Columbia Financial (CLBK) 10-K2 Mar 202019 FY Annual reportFinancial data

Company Profile

Cover Page

Cover Page - USD ($) $ in Millions	12 Months Ended
Cover Page - USD ($) $ in Millions	Dec. 31, 2019	Feb. 26, 2020	Jun. 28, 2019
Cover page.
Document Type	10-K
Document Annual Report	true
Document Period End Date	Dec. 31, 2019
Document Transition Report	false
Entity File Number	001-38456
Entity Registrant Name	COLUMBIA FINANCIAL, INC.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	22-3504946
Entity Address, Address Line One	19-01 Route 208 North,
Entity Address, City or Town	Fair Lawn,
Entity Address, State or Province	NJ
Entity Address, Postal Zip Code	07410
City Area Code	800
Local Phone Number	522-4167
Title of 12(b) Security	Common stock, par value $0.01 per share
Trading Symbol	CLBK
Security Exchange Name	NASDAQ
Entity Well-known Seasoned Filer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Public Float			$ 721.1
Entity Common Stock, Shares Outstanding (in shares)		112,361,961
Documents Incorporated by Reference	Portions of the Registrant’s Proxy Statement for the 2020 Annual Meeting of Stockholders are incorporated by reference into Part III of this Form 10-K.
Entity Central Index Key	0001723596
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2019
Document Fiscal Period	FY
Amendment Flag	false

Consolidated Statements of Fina

Consolidated Statements of Financial Condition - USD ($)	Dec. 31, 2019	Dec. 31, 2018
Assets
Cash and due from banks	$ 75,420,000	$ 42,065,000
Short-term investments	127,000	136,000
Total cash and cash equivalents	75,547,000	42,201,000
Debt securities available for sale, at fair value	1,098,336,000	1,032,868,000
Debt securities held to maturity, at amortized cost (fair value of $289,505 and $254,841 at December 31, 2019 and 2018, respectively)	285,756,000	262,143,000
Equity securities, at fair value	2,855,000	1,890,000
Federal Home Loan Bank stock	69,579,000	58,938,000
Loans held-for-sale, at fair value	0	8,081,000
Loans receivable	6,197,566,000	4,979,182,000
Less: allowance for loan losses	61,709,000	62,342,000
Loans receivable, net	6,135,857,000	4,916,840,000
Accrued interest receivable	22,092,000	18,894,000
Real estate owned	0	92,000
Office properties and equipment, net	72,967,000	52,050,000
Bank-owned life insurance	211,415,000	184,488,000
Goodwill and intangible assets	68,582,000	6,085,000
Other assets	145,708,000	107,048,000
Total assets	8,188,694,000	6,691,618,000
Liabilities:
Deposits	5,645,842,000	4,413,873,000
Borrowings	1,407,022,000	1,189,180,000
Advance payments by borrowers for taxes and insurance	35,507,000	32,030,000
Accrued expenses and other liabilities	117,806,000	84,475,000
Total liabilities	7,206,177,000	5,719,558,000
Stockholders' equity:
Preferred stock, $0.01 par value. 10,000,000 shares authorized; none issued and outstanding at December 31, 2019 and 2018	0	0
Common stock, $0.01 par value. 500,000,000 shares authorized; 117,278,745 shares issued and 113,765,387 shares outstanding at December 31, 2019, and 115,889,175 shares issued and outstanding at December 31, 2018	1,173,000	1,159,000
Additional paid-in capital	531,667,000	527,037,000
Retained earnings	615,481,000	560,216,000
Accumulated other comprehensive loss	(68,735,000)	(71,897,000)
Treasury stock, at cost; 3,513,358 shares at December 31, 2019 and -0- at December 31, 2018	(54,950,000)	0
Common stock held by the Employee Stock Ownership Plan	(41,564,000)	(43,835,000)
Stock held by Rabbi Trust	(1,520,000)	(1,259,000)
Deferred compensation obligations	965,000	639,000
Total stockholders' equity	982,517,000	972,060,000
Total liabilities and stockholders' equity	$ 8,188,694,000	$ 6,691,618,000

Consolidated Statements of Fi_2

Consolidated Statements of Financial Condition (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Statement of Financial Position [Abstract]
Debt securities held to maturity	$ 289,505	$ 254,841
Preferred stock, par value (in dollars per share)	$ 0.01	$ 0.01
Preferred stock, shares authorized (in shares)	10,000,000	10,000,000
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized (in shares)	500,000,000	500,000,000
Preferred stock, shares issued (in shares)	0	0
Preferred stock, shares outstanding (in shares)	0	0
Common stock, shares issued (in shares)	117,278,745	115,889,175
Common stock, shares outstanding (in shares)	113,765,387	115,889,175
Treasury stock, shares (in shares)	3,513,358	0

Consolidated Statements of Inco

Consolidated Statements of Income - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
Consolidated Statements of Income - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2019	Dec. 31, 2018	Sep. 30, 2017
Interest income:
Loans receivable	$ 43,043	$ 217,774	$ 189,869	$ 164,849
Debt securities available for sale and equity securities	5,074	30,938	25,338	17,163
Debt securities held to maturity	382	8,180	7,147	68
Federal funds and interest-earning deposits	103	594	1,175	308
Federal Home Loan Bank stock dividends	567	3,597	2,761	1,838
Total interest income	49,169	261,083	226,290	184,226
Interest expense:
Deposits	7,631	61,551	39,523	25,581
Borrowings	4,609	27,161	22,733	18,865
Total interest expense	12,240	88,712	62,256	44,446
Net interest income	36,929	172,371	164,034	139,780
Provision for loan losses	3,400	4,224	6,677	6,426
Net interest income after provision for loan losses	33,529	168,147	157,357	133,354
Non-interest income:
Bank-owned life insurance	1,089	5,846	5,208	4,936
Gain (loss) on securities transactions	(60)	2,612	116	(1,689)
Change in fair value of equity securities	0	305	0	0
Gain (loss) on sale of loans	0	785	618	(380)
Other non-interest income	1,162	5,922	4,943	4,497
Total non-interest income	4,733	31,636	21,688	17,172
Non-interest expense:
Compensation and employee benefits	15,624	84,256	77,226	62,993
Occupancy	3,382	16,180	14,547	13,315
Federal deposit insurance premiums	414	895	1,893	1,652
Advertising	1,408	3,932	4,137	4,078
Professional fees	398	5,913	4,619	1,354
Data processing	595	3,001	2,600	2,244
Charitable contribution to foundation	0	0	34,767	3,603
Merger-related expenses	0	2,755	0	0
Other non-interest expense	3,780	11,769	5,597	14,207
Total non-interest expense	25,601	128,701	145,386	103,446
Income before income tax expense	12,661	71,082	33,659	47,080
Income tax expense	8,983	16,365	10,923	16,008
Net income	3,678	$ 54,717	$ 22,736	31,072
Earnings per share - basic and diluted (in dollars per share)		$ 0.49	$ 0.20
Weighted average shares outstanding - basic and diluted (in shares)		111,101,246	111,395,723
Demand deposit account fees
Non-interest income:
Revenue	960	$ 4,478	$ 3,987	3,669
Title insurance fees
Non-interest income:
Revenue	1,017	4,981	4,297	4,163
Bank Servicing
Non-interest income:
Revenue	$ 565	$ 6,707	$ 2,519	$ 1,976

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income (Loss) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2019	Dec. 31, 2018	Sep. 30, 2017
Statement of Comprehensive Income [Abstract]
Net income	$ 3,678	$ 54,717	$ 22,736	$ 31,072
Other comprehensive income (loss), net of tax:
Unrealized gain (loss) on debt securities available for sale	(3,131)	21,067	(5,778)	(11,498)
Accretion of unrealized gain (loss) on debt securities reclassified as held to maturity	(58)	9	(13)	8
Reclassification adjustment for gain (loss) included in net income	47	2,011	(92)	1,689
Total other comprehensive (loss) income, net of tax	(3,142)	23,087	(5,883)	(9,801)
Derivatives, net of tax:
Unrealized (loss) gain on swap contracts accounted for as cash flow hedges		(6,468)
Unrealized (loss) gain on swap contracts accounted for as cash flow hedges	162		(2,230)	62
Total derivative, net of tax		(6,468)
Total derivative, net of tax	162		(2,230)	62
Employee benefit plans, net of tax:
Amortization of prior service cost included in net income	(43)	(44)	(491)	(73)
Reclassification adjustment of actuarial net (loss) gain included in net income	(103)	(2,930)	1,996	7,593
Change in funded status of retirement obligations	(5,670)	(9,935)	121	7,397
Tax effects resulting from the adoption of ASU No. 2018-02	(10,434)	0	0	0
Total employee benefit plans, net of tax	(16,250)	(12,909)	1,626	14,917
Total other comprehensive income (loss)	(19,230)	3,710	(6,487)	5,178
Total comprehensive income (loss), net of tax	$ (15,552)	$ 58,427	$ 16,249	$ 36,250

Consolidated Statements of Chan

Consolidated Statements of Changes in Stockholders' Equity - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-in-Capital	Retained Earnings	Accumulated Other Comprehensive (Loss)	Treasury Stock	Common Stock Held by the Employee Stock Ownership Plan	Stock Held by Rabbi Trust	Deferred Compensation Obligations	Columbia Bank, MHC	Columbia Bank, MHCCommon Stock	Columbia Bank Foundation	Columbia Bank FoundationCommon Stock	Columbia Bank FoundationAdditional Paid-in-Capital	IPO	IPOCommon Stock	IPOAdditional Paid-in-Capital
Balance at beginning of period at Sep. 30, 2016	$ 439,664	$ 0	$ 0	$ 491,022	$ (51,358)		$ 0	$ 0	$ 0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	31,072			31,072
Other comprehensive income	5,178				5,178				0
Balance at end of year at Sep. 30, 2017	475,914	0	0	522,094	(46,180)		0	0	0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	3,678			3,678
Other comprehensive income	(19,230)								0
Other comprehensive income (loss)	(7,522)				(7,522)
Balance at end of year at Dec. 31, 2017	472,070	0	0	537,480	(65,410)		0	0	0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	22,736			22,736
Other comprehensive income	(6,487)				(6,487)
Issuance of common stock										$ 626	$ 626	$ 34,767	$ 35	$ 34,732	$ 491,802	$ 498	$ 491,304
Purchase of Employee Stock Ownership Plan shares	(45,428)						(45,428)
Employee Stock Ownership Plan shares committed to be released	2,594		1,001				1,593
Funding of deferred compensation obligations	(620)							(1,259)	639
Balance at end of year at Dec. 31, 2018	972,060	1,159	527,037	560,216	(71,897)	$ 0	(43,835)	(1,259)	639
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	54,717			54,717
Other comprehensive income	3,710				3,710
Issuance of common stock allocated to restricted stock award grants	14	14	0
Treasury stock allocated to restricted stock award grants	0		(1,095)			1,095
Stock based compensation	3,694		3,694
Purchase of treasury stock (3,543,800 shares)	(55,309)					(55,309)
Restricted stock forfeitures	0		736			(736)
Employee Stock Ownership Plan shares committed to be released	3,566		1,295				2,271
Funding of deferred compensation obligations	65							(261)	326
Balance at end of year at Dec. 31, 2019	$ 982,517	$ 1,173	$ 531,667	$ 615,481	$ (68,735)	$ (54,950)	$ (41,564)	$ (1,520)	$ 965

Consolidated Statements of Ch_2

Consolidated Statements of Changes in Stockholders' Equity (Parenthetical)	12 Months Ended
	Dec. 31, 2019shares
Statement of Stockholders' Equity [Abstract]
Treasury stock, shares purchased (in shares)	3,543,800

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($)	3 Months Ended	12 Months Ended
Consolidated Statements of Cash Flows - USD ($)	Dec. 31, 2017	Dec. 31, 2019	Dec. 31, 2018	Sep. 30, 2017
Cash flows from operating activities:
Net income	$ 3,678,000	$ 54,717,000	$ 22,736,000	$ 31,072,000
Adjustments to reconcile net income to net cash provided by operating activities:
Amortization of deferred loan fees and costs, premiums and discounts	439,000	1,205,000	1,965,000	1,006,000
Net amortization of premiums and discounts on securities	328,000	1,160,000	1,212,000	1,460,000
Net amortization of mortgage servicing rights	22,000	(109,000)	(88,000)	105,000
Amortization of debt issuance costs	14,000	0	890,000	53,000
Amortization of intangible assets	0	222,000	0	0
Depreciation and amortization of office properties and equipment	863,000	4,880,000	3,839,000	3,364,000
Provision for loan losses	3,400,000	4,224,000	6,677,000	6,426,000
(Gain) loss on securities transactions	60,000	(2,612,000)	(116,000)	1,689,000
Change in fair value of equity securities	0	(305,000)	0	0
Proceeds from sales of loans held-for-sale	0	101,946,000	3,615,000	40,564,000
Origination of loans held-for-sale	0	0	0	(40,280,000)
(Gain) loss on sale of loans	0	(785,000)	(618,000)	380,000
Loss (gain) on real estate owned	0	1,000	56,000	(233,000)
Loss on write-down of real estate owned	0	0	55,000	0
Loss (gain) on disposal of office properties and equipment	0	3,000	(5,000)	169,000
Deferred tax expense (benefit)	7,491,000	7,527,000	(5,490,000)	(1,426,000)
Increase in accrued interest receivable	(1,228,000)	(959,000)	(2,979,000)	(1,531,000)
Increase in other assets	(15,557,000)	(51,856,000)	(11,053,000)	(11,681,000)
Increase in accrued expenses and other liabilities	3,905,000	3,032,000	7,980,000	9,840,000
Income on bank-owned life insurance	(1,089,000)	(5,846,000)	(5,208,000)	(4,936,000)
Contribution of common stock to Columbia Bank Foundation	0	0	34,767,000	0
Employee stock ownership plan expense	0	3,566,000	2,594,000	0
Stock based compensation	0	3,694,000	0	0
Increase in deferred compensation obligations under Rabbi Trust	0	65,000	(620,000)	0
Net cash provided by operating activities	2,326,000	123,770,000	60,209,000	36,041,000
Cash flows from investing activities:
Proceeds from sales of debt securities available for sale	0	65,198,000	11,513,000	187,376,000
Proceeds from sale of equity securities	92,000	1,065,000	0	0
Proceeds from paydowns / maturities / calls of debt securities available for sale	7,009,000	149,683,000	69,977,000	68,409,000
Proceeds from paydowns / maturities / calls of debt securities held to maturity	1,845,000	46,133,000	8,820,000	769,000
Purchases of debt securities available for sale	(163,721,000)	(176,171,000)	(413,804,000)	(162,788,000)
Purchases of debt securities held to maturity	(108,640,000)	(70,126,000)	(31,639,000)	(30,484,000)
Purchase of equity securities	0	(416,000)	0	0
Proceeds from sales of loans receivable	0	11,671,000	32,039,000	62,407,000
Purchase of loans receivable	(56,095,000)	(89,774,000)	(32,251,000)	(20,473,000)
Net increase in loans receivable	(41,157,000)	(503,772,000)	(536,129,000)	(425,926,000)
Purchase of bank-owned life insurance	0	0	(30,000,000)	(4,500,000)
Proceeds from bank-owned life insurance death benefit	0	1,015,000	1,241,000	1,631,000
Proceeds from redemptions of Federal Home Loan Bank stock	6,476,000	72,871,000	67,035,000	33,193,000
Purchases of Federal Home Loan Bank stock	(15,296,000)	(79,796,000)	(81,309,000)	(35,035,000)
Proceeds from sales of office properties and equipment	0	0	8,000	17,000
Additions to office properties and equipment	(2,648,000)	(19,344,000)	(13,272,000)	(6,527,000)
Proceeds from sales of real estate owned	0	91,000	1,007,000	1,614,000
Net cash acquired in acquisition	0	(31,288,000)	0
Net cash used in investing activities	(372,135,000)	(622,960,000)	(946,764,000)	(330,317,000)
Cash flows from financing activities:
Net increase in deposits	139,887,000	449,270,000	150,558,000	300,613,000
Proceeds from long-term borrowings	0	140,000,000	220,980,000	168,400,000
Payments on long-term borrowings	(90,000,000)	(230,000,000)	(210,000,000)	(90,000,000)
Net increase (decrease) in short-term borrowings	286,000,000	225,081,000	299,800,000	(27,400,000)
Payments on trust preferred securities	0	0	(51,547,000)	0
Increase (decrease) in advance payments by borrowers for taxes and insurance	(1,555,000)	3,121,000	6,467,000	(2,056,000)
Issuance of common stock	0	14,000	492,428,000	0
Purchase of treasury stock	0	(55,309,000)	0	0
Purchase of employee stock ownership plan shares	0	0	(45,428,000)	0
Restricted stock forfeitures	0	(736,000)	0
Issuance of treasury stock allocated to restricted stock award grants	0	1,095,000	0
Net cash provided by financing activities	334,332,000	532,536,000	863,258,000	349,557,000
Net increase (decrease) in cash and cash equivalents	(35,477,000)	33,346,000	(23,297,000)	55,281,000
Cash and cash equivalents at beginning of period	100,975,000	42,201,000	65,498,000	45,694,000
Cash and cash equivalents at end of period	65,498,000	75,547,000	42,201,000	100,975,000
Cash paid during the period for:
Interest on deposits and borrowings	11,484,000	87,370,000	61,987,000	44,397,000
Income tax payments, net of (refunds)	1,393,000	(2,893,000)	21,325,000	27,784,000
Non-cash investing and financing activities
Transfer of loans receivable to real estate owned	566,000	0	251,000	515,000
Transfer of loans receivable to loans held-for-sale	0	93,147,000	11,696,000	0
Transfer of securities from available for sale to held to maturity	0	0	0	103,680,000
Securitization of loans	0	21,615,000	0	0
Non-cash assets acquired:
Debt securities available for sale	0	51,710,000	0	0
Equity securities	0	1,073,000	0	0
Federal Home Loan Bank stock	0	3,716,000	0	0
Loans receivable	0	757,223,000	0	0
Accrued interest receivable	0	2,239,000	0	0
Office properties and equipment, net	0	6,815,000	0	0
Bank-owned life insurance	0	22,096,000	0	0
Deferred tax assets, net	0	3,534,000	0	0
Core deposit and other intangibles	0	7,467,000	0	0
Other assets	0	767,000	0	0
Total non-cash assets acquired	0	856,640,000	0	0
Liabilities assumed:
Deposits	0	782,698,000	0	0
Borrowings	0	82,761,000	0	0
Advance payments by borrowers for taxes and insurance	0	356,000	0	0
Accrued expenses and other liabilities	0	14,584,000	0	0
Total liabilities assumed	0	880,399,000	0	0
Net non-cash liabilities acquired	0	(23,759,000)	0	0
Net cash and cash equivalents acquired in acquisition	$ 0	$ 105,006,000	$ 0	$ 0

Business

Business	12 Months Ended
Business	Dec. 31, 2019
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Business	Business On April 19, 2018, Columbia Financial, Inc. completed its minority stock offering, after receiving all regulatory approvals. In connection with the closing, 62,580,155 shares of its common stock were issued to Columbia Bank, MHC (the "MHC"), the mutual holding company of Columbia Financial, Inc., 3,476,675 shares were issued to the Columbia Bank Foundation, Columbia Bank's charitable foundation, and 49,832,345 shares were issued to depositors who subscribed for and were allocated shares in the minority stock offering, as well as the Columbia Bank Employee Stock Ownership Plan (the "ESOP"). The accounts of the MHC are not consolidated in the consolidated financial statements of the Company. On May 22, 2018, the Board of Directors of the Company adopted a resolution to change the Company’s fiscal year end from September 30 to December 31, effective immediately as of the date of the Board resolution. In addition, on May 22, 2018, the Boards of Directors of Columbia Bank, MHC and Columbia Bank (the "Bank") also adopted resolutions to change the MHC’s and the Bank’s fiscal year ends from September 30 to December 31, effective immediately as of the date of the Board resolutions. On November 1, 2019, the Company completed its acquisition of Stewardship Financial Corporation (“Stewardship”), pursuant to the Agreement and Plan of Merger, dated as of June 6, 2019. Immediately following the consummation of the Merger, Atlantic Stewardship Bank, a wholly owned subsidiary of Stewardship, merged with and into Columbia Bank, a wholly owned subsidiary of the Company, with Columbia Bank as the surviving bank. On December 2, 2019, the Company, the Bank and the MHC entered into an Agreement and Plan of Merger (the “Merger Agreement”) with RSB Bancorp, MHC, RSB Bancorp, Inc. and Roselle Bank (collectively, the “Roselle Entities”), pursuant to which (i) RSB Bancorp, MHC will merge with and into the MHC, with the MHC as the surviving entity, (ii) RSB Bancorp, Inc. will merge with and into the Company, with the Company as the surviving entity; and (iii) Roselle Bank will merge with and into the Bank, with the Bank as the surviving institution (collectively, the “Merger”). Under the terms of the Merger Agreement, depositors of Roselle Bank will become depositors of the Bank and will have the same rights and privileges in the MHC as if their accounts had been established at the Bank on the date established at Roselle Bank. As part of the transactions contemplated by the Merger Agreement, at the effective time of the Merger, the Company will issue additional shares of its common stock to the MHC in an amount equal to the fair value of the Roselle Entities as determined by an independent appraiser. The Merger Agreement has been unanimously approved by the Boards of Directors of each of the Company, the MHC and the Bank and the Boards of Directors of each of the Roselle Entities. Subject to the receipt of all required regulatory and other approvals, and the satisfaction or waiver of other customary closing conditions, the parties anticipate that the transactions contemplated by the Merger Agreement will close in the second quarter of 2020.

Summary of Significant Accounti

Summary of Significant Accounting Policies	12 Months Ended
Summary of Significant Accounting Policies	Dec. 31, 2019
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Summary of Significant Accounting Policies	Summary of Significant Accounting Policies Principles of Consolidation The accompanying consolidated financial statements include the accounts of Columbia Financial, Inc., its wholly-owned subsidiary, Columbia Bank (the "Bank") and the Bank's wholly-owned subsidiaries, Columbia Investment Services, Inc., 2500 Broadway Corp. 1901 Residential Management Co. LLC, Plaza Financial Services, Inc., First Jersey Title Services, Inc., Real Estate Management Corp. LLC, 1901 Commercial Management Co. LLC, Stewardship Realty LLC, and CSB Realty Corp. (collectively, the “Company”). In consolidation, all intercompany accounts and transactions are eliminated. Certain reclassifications have been made in the consolidated financial statements to conform with current year classifications. The Company also owns 100% of the common stock of Columbia Financial Capital Trust I (the "Trust"). The Trust was used to issue trust preferred securities. In accordance with Accounting Standards Codification ("ASC") Topic 810, Consolidation , the Trust was classified as a variable interest entity and did not satisfy the conditions for consolidation. Accordingly, the Trust was treated as an unconsolidated subsidiary. In August 2018, the Company redeemed, in full $51.5 million of junior subordinated debt securities, which represented 100% of the assets of the Trust. The Bank's wholly owned subsidiary, Stewardship Realty, LLC, incorporated as a New Jersey corporation in 2005 was acquired in the Company's merger with Stewardship in November 2019. It is a service corporation originally organized to hold and manage property in Midland Park which was occupied by Atlantic Stewardship Bank. The Company also owns 100% of the common stock of Stewardship Statutory Trust I, which is a trust incorporated in Delaware which was also acquired in the Company's merger with Stewardship in November 2019. In accordance with ASC Topic 810, Consolidation , (2) Summary of Significant Accounting Policies (continued) this Trust was classified as a variable interest entity and did not satisfy the conditions for consolidation. Accordingly, this Trust, which owns $7.0 million of trust preferred securities, which represented 100% of the assets, was treated as an unconsolidated subsidiary. Basis of Financial Statement Presentation The consolidated financial statements of the Company have been prepared in conformity with U.S. generally accepted accounting principles (“GAAP”). In preparing the consolidated financial statements, management is required to make estimates and assumptions about future events. These estimates and the underlying assumptions affect the reported amounts of assets and liabilities and disclosures about contingent assets and liabilities as of the dates of the consolidated statements of financial condition, and revenues and expenses for the periods then ended. Such estimates are used in connection with the determination of the adequacy of the allowance for loan losses, evaluation of goodwill for impairment, evaluation of other-than-temporary impairment on securities, evaluation of the need for valuation allowances on deferred tax assets, and determination of liabilities related to retirement and other post-retirement benefits, among others. These estimates and assumptions are based on management’s best estimates and judgment. Management evaluates its estimates and assumptions on an ongoing basis using historical experience and other factors, including the current economic environment, which management believes to be reasonable under the circumstances. Such estimates and assumptions are adjusted when facts and circumstances dictate. Illiquid credit markets, volatile securities markets, and declines in the housing market and the economy generally have combined to increase the uncertainty inherent in such estimates and assumptions. As future events and their effects cannot be determined with precision, actual results could differ significantly from these estimates. Changes in estimates resulting from continuing changes in the economic environment will be reflected in the consolidated financial statements in future periods. Cash and Cash Equivalents For purposes of reporting cash flows, cash and cash equivalents include cash on hand, amounts due from banks and interest-bearing deposits at other financial institutions and short-term investments. The Company is required by the Federal Reserve Bank System to maintain cash reserves equal to a percentage of certain deposits. At December 31, 2019 and 2018 , the reserve requirement totaled $8.8 million and $5.9 million , respectively. Securities Securities are classified as available for sale and held to maturity. Management determines the appropriate classification of securities at the time of purchase. If the Company has the intent to hold securities until maturity, these securities are classified as held to maturity and reported at amortized cost. If the Company does not have the intent to hold securities until maturity, these securities are classified as available for sale. The available for sale securities portfolio is carried at estimated fair value, with any unrealized holding gains or losses, net of taxes, reported as a separate component of accumulated other comprehensive income or loss in Stockholders' Equity. The fair values of these securities are based on market quotations or matrix pricing as discussed in Note 16. Management conducts a periodic review and evaluation of the securities portfolio to determine if any declines in the fair value of securities are other-than-temporary. In this evaluation, if such decline were deemed other-than temporary, management would measure the total credit-related component of the unrealized loss, and recognize that portion of the loss as a charge to current period earnings. The remaining portion of the unrealized loss would be recognized as an adjustment to accumulated other comprehensive income. The fair value of the securities portfolio is significantly affected by changes in interest rates. In general, as interest rates rise, the fair value of fixed-rate securities decreases and as interest rates fall, the fair value of fixed-rate securities increases. The Company determines if it has the intent to sell these securities or if it more likely than not that the Company would be required to sell the securities before the anticipated recovery. If either exists, the decline in value is considered other-than-temporary and would be recognized as an expense in the current period. Premiums and discounts on securities are generally amortized and accreted to income over the contractual lives of the securities using the level-yield method. Premiums on callable securities are amortized to the first call date. Dividend and interest income are recognized when earned. Realized gains and losses are recognized when securities are sold or called based on the specific identification method. In the ordinary course of business, securities are pledged as collateral in conjunction with the Company’s borrowings, lines of credit, and public funds on deposit. (2) Summary of Significant Accounting Policies (continued) Federal Home Loan Bank Stock The Bank, as a member of the Federal Home Loan Bank of New York (the "FHLB"), is required to hold shares of capital stock of the FHLB based on its activities, primarily its outstanding borrowings. The Bank carries the investment at cost, or par value, which approximates fair value. Loans Held-for-Sale Loans held-for-sale consist of conforming loans originated and intended for sale in the secondary market. These loans are carried at the lower of cost or estimated fair value, less costs to sell, as determined on an individual loan basis. Net unrealized losses, if any, are recognized in a valuation allowance through charges to earnings. Origination fees and costs on loans held-for-sale are deferred and recognized as a component of the gain or loss on sale. Loans held-for-sale are generally sold with loan servicing rights retained by the Bank. Loans Receivable Loans receivable are carried at unpaid principal balances adjusted by unamortized premiums and unearned discounts, net deferred origination fees and costs less the allowance for loan losses. The Bank defers loan origination fees and certain direct loan origination costs and accretes such amounts as an adjustment to the yield over the expected lives of the related loans using the level-yield method. Interest income on loans is accrued and credited to income as earned. Premiums and discounts on loans purchased are amortized or accreted as an adjustment to yield over the contractual lives of the related loans using methodologies which approximate the level-yield method. A loan is considered delinquent when payment has not been received within 30 days of its contractual due date. Generally, the accrual of income on loans is discontinued when they are past due 90 days or more as to contractual obligations, or other circumstances indicate that collection is questionable. When a loan is placed on non-accrual status, any interest accrued but not received is reversed against interest income. Payments received on a non-accrual loan are either applied to the outstanding principal balance or recorded as interest income, depending on an assessment of the ability to collect the loan. Non-accruing loans are returned to accrual status after there has been a sustained period of repayment performance (generally six consecutive months of payment) and both principal and interest are deemed collectible. Loans are generally charged off after an analysis is completed which indicates that collectability of the full principal balance is in doubt. An impaired loan is defined as a loan for which it is probable, based on current information, that the Bank will not collect all amounts due under the contractual terms of the loan agreement. The Bank considers the population of loans in its impairment analysis to include all multifamily and commercial real estate, construction, and commercial business loans with an outstanding balance greater than $500,000 and not accruing, and loans modified in a troubled debt restructuring. The Company also considers residential real estate, and home equity loans and advances that are not accruing or modified in a troubled debt restructuring for impairment. Other loans may be included in the population of loans in its impairment analysis if management has specific information of a collateral shortfall. Loan impairment is measured based on the present value of expected future cash flows discounted at the loan's effective interest rate or, as a practical expedient, at the loan's observable market price or the fair value of the collateral if the loan is collateral dependent. Payments received on impaired loans are recognized on a cash basis. Purchased Credit-Impaired ("PCI") Loans Purchased credit impaired loans are loans acquired through acquisitions at a discount primarily due to deteriorated credit quality. PCI loans are recorded at fair value at the date of acquisition with no carryover of the related allowance for credit losses. Determining the fair value of loans involves estimating the amount and timing of principal and interest cash flows expected to be collected on the loans discounting those cash flows at a market rate of interest. The excess of cash flows expected at acquisition over the estimated fair value is referred to as the accretable yield and is recognized into interest income over the remaining life of the loan. The difference between contractually required payments at acquisition and the cash flows expected to be collected at acquisition is referred to as the nonaccretable yield. The nonaccretable yield represents estimated future credit losses expected to be incurred over the life of the loan. Subsequent decreases to the expected cash flows require us to evaluate the need for an allowance for credit losses. Subsequent improvements in expected cash flows result in the reversal of a corresponding amount of the nonacretable yield which we then reclassify as accretable yield that is recognized into interest income over the remaining life of the loan using the interest method. The evaluation of the amount of future cash flows that is expected to be collected is performed in a similar manner used to determine the allowance for (2) Summary of Significant Accounting Policies (continued) loan losses. Any charge-offs of principal on acquired loans would first be applied against the nonaccretable yield portion of the fair value adjustment. Allowance for Loan Losses Losses on loans are charged to the allowance for loan losses. Additions to this allowance are made by recoveries of loans previously charged off and by a provision charged to expense. The determination of the balance of the allowance for loan losses is based on an analysis of the loan portfolio, economic conditions, historical loan loss experience and other factors that warrant recognition in providing an adequate allowance. Estimates and judgments required to establish the allowance include: overall economic environment; value of collateral; strength of guarantors; loss exposure in the event of default; the amount and timing of future cash flows on impaired loans; and determination of loss factors applied to the portfolio segments. These estimates are susceptible to significant change. Management regularly reviews loss experience within the portfolio and monitors current economic conditions and other factors related to the collectability of the loan portfolio. While management uses available information, future additions to the allowance may be necessary based on changes in economic conditions in the Bank's market area. In addition, regulatory agencies, as an integral part of their examination process, periodically review the adequacy of the Bank's allowance for loan losses as an integral part of their examination. Such agencies may require the Bank to recognize additions to the allowance or additional write-downs based on their judgments about information available to them at the time of their examination. Although management uses the best information available, the level of the allowance for loan losses remains an estimate that is subject to significant uncertainties. Troubled Debt Restructuring Troubled debt restructured loans are those loans where the Company has granted a concession it would not otherwise consider because of economic or legal reasons pertaining to a debtor’s financial difficulties. A concession could include a reduced interest rate below a market rate, an extension of the term of the loan, or a combination of the two methods, but generally does not result in the forgiveness of principal or accrued interest. Not all concessions granted by the Company constitute a troubled debt restructuring. Once an obligation has been restructured and designated as a troubled debt restructuring, it continues to be designed as a restructured loan until paid in full. The Company records an impairment charge equal to the difference between the present value of expected future cash flows under the restructured terms discounted at the loan’s original effective interest rate, and the loan’s carrying value. Changes in the calculated impairment due to the passage of time are recorded as an adjustment to the allowance for loan losses. Restructured loans that were accruing prior to the restructuring, where income was reasonably assured subsequent to the restructuring, maintain their accrual status. Restructured loans for which collectability was not reasonably assured are placed on non-accrual status, interest accruals cease, and uncollected accrued interest is reversed and charged against current income. Non-accruing restructured loans may be returned to accrual status when there is a sustained period of repayment performance (generally six consecutive months of payments), and both principal and interest are deemed collectible. Loans Sold and Serviced The Company has entered into Guarantor Swaps with Freddie Mac to improve its liquidity. In these types of transactions, the Company sells mortgage loans in exchange for Freddie Mac Mortgage Participation Certificates backed exclusively by the loans sold. The Company retains the servicing of these loans. The Company also periodically sells loans to investors and continues to service such loans for a fee. Gains or losses on the sale of loans are recorded on trade date using the specific-identification method. Real Estate Owned Real estate acquired through foreclosure or deed in lieu of foreclosure is carried at the lower of the recorded investment in the loan at the time of foreclosure or fair value, less estimated costs to sell. Fair value is generally based on recent appraisals. The excess, if any, of the loan amount over the fair value of the asset acquired is charged off against the allowance for loan losses at the date the property is acquired. Subsequent write-downs in the value of real estate owned, as well as holding costs, and any gains or losses realized upon sale of the property are recorded as incurred. Office Properties and Equipment Land is carried at cost. Office properties, land and building improvements, furniture and equipment, and leasehold improvements are carried at cost, less accumulated depreciation and amortization. Depreciation and amortization of office properties and equipment is computed on a straight-line basis over their estimated useful lives (generally 40 years for buildings, 10 to 20 years for land and building (2) Summary of Significant Accounting Policies (continued) improvements, 3 to 10 years for furniture and equipment). Leasehold improvements, carried at cost, net of accumulated depreciation, are amortized over the terms of the related leases or the estimated useful lives of the assets, whichever is shorter. Major improvements are capitalized, while repairs and maintenance costs are charged to expense as incurred. Upon retirement or sale, any gain or loss is recognized as incurred. At December 31, 2019, land and buildings include property acquired from Stewardship with a fair value of $1.8 million which is held for sale. Bank-owned Life Insurance ("BOLI") Bank-owned life insurance is accounted for using the cash surrender value method and is recorded at its net realizable value. The change in the net asset value is recorded as a component of non-interest income. A deferred liability has been recorded for the estimated cost of post-retirement life insurance benefits accruing to applicable employees and directors covered by an endorsement split-dollar life insurance arrangement. Goodwill and Intangible Assets Intangible assets of the Bank consist of goodwill, core deposit intangibles and mortgage servicing rights. Goodwill represents the excess of the purchase price over the fair value of net assets acquired in purchase acquisitions. In accordance with GAAP, goodwill with an indefinite useful life is not amortized, but is evaluated for impairment on an annual basis, or more frequently if events or changes in circumstances indicate potential impairment between annual measurement dates. As permitted by GAAP, the Company prepares a qualitative assessment in determining whether goodwill may be impaired. The factors considered in the assessment include macroeconomic conditions, industry and market conditions and overall financial performance of the Company, among others. The Company completed its annual goodwill impairment test as of December 31, 2019 based upon its qualitative assessment of goodwill and concluded that goodwill was not impaired and no further quantitative analysis was warranted. Core deposit intangibles represent the balance of the core deposit intangibles ascribed to the value of deposit acquired by the Bank through the acquisition of Stewardship. Mortgage servicing rights are recorded when purchased or when originated mortgage loans are sold, with servicing rights retained. Mortgage servicing rights are amortized on an accelerated method based upon the estimated lives of the related loans, and generally adjusted for prepayments. Mortgage servicing rights are carried at the lower of amortized cost or fair value. Post-retirement Benefits The Company provides certain health care and life insurance benefits to eligible retired employees under a Post-retirement Plan, along with a split-dollar BOLI death benefit. The Company accrues the cost of retiree health care and other benefits during the employees’ period of active service. Effective January 1, 2019, the Post-retirement plan has been closed to new hires. Effective January 1, 2019, the Company implemented ASU 2017-07, Compensation - Retirement Benefits (Topic 715): Improving the Presentation of Net Periodic Pension Cost and Net Periodic Post-retirement Benefit Cost. Under this ASU, the FASB requires employers to report the service cost component in the same line item as other compensation costs arising from services rendered by the pertinent employees during the period. The other components of net periodic benefit cost are required to be presented in the Consolidated Statements of Income separately from the service cost component. This ASU is also required to be applied retrospectively to all periods presented. Employee Benefit Plans The Company maintains a single-employer tax-qualified defined benefit pension plan (the "Pension Plan") which covers full-time employees that satisfy the Pension Plan eligibility requirements. Effective October 1, 2018, employees hired by the Bank are not eligible to participate in the Company's Pension Plan as the plan has been closed to new employees as of that date. The Company's policy is to fund at least the minimum contribution required by the Employee Retirement Income Security Act of 1974. GAAP requires an employer to: (a) recognize in its statement of financial position the over-funded or under-funded status of a defined benefit post-retirement plan measured as the difference between the fair value of plan assets and the benefit obligation; (b) measure a plan’s assets and its obligations that determine its funded status at the end of the employer’s fiscal year (with limited exceptions); and (2) Summary of Significant Accounting Policies (continued) (c) recognize as a component of other comprehensive income (loss), net of tax, the actuarial gains and losses and the prior service costs and credits that arise during the period. The assets of the plan are primarily invested in fixed income and equity funds. The Company has a retirement income maintenance plan (the "RIM Plan") which is a non-qualified defined benefit plan which provides benefits to all employees of the Company if their benefits under the Pension Plan are limited by the Internal Revenue Code. The Company has a 401(k) plan covering substantially all employees of the Company. The Company may match a percentage of the first 3.00% to 4.50% contributed by participants. The Company's matching contribution, if any, is determined by the Board of Directors in its sole discretion. The Company has an Employee Stock Ownership Plan ("ESOP"). The funds borrowed by the ESOP from the Company to purchase the Company's common stock are being repaid from the Bank's contributions over a period of 20 years . The Company's common stock not allocated to participants is recorded as a reduction of stockholders' equity at cost. Compensation expense for the ESOP is based on the average price of the Company's stock and the amount of shares committed to be allocated during each period. The Company has a Supplemental Executive Retirement Plan ("SERP"). The SERP is a non-qualified plan which provides supplemental retirement benefits to eligible officers (those designated by the Board of Directors) of the Company who are prevented from receiving the full benefits contemplated by the ESOP's benefit formulas under tax law limits for tax-qualified plans. In addition, the Company maintains a stock based deferral plan (the "Stock Based Deferral Plan") for certain executives and directors. The Company records a deferred compensation equity account and corresponding contra-equity account for the cost of the shares held by the Stock Based Deferral and SERP Plans. The Company also maintains a non-qualified savings income maintenance deferred compensation plan (the "SIM Plan") that provides supplemental benefits to certain executives who are prevented from receiving the full benefits contemplated by the 401(k) Plan under tax law limits for tax-qualified plans, and a Deferred Compensation Plan for directors. Derivatives The Company uses derivative financial instruments as components of its market risk management, principally to manage interest rate risk. Certain derivatives are entered into in connection with transactions with commercial customers. Derivatives are not used for speculative purposes. All derivatives are recognized as either assets or liabilities in the Consolidated Statements of Financial Condition, reported at fair value and presented on a gross basis. Until a derivative is settled, a favorable change in fair value results in an unrealized gain that is recognized as an asset, while an unfavorable change in fair value results in an unrealized loss that is recognized as a liability. The Company applies hedge accounting to its derivatives used for market risk management purposes if specific criteria are met, including a requirement that a highly effective relationship exists between the derivative instrument and the hedged item, both at inception of the hedge and on an ongoing basis. Changes in the fair value of effective fair value hedges are recognized in current earnings (with the change in fair value of the hedged asset or liability also recognized in earnings). Changes in the fair value of effective cash flow hedges are recognized in other comprehensive income (loss) until earnings are affected by the variability in cash flows of the designated hedged item. Ineffective portions of hedge results are recognized in current earnings. Changes in the fair value of derivatives for which hedge accounting is not applied are recognized in current earnings. The Company formally documents at inception all relationships between the derivative instruments and the hedged items, as well as its risk management objectives and strategies for undertaking the hedge transactions. This process includes linking all derivatives that are designated as hedges to specific assets and liabilities, or to specific firm commitments. The Company also formally assesses, both at inception of the hedge and on an ongoing basis, whether the derivatives that are used in hedging transactions are highly effective in offsetting changes in the fair values or cash flows of the hedged items. If it is determined that a derivative is not highly effective or has ceased to be a highly effective hedge, the Company would discontinue hedge accounting prospectively. Gains or losses resulting from the termination of a derivative accounted for as a cash flow hedge remain in other comprehensive income (loss) and is (accreted) amortized to earnings over the remaining period of the former hedging relationship. Certain derivative financial instruments are offered to certain commercial banking customers to manage their risk exposures and risk management strategies. These derivative instruments consist primarily of currency forward contracts and interest rate swap contracts. The risk associated with these transactions is mitigated by simultaneously entering into similar transactions having essentially offsetting terms with a third party. (2) Summary of Significant Accounting Policies (continued) Income Taxes The Company and its subsidiaries file consolidated federal income tax returns. Federal income taxes are allocated to each entity based on their respective contributions to taxable income of the consolidated income tax returns. Beginning in 2019 as required by the State of New Jersey, the Company adopted combined income tax reporting for certain members of a commonly-controlled unitary business group. Prior to 2019, separate state income tax returns were filed for the Company and each of its qualifying subsidiaries. For the three months ended December 31, 2017, income tax expense included the impact of the enactment of the Tax Cuts and Jobs Act which reduced the maximum statutory federal income tax rate from 35% to 21%. This resulted in a charge to reduce the carrying value of the Company's net deferred income tax assets, which are included in the Consolidated Statements of Financial Condition. The Company records income taxes in accordance with ASC Topic 740, Income Taxes , using the asset and liability method. The amounts reflected on the Company's federal and state income tax returns differ from these provisions due principally to temporary differences in the reporting of certain items for consolidated financial statement reporting and income tax reporting purposes. Accordingly, deferred tax assets and liabilities: (i) are recognized for the expected future tax consequences of events that have been recognized in the financial statements or tax returns; (ii) are attributable to differences between the financial statement carrying amounts of existing assets and liabilities and their respective tax bases; and (iii) are measured using enacted tax rates expected to apply in the years when those temporary differences are expected to be recovered or settled. Where applicable, deferred tax assets are reduced by a valuation allowance for any portions determined not likely to be realized. The effect on deferred tax assets and liabilities of a change in tax rates is recognized in income tax expense in the period that includes the enactment date. The valuation allowance is adjusted, by a charge or credit to income tax expense, as changes in facts and circumstances warrant. Income taxes are allocated to the individual entities within the consolidated group based on the effective tax rate of the entity. The Company did not have any liabilities for uncertain tax positions or any known unrecognized tax benefits at December 31, 2019 and 2018 . The Company recognizes interest and penalties related to unrecognized tax benefits in income tax expense in the Consolidated Statements of Income. The Company did not recognize any interest and penalties during the years ended December 31, 2019 and 2018, September 31, 2017, and the three months ended December 31, 2017. On July 1, 2018, New Jersey enacted legislation which adds to the state’s 9.0% Corporation Business Tax rate (i) a 2.5% surtax for periods beginning in 2018 and 2019 and (ii) a 1.5% surtax for periods beginning in 2020 and 2021. These surtaxes apply to corporations with more than $1.0 million of net income allocated to New Jersey and expire beginning in 2022. Also, for periods beginning in 2017, New Jersey has reduced the dividends-received deduction from 100% to 95% for certain dividend income received by a corporation from a subsidiary that is at least 80% owned by the corporation. In addition, for periods beginning in 2019, as previously noted, New Jersey adopted combined income tax reporting for certain members of a commonly-controlled unitary business group, and issued guidance in December 2019 to clarify business entities to be included and excluded from this combined group. Comprehensive Income (Loss) Comprehensive income (loss) consists of net income and other comprehensive income (loss). Other comprehensive income (loss) includes items recorded in equity, such as unrealized holding gains and losses on debt securities available for sale, the noncredit component of other than temporary impairment losses on debt securities, unrealized gains and losses on derivatives, and the unfunded status and reclassification of actuarial net (loss) gain associated with the Company's benefit plans. Comprehensive income is presented in a separate Consolidated Statements of Comprehensive Income (Loss). Segment Reporting The Company’s operations are solely in the financial services industry and include providing traditional banking and other financial services to its customers. The Company operates primarily in New Jersey. Management makes operating decisions and assesses performance based on an ongoing review of the Company’s consolidated financial results. Therefore, the Company has a single operating segment for financial reporting purposes. Earnings Per Share ("EPS") Basic EPS is computed by dividing net income available to common shareholders by the weighted average number of common shares outstanding during the period. For purposes of calculating basic EPS

Acquisition of Stewardship Fina

Acquisition of Stewardship Financial Corporation	12 Months Ended
Acquisition of Stewardship Financial Corporation	Dec. 31, 2019
Business Combinations [Abstract]
Acquisition of Stewardship Financial Corporation	Acquisition of Stewardship Financial Corporation On November 1, 2019, the Company completed its acquisition of Stewardship Financial Corporation ("Stewardship"), pursuant to the Agreement and Plan of Merger, dated as of June 6, 2019, (the "Merger Agreement"). Under the terms of the merger agreement, each outstanding share of Stewardship common stock was converted into the right to received $15.75 in cash. At the time of closing, Stewardship had $956.0 million in total assets, including $756.9 million in net loans receivable, $52.6 million in securities, and $877.8 million in total liabilities, including $781.4 million in deposits and $81.8 million in borrowings. The deposits acquired from Stewardship were held across a network of 12 branches located in New Jersey throughout Bergen, Morris, and Passaic counties. Merger-related expenses are recorded in the Consolidated Statements of Income and are expensed as incurred. Direct acquisition and other charges incurred in connection with the Stewardship acquisition totaled $2.8 million for the year ended December 31, 2019 . The following table sets forth assets acquired and liabilities assumed in the Stewardship acquisition, at their estimated fair values as of the closing date of the transaction: November 1, 2019 Assets acquired: Cash and cash equivalents $ 105,006 Debt securities available for sale 51,710 Equity securities 1,073 Federal Home Loan Bank stock 3,716 Loans receivable 757,223 Accrued interest receivable 2,239 Office properties and equipment, net 6,815 Bank-owned life insurance 22,096 Deferred tax assets, net 3,534 Core deposit and other intangibles 7,467 Other assets 767 Total assets acquired 961,646 Liabilities assumed: Deposits $ 782,698 Borrowings 82,761 Advance payments by borrowers for taxes and insurance 356 Accrued expenses and other liabilities 14,584 Total liabilities assumed $ 880,399 Net assets acquired $ 81,247 Cash paid for purchase 136,294 Goodwill recorded at merger $ 55,047 The assets acquired and liabilities assumed have been accounted for under the acquisition method of accounting. The assets and liabilities were recorded at their fair values as of November 1, 2019, and resulted in the recognition of goodwill of $55.0 million and a core deposit intangible of $7.5 million . The determination of the fair value of assets acquired and liabilities assumed required management to make estimates about discount rates, future expected cash flows, market condition, and other future events that are highly subjective in nature and subject to change. The fair value estimates are subject to change for up to one year after the closing date of the transaction if additional information (existing at the date of closing) relative to closing date fair values becomes available. As the Company continues to analyze the acquired assets and assumed liabilities, there may be adjustments to the recorded carrying values. However, management does not expect significant future adjustments to the recorded amounts as at November 1, 2019. (3) Acquisition of Stewardship Financial Corporation (continued) Fair Value Measurement of Assets Acquired and Liabilities Assumed Described below are the methods used to determine the fair values of the significant assets acquired and liabilities assumed: Cash and cash equivalents. The estimated fair values of cash and cash equivalents approximate their stated face amounts, as these financial instruments are either due on demand or have short-term maturities. Debt securities available for sale. The estimated fair values of the debt securities were calculated utilizing Level 2 inputs. The majority of the acquired securities were fixed income instruments that are not quoted on an exchange, but are traded in active markets. The prices for these instruments are obtained through an independent pricing service when available, or dealer market participants with whom the Company has historically transacted with for both purchases and sales of securities. The prices are derived from market quotations and matrix pricing. The fair value measurements consider observable data that may include dealer quotes, market spreads, cash flows, the U.S. Treasury yield curve, and the bond's terms and conditions, among other things. Management reviewed the data and assumptions used in pricing securities by its third party provider to ensure the highest level of significant inputs are derived from market observable data. Loans. The acquired loan portfolio was segregated into pools for valuation purposes primarily based on loan type, non-accrual status, and credit risk rating. The estimated fair values were computed by discounting the expected cash flows from the respective pools. Cash flows were estimated by using valuation models that incorporated estimates of current key assumptions such as prepayment speeds, default rates, and loss severity rates. The process included: (1) Projecting monthly principal and/or interest cash flows based on the contractual terms of the loans, including both maturity and contractual amortization; (2) Adjusting projected cash flows for expected losses and prepayments, where appropriate; (3) Developing a discount rate based on the relative risk of the cash flows, considering the loan type, liquidity risk, the maturity of the loans, servicing costs, and a required return on capital; (4) Discounting the projected cash flows to a present value, to arrive at the calculated value of the loans. The methods used to estimate the fair values of loans are extremely sensitive to the assumptions and estimates used. While management attempted to use assumptions and estimates that best reflected the acquired loan portfolios and current market conditions, a greater degree of subjectivity is inherent in the values than in those determined in active markets. Office properties and equipment, net. The fair value of land and buildings was estimated using current appraisals. Acquired equipment was not material. Buildings are amortized over their estimated useful lives. Leasehold improvements and equipment are amortized or depreciated over their estimated useful lives usually ranging for three to ten years . Goodwill and intangible assets. Goodwill is not amortized for book purposes: however: it is reviewed at least annually for impairment and is not deductible for tax purposes. Intangible assets consisting of core deposit intangibles ("CDI") are the measures of the value of non-maturity deposits in a business combination. The fair value of the CDI was calculated utilizing the cost savings approach, the expected cost savings attributable to the core deposits funding relative to an alternative source of funding, using a discounted cash flow present value methodology. Key inputs and assumptions utilized in the discounted cash flow present value methodology include core deposit balances and rates paid, the cost of an additional funding source, the aggregate life of deposits and truncation points, non-interest deposit costs, and the immediate deposit outflow assumption. The CDI is amortized over an estimated useful life of ten years to approximate the existing deposit relationships acquired. Deposits. The fair values of deposit liabilities with no stated maturity (ie., non-interest bearing and interest-bearing demand deposit accounts, money market and savings and club accounts) are equal to the carrying amounts payable on demand. The fair value of certificates of deposit represent contractual cash flows, discounted to present value using interest rates currently offered on deposits with similar characteristics and remaining maturities. Borrowings. The fair values of borrowings consisting of FHLB advances were estimated by discounting future cash flows using market discount rates for borrowings with similar characteristics, terms and remaining maturities. The fair value of other borrowings, which included subordinated notes and debentures, were measured at the acquisition date using a dealer market quote.

Debt Securities Available for S

Debt Securities Available for Sale	12 Months Ended
Debt Securities Available for Sale	Dec. 31, 2019
Investments, Debt and Equity Securities [Abstract]
Debt Securities Available for Sale	Debt Securities Available for Sale Debt s ecurities available for sale at December 31, 2019 and 2018 are summarized as follows: December 31, 2019 Amortized Cost Gross Unrealized Gains Gross Unrealized (Losses) Fair Value (In thousands) U.S. government and agency obligations $ 42,081 $ 321 $ (16 ) $ 42,386 Mortgage-backed securities and collateralized mortgage obligations 968,165 12,981 (1,265 ) 979,881 Municipal obligations 2,284 1 (1 ) 2,284 Corporate debt securities 68,613 945 (378 ) 69,180 Trust preferred securities 5,000 — (395 ) 4,605 $ 1,086,143 $ 14,248 $ (2,055 ) $ 1,098,336 December 31, 2018 Amortized Cost Gross Unrealized Gains Gross Unrealized (Losses) Fair Value (In thousands) U.S. government and agency obligations $ 54,821 $ 53 $ (717 ) $ 54,157 Mortgage-backed securities and collateralized mortgage obligations 934,631 2,812 (17,436 ) 920,007 Municipal obligations 987 — — 987 Corporate debt securities 54,493 129 (1,155 ) 53,467 Trust preferred securities 5,000 — (750 ) 4,250 $ 1,049,932 $ 2,994 $ (20,058 ) $ 1,032,868 The amortized cost and fair value of debt securities available for sale at December 31, 2019 , by contractual final maturity is shown below. Expected maturities may differ from contractual maturities due to prepayment or early call options exercised by the issuer. December 31, 2019 Amortized Cost Fair Value (In thousands) One year or less $ 31,901 $ 31,955 More than one year to five years 27,366 27,729 More than five years to ten years 53,235 53,669 More than ten years 5,476 5,102 117,978 118,455 Mortgage-backed securities and collateralized mortgage obligations 968,165 979,881 $ 1,086,143 $ 1,098,336 Mortgage-backed securities and collateralized mortgage obligations totaling $968.2 million at amortized cost, and $979.9 million at fair value, are not classified by maturity in the table above as their expected lives are likely to be shorter than the contractual maturity date due to principal prepayments. (4) Debt Securities Available for Sale (continued) During the year ended December 31, 2019 , proceeds from the sales of debt securities available for sale totaled $65.2 million , resulting in gross gains of $2.2 million and gross losses of $22,000 . Proceeds from called debt securities available for sale totaled $24.1 million resulting in gross gains of $174,000 and no gross losses. Proceeds from one matured debt security available for sale totaled $797,000 . During the year ended December 31, 2018 , proceeds from calls of debt securities available for sale totaled $11.5 million , resulting in gross realized gains of $116,000 and no gross unrealized losses. Proceeds from maturities of securities available for sale totaled $2.4 million . During the three months ended December 31, 2017 , there were no sales, calls or maturities of debt securities available for sale during the period. During the year ended September 30, 2017, proceeds from sales of debt securities available for sale totaled $187.4 million , resulting in gross gains of $1.5 million and gross losses of $3.2 million . Proceeds from calls and maturities of securities available for sale totaled $17.2 million . Debt securities available for sale having a carrying value of $462.0 million and $232.7 million , respectively, at December 31, 2019 and 2018 , respectively, were pledged as security for public funds on deposit at the Bank as required and permitted by law, pledged for outstanding borrowings at the Federal Home Loan Bank, and pledged for potential borrowing at the Federal Reserve Bank of New York. The following table summarizes the fair value and gross unrealized losses of those securities that reported an unrealized loss at December 31, 2019 and 2018 and if the unrealized loss position was continuous for the twelve months prior to those respective dates: December 31, 2019 Less Than 12 Months 12 Months or Longer Total Fair Value Gross Unrealized (Losses) Fair Value Gross Unrealized (Losses) Fair Value Gross Unrealized (Losses) (In thousands) U.S. government and agency obligations $ 5,106 $ (13 ) $ 4,988 $ (3 ) $ 10,094 $ (16 ) Mortgage-backed securities and collateralized mortgage obligations 178,665 (946 ) 58,208 (319 ) 236,873 (1,265 ) Municipal obligations 696 (1 ) — — 696 (1 ) Corporate debt securities 2,588 (5 ) 4,627 (373 ) 7,215 (378 ) Trust preferred securities — — 4,605 (395 ) 4,605 (395 ) $ 187,055 $ (965 ) $ 72,428 $ (1,090 ) $ 259,483 $ (2,055 ) (4) Debt Securities Available for Sale (continued) December 31, 2018 Less Than 12 Months 12 Months or Longer Total Fair Value Gross Unrealized (Losses) Fair Value Gross Unrealized (Losses) Fair Value Gross Unrealized (Losses) (In thousands) U.S. government and agency obligations $ 14,668 $ (202 ) $ 29,437 $ (515 ) $ 44,105 $ (717 ) Mortgage-backed securities and collateralized mortgage obligations 176,614 (1,034 ) 509,397 (16,402 ) 686,011 (17,436 ) Corporate debt securities 26,480 (512 ) 9,358 (643 ) 35,838 (1,155 ) Trust preferred securities — — 4,250 (750 ) 4,250 (750 ) $ 217,762 $ (1,748 ) $ 552,442 $ (18,310 ) $ 770,204 $ (20,058 ) The Company evaluates securities for other-than-temporary impairment at each reporting period and more frequently when economic or market conditions warrant such evaluation. The temporary loss position associated with debt securities available for sale was the result of changes in market interest rates relative to the coupon of the individual security and changes in credit spreads. The Company does not have the intent to sell securities in a temporary loss position at December 31, 2019 , nor is it more likely than not that the Company will be required to sell the securities before the anticipated recovery. The number of securities in an unrealized loss position as of December 31, 2019 totaled 97 , compared with 151 at December 31, 2018 . All temporarily impaired securities were investment grade as of December 31, 2019 and 2018 . The Company did not record an other-than-temporary impairment charge on debt securities available for sale during the years ended December 31, 2019 and 2018 , September 30, 2017, and the three months ended December 31, 2017 . Debt securities held to maturity at December 31, 2019 and 2018 are summarized as follows: December 31, 2019 Amortized Cost Gross Unrealized Gains Gross Unrealized (Losses) Fair Value (In thousands) U.S. government and agency obligations $ 20,000 $ 26 $ (66 ) $ 19,960 Mortgage-backed securities and collateralized mortgage obligations 265,756 4,048 (259 ) 269,545 $ 285,756 $ 4,074 $ (325 ) $ 289,505 December 31, 2018 Amortized Cost Gross Unrealized Gains Gross Unrealized (Losses) Fair Value (In thousands) U.S. government and agency obligations $ 23,404 $ 45 $ (208 ) $ 23,241 Mortgage-backed securities and collateralized mortgage obligations 238,739 28 (7,167 ) 231,600 $ 262,143 $ 73 $ (7,375 ) $ 254,841 (5) Debt Securities Held to Maturity (continued) The amortized cost and fair value of debt securities held to maturity at December 31, 2019 , by contractual final maturity, is shown below. Expected maturities may differ from contractual maturities due to prepayment or early call options exercised by the issuer. December 31, 2019 Amortized Cost Fair Value (In thousands) More than ten years $ 20,000 $ 19,960 Mortgage-backed securities and collateralized mortgage obligations 265,756 269,545 $ 285,756 $ 289,505 Mortgage-backed securities and collateralized mortgage obligations totaling $265.8 million at amortized cost, and $269.5 million at fair value, are not classified by maturity in the table above as their expected lives are likely to be shorter than the contractual maturity date due to principal prepayments. There were no sales of debt securities held to maturity for the years ended December 31, 2019 and 2018, September 30, 2017, and the three months ended December 31, 2017 . Proceeds from calls of debt securities held to maturity for the year ended December 31, 2019 totaled $33.4 million , resulting in $24,000 of gross gains and no gross losses. Proceeds from calls and maturities of debt securities held to maturity for the years ended December 31, 2018 and September 30, 2017 totaled $5.4 million and $769,000 , respectively. No gross gains or losses were recognized. There were no calls or maturities of debt securities held to maturity for the three months ended December 31, 2017. Debt securities held to maturity having a carrying value of $236.0 million and $187.0 million , respectively, at December 31, 2019 and December 31, 2018 , respectively, were pledged as security for public funds on deposit at the Bank as required and permitted by law, pledged for outstanding borrowings at the Federal Home Loan Bank, and pledged for potential borrowing at the Federal Reserve Bank of New York. The following table summarizes the fair value and gross unrealized losses of those securities that reported an unrealized loss at December 31, 2019 and 2018 and if the unrealized loss position was continuous for the twelve months prior to those respective dates: December 31, 2019 Less Than 12 Months 12 Months or Longer Total Fair Value Gross Unrealized (Losses) Fair Value Gross Unrealized (Losses) Fair Value Gross Unrealized (Losses) (In thousands) U.S. government and agency obligations $ 9,934 $ (66 ) $ — $ — $ 9,934 $ (66 ) Mortgage-backed securities and collateralized mortgage obligations 27,911 (251 ) 772 (8 ) 28,683 (259 ) $ 37,845 $ (317 ) $ 772 $ (8 ) $ 38,617 $ (325 ) (5) Debt Securities Held to Maturity (continued) December 31, 2018 Less than 12 months 12 months or longer Total Fair Value Gross Unrealized (Losses) Fair Value Gross Unrealized (Losses) Fair Value Gross Unrealized (Losses) (In thousands) U.S. government and agency obligations $ — $ — $ 8,197 $ (208 ) $ 8,197 $ (208 ) Mortgage-backed securities and collateralized mortgage obligations 11,265 (69 ) 213,246 (7,098 ) 224,511 (7,167 ) $ 11,265 $ (69 ) $ 221,443 $ (7,306 ) $ 232,708 $ (7,375 ) The Company evaluates securities for other-than-temporary impairment at each reporting period and more frequently when economic or market conditions warrant such evaluation. The temporary loss position associated with debt securities held to maturity was the result of changes in market interest rates relative to the coupon of the individual security and changes in credit spreads. The Company does not have the intent to sell securities in a temporary loss position at December 31, 2019 , nor is it more likely than not that the Company will be required to sell the securities before the anticipated recovery. The number of securities in an unrealized loss position as of December 31, 2019 totaled 22 , compared with 88 at December 31, 2018 . All temporarily impaired securities were investment grade as of December 31, 2019 and 2018 . The Company did not record an other-than-temporary impairment charge on debt securities held to maturity for the years ended December 31, 2019 and 2018 , September 30, 2017, and the three months ended December 31, 2017 . During the year ended September 30, 2017, the Company transferred certain debt securities available for sale with an amortized cost of $103.7 million and a fair value of $103.3 million The Company has an equity securities portfolio which consists of stock in other financial institutions, a payment technology company, and a community bank correspondent services company, which is reported at fair value on the Company's Consolidated Statements of Financial Condition. The fair value of the equities portfolio at December 31, 2019 and 2018 was $2.9 million and $1.9 million , respectively. The Company adopted ASU 2016-01 on January 1, 2019, resulting in a $548,000 after tax cumulative-effect adjustment from other comprehensive income (loss) to retained earnings, as reflected in the Consolidated Statements of Changes in Stockholders' Equity. The Company recorded the net increase in the fair value of equity securities of $305,000 for the year ended December 31, 2019 as a component of non-interest income. During the year ended December 31, 2019 , proceeds from the sale of equity securities totaled $1.1 million , resulting in gross gains of $236,000 and no gross losses. During the years ended December 31, 2018 and September 30, 2017, there were no sales of equity securities. During the three months ended December 31, 2017, proceeds from sales of equity securities totaled $92,000 , resulting in no gross realized gains and $60,000

Debt Securities Held to Maturit

Debt Securities Held to Maturity	12 Months Ended
Debt Securities Held to Maturity	Dec. 31, 2019
Investments, Debt and Equity Securities [Abstract]
Debt Securities Held to Maturity	Debt Securities Available for Sale Debt s ecurities available for sale at December 31, 2019 and 2018 are summarized as follows: December 31, 2019 Amortized Cost Gross Unrealized Gains Gross Unrealized (Losses) Fair Value (In thousands) U.S. government and agency obligations $ 42,081 $ 321 $ (16 ) $ 42,386 Mortgage-backed securities and collateralized mortgage obligations 968,165 12,981 (1,265 ) 979,881 Municipal obligations 2,284 1 (1 ) 2,284 Corporate debt securities 68,613 945 (378 ) 69,180 Trust preferred securities 5,000 — (395 ) 4,605 $ 1,086,143 $ 14,248 $ (2,055 ) $ 1,098,336 December 31, 2018 Amortized Cost Gross Unrealized Gains Gross Unrealized (Losses) Fair Value (In thousands) U.S. government and agency obligations $ 54,821 $ 53 $ (717 ) $ 54,157 Mortgage-backed securities and collateralized mortgage obligations 934,631 2,812 (17,436 ) 920,007 Municipal obligations 987 — — 987 Corporate debt securities 54,493 129 (1,155 ) 53,467 Trust preferred securities 5,000 — (750 ) 4,250 $ 1,049,932 $ 2,994 $ (20,058 ) $ 1,032,868 The amortized cost and fair value of debt securities available for sale at December 31, 2019 , by contractual final maturity is shown below. Expected maturities may differ from contractual maturities due to prepayment or early call options exercised by the issuer. December 31, 2019 Amortized Cost Fair Value (In thousands) One year or less $ 31,901 $ 31,955 More than one year to five years 27,366 27,729 More than five years to ten years 53,235 53,669 More than ten years 5,476 5,102 117,978 118,455 Mortgage-backed securities and collateralized mortgage obligations 968,165 979,881 $ 1,086,143 $ 1,098,336 Mortgage-backed securities and collateralized mortgage obligations totaling $968.2 million at amortized cost, and $979.9 million at fair value, are not classified by maturity in the table above as their expected lives are likely to be shorter than the contractual maturity date due to principal prepayments. (4) Debt Securities Available for Sale (continued) During the year ended December 31, 2019 , proceeds from the sales of debt securities available for sale totaled $65.2 million , resulting in gross gains of $2.2 million and gross losses of $22,000 . Proceeds from called debt securities available for sale totaled $24.1 million resulting in gross gains of $174,000 and no gross losses. Proceeds from one matured debt security available for sale totaled $797,000 . During the year ended December 31, 2018 , proceeds from calls of debt securities available for sale totaled $11.5 million , resulting in gross realized gains of $116,000 and no gross unrealized losses. Proceeds from maturities of securities available for sale totaled $2.4 million . During the three months ended December 31, 2017 , there were no sales, calls or maturities of debt securities available for sale during the period. During the year ended September 30, 2017, proceeds from sales of debt securities available for sale totaled $187.4 million , resulting in gross gains of $1.5 million and gross losses of $3.2 million . Proceeds from calls and maturities of securities available for sale totaled $17.2 million . Debt securities available for sale having a carrying value of $462.0 million and $232.7 million , respectively, at December 31, 2019 and 2018 , respectively, were pledged as security for public funds on deposit at the Bank as required and permitted by law, pledged for outstanding borrowings at the Federal Home Loan Bank, and pledged for potential borrowing at the Federal Reserve Bank of New York. The following table summarizes the fair value and gross unrealized losses of those securities that reported an unrealized loss at December 31, 2019 and 2018 and if the unrealized loss position was continuous for the twelve months prior to those respective dates: December 31, 2019 Less Than 12 Months 12 Months or Longer Total Fair Value Gross Unrealized (Losses) Fair Value Gross Unrealized (Losses) Fair Value Gross Unrealized (Losses) (In thousands) U.S. government and agency obligations $ 5,106 $ (13 ) $ 4,988 $ (3 ) $ 10,094 $ (16 ) Mortgage-backed securities and collateralized mortgage obligations 178,665 (946 ) 58,208 (319 ) 236,873 (1,265 ) Municipal obligations 696 (1 ) — — 696 (1 ) Corporate debt securities 2,588 (5 ) 4,627 (373 ) 7,215 (378 ) Trust preferred securities — — 4,605 (395 ) 4,605 (395 ) $ 187,055 $ (965 ) $ 72,428 $ (1,090 ) $ 259,483 $ (2,055 ) (4) Debt Securities Available for Sale (continued) December 31, 2018 Less Than 12 Months 12 Months or Longer Total Fair Value Gross Unrealized (Losses) Fair Value Gross Unrealized (Losses) Fair Value Gross Unrealized (Losses) (In thousands) U.S. government and agency obligations $ 14,668 $ (202 ) $ 29,437 $ (515 ) $ 44,105 $ (717 ) Mortgage-backed securities and collateralized mortgage obligations 176,614 (1,034 ) 509,397 (16,402 ) 686,011 (17,436 ) Corporate debt securities 26,480 (512 ) 9,358 (643 ) 35,838 (1,155 ) Trust preferred securities — — 4,250 (750 ) 4,250 (750 ) $ 217,762 $ (1,748 ) $ 552,442 $ (18,310 ) $ 770,204 $ (20,058 ) The Company evaluates securities for other-than-temporary impairment at each reporting period and more frequently when economic or market conditions warrant such evaluation. The temporary loss position associated with debt securities available for sale was the result of changes in market interest rates relative to the coupon of the individual security and changes in credit spreads. The Company does not have the intent to sell securities in a temporary loss position at December 31, 2019 , nor is it more likely than not that the Company will be required to sell the securities before the anticipated recovery. The number of securities in an unrealized loss position as of December 31, 2019 totaled 97 , compared with 151 at December 31, 2018 . All temporarily impaired securities were investment grade as of December 31, 2019 and 2018 . The Company did not record an other-than-temporary impairment charge on debt securities available for sale during the years ended December 31, 2019 and 2018 , September 30, 2017, and the three months ended December 31, 2017 . Debt securities held to maturity at December 31, 2019 and 2018 are summarized as follows: December 31, 2019 Amortized Cost Gross Unrealized Gains Gross Unrealized (Losses) Fair Value (In thousands) U.S. government and agency obligations $ 20,000 $ 26 $ (66 ) $ 19,960 Mortgage-backed securities and collateralized mortgage obligations 265,756 4,048 (259 ) 269,545 $ 285,756 $ 4,074 $ (325 ) $ 289,505 December 31, 2018 Amortized Cost Gross Unrealized Gains Gross Unrealized (Losses) Fair Value (In thousands) U.S. government and agency obligations $ 23,404 $ 45 $ (208 ) $ 23,241 Mortgage-backed securities and collateralized mortgage obligations 238,739 28 (7,167 ) 231,600 $ 262,143 $ 73 $ (7,375 ) $ 254,841 (5) Debt Securities Held to Maturity (continued) The amortized cost and fair value of debt securities held to maturity at December 31, 2019 , by contractual final maturity, is shown below. Expected maturities may differ from contractual maturities due to prepayment or early call options exercised by the issuer. December 31, 2019 Amortized Cost Fair Value (In thousands) More than ten years $ 20,000 $ 19,960 Mortgage-backed securities and collateralized mortgage obligations 265,756 269,545 $ 285,756 $ 289,505 Mortgage-backed securities and collateralized mortgage obligations totaling $265.8 million at amortized cost, and $269.5 million at fair value, are not classified by maturity in the table above as their expected lives are likely to be shorter than the contractual maturity date due to principal prepayments. There were no sales of debt securities held to maturity for the years ended December 31, 2019 and 2018, September 30, 2017, and the three months ended December 31, 2017 . Proceeds from calls of debt securities held to maturity for the year ended December 31, 2019 totaled $33.4 million , resulting in $24,000 of gross gains and no gross losses. Proceeds from calls and maturities of debt securities held to maturity for the years ended December 31, 2018 and September 30, 2017 totaled $5.4 million and $769,000 , respectively. No gross gains or losses were recognized. There were no calls or maturities of debt securities held to maturity for the three months ended December 31, 2017. Debt securities held to maturity having a carrying value of $236.0 million and $187.0 million , respectively, at December 31, 2019 and December 31, 2018 , respectively, were pledged as security for public funds on deposit at the Bank as required and permitted by law, pledged for outstanding borrowings at the Federal Home Loan Bank, and pledged for potential borrowing at the Federal Reserve Bank of New York. The following table summarizes the fair value and gross unrealized losses of those securities that reported an unrealized loss at December 31, 2019 and 2018 and if the unrealized loss position was continuous for the twelve months prior to those respective dates: December 31, 2019 Less Than 12 Months 12 Months or Longer Total Fair Value Gross Unrealized (Losses) Fair Value Gross Unrealized (Losses) Fair Value Gross Unrealized (Losses) (In thousands) U.S. government and agency obligations $ 9,934 $ (66 ) $ — $ — $ 9,934 $ (66 ) Mortgage-backed securities and collateralized mortgage obligations 27,911 (251 ) 772 (8 ) 28,683 (259 ) $ 37,845 $ (317 ) $ 772 $ (8 ) $ 38,617 $ (325 ) (5) Debt Securities Held to Maturity (continued) December 31, 2018 Less than 12 months 12 months or longer Total Fair Value Gross Unrealized (Losses) Fair Value Gross Unrealized (Losses) Fair Value Gross Unrealized (Losses) (In thousands) U.S. government and agency obligations $ — $ — $ 8,197 $ (208 ) $ 8,197 $ (208 ) Mortgage-backed securities and collateralized mortgage obligations 11,265 (69 ) 213,246 (7,098 ) 224,511 (7,167 ) $ 11,265 $ (69 ) $ 221,443 $ (7,306 ) $ 232,708 $ (7,375 ) The Company evaluates securities for other-than-temporary impairment at each reporting period and more frequently when economic or market conditions warrant such evaluation. The temporary loss position associated with debt securities held to maturity was the result of changes in market interest rates relative to the coupon of the individual security and changes in credit spreads. The Company does not have the intent to sell securities in a temporary loss position at December 31, 2019 , nor is it more likely than not that the Company will be required to sell the securities before the anticipated recovery. The number of securities in an unrealized loss position as of December 31, 2019 totaled 22 , compared with 88 at December 31, 2018 . All temporarily impaired securities were investment grade as of December 31, 2019 and 2018 . The Company did not record an other-than-temporary impairment charge on debt securities held to maturity for the years ended December 31, 2019 and 2018 , September 30, 2017, and the three months ended December 31, 2017 . During the year ended September 30, 2017, the Company transferred certain debt securities available for sale with an amortized cost of $103.7 million and a fair value of $103.3 million The Company has an equity securities portfolio which consists of stock in other financial institutions, a payment technology company, and a community bank correspondent services company, which is reported at fair value on the Company's Consolidated Statements of Financial Condition. The fair value of the equities portfolio at December 31, 2019 and 2018 was $2.9 million and $1.9 million , respectively. The Company adopted ASU 2016-01 on January 1, 2019, resulting in a $548,000 after tax cumulative-effect adjustment from other comprehensive income (loss) to retained earnings, as reflected in the Consolidated Statements of Changes in Stockholders' Equity. The Company recorded the net increase in the fair value of equity securities of $305,000 for the year ended December 31, 2019 as a component of non-interest income. During the year ended December 31, 2019 , proceeds from the sale of equity securities totaled $1.1 million , resulting in gross gains of $236,000 and no gross losses. During the years ended December 31, 2018 and September 30, 2017, there were no sales of equity securities. During the three months ended December 31, 2017, proceeds from sales of equity securities totaled $92,000 , resulting in no gross realized gains and $60,000

Equity Securities at Fair Value

Equity Securities at Fair Value	12 Months Ended
Equity Securities at Fair Value	Dec. 31, 2019
Investments, Debt and Equity Securities [Abstract]
Equity Securities at Fair Value	Debt Securities Available for Sale Debt s ecurities available for sale at December 31, 2019 and 2018 are summarized as follows: December 31, 2019 Amortized Cost Gross Unrealized Gains Gross Unrealized (Losses) Fair Value (In thousands) U.S. government and agency obligations $ 42,081 $ 321 $ (16 ) $ 42,386 Mortgage-backed securities and collateralized mortgage obligations 968,165 12,981 (1,265 ) 979,881 Municipal obligations 2,284 1 (1 ) 2,284 Corporate debt securities 68,613 945 (378 ) 69,180 Trust preferred securities 5,000 — (395 ) 4,605 $ 1,086,143 $ 14,248 $ (2,055 ) $ 1,098,336 December 31, 2018 Amortized Cost Gross Unrealized Gains Gross Unrealized (Losses) Fair Value (In thousands) U.S. government and agency obligations $ 54,821 $ 53 $ (717 ) $ 54,157 Mortgage-backed securities and collateralized mortgage obligations 934,631 2,812 (17,436 ) 920,007 Municipal obligations 987 — — 987 Corporate debt securities 54,493 129 (1,155 ) 53,467 Trust preferred securities 5,000 — (750 ) 4,250 $ 1,049,932 $ 2,994 $ (20,058 ) $ 1,032,868 The amortized cost and fair value of debt securities available for sale at December 31, 2019 , by contractual final maturity is shown below. Expected maturities may differ from contractual maturities due to prepayment or early call options exercised by the issuer. December 31, 2019 Amortized Cost Fair Value (In thousands) One year or less $ 31,901 $ 31,955 More than one year to five years 27,366 27,729 More than five years to ten years 53,235 53,669 More than ten years 5,476 5,102 117,978 118,455 Mortgage-backed securities and collateralized mortgage obligations 968,165 979,881 $ 1,086,143 $ 1,098,336 Mortgage-backed securities and collateralized mortgage obligations totaling $968.2 million at amortized cost, and $979.9 million at fair value, are not classified by maturity in the table above as their expected lives are likely to be shorter than the contractual maturity date due to principal prepayments. (4) Debt Securities Available for Sale (continued) During the year ended December 31, 2019 , proceeds from the sales of debt securities available for sale totaled $65.2 million , resulting in gross gains of $2.2 million and gross losses of $22,000 . Proceeds from called debt securities available for sale totaled $24.1 million resulting in gross gains of $174,000 and no gross losses. Proceeds from one matured debt security available for sale totaled $797,000 . During the year ended December 31, 2018 , proceeds from calls of debt securities available for sale totaled $11.5 million , resulting in gross realized gains of $116,000 and no gross unrealized losses. Proceeds from maturities of securities available for sale totaled $2.4 million . During the three months ended December 31, 2017 , there were no sales, calls or maturities of debt securities available for sale during the period. During the year ended September 30, 2017, proceeds from sales of debt securities available for sale totaled $187.4 million , resulting in gross gains of $1.5 million and gross losses of $3.2 million . Proceeds from calls and maturities of securities available for sale totaled $17.2 million . Debt securities available for sale having a carrying value of $462.0 million and $232.7 million , respectively, at December 31, 2019 and 2018 , respectively, were pledged as security for public funds on deposit at the Bank as required and permitted by law, pledged for outstanding borrowings at the Federal Home Loan Bank, and pledged for potential borrowing at the Federal Reserve Bank of New York. The following table summarizes the fair value and gross unrealized losses of those securities that reported an unrealized loss at December 31, 2019 and 2018 and if the unrealized loss position was continuous for the twelve months prior to those respective dates: December 31, 2019 Less Than 12 Months 12 Months or Longer Total Fair Value Gross Unrealized (Losses) Fair Value Gross Unrealized (Losses) Fair Value Gross Unrealized (Losses) (In thousands) U.S. government and agency obligations $ 5,106 $ (13 ) $ 4,988 $ (3 ) $ 10,094 $ (16 ) Mortgage-backed securities and collateralized mortgage obligations 178,665 (946 ) 58,208 (319 ) 236,873 (1,265 ) Municipal obligations 696 (1 ) — — 696 (1 ) Corporate debt securities 2,588 (5 ) 4,627 (373 ) 7,215 (378 ) Trust preferred securities — — 4,605 (395 ) 4,605 (395 ) $ 187,055 $ (965 ) $ 72,428 $ (1,090 ) $ 259,483 $ (2,055 ) (4) Debt Securities Available for Sale (continued) December 31, 2018 Less Than 12 Months 12 Months or Longer Total Fair Value Gross Unrealized (Losses) Fair Value Gross Unrealized (Losses) Fair Value Gross Unrealized (Losses) (In thousands) U.S. government and agency obligations $ 14,668 $ (202 ) $ 29,437 $ (515 ) $ 44,105 $ (717 ) Mortgage-backed securities and collateralized mortgage obligations 176,614 (1,034 ) 509,397 (16,402 ) 686,011 (17,436 ) Corporate debt securities 26,480 (512 ) 9,358 (643 ) 35,838 (1,155 ) Trust preferred securities — — 4,250 (750 ) 4,250 (750 ) $ 217,762 $ (1,748 ) $ 552,442 $ (18,310 ) $ 770,204 $ (20,058 ) The Company evaluates securities for other-than-temporary impairment at each reporting period and more frequently when economic or market conditions warrant such evaluation. The temporary loss position associated with debt securities available for sale was the result of changes in market interest rates relative to the coupon of the individual security and changes in credit spreads. The Company does not have the intent to sell securities in a temporary loss position at December 31, 2019 , nor is it more likely than not that the Company will be required to sell the securities before the anticipated recovery. The number of securities in an unrealized loss position as of December 31, 2019 totaled 97 , compared with 151 at December 31, 2018 . All temporarily impaired securities were investment grade as of December 31, 2019 and 2018 . The Company did not record an other-than-temporary impairment charge on debt securities available for sale during the years ended December 31, 2019 and 2018 , September 30, 2017, and the three months ended December 31, 2017 . Debt securities held to maturity at December 31, 2019 and 2018 are summarized as follows: December 31, 2019 Amortized Cost Gross Unrealized Gains Gross Unrealized (Losses) Fair Value (In thousands) U.S. government and agency obligations $ 20,000 $ 26 $ (66 ) $ 19,960 Mortgage-backed securities and collateralized mortgage obligations 265,756 4,048 (259 ) 269,545 $ 285,756 $ 4,074 $ (325 ) $ 289,505 December 31, 2018 Amortized Cost Gross Unrealized Gains Gross Unrealized (Losses) Fair Value (In thousands) U.S. government and agency obligations $ 23,404 $ 45 $ (208 ) $ 23,241 Mortgage-backed securities and collateralized mortgage obligations 238,739 28 (7,167 ) 231,600 $ 262,143 $ 73 $ (7,375 ) $ 254,841 (5) Debt Securities Held to Maturity (continued) The amortized cost and fair value of debt securities held to maturity at December 31, 2019 , by contractual final maturity, is shown below. Expected maturities may differ from contractual maturities due to prepayment or early call options exercised by the issuer. December 31, 2019 Amortized Cost Fair Value (In thousands) More than ten years $ 20,000 $ 19,960 Mortgage-backed securities and collateralized mortgage obligations 265,756 269,545 $ 285,756 $ 289,505 Mortgage-backed securities and collateralized mortgage obligations totaling $265.8 million at amortized cost, and $269.5 million at fair value, are not classified by maturity in the table above as their expected lives are likely to be shorter than the contractual maturity date due to principal prepayments. There were no sales of debt securities held to maturity for the years ended December 31, 2019 and 2018, September 30, 2017, and the three months ended December 31, 2017 . Proceeds from calls of debt securities held to maturity for the year ended December 31, 2019 totaled $33.4 million , resulting in $24,000 of gross gains and no gross losses. Proceeds from calls and maturities of debt securities held to maturity for the years ended December 31, 2018 and September 30, 2017 totaled $5.4 million and $769,000 , respectively. No gross gains or losses were recognized. There were no calls or maturities of debt securities held to maturity for the three months ended December 31, 2017. Debt securities held to maturity having a carrying value of $236.0 million and $187.0 million , respectively, at December 31, 2019 and December 31, 2018 , respectively, were pledged as security for public funds on deposit at the Bank as required and permitted by law, pledged for outstanding borrowings at the Federal Home Loan Bank, and pledged for potential borrowing at the Federal Reserve Bank of New York. The following table summarizes the fair value and gross unrealized losses of those securities that reported an unrealized loss at December 31, 2019 and 2018 and if the unrealized loss position was continuous for the twelve months prior to those respective dates: December 31, 2019 Less Than 12 Months 12 Months or Longer Total Fair Value Gross Unrealized (Losses) Fair Value Gross Unrealized (Losses) Fair Value Gross Unrealized (Losses) (In thousands) U.S. government and agency obligations $ 9,934 $ (66 ) $ — $ — $ 9,934 $ (66 ) Mortgage-backed securities and collateralized mortgage obligations 27,911 (251 ) 772 (8 ) 28,683 (259 ) $ 37,845 $ (317 ) $ 772 $ (8 ) $ 38,617 $ (325 ) (5) Debt Securities Held to Maturity (continued) December 31, 2018 Less than 12 months 12 months or longer Total Fair Value Gross Unrealized (Losses) Fair Value Gross Unrealized (Losses) Fair Value Gross Unrealized (Losses) (In thousands) U.S. government and agency obligations $ — $ — $ 8,197 $ (208 ) $ 8,197 $ (208 ) Mortgage-backed securities and collateralized mortgage obligations 11,265 (69 ) 213,246 (7,098 ) 224,511 (7,167 ) $ 11,265 $ (69 ) $ 221,443 $ (7,306 ) $ 232,708 $ (7,375 ) The Company evaluates securities for other-than-temporary impairment at each reporting period and more frequently when economic or market conditions warrant such evaluation. The temporary loss position associated with debt securities held to maturity was the result of changes in market interest rates relative to the coupon of the individual security and changes in credit spreads. The Company does not have the intent to sell securities in a temporary loss position at December 31, 2019 , nor is it more likely than not that the Company will be required to sell the securities before the anticipated recovery. The number of securities in an unrealized loss position as of December 31, 2019 totaled 22 , compared with 88 at December 31, 2018 . All temporarily impaired securities were investment grade as of December 31, 2019 and 2018 . The Company did not record an other-than-temporary impairment charge on debt securities held to maturity for the years ended December 31, 2019 and 2018 , September 30, 2017, and the three months ended December 31, 2017 . During the year ended September 30, 2017, the Company transferred certain debt securities available for sale with an amortized cost of $103.7 million and a fair value of $103.3 million The Company has an equity securities portfolio which consists of stock in other financial institutions, a payment technology company, and a community bank correspondent services company, which is reported at fair value on the Company's Consolidated Statements of Financial Condition. The fair value of the equities portfolio at December 31, 2019 and 2018 was $2.9 million and $1.9 million , respectively. The Company adopted ASU 2016-01 on January 1, 2019, resulting in a $548,000 after tax cumulative-effect adjustment from other comprehensive income (loss) to retained earnings, as reflected in the Consolidated Statements of Changes in Stockholders' Equity. The Company recorded the net increase in the fair value of equity securities of $305,000 for the year ended December 31, 2019 as a component of non-interest income. During the year ended December 31, 2019 , proceeds from the sale of equity securities totaled $1.1 million , resulting in gross gains of $236,000 and no gross losses. During the years ended December 31, 2018 and September 30, 2017, there were no sales of equity securities. During the three months ended December 31, 2017, proceeds from sales of equity securities totaled $92,000 , resulting in no gross realized gains and $60,000

Loans Receivable and Allowance

Loans Receivable and Allowance for Loan Losses	12 Months Ended
Loans Receivable and Allowance for Loan Losses	Dec. 31, 2019
Receivables [Abstract]
Loans Receivable and Allowance for Loan Losses	Loans Receivable and Allowance for Loan Losses Loans receivable at December 31, 2019 and 2018 are summarized as follows: December 31, 2019 2018 (In thousands) Real estate loans: One-to-four family $ 2,077,079 $ 1,830,186 Multifamily and commercial 2,919,985 2,142,154 Construction 298,942 261,473 Commercial business loans 483,215 333,876 Consumer loans: Home equity loans and advances 388,127 393,492 Other consumer loans 1,960 1,108 Total gross loans 6,169,308 4,962,289 Purchased credit-impaired loans 7,021 — Net deferred loan costs, fees and purchased premiums and discounts 21,237 16,893 Loans receivable $ 6,197,566 $ 4,979,182 There were no loans held for sale at December 31, 2019 , and $8.1 million of one-to-four family real estate loans were held-for-sale at December 31, 2018. During the year ended December 31, 2019 , the Company sold $97.4 million , $4.3 million , and $164,000 of one-to-four family and fixed rate home equity loans, commercial real estate and commercial business loans, respectively, to third parties. Gross gains of $718,000 and no gross losses were recognized from the sales of loans. During the year ended December 31, 2018, the Company sold $3.6 million of one-to-four family and fixed rate home equity loans resulting in no gross gains or losses. During the year ended September 30, 2017 and the three months ended December 31, 2017 no loans held-for-sale were sold by the Company. During the year ended December 31, 2019 , the Company sold $5.3 million , $5.5 million , and $901,000 of one-to-four family and fixed rate home equity loans, commercial real estate and commercial business loans, respectively, included in loans receivable. Gross gains of $67,000 and no gross losses were recognized from the sales of loans. During the year ended December 31, 2018, the Company sold $32.0 million of one-to-four family and fixed rate home equity loans to third parties, resulting in gross gains of $618,000 and no gross losses. For the year ended September 30, 2017, the Company sold $62.4 million of one-to-four family and fixed rate home equity, and multifamily loans to third parties resulting in no gross gains and $380,000 of gross losses. During the years ended December 31, 2019 and 2018 , and September 30, 2017, the Company purchased $89.8 million , $32.3 million and $20.5 million , respectively, of one-to-four family, multifamily and commercial real estate loans. During the three months ended December 31, 2017, the Company purchased $56.1 million of multifamily and commercial real estate loans. At December 31, 2019 and 2018 , the carrying value of loans serviced by the Company for investors was $526.3 million and $462.7 million , respectively. These loans are not included in the Consolidated Statements of Financial Condition. Servicing income totaled $1.2 million , $1.1 million , and $1.2 million for the year ended December 31, 2019 and 2018 , September 30, 2017. For the three months ended December 31, 2017 servicing income totaled $298,000 . The Company has entered into Guarantor Swaps with Freddie Mac which results in improved liquidity. During the year ended December 31, 2019 , the Company exchanged $21.6 million of loans for a Freddie Mac Mortgage Participation Certificate. The Company retained the servicing of these loans. No loans were sold to Freddie Mac in exchange for Freddie Mac Mortgage Participation Certificates during the years ended December 31, 2018 and September 30, 2017, or during the three months ended December 31, 2017. The Company has granted loans to certain officers and directors of the Company and its subsidiaries and to their associates. As of December 31, 2019 and 2018 such loans totaled approximately $1.1 million and $1.4 million , respectively. During the years ended December 31, 2019 and 2018 and the three months ended December 31, 2017, the Bank granted no new loans to related parties. During the year ended September 30, 2017, new loans totaling $390,000 were granted to related parties. These loans are performing in accordance with their original terms. (7) Loans Receivable and Allowance for Loan Losses (continued) The following tables summarize the aging of loans receivable by portfolio segment, excluding PCI loans at December 31, 2019 and 2018 : December 31, 2019 30-59 Days 60-89 Days 90 Days or More Total Past Due Current Total (In thousands) Real estate loans: One-to-four family $ 6,249 $ 2,132 $ 1,638 $ 10,019 $ 2,067,060 $ 2,077,079 Multifamily and commercial 626 1,210 716 2,552 2,917,433 2,919,985 Construction — — — — 298,942 298,942 Commercial business loans 1,056 — 2,489 3,545 479,670 483,215 Consumer loans: Home equity loans and advances 1,708 246 405 2,359 385,768 388,127 Other consumer loans 3 — — 3 1,957 1,960 Total loans $ 9,642 $ 3,588 $ 5,248 $ 18,478 $ 6,150,830 $ 6,169,308 December 31, 2018 30-59 Days 60-89 Days 90 Days or More Total Past Due Current Total (In thousands) Real estate loans: One-to-four family $ 8,384 $ 1,518 $ 819 $ 10,721 $ 1,819,465 $ 1,830,186 Multifamily and commercial 1,870 1,425 154 3,449 2,138,705 2,142,154 Construction — — — — 261,473 261,473 Commercial business loans 208 279 911 1,398 332,478 333,876 Consumer loans: Home equity loans and advances 1,550 173 905 2,628 390,864 393,492 Other consumer loans — — — — 1,108 1,108 Total loans $ 12,012 $ 3,395 $ 2,789 $ 18,196 $ 4,944,093 $ 4,962,289 The Company considers a loan to be delinquent when we have not received a payment within 30 days of its contractual due date. Generally, a loan is designated as a non-accrual loan when the payment of interest is 90 days or more in arrears of its contractual due date, or repayment is unlikely. Non-accruing loans are returned to an accrual status after there has been a sustained period of repayment performance (generally six consecutive months of payments) and both principal and interest are deemed collectible. The Company identifies loans that may need to be charged-off as a loss, by reviewing all delinquent loans, classified loans and other loans that management may have concerns about collectability. At December 31, 2019 and 2018 , non-accrual loans totaled $6.7 million and $2.8 million , respectively. Included in non-accrual loans at December 31, 2019 , are 8 loans totaling $1.5 million which are less than 90 days in arrears. At December 31, 2018 , no loans less than 90 days in arrears were included in non-accrual loans. PCI loans are accounted for in accordance with ASC Subtopic 310-30 and are initially recorded at fair value (as determined by the present value of expected future cash flows) with no valuation allowance (i.e., the allowance for loan losses), and aggregated and accounted for as pools of loans based on common risk characteristics. The difference between the undiscounted cash flows expected at acquisition and the initial carrying amount (fair value) of the PCI loans, or the “accretable yield,” is recognized as interest income utilizing the level-yield method over the life of each pool. Contractually required payments for interest and principal that exceed the undiscounted cash flows expected at acquisition, or the “non-accretable difference,” are not recognized as a yield adjustment, as a loss accrual or a valuation allowance. Reclassifications of the non-accretable difference to the accretable yield may occur subsequent to the loan acquisition dates due to increases in expected cash flows of the loan pools. See Note 2 for additional information. (7) Loans Receivable and Allowance for Loan Losses (continued) The following table presents information regarding the estimates of the contractually required payments, the cash flows expected to be collected, and the estimated fair value of the PCI loans acquired in the Stewardship acquisition as of November 1, 2019 (See Note 3 for more details): November 1, 2019 (In thousands) Contractually required principal and interest $ 9,286 Contractual cash flows not expected to be collected (non-accretable difference) (1,823 ) Expected cash flows to be collected 7,463 Interest component of expected cash flows (accretable yield) (556 ) Fair value of acquired loans $ 6,907 The following table presents changes in the accretable yield for PCI loans for the year ended December 31, 2019: December 31, 2019 (In thousands) Balance, beginning of period $ — Acquisition 556 Accretion (30 ) Net change in expected cash flows (15 ) Balance, end of period $ 511 There were no PCI loans outstanding at December 31, 2018. The net increase in expected cash flows for certain pools of loans included in the table above is recognized prospectively as an adjustment to the yield over the estimated remaining life of the individual pools. The following table provides information with respect to our non-accrual loans, excluding PCI loans at December 31, 2019 and 2018 : December 31, 2019 2018 (In thousands) Non-accrual loans: Real estate loans: One-to-four family $ 1,732 $ 819 Multifamily and commercial 716 154 Commercial business loans 3,686 911 Consumer loans: Home equity loans and advances 553 905 Total non-accrual loans $ 6,687 $ 2,789 If the non-accrual loans had performed in accordance with their original terms, interest income would have increased by $509,000 , $126,000 , $295,000 , and $61,000 for the years ended December 31, 2019 and 2018 , September 30, 2017, and the three months ended December 31, 2017, respectively. The amount of cash basis interest income that was recognized on these loans during the years ended (7) Loans Receivable and Allowance for Loan Losses (continued) December 31, 2019 and 2018 , September 30, 2017, and the three months ended December 31, 2017 was $437,000 , $89,000 , $104,000 , and $121,000 , respectively. We may obtain physical possession of real estate collateralizing a residential mortgage loan via foreclosure or through an in-substance repossession. At December 31, 2019 , the Company had no real estate owned. At December 31, 2018 , we held one single-family property in real estate owned with a carrying value of $92,000 that was acquired through foreclosure on a residential mortgage loan. At of December 31, 2019 and 2018 , we had 4 and 14 residential mortgage loans with carrying values of $522,000 and $1.6 million , respectively, collateralized by residential real estate which are in the process of foreclosure. The Company maintains the allowance for loan losses through provisions for loan losses which are charged to income. Charge-offs against the allowance for loan losses are taken on loans where management determines that the collection of loan principal is unlikely. Recoveries made on loans that have been charged-off are credited to the allowance for loan losses. As part of the evaluation of the adequacy of the allowance for loan losses, management prepares an analysis each quarter that categorizes the entire loan portfolio by certain risk characteristics such as loan type (residential mortgage, commercial mortgage, construction, commercial, etc.) and loan risk rating. The Company utilizes an eight-point risk rating system to summarize its loan portfolio into categories with similar risk characteristics. Loans deemed to be “acceptable quality” are rated 1 through 4 (Pass), with a rating of 1 established for loans with minimal risk. Loans that are deemed to be of “questionable quality” are rated 5 (Special Mention) or 6 (Substandard). Loans with adverse classifications are rated 7 (Doubtful) or 8 (Loss). The risk ratings are also confirmed through periodic loan review examinations, which are currently performed by both an independent third-party and the Company's internal loan review department. The Company requires an annual review be performed above certain dollar thresholds, depending on loan type, to help determine the appropriate risk ratings. Results from examinations are presented to the Audit Committee of the Board of Directors. Management estimates the quantitative component of the allowance for loan losses for loans collectively evaluated for impairment by applying loss factors based upon the loan type categorization, risk rating level, and applying qualitative adjustments at the portfolio level. Quantitative loss factors give consideration to historical loss experience and migration experience by loan type over a look-back period, adjusted for a loss emergence period. Qualitative factor adjustments give consideration to other qualitative or environmental factors such as trends and levels of delinquencies, impaired loans, charge-offs, recoveries and loan volumes, as well as national and local economic trends and conditions. Qualitative factor adjustments to such loss factors are made to reflect risks in the loan portfolio not captured by the quantitative loss factors and, as such, are evaluated from a risk level perspective relative to the risk levels present over the look-back period. The reserves resulting from the application of both the quantitative experience and qualitative factors are combined to arrive at the allowance for loan losses for loans collectively evaluated for impairment. Management believes the primary risks inherent in the portfolio are a general decline in the economy, a decline in real estate market values, rising unemployment, increasing vacancy rates, and increases in interest rates in the absence of economic improvement. Any one or a combination of these events may adversely affect a borrowers’ ability to repay its loan, resulting in increased delinquencies and loan losses. Accordingly, the Company has recorded loan losses at a level which is estimated to represent the current risk in its loan portfolio. Management considers it important to maintain the ratio of the allowance for loan losses to total loans at an acceptable level considering the current composition of the loan portfolio. Although management believes that the Company has established and maintains the allowance for loan losses at appropriate levels, additional reserves may be necessary if future economic and other conditions differ substantially from the current operating environment. Management evaluates its estimates and assumptions on an ongoing basis and the estimates and assumptions are adjusted when facts and circumstances necessitate a re-valuation of the estimate. As future events and their effects cannot be determined with precision, actual results could differ significantly from these estimates. In addition, regulatory agencies periodically review the adequacy of the Company’s allowance for loan losses as an integral part of their examination process. Such agencies may require the Company to recognize additions to the allowance or additional write-downs based on their judgments about information available to them at the time of their examination. Although management uses the best information available, the level of the allowance for loan losses remains an estimate that is subject to significant uncertainties. The Bank defines a loan as impaired when, based on current information and events, it is probable that a creditor will be unable to collect all amounts due under the contractual terms of the loan agreement. All multifamily and commercial real estate, construction, and commercial business loans with an outstanding balance of greater than $500,000 and not accruing, loans modified in a troubled debt restructuring (TDR), and other loans if there is specific information of a collateral shortfall are individually evaluated for impairment. Impairment is measured by determining the present value of expected future cash flows or, for collateral-dependent loans, the fair value of the collateral less estimated selling costs. (7) Loans Receivable and Allowance for Loan Losses (continued) The following table summarizes loans receivable (including PCI loans) and allowance for loan losses by portfolio segment and impairment method at December 31, 2019 and 2018 : December 31, 2019 One-to-Four Family Multifamily and Commercial Construction Commercial Business Home Equity Loans and Advances Other Consumer Loans Unallocated Total (In thousands) Allowance for loan losses: Individually evaluated for impairment $ 484 $ 2 $ — $ 1,121 $ 14 $ — $ — $ 1,621 Collectively evaluated for impairment 13,296 22,978 7,435 14,715 1,655 9 — 60,088 Loans acquired with deteriorated credit quality — — — — — — — — Total $ 13,780 $ 22,980 $ 7,435 $ 15,836 $ 1,669 $ 9 $ — $ 61,709 Total loans: Individually evaluated for impairment $ 8,891 $ 2,599 $ — $ 5,178 $ 2,143 $ — $ — $ 18,811 Collectively evaluated for impairment 2,068,188 2,917,386 298,942 478,037 385,984 1,960 — 6,150,497 Loans acquired with deteriorated credit quality 429 4,866 — 1,726 — — — 7,021 Total gross loans $ 2,077,508 $ 2,924,851 $ 298,942 $ 484,941 $ 388,127 $ 1,960 $ — $ 6,176,329 (7) Loans Receivable and Allowance for Loan Losses (continued) December 31, 2018 One-to-Four Family Multifamily and Commercial Construction Commercial Business Home Equity Loans and Advances Other Consumer Loans Unallocated Total (In thousands) Allowance for loan losses: Individually evaluated for impairment $ 537 $ — $ — $ 366 $ 12 $ — $ — $ 915 Collectively evaluated for impairment 14,695 23,251 7,217 13,810 2,446 8 — 61,427 Total $ 15,232 $ 23,251 $ 7,217 $ 14,176 $ 2,458 $ 8 $ — $ 62,342 Total loans: Individually evaluated for impairment $ 9,048 $ 2,695 $ — $ 2,944 $ 3,100 $ — $ — $ 17,787 Collectively evaluated for impairment 1,821,138 2,139,459 261,473 330,932 390,392 1,108 — 4,944,502 Total gross loans $ 1,830,186 $ 2,142,154 $ 261,473 $ 333,876 $ 393,492 $ 1,108 $ — $ 4,962,289 Loan modifications to borrowers experiencing financial difficulties that are considered troubled debt restructurings ("TDRs") primarily involve the lowering of the monthly payments on such loans through either a reduction in interest rate below a market rate, an extension of the term of the loan without a corresponding adjustment to the risk premium reflected in the interest rate, or a combination of these two methods. These modifications generally do not result in the forgiveness of principal or accrued interest. In addition, the Company attempts to obtain additional collateral or guarantor support when modifying such loans. Non-accruing restructured loans may be returned to accrual status when there has been a sustained period of repayment performance (generally six consecutive months of payments) and both principal and interest are deemed collectible. (7) Loans Receivable and Allowance for Loan Losses (continued) The following table presents the number of loans modified as TDRs for the years ended December 31, 2019 and 2018 , and September 30, 2017, along with their balances immediately prior to the modification date and post-modification. Post-modification recorded investment represents the net book balance immediately following modification. There we no loans modified during the three months ended December 31, 2017, For the Years Ended December 31, 2019 2018 No. of Loans Pre-modification Recorded Investment Post-modification Recorded Investment No. of Loans Pre-modification Recorded Investment Post-modification Recorded Investment (In thousands) Troubled Debt Restructurings Real estate loans: One-to-four family — $ — $ — 5 $ 801 $ 801 Multifamily and commercial — — — 1 65 65 Commercial business loans 1 4,095 4,095 — — — Consumer loans: Home equity loans and advances — — — 1 588 588 Total restructured loans 1 $ 4,095 $ 4,095 7 $ 1,454 $ 1,454 For the Year Ended September 30, 2017 No. of Loans Pre-modification Recorded Investment Post-modification Recorded Investment (Dollars in thousands) Troubled Debt Restructurings Real estate loans: One-to-four family 3 $ 548 $ 548 Multifamily and commercial 1 3,964 3,964 Commercial business loans 1 18 18 Consumer loans: Home equity loans and advances 2 248 248 Total restructured loans 7 $ 4,778 $ 4,778 (7) Loans Receivable and Allowance for Loan Losses (continued) The activity in the allowance for loan losses for the years ended December 31, 2019 and 2018 , September 30, 2017, and the three months ended December 31, 2017 are as follows: Years Ended December 31, Three Months Ended December 31, Year Ended September 30, 2019 2018 2017 2017 (In thousands) Balance at beginning of period $ 62,342 $ 58,178 $ 54,633 $ 51,867 Provision charged 4,224 6,677 3,400 6,426 Recoveries 496 707 188 584 Charge-offs (5,353 ) (3,220 ) (43 ) (4,244 ) Balance at end of period $ 61,709 $ 62,342 $ 58,178 $ 54,633 The activity in the allowance for loan losses by portfolio segment for the years ended December 31, 2019 and 2018 , September 30, 2017, and the three months ended December 31, 2017 are as follows: For the Year Ended December 31, 2019 One-to-Four Family Multifamily and Commercial Construction Commercial Business Home Equity Loans and Advances Other Consumer Loans Unallocated Total (In thousands) Balance at beginning of period $ 15,232 $ 23,251 $ 7,217 $ 14,176 $ 2,458 $ 8 $ — $ 62,342 Provision charged (credited) (429 ) (178 ) 216 5,250 (638 ) 3 — 4,224 Recoveries 30 10 2 404 50 — — 496 Charge-offs (1,053 ) (103 ) — (3,994 ) (201 ) (2 ) — (5,353 ) Balance at end of period $ 13,780 $ 22,980 $ 7,435 $ 15,836 $ 1,669 $ 9 $ — $ 61,709 For the Year Ended December 31, 2018 One-to-Four Family Multifamily and Commercial Construction Commercial Business Home Equity Loans and Advances Other Consumer Loans Unallocated Total (In thousands) Balance at beginning of period $ 19,991 $ 19,933 $ 5,217 $ 8,275 $ 4,576 $ 8 $ 178 $ 58,178 Provision charged (credited) (4,503 ) 3,445 1,997 7,860 (1,949 ) 5 (178 ) 6,677 Recoveries 334 2 3 240 122 6 — 707 Charge-offs (590 ) (129 ) — (2,199 ) (291 ) (11 ) — (3,220 ) Balance at end of period $ 15,232 $ 23,251 $ 7,217 $ 14,176 $ 2,458 $ 8 $ — $ 62,342 (7) Loans Receivable and Allowance for Loan Losses (continued) For the Three Months Ended December 31, 2017 One-to-Four Family Multifamily and Commercial Construction Commercial Business Home Equity Loans and Advances Other Consumer Loans Unallocated Total (In thousands) Balance at beginning of period $ 18,533 $ 18,029 $ 5,299 $ 8,480 $ 4,190 $ 8 $ 94 $ 54,633 Provision charged (credited) 1,473 1,906 (82 ) (373 ) 389 3 84 3,400 Recoveries 9 — — 171 6 2 — 188 Charge-offs (24 ) (2 ) — (3 ) (9 ) (5 ) — (43 ) Balance at end of period $ 19,991 $ 19,933 $ 5,217 $ 8,275 $ 4,576 $ 8 $ 178 $ 58,178 For the Year Ended September 30, 2017 One-to-Four Family Multifamily and Commercial Construction Commercial Business Home Equity Loans and Advances Other Consumer Loans Unallocated Total (In thousands) Balance at beginning of period $ 18,638 $ 17,390 $ 5,960 $ 5,721 $ 4,052 $ 11 $ 95 $ 51,867 Provision charged (credited) 1,029 1,644 (661 ) 3,183 1,219 13 (1 ) 6,426 Recoveries 268 75 — 182 59 — — 584 Charge-offs (1,402 ) (1,080 ) — (606 ) (1,140 ) (16 ) — (4,244 ) Balance at end of period $ 18,533 $ 18,029 $ 5,299 $ 8,480 $ 4,190 $ 8 $ 94 $ 54,633 (7) Loans Receivable and Allowance for Loan Losses (continued) The following tables present loans individually evaluated for impairment by loan segment, excluding PCI loans: At December 31, 2019 Recorded Investment Unpaid Principal Balance Specific Allowance (In thousands) With no allowance recorded: Real estate loans: One-to-four family $ 4,314 $ 5,473 $ — Multifamily and commercial 1,494 2,191 — Commercial business loans 3,859 4,048 — Consumer loans: Home equity loans and advances 1,080 1,217 — 10,747 12,929 — With a specific allowance recorded: Real estate loans: One-to-four family 4,577 4,613 484 Multifamily and commercial 1,105 1,105 2 Commercial business loans 1,319 4,307 1,121 Consumer loans: Home equity loans and advances 1,063 1,063 14 8,064 11,088 1,621 Total: Real estate loans: One-to-four family 8,891 10,086 484 Multifamily and commercial 2,599 3,296 2 Commercial business loans 5,178 8,355 1,121 Consumer loans: Home equity loans and advances 2,143 2,280 14 Total loans $ 18,811 $ 24,017 $ 1,621 (7) Loans Receivable and Allowance for Loan Losses (continued) At December 31, 2018 Recorded Investment Unpaid Principal Balance Specific Allowance (In thousands) With no allowance recorded: Real estate loans: One-to-four family $ 4,156 $ 5,307 $ — Multifamily and commercial 2,695 3,482 — Commercial business loans 2,285 2,374 — Consumer loans: Home equity loans and advances 2,511 2,866 — 11,647 14,029 — With a specific allowance recorded: Real estate loans: One-to-four family 4,892 4,939 537 Commercial business loans 659 768 366 Consumer loans: Home equity loans and advances 589 589 12 6,140 6,296 915 Total: Real estate loans: One-to-four family 9,048 10,246 537 Multifamily and commercial 2,695 3,482 — Commercial business loans 2,944 3,142 366 Consumer loans: Home equity loans and advances 3,100 3,455 12 Total loans $ 17,787 $ 20,325 $ 915 Specific allocations of the allowance for loan losses attributable to impaired loans totaled $1.6 million and $915,000 at December 31, 2019 and 2018 , respectively. At December 31, 2019 and 2018 , impaired loans for which there was no related allowance for loan losses totaled $10.7 million and $11.6 million , respectively. (7) Loans Receivable and Allowance for Loan Losses (continued) The following tables present interest income recognized for loans individually evaluated for impairment, by loan segment, excluding PCI loans for the years ended December 31, 2019 and 2018 , September 30, 2017, and the three months ended December 31, 2017: For the Years Ended December 31, 2019 2018 Average Recorded Investment Interest Income Recognized Average Recorded Investment Interest Income Recognized (In thousands) Real estate loans: One-to-four family $ 8,811 $ 434 $ 10,224 $ 445 Multifamily and commercial 2,639 147 2,712 155 Construction 850 — — — Commercial business loans 6,378 479 3,060 118 Consumer loans: Home equity loans and advances 2,562 143 3,361 173 Totals $ 21,240 $ 1,203 $ 19,357 $ 891 For the Three Months Ended December 31, For the Year Ended September 30, 2017 2017 Average Recorded Investment Interest Income Recognized Average Recorded Investment Interest Income Recognized (In thousands) Real estate loans: One-to-four family $ 14,015 $ 110 $ 15,027 $ 469 Multifamily and commercial 4,087 39 4,328 279 Commercial business loans 3,870 46 3,796 195 Consumer loans: Home equity loans and advances 3,618 35 3,903 136 Totals $ 25,590 $ 230 $ 27,054 $ 1,079 The recorded investment in TDRs totaled $20.0 million at December 31, 2019 , of which no loans were over 90 days past due, and three loans totaling $660,000 were 30-59 days past due. The remaining loans modified were current at the time of restructuring and have complied with the terms of their restructure agreement at December 31, 2019 . The recorded investment in TDRs totaled $16.0 million at December 31, 2018 , of which one loan totaling $101,000 was over 90 days past due, and seven loans totaling $1.0 million were 30-59 days past due. The remaining loans modified were current at the time of restructuring and have complied with the terms of their restructure agreement at December 31, 2018 . The recorded investment in TDRs totaled $17.6 million at December 31, 2017, of which two loans totaling $425,000 were over 90 days past due. The remaining loans modified were current at the time of restructuring and have complied with the terms of their restructure agreement at December 31, 2017. The recorded investment in TDRs totaled $21.1 million at September 30, 2017, of which seven loans totaling $1.0 million were over 90 days past due. The remaining loans modified were current at the time of restructuring and have complied with the terms of their restructure agreement at September 30, 2017. (7) Loans Receivable and Allowance for Loan Losses (continued) The following tables present loans receivable by credit quality risk indicator and by loan segment, excluding PCI loans at December 31, 2019 and 2018 : December 31, 2019 One-to-Four Family Multifamily and Commercial Construction Commercial Business Home Equity Loans and Advances Other Consumer Loans Total (In thousands) Pass $ 2,072,878 $ 2,900,286 $ 298,942 $ 454,183 $ 387,251 $ 1,960 $ 6,115,500 Special mention 419 4,724 — 20,170 — — 25,313 Substandard 3,782 14,975 — 8,862 876 — 28,495 Doubtful — — — — — — — Total $ 2,077,079 $ 2,919,985 $ 298,942 $ 483,215 $ 388,127 $ 1,960 $ 6,169,308 December 31, 2018 One-to-Four Family Multifamily and Commercial Construction Commercial Business Home Equity Loans and Advances Other Consumer Loans Total (In thousands) Pass $ 1,826,066 $ 2,128,680 $ 261,473 $ 320,451 $ 392,092 $ 1,108 $ 4,929,870 Special mention — — — 9,074 — — 9,074 Substandard 4,120 13,474 — 4,351 1,400 — 23,345 Doubtful — — — — — — — Total $ 1,830,186 $ 2,142,154 $ 261,473 $ 333,876 $ 393,492 $ 1,108 $ 4,962,289

Office Properties and Equipment

Office Properties and Equipment, net	12 Months Ended
Office Properties and Equipment, net	Dec. 31, 2019
Property, Plant and Equipment [Abstract]
Office Properties and Equipment, net	Office Properties and Equipment, net Office properties and equipment less accumulated depreciation at December 31, 2019 and 2018 are summarized as follows: December 31, 2019 2018 (In thousands) Land $ 11,069 $ 7,829 Buildings 27,340 24,018 Land and building improvements 31,520 24,864 Leasehold improvements 24,038 21,279 Furniture and equipment 36,828 28,538 130,795 106,528 Less accumulated depreciation and amortization 57,828 54,478 Total office properties and equipment, net $ 72,967 $ 52,050 (8) Office Properties and Equipment, net (continued) Land and building improvements at December 31, 2019 and 2018 included $1.3 million and $8.9 million , respectively, in construction in progress for the renovation of the Bank's corporate headquarters and various other facilities, and at December 31, 2019 also included $1.8 million of properties acquired from Stewardship that were held-for-sale, and carried at fair value. Depreciation and amortization expense for the years ended December 31, 2019 and 2018 , September 30, 2017 and the three months ended December 31, 2017 , amounted to $4.9 million , $3.8 million , $3.4 million , and $863,000

Goodwill and Intangible Assets

Goodwill and Intangible Assets	12 Months Ended
Goodwill and Intangible Assets	Dec. 31, 2019
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill and Intangible Assets	Goodwill and Intangible Assets Intangible assets at December 31, 2019 and 2018 are summarized as follows: December 31, 2019 2018 (In thousands) Goodwill $ 60,763 $ 5,716 Core deposit intangibles 7,245 — Mortgage servicing rights 574 369 $ 68,582 $ 6,085 Mortgage servicing rights' amortization expense for the years ended December 31, 2019 and 2018 , September 30, 2017, and the three months ended December 31, 2017 amounted to $109,000 , $73,000 , $105,000 , and $22,000 respectively. Core deposit intangible amortization expense for the year ended December 31, 2019 amounted to $222,000 . There was no core deposit amortization expense for the years ended December 31, 2018, September 30, 2017 or the three months ended December 31, 2017. Scheduled amortization of core deposit intangibles for each of the next five years and thereafter is as follows: Year Ending December 31, Core Deposit Intangible Amortization (In thousands) 2020 $ 1,048 2021 1,024 2022 961 2023 892 2024 819 Thereafter 2,501

Deposits

Deposits	12 Months Ended
Deposits	Dec. 31, 2019
Banking and Thrift [Abstract]
Deposits	Deposits Deposits at December 31, 2019 and 2018 are summarized as follows: December 31, 2019 2018 Balance Weighted Average Rate Balance Weighted Average Rate (Dollars in thousands) Non-interest-bearing demand $ 958,442 — % $ 723,794 — % Interest-bearing demand 1,720,383 1.03 1,219,381 0.95 Money market accounts 410,392 0.91 259,694 0.67 Savings and club deposits 543,480 0.15 510,688 0.16 Certificates of deposit 2,013,145 2.25 1,700,316 2.01 Total deposits $ 5,645,842 1.20 % $ 4,413,873 1.09 % Included in the above balance at December 31, 2019 are certificates of deposit obtained through brokers, of $31.6 million , that were acquired from Stewardship. The aggregate amount of certificates of deposit that meet or exceed $100,000 totaled approximately $1.1 billion and $885.3 million at December 31, 2019 and 2018 , respectively. Scheduled maturities of certificates of deposit accounts at December 31, 2019 and 2018 are summarized as follows: December 31, 2019 2018 (In thousands) One year or less $ 1,293,613 $ 1,107,667 After one year to two years 548,995 326,800 After two years to three years 142,458 230,468 After three years to four years 11,362 24,939 After four years 16,717 10,442 $ 2,013,145 $ 1,700,316 Interest expense on deposits for the years ended December 31, 2019 and 2018 , September 30, 2017, and the three months ended December 31, 2017 are summarized as follows: Years Ended December 31, Three Months Ended December 31, Year Ended September 30, 2019 2018 2017 2017 (In thousands) Demand (including money market accounts) $ 19,922 $ 12,933 $ 2,509 $ 8,556 Savings and club deposits 770 993 210 630 Certificates of deposit 40,859 25,597 4,912 16,395 $ 61,551 $ 39,523 $ 7,631 $ 25,581

Borrowings

Borrowings	12 Months Ended
Borrowings	Dec. 31, 2019
Debt Disclosure [Abstract]
Borrowings	Borrowings Borrowings at December 31, 2019 and 2018 are summarized as follows: December 31, 2019 2018 2019 2018 Balance Weighted Average Interest Rate (In thousands) Overnight lines of credit $ 107,800 $ 159,600 1.81 % 2.60 % Federal Home Loan Bank advances 1,275,391 1,029,580 2.09 2.40 Subordinated notes 16,899 — 6.75 — Junior subordinated debentures 6,932 — 5.09 — $ 1,407,022 $ 1,189,180 2.14 % 2.43 % At December 31, 2019 and 2018 , the Company had outstanding overnight lines of credit with the FHLB of $107.8 million and $159.6 million , respectively. Interest expense on the overnight advances for the years ended December 31, 2019 and 2018 , September 30, 2017, and the three months ended December 31, 2017 , were $1.8 million , $2.2 million , $233,000 , and $70,000 respectively. At December 31, 2019 , the Bank could borrow funds from the FHLB under an overnight advance program up to the Bank's maximum borrowing capacity based on its ability to collateralize such borrowings. Members in good standing can borrow up to 50% of their asset size as long as they have qualifying collateral to support the advance and purchase of FHLB capital. Additionally, at both December 31, 2019 and 2018 , the Bank had unused correspondent bank lines of credit with an aggregate overnight borrowing capacity of $250.0 million and $225.0 million , respectively. At December 31, 2019 FHLB advances were at fixed rates with maturities between January 2020 and August 2024, and at December 31, 2018 , FHLB advances were at fixed rates with maturities between January 2019 and December 2022. At December 31, 2019 and 2018 , FHLB advances were collateralized by FHLB capital stock owned by the Bank, loans with carrying values totaling $1.9 billion and $1.7 billion , respectively. Loans securing advances consists of one-to-four family, multifamily, commercial and home equity real estate loans. At December 31, 2019, FHLB advances were also collateralized by securities with carrying values totaling $246.2 million . Interest expense on fixed rate FHLB advances for the years ended December 31, 2019 and 2018, September 30, 2017, and the three months ended December 31, 2017 were $25.2 million , $17.1 million , $12.8 million , and $3.3 million respectively. At December 31, 2019 and 2018 , short-term FHLB advances totaling $410.0 million and $320.0 million , respectively, were designated as hedged items as part of a cash flow hedging program. See note 21 for information regarding these transactions. Scheduled maturities of FHLB advances including lines of credit at December 31, 2019 are summarized as follows: Year Ended December 31, 2019 (In thousands) One year or less $ 1,004,139 After one year to two years 178,723 After two years to three years 169,800 After three years to four years 20,529 After four years 10,000 Total FHLB advances $ 1,383,191 (11) Borrowings (continued) At December 31, 2019 and 2018 , the carrying value of junior subordinated debt balances were $6.9 million and $0 , respectively. The balance outstanding at December 31, 2019 represents debentures issued in 2003 by Stewardship Statutory Trust (the "Trust"), a statutory business trust that was acquired in the Stewardship merger. These floating rate debentures mature on September 17, 2033 and adjust quarterly at a rate of three month LIBOR plus 2.95% . At December 31, 2019 the rate was 5.09% . In August 2018, the Company redeemed all other junior subordinated debt securities that were previously outstanding. Interest expense for the years ended December 31, 2019 and 2018 , September 31, 2017, and the three months ended December 31, 2017 were $113,000 , $3.5 million , $4.2 million and $1.0 million , respectively. At December 31, 2019 and 2018 , the balance of subordinated notes were $16.9 million and $0 , respectively. The Company acquired these subordinated notes in the Stewardship merger. These notes mature on August 25, 2025 and bear interest at a fixed rate of 6.75% . The subordinated notes include a right of prepayment, without penalty, on or after August 28, 2020. Interest expense for the year ended December 31, 2019 was $65,000 . There were no subordinated notes outstanding at or during the years ended December 31, 2018, September 30, 2017 or the three months ended December 31, 2017. Interest expense on securities sold under agreements to repurchase for the years ended December 31, 2019 and 2018 , September 30, 2017, and the three months ended December 31, 2017 were $0 , $3,000 , $1.6 million , and $203,000

Stockholders' Equity

Stockholders' Equity	12 Months Ended
Stockholders' Equity	Dec. 31, 2019
Banking and Thrift [Abstract]
Stockholders' Equity	Stockholders' Equity Regulatory Capital The Company and its subsidiary Bank are subject to various regulatory capital requirements administered by the federal banking regulators, including a risk-based capital measure. The Federal Reserve establishes capital requirements, including well capitalized standards, for the consolidated financial holding company, and the Office of the Comptroller of the Currency (the "OCC") has similar requirements for the Company's subsidiary bank. Failure to meet minimum capital requirements can initiate certain mandatory and possibly additional discretionary actions by regulators that, if undertaken, could have a direct material effect on the Company's Consolidated Statements of Financial Condition. Federal regulators require federally insured depository institutions to meet several minimum capital standards: (1) total capital to risk-weighted assets of 8.0% ; (2) tier 1 capital to risk-weighted assets of 6.0% ; (3) common equity tier 1 capital to risk-weighted assets of 4.5% ; and (4) tier 1 capital to adjusted total assets of 4.0% . In addition to establishing the minimum regulatory capital requirements, the regulations limit capital distributions and certain discretionary bonus payments to management if the institution does not hold a "capital conservation buffer" consisting of 2.5% of common equity tier 1 capital to risk-weighted assets above the amount necessary to meet its minimum risk-based capital requirements. The capital conservation buffer capital requirement was fully phased on January 1, 2019. The regulators established a framework for the classification of savings institutions into five categories: well capitalized, adequately capitalized, undercapitalized, significantly undercapitalized, and critically undercapitalized. Generally, an institution is considered well capitalized if it has: a total capital to risk-weighted assets ratio of at least 10.0% , a tier 1 capital to risk-weighted assets ratio of at least 8.0% , a common tier 1 capital to risk-weighted assets ratio of at least 6.5% , and a tier 1 capital to adjusted total assets ratio of at least 5.0% . As of December 31, 2019 and 2018 , each of the Company and the Bank exceeded all capital adequacy requirements to which it is subject. Based upon most recent notification from federal banking regulators, the Bank was categorized as well capitalized as of September 30, 2019, under the regulatory framework for prompt corrective action. There are no conditions existing or events which have occurred since notification that management believes have changed the Bank's category. The following table presents the Company's and the Bank's actual capital amounts and ratios as of December 31, 2019 and 2018 compared to the Federal Reserve Bank minimum capital adequacy requirements and the Federal Reserve Bank requirements for classification as a well-capitalized institution: (12) Stockholders' Equity (continued) Regulatory Capital (continued) Actual Minimum Capital Adequacy Requirements Minimum Capital Adequacy Requirements With Capital Conservation Buffer To Be Well Capitalized Under Prompt Corrective Action Provisions Amount Ratio Amount Ratio Amount Ratio Amount Ratio Company (In thousands, except ratio data) At December 31, 2019: Total capital (to risk-weighted assets) $ 1,061,555 17.25 % $ 492,438 8.00 % $ 646,324 10.50 % N/A N/A Tier 1 capital (to risk-weighted assets) 988,172 16.05 369,328 6.00 523,215 8.50 N/A N/A Common equity tier 1 capital (to risk-weighted assets) 980,995 15.94 276,996 4.50 430,883 7.00 N/A N/A Tier 1 capital (to adjusted total assets) 988,172 12.92 305,824 4.00 305,824 4.00 N/A N/A At December 31, 2018: Total capital (to risk-weighted assets) $ 1,094,062 23.45 % $ 373,276 8.00 % $ 460,763 9.88 % N/A N/A Tier 1 capital (to risk-weighted assets) 1,035,477 22.19 279,957 6.00 367,444 7.88 N/A N/A Common equity tier 1 capital (to risk-weighted assets) 1,035,477 22.19 209,968 4.50 297,455 6.38 N/A N/A Tier 1 capital (to adjusted total assets) 1,035,477 15.75 263,037 4.00 263,037 4.00 N/A N/A Bank At December 31, 2019: Total capital (to risk-weighted assets) $ 844,664 14.25 % $ 474,125 8.00 % $ 622,290 10.50 % $ 592,657 10.00 % Tier 1 capital (to risk-weighted assets) 782,881 13.21 355,594 6.00 503,758 8.50 474,125 8.00 Common equity tier 1 capital (to risk-weighted assets) 782,881 13.21 266,696 4.50 414,860 7.00 385,227 6.50 Tier 1 capital (to adjusted total assets) 782,881 10.25 305,423 4.00 305,423 4.00 381,779 5.00 At December 31, 2018: Total capital (to risk-weighted assets) $ 886,728 19.04 % $ 372,550 8.00 % $ 459,866 9.88 % $ 465,687 10.00 % Tier 1 capital (to risk-weighted assets) 828,257 17.79 279,412 6.00 366,729 7.88 372,550 8.00 Common equity tier 1 capital (to risk-weighted assets) 828,257 17.79 209,559 4.50 296,875 6.38 302,697 6.50 Tier 1 capital (to adjusted total assets) 828,257 12.60 263,025 4.00 263,025 4.00 382,006 5.00 (12) Stockholders' Equity (continued) Regulatory Capital (continued) As a result of the recently enacted Economic Growth, Regulatory Relief, and Consumer Protection Act, the federal banking agencies developed a "Community Bank Leverage Ratio" (the ratio of a bank's Tier 1 equity capital to average total consolidated assets) for financial institutions with less than $10 billion. A "qualifying community bank" with capital exceeding 9% will be considered compliant with all applicable regulatory capital and leverage requirements, including the capital requirements to be considered "well capitalized' under Prompt Corrective Action statutes. The rule has been adopted in final form and the framework, if elected, will first be available for use in the Bank's March 31, 2020 Call Report. Stock Repurchase Program On June 11, 2019, the Company announced that its Board of Directors authorized the Company's first stock repurchase program since the completion of its minority public offering in April 2018. This program, which commenced on June 13, 2019, authorized the purchase of up to 4,000,000 shares, or approximately 3.5% , of the Company's then issued and outstanding common stock. On December 5, 2019, the Company announced that the Board of Directors authorized expanding its stock repurchase program to acquire an additional 3,000,000 shares of the Company's outstanding common stock. During the year ended December 31, 2019, the Company repurchased 3,543,800 shares at a cost of approximately $55.3 million , or $15.61 per share under this program. Repurchased shares are held as treasury stock and are available for general corporate purposes. There were no stock repurchase programs in effect at or during the year ended December 31, 2018.

Employee Benefit Plans

Employee Benefit Plans	12 Months Ended
Employee Benefit Plans	Dec. 31, 2019
Retirement Benefits [Abstract]
Employee Benefit Plans	Employee Benefit Plans Pension Plan, Retirement Income Maintenance Plan (the "RIM Plan") and Post-retirement Plan The Company maintains a single employer, tax-qualified defined benefit pension plan (the "Pension Plan") which covers full-time employees that satisfy the plan eligibility requirements. The benefits are based on years of service and the employee's compensation during the last five years of employment. Effective October 1, 2018, employees hired by the Bank are not eligible to participate in the Bank's pension plan as the plan has been closed to new employees as of that date, and effective January 1, 2019, the Post-retirement Plan has also been closed to new hires. The Company's policy is to fund at least the minimum contribution required by the Employee Retirement Income Security Act of 1974. GAAP requires an employer to: (a) recognize in its statement of financial position the over-funded or under-funded status of a defined benefit post-retirement plan measured as the difference between the fair value of plan assets and the benefit obligation; (b) measure a plan’s assets and its obligations that determine its funded status at the end of the employer’s fiscal year (with limited exceptions); and (c) recognize as a component of other comprehensive income (loss), net of tax, the actuarial gains and losses and the prior service costs and credits that arise during the period. The assets of the plan are primarily invested in fixed income and equity funds. The Company also has a RIM Plan, which is a non-qualified defined benefit plan which provides benefits to all employees of the Company if their benefits under the Pension Plan are limited by Internal Revenue Code 415 and 401(a)(17). In addition, the Company provides certain health care and life insurance benefits to eligible retired employees under a Post-retirement Plan. The Company accrues the cost of retiree health care and other benefits during the employees’ period of active service. The following table sets forth information regarding the Pension, RIM and Post-retirement Plans at December 31, 2019 and 2018 : December 31, 2019 2018 2019 2018 2019 2018 Pension RIM Post-retirement (In thousands) Change in benefit obligation: Benefit obligation at beginning of year $ 209,205 $ 229,156 $ 11,285 $ 12,243 $ 20,964 $ 22,078 Service cost 6,494 7,805 210 282 339 417 Interest cost 8,569 8,489 466 443 826 796 Actuarial (gain) loss 46,001 (30,703 ) 2,074 (1,355 ) 3,141 (1,845 ) Benefits paid (6,443 ) (5,542 ) (339 ) (328 ) (667 ) (482 ) Benefit obligation at end of year 263,826 209,205 13,696 11,285 24,603 20,964 Change in plan assets: Fair value of plan assets at beginning of year 272,974 289,390 — — — — Actuarial return on plan assets 54,816 (10,874 ) — — — — Employer contributions 35,000 — 339 328 667 482 Benefits paid (6,443 ) (5,542 ) (339 ) (328 ) (667 ) (482 ) Fair value of plan assets at end of year 356,347 272,974 — — — — Funded status at end of year $ 92,521 $ 63,769 $ (13,696 ) $ (11,285 ) $ (24,603 ) $ (20,964 ) (13) Employee Benefit Plans (continued) Pension Plan, Retirement Income Maintenance Plan (the "RIM Plan") and Post-retirement Plan (cont'd) At December 31, 2019 and 2018 , the unfunded liability for the RIM and Post-retirement Plans of $13.7 million and $24.6 million , and $11.3 million and $21.0 million , respectively, were included in other liabilities in the Consolidated Statements of Financial Condition, and the over-funded pension benefits associated with the Pension Plan totaling $92.5 million and $63.8 million respectively, were included in other assets. The components of accumulated other comprehensive income related to the Pension, RIM, and Post-retirement Plans on a pre-tax basis, at December 31, 2019 , 2018 , and 2017, and September 30, 2017 are summarized in the following table: At December 31, 2019 2018 Pension RIM Post-retirement Pension RIM Post-retirement (In thousands) Unrecognized prior service costs $ — $ — $ — $ — $ — $ — Unrecognized net actuarial income 68,752 5,577 7,221 59,579 3,748 4,226 Total accumulated other comprehensive income $ 68,752 $ 5,577 $ 7,221 $ 59,579 $ 3,748 $ 4,226 At December 31 At September 30, 2017 2017 Pension RIM Post-retirement Pension RIM Post-retirement (In thousands) Unrecognized prior service costs $ — $ — $ (106 ) $ — $ — $ (140 ) Unrecognized net actuarial income 61,731 5,515 6,395 55,438 4,725 4,611 Total accumulated other comprehensive income $ 61,731 $ 5,515 $ 6,289 $ 55,438 $ 4,725 $ 4,471 Net periodic benefit (income) cost for Pension Plan, RIM and Post-retirement Plan and split dollar life insurance arrangement plan benefits for the years ended December 31, 2019 and 2018 , September 30, 2017 and the three months ended December 31, 2017 , includes the following components: (13) Employee Benefit Plans (continued) Pension Plan, Retirement Income Maintenance Plan (the "RIM Plan") and Post-retirement Plan (cont'd) For the Years Ended December 31, 2019 2018 Pension RIM Post-retirement Pension RIM Post-retirement Affected Line Item in the Consolidated Statements of Income (In thousands) Service cost $ 6,494 $ 210 $ 339 $ 7,805 $ 282 $ 417 Compensation and employee benefits Interest cost 8,569 466 826 8,489 443 796 Other non-interest expense Expected return on plan assets (21,058 ) — — (20,794 ) — — Other non-interest expense Amortization: Prior service cost — — — — — (106 ) Other non-interest expense Net loss 3,070 244 147 3,117 413 323 Other non-interest expense Net periodic (income) benefit cost $ (2,925 ) $ 920 $ 1,312 $ (1,383 ) $ 1,138 $ 1,430 For the Three Months Ended December 31, For the Year Ended September 30, 2017 2017 Pension RIM Post-retirement Pension RIM Post-retirement (In thousands) Service cost $ 1,780 $ 60 $ 92 $ 7,621 $ 237 $ 471 Interest cost 2,128 111 205 8,444 429 742 Expected return on plan assets (4,814 ) — — (24,809 ) — — Amortization: Prior service cost — — (34 ) — — (136 ) Net loss 707 103 70 10,998 453 325 Net periodic (income) benefit cost $ (199 ) $ 274 $ 333 $ 2,254 $ 1,119 $ 1,402 (13) Employee Benefit Plans (continued) Pension Plan, Retirement Income Maintenance Plan (the "RIM Plan") and Post-retirement Plan (cont'd) The following table summarizes the impact of retrospective application of ASU 2017-07 to the Consolidated Statements of Income for the year ended December 31, 2018: Year Ended December 31, 2018 (In thousands) Compensation and employee benefits: As previously reported $ 69,907 As reported under ASU 2017-07 77,226 Other non-interest expense: As previously reported $ 12,916 As reported under ASU 2017-07 5,597 The weighted average actuarial assumptions used in the plan determinations at and for the years ended December 31, 2019 and 2018 , September 30, 2017 and the three months ended December 31, 2017 were as follows: At and For the Years Ended December 31, 2019 2018 Pension RIM Post-retirement Pension RIM Post-retirement Weighted average assumptions used to determine benefit obligation: Discount rate 3.490 % 3.330 % 3.270 % 4.570 % 4.470 % 4.410 % Rate of compensation increase 3.500 3.500 N/A 3.500 3.500 N/A Weighted average assumptions used to determine net periodic benefit cost: Discount rate 4.570 % 4.470 % 4.410 % 3.750 % 3.625 % 3.625 % Discount rate-remeasurement 3.850 N/A N/A N/A N/A N/A Expected rate of return on plan assets 7.000 N/A N/A 7.250 % N/A N/A Rate of compensation increase 3.500 3.500 N/A 3.500 3.500 N/A At and For the Three Months Ended December 31, At and for the Year Ended September 30, 2017 2017 Pension RIM Post-retirement Pension RIM Post-retirement Weighted average assumptions used to determine benefit obligation: Discount rate 3.750 % 3.625 % 3.625 % 4.000 % 3.875 % 3.875 % Rate of compensation increase 3.500 3.500 N/A 3.500 3.500 N/A Weighted average assumptions used to determine net periodic benefit cost: Discount rate 4.000 % 3.875 % 3.875 % 3.875 % 3.625 % 3.625 % Expected rate of return on plan assets 7.250 N/A N/A 7.500 N/A N/A Rate of compensation increase 3.500 3.500 N/A 3.500 3.500 N/A (13) Employee Benefit Plans (continued) Pension Plan, Retirement Income Maintenance Plan (the "RIM Plan") and Post-retirement Plan (cont'd) The Company provides its actuaries with certain rate assumptions used in measuring the respective benefit obligations. The most significant of these is the discount rate used to calculate the period-end present value of the benefit obligations, and the expense to be included in the following year's financial statements. A lower discount rate will result in a higher benefit obligation and expense, while a higher discount rate will result in a lower benefit obligation and expense. The discount rate assumption was determined based on a cash flow-yield curve model specific to the Company's pension and post-retirement plans. The Company compares this rate to certain market indices, such as long-term treasury bonds, or pension liability indices, for reasonableness. The Company's expected return on plan assets assumption is based on historical investment return rate experience and evaluation of input from the trustee managing the pension plan's assets and the Bank's Pension Committee which has responsibility for managing these assets. The expected return on pension plan assets is also impacted by the target allocation of assets, which is based on the Company's goal of earning the highest rate of return while maintaining risk at acceptable levels. Assumed health care cost trend rates have a significant effect on the amounts reported for health care plans. A 1% change in the assumed health care cost trend rate would have the following effects on post-retirement benefits at December 31, 2019 : 1% increase 1% decrease (In thousands) Effect on total service cost and interest cost $ 14 $ (12 ) Effect on post-retirement benefit obligations 162 (141 ) Estimated future benefit payments, which reflect expected future service, as appropriate for the next five years and thereafter are as follows: Pension RIM Post-retirement (In thousands) 2020 $ 6,675 $ 361 $ 1,246 2021 7,209 379 1,293 2022 7,760 417 1,337 2023 8,412 457 1,351 2024 9,112 521 1,346 2025 - 2029 57,274 3,605 7,270 The weighted average asset allocation of pension assets at December 31, 2019 and 2018 were as follows: December 31, 2019 2018 Domestic equities 39.60 % 35.20 % Foreign equities 9.60 10.80 Fixed income 44.30 42.30 Real estate 6.10 10.50 Cash 0.40 1.20 Total 100.00 % 100.00 % (13) Employee Benefit Plans (continued) Pension Plan, Retirement Income Maintenance Plan (the "RIM Plan") and Post-retirement Plan (cont'd) Management, under the direction of the Pension Committee, strives to have pension assets sufficiently diversified so that adverse or unexpected results from one security class will not have a significant detrimental impact on the entire portfolio. The target allocation of assets and acceptable ranges around the targets are as follows: Allowable Range Equities 40-60% Fixed income 40-60% Real estate 0-10% Cash 0-15% The Pension Committee engages an investment management advisory firm to regularly monitor the performance of the asset managers and ensure they are within compliance with policy. The maximum and minimum of the range for each class is based on the fair value of the assets in the fund. If changes in fair value should lead to allocations outside these boundaries, management shall adjust exposure back to the established guidelines within 90 days or reevaluate the guidelines. The following tables present the assets that are measured at fair value on a recurring basis by level within the U.S. GAAP fair value hierarchy as reported on the Statements of Net Assets Available for Plan Benefits at December 31, 2019 and 2018 , respectively. A financial instrument's level within the fair value hierarchy's is based on the lowest level of input that is significant to the fair value measurement. December 31, 2019 Fair Value Measurements Fair Value Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) (In thousands) Money market mutual funds $ 1,462 $ 1,462 $ — $ — Mutual funds - value stock fund 27,827 27,827 — — Mutual funds - fixed income 158,030 158,030 — — Mutual funds - international stock 34,332 34,332 — — Mutual funds - institutional stock index 113,100 113,100 — — Commingled real estate funds 21,596 — 21,596 — $ 356,347 $ 334,751 $ 21,596 $ — (13) Employee Benefit Plans (continued) Pension Plan, Retirement Income Maintenance Plan (the "RIM Plan") and Post-retirement Plan (cont'd) December 31, 2018 Fair Value Measurements Fair value Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) (In thousands) Money market mutual funds $ 3,459 $ 3,459 $ — $ — Mutual funds - value stock fund 22,533 22,533 — — Mutual funds - fixed income 115,500 115,500 — — Mutual funds - international stock 29,441 29,441 — — Mutual funds - institutional stock index 73,450 73,450 — — Commingled real estate funds 28,591 — 28,591 — $ 272,974 $ 244,383 $ 28,591 $ — Money market and other mutual funds are reported at fair value in the tables above utilizing exchange quoted prices in active markets for identical instruments (Level 1 inputs). The commingled trust funds are reported at their respective net asset values (Level 2 inputs). BOLI and Split-Dollar Life Insurance The Company has Bank-owned life insurance ("BOLI") which is a tax-advantaged transaction that is used to partially fund obligations associated with employee compensation and benefit programs. Policies are purchased insuring officers of the Company using a single premium method of payment. BOLI is accounted for using the cash surrender value and the increase in cash surrender value is included in non-interest income in the Company's Consolidated Statements of Income. At December 31, 2019 and 2018 , the Company had $211.4 million and $184.5 million , respectively, in BOLI. BOLI income for the years ended December 31, 2019 and 2018 , September 30, 2017, and the three months ended December 31, 2017 , was $5.8 million , $5.2 million , $4.9 million , and $1.1 million , respectively. The Company also provides life insurance benefits to eligible employees under an endorsement split-dollar life insurance program. The Company recognizes a liability for future benefits applicable to endorsement split-dollar life insurance arrangements that provide death benefits post-retirement. Through the merger with Atlantic Stewardship Bank, the Company recognized an additional liability for future benefits applicable to endorsement split-dollar life insurance arrangements that provide death benefits post-retirement under that Bank's program. At December 31, 2019 and 2018 , $14.1 million and $10.5 million , respectively, related to the liability under this these programs were recognized in other liabilities in the Company's Consolidated Statements of Financial Condition. The BOLI expense related to the split-dollar benefit for the years ended December 31, 2019 and 2018 , September 30, 2017, and the three months ended December 31, 2017 , was $1.1 million , $1.3 million , $395,000 and $159,000 , respectively. Savings Income Maintenance Deferred Compensation Plan (the "SIM Plan") The Company also maintains a non-qualified defined contribution plan that provides supplemental benefits to certain executives who are prevented from receiving the full benefits contemplated by the 401(k) Plan under tax law limits for tax-qualified plans. The contribution expense for the years ended December 31, 2019 and 2018 , September 30, 2017, and the three months ended December 31, 2017 , was approximately $11,000 , $9,000 , $14,000 and $1,000 , respectively. (13) Employee Benefit Plans (continued) 401(k) Plan The Company has a 401(k) plan covering substantially all employees of the Bank. The Bank may match a percentage of the first 3.00% to 4.50% contributed by participants. The Bank’s matching contribution, if any, is determined by the Board of Directors in its sole discretion. The expense for the years ended December 31, 2019 and 2018 , September 30, 2017, and the three months ended December 31, 2017 , was approximately $1.4 million , $1.3 million , $1.2 million and $289,000 , respectively. Employee Stock Ownership Plan ("ESOP") Effective upon the consummation of the Company's reorganization in April 2018, an ESOP was established for all eligible employees. The ESOP used $45.4 million in proceeds from a twenty year term loan obtained from the Company to purchase 4,542,855 shares of Company common stock. The term loan principal is payable in installments through April 2038. Interest on the term loan is fixed at a rate of 4.75% . Each year, the Bank makes discretionary contributions to the ESOP, which are equal to principal and interest payments required on the term loan. Shares purchased with the loan proceeds were initially pledged as collateral for the term loan and is held in a suspense account for future allocation among participants. Contributions to the ESOP and shares released form the suspense account are allocated among the participants on the basis of compensation, as described by the ESOP, in the year of allocation. The ESOP shares pledged as collateral are reported as unearned ESOP shares in the Consolidated Statements of Financial Condition. As shares are committed to be released from collateral, the Bank reports compensation expense equal to the average market price of the shares during the year, and the shares become outstanding for basic net income per common share computations. ESOP compensation expense for the years ended December 31, 2019 and 2018 was $3.6 million and $2.6 million , respectively. There was no ESOP expense recorded for the year ended September 30, 2017 and the three months ended December 31, 2017 . The ESOP shares were as follows: December 31, 2019 2018 (In thousands) Allocated shares 385 159 Unearned shares 4,156 4,384 Total ESOP shares 4,541 4,543 Fair value of unearned shares $ 70,409 $ 67,025 Supplemental Executive Retirement Plan ("SERP") The Company has a SERP, which is a non-qualified plan which provides supplemental retirement benefits to eligible officers (those designated by the Board of Directors) of the Company who are prevented from receiving the full benefits contemplated by the ESOP's benefit formulas under tax law limits for tax-qualified plans. SERP compensation expense for the years ended December 31, 2019 and 2018 was $267,000 and $165,000 , respectively. There was no SERP expense recorded for the year ended September 30, 2017 and the three months ended December 31, 2017. Stock Based Deferral Plan and Directors Deferred Compensation Plan In addition, the Bank maintains a stock based deferral plan for certain executives and directors, and a cash based deferred compensation plan for directors. The Company records a deferred compensation equity account and corresponding contra-equity account for the cost of the shares held by the Stock Based Deferral Plan. Periodic adjustments to market are not required as participants do not have the option to take the distribution in cash. The Company records a liability for the amount deferred under the Directors Deferred Compensation Plan. There were no expenses recorded under these plans. (13) Employee Benefit Plans (continued) Stock Based Compensation At the Company's 2019 annual meeting held on June 6, 2019, stockholders approved the Columbia Financial, Inc. 2019 Equity Incentive Plan ("2019 Plan") which provides for the issuance of up to 7,949,996 shares ( 2,271,427 restricted stock awards and 5,678,569 stock options) of Columbia Financial Inc. common stock. On July 23, 2019, 1,389,570 shares of restricted stock were awarded, with a grant date fair value of $15.60 per share, and options to purchase 3,707,901 shares of Company common stock were awarded, with a grant date fair value of $4.25 per option. To fund the grant of restricted common stock, the Company issued shares from authorized unissued shares. On December 16, 2019, 74,673 shares of restricted stock were awarded, with a grant date fair value of $17.00 per share, and options to purchase 184,378 shares of Company common stock were awarded, with a grant date fair value of $4.59 per option. To fund the grant of restricted common stock, the Company reissued shares from treasury stock. Restricted shares granted under the 2019 Plan generally vest in equal installments, over the performance or service periods ranging from three to five years , beginning one year from the date of grant. A portion of restricted shares awarded are performance vesting awards, which may or may not vest depending upon the attainment of certain corporate financial targets. Management recognizes compensation expense for the fair value of restricted shares on a straight line basis over the requisite performance or service period. During the year ended December 31, 2019, approximately $2.3 million in expense was recognized in regard to these awards. There was no restricted stock expense recorded for the years ended December 31, 2018 and September 30, 2017 and the three months ended December 31, 2017. The expected future compensation expense related to the 1,420,012 non-vested restricted shares outstanding at December 31, 2019 is approximately $19.9 million over a weighted average period of 4.1 years . Stock options granted under the 2019 Plan generally vest in equal installments over the service period of five years beginning one year from the date of grant. Stock options were granted at an exercise price which represents the fair value of the Company's common stock price on the grant date based on the closing market price, and have an expiration period of 10 years . The following is a summary of the Company's restricted stock activity during the year ended December 31, 2019 : Number of Restricted Shares Weighted Average Grant Date Fair Value Outstanding, January 1, 2019 — $ — Granted 1,464,243 15.67 Forfeited (44,231 ) 15.60 Outstanding, December 31, 2019 1,420,012 $ 15.67 The fair value of stock options granted on July 23, 2019 was estimated utilizing the Black-Scholes option pricing model using the following assumptions: expected life of 6.5 years , risk-free rate of return of 1.90% , volatility of 22.12% , and a dividend yield of 0.00% . Stock options granted under the 2019 Plan vest in equal installments over the service period of five years beginning one year from the date of grant. Stock options were granted at an exercise price of $15.60 , which represents the fair value of the Company's common stock price on the grant date based on the closing market price, and have an expiration period of 10 years . The fair value of stock options granted on December 16, 2019 was estimated utilizing the Black-Scholes option pricing model using the following assumptions: expected life of 6.5 years , risk-free rate of return of 1.79% , volatility of 22.23% , and a dividend yield of 0.00% . Stock options granted under the 2019 Plan generally vest in equal installments over the service period of five years beginning one year from the date of grant. Stock options were granted at an exercise price of $17.00 , which represents the fair value of the Company's common stock price on the grant date based on the closing market price, and have an expiration period of approximately 10 years . The expected life of the options represents the period of time that stock options are expected to be outstanding and is estimated using the simplified approach, which assumes that all outstanding options will be exercised at the midpoint of the vesting date and full contractual term. The risk-free rate of return is based on the rates on the grant date of a U.S. Treasury Note with a term equal to the expected option life. Since the Company recently converted to a public Company and does not have sufficient historical price data, the (13) Employee Benefit Plans (continued) Stock Based Compensation (cont'd) expected volatility is based on the historical daily stock prices of a peer group of similar entities based on factors such as industry, stage of life cycle, size and financial leverage. The Company has not paid any cash dividends on its common stock. Management recognizes expense for the fair value of these awards on a straight line basis over the requisite service period. During the year ended December 31, 2019, approximately $1.4 million in expense was recognized in regard to these awards. There was no stock option expense recorded for the years ended December 31, 2018 and September 30, 2017 and the three months ended December 31, 2017. The expected future compensation expense related to the 3,784,044 non-vested options outstanding at December 31, 2019 is $14.8 million over a weighted average period of 4.6 years . The following is a summary of the Company's option activity during the year ended December 31, 2019 : Number of Stock Options Weighted Average Exercise Price Weighted Average Remaining Contractual Term (in years) Aggregate Intrinsic Value Outstanding, January 1, 2019 — $ — — $ — Granted 3,892,279 15.67 9.6 Forfeited (108,235 ) 15.60 Outstanding, December 31, 2019 3,784,044 $ 15.67 9.6 $ 4,812,490 Options exercisable at December 31 2019 — $ — — $ — The aggregate intrinsic value in the table above represents the total pre-tax intrinsic value, the difference between the Company's closing stock price on the last trading day of the period and the exercise price, multiplied by the number of in-the-money options. There were no stock option exercises during the years ended December 31, 2019 and 2018 , September 30, 2017 and the three months ended December 31, 2017.

Income Taxes

Income Taxes	12 Months Ended
Income Taxes	Dec. 31, 2019
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes On December 22, 2017, the President signed into law the Tax Act. The new law reduces the federal corporate income tax rate from 35% to 21% effective January 1, 2018. Under ASC 740, "Income Taxes", companies are required to recognize the effect of tax law changes in the period of enactment; therefore, the Company re-measured its deferred tax assets and liabilities at the enacted tax rate expected to apply when its temporary differences are expected to be realized or settled. As a result of the enactment of the Act, the Company recognized an additional tax expense of $11.7 million for the three months ended December 2017. (14) Income Taxes (continued) The current and deferred amounts of income tax expense (benefit) for the years ended December 31, 2019 and 2018, September 30, 2017, and the three months ended December 31, 2017 are as follows: Years Ended December 31, Three Months Ended December 31, Year Ended September 30, 2019 2018 2017 2017 (In thousands) Current: Federal $ 5,933 $ 11,284 $ 630 $ 16,198 State 2,905 5,129 862 1,236 Total current 8,838 16,413 1,492 17,434 Deferred: Federal 8,275 (4,901 ) 7,530 (1,454 ) State (748 ) (589 ) (39 ) 28 Total deferred 7,527 (5,490 ) 7,491 (1,426 ) Total income tax expense $ 16,365 $ 10,923 $ 8,983 $ 16,008 The Company reported deferred tax expense (benefit) of $(5.5) million , $1.4 million , $6.4 million and $(119,000) for the years ended December 31, 2019 and 2018, September 30, 2017, and the three months ended December 31, 2017 , respectively, related to the unrealized gains (losses) on securities available for sale, which is reported in accumulated other comprehensive income (loss), net of tax. Additionally, the Company recorded a deferred tax (benefit) expense of $779,000 , $(530,000) , $(4.2) million and $(94,000) , respectively, related to the reclassification adjustment of actuarial net (loss) gain on employee benefit obligations, which is reported in accumulated other comprehensive income, net of tax. Deferred tax expense for the year ended December 31, 2019 also includes $2.3 million in expense recorded for purchase accounting adjustments related to the Stewardship acquisition. A reconciliation between the amount of reported total income tax expense and the amount computed by multiplying the applicable statutory federal income tax rate (21% for the 2019 and 2018 periods, and 35% for the 2017 periods) is as follows: Years Ended December 31, Three Months Ended December 31, Year Ended September 30, 2019 2018 2017 2017 (In thousands) Tax expense at applicable statutory rate $ 14,927 $ 7,067 $ 4,431 $ 16,478 Increase (decrease) in taxes resulting from: State tax, net of federal income tax benefit 1,704 3,587 535 822 ESOP fair market value adjustment 272 202 — — Tax exempt interest income (6 ) (4 ) (2 ) (50 ) Income from Bank-owned life insurance (1,246 ) (812 ) (381 ) (1,589 ) Dividend received deduction (8 ) (16 ) (10 ) (40 ) Non-deductible merger-related expenses 222 — — — Non-deductible compensation expense 398 — — — Impact of tax reform — — 4,700 — Other, net 102 899 (290 ) 387 Total income tax expense $ 16,365 $ 10,923 $ 8,983 $ 16,008 (14) Income Taxes (continued) The net deferred tax asset is included in other assets in the Consolidated Statements of Financial Condition. The tax effects of temporary differences that give rise to significant portions of the deferred tax assets and deferred tax liabilities at December 31, 2019 and 2018 are as follows: At December 31, 2019 2018 (In thousands) Deferred tax assets: Allowance for loan losses $ 13,114 $ 13,251 Post-retirement benefits 4,089 3,720 Deferred compensation 2,085 2,228 Depreciation 1,002 1,042 Retirement Income Maintenance plan 1,725 1,602 ESOP 301 128 Stock-based compensation 788 35 Reserve for uncollected interest 54 24 Net unrealized losses on debt securities and defined benefit plans 18,374 19,060 Federal and State NOLs 8,333 2,063 Alternative minimum assessment carryforwards 2,156 2,156 Charitable contribution carryforward 5,981 6,085 Purchase accounting 665 — Other items 332 670 Gross deferred tax assets 58,999 52,064 Valuation allowance (7,442 ) (2,388 ) 51,557 49,676 Deferred tax liabilities: Pension expense 33,856 26,071 Deferred loan costs 5,911 5,736 Intangible assets 1,215 1,621 Other items 266 34 Total gross deferred tax liabilities 41,248 33,462 Net deferred tax asset $ 10,309 $ 16,214 Retained earnings at December 31, 2019 and 2018 includes approximately $21.5 million for which no provision for income tax has been made. This amount represents an allocation of income to bad debt deductions for tax purposes only. Events that would result in taxation of these reserves include the failure to qualify as a bank for tax purposes, distributions in complete or partial liquidation, stock redemptions and excess distributions to stockholders. Management believes that not all existing net deductible temporary differences that comprise the net deferred tax asset will reverse during periods in which the Company generates sufficient net taxable income. Accordingly, management has established a valuation allowance. Significant changes in the Company's operations and or economic conditions could affect the benefits of the recognized net deferred tax asset. Based on all available evidence, a valuation allowance was established for the portion of the state tax benefit that is not more likely than not to be realized. At December 31, 2019 and 2018 , the Company's valuation allowance totaled $7.4 million and $2.4 million , respectively. Based upon projections of future taxable income and the ability to carryforward net operating losses indefinitely, management believes it is more likely than not the Company will realize the remaining deferred tax asset. (14) Income Taxes (continued) The Company had federal net operating losses from the acquisition of Stewardship of $5.8 million as of December 31, 2019. These net operating losses are subject to a $2.3 million annual limitation under Code Section 382 and will not expire. The Company had New Jersey net operating loss carryforwards of $70.9 million and $24.0 million , respectively, available to offset future taxable income as of December 31, 2019 and 2018 , respectively. If not utilized, these carryforwards will expire periodically through 2038. As of December 31, 2019 and 2018, the Company had approximately $2.2 million of New Jersey AMA Tax Credits. These credits do not expire. As of December 31, 2019 and 2018, the Company had New Jersey NOLs of $28.9 million . If not utilized, these carryforwards will expire periodically through 2038. The Company files income tax returns in the United States federal jurisdiction and in the states of New Jersey, New York and Pennsylvania. As of December 31, 2019, the Company is no longer subject to federal income tax examination for the years prior to 2015. Columbia Bank MHC and its subsidiaries' New York returns are currently under audit for the tax years 2016 and 2017. The Company is open for examination by the State of New Jersey for years after 2014 and the States of Pennsylvania and New York for years after 2015.

Financial Transactions with Off

Financial Transactions with Off-Balance-Sheet Risk and Concentrations of Credit Risk	12 Months Ended
	Dec. 31, 2019
Commitments and Contingencies Disclosure [Abstract]
Financial Transactions with Off-Balance-Sheet Risk and Concentrations of Credit Risk	Financial Transactions with Off-Balance-Sheet Risk and Concentrations of Credit Risk The Company is a party to financial instruments with off-balance-sheet risk in the normal course of business in order to meet the financing needs of its customers. These financial instruments consist of commitments to extend credit and involve, to varying degrees, elements of credit and interest rate risk in excess of the amounts recognized in the Consolidated Statements of Financial Condition. At December 31, 2019 and 2018 , the following commitments existed which are not reflected in the Consolidated Statements of Financial Condition: December 31, 2019 2018 (In thousands) Loan commitments: Residential real estate $ 91,141 $ 29,622 Multifamily and commercial real estate 95,025 73,201 Commercial business 18,737 13,000 Construction 59,990 71,062 Consumer home equity loans and lines of credit 5,988 8,344 Total loan commitments $ 270,881 $ 195,229 Unused lines of credit consisting of home equity lines, and undisbursed business and construction lines totaled approximately $910.0 million and $714.6 million as of December 31, 2019 and 2018 , respectively. Amounts drawn on the unused lines of credit are predominantly assessed interest at rates that fluctuate with the base rate. The Company uses the same credit policies and collateral requirements in making commitments and conditional obligations as it does for on-balance-sheet loans. Commitments to extend credit are agreements to lend customers as long as there is no violation of any condition established in the contract. Commitments generally have fixed expiration dates or other termination clauses and may require payment of a fee. Since the commitments may expire without being drawn upon, the total commitment amounts do not necessarily represent future cash requirements. The Company evaluates each customer's creditworthiness on a case-by-case basis. The amount of collateral obtained, if deemed necessary by the Company upon extension of credit, is based on management's credit evaluation of the borrower. The Company principally grants residential, multifamily and commercial real estate loans, construction loans, commercial and industrial loans, home equity loans and advances and other consumer loans to borrowers primarily throughout New Jersey, in New York and Pennsylvania, and to a much lesser extent in a few other east coast states. Its borrowers' abilities to repay their obligations are dependent upon various factors, including the borrowers' income and net worth, cash flows generated by the underlying collateral, if any, or from business operations, value of the underlying collateral and priority of the Company's lien on the property. These factors are (15) Financial Transactions with Off-Balance-Sheet Risk and Concentrations of Credit Risk (continued) dependent on various economic conditions and circumstances beyond the Company's control , and as a result, the Company is subject to the risk of loss. The Company believes that its lending policies and procedures adequately minimize the potential exposure to such risks and adequate provisions for loan losses are provided for all probable and estimable losses. In the normal course of business, the Company sells residential real estate loans to third parties. These loan sales are subject to customary representations and warranties. In the event that the Company is found to be in breach of these representations and warranties, it may be obligated to repurchase certain of these loans. The Company has entered into derivative financial instruments to manage exposures that arise from business activities that result in the receipt or payment of future known and uncertain cash amounts, the value of which are determined by interest rates. The Company's derivative financial instruments are used to manage differences in the amount, timing, and duration of the Company's known or expected cash receipts and its known or expected cash payments principally related to the Company's borrowings. These derivatives were used to hedge the variability in cash flows associated with certain short-term funding transactions. The fair value of the derivatives as of December 31, 2019 and 2018 was a net liability of $11.4 million and $2.6 million , respectively, inclusive of accrued interest and variation margin posted in accordance with the Chicago Mercantile Exchange. In connection with its mortgage banking activities, at December 31, 2018 the Company had commitments of approximately $8.1 million , to sell loans, with servicing retained by the Bank. In addition to the commitments noted above, the Company is party to standby letters of credit which are conditional commitments issued by the Bank to guarantee the performance of a customer to a third party. The guarantees generally extend for a term of up to one year and may be secured or unsecured. Outstanding letters of credit totaled $8.4 million and $7.0 million at December 31, 2019 and 2018 , respectively. Certain bank facilities are occupied under non-cancelable operating leases on buildings and land used for office space and banking purposes, which expire at various dates through August 2030. Certain lease agreements provide for renewal options and increases in rental payments based upon increases in the consumer price index or the lessor's cost of operating the facility. Minimum aggregate lease payments for the remainder of the lease terms as of December 31, 2019 are as follows: Amount (In thousands) Years ending: 2020 $ 4,942 2021 4,484 2022 4,012 2023 3,503 2024 2,732 Thereafter 5,001 Total lease commitments $ 24,674 Net occupancy expense, which represents rental expenses for Bank facilities, for the years ended December 31, 2019 and 2018 , September 30, 2017, and the three months ended December 31, 2017 , totaled $5.0 million , $4.6 million , $4.3 million , and $1.1 million , respectively. In the normal course of business, there are outstanding various legal proceedings, claims, and contingent liabilities which are not included in the consolidated financial statements. In the opinion of management, the financial position of the Company will not be materially affected by the outcome of such legal proceedings and claims.

Fair Value Measurements

Fair Value Measurements	12 Months Ended
Fair Value Measurements	Dec. 31, 2019
Fair Value Disclosures [Abstract]
Fair Value Measurements	Fair Value Measurements The Company utilizes fair value measurements to record fair value adjustments to certain assets and liabilities and to determine fair value disclosures. The determination of fair values of financial instruments often requires the use of estimates. Where quoted market values in an active market are not readily available, the Company utilizes various valuation techniques to estimate fair value. In January 2016, the FASB issued ASU 2016-01- "Financial Instruments". This guidance amended existing guidance to improve accounting standards for financial instruments including clarification and simplification of the accounting and disclosure requirements and the requirement to use the exit price notion when measuring the fair value of financial instruments for disclosure purposes. The Company adopted the guidance effective January 1, 2019, and the fair value of the Company's loan portfolio at December 31, 2019 is presented using an exit price method. The fair value of loans was measured using the entry price notion as of December 31, 2018. Fair value is the exchange price that would be received for an asset or paid to transfer a liability (exit price) in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants on the measurement date. There are three levels of inputs that may be used to measure the fair value: Level 1: Unadjusted quoted prices for identical assets or liabilities in active markets that the Company has the ability to access on the measurement date. Level 2: Inputs other than quoted prices included in Level 1 that are observable for the asset or liability, either directly or indirectly. These might include quoted prices for similar instruments in markets that are active or not active, or inputs that are observable or can be corroborated by observable market data for substantially the full term of the asset or liability. Level 3: Prices or valuation techniques that require unobservable inputs that are both significant to the fair value measurement and unobservable (i.e., supported by minimal or no market activity). Valuation techniques include the use of option pricing models, discounted cash flow models and similar techniques. A financial instrument’s level within the fair value hierarchy is based on the lowest level of input that is significant to the fair value measurement. Assets and Liabilities Measured at Fair Value on a Recurring Basis The methods described below were used to measure fair value of financial instruments as reflected in the tables below on a recurring basis as of December 31, 2019 and 2018 . Debt Securities Available for Sale, at Fair Value For debt securities available for sale, fair value was estimated using a market approach. The majority of these securities are fixed income instruments that are not quoted on an exchange, but are traded in active markets. Prices for these instruments are obtained through third-party data service providers or dealer market participants with which the Company has historically transacted both purchases and sales of securities. Prices obtained from these sources include market quotations and matrix pricing. Matrix pricing, a Level 2 input, is a mathematical technique used principally to value certain securities to a benchmark or to comparable securities. The Company evaluates the quality of Level 2 matrix pricing through comparison to similar assets with greater liquidity and evaluation of projected cash flows. As the Company is responsible for the determination of fair value, it performs quarterly analysis on the prices received from the pricing service to determine whether the prices are reasonable estimates of fair value. Specifically, the Company compares the prices received from the pricing service to a secondary pricing source. Additionally, the Company compares changes in the reported market values and returns to relevant market indices to assess the reasonableness of the reported prices. The Company’s internal price verification procedures and review of fair value methodology documentation provided by independent pricing services has not historically resulted in an adjustment in the prices obtained from the pricing service. The Company may hold debt instruments issued by the U.S. government and U.S. government-sponsored agencies that are traded in active markets with readily accessible quoted market prices that are considered Level 1 inputs. (16) Fair Value Measurements (continued) Equity Securities, at Fair Value The Company holds equity securities that are traded in active markets with readily accessible quoted market prices that are considered Level 1 instruments. A trust preferred security that is not traded in an active market, an Atlantic Community Bankers Bank ("ACBB" ) stock which is based on redemption at par value and can only be sold to the issuing ACBB or another institution that holds ACBB stock are considered Level 2 instruments. Derivatives The Company records all derivatives included in other assets and liabilities on the consolidated statements of financial condition at fair value. The accounting for changes in the fair value of derivatives depends on the intended use of the derivative, whether the Company has elected to designate a derivative in a hedging relationship and apply hedge accounting, and whether the hedging relationship has satisfied the criteria necessary to apply hedge accounting. See note 21 for disclosures related to the accounting treatment for derivatives. The fair value of the Company's derivatives is determined using discounted cash flow analysis using observable market-based inputs, which are considered Level 2 inputs. The following tables present the assets and liabilities reported on the Consolidated Statements of Financial Condition at their fair values as of December 31, 2019 and 2018 , by level within the fair value hierarchy: December 31, 2019 Fair Value Measurements Fair Value Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) (In thousands) Debt securities available for sale: U.S. government and agency obligations $ 42,386 $ 42,386 $ — $ — Mortgage-backed securities and collateralized mortgage obligations 979,881 — 979,881 — Municipal obligations 2,284 — 2,284 — Corporate debt securities 69,180 — 69,180 — Trust preferred securities 4,605 — 4,605 — Total debt securities available for sale 1,098,336 42,386 1,055,950 — Equity securities 2,855 2,587 268 — Derivative assets 185 — 185 — $ 1,101,376 $ 44,973 $ 1,056,403 $ — Derivative liabilities $ 11,546 $ — $ 11,546 $ — (16) Fair Value Measurements (continued) December 31, 2018 Fair Value Measurements Fair Value Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) (In thousands) Debt securities available for sale: U.S. government and agency obligations $ 54,157 $ 54,157 $ — $ — Mortgage-backed securities and collateralized mortgage obligations 920,007 — 920,007 — Municipal obligations 987 — 987 — Corporate debt securities 53,467 — 53,467 — Trust preferred securities 4,250 — 4,250 — Total debt securities available for sale 1,032,868 54,157 978,711 — Equity securities 1,890 1,890 — — Derivative assets 1,342 — 1,342 — $ 1,036,100 $ 56,047 $ 980,053 $ — Derivative liabilities $ 3,944 $ — $ 3,944 $ — There were no transfers between Level 1, Level 2, and Level 3 during the years ended December 31, 2019 and 2018 , and the three months ended December 31, 2017. During the year ended September 30, 2017, U.S. Government and agency obligations with a carrying value of $20.4 million were transferred from Level 2 to Level 1. There were no Level 3 assets measured at fair value on a recurring basis at December 31, 2019 and 2018 . Assets Measured at Fair Value on a Non-Recurring Basis The valuation techniques described below were used to estimate fair value of financial instruments measured on a non-recurring basis as of December 31, 2019 and 2018 . Collateral Dependent Impaired Loans Loans which meet certain criteria are evaluated individually for impairment. For loans measured for impairment based on the fair value of the underlying collateral, fair value was estimated using a market approach. The Company measures the fair value of collateral underlying impaired loans primarily through obtaining independent appraisals that rely upon quoted market prices for similar assets in active markets. These appraisals include adjustments, on an individual case-by-case basis, to comparable assets based on the appraisers’ market knowledge and experience, as well as adjustments for estimated costs to sell between 6% and 8% . The Company classifies these loans as Level 3 within the fair value hierarchy. For non-collateral dependent loans, the expected value of future cash flows is used to estimate fair value. Real Estate Owned Assets acquired through foreclosure or deed in lieu of foreclosure are carried at fair value, less estimated costs to sell between 6% and 8% . Fair value is generally based on independent appraisals that rely upon quoted market prices for similar assets in active markets. These appraisals include adjustments, on an individual case basis, to comparable assets based on the appraiser's market knowledge and experience, and are classified as Level 3. When an asset is acquired, the excess of the loan balance over fair value less estimated selling costs is charged to the allowance for loan losses. Operating results from real estate owned, including rental income, operating expenses, and gains and losses realized from the sales of real estate owned, are recorded as incurred. (16) Fair Value Measurements (continued) Mortgage Servicing Rights, Net ("MSR"s") Mortgage servicing rights are carried at the lower of cost or estimated fair value. The estimated fair value of MSRs is obtained through an analysis of future cash flows, incorporating assumptions that market participants would use in determining fair value including market discount rates, prepayments speeds, servicing income, servicing costs, default rates and other market driven data, including the market's perception of future interest rate movements. The prepayment speed and the discount rate are considered two of the most significant inputs in the model. A significant degree of judgment is involved in valuing the mortgage servicing rights using Level 3 inputs. The use of different assumptions could have a significant effect on this fair value estimate. The following tables present the assets and liabilities reported on the Consolidated Statements of Financial Condition at their fair values as of December 31, 2019 and 2018 , by level within the fair value hierarchy: December 31, 2019 Fair Value Measurements Fair Value Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) (In thousands) Impaired loans $ 1,063 $ — $ — $ 1,063 Mortgage servicing rights 681 — — 681 $ 1,744 $ — $ — $ 1,744 December 31, 2018 Fair Value Measurements Fair Value Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) (In thousands) Impaired loans $ 125 $ — $ — $ 125 Real estate owned 92 — — 92 Mortgage servicing rights 442 — — 442 $ 659 $ — $ — $ 659 The following table presents information for Level 3 assets measured at fair value on a non-recurring basis as of December 31, 2019 and 2018 : December 31, 2019 Fair Value Valuation Methodology Unobservable Inputs Range of Inputs Weighted Average (Dollars in thousands) Impaired loans $ 1,063 Estimated cash flow Expected value of future cash flows (5) —% —% Mortgage servicing rights 681 Estimated cash flow Prepayment speeds and discount rates (4) 3.6% - 24.0% 12.7% (16) Fair Value Measurements (continued) December 31, 2018 Fair Value Valuation Methodology Unobservable Inputs Range of Inputs Weighted Average (Dollars in thousands) Impaired loans $ 125 Appraised value (2) Discount for cost to sell (3) 6.0% 6.0% Real estate owned 92 Contract sales price (1) Discount for cost to sell (3) 6.0% 6.0% Mortgage servicing rights 442 Estimated cash flow Prepayment speeds (4) 3.3% - 26.8% 12.0% (1) Value is based on signed contract for sale. (2) Value is based on an independent appraisal of the fair value of the loan's underlying collateral. (3) Includes commissions, fees and other costs. (4) Value of SBA servicing rights based on a discount rate of 11.75%. (5) Value based on management's estimate of expected future cash flows. Other Fair Value Disclosures The Company is required to disclose estimated fair value of financial instruments, both assets and liabilities on and off the balance sheet, for which it is practicable to estimate fair value. A description of the valuation methodologies used for those assets and liabilities not recorded at fair value on a recurring or non-recurring basis are set forth below. Cash and Cash Equivalents For cash and due from banks, federal funds sold and short-term investments, the carrying amount approximates fair value due to their nature and short-term maturities. Debt Securities Held to Maturity For debt securities held to maturity, fair value was estimated using a market approach. The majority of the Company’s securities are fixed income instruments that are not quoted on an exchange, but are traded in active markets. Prices for these instruments are obtained through third-party data service providers or dealer market participants with which the Company has historically transacted both purchases and sales of securities. Prices obtained from these sources include market quotations and matrix pricing. Matrix pricing, a Level 2 input, is a mathematical technique used principally to value certain securities to benchmark or to compare securities. The Company evaluates the quality of Level 2 matrix pricing through comparison to similar assets with greater liquidity and evaluation of projected cash flows. As the Company is responsible for the determination of fair value, it performs quarterly analysis on the prices received from the pricing service to determine whether the prices are reasonable estimates of fair value. Specifically, the Company compares the prices received from the pricing service to a secondary pricing source. Additionally, the Company compares changes in the reported market values and returns to relevant market indices to assess the reasonableness of the reported prices. The Company’s internal price verification procedures and review of fair value methodology documentation provided by independent pricing services has not historically resulted in an adjustment in the prices obtained from the pricing service. The Company also holds debt instruments issued by the U.S. government and U.S. government sponsored agencies that are traded in active markets with readily accessible quoted market prices that are considered Level 1 inputs within the fair value hierarchy. Federal Home Loan Bank Stock ("FHLB") The fair value of FHLB stock is based on redemption at par value and can only be sold to the issuing FHLB, to other FHLBs, or to other member banks. As such, the Company's FHLB stock is recorded at cost, or par value, and is evaluated for impairment each reporting period by considering the ultimate recoverability of the investment rather than temporary declines in value. The Company classifies the estimated fair value as Level 2 within the fair value hierarchy. (16) Fair Value Measurements (continued) Loans Receivable Fair values are estimated for portfolios of loans with similar financial characteristics. Loans are segregated by type such as commercial mortgage, residential mortgage, commercial, construction, and consumer and other. Each loan category is further segmented into fixed and adjustable rate interest terms and into performing and non-performing categories. The fair value of performing loans was estimated using a combination of techniques, including a discounted cash flow model that utilizes a discount rate that reflects the Company's current pricing for loans with similar characteristics and remaining maturity, adjusted by an amount for estimated credit losses inherent in the portfolio at the balance sheet date. The rates take into account the expected yield curve, as well as an adjustment for prepayment risk, when applicable. The Company classifies the estimated fair value of its loan portfolio as Level 3 . The fair value for significant non-performing loans was based on recent external appraisals of collateral securing such loans, adjusted for the timing of anticipated cash flows. The Company classifies the estimated fair value of its non-performing loan portfolio as Level 3 . In accordance with the prospective adoption of ASU 2016-01, the fair value of loans was measured using the exit price method as of December 31, 2019 . The fair value of loans was measured using the entry price notion as of December 31, 2018. Deposits The fair value of deposits with no stated maturity, such as demand, money market, and savings and club deposits are payable on demand at each reporting date and classified as Level 2 . The estimated fair value of certificates of deposit was based on the discounted value of contractual cash flows. The discount rate was estimated using the Company’s current rates offered for deposits with similar remaining maturities. The Company classifies the estimated fair value of its certificates of deposit portfolio as Level 2 . Borrowings The fair value of borrowings was estimated by discounting future cash flows using rates available for debt with similar terms and maturities and is classified by the Company as Level 2 within the fair value hierarchy. Commitments to Extend Credit and Letters of Credit The fair value of commitments to extend credit and letters of credit was estimated using the fees currently charged to enter into similar agreements, taking into account the remaining terms of the agreements and the present creditworthiness of the counter-parties. For fixed rate loan commitments, fair value also considers the difference between current levels of interest rates and the committed rates. The fair value estimates of commitments to extend credit and letters of credit are deemed immaterial in comparison to their carrying value. The following tables present the assets and liabilities reported on the Consolidated Statements of Financial Condition at their fair values as of December 31, 2019 and 2018 : (16) Fair Value Measurements (continued) December 31, 2019 Fair Value Measurements Carrying Value Total Fair Value Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) (In thousands) Financial assets: Cash and cash equivalents $ 75,547 $ 75,547 $ 75,547 $ — $ — Debt securities available for sale 1,098,336 1,098,336 42,386 1,055,950 — Debt securities held to maturity 285,756 289,505 19,960 269,545 — Equity securities, at fair value 2,855 2,855 2,587 268 Federal Home Loan Bank stock 69,579 69,579 — 69,579 — Loans receivable, net 6,135,857 6,219,008 — — 6,219,008 Derivative assets 185 185 — 185 — Financial liabilities: Deposits $ 5,645,842 $ 5,654,075 $ — $ 5,654,075 $ — Borrowings 1,407,022 1,411,962 — 1,411,962 — Derivative liabilities 11,546 11,546 — 11,546 — December 31, 2018 Fair Value Measurements Carrying Value Total Fair Value Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) (In thousands) Financial assets: Cash and cash equivalents $ 42,201 $ 42,201 $ 42,201 $ — $ — Debt securities available for sale 1,032,868 1,032,868 54,157 978,711 — Debt securities held to maturity 262,143 254,841 23,241 231,600 — Equity securities 1,890 1,890 1,890 — — Federal Home Loan Bank stock 58,938 58,938 — 58,938 — Loans held-for-sale 8,081 8,081 8,081 — Loans receivable, net 4,916,840 4,841,830 — — 4,841,830 Derivative assets 1,342 1,342 — 1,342 — Financial liabilities: Deposits $ 4,413,873 $ 4,402,336 $ — $ 4,402,336 $ — Borrowings 1,189,180 1,185,007 — 1,185,007 — Derivative liabilities 3,944 3,944 — 3,944 — (16) Fair Value Measurements (continued) Limitations Fair value estimates are made at a specific point in time, based on relevant market information and information about the financial instrument. These estimates do not reflect any premium or discount that could result from offering for sale at one time the Company’s entire holdings of a particular financial instrument. Because limited markets exist for a significant portion of the Company’s financial instruments, fair value estimates are based on judgments regarding future expected loss experience, current economic conditions, risk characteristics of various financial instruments, and other factors. These estimates are subjective in nature and involve uncertainties and matters of significant judgment and, therefore, cannot be determined with precision. Changes in assumptions could significantly affect the estimates.

Selected Quarterly Financial Da

Selected Quarterly Financial Data (Unaudited)	12 Months Ended
Selected Quarterly Financial Data (Unaudited)	Dec. 31, 2019
Quarterly Financial Information Disclosure [Abstract]
Selected Quarterly Financial Data (Unaudited)	Selected Quarterly Financial Data (Unaudited) The following tables are a condensed summary of certain quarterly results of operation for the years ended December 31, 2019 and 2018 , September 30, 2017, and the three months ended December 31, 2017 : Quarters Ended December 31, 2019 March 31 June 30 September 30 December 31 (Dollars in thousands, except share and per share data) Total interest income $ 62,887 $ 62,732 $ 64,438 $ 71,026 Total interest expense 20,503 21,889 22,722 23,598 Net interest income 42,384 40,843 41,716 47,428 Provision for loan losses 436 112 1,157 2,519 Net interest income after provision for loan losses 41,948 40,731 40,559 44,909 Total non-interest income 6,037 6,775 10,115 8,709 Total non-interest expense 29,559 31,841 31,064 36,237 Income before income tax expense 18,426 15,665 19,610 17,381 Income tax expense 3,507 3,634 5,392 3,832 Net income $ 14,919 $ 12,031 $ 14,218 $ 13,549 Earnings per share - basic and diluted $ 0.13 $ 0.11 $ 0.13 $ 0.12 Weighted average shares outstanding - basic and diluted 111,536,577 111,553,203 111,371,754 109,958,999 Quarters Ended December 31, 2018 March 31 June 30 September 30 December 31 (Dollars in thousands, except share and per share data) Total interest income $ 51,791 $ 55,019 $ 57,695 $ 61,785 Total interest expense 12,730 14,004 17,112 18,410 Net interest income 39,061 41,015 40,583 43,375 Provision for loan losses 2,000 2,400 1,500 777 Net interest income after provision for loan losses 37,061 38,615 39,083 42,598 Total non-interest income 4,543 5,450 5,290 6,405 Total non-interest expense 26,015 61,768 26,590 31,013 Income (loss) before income tax expense 15,589 (17,703 ) 17,783 17,990 Income tax expense 3,805 (2,961 ) 6,956 3,123 Net income (loss) $ 11,784 $ (14,742 ) $ 10,827 $ 14,867 Earnings per share - basic and diluted N/A $ (0.13 ) $ 0.10 $ 0.13 Weighted average shares outstanding - basic and diluted N/A 111,360,278 111,389,951 111,423,361 (17) Selected Quarterly Financial Data (Unaudited) (continued) Quarter Ended December 31, 2017 Dollars in thousands, except per share data) Total interest income $ 49,169 Total interest expense 12,240 Net interest income 36,929 Provision for loan losses 3,400 Net interest income after provision for loan losses 33,529 Total non-interest income 4,733 Total non-interest expense 25,601 Income before income tax expense 12,661 Income tax expense 8,983 Net income $ 3,678 Earnings per share - basic and diluted N/A Quarters Ended September 30, 2017 December 31 March 31 June 30 September 30 (Dollars in thousands, except per share data) Total interest income $ 44,129 $ 45,428 $ 46,850 $ 47,820 Total interest expense 10,724 10,651 11,211 11,860 Net interest income 33,405 34,777 35,639 35,960 Provision for loan losses — 375 375 5,676 Net interest income after provision for loan losses 33,405 34,402 35,264 30,284 Total non-interest income 5,534 5,806 4,645 1,630 Total non-interest expense 24,078 24,903 24,703 30,206 Income before income tax expense 14,861 15,305 15,206 1,708 Income tax expense 4,868 5,012 5,934 194 Net income $ 9,993 $ 10,293 $ 9,272 $ 1,514 Earnings per share - basic and diluted N/A N/A N/A N/A

Earnings per Share

Earnings per Share	12 Months Ended
Earnings per Share	Dec. 31, 2019
Earnings Per Share [Abstract]
Earnings per Share	Earnings per Share Basic earnings per share ("EPS") is computed by dividing net income available to common shareholders by the weighted average number of common shares outstanding during the period. For purposes of calculating basic EPS, weighted average common shares outstanding excludes treasury stock, unallocated employee stock ownership plan shares that have not been committed for release and deferred compensation obligations required to be settled in shares of Company stock. Diluted EPS is computed using the same method as basic EPS and reflects the potential dilution which could occur if stock options and unvested shares were exercised and converted into common stock. The potentially diluted shares would then be included in the weighted average number of shares outstanding for the period using the treasury stock method. For the year ended December 31, 2019 , there were no shares related to outstanding options that were dilutive as the Company had no stock options outstanding. For the years ended December 31, 2018 , September 30, 2017, and the three months ended December 31, 2017 , the Company did not have any stock options outstanding. (18) Earnings per Share (continued) The following is a reconciliation of the numerators and denominators of the basic and diluted earnings per share calculations for the years ended December 31, 2019 and 2018 , September 30, 2017, and the three months ended December 31, 2017: December 31, Three Months Ended December 31, September 30, 2019 2018 2017 2017 (Dollars in thousands, except share and per share data) Net income $ 54,717 $ 22,736 $ 3,678 $ 31,072 Shares: Weighted average shares outstanding - basic 111,101,246 111,395,723 N/A N/A Weighted average dilutive shares outstanding — — N/A N/A Weighted average shares outstanding - diluted 111,101,246 111,395,723 N/A N/A Earnings per share: Basic $ 0.49 $ 0.20 N/A N/A Diluted $ 0.49 $ 0.20 N/A N/A The average number of stock options which were anti-dilutive and were not included in the computation of diluted earnings per share, totaled 1,111,650 , for the year ended December 31, 2019 . There were no stock options outstanding for the years ended December 31, 2018 and September 30, 2017, or during the three months ended December 31, 2017.

Parent-only Financial Informati

Parent-only Financial Information	12 Months Ended
Parent-only Financial Information	Dec. 31, 2019
Condensed Financial Information Disclosure [Abstract]
Parent-only Financial Information	Parent-only Financial Information The condensed financial statements of Columbia Financial, Inc. (parent company) are presented below: Statements of Financial Condition December 31, 2019 2018 (In thousands) Assets Cash and due from Bank $ 168,242 $ 153,697 Short-term investments 127 136 Total cash and cash equivalents 168,369 153,833 Debt securities available for sale, at fair value 1,496 — Equity securities, at fair value 1,282 1,420 Investment in subsidiaries 785,964 764,663 Loan receivable from Bank 42,982 44,439 Other assets 8,431 7,852 Total assets $ 1,008,524 $ 972,207 Liabilities and Stockholders' Equity Liabilities: Borrowings $ 23,831 $ — Accrued expenses and other liabilities 2,176 147 Total liabilities 26,007 147 Total stockholders' equity 982,517 972,060 Total liabilities and stockholders' equity $ 1,008,524 $ 972,207 (19) Parent-only Financial Information (continued) Statements of Comprehensive Income (Loss) Years Ended December 31, Three Months Ended December 31, Year Ended September 30, 2019 2018 2017 2017 (In thousands) Income: Dividends from subsidiary $ 179,000 $ — $ — $ 2,000 Loans receivable 2,111 1,513 — — Debt securities available for sale and equity securities 51 123 41 162 Interest-earning deposits 173 871 — 1 Total interest income 181,335 2,507 41 2,163 Interest expense on borrowings 176 3,468 1,044 4,177 Net interest income (expense) 181,159 (961 ) (1,003 ) (2,014 ) Equity earnings (loss) in subsidiary (123,142 ) 51,401 4,288 32,230 Non-interest income: Gain on securities transactions 236 — (60 ) — Change in fair value of equity securities 65 — — — Other non-interest income 139 — — — Total non-interest income 440 — (60 ) — Non-interest expense Charitable contribution to foundation — 34,767 — — Merger-related expenses 1,807 — — — Other non-interest expense 1,955 425 2 460 Total non-interest expense 3,762 35,192 2 460 Income before income tax benefit 54,695 15,248 3,223 29,756 Income tax benefit 22 7,488 455 1,316 Net income 54,717 22,736 3,678 31,072 Other comprehensive income (loss) 3,710 (6,487 ) (19,230 ) 5,178 Comprehensive income (loss) $ 58,427 $ 16,249 $ (15,552 ) $ 36,250 (19) Parent-only Financial Information (continued) Statements of Cash Flows Years Ended December 31, Three Months Ended December 31, Year Ended September 30, 2019 2018 2017 2017 (In thousands) Cash flows from operating activities: Net income $ 54,717 $ 22,736 $ 3,678 $ 31,072 Adjustments to reconcile net income to net cash provided by operating activities: Amortization of debt issuance costs — 890 14 53 Amortization of intangible assets (71 ) — — — (Gain) loss on securities transactions (236 ) — 60 — Change in fair value of equity securities (65 ) — — — Deferred tax (benefit) expense 1,453 (6,086 ) 42 1 (Decrease) increase in other assets (2,026 ) 1,515 (494 ) 1,404 Increase (decrease) in accrued expenses and other liabilities 3,515 (1,498 ) 989 62 Contribution of common stock to Columbia Bank Foundation — 34,767 — — Equity in undistributed earnings (loss) of subsidiary 123,142 (51,401 ) (4,288 ) (32,295 ) Net cash provided by operating activities 180,429 923 1 297 Cash flows from investing activities: Capital contribution to subsidiary — (246,420 ) — — Proceeds from sales of debt securities available for sale — — 92 — Proceeds from sale of equity securities 1,065 — — — Proceeds from paydowns/maturities/calls of debt securities available for sale 500 1,601 10 — Purchases of debt securities available for sale — (414 ) — — Purchase of equity securities (416 ) — — — Loan to ESOP — (45,428 ) — — Repayment of loan receivable from Bank 1,457 989 — — Net cash paid in acquisition (135,410 ) — — — Net cash (used in) provided by investing activities (132,804 ) (289,672 ) 102 — Cash flows from financing activities: Payments on trust preferred securities — (51,547 ) — — Issuance of common stock in initial public offering — 492,428 — — Purchase of treasury stock (55,309 ) — — — Issuance of common stock allocated to restricted stock award grants 21,687 — — — Restricted stock forfeitures (736 ) — — — Issuance of treasury stock allocated to restricted stock award grants 1,269 — — — Net cash (used in) provided by financing activities (33,089 ) 440,881 — — (19) Parent-only Financial Information (continued) Statements of Cash Flows Years Ended December 31, Three Months Ended December 31, Year Ended September 30, 2019 2018 2017 2017 (In thousands) Net increase in cash and cash equivalents $ 14,536 — $ 152,132 — $ 103 $ 297 Cash and cash equivalents at beginning of year 153,833 1,701 1,598 1,301 Cash and cash equivalents at end of period $ 168,369 $ 153,833 $ 1,701 $ 1,598 Acquisition: Non-cash assets acquired: Debt securities available for sale $ 1,998 $ — $ — $ — Equity securities 208 — — — Other assets 1,492 — — — Total non-cash assets acquired $ 3,698 $ — $ — $ — Liabilities assumed: Borrowings $ 23,901 $ — $ — $ — Total liabilities assumed $ 23,901 $ — $ — $ — Net non-cash liabilities acquired $ (20,203 ) $ — $ — $ — Net cash acquired in acquisition $ 884 $ — $ — $ —

Other Comprehensive Income (Los

Other Comprehensive Income (Loss)	12 Months Ended
Other Comprehensive Income (Loss)	Dec. 31, 2019
Equity [Abstract]
Other Comprehensive Income (Loss)	Other Comprehensive Income (Loss) The following tables present the components of other comprehensive income (loss), both gross and net of tax, for the years ended December 31, 2019 and 2018 , September 30, 2017, and the three months ended December 31, 2017 : For the Years Ended December 31, 2019 2018 Before Tax Tax Effect After Tax Before Tax Tax Effect After Tax (In thousands) Components of other comprehensive income (loss): Unrealized gains (losses) on debt securities available for sale: $ 26,601 $ (5,534 ) $ 21,067 $ (7,224 ) $ 1,446 $ (5,778 ) Accretion of unrealized gain (loss) on debt securities reclassified as held to maturity 11 (2 ) 9 (13 ) — (13 ) Reclassification adjustment for gains included in net income 2,612 (601 ) 2,011 (116 ) 24 (92 ) 29,224 (6,137 ) 23,087 (7,353 ) 1,470 (5,883 ) Derivatives: Unrealized (loss) on swap contracts accounted for as cash flow hedges (8,193 ) 1,725 (6,468 ) (2,825 ) 595 (2,230 ) Employee benefit plans: Amortization of prior service cost included in net income (56 ) 12 (44 ) (623 ) 132 (491 ) Reclassification adjustment of actuarial net (loss) gain included in net income (3,709 ) 779 (2,930 ) 2,526 (530 ) 1,996 Change in funded status of retirement obligations (12,576 ) 2,641 (9,935 ) 897 (776 ) 121 (16,341 ) 3,432 (12,909 ) 2,800 (1,174 ) 1,626 Total other comprehensive income (loss) $ 4,690 $ (980 ) $ 3,710 $ (7,378 ) $ 891 $ (6,487 ) (20) Other Comprehensive Income (Loss) (continued) For the Three Months Ended December 31, For the Year Ended September 30, 2017 2017 Before Tax Tax Effect After Tax Before Tax Tax Effect After Tax (In thousands) Components of other comprehensive income (loss): Unrealized gains (losses) on debt securities available for sale: $ (3,012 ) $ (119 ) $ (3,131 ) $ (17,877 ) $ 6,379 $ (11,498 ) Accretion of unrealized (loss) gain on debt securities reclassified as held to maturity (2 ) (56 ) (58 ) 12 (4 ) 8 Reclassification adjustment for gains included in net income 60 (13 ) 47 2,626 (937 ) 1,689 (2,954 ) (188 ) (3,142 ) (15,239 ) 5,438 (9,801 ) Derivatives: Unrealized gain on swap contracts accounted for as cash flow hedges 192 (30 ) 162 95 (33 ) 62 Employee benefit plans: Amortization of prior service cost included in net income (24 ) (19 ) (43 ) (114 ) 41 (73 ) Reclassification adjustment of actuarial net (loss) gain included in net income (9 ) (94 ) (103 ) 11,806 (4,213 ) 7,593 Change in funded status of retirement obligations (9,024 ) 3,354 (5,670 ) 11,503 (4,106 ) 7,397 Tax effects resulting from the adoption of ASU No. 2018-02 — (10,434 ) (10,434 ) — — — (9,057 ) (7,193 ) (16,250 ) 23,195 (8,278 ) 14,917 Total other comprehensive (loss) income $ (11,819 ) $ (7,411 ) $ (19,230 ) $ 8,051 $ (2,873 ) $ 5,178 The Company, in accordance with ASU No. 2018-02, elected to reclassify the income tax effects of the Tax Act from accumulated other comprehensive (loss) income to retained earnings for the three months ended December 31, 2017. (20) Other Comprehensive Income (Loss) (continued) The following tables present the changes in the components of accumulated other comprehensive income (loss), net of tax, for the years ended December 31, 2019 and 2018 , September 30, 2017, and the three months ended December 31, 2017 : For the Years Ended December 31, 2019 2018 Unrealized (Losses) Gains on Debt Securities Available for Sale Unrealized (Losses) on Swaps Employee Benefit Plans Accumulated Other Comprehensive (Loss) Unrealized (Losses) on Debt Securities Available for Sale Unrealized Gains (Losses) on Swaps Employee Benefit Plans Accumulated Other Comprehensive (Loss) (In thousands) Balance at beginning of period $ (13,162 ) $ (2,006 ) $ (56,729 ) $ (71,897 ) $ (7,279 ) $ 224 $ (58,355 ) $ (65,410 ) Effect of the adoption of ASU 2016-01 (548 ) (548 ) — — — — Balance at January 1, 2019 $ (13,710 ) $ (2,006 ) $ (56,729 ) $ (72,445 ) $ (7,279 ) $ 224 $ (58,355 ) $ (65,410 ) Current period changes in other comprehensive income (loss) 23,087 (6,468 ) (12,909 ) 3,710 (5,883 ) (2,230 ) 1,626 (6,487 ) Total other comprehensive income (loss) $ 9,377 $ (8,474 ) $ (69,638 ) $ (68,735 ) $ (13,162 ) $ (2,006 ) $ (56,729 ) $ (71,897 ) For the Three Months Ended December 31, For the Year Ended September 30, 2017 2017 Unrealized (Losses) Gains on Debt Securities Available for Sale Unrealized Gains on Swaps Employee Benefit Plans Accumulated Other Comprehensive (Loss) Unrealized (Losses) Gains on Debt Securities Available for Sale Unrealized Gains on Swaps Employee Benefit Plans Accumulated Other Comprehensive (Loss) (In thousands) Balance at beginning of period $ (4,137 ) $ 62 $ (42,105 ) $ (46,180 ) $ 5,664 $ — $ (57,022 ) $ (51,358 ) Current period changes in other comprehensive (loss) income (1,828 ) 122 (5,816 ) (7,522 ) (9,801 ) 62 14,917 5,178 Reclassification of tax effects resulting from the adoption of ASU No. 2018-02 (1,314 ) 40 (10,434 ) (11,708 ) — — — — Total other comprehensive income (loss) $ (7,279 ) $ 224 $ (58,355 ) $ (65,410 ) $ (4,137 ) $ 62 $ (42,105 ) $ (46,180 ) (20) Other Comprehensive Income (Loss) (continued) The following tables reflect amounts reclassified out of accumulated other comprehensive income (loss) in the Consolidated Statements of Income and the affected line item in the statement where net income is presented for the years ended December 31, 2019 and 2018 , September 30, 2017, and the three months ended December 31, 2017 : Accumulated Other Comprehensive (Loss) Income Components For the Years Ended December 31, Affected line items in the Consolidated Statements of Income 2019 2018 (In thousands) Reclassification adjustment for gains (losses) included in net income $ 2,612 $ (116 ) Gain (loss) on securities transactions Reclassification adjustment of actuarial net (loss) gain included in net income (3,709 ) 2,526 Other non-interest expense Total before tax (1,097 ) 2,410 Income tax (benefit) 178 (506 ) Net of tax $ (919 ) $ 1,904 Accumulated Other Comprehensive (Loss) Income Components For the Three Months Ended December 31, For the Year Ended September 30, Affected line items in the Consolidated Statements of Income 2017 2017 (In thousands) Reclassification adjustment for gains included in net income $ 60 $ 2,626 Gain on securities transactions Reclassification adjustment of actuarial net (loss) gain included in net income (9 ) 11,806 Other non-interest expense Total before tax 51 14,432 Income tax (benefit) (107 ) (5,150 ) Net of tax $ (56 ) $ 9,282

Derivatives and Hedging Activit

Derivatives and Hedging Activities	12 Months Ended
Derivatives and Hedging Activities	Dec. 31, 2019
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Derivatives and Hedging Activities	Derivatives and Hedging Activities The Company uses derivative financial instruments as components of its market risk management, principally to manage interest rate risk. Certain derivatives are entered into in connection with transactions with commercial customers. Derivatives are not used for speculative purposes. All derivatives are recognized as either assets or liabilities in the Consolidated Statements of Financial Condition, reported at fair value and presented on a gross basis. Until a derivative is settled, a favorable change in fair value results in an unrealized gain that is recognized as an asset, while an unfavorable change in fair value results in an unrealized loss that is recognized as a liability. The Company generally applies hedge accounting to its derivatives used for market risk management purposes. Hedge accounting is permitted only if specific criteria are met, including a requirement that a highly effective relationship exists between the derivative instrument and the hedged item, both at inception of the hedge and on an ongoing basis. Changes in the fair value of effective fair value hedges are recognized in current earnings (with the change in fair value of the hedged asset or liability also recognized in earnings). Changes in the fair value of effective cash flow hedges are recognized in other comprehensive income (loss) until earnings are affected by the variability in cash flows of the designated hedged item. Ineffective portions of hedge results are recognized in current earnings. Changes in the fair value of derivatives for which hedge accounting is not applied are recognized in current earnings. The Company formally documents at inception all relationships between the derivative instruments and the hedged items, as well as its risk management objectives and strategies for undertaking the hedge transactions. This process includes linking all derivatives that are designated as hedges to specific assets and liabilities, or to specific firm commitments. The Company also formally assesses, both at inception of the hedge and on an ongoing basis, whether the derivatives that are used in hedging transactions are highly effective in offsetting changes in the fair values or cash flows of the hedged items. If it is determined that a derivative is not highly effective or has ceased to be a highly effective hedge, the Company would discontinue hedge accounting prospectively. Gains or losses resulting from the termination of a derivative accounted for as a cash flow hedge remain in other comprehensive income (loss) and is (accreted) amortized to earnings over the remaining period of the former hedging relationship. Certain derivative financial instruments are offered to certain commercial banking customers to manage their risk of exposure and risk management strategies. These derivative instruments consist primarily of currency forward contracts and interest rate swap contracts. The risk associated with these transactions is mitigated by simultaneously entering into similar transactions having essentially offsetting terms with a third party. In addition, the Company executes interest rate swaps with third parties in order to hedge the interest rate risk of short-term FHLB advances. Currency Forward Contracts. At December 31, 2019 and 2018, the Company had no currency forward contracts in place with commercial banking customers. Interest Rate Swaps. At December 31, 2019 the Company had interest rate swaps in place with 22 commercial banking customers executed by offsetting interest rate swaps with third parties, with an aggregated notional amount of $169.9 million . At December 31, 2018 , the Company had interest rate swaps in place with three commercial banking customers executed by offsetting interest rate swaps with third parties, with an aggregated notional amount of $ 36.6 million . These derivatives are not designated as hedges and are not speculative. These interest rate swaps do not meet hedge accounting requirements. At December 31, 2019 and 2018 , the Company had 29 and 24 interest rate swaps with notional amounts of $410.0 million and $320.0 million , respectively, hedging certain FHLB advances. These interest rate swaps meet the hedge accounting requirements. Interest rate swaps designated as cash flow hedges involve receipt of variable amounts from a counter-party in exchange for the Company making fixed-rate payments over the life of the arrangements without the exchange of the underlying notional amount. For the years ended December 31, 2019 and 2018 , September 30, 2017, and the three months ended December 31, 2017 , the Company did not record any hedge ineffectiveness associated with these contracts. (21) Derivatives and Hedging Activities (continued) The tables below present the fair value of the Company’s derivative financial instruments as well as their classification in the Consolidated Statements of Financial Condition at December 31, 2019 and 2018 : December 31, 2019 Asset Derivative Liability Derivative Consolidated Statements of Financial Condition Fair Value Consolidated Statements of Financial Condition Fair Value (In thousands) Derivatives: Interest rate swaps Other Assets $ 185 Other Liabilities $ 11,546 Total derivative instruments $ 185 $ 11,546 December 31, 2018 Asset Derivative Liability Derivative Consolidated Statements of Financial Condition Fair Value Consolidated Statements of Financial Condition Fair Value (In thousands) Derivatives: Interest rate swaps Other Assets $ 1,342 Other Liabilities $ 3,944 Total derivative instruments $ 1,342 $ 3,944 For the years ended December 31, 2019 and 2018 gains (losses) of $204,000 and $(52,000) respectively, were recorded for changes in fair value of interest rate swaps with third parties. For the year ended September 30, 2017, and the three months ended December 31, 2017, no gains or losses were recorded for these transactions. At December 31, 2019 and 2018 , accrued interest was $344,000 and $65,000 , respectively. The Company has agreements with counterparties that contain a provision that if the Company defaults on any of its indebtedness, including default where repayment of the indebtedness has not been accelerated by the lender, then the Company could also be declared in default of its derivative obligations. At December 31, 2019 , the termination value of derivatives in a net liability position, which includes accrued interest, was $17.5 million . The Company has collateral posting thresholds with certain of its derivative counterparties, and has posted collateral of $18.4 million

Revenue Recognition

Revenue Recognition	12 Months Ended
Revenue Recognition	Dec. 31, 2019
Revenue from Contract with Customer [Abstract]
Revenue Recognition	Revenue Recognition On January 1, 2019, the Company adopted ASU 2014-09 Revenue from Contracts with Customers (Topic 606) and all subsequent ASUs that modified Topic 606. The Company performed a review and assessment of all revenue streams, the related contracts with customers, and the underlying performance obligations in those contracts. This guidance does not apply to revenue associated with financial instruments, including interest income on loans and securities, which comprise the majority of the Company's revenue. Revenue-generating activities that are within the scope of Topic 606, are components of non-interest income. These revenue streams can generally be classified as demand deposit account fees, title insurance fees and other fees. The Company, using a modified retrospective transition approach, determined that there was no cumulative effect adjustment to retained earnings as a result of adopting the new standard, nor did the standard have a material impact on our consolidated financial statements including the timing or amounts of revenue recognized. (22) Revenue Recognition (continued) The following table presents non-interest income, segregated by revenue streams in-scope and out-of-scope of Topic 606, for the years ended December 31, 2019 and 2018 . For the Years Ended December 31, 2019 2018 (In thousands) Non-interest income In-scope of Topic 606: Demand deposit account fees $ 4,478 $ 3,987 Title insurance fees 4,981 4,297 Other non-interest income 4,844 4,679 Total in-scope non-interest income 14,303 12,963 Total out-of-scope non-interest income 17,333 8,725 Total non-interest income $ 31,636 $ 21,688 Demand deposit account fees include monthly maintenance fees and service charges. These fees are generally derived as a result of either transaction-based or serviced-based services. The Company's performance obligation for these services is generally satisfied, and revenue recognized, at the time the transaction is completed or the service rendered. Fees for these services are generally received from the customer either at the time of the transaction or monthly. Title insurance fees are generally recognized at the time the transaction closes or when the service is rendered. Other non-interest income includes check printing fees, traveler's check fees, gift card fees, branch service fees, overdraft fees, account analysis fees, other deposit related fees, wealth management related fee income which includes annuity fees, brokerage commissions, and asset management fees. Wealth management related fee income represent fees earned from customers as consideration for asset management and investment advisory services provided by a third party. The Company's performance obligation is generally satisfied monthly and the resulting fees are recognized monthly based upon the month-end market value of the assets under management and the applicable fee rate. The Company does not earn performance-based incentives. The Company's performance obligation for these transaction-based services are generally satisfied, and related revenue recognized, at the time the transaction closes or when the service is rendered or a point in time when the service is completed. Also included in other fees are debit card and ATM fees which are transaction-based. Debit card revenue is primarily comprised of interchange fees earned when a customer's Company card is processed through a card payment network. ATM fees are largely generated when a Company cardholder uses a non-Company ATM, or a non-Company cardholder uses a Company ATM. The Company's performance obligation for these services is satisfied when the service is rendered. Payment is generally received at time of transaction or monthly. Out-of-scope non-interest income primarily consists of income from bank-owned life insurance, loan prepayment and servicing fees, net fees loan level swaps, gains and losses on the sale of loans and securities, and changes in the fair value of equity securities. None of these revenue streams are subject to the requirements of Topic 606.

Subsequent Events

Subsequent Events	12 Months Ended
Subsequent Events	Dec. 31, 2019
Subsequent Events [Abstract]
Subsequent Events	Subsequent Events The Company has evaluated events subsequent to December 31, 2019 and through the financial statement issuance date of March 2, 2020

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	12 Months Ended
Summary of Significant Accounting Policies (Policies)	Dec. 31, 2019
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Principles of Consolidation	Principles of Consolidation The accompanying consolidated financial statements include the accounts of Columbia Financial, Inc., its wholly-owned subsidiary, Columbia Bank (the "Bank") and the Bank's wholly-owned subsidiaries, Columbia Investment Services, Inc., 2500 Broadway Corp. 1901 Residential Management Co. LLC, Plaza Financial Services, Inc., First Jersey Title Services, Inc., Real Estate Management Corp. LLC, 1901 Commercial Management Co. LLC, Stewardship Realty LLC, and CSB Realty Corp. (collectively, the “Company”). In consolidation, all intercompany accounts and transactions are eliminated. Certain reclassifications have been made in the consolidated financial statements to conform with current year classifications. The Company also owns 100% of the common stock of Columbia Financial Capital Trust I (the "Trust"). The Trust was used to issue trust preferred securities. In accordance with Accounting Standards Codification ("ASC") Topic 810, Consolidation , the Trust was classified as a variable interest entity and did not satisfy the conditions for consolidation. Accordingly, the Trust was treated as an unconsolidated subsidiary. In August 2018, the Company redeemed, in full $51.5 million of junior subordinated debt securities, which represented 100% of the assets of the Trust. The Bank's wholly owned subsidiary, Stewardship Realty, LLC, incorporated as a New Jersey corporation in 2005 was acquired in the Company's merger with Stewardship in November 2019. It is a service corporation originally organized to hold and manage property in Midland Park which was occupied by Atlantic Stewardship Bank. The Company also owns 100% of the common stock of Stewardship Statutory Trust I, which is a trust incorporated in Delaware which was also acquired in the Company's merger with Stewardship in November 2019. In accordance with ASC Topic 810, Consolidation , (2) Summary of Significant Accounting Policies (continued) this Trust was classified as a variable interest entity and did not satisfy the conditions for consolidation. Accordingly, this Trust, which owns $7.0 million of trust preferred securities, which represented 100%
Basis of Financial Statement Presentation	Basis of Financial Statement Presentation The consolidated financial statements of the Company have been prepared in conformity with U.S. generally accepted accounting principles (“GAAP”). In preparing the consolidated financial statements, management is required to make estimates and assumptions about future events. These estimates and the underlying assumptions affect the reported amounts of assets and liabilities and disclosures about contingent assets and liabilities as of the dates of the consolidated statements of financial condition, and revenues and expenses for the periods then ended. Such estimates are used in connection with the determination of the adequacy of the allowance for loan losses, evaluation of goodwill for impairment, evaluation of other-than-temporary impairment on securities, evaluation of the need for valuation allowances on deferred tax assets, and determination of liabilities related to retirement and other post-retirement benefits, among others. These estimates and assumptions are based on management’s best estimates and judgment. Management evaluates its estimates and assumptions on an ongoing basis using historical experience and other factors, including the current economic environment, which management believes to be reasonable under the circumstances. Such estimates and assumptions are adjusted when facts and circumstances dictate. Illiquid credit markets, volatile securities markets, and declines in the housing market and the economy generally have combined to increase the uncertainty inherent in such estimates and assumptions. As future events and their effects cannot be determined with precision, actual results could differ significantly from these estimates. Changes in estimates resulting from continuing changes in the economic environment will be reflected in the consolidated financial statements in future periods.
Cash and Cash Equivalents	Cash and Cash Equivalents
Securities	Securities Securities are classified as available for sale and held to maturity. Management determines the appropriate classification of securities at the time of purchase. If the Company has the intent to hold securities until maturity, these securities are classified as held to maturity and reported at amortized cost. If the Company does not have the intent to hold securities until maturity, these securities are classified as available for sale. The available for sale securities portfolio is carried at estimated fair value, with any unrealized holding gains or losses, net of taxes, reported as a separate component of accumulated other comprehensive income or loss in Stockholders' Equity. The fair values of these securities are based on market quotations or matrix pricing as discussed in Note 16. Management conducts a periodic review and evaluation of the securities portfolio to determine if any declines in the fair value of securities are other-than-temporary. In this evaluation, if such decline were deemed other-than temporary, management would measure the total credit-related component of the unrealized loss, and recognize that portion of the loss as a charge to current period earnings. The remaining portion of the unrealized loss would be recognized as an adjustment to accumulated other comprehensive income. The fair value of the securities portfolio is significantly affected by changes in interest rates. In general, as interest rates rise, the fair value of fixed-rate securities decreases and as interest rates fall, the fair value of fixed-rate securities increases. The Company determines if it has the intent to sell these securities or if it more likely than not that the Company would be required to sell the securities before the anticipated recovery. If either exists, the decline in value is considered other-than-temporary and would be recognized as an expense in the current period. Premiums and discounts on securities are generally amortized and accreted to income over the contractual lives of the securities using the level-yield method. Premiums on callable securities are amortized to the first call date. Dividend and interest income are recognized when earned. Realized gains and losses are recognized when securities are sold or called based on the specific identification method. In the ordinary course of business, securities are pledged as collateral in conjunction with the Company’s borrowings, lines of credit, and public funds on deposit.
Federal Home Loan Bank Stock	Federal Home Loan Bank Stock The Bank, as a member of the Federal Home Loan Bank of New York (the "FHLB"), is required to hold shares of capital stock of the FHLB based on its activities, primarily its outstanding borrowings. The Bank carries the investment at cost, or par value, which approximates fair value.
Loans Held-for-Sale	Loans Held-for-Sale Loans held-for-sale consist of conforming loans originated and intended for sale in the secondary market. These loans are carried at the lower of cost or estimated fair value, less costs to sell, as determined on an individual loan basis. Net unrealized losses, if any, are recognized in a valuation allowance through charges to earnings. Origination fees and costs on loans held-for-sale are deferred and recognized as a component of the gain or loss on sale. Loans held-for-sale are generally sold with loan servicing rights retained by the Bank.
Loans Receivable	Loans Receivable Loans receivable are carried at unpaid principal balances adjusted by unamortized premiums and unearned discounts, net deferred origination fees and costs less the allowance for loan losses. The Bank defers loan origination fees and certain direct loan origination costs and accretes such amounts as an adjustment to the yield over the expected lives of the related loans using the level-yield method. Interest income on loans is accrued and credited to income as earned. Premiums and discounts on loans purchased are amortized or accreted as an adjustment to yield over the contractual lives of the related loans using methodologies which approximate the level-yield method. A loan is considered delinquent when payment has not been received within 30 days of its contractual due date. Generally, the accrual of income on loans is discontinued when they are past due 90 days or more as to contractual obligations, or other circumstances indicate that collection is questionable. When a loan is placed on non-accrual status, any interest accrued but not received is reversed against interest income. Payments received on a non-accrual loan are either applied to the outstanding principal balance or recorded as interest income, depending on an assessment of the ability to collect the loan. Non-accruing loans are returned to accrual status after there has been a sustained period of repayment performance (generally six consecutive months of payment) and both principal and interest are deemed collectible. Loans are generally charged off after an analysis is completed which indicates that collectability of the full principal balance is in doubt. An impaired loan is defined as a loan for which it is probable, based on current information, that the Bank will not collect all amounts due under the contractual terms of the loan agreement. The Bank considers the population of loans in its impairment analysis to include all multifamily and commercial real estate, construction, and commercial business loans with an outstanding balance greater than $500,000
Allowance for Loan Losses	Purchased Credit-Impaired ("PCI") Loans Purchased credit impaired loans are loans acquired through acquisitions at a discount primarily due to deteriorated credit quality. PCI loans are recorded at fair value at the date of acquisition with no carryover of the related allowance for credit losses. Determining the fair value of loans involves estimating the amount and timing of principal and interest cash flows expected to be collected on the loans discounting those cash flows at a market rate of interest. The excess of cash flows expected at acquisition over the estimated fair value is referred to as the accretable yield and is recognized into interest income over the remaining life of the loan. The difference between contractually required payments at acquisition and the cash flows expected to be collected at acquisition is referred to as the nonaccretable yield. The nonaccretable yield represents estimated future credit losses expected to be incurred over the life of the loan. Subsequent decreases to the expected cash flows require us to evaluate the need for an allowance for credit losses. Subsequent improvements in expected cash flows result in the reversal of a corresponding amount of the nonacretable yield which we then reclassify as accretable yield that is recognized into interest income over the remaining life of the loan using the interest method. The evaluation of the amount of future cash flows that is expected to be collected is performed in a similar manner used to determine the allowance for (2) Summary of Significant Accounting Policies (continued) loan losses. Any charge-offs of principal on acquired loans would first be applied against the nonaccretable yield portion of the fair value adjustment. Allowance for Loan Losses Losses on loans are charged to the allowance for loan losses. Additions to this allowance are made by recoveries of loans previously charged off and by a provision charged to expense. The determination of the balance of the allowance for loan losses is based on an analysis of the loan portfolio, economic conditions, historical loan loss experience and other factors that warrant recognition in providing an adequate allowance. Estimates and judgments required to establish the allowance include: overall economic environment; value of collateral; strength of guarantors; loss exposure in the event of default; the amount and timing of future cash flows on impaired loans; and determination of loss factors applied to the portfolio segments. These estimates are susceptible to significant change. Management regularly reviews loss experience within the portfolio and monitors current economic conditions and other factors related to the collectability of the loan portfolio. While management uses available information, future additions to the allowance may be necessary based on changes in economic conditions in the Bank's market area. In addition, regulatory agencies, as an integral part of their examination process, periodically review the adequacy of the Bank's allowance for loan losses as an integral part of their examination. Such agencies may require the Bank to recognize additions to the allowance or additional write-downs based on their judgments about information available to them at the time of their examination. Although management uses the best information available, the level of the allowance for loan losses remains an estimate that is subject to significant uncertainties.
Troubled Debt Restructuring	Troubled Debt Restructuring Troubled debt restructured loans are those loans where the Company has granted a concession it would not otherwise consider because of economic or legal reasons pertaining to a debtor’s financial difficulties. A concession could include a reduced interest rate below a market rate, an extension of the term of the loan, or a combination of the two methods, but generally does not result in the forgiveness of principal or accrued interest. Not all concessions granted by the Company constitute a troubled debt restructuring. Once an obligation has been restructured and designated as a troubled debt restructuring, it continues to be designed as a restructured loan until paid in full. The Company records an impairment charge equal to the difference between the present value of expected future cash flows under the restructured terms discounted at the loan’s original effective interest rate, and the loan’s carrying value. Changes in the calculated impairment due to the passage of time are recorded as an adjustment to the allowance for loan losses. Restructured loans that were accruing prior to the restructuring, where income was reasonably assured subsequent to the restructuring, maintain their accrual status. Restructured loans for which collectability was not reasonably assured are placed on non-accrual status, interest accruals cease, and uncollected accrued interest is reversed and charged against current income. Non-accruing restructured loans may be returned to accrual status when there is a sustained period of repayment performance (generally six consecutive months of payments), and both principal and interest are deemed collectible.
Loans Sold and Serviced	Loans Sold and Serviced The Company has entered into Guarantor Swaps with Freddie Mac to improve its liquidity. In these types of transactions, the Company sells mortgage loans in exchange for Freddie Mac Mortgage Participation Certificates backed exclusively by the loans sold. The Company retains the servicing of these loans. The Company also periodically sells loans to investors and continues to service such loans for a fee. Gains or losses on the sale of loans are recorded on trade date using the specific-identification method.
Real Estate Owned	Real Estate Owned Real estate acquired through foreclosure or deed in lieu of foreclosure is carried at the lower of the recorded investment in the loan at the time of foreclosure or fair value, less estimated costs to sell. Fair value is generally based on recent appraisals. The excess, if any, of the loan amount over the fair value of the asset acquired is charged off against the allowance for loan losses at the date the property is acquired. Subsequent write-downs in the value of real estate owned, as well as holding costs, and any gains or losses realized upon sale of the property are recorded as incurred.
Office Properties and Equipment	Office Properties and Equipment Land is carried at cost. Office properties, land and building improvements, furniture and equipment, and leasehold improvements are carried at cost, less accumulated depreciation and amortization. Depreciation and amortization of office properties and equipment is computed on a straight-line basis over their estimated useful lives (generally 40 years for buildings, 10 to 20 years for land and building (2) Summary of Significant Accounting Policies (continued) improvements, 3 to 10 years
Bank-owned Life Insurance	Bank-owned Life Insurance ("BOLI")
Goodwill and Intangible Assets	Goodwill and Intangible Assets Intangible assets of the Bank consist of goodwill, core deposit intangibles and mortgage servicing rights. Goodwill represents the excess of the purchase price over the fair value of net assets acquired in purchase acquisitions. In accordance with GAAP, goodwill with an indefinite useful life is not amortized, but is evaluated for impairment on an annual basis, or more frequently if events or changes in circumstances indicate potential impairment between annual measurement dates. As permitted by GAAP, the Company prepares a qualitative assessment in determining whether goodwill may be impaired. The factors considered in the assessment include macroeconomic conditions, industry and market conditions and overall financial performance of the Company, among others. The Company completed its annual goodwill impairment test as of December 31, 2019 based upon its qualitative assessment of goodwill and concluded that goodwill was not impaired and no further quantitative analysis was warranted. Core deposit intangibles represent the balance of the core deposit intangibles ascribed to the value of deposit acquired by the Bank through the acquisition of Stewardship. Mortgage servicing rights are recorded when purchased or when originated mortgage loans are sold, with servicing rights retained. Mortgage servicing rights are amortized on an accelerated method based upon the estimated lives of the related loans, and generally adjusted for prepayments. Mortgage servicing rights are carried at the lower of amortized cost or fair value.
Post-retirement Benefits	Post-retirement Benefits The Company provides certain health care and life insurance benefits to eligible retired employees under a Post-retirement Plan, along with a split-dollar BOLI death benefit. The Company accrues the cost of retiree health care and other benefits during the employees’ period of active service. Effective January 1, 2019, the Post-retirement plan has been closed to new hires. Effective January 1, 2019, the Company implemented ASU 2017-07, Compensation - Retirement Benefits (Topic 715): Improving the Presentation of Net Periodic Pension Cost and Net Periodic Post-retirement Benefit Cost. Under this ASU, the FASB requires employers to report the service cost component in the same line item as other compensation costs arising from services rendered by the pertinent employees during the period. The other components of net periodic benefit cost are required to be presented in the Consolidated Statements of Income separately from the service cost component. This ASU is also required to be applied retrospectively to all periods presented.
Employee Benefits Plans	Employee Benefit Plans The Company maintains a single-employer tax-qualified defined benefit pension plan (the "Pension Plan") which covers full-time employees that satisfy the Pension Plan eligibility requirements. Effective October 1, 2018, employees hired by the Bank are not eligible to participate in the Company's Pension Plan as the plan has been closed to new employees as of that date. The Company's policy is to fund at least the minimum contribution required by the Employee Retirement Income Security Act of 1974. GAAP requires an employer to: (a) recognize in its statement of financial position the over-funded or under-funded status of a defined benefit post-retirement plan measured as the difference between the fair value of plan assets and the benefit obligation; (b) measure a plan’s assets and its obligations that determine its funded status at the end of the employer’s fiscal year (with limited exceptions); and (2) Summary of Significant Accounting Policies (continued) (c) recognize as a component of other comprehensive income (loss), net of tax, the actuarial gains and losses and the prior service costs and credits that arise during the period. The assets of the plan are primarily invested in fixed income and equity funds. The Company has a retirement income maintenance plan (the "RIM Plan") which is a non-qualified defined benefit plan which provides benefits to all employees of the Company if their benefits under the Pension Plan are limited by the Internal Revenue Code. The Company has a 401(k) plan covering substantially all employees of the Company. The Company may match a percentage of the first 3.00% to 4.50% contributed by participants. The Company's matching contribution, if any, is determined by the Board of Directors in its sole discretion. The Company has an Employee Stock Ownership Plan ("ESOP"). The funds borrowed by the ESOP from the Company to purchase the Company's common stock are being repaid from the Bank's contributions over a period of 20 years . The Company's common stock not allocated to participants is recorded as a reduction of stockholders' equity at cost. Compensation expense for the ESOP is based on the average price of the Company's stock and the amount of shares committed to be allocated during each period. The Company has a Supplemental Executive Retirement Plan ("SERP"). The SERP is a non-qualified plan which provides supplemental retirement benefits to eligible officers (those designated by the Board of Directors) of the Company who are prevented from receiving the full benefits contemplated by the ESOP's benefit formulas under tax law limits for tax-qualified plans. In addition, the Company maintains a stock based deferral plan (the "Stock Based Deferral Plan") for certain executives and directors. The Company records a deferred compensation equity account and corresponding contra-equity account for the cost of the shares held by the Stock Based Deferral and SERP Plans. The Company also maintains a non-qualified savings income maintenance deferred compensation plan (the "SIM Plan") that provides supplemental benefits to certain executives who are prevented from receiving the full benefits contemplated by the 401(k) Plan under tax law limits for tax-qualified plans, and a Deferred Compensation Plan for directors.
Derivatives	Derivatives The Company uses derivative financial instruments as components of its market risk management, principally to manage interest rate risk. Certain derivatives are entered into in connection with transactions with commercial customers. Derivatives are not used for speculative purposes. All derivatives are recognized as either assets or liabilities in the Consolidated Statements of Financial Condition, reported at fair value and presented on a gross basis. Until a derivative is settled, a favorable change in fair value results in an unrealized gain that is recognized as an asset, while an unfavorable change in fair value results in an unrealized loss that is recognized as a liability. The Company applies hedge accounting to its derivatives used for market risk management purposes if specific criteria are met, including a requirement that a highly effective relationship exists between the derivative instrument and the hedged item, both at inception of the hedge and on an ongoing basis. Changes in the fair value of effective fair value hedges are recognized in current earnings (with the change in fair value of the hedged asset or liability also recognized in earnings). Changes in the fair value of effective cash flow hedges are recognized in other comprehensive income (loss) until earnings are affected by the variability in cash flows of the designated hedged item. Ineffective portions of hedge results are recognized in current earnings. Changes in the fair value of derivatives for which hedge accounting is not applied are recognized in current earnings. The Company formally documents at inception all relationships between the derivative instruments and the hedged items, as well as its risk management objectives and strategies for undertaking the hedge transactions. This process includes linking all derivatives that are designated as hedges to specific assets and liabilities, or to specific firm commitments. The Company also formally assesses, both at inception of the hedge and on an ongoing basis, whether the derivatives that are used in hedging transactions are highly effective in offsetting changes in the fair values or cash flows of the hedged items. If it is determined that a derivative is not highly effective or has ceased to be a highly effective hedge, the Company would discontinue hedge accounting prospectively. Gains or losses resulting from the termination of a derivative accounted for as a cash flow hedge remain in other comprehensive income (loss) and is (accreted) amortized to earnings over the remaining period of the former hedging relationship. Certain derivative financial instruments are offered to certain commercial banking customers to manage their risk exposures and risk management strategies. These derivative instruments consist primarily of currency forward contracts and interest rate swap contracts. The risk associated with these transactions is mitigated by simultaneously entering into similar transactions having essentially offsetting terms with a third party.
Income Taxes	Income Taxes The Company and its subsidiaries file consolidated federal income tax returns. Federal income taxes are allocated to each entity based on their respective contributions to taxable income of the consolidated income tax returns. Beginning in 2019 as required by the State of New Jersey, the Company adopted combined income tax reporting for certain members of a commonly-controlled unitary business group. Prior to 2019, separate state income tax returns were filed for the Company and each of its qualifying subsidiaries. For the three months ended December 31, 2017, income tax expense included the impact of the enactment of the Tax Cuts and Jobs Act which reduced the maximum statutory federal income tax rate from 35% to 21%. This resulted in a charge to reduce the carrying value of the Company's net deferred income tax assets, which are included in the Consolidated Statements of Financial Condition. The Company records income taxes in accordance with ASC Topic 740, Income Taxes , using the asset and liability method. The amounts reflected on the Company's federal and state income tax returns differ from these provisions due principally to temporary differences in the reporting of certain items for consolidated financial statement reporting and income tax reporting purposes. Accordingly, deferred tax assets and liabilities: (i) are recognized for the expected future tax consequences of events that have been recognized in the financial statements or tax returns; (ii) are attributable to differences between the financial statement carrying amounts of existing assets and liabilities and their respective tax bases; and (iii) are measured using enacted tax rates expected to apply in the years when those temporary differences are expected to be recovered or settled. Where applicable, deferred tax assets are reduced by a valuation allowance for any portions determined not likely to be realized. The effect on deferred tax assets and liabilities of a change in tax rates is recognized in income tax expense in the period that includes the enactment date. The valuation allowance is adjusted, by a charge or credit to income tax expense, as changes in facts and circumstances warrant. Income taxes are allocated to the individual entities within the consolidated group based on the effective tax rate of the entity. The Company did not have any liabilities for uncertain tax positions or any known unrecognized tax benefits at December 31, 2019 and 2018 . The Company recognizes interest and penalties related to unrecognized tax benefits in income tax expense in the Consolidated Statements of Income. The Company did not recognize any interest and penalties during the years ended December 31, 2019 and 2018, September 31, 2017, and the three months ended December 31, 2017. On July 1, 2018, New Jersey enacted legislation which adds to the state’s 9.0% Corporation Business Tax rate (i) a 2.5% surtax for periods beginning in 2018 and 2019 and (ii) a 1.5% surtax for periods beginning in 2020 and 2021. These surtaxes apply to corporations with more than $1.0 million of net income allocated to New Jersey and expire beginning in 2022. Also, for periods beginning in 2017, New Jersey has reduced the dividends-received deduction from 100% to 95% for certain dividend income received by a corporation from a subsidiary that is at least 80% owned by the corporation. In addition, for periods beginning in 2019, as previously noted, New Jersey adopted combined income tax reporting for certain members of a commonly-controlled unitary business group, and issued guidance in December 2019 to clarify business entities to be included and excluded from this combined group.
Comprehensive Income (Loss)	Comprehensive Income (Loss) Comprehensive income (loss) consists of net income and other comprehensive income (loss). Other comprehensive income (loss) includes items recorded in equity, such as unrealized holding gains and losses on debt securities available for sale, the noncredit component of other than temporary impairment losses on debt securities, unrealized gains and losses on derivatives, and the unfunded status and reclassification of actuarial net (loss) gain associated with the Company's benefit plans. Comprehensive income is presented in a separate Consolidated Statements of Comprehensive Income (Loss).
Segment Reporting	Segment Reporting The Company’s operations are solely in the financial services industry and include providing traditional banking and other financial services to its customers. The Company operates primarily in New Jersey. Management makes operating decisions and assesses performance based on an ongoing review of the Company’s consolidated financial results. Therefore, the Company has a single operating segment for financial reporting purposes.
Earnings Per Share	Earnings Per Share ("EPS") Basic EPS is computed by dividing net income available to common shareholders by the weighted average number of common shares outstanding during the period. For purposes of calculating basic EPS, weighted average common shares outstanding excludes treasury stock, unallocated employee stock ownership plan shares that have not been committed for release and deferred compensation obligations required to be settled in shares of Company stock. Diluted EPS is computed using the same method as basic EPS and reflects the potential dilution which could occur if stock options and unvested shares were exercised and converted into common stock. (2) Summary of Significant Accounting Policies (continued) The potentially diluted shares would then be included in the weighted average number of shares outstanding for the period using the treasury stock method. Shares issued and reacquired during any period are weighted for the portion of the period that they were outstanding.
Stock Compensation Plans	Stock Compensation Plans Compensation expense related to stock options and non-vested restricted stock awards is based on the fair value of the award on the measurement date with expense recognized on a straight line basis over the requisite performance or service period. The fair value of stock options is estimated utilizing the Black-Scholes option pricing model. The fair value of non-vested restricted stock awards is generally the closing market price of the Company's common stock on the date of grant. The Company accounts for forfeitures as they occur.
Recent Accounting Pronouncements	Recent Accounting Pronouncements As an “emerging growth company” as defined in Title 1 of the Jumpstart Our Business Startups (JOBS) Act prior to December 31, 2019, the Company elected to use the extended transition period to delay the adoption of new or reissued accounting pronouncements applicable to public companies until such pronouncements were made applicable to private companies. Accounting Pronouncements Adopted In February 2018, the Financial Accounting Standards Board ("FASB") issued ASU No. 2018-02, Income Statement - Reporting Comprehensive Income (Topic 220) . The updated guidance allows a reclassification from accumulated other comprehensive income to retained earnings for the stranded tax effects resulting from the Tax Cuts and Jobs Act disclosed in Note 14. The purpose of the guidance is to improve the usefulness of the information reported to the financial statement users. The guidance is effective for all entities for fiscal years beginning after December 31, 2018 and interim periods within those fiscal years. Early adoption is permitted. The Company early adopted ASU No. 2018-02 for the period ended December 31, 2018 and the impact of the adoption resulted in a reclassification adjustment between accumulated other comprehensive income and retained earnings of $11.7 million . In March 2017, the FASB issued ASU No. 2017-07, Compensation - Retirement Benefits (Topic 715): Improving the Presentation of Net Periodic Pension Cost and Net Periodic Post-retirement Benefit Cost, which requires that companies disaggregate the service cost component from other components of net benefit cost. This update calls for companies that offer post-retirement benefits to present the service cost, which is the amount an employer has to set aside each quarter or fiscal year to cover the benefits, in the same line item with other current employee compensation costs. Other components of net benefit cost will be presented in the income statement separately from the service costs component and outside the subtotal of income from operations, if one is presented. The effective date for this ASU for the Company is fiscal years beginning after December 15, 2018, including interim periods within those fiscal years. The Company adopted this guidance effective January 1, 2019. See note 13 for additional disclosure regarding the impact of adoption of this ASU on the Company's consolidated financial statements. In August 2016, the FASB issued ASU No. 2016-15, Statement of Cash Flows (Topic 230): Classification of Certain Cash Receipts and Cash Payments, a new standard which addresses diversity in practice related to eight specific cash flow issues: debt prepayment or extinguishment costs, settlement of zero-coupon debt instruments or other debt instruments with coupon interest rates that are insignificant in relation to the effective interest rate of the borrowing, contingent consideration payments made after a business combination, proceeds from the settlement of insurance claims, proceeds from the settlement of corporate-owned life insurance policies (including bank-owned life insurance policies), distributions received from equity method investees, beneficial interests in securitization transactions and separately identifiable cash flows and application of the predominance principle. This guidance in the ASU is effective for the Company for fiscal years beginning after December 15, 2018, including interim periods within those fiscal years. Entities will apply the standard’s provisions using a retrospective transition method to each period presented. If it is impracticable to apply the amendments retrospectively for some of the issues, the amendments for those issues would be applied prospectively as of the earliest date practicable. The Company adopted this guidance effective January 1, 2019. The adoption of this ASU did not have a material impact on the Company's consolidated financial statements. In January 2016, the FASB issued ASU No. 2016-01, Financial Instruments- Overall: Recognition and Measurement of Financial Assets and Financial Liabilities. This guidance requires an entity to: (i) measure equity investments at fair value through net income, with certain exceptions; (ii) present in other comprehensive income the changes in instrument-specific credit risk for financial liabilities measured using the fair value option; (iii) present financial assets and financial liabilities by measurement category and form of financial asset; (iv) calculate the fair value of financial instruments for disclosure purposes based on an exit price; and (v) assess a valuation (2) Summary of Significant Accounting Policies (continued) Recent Accounting Pronouncements (cont'd) Accounting Pronouncements Adopted (cont'd) allowance on deferred tax assets related to unrealized losses on available-for-sale debt securities in combination with other deferred tax assets. This guidance provides an election to subsequently measure certain non-marketable equity investments at cost less any impairment and adjusted for certain observable price changes. The guidance also requires a qualitative impairment assessment of such equity investments and amends certain fair value disclosure requirements. The Company adopted this guidance effective January 1, 2019. As a result, $1.9 million of equity securities, as of December 31, 2018, were reclassified from securities available for sale, and presented as a separate line item on the Consolidated Statements of Financial Condition. The $548,000 after tax unrealized gain on these securities, at time of adoption, was reclassified from other comprehensive income (loss) to retained earnings, and is reflected in the consolidated statements of changes in stockholders' equity. For financial instruments that are measured at amortized cost, the Company measures fair value utilizing an exit price methodology. See note 20 for additional disclosure regarding the impact of adoption of this ASU on the Company's consolidated financial statements. In May 2014, the FASB issued ASU No. 2014-09, Revenue from Contracts with Customers. The objective of this amendment is to clarify the principles for recognizing revenue and to develop a common revenue standard for U.S. GAAP. This update affects any entity that either enters into contracts with customers to transfer goods or services or enters into contracts for the transfer of non-financial assets unless those contracts are in the scope of other standards. The guidance in the ASU was effective for the Company for fiscal years beginning after December 15, 2018. Subsequently, the FASB issued various amendments that were intended to improve and clarify the implementation guidance of ASU No. 2014-09 and had the same effective date as the original guidance. The Company's revenue is primarily comprised of net interest income on interest earning assets and liabilities and non-interest income. The scope of guidance explicitly excludes net interest income as well as other revenues associated with financial assets and liabilities, including loans, leases, securities and derivatives. The Company adopted this guidance effective January 1, 2019, after completing an evaluation of the Company's revenue streams and applicable revenue recognition, and concluded that there are no material changes related to the timing or amount of revenue recognition. The adoption of this guidance did not have a significant impact on the Company's consolidated financial statements, but resulted in additional footnote disclosures, including the disaggregation of certain categories of revenues. See note 22 for additional disclosure regarding the impact of adoption of this ASU on the Company's consolidated financial statements.

Acquisition of Stewardship Fi_2

Acquisition of Stewardship Financial Corporation (Tables)	12 Months Ended
Acquisition of Stewardship Financial Corporation (Tables)	Dec. 31, 2019
Business Combinations [Abstract]
Schedule of recognized identified assets acquired and liabilities assumed	The following table sets forth assets acquired and liabilities assumed in the Stewardship acquisition, at their estimated fair values as of the closing date of the transaction: November 1, 2019 Assets acquired: Cash and cash equivalents $ 105,006 Debt securities available for sale 51,710 Equity securities 1,073 Federal Home Loan Bank stock 3,716 Loans receivable 757,223 Accrued interest receivable 2,239 Office properties and equipment, net 6,815 Bank-owned life insurance 22,096 Deferred tax assets, net 3,534 Core deposit and other intangibles 7,467 Other assets 767 Total assets acquired 961,646 Liabilities assumed: Deposits $ 782,698 Borrowings 82,761 Advance payments by borrowers for taxes and insurance 356 Accrued expenses and other liabilities 14,584 Total liabilities assumed $ 880,399 Net assets acquired $ 81,247 Cash paid for purchase 136,294 Goodwill recorded at merger $ 55,047

Debt Securities Available for_2

Debt Securities Available for Sale (Tables)	12 Months Ended
Debt Securities Available for Sale (Tables)	Dec. 31, 2019
Investments, Debt and Equity Securities [Abstract]
Debt securities, available-for-sale	Debt s ecurities available for sale at December 31, 2019 and 2018 are summarized as follows: December 31, 2019 Amortized Cost Gross Unrealized Gains Gross Unrealized (Losses) Fair Value (In thousands) U.S. government and agency obligations $ 42,081 $ 321 $ (16 ) $ 42,386 Mortgage-backed securities and collateralized mortgage obligations 968,165 12,981 (1,265 ) 979,881 Municipal obligations 2,284 1 (1 ) 2,284 Corporate debt securities 68,613 945 (378 ) 69,180 Trust preferred securities 5,000 — (395 ) 4,605 $ 1,086,143 $ 14,248 $ (2,055 ) $ 1,098,336 December 31, 2018 Amortized Cost Gross Unrealized Gains Gross Unrealized (Losses) Fair Value (In thousands) U.S. government and agency obligations $ 54,821 $ 53 $ (717 ) $ 54,157 Mortgage-backed securities and collateralized mortgage obligations 934,631 2,812 (17,436 ) 920,007 Municipal obligations 987 — — 987 Corporate debt securities 54,493 129 (1,155 ) 53,467 Trust preferred securities 5,000 — (750 ) 4,250 $ 1,049,932 $ 2,994 $ (20,058 ) $ 1,032,868
Investments classified by contractual maturity date	The amortized cost and fair value of debt securities available for sale at December 31, 2019 , by contractual final maturity is shown below. Expected maturities may differ from contractual maturities due to prepayment or early call options exercised by the issuer. December 31, 2019 Amortized Cost Fair Value (In thousands) One year or less $ 31,901 $ 31,955 More than one year to five years 27,366 27,729 More than five years to ten years 53,235 53,669 More than ten years 5,476 5,102 117,978 118,455 Mortgage-backed securities and collateralized mortgage obligations 968,165 979,881 $ 1,086,143 $ 1,098,336 December 31, 2019 Amortized Cost Fair Value (In thousands) More than ten years $ 20,000 $ 19,960 Mortgage-backed securities and collateralized mortgage obligations 265,756 269,545 $ 285,756 $ 289,505
Debt securities, available-for-sale, unrealized loss position, fair value	The following table summarizes the fair value and gross unrealized losses of those securities that reported an unrealized loss at December 31, 2019 and 2018 and if the unrealized loss position was continuous for the twelve months prior to those respective dates: December 31, 2019 Less Than 12 Months 12 Months or Longer Total Fair Value Gross Unrealized (Losses) Fair Value Gross Unrealized (Losses) Fair Value Gross Unrealized (Losses) (In thousands) U.S. government and agency obligations $ 5,106 $ (13 ) $ 4,988 $ (3 ) $ 10,094 $ (16 ) Mortgage-backed securities and collateralized mortgage obligations 178,665 (946 ) 58,208 (319 ) 236,873 (1,265 ) Municipal obligations 696 (1 ) — — 696 (1 ) Corporate debt securities 2,588 (5 ) 4,627 (373 ) 7,215 (378 ) Trust preferred securities — — 4,605 (395 ) 4,605 (395 ) $ 187,055 $ (965 ) $ 72,428 $ (1,090 ) $ 259,483 $ (2,055 ) (4) Debt Securities Available for Sale (continued) December 31, 2018 Less Than 12 Months 12 Months or Longer Total Fair Value Gross Unrealized (Losses) Fair Value Gross Unrealized (Losses) Fair Value Gross Unrealized (Losses) (In thousands) U.S. government and agency obligations $ 14,668 $ (202 ) $ 29,437 $ (515 ) $ 44,105 $ (717 ) Mortgage-backed securities and collateralized mortgage obligations 176,614 (1,034 ) 509,397 (16,402 ) 686,011 (17,436 ) Corporate debt securities 26,480 (512 ) 9,358 (643 ) 35,838 (1,155 ) Trust preferred securities — — 4,250 (750 ) 4,250 (750 ) $ 217,762 $ (1,748 ) $ 552,442 $ (18,310 ) $ 770,204 $ (20,058 )

Debt Securities Held to Matur_2

Debt Securities Held to Maturity (Tables)	12 Months Ended
Debt Securities Held to Maturity (Tables)	Dec. 31, 2019
Investments, Debt and Equity Securities [Abstract]
Debt securities, held-to-maturity	Debt securities held to maturity at December 31, 2019 and 2018 are summarized as follows: December 31, 2019 Amortized Cost Gross Unrealized Gains Gross Unrealized (Losses) Fair Value (In thousands) U.S. government and agency obligations $ 20,000 $ 26 $ (66 ) $ 19,960 Mortgage-backed securities and collateralized mortgage obligations 265,756 4,048 (259 ) 269,545 $ 285,756 $ 4,074 $ (325 ) $ 289,505 December 31, 2018 Amortized Cost Gross Unrealized Gains Gross Unrealized (Losses) Fair Value (In thousands) U.S. government and agency obligations $ 23,404 $ 45 $ (208 ) $ 23,241 Mortgage-backed securities and collateralized mortgage obligations 238,739 28 (7,167 ) 231,600 $ 262,143 $ 73 $ (7,375 ) $ 254,841
Investments classified by contractual maturity date	The amortized cost and fair value of debt securities available for sale at December 31, 2019 , by contractual final maturity is shown below. Expected maturities may differ from contractual maturities due to prepayment or early call options exercised by the issuer. December 31, 2019 Amortized Cost Fair Value (In thousands) One year or less $ 31,901 $ 31,955 More than one year to five years 27,366 27,729 More than five years to ten years 53,235 53,669 More than ten years 5,476 5,102 117,978 118,455 Mortgage-backed securities and collateralized mortgage obligations 968,165 979,881 $ 1,086,143 $ 1,098,336 December 31, 2019 Amortized Cost Fair Value (In thousands) More than ten years $ 20,000 $ 19,960 Mortgage-backed securities and collateralized mortgage obligations 265,756 269,545 $ 285,756 $ 289,505
Schedule of unrealized loss on investments	The following table summarizes the fair value and gross unrealized losses of those securities that reported an unrealized loss at December 31, 2019 and 2018 and if the unrealized loss position was continuous for the twelve months prior to those respective dates: December 31, 2019 Less Than 12 Months 12 Months or Longer Total Fair Value Gross Unrealized (Losses) Fair Value Gross Unrealized (Losses) Fair Value Gross Unrealized (Losses) (In thousands) U.S. government and agency obligations $ 9,934 $ (66 ) $ — $ — $ 9,934 $ (66 ) Mortgage-backed securities and collateralized mortgage obligations 27,911 (251 ) 772 (8 ) 28,683 (259 ) $ 37,845 $ (317 ) $ 772 $ (8 ) $ 38,617 $ (325 ) (5) Debt Securities Held to Maturity (continued) December 31, 2018 Less than 12 months 12 months or longer Total Fair Value Gross Unrealized (Losses) Fair Value Gross Unrealized (Losses) Fair Value Gross Unrealized (Losses) (In thousands) U.S. government and agency obligations $ — $ — $ 8,197 $ (208 ) $ 8,197 $ (208 ) Mortgage-backed securities and collateralized mortgage obligations 11,265 (69 ) 213,246 (7,098 ) 224,511 (7,167 ) $ 11,265 $ (69 ) $ 221,443 $ (7,306 ) $ 232,708 $ (7,375 )

Loans Receivable and Allowanc_2

Loans Receivable and Allowance for Loan Losses (Tables)	12 Months Ended
Loans Receivable and Allowance for Loan Losses (Tables)	Dec. 31, 2019
Receivables [Abstract]
Schedule of loans receivable	Loans receivable at December 31, 2019 and 2018 are summarized as follows: December 31, 2019 2018 (In thousands) Real estate loans: One-to-four family $ 2,077,079 $ 1,830,186 Multifamily and commercial 2,919,985 2,142,154 Construction 298,942 261,473 Commercial business loans 483,215 333,876 Consumer loans: Home equity loans and advances 388,127 393,492 Other consumer loans 1,960 1,108 Total gross loans 6,169,308 4,962,289 Purchased credit-impaired loans 7,021 — Net deferred loan costs, fees and purchased premiums and discounts 21,237 16,893 Loans receivable $ 6,197,566 $ 4,979,182 The following table provides information with respect to our non-accrual loans, excluding PCI loans at December 31, 2019 and 2018 : December 31, 2019 2018 (In thousands) Non-accrual loans: Real estate loans: One-to-four family $ 1,732 $ 819 Multifamily and commercial 716 154 Commercial business loans 3,686 911 Consumer loans: Home equity loans and advances 553 905 Total non-accrual loans $ 6,687 $ 2,789
Schedule of aging of loans receivable by portfolio segment	The following tables summarize the aging of loans receivable by portfolio segment, excluding PCI loans at December 31, 2019 and 2018 : December 31, 2019 30-59 Days 60-89 Days 90 Days or More Total Past Due Current Total (In thousands) Real estate loans: One-to-four family $ 6,249 $ 2,132 $ 1,638 $ 10,019 $ 2,067,060 $ 2,077,079 Multifamily and commercial 626 1,210 716 2,552 2,917,433 2,919,985 Construction — — — — 298,942 298,942 Commercial business loans 1,056 — 2,489 3,545 479,670 483,215 Consumer loans: Home equity loans and advances 1,708 246 405 2,359 385,768 388,127 Other consumer loans 3 — — 3 1,957 1,960 Total loans $ 9,642 $ 3,588 $ 5,248 $ 18,478 $ 6,150,830 $ 6,169,308 December 31, 2018 30-59 Days 60-89 Days 90 Days or More Total Past Due Current Total (In thousands) Real estate loans: One-to-four family $ 8,384 $ 1,518 $ 819 $ 10,721 $ 1,819,465 $ 1,830,186 Multifamily and commercial 1,870 1,425 154 3,449 2,138,705 2,142,154 Construction — — — — 261,473 261,473 Commercial business loans 208 279 911 1,398 332,478 333,876 Consumer loans: Home equity loans and advances 1,550 173 905 2,628 390,864 393,492 Other consumer loans — — — — 1,108 1,108 Total loans $ 12,012 $ 3,395 $ 2,789 $ 18,196 $ 4,944,093 $ 4,962,289
Schedule of PCI loans acquired	The following table presents information regarding the estimates of the contractually required payments, the cash flows expected to be collected, and the estimated fair value of the PCI loans acquired in the Stewardship acquisition as of November 1, 2019 (See Note 3 for more details): November 1, 2019 (In thousands) Contractually required principal and interest $ 9,286 Contractual cash flows not expected to be collected (non-accretable difference) (1,823 ) Expected cash flows to be collected 7,463 Interest component of expected cash flows (accretable yield) (556 ) Fair value of acquired loans $ 6,907 The following table presents changes in the accretable yield for PCI loans for the year ended December 31, 2019: December 31, 2019 (In thousands) Balance, beginning of period $ — Acquisition 556 Accretion (30 ) Net change in expected cash flows (15 ) Balance, end of period $ 511
Schedule of loans receivable by portfolio segment and impairment method	The following table summarizes loans receivable (including PCI loans) and allowance for loan losses by portfolio segment and impairment method at December 31, 2019 and 2018 : December 31, 2019 One-to-Four Family Multifamily and Commercial Construction Commercial Business Home Equity Loans and Advances Other Consumer Loans Unallocated Total (In thousands) Allowance for loan losses: Individually evaluated for impairment $ 484 $ 2 $ — $ 1,121 $ 14 $ — $ — $ 1,621 Collectively evaluated for impairment 13,296 22,978 7,435 14,715 1,655 9 — 60,088 Loans acquired with deteriorated credit quality — — — — — — — — Total $ 13,780 $ 22,980 $ 7,435 $ 15,836 $ 1,669 $ 9 $ — $ 61,709 Total loans: Individually evaluated for impairment $ 8,891 $ 2,599 $ — $ 5,178 $ 2,143 $ — $ — $ 18,811 Collectively evaluated for impairment 2,068,188 2,917,386 298,942 478,037 385,984 1,960 — 6,150,497 Loans acquired with deteriorated credit quality 429 4,866 — 1,726 — — — 7,021 Total gross loans $ 2,077,508 $ 2,924,851 $ 298,942 $ 484,941 $ 388,127 $ 1,960 $ — $ 6,176,329 (7) Loans Receivable and Allowance for Loan Losses (continued) December 31, 2018 One-to-Four Family Multifamily and Commercial Construction Commercial Business Home Equity Loans and Advances Other Consumer Loans Unallocated Total (In thousands) Allowance for loan losses: Individually evaluated for impairment $ 537 $ — $ — $ 366 $ 12 $ — $ — $ 915 Collectively evaluated for impairment 14,695 23,251 7,217 13,810 2,446 8 — 61,427 Total $ 15,232 $ 23,251 $ 7,217 $ 14,176 $ 2,458 $ 8 $ — $ 62,342 Total loans: Individually evaluated for impairment $ 9,048 $ 2,695 $ — $ 2,944 $ 3,100 $ — $ — $ 17,787 Collectively evaluated for impairment 1,821,138 2,139,459 261,473 330,932 390,392 1,108 — 4,944,502 Total gross loans $ 1,830,186 $ 2,142,154 $ 261,473 $ 333,876 $ 393,492 $ 1,108 $ — $ 4,962,289 The activity in the allowance for loan losses for the years ended December 31, 2019 and 2018 , September 30, 2017, and the three months ended December 31, 2017 are as follows: Years Ended December 31, Three Months Ended December 31, Year Ended September 30, 2019 2018 2017 2017 (In thousands) Balance at beginning of period $ 62,342 $ 58,178 $ 54,633 $ 51,867 Provision charged 4,224 6,677 3,400 6,426 Recoveries 496 707 188 584 Charge-offs (5,353 ) (3,220 ) (43 ) (4,244 ) Balance at end of period $ 61,709 $ 62,342 $ 58,178 $ 54,633 The activity in the allowance for loan losses by portfolio segment for the years ended December 31, 2019 and 2018 , September 30, 2017, and the three months ended December 31, 2017 are as follows: For the Year Ended December 31, 2019 One-to-Four Family Multifamily and Commercial Construction Commercial Business Home Equity Loans and Advances Other Consumer Loans Unallocated Total (In thousands) Balance at beginning of period $ 15,232 $ 23,251 $ 7,217 $ 14,176 $ 2,458 $ 8 $ — $ 62,342 Provision charged (credited) (429 ) (178 ) 216 5,250 (638 ) 3 — 4,224 Recoveries 30 10 2 404 50 — — 496 Charge-offs (1,053 ) (103 ) — (3,994 ) (201 ) (2 ) — (5,353 ) Balance at end of period $ 13,780 $ 22,980 $ 7,435 $ 15,836 $ 1,669 $ 9 $ — $ 61,709 For the Year Ended December 31, 2018 One-to-Four Family Multifamily and Commercial Construction Commercial Business Home Equity Loans and Advances Other Consumer Loans Unallocated Total (In thousands) Balance at beginning of period $ 19,991 $ 19,933 $ 5,217 $ 8,275 $ 4,576 $ 8 $ 178 $ 58,178 Provision charged (credited) (4,503 ) 3,445 1,997 7,860 (1,949 ) 5 (178 ) 6,677 Recoveries 334 2 3 240 122 6 — 707 Charge-offs (590 ) (129 ) — (2,199 ) (291 ) (11 ) — (3,220 ) Balance at end of period $ 15,232 $ 23,251 $ 7,217 $ 14,176 $ 2,458 $ 8 $ — $ 62,342 (7) Loans Receivable and Allowance for Loan Losses (continued) For the Three Months Ended December 31, 2017 One-to-Four Family Multifamily and Commercial Construction Commercial Business Home Equity Loans and Advances Other Consumer Loans Unallocated Total (In thousands) Balance at beginning of period $ 18,533 $ 18,029 $ 5,299 $ 8,480 $ 4,190 $ 8 $ 94 $ 54,633 Provision charged (credited) 1,473 1,906 (82 ) (373 ) 389 3 84 3,400 Recoveries 9 — — 171 6 2 — 188 Charge-offs (24 ) (2 ) — (3 ) (9 ) (5 ) — (43 ) Balance at end of period $ 19,991 $ 19,933 $ 5,217 $ 8,275 $ 4,576 $ 8 $ 178 $ 58,178 For the Year Ended September 30, 2017 One-to-Four Family Multifamily and Commercial Construction Commercial Business Home Equity Loans and Advances Other Consumer Loans Unallocated Total (In thousands) Balance at beginning of period $ 18,638 $ 17,390 $ 5,960 $ 5,721 $ 4,052 $ 11 $ 95 $ 51,867 Provision charged (credited) 1,029 1,644 (661 ) 3,183 1,219 13 (1 ) 6,426 Recoveries 268 75 — 182 59 — — 584 Charge-offs (1,402 ) (1,080 ) — (606 ) (1,140 ) (16 ) — (4,244 ) Balance at end of period $ 18,533 $ 18,029 $ 5,299 $ 8,480 $ 4,190 $ 8 $ 94 $ 54,633
Schedule of troubled debt restructuring	he following table presents the number of loans modified as TDRs for the years ended December 31, 2019 and 2018 , and September 30, 2017, along with their balances immediately prior to the modification date and post-modification. Post-modification recorded investment represents the net book balance immediately following modification. There we no loans modified during the three months ended December 31, 2017, For the Years Ended December 31, 2019 2018 No. of Loans Pre-modification Recorded Investment Post-modification Recorded Investment No. of Loans Pre-modification Recorded Investment Post-modification Recorded Investment (In thousands) Troubled Debt Restructurings Real estate loans: One-to-four family — $ — $ — 5 $ 801 $ 801 Multifamily and commercial — — — 1 65 65 Commercial business loans 1 4,095 4,095 — — — Consumer loans: Home equity loans and advances — — — 1 588 588 Total restructured loans 1 $ 4,095 $ 4,095 7 $ 1,454 $ 1,454 For the Year Ended September 30, 2017 No. of Loans Pre-modification Recorded Investment Post-modification Recorded Investment (Dollars in thousands) Troubled Debt Restructurings Real estate loans: One-to-four family 3 $ 548 $ 548 Multifamily and commercial 1 3,964 3,964 Commercial business loans 1 18 18 Consumer loans: Home equity loans and advances 2 248 248 Total restructured loans 7 $ 4,778 $ 4,778
Schedule of loans individually evaluated for impairment	At December 31, 2018 Recorded Investment Unpaid Principal Balance Specific Allowance (In thousands) With no allowance recorded: Real estate loans: One-to-four family $ 4,156 $ 5,307 $ — Multifamily and commercial 2,695 3,482 — Commercial business loans 2,285 2,374 — Consumer loans: Home equity loans and advances 2,511 2,866 — 11,647 14,029 — With a specific allowance recorded: Real estate loans: One-to-four family 4,892 4,939 537 Commercial business loans 659 768 366 Consumer loans: Home equity loans and advances 589 589 12 6,140 6,296 915 Total: Real estate loans: One-to-four family 9,048 10,246 537 Multifamily and commercial 2,695 3,482 — Commercial business loans 2,944 3,142 366 Consumer loans: Home equity loans and advances 3,100 3,455 12 Total loans $ 17,787 $ 20,325 $ 915 The following tables present loans individually evaluated for impairment by loan segment, excluding PCI loans: At December 31, 2019 Recorded Investment Unpaid Principal Balance Specific Allowance (In thousands) With no allowance recorded: Real estate loans: One-to-four family $ 4,314 $ 5,473 $ — Multifamily and commercial 1,494 2,191 — Commercial business loans 3,859 4,048 — Consumer loans: Home equity loans and advances 1,080 1,217 — 10,747 12,929 — With a specific allowance recorded: Real estate loans: One-to-four family 4,577 4,613 484 Multifamily and commercial 1,105 1,105 2 Commercial business loans 1,319 4,307 1,121 Consumer loans: Home equity loans and advances 1,063 1,063 14 8,064 11,088 1,621 Total: Real estate loans: One-to-four family 8,891 10,086 484 Multifamily and commercial 2,599 3,296 2 Commercial business loans 5,178 8,355 1,121 Consumer loans: Home equity loans and advances 2,143 2,280 14 Total loans $ 18,811 $ 24,017 $ 1,621 The following tables present interest income recognized for loans individually evaluated for impairment, by loan segment, excluding PCI loans for the years ended December 31, 2019 and 2018 , September 30, 2017, and the three months ended December 31, 2017: For the Years Ended December 31, 2019 2018 Average Recorded Investment Interest Income Recognized Average Recorded Investment Interest Income Recognized (In thousands) Real estate loans: One-to-four family $ 8,811 $ 434 $ 10,224 $ 445 Multifamily and commercial 2,639 147 2,712 155 Construction 850 — — — Commercial business loans 6,378 479 3,060 118 Consumer loans: Home equity loans and advances 2,562 143 3,361 173 Totals $ 21,240 $ 1,203 $ 19,357 $ 891 For the Three Months Ended December 31, For the Year Ended September 30, 2017 2017 Average Recorded Investment Interest Income Recognized Average Recorded Investment Interest Income Recognized (In thousands) Real estate loans: One-to-four family $ 14,015 $ 110 $ 15,027 $ 469 Multifamily and commercial 4,087 39 4,328 279 Commercial business loans 3,870 46 3,796 195 Consumer loans: Home equity loans and advances 3,618 35 3,903 136 Totals $ 25,590 $ 230 $ 27,054 $ 1,079
Schedule of loans receivable by credit quality risk	The following tables present loans receivable by credit quality risk indicator and by loan segment, excluding PCI loans at December 31, 2019 and 2018 : December 31, 2019 One-to-Four Family Multifamily and Commercial Construction Commercial Business Home Equity Loans and Advances Other Consumer Loans Total (In thousands) Pass $ 2,072,878 $ 2,900,286 $ 298,942 $ 454,183 $ 387,251 $ 1,960 $ 6,115,500 Special mention 419 4,724 — 20,170 — — 25,313 Substandard 3,782 14,975 — 8,862 876 — 28,495 Doubtful — — — — — — — Total $ 2,077,079 $ 2,919,985 $ 298,942 $ 483,215 $ 388,127 $ 1,960 $ 6,169,308 December 31, 2018 One-to-Four Family Multifamily and Commercial Construction Commercial Business Home Equity Loans and Advances Other Consumer Loans Total (In thousands) Pass $ 1,826,066 $ 2,128,680 $ 261,473 $ 320,451 $ 392,092 $ 1,108 $ 4,929,870 Special mention — — — 9,074 — — 9,074 Substandard 4,120 13,474 — 4,351 1,400 — 23,345 Doubtful — — — — — — — Total $ 1,830,186 $ 2,142,154 $ 261,473 $ 333,876 $ 393,492 $ 1,108 $ 4,962,289

Office Properties and Equipme_2

Office Properties and Equipment, net (Tables)	12 Months Ended
Office Properties and Equipment, net (Tables)	Dec. 31, 2019
Property, Plant and Equipment [Abstract]
Schedule of Office Properties and Equipment	Office properties and equipment less accumulated depreciation at December 31, 2019 and 2018 are summarized as follows: December 31, 2019 2018 (In thousands) Land $ 11,069 $ 7,829 Buildings 27,340 24,018 Land and building improvements 31,520 24,864 Leasehold improvements 24,038 21,279 Furniture and equipment 36,828 28,538 130,795 106,528 Less accumulated depreciation and amortization 57,828 54,478 Total office properties and equipment, net $ 72,967 $ 52,050

Goodwill and Intangible Assets

Goodwill and Intangible Assets (Tables)	12 Months Ended
Goodwill and Intangible Assets (Tables)	Dec. 31, 2019
Goodwill and Intangible Assets Disclosure [Abstract]
Schedule of Goodwill and Intangible Assets	Intangible assets at December 31, 2019 and 2018 are summarized as follows: December 31, 2019 2018 (In thousands) Goodwill $ 60,763 $ 5,716 Core deposit intangibles 7,245 — Mortgage servicing rights 574 369 $ 68,582 $ 6,085
Schedule of Finite-Lived Intangible Assets, Future Amortization Expense	Scheduled amortization of core deposit intangibles for each of the next five years and thereafter is as follows: Year Ending December 31, Core Deposit Intangible Amortization (In thousands) 2020 $ 1,048 2021 1,024 2022 961 2023 892 2024 819 Thereafter 2,501

Deposits (Tables)

Deposits (Tables)	12 Months Ended
Deposits (Tables)	Dec. 31, 2019
Banking and Thrift [Abstract]
Schedule of Deposits	Deposits at December 31, 2019 and 2018 are summarized as follows: December 31, 2019 2018 Balance Weighted Average Rate Balance Weighted Average Rate (Dollars in thousands) Non-interest-bearing demand $ 958,442 — % $ 723,794 — % Interest-bearing demand 1,720,383 1.03 1,219,381 0.95 Money market accounts 410,392 0.91 259,694 0.67 Savings and club deposits 543,480 0.15 510,688 0.16 Certificates of deposit 2,013,145 2.25 1,700,316 2.01 Total deposits $ 5,645,842 1.20 % $ 4,413,873 1.09 %
Schedule of Certificate Accounts by Maturity	Scheduled maturities of certificates of deposit accounts at December 31, 2019 and 2018 are summarized as follows: December 31, 2019 2018 (In thousands) One year or less $ 1,293,613 $ 1,107,667 After one year to two years 548,995 326,800 After two years to three years 142,458 230,468 After three years to four years 11,362 24,939 After four years 16,717 10,442 $ 2,013,145 $ 1,700,316 Interest expense on deposits for the years ended December 31, 2019 and 2018 , September 30, 2017, and the three months ended December 31, 2017 are summarized as follows: Years Ended December 31, Three Months Ended December 31, Year Ended September 30, 2019 2018 2017 2017 (In thousands) Demand (including money market accounts) $ 19,922 $ 12,933 $ 2,509 $ 8,556 Savings and club deposits 770 993 210 630 Certificates of deposit 40,859 25,597 4,912 16,395 $ 61,551 $ 39,523 $ 7,631 $ 25,581

Borrowings (Tables)

Borrowings (Tables)	12 Months Ended
Borrowings (Tables)	Dec. 31, 2019
Debt Disclosure [Abstract]
Schedule of borrowed funds	Borrowings at December 31, 2019 and 2018 are summarized as follows: December 31, 2019 2018 2019 2018 Balance Weighted Average Interest Rate (In thousands) Overnight lines of credit $ 107,800 $ 159,600 1.81 % 2.60 % Federal Home Loan Bank advances 1,275,391 1,029,580 2.09 2.40 Subordinated notes 16,899 — 6.75 — Junior subordinated debentures 6,932 — 5.09 — $ 1,407,022 $ 1,189,180 2.14 % 2.43 %
Schedule of borrowed funds contractual maturity	Scheduled maturities of FHLB advances including lines of credit at December 31, 2019 are summarized as follows: Year Ended December 31, 2019 (In thousands) One year or less $ 1,004,139 After one year to two years 178,723 After two years to three years 169,800 After three years to four years 20,529 After four years 10,000 Total FHLB advances $ 1,383,191

Stockholders' Equity (Tables)

Stockholders' Equity (Tables)	12 Months Ended
Stockholders' Equity (Tables)	Dec. 31, 2019
Banking and Thrift [Abstract]
Public Utilities General Disclosures	The following table presents the Company's and the Bank's actual capital amounts and ratios as of December 31, 2019 and 2018 compared to the Federal Reserve Bank minimum capital adequacy requirements and the Federal Reserve Bank requirements for classification as a well-capitalized institution: (12) Stockholders' Equity (continued) Regulatory Capital (continued) Actual Minimum Capital Adequacy Requirements Minimum Capital Adequacy Requirements With Capital Conservation Buffer To Be Well Capitalized Under Prompt Corrective Action Provisions Amount Ratio Amount Ratio Amount Ratio Amount Ratio Company (In thousands, except ratio data) At December 31, 2019: Total capital (to risk-weighted assets) $ 1,061,555 17.25 % $ 492,438 8.00 % $ 646,324 10.50 % N/A N/A Tier 1 capital (to risk-weighted assets) 988,172 16.05 369,328 6.00 523,215 8.50 N/A N/A Common equity tier 1 capital (to risk-weighted assets) 980,995 15.94 276,996 4.50 430,883 7.00 N/A N/A Tier 1 capital (to adjusted total assets) 988,172 12.92 305,824 4.00 305,824 4.00 N/A N/A At December 31, 2018: Total capital (to risk-weighted assets) $ 1,094,062 23.45 % $ 373,276 8.00 % $ 460,763 9.88 % N/A N/A Tier 1 capital (to risk-weighted assets) 1,035,477 22.19 279,957 6.00 367,444 7.88 N/A N/A Common equity tier 1 capital (to risk-weighted assets) 1,035,477 22.19 209,968 4.50 297,455 6.38 N/A N/A Tier 1 capital (to adjusted total assets) 1,035,477 15.75 263,037 4.00 263,037 4.00 N/A N/A Bank At December 31, 2019: Total capital (to risk-weighted assets) $ 844,664 14.25 % $ 474,125 8.00 % $ 622,290 10.50 % $ 592,657 10.00 % Tier 1 capital (to risk-weighted assets) 782,881 13.21 355,594 6.00 503,758 8.50 474,125 8.00 Common equity tier 1 capital (to risk-weighted assets) 782,881 13.21 266,696 4.50 414,860 7.00 385,227 6.50 Tier 1 capital (to adjusted total assets) 782,881 10.25 305,423 4.00 305,423 4.00 381,779 5.00 At December 31, 2018: Total capital (to risk-weighted assets) $ 886,728 19.04 % $ 372,550 8.00 % $ 459,866 9.88 % $ 465,687 10.00 % Tier 1 capital (to risk-weighted assets) 828,257 17.79 279,412 6.00 366,729 7.88 372,550 8.00 Common equity tier 1 capital (to risk-weighted assets) 828,257 17.79 209,559 4.50 296,875 6.38 302,697 6.50 Tier 1 capital (to adjusted total assets) 828,257 12.60 263,025 4.00 263,025 4.00 382,006 5.00

Employee Benefit Plans (Tables)

Employee Benefit Plans (Tables)	12 Months Ended
Employee Benefit Plans (Tables)	Dec. 31, 2019
Retirement Benefits [Abstract]
Changes in Projected Benefit Obligations, Fair Value of Plan Assets, and Funded Status of Plan	The following table sets forth information regarding the Pension, RIM and Post-retirement Plans at December 31, 2019 and 2018 : December 31, 2019 2018 2019 2018 2019 2018 Pension RIM Post-retirement (In thousands) Change in benefit obligation: Benefit obligation at beginning of year $ 209,205 $ 229,156 $ 11,285 $ 12,243 $ 20,964 $ 22,078 Service cost 6,494 7,805 210 282 339 417 Interest cost 8,569 8,489 466 443 826 796 Actuarial (gain) loss 46,001 (30,703 ) 2,074 (1,355 ) 3,141 (1,845 ) Benefits paid (6,443 ) (5,542 ) (339 ) (328 ) (667 ) (482 ) Benefit obligation at end of year 263,826 209,205 13,696 11,285 24,603 20,964 Change in plan assets: Fair value of plan assets at beginning of year 272,974 289,390 — — — — Actuarial return on plan assets 54,816 (10,874 ) — — — — Employer contributions 35,000 — 339 328 667 482 Benefits paid (6,443 ) (5,542 ) (339 ) (328 ) (667 ) (482 ) Fair value of plan assets at end of year 356,347 272,974 — — — — Funded status at end of year $ 92,521 $ 63,769 $ (13,696 ) $ (11,285 ) $ (24,603 ) $ (20,964 )
Schedule of Net Benefit Costs	Net periodic benefit (income) cost for Pension Plan, RIM and Post-retirement Plan and split dollar life insurance arrangement plan benefits for the years ended December 31, 2019 and 2018 , September 30, 2017 and the three months ended December 31, 2017 , includes the following components: (13) Employee Benefit Plans (continued) Pension Plan, Retirement Income Maintenance Plan (the "RIM Plan") and Post-retirement Plan (cont'd) For the Years Ended December 31, 2019 2018 Pension RIM Post-retirement Pension RIM Post-retirement Affected Line Item in the Consolidated Statements of Income (In thousands) Service cost $ 6,494 $ 210 $ 339 $ 7,805 $ 282 $ 417 Compensation and employee benefits Interest cost 8,569 466 826 8,489 443 796 Other non-interest expense Expected return on plan assets (21,058 ) — — (20,794 ) — — Other non-interest expense Amortization: Prior service cost — — — — — (106 ) Other non-interest expense Net loss 3,070 244 147 3,117 413 323 Other non-interest expense Net periodic (income) benefit cost $ (2,925 ) $ 920 $ 1,312 $ (1,383 ) $ 1,138 $ 1,430 For the Three Months Ended December 31, For the Year Ended September 30, 2017 2017 Pension RIM Post-retirement Pension RIM Post-retirement (In thousands) Service cost $ 1,780 $ 60 $ 92 $ 7,621 $ 237 $ 471 Interest cost 2,128 111 205 8,444 429 742 Expected return on plan assets (4,814 ) — — (24,809 ) — — Amortization: Prior service cost — — (34 ) — — (136 ) Net loss 707 103 70 10,998 453 325 Net periodic (income) benefit cost $ (199 ) $ 274 $ 333 $ 2,254 $ 1,119 $ 1,402
Condensed Income Statement	The following table summarizes the impact of retrospective application of ASU 2017-07 to the Consolidated Statements of Income for the year ended December 31, 2018: Year Ended December 31, 2018 (In thousands) Compensation and employee benefits: As previously reported $ 69,907 As reported under ASU 2017-07 77,226 Other non-interest expense: As previously reported $ 12,916 As reported under ASU 2017-07 5,597
Schedule of Amounts Recognized in Other Comprehensive Income (Loss)	The components of accumulated other comprehensive income related to the Pension, RIM, and Post-retirement Plans on a pre-tax basis, at December 31, 2019 , 2018 , and 2017, and September 30, 2017 are summarized in the following table: At December 31, 2019 2018 Pension RIM Post-retirement Pension RIM Post-retirement (In thousands) Unrecognized prior service costs $ — $ — $ — $ — $ — $ — Unrecognized net actuarial income 68,752 5,577 7,221 59,579 3,748 4,226 Total accumulated other comprehensive income $ 68,752 $ 5,577 $ 7,221 $ 59,579 $ 3,748 $ 4,226 At December 31 At September 30, 2017 2017 Pension RIM Post-retirement Pension RIM Post-retirement (In thousands) Unrecognized prior service costs $ — $ — $ (106 ) $ — $ — $ (140 ) Unrecognized net actuarial income 61,731 5,515 6,395 55,438 4,725 4,611 Total accumulated other comprehensive income $ 61,731 $ 5,515 $ 6,289 $ 55,438 $ 4,725 $ 4,471 The weighted average actuarial assumptions used in the plan determinations at and for the years ended December 31, 2019 and 2018 , September 30, 2017 and the three months ended December 31, 2017 were as follows: At and For the Years Ended December 31, 2019 2018 Pension RIM Post-retirement Pension RIM Post-retirement Weighted average assumptions used to determine benefit obligation: Discount rate 3.490 % 3.330 % 3.270 % 4.570 % 4.470 % 4.410 % Rate of compensation increase 3.500 3.500 N/A 3.500 3.500 N/A Weighted average assumptions used to determine net periodic benefit cost: Discount rate 4.570 % 4.470 % 4.410 % 3.750 % 3.625 % 3.625 % Discount rate-remeasurement 3.850 N/A N/A N/A N/A N/A Expected rate of return on plan assets 7.000 N/A N/A 7.250 % N/A N/A Rate of compensation increase 3.500 3.500 N/A 3.500 3.500 N/A At and For the Three Months Ended December 31, At and for the Year Ended September 30, 2017 2017 Pension RIM Post-retirement Pension RIM Post-retirement Weighted average assumptions used to determine benefit obligation: Discount rate 3.750 % 3.625 % 3.625 % 4.000 % 3.875 % 3.875 % Rate of compensation increase 3.500 3.500 N/A 3.500 3.500 N/A Weighted average assumptions used to determine net periodic benefit cost: Discount rate 4.000 % 3.875 % 3.875 % 3.875 % 3.625 % 3.625 % Expected rate of return on plan assets 7.250 N/A N/A 7.500 N/A N/A Rate of compensation increase 3.500 3.500 N/A 3.500 3.500 N/A
Schedule of Effect of One-Percentage-Point Change in Assumed Health Care Cost Trend Rates	A 1% change in the assumed health care cost trend rate would have the following effects on post-retirement benefits at December 31, 2019 : 1% increase 1% decrease (In thousands) Effect on total service cost and interest cost $ 14 $ (12 ) Effect on post-retirement benefit obligations 162 (141 )
Schedule of Expected Benefit Payments	Estimated future benefit payments, which reflect expected future service, as appropriate for the next five years and thereafter are as follows: Pension RIM Post-retirement (In thousands) 2020 $ 6,675 $ 361 $ 1,246 2021 7,209 379 1,293 2022 7,760 417 1,337 2023 8,412 457 1,351 2024 9,112 521 1,346 2025 - 2029 57,274 3,605 7,270
Schedule of Allocation of Plan Assets	The weighted average asset allocation of pension assets at December 31, 2019 and 2018 were as follows: December 31, 2019 2018 Domestic equities 39.60 % 35.20 % Foreign equities 9.60 10.80 Fixed income 44.30 42.30 Real estate 6.10 10.50 Cash 0.40 1.20 Total 100.00 % 100.00 % The following tables present the assets that are measured at fair value on a recurring basis by level within the U.S. GAAP fair value hierarchy as reported on the Statements of Net Assets Available for Plan Benefits at December 31, 2019 and 2018 , respectively. A financial instrument's level within the fair value hierarchy's is based on the lowest level of input that is significant to the fair value measurement. December 31, 2019 Fair Value Measurements Fair Value Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) (In thousands) Money market mutual funds $ 1,462 $ 1,462 $ — $ — Mutual funds - value stock fund 27,827 27,827 — — Mutual funds - fixed income 158,030 158,030 — — Mutual funds - international stock 34,332 34,332 — — Mutual funds - institutional stock index 113,100 113,100 — — Commingled real estate funds 21,596 — 21,596 — $ 356,347 $ 334,751 $ 21,596 $ — (13) Employee Benefit Plans (continued) Pension Plan, Retirement Income Maintenance Plan (the "RIM Plan") and Post-retirement Plan (cont'd) December 31, 2018 Fair Value Measurements Fair value Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) (In thousands) Money market mutual funds $ 3,459 $ 3,459 $ — $ — Mutual funds - value stock fund 22,533 22,533 — — Mutual funds - fixed income 115,500 115,500 — — Mutual funds - international stock 29,441 29,441 — — Mutual funds - institutional stock index 73,450 73,450 — — Commingled real estate funds 28,591 — 28,591 — $ 272,974 $ 244,383 $ 28,591 $ — Allowable Range Equities 40-60% Fixed income 40-60% Real estate 0-10% Cash 0-15%
Employee Stock Ownership Plan (ESOP) Disclosures	The ESOP shares were as follows: December 31, 2019 2018 (In thousands) Allocated shares 385 159 Unearned shares 4,156 4,384 Total ESOP shares 4,541 4,543 Fair value of unearned shares $ 70,409 $ 67,025

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
Income Taxes (Tables)	Dec. 31, 2019
Income Tax Disclosure [Abstract]
Schedule of Components of Income Tax Expense (Benefit)	The current and deferred amounts of income tax expense (benefit) for the years ended December 31, 2019 and 2018, September 30, 2017, and the three months ended December 31, 2017 are as follows: Years Ended December 31, Three Months Ended December 31, Year Ended September 30, 2019 2018 2017 2017 (In thousands) Current: Federal $ 5,933 $ 11,284 $ 630 $ 16,198 State 2,905 5,129 862 1,236 Total current 8,838 16,413 1,492 17,434 Deferred: Federal 8,275 (4,901 ) 7,530 (1,454 ) State (748 ) (589 ) (39 ) 28 Total deferred 7,527 (5,490 ) 7,491 (1,426 ) Total income tax expense $ 16,365 $ 10,923 $ 8,983 $ 16,008
Schedule of Effective Income Tax Rate Reconciliation	A reconciliation between the amount of reported total income tax expense and the amount computed by multiplying the applicable statutory federal income tax rate (21% for the 2019 and 2018 periods, and 35% for the 2017 periods) is as follows: Years Ended December 31, Three Months Ended December 31, Year Ended September 30, 2019 2018 2017 2017 (In thousands) Tax expense at applicable statutory rate $ 14,927 $ 7,067 $ 4,431 $ 16,478 Increase (decrease) in taxes resulting from: State tax, net of federal income tax benefit 1,704 3,587 535 822 ESOP fair market value adjustment 272 202 — — Tax exempt interest income (6 ) (4 ) (2 ) (50 ) Income from Bank-owned life insurance (1,246 ) (812 ) (381 ) (1,589 ) Dividend received deduction (8 ) (16 ) (10 ) (40 ) Non-deductible merger-related expenses 222 — — — Non-deductible compensation expense 398 — — — Impact of tax reform — — 4,700 — Other, net 102 899 (290 ) 387 Total income tax expense $ 16,365 $ 10,923 $ 8,983 $ 16,008
Schedule of Deferred Tax Assets and Liabilities	The tax effects of temporary differences that give rise to significant portions of the deferred tax assets and deferred tax liabilities at December 31, 2019 and 2018 are as follows: At December 31, 2019 2018 (In thousands) Deferred tax assets: Allowance for loan losses $ 13,114 $ 13,251 Post-retirement benefits 4,089 3,720 Deferred compensation 2,085 2,228 Depreciation 1,002 1,042 Retirement Income Maintenance plan 1,725 1,602 ESOP 301 128 Stock-based compensation 788 35 Reserve for uncollected interest 54 24 Net unrealized losses on debt securities and defined benefit plans 18,374 19,060 Federal and State NOLs 8,333 2,063 Alternative minimum assessment carryforwards 2,156 2,156 Charitable contribution carryforward 5,981 6,085 Purchase accounting 665 — Other items 332 670 Gross deferred tax assets 58,999 52,064 Valuation allowance (7,442 ) (2,388 ) 51,557 49,676 Deferred tax liabilities: Pension expense 33,856 26,071 Deferred loan costs 5,911 5,736 Intangible assets 1,215 1,621 Other items 266 34 Total gross deferred tax liabilities 41,248 33,462 Net deferred tax asset $ 10,309 $ 16,214

Financial Transactions with O_2

Financial Transactions with Off-Balance-Sheet risk and Concentrations of Credit risk (Tables)	12 Months Ended
	Dec. 31, 2019
Commitments and Contingencies Disclosure [Abstract]
Schedules of Concentration of Risk, by Risk Factor	At December 31, 2019 and 2018 , the following commitments existed which are not reflected in the Consolidated Statements of Financial Condition: December 31, 2019 2018 (In thousands) Loan commitments: Residential real estate $ 91,141 $ 29,622 Multifamily and commercial real estate 95,025 73,201 Commercial business 18,737 13,000 Construction 59,990 71,062 Consumer home equity loans and lines of credit 5,988 8,344 Total loan commitments $ 270,881 $ 195,229
Contractual Obligation, Fiscal Year Maturity Schedule	Minimum aggregate lease payments for the remainder of the lease terms as of December 31, 2019 are as follows: Amount (In thousands) Years ending: 2020 $ 4,942 2021 4,484 2022 4,012 2023 3,503 2024 2,732 Thereafter 5,001 Total lease commitments $ 24,674

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	12 Months Ended
Fair Value Measurements (Tables)	Dec. 31, 2019
Fair Value Disclosures [Abstract]
Schedule of fair value assets and liabilities measured on recurring basis	The following tables present the assets and liabilities reported on the Consolidated Statements of Financial Condition at their fair values as of December 31, 2019 and 2018 , by level within the fair value hierarchy: December 31, 2019 Fair Value Measurements Fair Value Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) (In thousands) Debt securities available for sale: U.S. government and agency obligations $ 42,386 $ 42,386 $ — $ — Mortgage-backed securities and collateralized mortgage obligations 979,881 — 979,881 — Municipal obligations 2,284 — 2,284 — Corporate debt securities 69,180 — 69,180 — Trust preferred securities 4,605 — 4,605 — Total debt securities available for sale 1,098,336 42,386 1,055,950 — Equity securities 2,855 2,587 268 — Derivative assets 185 — 185 — $ 1,101,376 $ 44,973 $ 1,056,403 $ — Derivative liabilities $ 11,546 $ — $ 11,546 $ — (16) Fair Value Measurements (continued) December 31, 2018 Fair Value Measurements Fair Value Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) (In thousands) Debt securities available for sale: U.S. government and agency obligations $ 54,157 $ 54,157 $ — $ — Mortgage-backed securities and collateralized mortgage obligations 920,007 — 920,007 — Municipal obligations 987 — 987 — Corporate debt securities 53,467 — 53,467 — Trust preferred securities 4,250 — 4,250 — Total debt securities available for sale 1,032,868 54,157 978,711 — Equity securities 1,890 1,890 — — Derivative assets 1,342 — 1,342 — $ 1,036,100 $ 56,047 $ 980,053 $ — Derivative liabilities $ 3,944 $ — $ 3,944 $ —
Schedule of fair value assets and liabilities measured on non-recurring basis	The following tables present the assets and liabilities reported on the Consolidated Statements of Financial Condition at their fair values as of December 31, 2019 and 2018 , by level within the fair value hierarchy: December 31, 2019 Fair Value Measurements Fair Value Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) (In thousands) Impaired loans $ 1,063 $ — $ — $ 1,063 Mortgage servicing rights 681 — — 681 $ 1,744 $ — $ — $ 1,744 December 31, 2018 Fair Value Measurements Fair Value Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) (In thousands) Impaired loans $ 125 $ — $ — $ 125 Real estate owned 92 — — 92 Mortgage servicing rights 442 — — 442 $ 659 $ — $ — $ 659
Schedule of qualitative information for Level 3 assets measured at fair value on a non-recurring basis	The following table presents information for Level 3 assets measured at fair value on a non-recurring basis as of December 31, 2019 and 2018 : December 31, 2019 Fair Value Valuation Methodology Unobservable Inputs Range of Inputs Weighted Average (Dollars in thousands) Impaired loans $ 1,063 Estimated cash flow Expected value of future cash flows (5) —% —% Mortgage servicing rights 681 Estimated cash flow Prepayment speeds and discount rates (4) 3.6% - 24.0% 12.7% (16) Fair Value Measurements (continued) December 31, 2018 Fair Value Valuation Methodology Unobservable Inputs Range of Inputs Weighted Average (Dollars in thousands) Impaired loans $ 125 Appraised value (2) Discount for cost to sell (3) 6.0% 6.0% Real estate owned 92 Contract sales price (1) Discount for cost to sell (3) 6.0% 6.0% Mortgage servicing rights 442 Estimated cash flow Prepayment speeds (4) 3.3% - 26.8% 12.0% (1) Value is based on signed contract for sale. (2) Value is based on an independent appraisal of the fair value of the loan's underlying collateral. (3) Includes commissions, fees and other costs. (4) Value of SBA servicing rights based on a discount rate of 11.75%. (5) Value based on management's estimate of expected future cash flows.
Schedule of fair value assets and liabilities on Consolidated Balance Sheets	The following tables present the assets and liabilities reported on the Consolidated Statements of Financial Condition at their fair values as of December 31, 2019 and 2018 : (16) Fair Value Measurements (continued) December 31, 2019 Fair Value Measurements Carrying Value Total Fair Value Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) (In thousands) Financial assets: Cash and cash equivalents $ 75,547 $ 75,547 $ 75,547 $ — $ — Debt securities available for sale 1,098,336 1,098,336 42,386 1,055,950 — Debt securities held to maturity 285,756 289,505 19,960 269,545 — Equity securities, at fair value 2,855 2,855 2,587 268 Federal Home Loan Bank stock 69,579 69,579 — 69,579 — Loans receivable, net 6,135,857 6,219,008 — — 6,219,008 Derivative assets 185 185 — 185 — Financial liabilities: Deposits $ 5,645,842 $ 5,654,075 $ — $ 5,654,075 $ — Borrowings 1,407,022 1,411,962 — 1,411,962 — Derivative liabilities 11,546 11,546 — 11,546 — December 31, 2018 Fair Value Measurements Carrying Value Total Fair Value Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) (In thousands) Financial assets: Cash and cash equivalents $ 42,201 $ 42,201 $ 42,201 $ — $ — Debt securities available for sale 1,032,868 1,032,868 54,157 978,711 — Debt securities held to maturity 262,143 254,841 23,241 231,600 — Equity securities 1,890 1,890 1,890 — — Federal Home Loan Bank stock 58,938 58,938 — 58,938 — Loans held-for-sale 8,081 8,081 8,081 — Loans receivable, net 4,916,840 4,841,830 — — 4,841,830 Derivative assets 1,342 1,342 — 1,342 — Financial liabilities: Deposits $ 4,413,873 $ 4,402,336 $ — $ 4,402,336 $ — Borrowings 1,189,180 1,185,007 — 1,185,007 — Derivative liabilities 3,944 3,944 — 3,944 —

Selected Quarterly Financial _2

Selected Quarterly Financial Data (Unaudited) (Tables)	12 Months Ended
Selected Quarterly Financial Data (Unaudited) (Tables)	Dec. 31, 2019
Quarterly Financial Information Disclosure [Abstract]
Quarterly Financial Information	The following tables are a condensed summary of certain quarterly results of operation for the years ended December 31, 2019 and 2018 , September 30, 2017, and the three months ended December 31, 2017 : Quarters Ended December 31, 2019 March 31 June 30 September 30 December 31 (Dollars in thousands, except share and per share data) Total interest income $ 62,887 $ 62,732 $ 64,438 $ 71,026 Total interest expense 20,503 21,889 22,722 23,598 Net interest income 42,384 40,843 41,716 47,428 Provision for loan losses 436 112 1,157 2,519 Net interest income after provision for loan losses 41,948 40,731 40,559 44,909 Total non-interest income 6,037 6,775 10,115 8,709 Total non-interest expense 29,559 31,841 31,064 36,237 Income before income tax expense 18,426 15,665 19,610 17,381 Income tax expense 3,507 3,634 5,392 3,832 Net income $ 14,919 $ 12,031 $ 14,218 $ 13,549 Earnings per share - basic and diluted $ 0.13 $ 0.11 $ 0.13 $ 0.12 Weighted average shares outstanding - basic and diluted 111,536,577 111,553,203 111,371,754 109,958,999 Quarters Ended December 31, 2018 March 31 June 30 September 30 December 31 (Dollars in thousands, except share and per share data) Total interest income $ 51,791 $ 55,019 $ 57,695 $ 61,785 Total interest expense 12,730 14,004 17,112 18,410 Net interest income 39,061 41,015 40,583 43,375 Provision for loan losses 2,000 2,400 1,500 777 Net interest income after provision for loan losses 37,061 38,615 39,083 42,598 Total non-interest income 4,543 5,450 5,290 6,405 Total non-interest expense 26,015 61,768 26,590 31,013 Income (loss) before income tax expense 15,589 (17,703 ) 17,783 17,990 Income tax expense 3,805 (2,961 ) 6,956 3,123 Net income (loss) $ 11,784 $ (14,742 ) $ 10,827 $ 14,867 Earnings per share - basic and diluted N/A $ (0.13 ) $ 0.10 $ 0.13 Weighted average shares outstanding - basic and diluted N/A 111,360,278 111,389,951 111,423,361 (17) Selected Quarterly Financial Data (Unaudited) (continued) Quarter Ended December 31, 2017 Dollars in thousands, except per share data) Total interest income $ 49,169 Total interest expense 12,240 Net interest income 36,929 Provision for loan losses 3,400 Net interest income after provision for loan losses 33,529 Total non-interest income 4,733 Total non-interest expense 25,601 Income before income tax expense 12,661 Income tax expense 8,983 Net income $ 3,678 Earnings per share - basic and diluted N/A Quarters Ended September 30, 2017 December 31 March 31 June 30 September 30 (Dollars in thousands, except per share data) Total interest income $ 44,129 $ 45,428 $ 46,850 $ 47,820 Total interest expense 10,724 10,651 11,211 11,860 Net interest income 33,405 34,777 35,639 35,960 Provision for loan losses — 375 375 5,676 Net interest income after provision for loan losses 33,405 34,402 35,264 30,284 Total non-interest income 5,534 5,806 4,645 1,630 Total non-interest expense 24,078 24,903 24,703 30,206 Income before income tax expense 14,861 15,305 15,206 1,708 Income tax expense 4,868 5,012 5,934 194 Net income $ 9,993 $ 10,293 $ 9,272 $ 1,514 Earnings per share - basic and diluted N/A N/A N/A N/A

Earnings per Share (Tables)

Earnings per Share (Tables)	12 Months Ended
Earnings per Share (Tables)	Dec. 31, 2019
Earnings Per Share [Abstract]
Schedule of Earnings Per Share, Basic and Diluted	The following is a reconciliation of the numerators and denominators of the basic and diluted earnings per share calculations for the years ended December 31, 2019 and 2018 , September 30, 2017, and the three months ended December 31, 2017: December 31, Three Months Ended December 31, September 30, 2019 2018 2017 2017 (Dollars in thousands, except share and per share data) Net income $ 54,717 $ 22,736 $ 3,678 $ 31,072 Shares: Weighted average shares outstanding - basic 111,101,246 111,395,723 N/A N/A Weighted average dilutive shares outstanding — — N/A N/A Weighted average shares outstanding - diluted 111,101,246 111,395,723 N/A N/A Earnings per share: Basic $ 0.49 $ 0.20 N/A N/A Diluted $ 0.49 $ 0.20 N/A N/A

Parent-only Financial Informa_2

Parent-only Financial Information (Tables)	12 Months Ended
Parent-only Financial Information (Tables)	Dec. 31, 2019
Condensed Financial Information Disclosure [Abstract]
Condensed Balance Sheet	The condensed financial statements of Columbia Financial, Inc. (parent company) are presented below: Statements of Financial Condition December 31, 2019 2018 (In thousands) Assets Cash and due from Bank $ 168,242 $ 153,697 Short-term investments 127 136 Total cash and cash equivalents 168,369 153,833 Debt securities available for sale, at fair value 1,496 — Equity securities, at fair value 1,282 1,420 Investment in subsidiaries 785,964 764,663 Loan receivable from Bank 42,982 44,439 Other assets 8,431 7,852 Total assets $ 1,008,524 $ 972,207 Liabilities and Stockholders' Equity Liabilities: Borrowings $ 23,831 $ — Accrued expenses and other liabilities 2,176 147 Total liabilities 26,007 147 Total stockholders' equity 982,517 972,060 Total liabilities and stockholders' equity $ 1,008,524 $ 972,207
Condensed Statement of Comprehensive Income	Statements of Comprehensive Income (Loss) Years Ended December 31, Three Months Ended December 31, Year Ended September 30, 2019 2018 2017 2017 (In thousands) Income: Dividends from subsidiary $ 179,000 $ — $ — $ 2,000 Loans receivable 2,111 1,513 — — Debt securities available for sale and equity securities 51 123 41 162 Interest-earning deposits 173 871 — 1 Total interest income 181,335 2,507 41 2,163 Interest expense on borrowings 176 3,468 1,044 4,177 Net interest income (expense) 181,159 (961 ) (1,003 ) (2,014 ) Equity earnings (loss) in subsidiary (123,142 ) 51,401 4,288 32,230 Non-interest income: Gain on securities transactions 236 — (60 ) — Change in fair value of equity securities 65 — — — Other non-interest income 139 — — — Total non-interest income 440 — (60 ) — Non-interest expense Charitable contribution to foundation — 34,767 — — Merger-related expenses 1,807 — — — Other non-interest expense 1,955 425 2 460 Total non-interest expense 3,762 35,192 2 460 Income before income tax benefit 54,695 15,248 3,223 29,756 Income tax benefit 22 7,488 455 1,316 Net income 54,717 22,736 3,678 31,072 Other comprehensive income (loss) 3,710 (6,487 ) (19,230 ) 5,178 Comprehensive income (loss) $ 58,427 $ 16,249 $ (15,552 ) $ 36,250
Condensed Cash Flow Statement	Statements of Cash Flows Years Ended December 31, Three Months Ended December 31, Year Ended September 30, 2019 2018 2017 2017 (In thousands) Cash flows from operating activities: Net income $ 54,717 $ 22,736 $ 3,678 $ 31,072 Adjustments to reconcile net income to net cash provided by operating activities: Amortization of debt issuance costs — 890 14 53 Amortization of intangible assets (71 ) — — — (Gain) loss on securities transactions (236 ) — 60 — Change in fair value of equity securities (65 ) — — — Deferred tax (benefit) expense 1,453 (6,086 ) 42 1 (Decrease) increase in other assets (2,026 ) 1,515 (494 ) 1,404 Increase (decrease) in accrued expenses and other liabilities 3,515 (1,498 ) 989 62 Contribution of common stock to Columbia Bank Foundation — 34,767 — — Equity in undistributed earnings (loss) of subsidiary 123,142 (51,401 ) (4,288 ) (32,295 ) Net cash provided by operating activities 180,429 923 1 297 Cash flows from investing activities: Capital contribution to subsidiary — (246,420 ) — — Proceeds from sales of debt securities available for sale — — 92 — Proceeds from sale of equity securities 1,065 — — — Proceeds from paydowns/maturities/calls of debt securities available for sale 500 1,601 10 — Purchases of debt securities available for sale — (414 ) — — Purchase of equity securities (416 ) — — — Loan to ESOP — (45,428 ) — — Repayment of loan receivable from Bank 1,457 989 — — Net cash paid in acquisition (135,410 ) — — — Net cash (used in) provided by investing activities (132,804 ) (289,672 ) 102 — Cash flows from financing activities: Payments on trust preferred securities — (51,547 ) — — Issuance of common stock in initial public offering — 492,428 — — Purchase of treasury stock (55,309 ) — — — Issuance of common stock allocated to restricted stock award grants 21,687 — — — Restricted stock forfeitures (736 ) — — — Issuance of treasury stock allocated to restricted stock award grants 1,269 — — — Net cash (used in) provided by financing activities (33,089 ) 440,881 — — (19) Parent-only Financial Information (continued) Statements of Cash Flows Years Ended December 31, Three Months Ended December 31, Year Ended September 30, 2019 2018 2017 2017 (In thousands) Net increase in cash and cash equivalents $ 14,536 — $ 152,132 — $ 103 $ 297 Cash and cash equivalents at beginning of year 153,833 1,701 1,598 1,301 Cash and cash equivalents at end of period $ 168,369 $ 153,833 $ 1,701 $ 1,598 Acquisition: Non-cash assets acquired: Debt securities available for sale $ 1,998 $ — $ — $ — Equity securities 208 — — — Other assets 1,492 — — — Total non-cash assets acquired $ 3,698 $ — $ — $ — Liabilities assumed: Borrowings $ 23,901 $ — $ — $ — Total liabilities assumed $ 23,901 $ — $ — $ — Net non-cash liabilities acquired $ (20,203 ) $ — $ — $ — Net cash acquired in acquisition $ 884 $ — $ — $ —

Other Comprehensive Income (L_2

Other Comprehensive Income (Loss) (Tables)	12 Months Ended
Other Comprehensive Income (Loss) (Tables)	Dec. 31, 2019
Equity [Abstract]
Schedule of Other Comprehensive Income (Loss)	The following tables present the components of other comprehensive income (loss), both gross and net of tax, for the years ended December 31, 2019 and 2018 , September 30, 2017, and the three months ended December 31, 2017 : For the Years Ended December 31, 2019 2018 Before Tax Tax Effect After Tax Before Tax Tax Effect After Tax (In thousands) Components of other comprehensive income (loss): Unrealized gains (losses) on debt securities available for sale: $ 26,601 $ (5,534 ) $ 21,067 $ (7,224 ) $ 1,446 $ (5,778 ) Accretion of unrealized gain (loss) on debt securities reclassified as held to maturity 11 (2 ) 9 (13 ) — (13 ) Reclassification adjustment for gains included in net income 2,612 (601 ) 2,011 (116 ) 24 (92 ) 29,224 (6,137 ) 23,087 (7,353 ) 1,470 (5,883 ) Derivatives: Unrealized (loss) on swap contracts accounted for as cash flow hedges (8,193 ) 1,725 (6,468 ) (2,825 ) 595 (2,230 ) Employee benefit plans: Amortization of prior service cost included in net income (56 ) 12 (44 ) (623 ) 132 (491 ) Reclassification adjustment of actuarial net (loss) gain included in net income (3,709 ) 779 (2,930 ) 2,526 (530 ) 1,996 Change in funded status of retirement obligations (12,576 ) 2,641 (9,935 ) 897 (776 ) 121 (16,341 ) 3,432 (12,909 ) 2,800 (1,174 ) 1,626 Total other comprehensive income (loss) $ 4,690 $ (980 ) $ 3,710 $ (7,378 ) $ 891 $ (6,487 ) (20) Other Comprehensive Income (Loss) (continued) For the Three Months Ended December 31, For the Year Ended September 30, 2017 2017 Before Tax Tax Effect After Tax Before Tax Tax Effect After Tax (In thousands) Components of other comprehensive income (loss): Unrealized gains (losses) on debt securities available for sale: $ (3,012 ) $ (119 ) $ (3,131 ) $ (17,877 ) $ 6,379 $ (11,498 ) Accretion of unrealized (loss) gain on debt securities reclassified as held to maturity (2 ) (56 ) (58 ) 12 (4 ) 8 Reclassification adjustment for gains included in net income 60 (13 ) 47 2,626 (937 ) 1,689 (2,954 ) (188 ) (3,142 ) (15,239 ) 5,438 (9,801 ) Derivatives: Unrealized gain on swap contracts accounted for as cash flow hedges 192 (30 ) 162 95 (33 ) 62 Employee benefit plans: Amortization of prior service cost included in net income (24 ) (19 ) (43 ) (114 ) 41 (73 ) Reclassification adjustment of actuarial net (loss) gain included in net income (9 ) (94 ) (103 ) 11,806 (4,213 ) 7,593 Change in funded status of retirement obligations (9,024 ) 3,354 (5,670 ) 11,503 (4,106 ) 7,397 Tax effects resulting from the adoption of ASU No. 2018-02 — (10,434 ) (10,434 ) — — — (9,057 ) (7,193 ) (16,250 ) 23,195 (8,278 ) 14,917 Total other comprehensive (loss) income $ (11,819 ) $ (7,411 ) $ (19,230 ) $ 8,051 $ (2,873 ) $ 5,178
Components of Other Comprehensive Income (Loss)	The following tables present the changes in the components of accumulated other comprehensive income (loss), net of tax, for the years ended December 31, 2019 and 2018 , September 30, 2017, and the three months ended December 31, 2017 : For the Years Ended December 31, 2019 2018 Unrealized (Losses) Gains on Debt Securities Available for Sale Unrealized (Losses) on Swaps Employee Benefit Plans Accumulated Other Comprehensive (Loss) Unrealized (Losses) on Debt Securities Available for Sale Unrealized Gains (Losses) on Swaps Employee Benefit Plans Accumulated Other Comprehensive (Loss) (In thousands) Balance at beginning of period $ (13,162 ) $ (2,006 ) $ (56,729 ) $ (71,897 ) $ (7,279 ) $ 224 $ (58,355 ) $ (65,410 ) Effect of the adoption of ASU 2016-01 (548 ) (548 ) — — — — Balance at January 1, 2019 $ (13,710 ) $ (2,006 ) $ (56,729 ) $ (72,445 ) $ (7,279 ) $ 224 $ (58,355 ) $ (65,410 ) Current period changes in other comprehensive income (loss) 23,087 (6,468 ) (12,909 ) 3,710 (5,883 ) (2,230 ) 1,626 (6,487 ) Total other comprehensive income (loss) $ 9,377 $ (8,474 ) $ (69,638 ) $ (68,735 ) $ (13,162 ) $ (2,006 ) $ (56,729 ) $ (71,897 ) For the Three Months Ended December 31, For the Year Ended September 30, 2017 2017 Unrealized (Losses) Gains on Debt Securities Available for Sale Unrealized Gains on Swaps Employee Benefit Plans Accumulated Other Comprehensive (Loss) Unrealized (Losses) Gains on Debt Securities Available for Sale Unrealized Gains on Swaps Employee Benefit Plans Accumulated Other Comprehensive (Loss) (In thousands) Balance at beginning of period $ (4,137 ) $ 62 $ (42,105 ) $ (46,180 ) $ 5,664 $ — $ (57,022 ) $ (51,358 ) Current period changes in other comprehensive (loss) income (1,828 ) 122 (5,816 ) (7,522 ) (9,801 ) 62 14,917 5,178 Reclassification of tax effects resulting from the adoption of ASU No. 2018-02 (1,314 ) 40 (10,434 ) (11,708 ) — — — — Total other comprehensive income (loss) $ (7,279 ) $ 224 $ (58,355 ) $ (65,410 ) $ (4,137 ) $ 62 $ (42,105 ) $ (46,180 )
Reclassification out of AOCI	The following tables reflect amounts reclassified out of accumulated other comprehensive income (loss) in the Consolidated Statements of Income and the affected line item in the statement where net income is presented for the years ended December 31, 2019 and 2018 , September 30, 2017, and the three months ended December 31, 2017 : Accumulated Other Comprehensive (Loss) Income Components For the Years Ended December 31, Affected line items in the Consolidated Statements of Income 2019 2018 (In thousands) Reclassification adjustment for gains (losses) included in net income $ 2,612 $ (116 ) Gain (loss) on securities transactions Reclassification adjustment of actuarial net (loss) gain included in net income (3,709 ) 2,526 Other non-interest expense Total before tax (1,097 ) 2,410 Income tax (benefit) 178 (506 ) Net of tax $ (919 ) $ 1,904 Accumulated Other Comprehensive (Loss) Income Components For the Three Months Ended December 31, For the Year Ended September 30, Affected line items in the Consolidated Statements of Income 2017 2017 (In thousands) Reclassification adjustment for gains included in net income $ 60 $ 2,626 Gain on securities transactions Reclassification adjustment of actuarial net (loss) gain included in net income (9 ) 11,806 Other non-interest expense Total before tax 51 14,432 Income tax (benefit) (107 ) (5,150 ) Net of tax $ (56 ) $ 9,282

Derivatives and Hedging Activ_2

Derivatives and Hedging Activities (Tables)	12 Months Ended
Derivatives and Hedging Activities (Tables)	Dec. 31, 2019
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Schedule of derivative financial instruments on the Consolidated Balance Sheets	The tables below present the fair value of the Company’s derivative financial instruments as well as their classification in the Consolidated Statements of Financial Condition at December 31, 2019 and 2018 : December 31, 2019 Asset Derivative Liability Derivative Consolidated Statements of Financial Condition Fair Value Consolidated Statements of Financial Condition Fair Value (In thousands) Derivatives: Interest rate swaps Other Assets $ 185 Other Liabilities $ 11,546 Total derivative instruments $ 185 $ 11,546 December 31, 2018 Asset Derivative Liability Derivative Consolidated Statements of Financial Condition Fair Value Consolidated Statements of Financial Condition Fair Value (In thousands) Derivatives: Interest rate swaps Other Assets $ 1,342 Other Liabilities $ 3,944 Total derivative instruments $ 1,342 $ 3,944

Revenue Recognition (Tables)

Revenue Recognition (Tables)	12 Months Ended
Revenue Recognition (Tables)	Dec. 31, 2019
Revenue from Contract with Customer [Abstract]
Disaggregation of Revenue	The following table presents non-interest income, segregated by revenue streams in-scope and out-of-scope of Topic 606, for the years ended December 31, 2019 and 2018 . For the Years Ended December 31, 2019 2018 (In thousands) Non-interest income In-scope of Topic 606: Demand deposit account fees $ 4,478 $ 3,987 Title insurance fees 4,981 4,297 Other non-interest income 4,844 4,679 Total in-scope non-interest income 14,303 12,963 Total out-of-scope non-interest income 17,333 8,725 Total non-interest income $ 31,636 $ 21,688

Business (Details)

Business (Details) - Minority Stock Offering	Apr. 19, 2018shares
Columbia Bank, MHC
Subsidiary, Sale of Stock [Line Items]
Shares issued (in shares)	62,580,155
Columbia Bank Foundation
Subsidiary, Sale of Stock [Line Items]
Shares issued (in shares)	3,476,675
Columbia Bank Employee Stock Ownership Plan
Subsidiary, Sale of Stock [Line Items]
Shares issued (in shares)	49,832,345

Summary of Significant Accoun_3

Summary of Significant Accounting Policies (Details) - USD ($)	1 Months Ended	12 Months Ended
	Apr. 30, 2018	Dec. 31, 2019	Dec. 31, 2018	Nov. 30, 2019	Jan. 01, 2019	Aug. 31, 2018
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Junior subordinated debenture owed to unconsolidated subsidiary trust						$ 51,500,000
Assets		$ 8,188,694,000	$ 6,691,618,000
Cash reserves		8,800,000	5,900,000
Loan threshold for individual evaluation for impairment		500,000
Equity securities, at fair value		$ 2,855,000	1,890,000
Retained Earnings
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Reclassification from AOCI to retained earnings due to TCJA			11,700,000
Buildings
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Property, plant and equipment, useful life		40 years
Minimum
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Defined contribution plan, employer matching contribution, percent of match		3.00%
Minimum \| Land and building improvements
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Property, plant and equipment, useful life		10 years
Minimum \| Furniture and equipment
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Property, plant and equipment, useful life		3 years
Maximum
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Defined contribution plan, employer matching contribution, percent of match		4.50%
Maximum \| Land and building improvements
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Property, plant and equipment, useful life		20 years
Maximum \| Furniture and equipment
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Property, plant and equipment, useful life		10 years
Accounting Standards Update 2016-01
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Equity securities, at fair value			$ 1,900,000
Reclassification of tax effect resulting from adoption					$ 0
Accounting Standards Update 2016-01 \| Retained Earnings
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Reclassification of tax effect resulting from adoption					$ 548,000
Columbia Financial Capital Trust I
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Ownership percentage by parent		100.00%
Stewardship Statutory Trust I
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Ownership percentage by parent		100.00%
Columbia Bank Employee Stock Ownership Plan
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Loan term	20 years	20 years
Stewardship Property
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Assets held-for-sale, long-lived, fair value disclosure		$ 1,800,000
Variable Interest Entity, Not Primary Beneficiary
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Assets				$ 7,000,000

Acquisition of Stewardship Fi_3

Acquisition of Stewardship Financial Corporation - Narrative (Details) $ / shares in Units, $ in Thousands	Nov. 01, 2019USD ($)branch$ / shares	Dec. 31, 2017USD ($)	Dec. 31, 2019USD ($)	Dec. 31, 2018USD ($)	Sep. 30, 2017USD ($)
Business Acquisition [Line Items]
Assets			$ 8,188,694	$ 6,691,618
Loans receivable, net			6,135,857	4,916,840
Liabilities			7,206,177	5,719,558
Deposits			5,645,842	4,413,873
Borrowings			1,407,022	1,189,180
Merger-related expenses		$ 0	2,755	0	$ 0
Goodwill			60,763	$ 5,716
Stewardship Financial Corporation
Business Acquisition [Line Items]
Business acquisition, share price (in dollars per share) \| $ / shares	$ 15.75
Merger-related expenses			$ 2,800
Goodwill	$ 55,047
Stewardship Financial Corporation
Business Acquisition [Line Items]
Assets	956,000
Loans receivable, net	756,900
Securities	52,600
Liabilities	877,800
Deposits	781,400
Borrowings	$ 81,800
Number of stores \| branch	12
Core Deposits \| Stewardship Financial Corporation
Business Acquisition [Line Items]
Core deposit intangible	$ 7,500
Acquired finite-lived intangible assets, weighted average useful life	10 years
Leasehold Improvements And Equipment \| Minimum \| Stewardship Financial Corporation
Business Acquisition [Line Items]
Property, plant and equipment, useful life	3 years
Leasehold Improvements And Equipment \| Maximum \| Stewardship Financial Corporation
Business Acquisition [Line Items]
Property, plant and equipment, useful life	10 years

Acquisition of Stewardship Fi_4

Acquisition of Stewardship Financial Corporation - Assets Acquired and Liabilities Assumed through the Merger Fair Value (Details) - USD ($) $ in Thousands	Nov. 01, 2019	Dec. 31, 2019	Dec. 31, 2018
Liabilities assumed:
Goodwill		$ 60,763	$ 5,716
Stewardship Financial Corporation
Assets acquired:
Cash and cash equivalents	$ 105,006
Debt securities available for sale	51,710
Equity securities	1,073
Federal Home Loan Bank stock	3,716
Loans receivable	757,223
Accrued interest receivable	2,239
Office properties and equipment, net	6,815
Bank-owned life insurance	22,096
Deferred tax assets, net	3,534
Core deposit and other intangibles	7,467
Other assets	767
Total assets acquired	961,646
Liabilities assumed:
Deposits	782,698
Borrowings	82,761
Advance payments by borrowers for taxes and insurance	356
Accrued expenses and other liabilities	14,584
Total liabilities assumed	880,399
Net assets acquired	81,247
Cash paid for purchase	136,294
Goodwill	$ 55,047

Debt Securities Available for_3

Debt Securities Available for Sale - Securities Available-for-Sale (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Debt Securities, Available-for-sale [Line Items]
Securities available-for-sale, amortized cost	$ 1,086,143	$ 1,049,932
Securities available-for-sale, gross unrealized (losses)	14,248	2,994
Securities available-for-sale, gross unrealized (losses)	(2,055)	(20,058)
Debt securities available for sale	1,098,336	1,032,868
U.S. government and agency obligations
Debt Securities, Available-for-sale [Line Items]
Securities available-for-sale, amortized cost	42,081	54,821
Securities available-for-sale, gross unrealized (losses)	321	53
Securities available-for-sale, gross unrealized (losses)	(16)	(717)
Debt securities available for sale	42,386	54,157
Mortgage-backed securities and collateralized mortgage obligations
Debt Securities, Available-for-sale [Line Items]
Securities available-for-sale, amortized cost	968,165	934,631
Securities available-for-sale, gross unrealized (losses)	12,981	2,812
Securities available-for-sale, gross unrealized (losses)	(1,265)	(17,436)
Debt securities available for sale	979,881	920,007
Municipal obligations
Debt Securities, Available-for-sale [Line Items]
Securities available-for-sale, amortized cost	2,284	987
Securities available-for-sale, gross unrealized (losses)	1	0
Securities available-for-sale, gross unrealized (losses)	(1)	0
Debt securities available for sale	2,284	987
Corporate debt securities
Debt Securities, Available-for-sale [Line Items]
Securities available-for-sale, amortized cost	68,613	54,493
Securities available-for-sale, gross unrealized (losses)	945	129
Securities available-for-sale, gross unrealized (losses)	(378)	(1,155)
Debt securities available for sale	69,180	53,467
Trust preferred securities
Debt Securities, Available-for-sale [Line Items]
Securities available-for-sale, amortized cost	5,000	5,000
Securities available-for-sale, gross unrealized (losses)	0	0
Securities available-for-sale, gross unrealized (losses)	(395)	(750)
Debt securities available for sale	$ 4,605	$ 4,250

Debt Securities Available for_4

Debt Securities Available for Sale - Expected Maturities of Available-for-Sale Securities (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Amortized Cost
Securities available-for-sale, amortized cost	$ 1,086,143	$ 1,049,932
Fair Value
Securities available for sale, at fair value	1,098,336	1,032,868
Debt Securities Excluding Mortgage-Based Securities
Amortized Cost
One year or less	31,901
More than one year to five years	27,366
More than five years to ten years	53,235
More than ten years	5,476
Securities available-for-sale, amortized cost	117,978
Fair Value
One year or less	31,955
More than one year to five years	27,729
More than five years to ten years	53,669
More than ten years	5,102
Securities available for sale, at fair value	118,455
Mortgage-backed securities and collateralized mortgage obligations
Amortized Cost
Securities available-for-sale, amortized cost	968,165	934,631
Fair Value
Securities available for sale, at fair value	$ 979,881	$ 920,007

Debt Securities Available for_5

Debt Securities Available for Sale - Narrative (Details)	3 Months Ended	12 Months Ended
Debt Securities Available for Sale - Narrative (Details)	Dec. 31, 2017USD ($)	Dec. 31, 2019USD ($)security	Dec. 31, 2018USD ($)security	Dec. 31, 2017USD ($)	Sep. 30, 2017USD ($)
Debt Securities, Available-for-sale [Line Items]
Securities available-for-sale, amortized cost		$ 1,086,143,000	$ 1,049,932,000
Debt securities available for sale, at fair value		1,098,336,000	1,032,868,000
Proceeds from sales of debt securities available for sale	$ 0	65,198,000	11,513,000	$ 0	$ 187,376,000
Debt securities, available-for-sale securities, gross realized gains		2,200,000			1,500,000
Debt securities, available-for-sale, gross unrealized losses		22,000			3,200,000
Proceeds from calls and maturities of debt securities, available-for-sale		24,100,000	11,500,000		17,200,000
Calls of debt securities, available-for-sale, realized gain		174,000	116,000
Calls of debt securities, available-for-sale, unrealized loss		$ 0	0
Debt securities, available-for-sale, number of matured debt securities \| security		1
Proceeds from sale and maturity of debt securities, available for sale		$ 797,000	2,400,000
Debt securities, available-for-sale, restricted		$ 462,000,000	$ 232,700,000
Number of unrealized loss positions \| security		97	151
Other-than-temporary impairment loss, debt securities, available for sale	$ 0	$ 0	$ 0		$ 0
Mortgage-backed securities and collateralized mortgage obligations
Debt Securities, Available-for-sale [Line Items]
Securities available-for-sale, amortized cost		968,165,000	934,631,000
Debt securities available for sale, at fair value		$ 979,881,000	$ 920,007,000

Debt Securities Available for_6

Debt Securities Available for Sale - Continuous Unrealized Loss Position of Available-for-Sale Securities (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Debt Securities, Available-for-sale [Line Items]
Less than 12 months, fair value	$ 187,055	$ 217,762
Less than 12 months, gross unrealized (losses)	(965)	(1,748)
12 months or longer, fair value	72,428	552,442
12 months or longer, gross unrealized (losses)	(1,090)	(18,310)
Total, fair value	259,483	770,204
Total, gross unrealized (losses)	(2,055)	(20,058)
U.S. government and agency obligations
Debt Securities, Available-for-sale [Line Items]
Less than 12 months, fair value	5,106	14,668
Less than 12 months, gross unrealized (losses)	(13)	(202)
12 months or longer, fair value	4,988	29,437
12 months or longer, gross unrealized (losses)	(3)	(515)
Total, fair value	10,094	44,105
Total, gross unrealized (losses)	(16)	(717)
Mortgage-backed securities and collateralized mortgage obligations
Debt Securities, Available-for-sale [Line Items]
Less than 12 months, fair value	178,665	176,614
Less than 12 months, gross unrealized (losses)	(946)	(1,034)
12 months or longer, fair value	58,208	509,397
12 months or longer, gross unrealized (losses)	(319)	(16,402)
Total, fair value	236,873	686,011
Total, gross unrealized (losses)	(1,265)	(17,436)
Municipal obligations
Debt Securities, Available-for-sale [Line Items]
Less than 12 months, fair value	696
Less than 12 months, gross unrealized (losses)	(1)
12 months or longer, fair value	0
12 months or longer, gross unrealized (losses)	0
Total, fair value	696
Total, gross unrealized (losses)	(1)
Corporate debt securities
Debt Securities, Available-for-sale [Line Items]
Less than 12 months, fair value	2,588	26,480
Less than 12 months, gross unrealized (losses)	(5)	(512)
12 months or longer, fair value	4,627	9,358
12 months or longer, gross unrealized (losses)	(373)	(643)
Total, fair value	7,215	35,838
Total, gross unrealized (losses)	(378)	(1,155)
Trust preferred securities
Debt Securities, Available-for-sale [Line Items]
Less than 12 months, fair value	0	0
Less than 12 months, gross unrealized (losses)	0	0
12 months or longer, fair value	4,605	4,250
12 months or longer, gross unrealized (losses)	(395)	(750)
Total, fair value	4,605	4,250
Total, gross unrealized (losses)	$ (395)	$ (750)

Debt Securities Held-to-Maturit

Debt Securities Held-to-Maturity (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Schedule of Held-to-maturity Securities [Line Items]
Amortized cost	$ 285,756	$ 262,143
Gross unrealized gains	4,074	73
Gross unrealized (losses)	(325)	(7,375)
Debt securities held to maturity	289,505	254,841
U.S. government and agency obligations
Schedule of Held-to-maturity Securities [Line Items]
Amortized cost	20,000	23,404
Gross unrealized gains	26	45
Gross unrealized (losses)	(66)	(208)
Debt securities held to maturity	19,960	23,241
Mortgage-backed securities and collateralized mortgage obligations
Schedule of Held-to-maturity Securities [Line Items]
Amortized cost	265,756	238,739
Gross unrealized gains	4,048	28
Gross unrealized (losses)	(259)	(7,167)
Debt securities held to maturity	$ 269,545	$ 231,600

Debt Securities Held to Matur_3

Debt Securities Held to Maturity - Expected Maturities of Held-to-Maturity Securities (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Amortized cost
Amortized cost	$ 285,756	$ 262,143
Fair value
Fair value	289,505	254,841
U.S. government and agency obligations
Amortized cost
More than ten years	20,000
Amortized cost	20,000	23,404
Fair value
More than ten years	19,960
Fair value	19,960	23,241
Mortgage-backed securities and collateralized mortgage obligations
Amortized cost
Amortized cost	265,756	238,739
Fair value
Fair value	$ 269,545	$ 231,600

Debt Securities Held to Matur_4

Debt Securities Held to Maturity - Narrative (Details)	3 Months Ended	12 Months Ended
Debt Securities Held to Maturity - Narrative (Details)	Dec. 31, 2017USD ($)	Dec. 31, 2019USD ($)security	Dec. 31, 2018USD ($)security	Sep. 30, 2017USD ($)
Schedule of Held-to-maturity Securities [Line Items]
Amortized cost		$ 285,756,000	$ 262,143,000
Securities held-to-maturity, fair value		289,505,000	254,841,000
Proceeds from sale of held-to-maturity securities	$ 0	0	0	$ 0
Proceeds from calls and maturities of debt securities held to maturity	0	33,400,000	5,400,000	769,000
Debt securities, held-to-maturity, realized gain		24,000	0	0
Debt securities, held-to-maturity, sold, realized loss		0
Securities available-for-sale sold under agreements		$ 236,000,000	$ 187,000,000
Number of unrealized loss positions \| security		22	88
Other-than-temporary impairment loss, debt securities, held-to-maturity, before tax	0	$ 0	$ 0	0
Transfer of securities from available for sale securities	$ 0	0	0	103,680,000
Transfer of securities from available for sale securities, fair value				$ 103,300,000
Mortgage-backed securities and collateralized mortgage obligations
Schedule of Held-to-maturity Securities [Line Items]
Amortized cost		265,756,000	238,739,000
Securities held-to-maturity, fair value		$ 269,545,000	$ 231,600,000

Debt Securities Held to Matur_5

Debt Securities Held to Maturity - Continuous Unrealized Loss Position of Held-to-Maturity Securities (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Schedule of Held-to-maturity Securities [Line Items]
Less than 12 months, Fair Value	$ 37,845	$ 11,265
Less than 12 months, Gross unrealized (losses)	(317)	(69)
12 months or longer, Fair value	772	221,443
12 months or longer, Gross unrealized (losses)	(8)	(7,306)
Total, Fair value	38,617	232,708
Total, Gross unrealized (losses)	(325)	(7,375)
U.S. government and agency obligations
Schedule of Held-to-maturity Securities [Line Items]
Less than 12 months, Fair Value	9,934	0
Less than 12 months, Gross unrealized (losses)	(66)	0
12 months or longer, Fair value	0	8,197
12 months or longer, Gross unrealized (losses)	0	(208)
Total, Fair value	9,934	8,197
Total, Gross unrealized (losses)	(66)	(208)
Mortgage-backed securities and collateralized mortgage obligations
Schedule of Held-to-maturity Securities [Line Items]
Less than 12 months, Fair Value	27,911	11,265
Less than 12 months, Gross unrealized (losses)	(251)	(69)
12 months or longer, Fair value	772	213,246
12 months or longer, Gross unrealized (losses)	(8)	(7,098)
Total, Fair value	28,683	224,511
Total, Gross unrealized (losses)	$ (259)	$ (7,167)

Equity Securities at Fair Val_2

Equity Securities at Fair Value - Narrative (Details) - USD ($)	3 Months Ended	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2019	Dec. 31, 2018	Sep. 30, 2017	Jan. 01, 2019
Debt and Equity Securities, FV-NI [Line Items]
Equity securities, at fair value		$ 2,855,000	$ 1,890,000
Increase (decrease) in fair value of equity securities	$ 0	305,000	0	$ 0
Proceeds from sale of equity securities	92,000	1,100,000	0	$ 0
Gross realized gain in equity securities	0	236,000
Gross realized losses in equity securities	$ 60,000	$ 0
Accounting Standards Update 2016-01
Debt and Equity Securities, FV-NI [Line Items]
Equity securities, at fair value			$ 1,900,000
Reclassification of tax effect resulting from adoption					$ 0
Retained Earnings \| Accounting Standards Update 2016-01
Debt and Equity Securities, FV-NI [Line Items]
Reclassification of tax effect resulting from adoption					$ 548,000

Loans Receivable and Allowanc_3

Loans Receivable and Allowance for Loan Losses - Loans Receivable (Details) - USD ($)	Dec. 31, 2019	Dec. 31, 2018
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total gross loans	$ 6,176,329,000	$ 4,962,289,000
Net deferred loan costs, fees and purchased premiums and discounts	21,237,000	16,893,000
Loans receivable	6,197,566,000	4,979,182,000
Real estate loans \| One-to-four family
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total gross loans	2,077,508,000	1,830,186,000
Real estate loans \| Multifamily and commercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total gross loans	2,924,851,000	2,142,154,000
Real estate loans \| Construction
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total gross loans	298,942,000	261,473,000
Commercial business loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total gross loans	484,941,000	333,876,000
Consumer loans \| Home equity loans and advances
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total gross loans	388,127,000	393,492,000
Consumer loans \| Other consumer loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total gross loans	1,960,000	1,108,000
Financial Asset, Other than Financial Asset Acquired with Credit Deterioration
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total gross loans	6,169,308,000	4,962,289,000
Financial Asset, Other than Financial Asset Acquired with Credit Deterioration \| Real estate loans \| One-to-four family
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total gross loans	2,077,079,000	1,830,186,000
Financial Asset, Other than Financial Asset Acquired with Credit Deterioration \| Real estate loans \| Multifamily and commercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total gross loans	2,919,985,000	2,142,154,000
Financial Asset, Other than Financial Asset Acquired with Credit Deterioration \| Real estate loans \| Construction
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total gross loans	298,942,000	261,473,000
Financial Asset, Other than Financial Asset Acquired with Credit Deterioration \| Commercial business loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total gross loans	483,215,000	333,876,000
Financial Asset, Other than Financial Asset Acquired with Credit Deterioration \| Consumer loans \| Home equity loans and advances
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total gross loans	388,127,000	393,492,000
Financial Asset, Other than Financial Asset Acquired with Credit Deterioration \| Consumer loans \| Other consumer loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total gross loans	1,960,000	1,108,000
Financial Asset Acquired with Credit Deterioration
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total gross loans	7,021,000	0
Loans receivable		$ 0
Financial Asset Acquired with Credit Deterioration \| Real estate loans \| One-to-four family
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total gross loans	429,000
Financial Asset Acquired with Credit Deterioration \| Real estate loans \| Multifamily and commercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total gross loans	4,866,000
Financial Asset Acquired with Credit Deterioration \| Real estate loans \| Construction
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total gross loans	0
Financial Asset Acquired with Credit Deterioration \| Commercial business loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total gross loans	1,726,000
Financial Asset Acquired with Credit Deterioration \| Consumer loans \| Home equity loans and advances
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total gross loans	0
Financial Asset Acquired with Credit Deterioration \| Consumer loans \| Other consumer loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total gross loans	$ 0

Loans Receivable and Allowanc_4

Loans Receivable and Allowance for Loan Losses - Narrative (Details)	3 Months Ended	12 Months Ended
	Dec. 31, 2017USD ($)	Dec. 31, 2019USD ($)loan	Dec. 31, 2018USD ($)loanproperty	Dec. 31, 2017USD ($)loan	Sep. 30, 2017USD ($)loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held-for-sale		$ 0	$ 8,100,000
Proceeds from sale of loans held-for-sale	$ 0				$ 0
Gain on sale of loans held-for-sale		718,000
Loss on sale of loans held-for-sale		0
Gain (loss) on sale of loans held-for-sale			0
Gain on sale of loans held-for-investment		67,000	618,000		0
Loss on sale of loans held-for-investment		0	0		380,000
Proceeds from sales of loans receivable	0	11,671,000	32,039,000		62,407,000
Purchases and grants of loans receivable	56,095,000	89,774,000	32,251,000		20,473,000
Carrying value of servicing liability		526,300,000	462,700,000
Servicing income	298,000	1,200,000	1,100,000		1,200,000
Loans receivable		$ 6,135,857,000	$ 4,916,840,000
Threshold period, past due status of financing receivables		30 days
Threshold period, past due for nonperforming status of financing receivables		90 days	90 days
Non-accrual loans		$ 6,687,000	$ 2,789,000
Loans past due			0
Increase in interest income if non-accrual had performed in line with their original terms	61,000	509,000	126,000		295,000
Cash basis interest income on non-accrual loans	121,000	437,000	89,000		104,000
Property acquired through foreclosure		$ 0	$ 92,000
Number of real estate properties acquired through foreclosure \| property			1
Number of loans in the process of foreclosure \| loan		4	14
Loans in process of foreclosure		$ 522,000	$ 1,600,000
Loan threshold for individual evaluation for impairment		500,000
Specific allowance for loan losses attributable to impaired loans		1,621,000	915,000
Impaired loans for which there are no related allowance for loan losses		10,747,000	11,647,000
Investment in troubled debt restructuring	17,600,000	$ 20,000,000	$ 16,000,000	$ 17,600,000	$ 21,100,000
Number of loans in troubled debt restructuring \| loan		1	7		7
Loans receivable		$ 6,197,566,000	$ 4,979,182,000
Less Than 90 Days
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-accrual loans		$ 1,500,000	0
Number of loans in non-accrual status \| loan		8
90 Days or More
Accounts, Notes, Loans and Financing Receivable [Line Items]
Investment in troubled debt restructuring	425,000		$ 101,000	$ 425,000	$ 1,000,000
Number of loans in troubled debt restructuring \| loan		0	1	2	7
30-59 Days
Accounts, Notes, Loans and Financing Receivable [Line Items]
Investment in troubled debt restructuring		$ 660,000	$ 1,000,000
Number of loans in troubled debt restructuring \| loan		3	7
Related Parties
Accounts, Notes, Loans and Financing Receivable [Line Items]
Purchases and grants of loans receivable	0	$ 0	$ 0		$ 390,000
Loans receivable		1,100,000	1,400,000
Freddie Mac
Accounts, Notes, Loans and Financing Receivable [Line Items]
Proceeds from sales of loans receivable	0	21,600,000	0		0
Home equity loans and advances
Accounts, Notes, Loans and Financing Receivable [Line Items]
Proceeds from sale of loans held-for-sale		97,400,000	3,600,000
Proceeds from sale of loans held-for-investment		5,300,000
Commercial real estate loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Proceeds from sale of loans held-for-sale		4,300,000
Proceeds from sale of loans held-for-investment		5,500,000
Commercial business loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Proceeds from sale of loans held-for-sale		164,000
Proceeds from sale of loans held-for-investment		901,000
Multifamily loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Proceeds from sale of loans held-for-investment			32,000,000		62,400,000
Multifamily and commercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Purchases and grants of loans receivable	$ 56,100,000	$ 89,800,000	32,300,000		$ 20,500,000
Financial Asset Acquired with Credit Deterioration
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans receivable			$ 0

Loans Receivable and Allowanc_5

Loans Receivable and Allowance for Loan Losses - Aging of Loans (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Financing Receivable, Past Due [Line Items]
Total	$ 6,176,329	$ 4,962,289
Real estate loans \| One-to-four family
Financing Receivable, Past Due [Line Items]
Total	2,077,508	1,830,186
Real estate loans \| Multifamily and commercial
Financing Receivable, Past Due [Line Items]
Total	2,924,851	2,142,154
Real estate loans \| Construction
Financing Receivable, Past Due [Line Items]
Total	298,942	261,473
Commercial business loans
Financing Receivable, Past Due [Line Items]
Total	484,941	333,876
Consumer loans \| Home equity loans and advances
Financing Receivable, Past Due [Line Items]
Total	388,127	393,492
Consumer loans \| Other consumer loans
Financing Receivable, Past Due [Line Items]
Total	1,960	1,108
Financial Asset, Other than Financial Asset Acquired with Credit Deterioration
Financing Receivable, Past Due [Line Items]
Total Past Due	18,478	18,196
Current	6,150,830	4,944,093
Total	6,169,308	4,962,289
Financial Asset, Other than Financial Asset Acquired with Credit Deterioration \| 30-59 Days
Financing Receivable, Past Due [Line Items]
Total Past Due	9,642	12,012
Financial Asset, Other than Financial Asset Acquired with Credit Deterioration \| 60-89 Days
Financing Receivable, Past Due [Line Items]
Total Past Due	3,588	3,395
Financial Asset, Other than Financial Asset Acquired with Credit Deterioration \| 90 Days or More
Financing Receivable, Past Due [Line Items]
Total Past Due	5,248	2,789
Financial Asset, Other than Financial Asset Acquired with Credit Deterioration \| Real estate loans \| One-to-four family
Financing Receivable, Past Due [Line Items]
Total Past Due	10,019	10,721
Current	2,067,060	1,819,465
Total	2,077,079	1,830,186
Financial Asset, Other than Financial Asset Acquired with Credit Deterioration \| Real estate loans \| One-to-four family \| 30-59 Days
Financing Receivable, Past Due [Line Items]
Total Past Due	6,249	8,384
Financial Asset, Other than Financial Asset Acquired with Credit Deterioration \| Real estate loans \| One-to-four family \| 60-89 Days
Financing Receivable, Past Due [Line Items]
Total Past Due	2,132	1,518
Financial Asset, Other than Financial Asset Acquired with Credit Deterioration \| Real estate loans \| One-to-four family \| 90 Days or More
Financing Receivable, Past Due [Line Items]
Total Past Due	1,638	819
Financial Asset, Other than Financial Asset Acquired with Credit Deterioration \| Real estate loans \| Multifamily and commercial
Financing Receivable, Past Due [Line Items]
Total Past Due	2,552	3,449
Current	2,917,433	2,138,705
Total	2,919,985	2,142,154
Financial Asset, Other than Financial Asset Acquired with Credit Deterioration \| Real estate loans \| Multifamily and commercial \| 30-59 Days
Financing Receivable, Past Due [Line Items]
Total Past Due	626	1,870
Financial Asset, Other than Financial Asset Acquired with Credit Deterioration \| Real estate loans \| Multifamily and commercial \| 60-89 Days
Financing Receivable, Past Due [Line Items]
Total Past Due	1,210	1,425
Financial Asset, Other than Financial Asset Acquired with Credit Deterioration \| Real estate loans \| Multifamily and commercial \| 90 Days or More
Financing Receivable, Past Due [Line Items]
Total Past Due	716	154
Financial Asset, Other than Financial Asset Acquired with Credit Deterioration \| Real estate loans \| Construction
Financing Receivable, Past Due [Line Items]
Total Past Due	0	0
Current	298,942	261,473
Total	298,942	261,473
Financial Asset, Other than Financial Asset Acquired with Credit Deterioration \| Real estate loans \| Construction \| 30-59 Days
Financing Receivable, Past Due [Line Items]
Total Past Due	0	0
Financial Asset, Other than Financial Asset Acquired with Credit Deterioration \| Real estate loans \| Construction \| 60-89 Days
Financing Receivable, Past Due [Line Items]
Total Past Due	0	0
Financial Asset, Other than Financial Asset Acquired with Credit Deterioration \| Real estate loans \| Construction \| 90 Days or More
Financing Receivable, Past Due [Line Items]
Total Past Due	0	0
Financial Asset, Other than Financial Asset Acquired with Credit Deterioration \| Commercial business loans
Financing Receivable, Past Due [Line Items]
Total Past Due	3,545	1,398
Current	479,670	332,478
Total	483,215	333,876
Financial Asset, Other than Financial Asset Acquired with Credit Deterioration \| Commercial business loans \| 30-59 Days
Financing Receivable, Past Due [Line Items]
Total Past Due	1,056	208
Financial Asset, Other than Financial Asset Acquired with Credit Deterioration \| Commercial business loans \| 60-89 Days
Financing Receivable, Past Due [Line Items]
Total Past Due	0	279
Financial Asset, Other than Financial Asset Acquired with Credit Deterioration \| Commercial business loans \| 90 Days or More
Financing Receivable, Past Due [Line Items]
Total Past Due	2,489	911
Financial Asset, Other than Financial Asset Acquired with Credit Deterioration \| Consumer loans \| Home equity loans and advances
Financing Receivable, Past Due [Line Items]
Total Past Due	2,359	2,628
Current	385,768	390,864
Total	388,127	393,492
Financial Asset, Other than Financial Asset Acquired with Credit Deterioration \| Consumer loans \| Home equity loans and advances \| 30-59 Days
Financing Receivable, Past Due [Line Items]
Total Past Due	1,708	1,550
Financial Asset, Other than Financial Asset Acquired with Credit Deterioration \| Consumer loans \| Home equity loans and advances \| 60-89 Days
Financing Receivable, Past Due [Line Items]
Total Past Due	246	173
Financial Asset, Other than Financial Asset Acquired with Credit Deterioration \| Consumer loans \| Home equity loans and advances \| 90 Days or More
Financing Receivable, Past Due [Line Items]
Total Past Due	405	905
Financial Asset, Other than Financial Asset Acquired with Credit Deterioration \| Consumer loans \| Other consumer loans
Financing Receivable, Past Due [Line Items]
Total Past Due	3	0
Current	1,957	1,108
Total	1,960	1,108
Financial Asset, Other than Financial Asset Acquired with Credit Deterioration \| Consumer loans \| Other consumer loans \| 30-59 Days
Financing Receivable, Past Due [Line Items]
Total Past Due	3	0
Financial Asset, Other than Financial Asset Acquired with Credit Deterioration \| Consumer loans \| Other consumer loans \| 60-89 Days
Financing Receivable, Past Due [Line Items]
Total Past Due	0	0
Financial Asset, Other than Financial Asset Acquired with Credit Deterioration \| Consumer loans \| Other consumer loans \| 90 Days or More
Financing Receivable, Past Due [Line Items]
Total Past Due	$ 0	$ 0

Loans Receivable and Allowanc_6

Loans Receivable and Allowance for Loan Losses - PCI Loans Acquired (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Nov. 01, 2019	Dec. 31, 2018
Receivables [Abstract]
Contractually required principal and interest		$ 9,286
Contractual cash flows not expected to be collected (non-accretable difference)		(1,823)
Expected cash flows to be collected		7,463
Interest component of expected cash flows (accretable yield)	$ 511	(556)	$ 0
Fair value of acquired loans		$ 6,907

Loans Receivable and Allowanc_7

Loans Receivable and Allowance for Loan Losses - Accretable Yield for PCI Loans (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2018USD ($)
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Accretable Yield Movement Schedule [Roll Forward]
Acquisition	$ 556
Accretion	(30)
Net increase in expected cash flows	(15)
Balance, end of period	$ 0

Loans Receivable and Allowanc_8

Loans Receivable and Allowance for Loan Losses - Non-accrual Status of Loans (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivable, recorded investment, nonaccrual status	$ 6,687	$ 2,789
Commercial business loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivable, recorded investment, nonaccrual status	3,686	911
One-to-four family \| Real estate loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivable, recorded investment, nonaccrual status	1,732	819
Multifamily and commercial \| Real estate loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivable, recorded investment, nonaccrual status	716	154
Home equity loans and advances \| Consumer loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivable, recorded investment, nonaccrual status	$ 553	$ 905

Loans Receivable and Allowanc_9

Loans Receivable and Allowance for Loan Losses - Allowance for Loan Losses (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Sep. 30, 2016
Allowance for loan losses:
Individually evaluated for impairment		$ 915
Collectively evaluated for impairment		61,427
Total	$ 61,709	62,342	$ 58,178	$ 54,633	$ 51,867
Total loans:
Individually evaluated for impairment		17,787
Collectively evaluated for impairment		4,944,502
Total	6,176,329	4,962,289
Real estate loans \| One-to-four family
Allowance for loan losses:
Individually evaluated for impairment		537
Collectively evaluated for impairment		14,695
Total	13,780	15,232	19,991	18,533	18,638
Total loans:
Individually evaluated for impairment		9,048
Collectively evaluated for impairment		1,821,138
Total	2,077,508	1,830,186
Real estate loans \| Multifamily and commercial
Allowance for loan losses:
Individually evaluated for impairment		0
Collectively evaluated for impairment		23,251
Total	22,980	23,251	19,933	18,029	17,390
Total loans:
Individually evaluated for impairment		2,695
Collectively evaluated for impairment		2,139,459
Total	2,924,851	2,142,154
Real estate loans \| Construction
Allowance for loan losses:
Individually evaluated for impairment		0
Collectively evaluated for impairment		7,217
Total	7,435	7,217	5,217	5,299	5,960
Total loans:
Individually evaluated for impairment		0
Collectively evaluated for impairment		261,473
Total	298,942	261,473
Commercial business loans
Allowance for loan losses:
Individually evaluated for impairment		366
Collectively evaluated for impairment		13,810
Total	15,836	14,176	8,275	8,480	5,721
Total loans:
Individually evaluated for impairment		2,944
Collectively evaluated for impairment		330,932
Total	484,941	333,876
Consumer loans \| Home equity loans and advances
Allowance for loan losses:
Individually evaluated for impairment		12
Collectively evaluated for impairment		2,446
Total	1,669	2,458	4,576	4,190	4,052
Total loans:
Individually evaluated for impairment		3,100
Collectively evaluated for impairment		390,392
Total	388,127	393,492
Consumer loans \| Other consumer loans
Allowance for loan losses:
Individually evaluated for impairment		0
Collectively evaluated for impairment		8
Total	9	8	8	8	11
Total loans:
Individually evaluated for impairment		0
Collectively evaluated for impairment		1,108
Total	1,960	1,108
Unallocated
Allowance for loan losses:
Individually evaluated for impairment		0
Collectively evaluated for impairment		0
Total	0	0	$ 178	$ 94	$ 95
Total loans:
Individually evaluated for impairment		0
Collectively evaluated for impairment		0
Total	0	0
Financial Asset, Other than Financial Asset Acquired with Credit Deterioration
Allowance for loan losses:
Individually evaluated for impairment	1,621
Collectively evaluated for impairment	60,088
Total loans:
Individually evaluated for impairment	18,811
Collectively evaluated for impairment	6,150,497
Total	6,169,308	4,962,289
Financial Asset, Other than Financial Asset Acquired with Credit Deterioration \| Real estate loans \| One-to-four family
Allowance for loan losses:
Individually evaluated for impairment	484
Collectively evaluated for impairment	13,296
Total loans:
Individually evaluated for impairment	8,891
Collectively evaluated for impairment	2,068,188
Total	2,077,079	1,830,186
Financial Asset, Other than Financial Asset Acquired with Credit Deterioration \| Real estate loans \| Multifamily and commercial
Allowance for loan losses:
Individually evaluated for impairment	2
Collectively evaluated for impairment	22,978
Total loans:
Individually evaluated for impairment	2,599
Collectively evaluated for impairment	2,917,386
Total	2,919,985	2,142,154
Financial Asset, Other than Financial Asset Acquired with Credit Deterioration \| Real estate loans \| Construction
Allowance for loan losses:
Individually evaluated for impairment	0
Collectively evaluated for impairment	7,435
Total loans:
Individually evaluated for impairment	0
Collectively evaluated for impairment	298,942
Total	298,942	261,473
Financial Asset, Other than Financial Asset Acquired with Credit Deterioration \| Commercial business loans
Allowance for loan losses:
Individually evaluated for impairment	1,121
Collectively evaluated for impairment	14,715
Total loans:
Individually evaluated for impairment	5,178
Collectively evaluated for impairment	478,037
Total	483,215	333,876
Financial Asset, Other than Financial Asset Acquired with Credit Deterioration \| Consumer loans \| Home equity loans and advances
Allowance for loan losses:
Individually evaluated for impairment	14
Collectively evaluated for impairment	1,655
Total loans:
Individually evaluated for impairment	2,143
Collectively evaluated for impairment	385,984
Total	388,127	393,492
Financial Asset, Other than Financial Asset Acquired with Credit Deterioration \| Consumer loans \| Other consumer loans
Allowance for loan losses:
Individually evaluated for impairment	0
Collectively evaluated for impairment	9
Total loans:
Individually evaluated for impairment	0
Collectively evaluated for impairment	1,960
Total	1,960	1,108
Financial Asset, Other than Financial Asset Acquired with Credit Deterioration \| Unallocated
Allowance for loan losses:
Individually evaluated for impairment	0
Collectively evaluated for impairment	0
Total loans:
Individually evaluated for impairment	0
Collectively evaluated for impairment	0
Financial Asset Acquired with Credit Deterioration
Allowance for loan losses:
Total	0
Total loans:
Total	7,021	$ 0
Financial Asset Acquired with Credit Deterioration \| Real estate loans \| One-to-four family
Allowance for loan losses:
Total	0
Total loans:
Total	429
Financial Asset Acquired with Credit Deterioration \| Real estate loans \| Multifamily and commercial
Allowance for loan losses:
Total	0
Total loans:
Total	4,866
Financial Asset Acquired with Credit Deterioration \| Real estate loans \| Construction
Allowance for loan losses:
Total	0
Total loans:
Total	0
Financial Asset Acquired with Credit Deterioration \| Commercial business loans
Allowance for loan losses:
Total	0
Total loans:
Total	1,726
Financial Asset Acquired with Credit Deterioration \| Consumer loans \| Home equity loans and advances
Allowance for loan losses:
Total	0
Total loans:
Total	0
Financial Asset Acquired with Credit Deterioration \| Consumer loans \| Other consumer loans
Allowance for loan losses:
Total	0
Total loans:
Total	0
Financial Asset Acquired with Credit Deterioration \| Unallocated
Allowance for loan losses:
Total	0
Total loans:
Total	$ 0

Loans Receivable and Allowan_10

Loans Receivable and Allowance for Loan Losses - Troubled Debt Restructuring (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2019USD ($)loan	Dec. 31, 2018USD ($)loan	Sep. 30, 2017USD ($)loan
Financing Receivable, Troubled Debt Restructuring [Line Items]
No. of Loans \| loan	1	7	7
Pre-modification Recorded Investment	$ 4,095	$ 1,454	$ 4,778
Post-modification Recorded Investment	$ 4,095	$ 1,454	$ 4,778
Real estate loans \| One-to-four family
Financing Receivable, Troubled Debt Restructuring [Line Items]
No. of Loans \| loan	0	5	3
Pre-modification Recorded Investment	$ 0	$ 801	$ 548
Post-modification Recorded Investment	$ 0	$ 801	$ 548
Real estate loans \| Multifamily and commercial
Financing Receivable, Troubled Debt Restructuring [Line Items]
No. of Loans \| loan	0	1	1
Pre-modification Recorded Investment	$ 0	$ 65	$ 3,964
Post-modification Recorded Investment	$ 0	$ 65	$ 3,964
Commercial business loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
No. of Loans \| loan	1	0	1
Pre-modification Recorded Investment	$ 4,095	$ 0	$ 18
Post-modification Recorded Investment	$ 4,095	$ 0	$ 18
Consumer loans \| Home equity loans and advances
Financing Receivable, Troubled Debt Restructuring [Line Items]
No. of Loans \| loan	0	1	2
Pre-modification Recorded Investment	$ 0	$ 588	$ 248
Post-modification Recorded Investment	$ 0	$ 588	$ 248

Loans Receivable and Allowan_11

Loans Receivable and Allowance for Loan Losses - Rollforward of Allowance for Loan Losses (Details) - USD ($) $ in Thousands	3 Months Ended													12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Dec. 31, 2019	Dec. 31, 2018	Sep. 30, 2017
Allowance for loan losses:
Beginning balance				$ 62,342				$ 58,178	$ 54,633				$ 51,867	$ 62,342	$ 58,178	$ 51,867
Provision for loan losses	$ 2,519	$ 1,157	$ 112	436	$ 777	$ 1,500	$ 2,400	2,000	3,400	$ 5,676	$ 375	$ 375	0	4,224	6,677	6,426
Recoveries									188					496	707	584
Charge-offs									(43)					(5,353)	(3,220)	(4,244)
Ending balance	61,709				62,342				58,178	54,633				61,709	62,342	54,633
Real estate loans \| One-to-four family
Allowance for loan losses:
Beginning balance				15,232				19,991	18,533				18,638	15,232	19,991	18,638
Provision for loan losses									1,473					(429)	(4,503)	1,029
Recoveries									9					30	334	268
Charge-offs									(24)					(1,053)	(590)	(1,402)
Ending balance	13,780				15,232				19,991	18,533				13,780	15,232	18,533
Real estate loans \| Multifamily and commercial
Allowance for loan losses:
Beginning balance				23,251				19,933	18,029				17,390	23,251	19,933	17,390
Provision for loan losses									1,906					(178)	3,445	1,644
Recoveries									0					10	2	75
Charge-offs									(2)					(103)	(129)	(1,080)
Ending balance	22,980				23,251				19,933	18,029				22,980	23,251	18,029
Real estate loans \| Construction
Allowance for loan losses:
Beginning balance				7,217				5,217	5,299				5,960	7,217	5,217	5,960
Provision for loan losses									(82)					216	1,997	(661)
Recoveries									0					2	3	0
Charge-offs									0					0	0	0
Ending balance	7,435				7,217				5,217	5,299				7,435	7,217	5,299
Commercial business loans
Allowance for loan losses:
Beginning balance				14,176				8,275	8,480				5,721	14,176	8,275	5,721
Provision for loan losses									(373)					5,250	7,860	3,183
Recoveries									171					404	240	182
Charge-offs									(3)					(3,994)	(2,199)	(606)
Ending balance	15,836				14,176				8,275	8,480				15,836	14,176	8,480
Consumer loans \| Home equity loans and advances
Allowance for loan losses:
Beginning balance				2,458				4,576	4,190				4,052	2,458	4,576	4,052
Provision for loan losses									389					(638)	(1,949)	1,219
Recoveries									6					50	122	59
Charge-offs									(9)					(201)	(291)	(1,140)
Ending balance	1,669				2,458				4,576	4,190				1,669	2,458	4,190
Consumer loans \| Other consumer loans
Allowance for loan losses:
Beginning balance				8				8	8				11	8	8	11
Provision for loan losses									3					3	5	13
Recoveries									2					0	6	0
Charge-offs									(5)					(2)	(11)	(16)
Ending balance	9				8				8	8				9	8	8
Unallocated
Allowance for loan losses:
Beginning balance				$ 0				$ 178	94				$ 95	0	178	95
Provision for loan losses									84					0	(178)	(1)
Recoveries									0					0	0	0
Charge-offs									0					0	0	0
Ending balance	$ 0				$ 0				$ 178	$ 94				$ 0	$ 0	$ 94

Loans Receivable and Allowan_12

Loans Receivable and Allowance for Loan Losses - Loans Individually Evaluated for Impairment (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Financing Receivable, Impaired [Line Items]
With no allowance recorded: Recorded investment	$ 10,747	$ 11,647
With no allowance recorded: Unpaid principal balance	12,929	14,029
With a specific allowance recorded: Recorded investment	8,064	6,140
With a specific allowance recorded: Unpaid principal balance	11,088	6,296
Recorded investment	18,811	17,787
Unpaid principal balance	24,017	20,325
Specific allowance	1,621	915
Real estate loans \| One-to-four family
Financing Receivable, Impaired [Line Items]
With no allowance recorded: Recorded investment	4,314	4,156
With no allowance recorded: Unpaid principal balance	5,473	5,307
With a specific allowance recorded: Recorded investment	4,577	4,892
With a specific allowance recorded: Unpaid principal balance	4,613	4,939
Recorded investment	8,891	9,048
Unpaid principal balance	10,086	10,246
Specific allowance	484	537
Real estate loans \| Multifamily and commercial
Financing Receivable, Impaired [Line Items]
With no allowance recorded: Recorded investment	1,494	2,695
With no allowance recorded: Unpaid principal balance	2,191	3,482
With a specific allowance recorded: Recorded investment	1,105
With a specific allowance recorded: Unpaid principal balance	1,105
Recorded investment	2,599	2,695
Unpaid principal balance	3,296	3,482
Specific allowance	2	0
Commercial business loans
Financing Receivable, Impaired [Line Items]
With no allowance recorded: Recorded investment	3,859	2,285
With no allowance recorded: Unpaid principal balance	4,048	2,374
With a specific allowance recorded: Recorded investment	1,319	659
With a specific allowance recorded: Unpaid principal balance	4,307	768
Recorded investment	5,178	2,944
Unpaid principal balance	8,355	3,142
Specific allowance	1,121	366
Consumer loans \| Home equity loans and advances
Financing Receivable, Impaired [Line Items]
With no allowance recorded: Recorded investment	1,080	2,511
With no allowance recorded: Unpaid principal balance	1,217	2,866
With a specific allowance recorded: Recorded investment	1,063	589
With a specific allowance recorded: Unpaid principal balance	1,063	589
Recorded investment	2,143	3,100
Unpaid principal balance	2,280	3,455
Specific allowance	$ 14	$ 12

Loans Receivable and Allowan_13

Loans Receivable and Allowance for Loan Losses - Interest Income on Impaired Loans (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2019	Dec. 31, 2018	Sep. 30, 2017
Financing Receivable, Impaired [Line Items]
Average recorded Investment	$ 25,590	$ 21,240	$ 19,357	$ 27,054
Interest Income Recognized	230	1,203	891	1,079
Real estate loans \| One-to-four family
Financing Receivable, Impaired [Line Items]
Average recorded Investment	14,015	8,811	10,224	15,027
Interest Income Recognized	110	434	445	469
Real estate loans \| Multifamily and commercial
Financing Receivable, Impaired [Line Items]
Average recorded Investment	4,087	2,639	2,712	4,328
Interest Income Recognized	39	147	155	279
Real estate loans \| Construction
Financing Receivable, Impaired [Line Items]
Average recorded Investment		850	0
Interest Income Recognized		0	0
Commercial business loans
Financing Receivable, Impaired [Line Items]
Average recorded Investment	3,870	6,378	3,060	3,796
Interest Income Recognized	46	479	118	195
Consumer loans \| Home equity loans and advances
Financing Receivable, Impaired [Line Items]
Average recorded Investment	3,618	2,562	3,361	3,903
Interest Income Recognized	$ 35	$ 143	$ 173	$ 136

Loans Receivable and Allowan_14

Loans Receivable and Allowance for Loan Losses - Credit Quality Indicators (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Financing Receivable, Credit Quality Indicator [Line Items]
Total gross loans	$ 6,176,329	$ 4,962,289
Real estate loans \| One-to-four family
Financing Receivable, Credit Quality Indicator [Line Items]
Total gross loans	2,077,508	1,830,186
Real estate loans \| Multifamily and commercial
Financing Receivable, Credit Quality Indicator [Line Items]
Total gross loans	2,924,851	2,142,154
Real estate loans \| Construction
Financing Receivable, Credit Quality Indicator [Line Items]
Total gross loans	298,942	261,473
Commercial business loans
Financing Receivable, Credit Quality Indicator [Line Items]
Total gross loans	484,941	333,876
Consumer loans \| Home equity loans and advances
Financing Receivable, Credit Quality Indicator [Line Items]
Total gross loans	388,127	393,492
Consumer loans \| Other consumer loans
Financing Receivable, Credit Quality Indicator [Line Items]
Total gross loans	1,960	1,108
Financial Asset, Other than Financial Asset Acquired with Credit Deterioration
Financing Receivable, Credit Quality Indicator [Line Items]
Total gross loans	6,169,308	4,962,289
Financial Asset, Other than Financial Asset Acquired with Credit Deterioration \| Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Total gross loans	6,115,500	4,929,870
Financial Asset, Other than Financial Asset Acquired with Credit Deterioration \| Special mention
Financing Receivable, Credit Quality Indicator [Line Items]
Total gross loans	25,313	9,074
Financial Asset, Other than Financial Asset Acquired with Credit Deterioration \| Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Total gross loans	28,495	23,345
Financial Asset, Other than Financial Asset Acquired with Credit Deterioration \| Doubtful
Financing Receivable, Credit Quality Indicator [Line Items]
Total gross loans	0	0
Financial Asset, Other than Financial Asset Acquired with Credit Deterioration \| Real estate loans \| One-to-four family
Financing Receivable, Credit Quality Indicator [Line Items]
Total gross loans	2,077,079	1,830,186
Financial Asset, Other than Financial Asset Acquired with Credit Deterioration \| Real estate loans \| One-to-four family \| Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Total gross loans	2,072,878	1,826,066
Financial Asset, Other than Financial Asset Acquired with Credit Deterioration \| Real estate loans \| One-to-four family \| Special mention
Financing Receivable, Credit Quality Indicator [Line Items]
Total gross loans	419	0
Financial Asset, Other than Financial Asset Acquired with Credit Deterioration \| Real estate loans \| One-to-four family \| Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Total gross loans	3,782	4,120
Financial Asset, Other than Financial Asset Acquired with Credit Deterioration \| Real estate loans \| One-to-four family \| Doubtful
Financing Receivable, Credit Quality Indicator [Line Items]
Total gross loans	0	0
Financial Asset, Other than Financial Asset Acquired with Credit Deterioration \| Real estate loans \| Multifamily and commercial
Financing Receivable, Credit Quality Indicator [Line Items]
Total gross loans	2,919,985	2,142,154
Financial Asset, Other than Financial Asset Acquired with Credit Deterioration \| Real estate loans \| Multifamily and commercial \| Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Total gross loans	2,900,286	2,128,680
Financial Asset, Other than Financial Asset Acquired with Credit Deterioration \| Real estate loans \| Multifamily and commercial \| Special mention
Financing Receivable, Credit Quality Indicator [Line Items]
Total gross loans	4,724	0
Financial Asset, Other than Financial Asset Acquired with Credit Deterioration \| Real estate loans \| Multifamily and commercial \| Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Total gross loans	14,975	13,474
Financial Asset, Other than Financial Asset Acquired with Credit Deterioration \| Real estate loans \| Multifamily and commercial \| Doubtful
Financing Receivable, Credit Quality Indicator [Line Items]
Total gross loans	0	0
Financial Asset, Other than Financial Asset Acquired with Credit Deterioration \| Real estate loans \| Construction
Financing Receivable, Credit Quality Indicator [Line Items]
Total gross loans	298,942	261,473
Financial Asset, Other than Financial Asset Acquired with Credit Deterioration \| Real estate loans \| Construction \| Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Total gross loans	298,942	261,473
Financial Asset, Other than Financial Asset Acquired with Credit Deterioration \| Real estate loans \| Construction \| Special mention
Financing Receivable, Credit Quality Indicator [Line Items]
Total gross loans	0	0
Financial Asset, Other than Financial Asset Acquired with Credit Deterioration \| Real estate loans \| Construction \| Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Total gross loans	0	0
Financial Asset, Other than Financial Asset Acquired with Credit Deterioration \| Real estate loans \| Construction \| Doubtful
Financing Receivable, Credit Quality Indicator [Line Items]
Total gross loans	0	0
Financial Asset, Other than Financial Asset Acquired with Credit Deterioration \| Commercial business loans
Financing Receivable, Credit Quality Indicator [Line Items]
Total gross loans	483,215	333,876
Financial Asset, Other than Financial Asset Acquired with Credit Deterioration \| Commercial business loans \| Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Total gross loans	454,183	320,451
Financial Asset, Other than Financial Asset Acquired with Credit Deterioration \| Commercial business loans \| Special mention
Financing Receivable, Credit Quality Indicator [Line Items]
Total gross loans	20,170	9,074
Financial Asset, Other than Financial Asset Acquired with Credit Deterioration \| Commercial business loans \| Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Total gross loans	8,862	4,351
Financial Asset, Other than Financial Asset Acquired with Credit Deterioration \| Commercial business loans \| Doubtful
Financing Receivable, Credit Quality Indicator [Line Items]
Total gross loans	0	0
Financial Asset, Other than Financial Asset Acquired with Credit Deterioration \| Consumer loans \| Home equity loans and advances
Financing Receivable, Credit Quality Indicator [Line Items]
Total gross loans	388,127	393,492
Financial Asset, Other than Financial Asset Acquired with Credit Deterioration \| Consumer loans \| Home equity loans and advances \| Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Total gross loans	387,251	392,092
Financial Asset, Other than Financial Asset Acquired with Credit Deterioration \| Consumer loans \| Home equity loans and advances \| Special mention
Financing Receivable, Credit Quality Indicator [Line Items]
Total gross loans	0	0
Financial Asset, Other than Financial Asset Acquired with Credit Deterioration \| Consumer loans \| Home equity loans and advances \| Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Total gross loans	876	1,400
Financial Asset, Other than Financial Asset Acquired with Credit Deterioration \| Consumer loans \| Home equity loans and advances \| Doubtful
Financing Receivable, Credit Quality Indicator [Line Items]
Total gross loans	0	0
Financial Asset, Other than Financial Asset Acquired with Credit Deterioration \| Consumer loans \| Other consumer loans
Financing Receivable, Credit Quality Indicator [Line Items]
Total gross loans	1,960	1,108
Financial Asset, Other than Financial Asset Acquired with Credit Deterioration \| Consumer loans \| Other consumer loans \| Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Total gross loans	1,960	1,108
Financial Asset, Other than Financial Asset Acquired with Credit Deterioration \| Consumer loans \| Other consumer loans \| Special mention
Financing Receivable, Credit Quality Indicator [Line Items]
Total gross loans	0	0
Financial Asset, Other than Financial Asset Acquired with Credit Deterioration \| Consumer loans \| Other consumer loans \| Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Total gross loans	0	0
Financial Asset, Other than Financial Asset Acquired with Credit Deterioration \| Consumer loans \| Other consumer loans \| Doubtful
Financing Receivable, Credit Quality Indicator [Line Items]
Total gross loans	$ 0	$ 0

Office Properties and Equipme_3

Office Properties and Equipment, net - Schedule of Office Properties and Equipment (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Property, Plant and Equipment [Line Items]
Office property and equipment, gross	$ 130,795	$ 106,528
Less accumulated depreciation and amortization	57,828	54,478
Total office properties and equipment, net	72,967	52,050
Land
Property, Plant and Equipment [Line Items]
Office property and equipment, gross	11,069	7,829
Buildings
Property, Plant and Equipment [Line Items]
Office property and equipment, gross	27,340	24,018
Land and building improvements
Property, Plant and Equipment [Line Items]
Office property and equipment, gross	31,520	24,864
Leasehold improvements
Property, Plant and Equipment [Line Items]
Office property and equipment, gross	24,038	21,279
Furniture and equipment
Property, Plant and Equipment [Line Items]
Office property and equipment, gross	$ 36,828	$ 28,538

Office Properties and Equipme_4

Office Properties and Equipment, net - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2019	Dec. 31, 2018	Sep. 30, 2017
Property, Plant and Equipment [Line Items]
Depreciation and amortization	$ 863	$ 4,900	$ 3,800	$ 3,400
Land and building improvements
Property, Plant and Equipment [Line Items]
Property, plant and equipment, additions		1,300	$ 8,900
Stewardship Property
Property, Plant and Equipment [Line Items]
Assets held-for-sale, long-lived, fair value disclosure		$ 1,800

Goodwill and Intangible Asset_2

Goodwill and Intangible Assets - Schedule of Goodwill and Intangible Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Finite-Lived Intangible Assets [Line Items]
Goodwill	$ 60,763	$ 5,716
Goodwill and intangible assets	68,582	6,085
Core Deposits
Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible assets	7,245	0
Mortgage Servicing Rights
Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible assets	$ 574	$ 369

Goodwill and Intangible Asset_3

Goodwill and Intangible Assets - Narrative (Details) - USD ($)	3 Months Ended	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2019	Dec. 31, 2018	Sep. 30, 2017
Finite-Lived Intangible Assets [Line Items]
Amortization of intangible assets	$ 0	$ 222,000	$ 0	$ 0
Mortgage Servicing Rights
Finite-Lived Intangible Assets [Line Items]
Amortization of intangible assets	22,000	109,000	73,000	105,000
Core Deposits
Finite-Lived Intangible Assets [Line Items]
Amortization of intangible assets	$ 0	$ 222,000	$ 0	$ 0

Goodwill and Intangible Asset_4

Goodwill and Intangible Assets - Schedule of Amortization of Core Deposit Intangibles (Details) - Core Deposits $ in Thousands	Dec. 31, 2019USD ($)
Acquired Finite-Lived Intangible Assets [Line Items]
2020	$ 1,048
2021	1,024
2022	961
2023	892
2024	819
Thereafter	$ 2,501

Deposits - Schedule of Deposits

Deposits - Schedule of Deposits (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Balance
Non-interest-bearing demand	$ 958,442	$ 723,794
Interest-bearing demand	1,720,383	1,219,381
Money market accounts	410,392	259,694
Savings and club deposits	543,480	510,688
Certificates of deposit	2,013,145	1,700,316
Total deposits	$ 5,645,842	$ 4,413,873
Weighted Average Rate
Interest-bearing demand	1.03%	0.95%
Money market accounts	0.91%	0.67%
Savings and club deposits	0.15%	0.16%
Certificates of deposit	2.25%	2.01%
Total deposits	1.20%	1.09%

Deposits - Narrative (Details)

Deposits - Narrative (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Time Deposits [Line Items]
Interest-bearing demand	$ 1,720,383	$ 1,219,381
Aggregate amount of certificates of deposit exceeding threshold amount	1,100,000	$ 885,300
Stewardship Financial Corporation
Time Deposits [Line Items]
Interest-bearing demand	$ 31,600

Deposits - Schedule of Deposit

Deposits - Schedule of Deposit Maturities (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Banking and Thrift [Abstract]
One year or less	$ 1,293,613	$ 1,107,667
After one year to two years	548,995	326,800
After two years to three years	142,458	230,468
After three years to four years	11,362	24,939
After four years	16,717	10,442
Total term certificate accounts	$ 2,013,145	$ 1,700,316

Deposits - Interest Expense on

Deposits - Interest Expense on Deposits (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2019	Dec. 31, 2018	Sep. 30, 2017
Assets Sold under Agreements to Repurchase [Line Items]
Interest expense on deposits	$ 7,631	$ 61,551	$ 39,523	$ 25,581
Demand Deposits
Assets Sold under Agreements to Repurchase [Line Items]
Interest expense on deposits	2,509	19,922	12,933	8,556
Savings and Clubs
Assets Sold under Agreements to Repurchase [Line Items]
Interest expense on deposits	210	770	993	630
Certificates of Deposit
Assets Sold under Agreements to Repurchase [Line Items]
Interest expense on deposits	$ 4,912	$ 40,859	$ 25,597	$ 16,395

Borrowings - Schedule of borrow

Borrowings - Schedule of borrowed funds (Details) - USD ($)	Dec. 31, 2019	Dec. 31, 2018
Debt Instrument [Line Items]
Borrowings	$ 1,407,022,000	$ 1,189,180,000
Weighted Average Interest Rate	2.14%	2.43%
Overnight lines of credit
Debt Instrument [Line Items]
Borrowings	$ 107,800,000	$ 159,600,000
Weighted Average Interest Rate	1.81%	2.60%
Federal Home Loan Bank advances
Debt Instrument [Line Items]
Borrowings	$ 1,275,391,000	$ 1,029,580,000
Weighted Average Interest Rate	2.09%	2.40%
Subordinated notes
Debt Instrument [Line Items]
Borrowings	$ 16,899,000	$ 0
Weighted Average Interest Rate	6.75%	0.00%
Junior subordinated debt
Debt Instrument [Line Items]
Borrowings	$ 6,932,000	$ 0
Weighted Average Interest Rate	5.09%	0.00%

Borrowings - Narrative (Details

Borrowings - Narrative (Details) - USD ($)	3 Months Ended	12 Months Ended
Borrowings - Narrative (Details) - USD ($)	Dec. 31, 2017	Dec. 31, 2019	Dec. 31, 2018	Sep. 30, 2017
Debt Instrument [Line Items]
Borrowings		$ 1,407,022,000	$ 1,189,180,000
Unused line of credit		250,000,000	225,000,000
Advances from federal home loan banks		$ 1,900,000,000	$ 1,700,000,000
Weighted average interest rate		2.14%	2.43%
Line of Credit
Debt Instrument [Line Items]
Borrowings		$ 107,800,000	$ 159,600,000
Interest expense, debt	$ 70,000	$ 1,800,000	$ 2,200,000	$ 233,000
Weighted average interest rate		1.81%	2.60%
Federal Home Loan Bank advances
Debt Instrument [Line Items]
Borrowings		$ 1,275,391,000	$ 1,029,580,000
Interest expense, debt	3,300,000	$ 25,200,000	$ 17,100,000	12,800,000
Weighted average interest rate		2.09%	2.40%
Junior subordinated debt
Debt Instrument [Line Items]
Borrowings		$ 6,932,000	$ 0
Interest expense, debt	1,000,000	$ 113,000	$ 3,500,000	4,200,000
Weighted average interest rate		5.09%	0.00%
Subordinated notes
Debt Instrument [Line Items]
Borrowings		$ 16,899,000	$ 0
Interest expense, debt	0	$ 65,000	$ 0	0
Interest rate, effective percentage		5.09%
Weighted average interest rate		6.75%	0.00%
Interest rate, stated percentage		6.75%
Securities sold under agreements to repurchase
Debt Instrument [Line Items]
Interest expense, debt	$ 203,000	$ 0	$ 3,000	$ 1,600,000
Advances from federal home loan banks			246,200,000
Interest rate swaps \| Federal Home Loan Bank advances
Debt Instrument [Line Items]
Notional amount of derivative		$ 410,000,000	$ 320,000,000
London Interbank Offered Rate (LIBOR) \| Junior subordinated debt
Debt Instrument [Line Items]
Basis spread on variable rate		2.95%

Borrowings - Schedule of contra

Borrowings - Schedule of contractual maturity of borrowings (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Debt Instrument [Line Items]
Total FHLB advances	$ 1,407,022	$ 1,189,180
Line of Credit and FHLB Advances
Debt Instrument [Line Items]
One year or less	1,004,139
After one year to two years	178,723
After two years to three years	169,800
After three years to four years	20,529
After four years	10,000
Total FHLB advances	$ 1,383,191

Stockholders' Equity - Actual C

Stockholders' Equity - Actual Capital Amounts and Ratios (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Parent Company
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Capital conservation buffer, ratio	2.50%
Capital, amount	$ 1,061,555	$ 1,094,062
Capital to risk weighted assets, ratio	17.25%	23.45%
Capital required for capital adequacy, amount	$ 492,438	$ 373,276
Capital required for capital adequacy to risk weighted assets, ratio	8.00%	8.00%
Capital required for capital adequacy with capital buffer, amount	$ 646,324	$ 460,763
Capital required for capital adequacy with capital buffer to risk weighted assets, ratio	10.50%	9.88%
Tier one risk based capital, amount	$ 988,172	$ 1,035,477
Tier one risk based capital to risk weighted assets, ratio	16.05%	22.19%
Tier one risk based capital required for capital adequacy, amount	$ 369,328	$ 279,957
Tier one risk based capital required for capital adequacy to risk weighted assets, ratio	6.00%	6.00%
Tier one risk based capital required for capital adequacy with capital buffer, amount	$ 523,215	$ 367,444
Tier one risk based capital required for capital adequacy with capital buffer to risk weighted assets, ratio	8.50%	7.88%
Common equity tier one capital, amount	$ 980,995	$ 1,035,477
Common equity tier one capital ratio	15.94%	22.19%
Common equity tier one capital required for capital adequacy, amount	$ 276,996	$ 209,968
Common equity tier one capital required for capital adequacy to risk weighted assets, ratio	4.50%	4.50%
Common equity tier one risk based capital required for capital adequacy with capital buffer, amount	$ 430,883	$ 297,455
Common equity tier one risk based capital requirement for capital adequacy with capital buffer to risk weighted assets, ratio	7.00%	6.38%
Tier one leverage capital, amount	$ 988,172	$ 1,035,477
Tier one leverage capital to average assets, ratio	12.92%	15.75%
Tier one leverage capital required for capital adequacy, amount	$ 305,824	$ 263,037
Tier one leverage capital required for capital adequacy to average assets, ratio	4.00%	4.00%
Tier one leverage capital required for capital adequacy with capital buffer to average assets, amount	$ 305,824	$ 263,037
Tier one leverage capital requirement for capital adequacy with capital buffer to average assets, ratio	4.00%	4.00%
Subsidiaries
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Capital, amount	$ 844,664	$ 886,728
Capital to risk weighted assets, ratio	14.25%	19.04%
Capital required for capital adequacy, amount	$ 474,125	$ 372,550
Capital required for capital adequacy to risk weighted assets, ratio	8.00%	8.00%
Capital required for capital adequacy with capital buffer, amount	$ 622,290	$ 459,866
Capital required for capital adequacy with capital buffer to risk weighted assets, ratio	10.50%	9.88%
Capital required to be well capitalized, amount	$ 592,657	$ 465,687
Capital required to be well capitalized to risk weighted assets, ratio	10.00%	10.00%
Tier one risk based capital, amount	$ 782,881	$ 828,257
Tier one risk based capital to risk weighted assets, ratio	13.21%	17.79%
Tier one risk based capital required for capital adequacy, amount	$ 355,594	$ 279,412
Tier one risk based capital required for capital adequacy to risk weighted assets, ratio	6.00%	6.00%
Tier one risk based capital required for capital adequacy with capital buffer, amount	$ 503,758	$ 366,729
Tier one risk based capital required for capital adequacy with capital buffer to risk weighted assets, ratio	8.50%	7.88%
Tier one risk based capital required to be well capitalized, amount	$ 474,125	$ 372,550
Tier one risk based capital required to be well capitalized to risk weighted assets, ratio	8.00%	8.00%
Common equity tier one capital, amount	$ 782,881	$ 828,257
Common equity tier one capital ratio	13.21%	17.79%
Common equity tier one capital required for capital adequacy, amount	$ 266,696	$ 209,559
Common equity tier one capital required for capital adequacy to risk weighted assets, ratio	4.50%	4.50%
Common equity tier one risk based capital required for capital adequacy with capital buffer, amount	$ 414,860	$ 296,875
Common equity tier one risk based capital requirement for capital adequacy with capital buffer to risk weighted assets, ratio	7.00%	6.38%
Common equity tier one capital required to be well-capitalized, amount	$ 385,227	$ 302,697
Common equity tier one capital required to be well-capitalized to risk weighted assets, ratio	6.50%	6.50%
Tier one leverage capital, amount	$ 782,881	$ 828,257
Tier one leverage capital to average assets, ratio	10.25%	12.60%
Tier one leverage capital required for capital adequacy, amount	$ 305,423	$ 263,025
Tier one leverage capital required for capital adequacy to average assets, ratio	4.00%	4.00%
Tier one leverage capital required for capital adequacy with capital buffer to average assets, amount	$ 305,423	$ 263,025
Tier one leverage capital requirement for capital adequacy with capital buffer to average assets, ratio	4.00%	4.00%
Tier one leverage capital required to be well capitalized, amount	$ 381,779	$ 382,006
Tier one leverage capital required to be well capitalized to average assets, ratio	5.00%	5.00%

Stockholders' Equity - Narrativ

Stockholders' Equity - Narrative (Details) - USD ($) $ / shares in Units, $ in Thousands	Dec. 05, 2019	Jun. 13, 2019	Dec. 31, 2019
Banking and Thrift [Abstract]
Number of shares authorized to be repurchased (in shares)		4,000,000	3,543,800
Stock repurchase program, percent of common stock		3.50%
Additional shares acquired in stock repurchase program (in shares)	3,000,000
Cost method of shares repurchase			$ 55,309
Cost method of shares repurchased (in dollars per share)			$ 15.61

Employee Benefit Plans - Schedu

Employee Benefit Plans - Schedule of Change in Benefit Obligation and Plan Assets (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2019	Dec. 31, 2018	Sep. 30, 2017
Pension
Change in benefit obligation:
Benefit obligation, beginning balance		$ 209,205	$ 229,156
Service cost	$ 1,780	6,494	7,805	$ 7,621
Interest cost	2,128	8,569	8,489	8,444
Actuarial (gain) loss		46,001	(30,703)
Benefits paid		(6,443)	(5,542)
Benefit obligation, ending balance	229,156	263,826	209,205
Change in plan assets:
Fair value of plan assets, beginning balance		272,974	289,390
Actuarial return on plan assets		54,816	(10,874)
Employer contributions		35,000	0
Benefits paid		(6,443)	(5,542)
Fair value of plan assets, ending balance	289,390	356,347	272,974
Funded status at end of year		92,521	63,769
RIM
Change in benefit obligation:
Benefit obligation, beginning balance		11,285	12,243
Service cost	60	210	282	237
Interest cost	111	466	443	429
Actuarial (gain) loss		2,074	(1,355)
Benefits paid		(339)	(328)
Benefit obligation, ending balance	12,243	13,696	11,285
Change in plan assets:
Fair value of plan assets, beginning balance		0	0
Actuarial return on plan assets		0	0
Employer contributions		339	328
Benefits paid		(339)	(328)
Fair value of plan assets, ending balance	0	0	0
Funded status at end of year		(13,696)	(11,285)
Post-retirement
Change in benefit obligation:
Benefit obligation, beginning balance		20,964	22,078
Service cost	92	339	417	471
Interest cost	205	826	796	$ 742
Actuarial (gain) loss		3,141	(1,845)
Benefits paid		(667)	(482)
Benefit obligation, ending balance	22,078	24,603	20,964
Change in plan assets:
Fair value of plan assets, beginning balance		0	0
Actuarial return on plan assets		0	0
Employer contributions		667	482
Benefits paid		(667)	(482)
Fair value of plan assets, ending balance	$ 0	0	0
Funded status at end of year		$ (24,603)	$ (20,964)

Employee Benefit Plans - Narrat

Employee Benefit Plans - Narrative (Details) - USD ($)	1 Months Ended	3 Months Ended	12 Months Ended
Employee Benefit Plans - Narrative (Details) - USD ($)	Apr. 30, 2018	Dec. 31, 2017	Dec. 31, 2019	Dec. 31, 2018	Sep. 30, 2017
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, years of employment			5 years
Bank-owned life insurance			$ 211,415,000	$ 184,488,000
Bank-owned life insurance income		$ 1,089,000	5,846,000	5,208,000	$ 4,936,000
Defined benefit plan, accumulated benefit obligation			14,100,000	10,500,000
Defined contribution plan, cost		159,000	1,100,000	1,300,000	395,000
Proceeds from repayments of loans by employee stock ownership plans		0	0	45,428,000	0
Employee stock ownership plan, compensation expense		0	3,566,000	2,594,000	0
RIM
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, funded (unfunded) status of plan			(13,696,000)	(11,285,000)
Defined contribution plan, cost		1,000	11,000	9,000	14,000
Employee stock ownership plan, compensation expense		0	267,000	165,000	0
Post-retirement
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, funded (unfunded) status of plan			(24,603,000)	(20,964,000)
Pension
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, funded (unfunded) status of plan			92,521,000	63,769,000
Defined contribution plan, cost		$ 289,000	$ 1,400,000	1,300,000	1,200,000
Maximum
Defined Benefit Plan Disclosure [Line Items]
Defined contribution plan, employer matching contribution, percent of match			4.50%
Maximum \| Pension
Defined Benefit Plan Disclosure [Line Items]
Defined contribution plan, employer matching contribution, percent of match			4.50%
Minimum
Defined Benefit Plan Disclosure [Line Items]
Defined contribution plan, employer matching contribution, percent of match			3.00%
Minimum \| Pension
Defined Benefit Plan Disclosure [Line Items]
Defined contribution plan, employer matching contribution, percent of match			3.00%
Columbia Bank Employee Stock Ownership Plan
Defined Benefit Plan Disclosure [Line Items]
Proceeds from repayments of loans by employee stock ownership plans	$ 45,400,000
Loan term	20 years		20 years
Shares contributed to ESOP (in shares)	4,542,855
Fixed interest rate	4.75%
Employee stock ownership plan, compensation expense			$ 3,600,000	$ 2,600,000	$ 0

Employee Benefit Plans - Sche_2

Employee Benefit Plans - Schedule of Components of Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Sep. 30, 2017
Pension
Defined Benefit Plan Disclosure [Line Items]
Unrecognized prior service costs	$ 0	$ 0	$ 0	$ 0
Unrecognized net actuarial income	68,752	59,579	61,731	55,438
Total accumulated other comprehensive income	68,752	59,579	61,731	55,438
RIM
Defined Benefit Plan Disclosure [Line Items]
Unrecognized prior service costs	0	0	0	0
Unrecognized net actuarial income	5,577	3,748	5,515	4,725
Total accumulated other comprehensive income	5,577	3,748	5,515	4,725
Post-retirement
Defined Benefit Plan Disclosure [Line Items]
Unrecognized prior service costs	0	0	(106)	(140)
Unrecognized net actuarial income	7,221	4,226	6,395	4,611
Total accumulated other comprehensive income	$ 7,221	$ 4,226	$ 6,289	$ 4,471

Employee Benefit Plans - Sche_3

Employee Benefit Plans - Schedule of Net Periodic Benefit Cost (Income) (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2019	Dec. 31, 2018	Sep. 30, 2017
Pension
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service cost	$ 1,780	$ 6,494	$ 7,805	$ 7,621
Interest cost	2,128	8,569	8,489	8,444
Expected return on plan assets	(4,814)	(21,058)	(20,794)	(24,809)
Amortization of Prior service cost	0	0	0	0
Amortization of Net loss	707	3,070	3,117	10,998
Net periodic (income) benefit cost	(199)	(2,925)	(1,383)	2,254
RIM
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service cost	60	210	282	237
Interest cost	111	466	443	429
Expected return on plan assets	0	0	0	0
Amortization of Prior service cost	0	0	0	0
Amortization of Net loss	103	244	413	453
Net periodic (income) benefit cost	274	920	1,138	1,119
Post-retirement
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service cost	92	339	417	471
Interest cost	205	826	796	742
Expected return on plan assets	0	0	0	0
Amortization of Prior service cost	(34)	0	(106)	(136)
Amortization of Net loss	70	147	323	325
Net periodic (income) benefit cost	$ 333	$ 1,312	$ 1,430	$ 1,402

Employee Benefit Plans - Retros

Employee Benefit Plans - Retrospective Application of the Statement of Income (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2019	Dec. 31, 2018	Sep. 30, 2017
Defined Benefit Plan Disclosure [Line Items]
Compensation and employee benefits	$ 15,624	$ 84,256	$ 77,226	$ 62,993
Other non-interest expense	$ 3,780	$ 11,769	5,597	$ 14,207
Accounting Standards Update 2017-07
Defined Benefit Plan Disclosure [Line Items]
Compensation and employee benefits			77,226
Other non-interest expense			5,597
Accounting Standards Update 2017-07 \| Previously Reported
Defined Benefit Plan Disclosure [Line Items]
Compensation and employee benefits			69,907
Other non-interest expense			$ 12,916

Employee Benefit Plans - Sche_4

Employee Benefit Plans - Schedule of Weighted Average Actuarial Assumptions (Details)	3 Months Ended	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2019	Dec. 31, 2018	Sep. 30, 2017
Pension
Defined Benefit Plan Disclosure [Line Items]
Discount rate	3.75%	3.49%	4.57%	4.00%
Rate of compensation increase	3.50%	3.50%	3.50%	3.50%
Discount rate	4.00%	4.57%	3.75%	3.875%
Discount rate-remeasurement		3.85%
Expected rate of return on plan assets	7.25%	7.00%	7.25%	7.50%
Rate of compensation increase	3.50%	3.50%	3.50%	3.50%
RIM
Defined Benefit Plan Disclosure [Line Items]
Discount rate	3.625%	3.33%	4.47%	3.875%
Rate of compensation increase	3.50%	3.50%	3.50%	3.50%
Discount rate	3.875%	4.47%	3.625%	3.625%
Rate of compensation increase	3.50%	3.50%	3.50%	3.50%
Post-retirement
Defined Benefit Plan Disclosure [Line Items]
Discount rate	3.625%	3.27%	4.41%	3.875%
Discount rate	3.875%	4.41%	3.625%	3.625%

Employee Benefit Plans - Sche_5

Employee Benefit Plans - Schedule of Assumed Health Care Cost Trend Rates (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2019USD ($)
Retirement Benefits [Abstract]
Effect on total service cost and interest cost, increase	$ 14
Effect on post-retirement benefit obligations, increase	162
Effect on total service cost and interest cost, decrease	(12)
Effect on post-retirement benefit obligations, decrease	$ (141)

Employee Benefit Plans - Sche_6

Employee Benefit Plans - Schedule of Estimated Future Benefit Payments (Details) $ in Thousands	Dec. 31, 2019USD ($)
Pension
Defined Benefit Plan Disclosure [Line Items]
2020	$ 6,675
2021	7,209
2022	7,760
2023	8,412
2024	9,112
Years 2025-2029	57,274
RIM
Defined Benefit Plan Disclosure [Line Items]
2020	361
2021	379
2022	417
2023	457
2024	521
Years 2025-2029	3,605
Post-retirement
Defined Benefit Plan Disclosure [Line Items]
2020	1,246
2021	1,293
2022	1,337
2023	1,351
2024	1,346
Years 2025-2029	$ 7,270

Employee Benefit Plans - Sche_7

Employee Benefit Plans - Schedule of Weighted Average and Target Allocations of Pension Assets (Details) - Pension	Dec. 31, 2019	Dec. 31, 2018
Defined Benefit Plan Disclosure [Line Items]
Weighted average assets allocations, percentage	100.00%	100.00%
Domestic equities
Defined Benefit Plan Disclosure [Line Items]
Weighted average assets allocations, percentage	39.60%	35.20%
Foreign equities
Defined Benefit Plan Disclosure [Line Items]
Weighted average assets allocations, percentage	9.60%	10.80%
Fixed income
Defined Benefit Plan Disclosure [Line Items]
Weighted average assets allocations, percentage	44.30%	42.30%
Commingled real estate funds
Defined Benefit Plan Disclosure [Line Items]
Weighted average assets allocations, percentage	6.10%	10.50%
Money market mutual funds
Defined Benefit Plan Disclosure [Line Items]
Weighted average assets allocations, percentage	0.40%	1.20%
Minimum \| Equities
Defined Benefit Plan Disclosure [Line Items]
Plan assets, target allocation, percent	40.00%
Minimum \| Fixed income
Defined Benefit Plan Disclosure [Line Items]
Plan assets, target allocation, percent	40.00%
Minimum \| Commingled real estate funds
Defined Benefit Plan Disclosure [Line Items]
Plan assets, target allocation, percent	0.00%
Minimum \| Money market mutual funds
Defined Benefit Plan Disclosure [Line Items]
Plan assets, target allocation, percent	0.00%
Maximum \| Equities
Defined Benefit Plan Disclosure [Line Items]
Plan assets, target allocation, percent	60.00%
Maximum \| Fixed income
Defined Benefit Plan Disclosure [Line Items]
Plan assets, target allocation, percent	60.00%
Maximum \| Commingled real estate funds
Defined Benefit Plan Disclosure [Line Items]
Plan assets, target allocation, percent	10.00%
Maximum \| Money market mutual funds
Defined Benefit Plan Disclosure [Line Items]
Plan assets, target allocation, percent	15.00%

Employee Benefit Plans - Sche_8

Employee Benefit Plans - Schedule of Fair Value of Plan Assets (Details) - Pension - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 356,347	$ 272,974	$ 289,390
Quoted Prices in Active Markets for Identical Assets (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	334,751	244,383
Significant Other Observable Inputs (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	21,596	28,591
Significant Unobservable Inputs (Level 3)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Money market mutual funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	1,462	3,459
Money market mutual funds \| Quoted Prices in Active Markets for Identical Assets (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	1,462	3,459
Money market mutual funds \| Significant Other Observable Inputs (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Money market mutual funds \| Significant Unobservable Inputs (Level 3)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Mutual funds - value stock fund
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	27,827	22,533
Mutual funds - value stock fund \| Quoted Prices in Active Markets for Identical Assets (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	27,827	22,533
Mutual funds - value stock fund \| Significant Other Observable Inputs (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Mutual funds - value stock fund \| Significant Unobservable Inputs (Level 3)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Mutual funds - fixed income
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	158,030	115,500
Mutual funds - fixed income \| Quoted Prices in Active Markets for Identical Assets (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	158,030	115,500
Mutual funds - fixed income \| Significant Other Observable Inputs (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Mutual funds - fixed income \| Significant Unobservable Inputs (Level 3)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Mutual funds - international stock
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	34,332	29,441
Mutual funds - international stock \| Quoted Prices in Active Markets for Identical Assets (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	34,332	29,441
Mutual funds - international stock \| Significant Other Observable Inputs (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Mutual funds - international stock \| Significant Unobservable Inputs (Level 3)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Mutual funds - institutional stock index
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	113,100	73,450
Mutual funds - institutional stock index \| Quoted Prices in Active Markets for Identical Assets (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	113,100	73,450
Mutual funds - institutional stock index \| Significant Other Observable Inputs (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Mutual funds - institutional stock index \| Significant Unobservable Inputs (Level 3)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Commingled real estate funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	21,596	28,591
Commingled real estate funds \| Quoted Prices in Active Markets for Identical Assets (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Commingled real estate funds \| Significant Other Observable Inputs (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	21,596	28,591
Commingled real estate funds \| Significant Unobservable Inputs (Level 3)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 0	$ 0

Employee Benefit Plans - Sche_9

Employee Benefit Plans - Schedule of Employee Stock Ownership Plan (Details) - USD ($) shares in Thousands, $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Retirement Benefits [Abstract]
Allocated shares (in shares)	385	159
Unearned shares (in shares)	4,156	4,384
Total ESOP shares (in shares)	4,541	4,543
Fair value of unearned shares (in shares)	$ 70,409	$ 67,025

Employee Benefit Plans - Stock

Employee Benefit Plans - Stock Based Compensation Narrative (Details) - USD ($)	Dec. 16, 2019	Jul. 23, 2019	Dec. 31, 2017	Dec. 31, 2019	Dec. 31, 2018	Sep. 30, 2017	Jun. 06, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares authorized (in shares)							7,949,996
Grants in period (in shares)	184,378	3,707,901		3,892,279
Grants in period (in dollars per share)	$ 4.59	$ 4.25
Grants in period (in dollars per share)	$ 17	$ 15.60		$ 15.67
Exercises in period (in shares)			0	0	0	0
Restricted Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares authorized (in shares)							2,271,427
Equity instruments other than options, grants in period (in shares)	74,673	1,389,570		1,464,243
Equity instruments other than options, grants in period (in dollars per share)	$ 17	$ 15.60		$ 15.67
Share-based payment expense			$ 0	$ 2,300,000	$ 0	$ 0
Equity instrument other than options, nonvested (in shares)				1,420,012	0
Nonvested award, excluding option, cost not yet recognized				$ 19,900,000
Cost not yet recognized, period for recognition				4 years 1 month 6 days
Stock Option
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares authorized (in shares)							5,678,569
Award vesting period (in years)				5 years
Share-based payment expense			$ 0	$ 1,400,000	$ 0	$ 0
Equity instrument other than options, nonvested (in shares)				3,784,044
Nonvested award, excluding option, cost not yet recognized				$ 14,800,000
Cost not yet recognized, period for recognition				4 years 7 months 6 days
Expiration period (in years)	10 years	10 years
Expected term	6 years 6 months	6 years 6 months
Risk free interest rate	1.79%	1.90%
Expected volatility rate	22.23%	22.12%
Expected dividend rate	0.00%	0.00%
Minimum \| Restricted Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period (in years)		3 years
Maximum \| Restricted Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period (in years)				5 years
Share-based Payment Arrangement, Tranche One \| Restricted Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period (in years)				1 year
Share-based Payment Arrangement, Tranche One \| Stock Option
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period (in years)				1 year

Employee Benefit Plans - Restri

Employee Benefit Plans - Restricted Stock Activity (Details) - Restricted Stock - $ / shares	Dec. 16, 2019	Jul. 23, 2019	Dec. 31, 2019
Number of Restricted Shares
Beginning balance (in shares)			0
Granted (in shares)	74,673	1,389,570	1,464,243
Forfeited (in shares)			(44,231)
Ending balance (in shares)			1,420,012
Weighted Average Grant Date Fair Value
Beginning balance (in dollars per share)			$ 0
Granted (in dollars per share)	$ 17	$ 15.60	15.67
Forfeited (in dollars per share)			15.60
Ending balance (in dollars per share)			$ 15.67

Employee Benefit Plans - Stoc_2

Employee Benefit Plans - Stock Option Activity (Details) - USD ($)	Dec. 16, 2019	Jul. 23, 2019	Dec. 31, 2019
Number of Stock Options
Beginning balance (in shares)			0
Granted (in shares)	184,378	3,707,901	3,892,279
Forfeited (in shares)			(108,235)
Ending balance (in shares)			3,784,044
Options exercisable (in shares)			0
Weighted Average Exercise Price
Beginning balance (in dollars per share)			$ 0
Granted (in dollars per share)	$ 17	$ 15.60	15.67
Forfeited (in dollars per share)			15.60
Ending balance (in dollars per share)			15.67
Options exercisable (in dollars per share)			$ 0
Weighted Average Remaining Contractual Term (in years)
Granted			9 years 7 months 6 days
Outstanding			9 years 7 months 6 days
Aggregate Intrinsic Value
Outstanding			$ 4,812,490

Income Taxes - Narrative (Detai

Income Taxes - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
Income Taxes - Narrative (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2019	Dec. 31, 2018	Sep. 30, 2017
Income Tax Contingency [Line Items]
Income tax expense, Tax Cuts And Jobs Act Of 2017, deferred tax assets and liabilities	$ 11,700
Deferred income tax expense (benefit), related to unrealized gain (losses) on available-for-sale securities	(119)	$ (5,500)	$ 1,400	$ 6,400
Reclassification adjustment of actuarial net (loss) gain included in net income	(94)	779	(530)	(4,200)
Deferred tax expense (benefit)	$ 7,491	7,527	(5,490)	$ (1,426)
Included in retained earnings, no provision for income tax		21,500	21,500
Valuation allowance		7,442	2,388
Operating loss carryforwards		70,900	24,000
Stewardship Financial Corporation
Income Tax Contingency [Line Items]
Deferred tax expense (benefit)		2,300
Operating loss carryforwards		5,800
Operating loss carryforwards, net		2,300
New Jersey Division of Taxation
Income Tax Contingency [Line Items]
Operating loss carryforwards		28,900	28,900
Tax credit carryforward, amount		$ 2,200	$ 2,200

Income Taxes - Schedule of Inco

Income Taxes - Schedule of Income Tax Expense (Benefit) (Details) - USD ($) $ in Thousands	3 Months Ended													12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Dec. 31, 2019	Dec. 31, 2018	Sep. 30, 2017
Current:
Federal									$ 630					$ 5,933	$ 11,284	$ 16,198
State									862					2,905	5,129	1,236
Total current									1,492					8,838	16,413	17,434
Deferred:
Federal									7,530					8,275	(4,901)	(1,454)
State									(39)					(748)	(589)	28
Total deferred									7,491					7,527	(5,490)	(1,426)
Total income tax expense	$ 3,832	$ 5,392	$ 3,634	$ 3,507	$ 3,123	$ 6,956	$ (2,961)	$ 3,805	$ 8,983	$ 194	$ 5,934	$ 5,012	$ 4,868	$ 16,365	$ 10,923	$ 16,008

Income Taxes - Schedule of Effe

Income Taxes - Schedule of Effective Tax Rate Reconciliation (Details) - USD ($) $ in Thousands	3 Months Ended													12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Dec. 31, 2019	Dec. 31, 2018	Sep. 30, 2017
Income Tax Disclosure [Abstract]
Tax expense at applicable statutory rate									$ 4,431					$ 14,927	$ 7,067	$ 16,478
Increase (decrease) in taxes resulting from:
State tax, net of federal income tax benefit									535					1,704	3,587	822
ESOP fair market value adjustment									0					272	202	0
Tax exempt interest income									(2)					(6)	(4)	(50)
Income from Bank-owned life insurance									(381)					(1,246)	(812)	(1,589)
Dividend received deduction									(10)					(8)	(16)	(40)
Non-deductible merger-related expenses									0					222	0	0
Non-deductible compensation expense									0					398	0	0
Impact of tax reform									4,700					0	0	0
Other, net									(290)					102	899	387
Total income tax expense	$ 3,832	$ 5,392	$ 3,634	$ 3,507	$ 3,123	$ 6,956	$ (2,961)	$ 3,805	$ 8,983	$ 194	$ 5,934	$ 5,012	$ 4,868	$ 16,365	$ 10,923	$ 16,008

Income Taxes - Schedule of Defe

Income Taxes - Schedule of Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Deferred tax assets:
Allowance for loan losses	$ 13,114	$ 13,251
Post-retirement benefits	4,089	3,720
Deferred compensation	2,085	2,228
Depreciation	1,002	1,042
Retirement Income Maintenance plan	1,725	1,602
ESOP	301	128
Stock-based compensation	788	35
Reserve for uncollected interest	54	24
Net unrealized losses on debt securities and defined benefit plans	18,374	19,060
Federal and State NOLs	8,333	2,063
Alternative minimum assessment carryforwards	2,156	2,156
Charitable contribution carryforward	5,981	6,085
Purchase accounting	665	0
Other items	332	670
Gross deferred tax assets	58,999	52,064
Valuation allowance	(7,442)	(2,388)
Total deferred tax assets, net	51,557	49,676
Deferred tax liabilities:
Pension expense	33,856	26,071
Deferred loan costs	5,911	5,736
Intangible assets	1,215	1,621
Other items	266	34
Total gross deferred tax liabilities	41,248	33,462
Net deferred tax asset	$ 10,309	$ 16,214

Financial Transactions with O_3

Financial Transactions with Off-Balance-Sheet Risk and Concentrations of Credit Risk - Schedule of Loan Commitments (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Concentration Risk [Line Items]
Loan commitments	$ 270,881	$ 195,229
Residential real estate
Concentration Risk [Line Items]
Loan commitments	91,141	29,622
Multifamily and commercial
Concentration Risk [Line Items]
Loan commitments	95,025	73,201
Commercial business loans
Concentration Risk [Line Items]
Loan commitments	18,737	13,000
Construction
Concentration Risk [Line Items]
Loan commitments	59,990	71,062
Home equity loans and advances
Concentration Risk [Line Items]
Loan commitments	$ 5,988	$ 8,344

Financial Transactions with O_4

Financial Transactions with Off-Balance-Sheet Risk and Concentrations of Credit Risk - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2019	Dec. 31, 2018	Sep. 30, 2017
Loss Contingencies [Line Items]
Derivative (liabilities), at fair value, net		$ (11,400)	$ (2,600)
Occupancy expense, net	$ 3,382	16,180	14,547	$ 13,315
Unused lines of Credit
Loss Contingencies [Line Items]
Fair value disclosure, off-balance sheet risk, amount, liability		910,000	714,600
Mortgages
Loss Contingencies [Line Items]
Fair value disclosure, off-balance sheet risk, amount, liability			8,100
Letter of Credit
Loss Contingencies [Line Items]
Fair value disclosure, off-balance sheet risk, amount, liability		8,400	7,000
Bank Facilities
Loss Contingencies [Line Items]
Occupancy expense, net	$ 1,100	$ 5,000	$ 4,600	$ 4,300

Financial Transactions with O_5

Financial Transactions with Off-Balance-Sheet Risk and Concentrations of Credit Risk - Schedule of Future Minimum Lease Payments (Details) $ in Thousands	Dec. 31, 2019USD ($)
Commitments and Contingencies Disclosure [Abstract]
2020	$ 4,942
2021	4,484
2022	4,012
2023	3,503
2024	2,732
Thereafter	5,001
Total lease commitments	$ 24,674

Fair Value Measurements - Asset

Fair Value Measurements - Assets and Liabilities Measured on Recurring Basis (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities available for sale	$ 1,098,336	$ 1,032,868
Equity securities, at fair value	2,855	1,890
U.S. government and agency obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities available for sale	42,386	54,157
Mortgage-backed securities and collateralized mortgage obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities available for sale	979,881	920,007
Municipal obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities available for sale	2,284	987
Corporate debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities available for sale	69,180	53,467
Trust preferred securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities available for sale	4,605	4,250
Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities available for sale		54,157
Equity securities, at fair value	2,587	1,890
Derivative assets	0	0
Derivative liabilities	0	0
Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities available for sale		978,711
Equity securities, at fair value	268	0
Derivative assets	185	1,342
Derivative liabilities	11,546	3,944
Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities available for sale	0	0
Equity securities, at fair value		0
Derivative assets	0	0
Derivative liabilities	0	0
Measured on recurring basis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities available for sale	1,098,336	1,032,868
Equity securities, at fair value	2,855	1,890
Derivative assets	185	1,342
Assets	1,101,376	1,036,100
Derivative liabilities	11,546	3,944
Measured on recurring basis \| U.S. government and agency obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities available for sale	42,386	54,157
Measured on recurring basis \| Mortgage-backed securities and collateralized mortgage obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities available for sale	979,881	920,007
Measured on recurring basis \| Municipal obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities available for sale	2,284	987
Measured on recurring basis \| Corporate debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities available for sale	69,180	53,467
Measured on recurring basis \| Trust preferred securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities available for sale	4,605	4,250
Measured on recurring basis \| Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities available for sale	42,386	54,157
Equity securities, at fair value	2,587	1,890
Derivative assets	0	0
Assets	44,973	56,047
Derivative liabilities	0	0
Measured on recurring basis \| Quoted Prices in Active Markets for Identical Assets (Level 1) \| U.S. government and agency obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities available for sale	42,386	54,157
Measured on recurring basis \| Quoted Prices in Active Markets for Identical Assets (Level 1) \| Mortgage-backed securities and collateralized mortgage obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities available for sale	0	0
Measured on recurring basis \| Quoted Prices in Active Markets for Identical Assets (Level 1) \| Municipal obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities available for sale	0	0
Measured on recurring basis \| Quoted Prices in Active Markets for Identical Assets (Level 1) \| Corporate debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities available for sale	0	0
Measured on recurring basis \| Quoted Prices in Active Markets for Identical Assets (Level 1) \| Trust preferred securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities available for sale	0	0
Measured on recurring basis \| Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities available for sale	1,055,950	978,711
Equity securities, at fair value	268	0
Derivative assets	185	1,342
Assets	1,056,403	980,053
Derivative liabilities	11,546	3,944
Measured on recurring basis \| Significant Other Observable Inputs (Level 2) \| U.S. government and agency obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities available for sale	0	0
Measured on recurring basis \| Significant Other Observable Inputs (Level 2) \| Mortgage-backed securities and collateralized mortgage obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities available for sale	979,881	920,007
Measured on recurring basis \| Significant Other Observable Inputs (Level 2) \| Municipal obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities available for sale	2,284	987
Measured on recurring basis \| Significant Other Observable Inputs (Level 2) \| Corporate debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities available for sale	69,180	53,467
Measured on recurring basis \| Significant Other Observable Inputs (Level 2) \| Trust preferred securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities available for sale	4,605	4,250
Measured on recurring basis \| Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities available for sale	0	0
Equity securities, at fair value	0	0
Derivative assets	0	0
Assets	0	0
Derivative liabilities	0	0
Measured on recurring basis \| Significant Unobservable Inputs (Level 3) \| U.S. government and agency obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities available for sale	0	0
Measured on recurring basis \| Significant Unobservable Inputs (Level 3) \| Mortgage-backed securities and collateralized mortgage obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities available for sale	0	0
Measured on recurring basis \| Significant Unobservable Inputs (Level 3) \| Municipal obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities available for sale	0	0
Measured on recurring basis \| Significant Unobservable Inputs (Level 3) \| Corporate debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities available for sale	0	0
Measured on recurring basis \| Significant Unobservable Inputs (Level 3) \| Trust preferred securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities available for sale	$ 0	$ 0

Fair Value Measurements - Narra

Fair Value Measurements - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Sep. 30, 2017
Minimum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Adjustments for estimated costs to sell collateral dependent impaired loans	6.00%
Estimated costs to sell foreclosed assets	6.00%
Maximum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Adjustments for estimated costs to sell collateral dependent impaired loans	8.00%
Estimated costs to sell foreclosed assets	8.00%
U.S. government and agency obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Transfers from Level 2 to Level 1, amount		$ 20.4

Fair Value Measurements - Ass_2

Fair Value Measurements - Assets and Liabilities Measured on Non-Recurring Basis (Details) - USD ($)	Dec. 31, 2019	Dec. 31, 2018
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans held-for-sale, at fair value	$ 0	$ 8,081,000
Real estate owned	0	92,000
Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans held-for-sale, at fair value	0	0
Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans held-for-sale, at fair value	0	0
Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans held-for-sale, at fair value	6,219,008,000	4,841,830,000
Measured on non-recurring basis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans held-for-sale, at fair value	1,063,000	125,000
Real estate owned		92,000
Mortgage servicing rights	681,000	442,000
Assets	1,744,000	659,000
Measured on non-recurring basis \| Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans held-for-sale, at fair value	0	0
Real estate owned		0
Mortgage servicing rights	0	0
Assets	0	0
Measured on non-recurring basis \| Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans held-for-sale, at fair value	0	0
Real estate owned		0
Mortgage servicing rights	0	0
Assets	0	0
Measured on non-recurring basis \| Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans held-for-sale, at fair value	1,063,000	125,000
Real estate owned		92,000
Mortgage servicing rights	681,000	442,000
Assets	$ 1,744,000	$ 659,000

Fair Value Measurements - Quali

Fair Value Measurements - Qualitative Valuation (Details)	Dec. 31, 2019USD ($)	Dec. 31, 2018USD ($)
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Loans held-for-sale, at fair value	$ 0	$ 8,081,000
Real estate owned	0	92,000
Measured on non-recurring basis
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Loans held-for-sale, at fair value	1,063,000	125,000
Real estate owned		92,000
Mortgage servicing rights	681,000	442,000
Significant Unobservable Inputs (Level 3)
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Loans held-for-sale, at fair value	6,219,008,000	4,841,830,000
Significant Unobservable Inputs (Level 3) \| Measured on non-recurring basis
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Loans held-for-sale, at fair value	1,063,000	125,000
Real estate owned		92,000
Mortgage servicing rights	$ 681,000	$ 442,000
Significant Unobservable Inputs (Level 3) \| Measurement Input, Expected Value Of Future Cash Flows \| Measured on non-recurring basis \| Impaired loans \| Estimated Cash Flow
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Discount rate	0
Significant Unobservable Inputs (Level 3) \| Measurement Input, Expected Value Of Future Cash Flows \| Measured on non-recurring basis \| Impaired loans \| Weighted Average \| Estimated Cash Flow
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Discount rate	0
Significant Unobservable Inputs (Level 3) \| Measurement Input, Prepayment Rate and Discount Rate \| Measured on non-recurring basis \| Mortgage servicing rights \| Weighted Average \| Estimated Cash Flow
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Discount rate	0.127
Significant Unobservable Inputs (Level 3) \| Measurement Input, Discount Rate \| Measured on non-recurring basis \| Impaired loans \| Appraisal
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Discount rate		0.060
Significant Unobservable Inputs (Level 3) \| Measurement Input, Discount Rate \| Measured on non-recurring basis \| Impaired loans \| Weighted Average \| Appraisal
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Discount rate		0.060
Significant Unobservable Inputs (Level 3) \| Measurement Input, Discount Rate \| Measured on non-recurring basis \| Real estate owned \| Contract Sales Price
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Discount rate		0.060
Significant Unobservable Inputs (Level 3) \| Measurement Input, Discount Rate \| Measured on non-recurring basis \| Real estate owned \| Weighted Average \| Contract Sales Price
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Discount rate		0.060
Significant Unobservable Inputs (Level 3) \| Measurement Input, Prepayment Rate \| Measured on non-recurring basis \| Mortgage servicing rights \| Weighted Average \| Estimated Cash Flow
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Discount rate		0.120
Significant Unobservable Inputs (Level 3) \| Measurement Input, Prepayment Rate \| Measured on non-recurring basis \| Mortgage servicing rights \| Minimum \| Estimated Cash Flow
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Discount rate	0.036	0.033
Significant Unobservable Inputs (Level 3) \| Measurement Input, Prepayment Rate \| Measured on non-recurring basis \| Mortgage servicing rights \| Maximum \| Estimated Cash Flow
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Discount rate	0.240	0.268
Significant Unobservable Inputs (Level 3) \| Measurement Input, Prepayment Rate \| Measured on non-recurring basis \| SBA servicing rights \| Weighted Average \| Estimated Cash Flow
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Discount rate		0.1175

Fair Value Measurements - Fair

Fair Value Measurements - Fair Value on Balance Sheet (Details) - USD ($)	Dec. 31, 2019	Dec. 31, 2018
Financial assets:
Debt securities available for sale	$ 1,098,336,000	$ 1,032,868,000
Debt securities held to maturity	289,505,000	254,841,000
Equity securities, at fair value	2,855,000	1,890,000
Loans held-for-sale	0	8,100,000
Loans receivable, net	0	8,081,000
Quoted Prices in Active Markets for Identical Assets (Level 1)
Financial assets:
Cash and cash equivalents	75,547,000	42,201,000
Debt securities available for sale		54,157,000
Debt securities held to maturity	19,960,000	23,241,000
Equity securities, at fair value	2,587,000	1,890,000
Federal Home Loan Bank stock	0	0
Loans held-for-sale
Loans receivable, net	0	0
Derivative assets	0	0
Financial liabilities:
Deposits	0	0
Borrowings	0	0
Derivative liabilities	0	0
Significant Other Observable Inputs (Level 2)
Financial assets:
Cash and cash equivalents	0	0
Debt securities available for sale		978,711,000
Debt securities held to maturity	269,545,000	231,600,000
Equity securities, at fair value	268,000	0
Federal Home Loan Bank stock	69,579,000	58,938,000
Loans held-for-sale		8,081,000
Loans receivable, net	0	0
Derivative assets	185,000	1,342,000
Financial liabilities:
Deposits	5,654,075,000	4,402,336,000
Borrowings	1,411,962,000	1,185,007,000
Derivative liabilities	11,546,000	3,944,000
Significant Unobservable Inputs (Level 3)
Financial assets:
Cash and cash equivalents	0	0
Debt securities available for sale	0	0
Debt securities held to maturity	0	0
Equity securities, at fair value		0
Federal Home Loan Bank stock	0	0
Loans held-for-sale		0
Loans receivable, net	6,219,008,000	4,841,830,000
Derivative assets	0	0
Financial liabilities:
Deposits	0	0
Borrowings	0	0
Derivative liabilities	0	0
Carrying Value
Financial assets:
Cash and cash equivalents	75,547,000	42,201,000
Debt securities available for sale	1,098,336,000	1,032,868,000
Debt securities held to maturity	285,756,000	262,143,000
Equity securities, at fair value	2,855,000	1,890,000
Federal Home Loan Bank stock	69,579,000	58,938,000
Loans held-for-sale		8,081,000
Loans receivable, net	6,135,857,000	4,916,840,000
Derivative assets	185,000	1,342,000
Financial liabilities:
Deposits	5,645,842,000	4,413,873,000
Borrowings	1,407,022,000	1,189,180,000
Derivative liabilities	11,546,000	3,944,000
Total Fair Value
Financial assets:
Cash and cash equivalents	75,547,000	42,201,000
Debt securities available for sale	1,098,336,000	1,032,868,000
Debt securities held to maturity	289,505,000	254,841,000
Equity securities, at fair value	2,855,000	1,890,000
Federal Home Loan Bank stock	69,579,000	58,938,000
Loans held-for-sale		8,081,000
Loans receivable, net	6,219,008,000	4,841,830,000
Derivative assets	185,000	1,342,000
Financial liabilities:
Deposits	5,654,075,000	4,402,336,000
Borrowings	1,411,962,000	1,185,007,000
Derivative liabilities	$ 11,546,000	$ 3,944,000

Selected Quarterly Financial _3

Selected Quarterly Financial Data (Unaudited) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended													12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Dec. 31, 2019	Dec. 31, 2018	Sep. 30, 2017
Quarterly Financial Information Disclosure [Abstract]
Total interest income	$ 71,026	$ 64,438	$ 62,732	$ 62,887	$ 61,785	$ 57,695	$ 55,019	$ 51,791	$ 49,169	$ 47,820	$ 46,850	$ 45,428	$ 44,129	$ 261,083	$ 226,290	$ 184,226
Total interest expense	23,598	22,722	21,889	20,503	18,410	17,112	14,004	12,730	12,240	11,860	11,211	10,651	10,724	88,712	62,256	44,446
Net interest income	47,428	41,716	40,843	42,384	43,375	40,583	41,015	39,061	36,929	35,960	35,639	34,777	33,405	172,371	164,034	139,780
Provision for loan losses	2,519	1,157	112	436	777	1,500	2,400	2,000	3,400	5,676	375	375	0	4,224	6,677	6,426
Net interest income after provision for loan losses	44,909	40,559	40,731	41,948	42,598	39,083	38,615	37,061	33,529	30,284	35,264	34,402	33,405	168,147	157,357	133,354
Total non-interest income	8,709	10,115	6,775	6,037	6,405	5,290	5,450	4,543	4,733	1,630	4,645	5,806	5,534	31,636	21,688	17,172
Total non-interest expense	36,237	31,064	31,841	29,559	31,013	26,590	61,768	26,015	25,601	30,206	24,703	24,903	24,078	128,701	145,386	103,446
Income before income tax expense	17,381	19,610	15,665	18,426	17,990	17,783	(17,703)	15,589	12,661	1,708	15,206	15,305	14,861	71,082	33,659	47,080
Income tax expense	3,832	5,392	3,634	3,507	3,123	6,956	(2,961)	3,805	8,983	194	5,934	5,012	4,868	16,365	10,923	16,008
Net income	$ 13,549	$ 14,218	$ 12,031	$ 14,919	$ 14,867	$ 10,827	$ (14,742)	$ 11,784	$ 3,678	$ 1,514	$ 9,272	$ 10,293	$ 9,993	$ 54,717	$ 22,736	$ 31,072
Earnings per share - basic and diluted (in dollars per share)	$ 0.12	$ 0.13	$ 0.11	$ 0.13	$ 0.13	$ 0.10	$ (0.13)							$ 0.49	$ 0.20
Weighted average shares outstanding - basic and diluted (in shares)	109,958,999	111,371,754	111,553,203	111,536,577	111,423,361	111,389,951	111,360,278							111,101,246	111,395,723

Earnings per Share (Details)

Earnings per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended													12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Dec. 31, 2019	Dec. 31, 2018	Sep. 30, 2017
Earnings Per Share [Abstract]
Net income	$ 13,549	$ 14,218	$ 12,031	$ 14,919	$ 14,867	$ 10,827	$ (14,742)	$ 11,784	$ 3,678	$ 1,514	$ 9,272	$ 10,293	$ 9,993	$ 54,717	$ 22,736	$ 31,072
Shares:
Weighted average shares outstanding - basic (in shares)														111,101,246	111,395,723
Weighted average dilutive shares outstanding (in shares)														0	0
Weighted average shares outstanding - diluted (in shares)														111,101,246	111,395,723
Earnings per share:
Basic (in dollars per share)														$ 0.49	$ 0.20
Diluted (in dollars per share)														$ 0.49	$ 0.20

Earnings per Share - Narrative

Earnings per Share - Narrative (Details) - shares	3 Months Ended	12 Months Ended
Earnings per Share - Narrative (Details) - shares	Dec. 31, 2017	Dec. 31, 2019	Dec. 31, 2018	Sep. 30, 2017
Earnings Per Share [Abstract]
Antidilutive securities excluded from computation of earnings per share (in shares)	0	1,111,650	0	0

Parent-only Financial Informa_3

Parent-only Financial Information - Statement of Financial Condition (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Sep. 30, 2016
Assets
Cash and due from banks	$ 75,420	$ 42,065
Short-term investments	127	136
Total cash and cash equivalents	75,547	42,201
Debt securities available for sale	1,098,336	1,032,868
Equity securities, at fair value	2,855	1,890
Loans receivable, net	0	8,081
Other assets	145,708	107,048
Total assets	8,188,694	6,691,618
Liabilities:
Borrowings	1,407,022	1,189,180
Accrued expenses and other liabilities	117,806	84,475
Total liabilities	7,206,177	5,719,558
Total stockholders' equity	982,517	972,060	$ 472,070	$ 475,914	$ 439,664
Total liabilities and stockholders' equity	8,188,694	6,691,618
Parent Company
Assets
Cash and due from banks	168,242	153,697
Short-term investments	127	136
Total cash and cash equivalents	168,369	153,833
Debt securities available for sale	1,496	0
Equity securities, at fair value	1,282	1,420
Investment in subsidiaries	785,964	764,663
Loans receivable, net	42,982	44,439
Other assets	8,431	7,852
Total assets	1,008,524	972,207
Liabilities:
Borrowings	23,831	0
Accrued expenses and other liabilities	2,176	147
Total liabilities	26,007	147
Total stockholders' equity	982,517	972,060
Total liabilities and stockholders' equity	$ 1,008,524	$ 972,207

Parent-only Financial Informa_4

Parent-only Financial Information - Statement of Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	3 Months Ended													12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Dec. 31, 2019	Dec. 31, 2018	Sep. 30, 2017
Income:
Loans receivable									$ 43,043					$ 217,774	$ 189,869	$ 164,849
Unrealized gain (loss) on debt securities available for sale									(3,131)					21,067	(5,778)	(11,498)
Interest expense on borrowings									4,609					27,161	22,733	18,865
Net interest income	$ 47,428	$ 41,716	$ 40,843	$ 42,384	$ 43,375	$ 40,583	$ 41,015	$ 39,061	36,929	$ 35,960	$ 35,639	$ 34,777	$ 33,405	172,371	164,034	139,780
Non-interest income:
Gain (loss) on securities transactions									(60)					2,612	116	(1,689)
Change in fair value of equity securities									0					305	0	0
Other non-interest income									1,162					5,922	4,943	4,497
Total non-interest income	8,709	10,115	6,775	6,037	6,405	5,290	5,450	4,543	4,733	1,630	4,645	5,806	5,534	31,636	21,688	17,172
Non-interest expense
Charitable contribution to foundation									0					0	34,767	3,603
Merger-related expenses									0					2,755	0	0
Other non-interest expense									3,780					11,769	5,597	14,207
Total non-interest expense	36,237	31,064	31,841	29,559	31,013	26,590	61,768	26,015	25,601	30,206	24,703	24,903	24,078	128,701	145,386	103,446
Income before income tax expense	17,381	19,610	15,665	18,426	17,990	17,783	(17,703)	15,589	12,661	1,708	15,206	15,305	14,861	71,082	33,659	47,080
Income tax benefit	(3,832)	(5,392)	(3,634)	(3,507)	(3,123)	(6,956)	2,961	(3,805)	(8,983)	(194)	(5,934)	(5,012)	(4,868)	(16,365)	(10,923)	(16,008)
Net income	$ 13,549	$ 14,218	$ 12,031	$ 14,919	14,867	$ 10,827	$ (14,742)	$ 11,784	3,678	$ 1,514	$ 9,272	$ 10,293	$ 9,993	54,717	22,736	31,072
Other comprehensive income									(19,230)					3,710	(6,487)	5,178
Total comprehensive income (loss), net of tax									(15,552)					58,427	16,249	36,250
Parent Company
Income:
Dividends from subsidiary									0					179,000	0	2,000
Loans receivable									0					2,111	1,513	0
Unrealized gain (loss) on debt securities available for sale									41					51	123	162
Interest-earning deposits									0					173	871	1
Total interest income									41					181,335	2,507	2,163
Interest expense on borrowings									1,044					176	3,468	4,177
Net interest income									(1,003)					181,159	(961)	(2,014)
Equity earnings (loss) in subsidiary									4,288					(123,142)	51,401	32,230
Non-interest income:
Gain (loss) on securities transactions									(60)					236	0	0
Change in fair value of equity securities									0					65	0	0
Other non-interest income									0					139	0	0
Total non-interest income									(60)					440	0	0
Non-interest expense
Charitable contribution to foundation									0					0	34,767	0
Merger-related expenses					$ 0				0					1,807		0
Other non-interest expense									2					1,955	425	460
Total non-interest expense									2					3,762	35,192	460
Income before income tax expense									3,223					54,695	15,248	29,756
Income tax benefit									455					22	7,488	1,316
Net income									3,678					54,717	22,736	31,072
Other comprehensive income									(19,230)					3,710	(6,487)	5,178
Total comprehensive income (loss), net of tax									$ (15,552)					$ 58,427	$ 16,249	$ 36,250

Parent-only Financial Informa_5

Parent-only Financial Information - Statement of Cash Flows (Details) - USD ($)	3 Months Ended													12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Sep. 30, 2017
Cash flows from operating activities:
Net income	$ 13,549,000	$ 14,218,000	$ 12,031,000	$ 14,919,000	$ 14,867,000	$ 10,827,000	$ (14,742,000)	$ 11,784,000	$ 3,678,000	$ 1,514,000	$ 9,272,000	$ 10,293,000	$ 9,993,000	$ 54,717,000	$ 22,736,000		$ 31,072,000
Adjustments to reconcile net income to net cash provided by operating activities:
Amortization of debt issuance costs									14,000					0	890,000		53,000
Amortization of intangible assets									0					222,000	0		0
(Gain) loss on securities transactions									60,000					(2,612,000)	(116,000)		1,689,000
Change in fair value of equity securities									0					(305,000)	0		0
Deferred tax expense (benefit)									7,491,000					7,527,000	(5,490,000)		(1,426,000)
Increase in other assets									(15,557,000)					(51,856,000)	(11,053,000)		(11,681,000)
Increase in accrued expenses and other liabilities									3,905,000					3,032,000	7,980,000		9,840,000
Contribution of common stock to Columbia Bank Foundation									0					0	34,767,000		0
Net cash provided by operating activities									2,326,000					123,770,000	60,209,000		36,041,000
Cash flows from investing activities:
Proceeds from sales of debt securities available for sale									0					65,198,000	11,513,000	$ 0	187,376,000
Proceeds from sale of equity securities									92,000					1,065,000	0		0
Proceeds from paydowns / maturities / calls of debt securities available for sale									7,009,000					149,683,000	69,977,000		68,409,000
Purchases of debt securities available for sale									(163,721,000)					(176,171,000)	(413,804,000)		(162,788,000)
Purchase of equity securities									0					(416,000)	0		0
Loan to ESOP									0					0	(45,428,000)		0
Repayment of loan receivable from Bank									0					11,671,000	32,039,000		62,407,000
Net cash acquired in acquisition									0					(31,288,000)	0
Net cash used in investing activities									(372,135,000)					(622,960,000)	(946,764,000)		(330,317,000)
Cash flows from financing activities:
Purchase of treasury stock									0					(55,309,000)	0		0
Restricted stock forfeitures									0					(736,000)	0
Issuance of treasury stock allocated to restricted stock award grants									0					1,095,000	0
Net cash provided by financing activities									334,332,000					532,536,000	863,258,000		349,557,000
Net increase (decrease) in cash and cash equivalents									(35,477,000)					33,346,000	(23,297,000)		55,281,000
Cash and cash equivalents at beginning of period				42,201,000				65,498,000	100,975,000				45,694,000	42,201,000	65,498,000		45,694,000
Cash and cash equivalents at end of period	75,547,000				42,201,000				65,498,000	100,975,000				75,547,000	42,201,000	65,498,000	100,975,000
Non-cash assets acquired:
Debt securities available for sale									0					51,710,000	0		0
Equity securities									0					1,073,000	0		0
Other assets									0					767,000	0		0
Total non-cash assets acquired									0					856,640,000	0		0
Liabilities assumed:
Borrowings									0					82,761,000	0		0
Total liabilities assumed									0					880,399,000	0		0
Net non-cash liabilities acquired									0					(23,759,000)	0		0
Net cash acquired in acquisition									0					105,006,000	0		0
Parent Company
Cash flows from operating activities:
Net income									3,678,000					54,717,000	22,736,000		31,072,000
Adjustments to reconcile net income to net cash provided by operating activities:
Amortization of debt issuance costs									14,000					0	890,000		53,000
Amortization of intangible assets									0					(71,000)	0		0
(Gain) loss on securities transactions									60,000					(236,000)	0		0
Change in fair value of equity securities									0					(65,000)	0		0
Deferred tax expense (benefit)									42,000					1,453,000	(6,086,000)		1,000
Increase in other assets									(494,000)					(2,026,000)	1,515,000		1,404,000
Increase in accrued expenses and other liabilities									989,000					3,515,000	(1,498,000)		62,000
Contribution of common stock to Columbia Bank Foundation									0					0	34,767,000		0
Equity in undistributed earnings (loss) of subsidiary									(4,288,000)					123,142,000	(51,401,000)		(32,295,000)
Net cash provided by operating activities									1,000					180,429,000	923,000		297,000
Cash flows from investing activities:
Capital contribution to subsidiary									0					0	(246,420,000)		0
Proceeds from sales of debt securities available for sale									92,000					0	0		0
Proceeds from sale of equity securities									0					1,065,000	0		0
Proceeds from paydowns / maturities / calls of debt securities available for sale									10,000					500,000	1,601,000		0
Purchases of debt securities available for sale									0					0	(414,000)		0
Purchase of equity securities									0					(416,000)	0		0
Loan to ESOP									0					0	(45,428,000)		0
Repayment of loan receivable from Bank									0					1,457,000	989,000		0
Net cash acquired in acquisition									0					(135,410,000)	0		0
Net cash used in investing activities									102,000					(132,804,000)	(289,672,000)		0
Cash flows from financing activities:
Payments on trust preferred securities									0					0	(51,547,000)		0
Issuance of common stock in initial public offering									0					0	492,428,000		0
Purchase of treasury stock									0					(55,309,000)	0		0
Issuance of common stock allocated to restricted stock award grants									0					21,687,000	0		0
Restricted stock forfeitures									0					(736,000)	0		0
Issuance of treasury stock allocated to restricted stock award grants									0					1,269,000	0		0
Net cash provided by financing activities									0					(33,089,000)	440,881,000		0
Net increase (decrease) in cash and cash equivalents									103,000					14,536,000	152,132,000		297,000
Cash and cash equivalents at beginning of period				$ 153,833,000				$ 1,701,000	1,598,000				$ 1,301,000	153,833,000	1,701,000		1,301,000
Cash and cash equivalents at end of period	$ 168,369,000				$ 153,833,000				1,701,000	$ 1,598,000				168,369,000	153,833,000	$ 1,701,000	1,598,000
Non-cash assets acquired:
Debt securities available for sale									0					1,998,000	0		0
Equity securities									0					208,000	0		0
Other assets									0					1,492,000	0		0
Total non-cash assets acquired									0					3,698,000	0		0
Liabilities assumed:
Borrowings									0					23,901,000	0		0
Total liabilities assumed									0					23,901,000	0		0
Net non-cash liabilities acquired									0					(20,203,000)	0		0
Net cash acquired in acquisition									$ 0					$ 884,000	$ 0		$ 0

Other Comprehensive Income (L_3

Other Comprehensive Income (Loss) - Tax effects of components in other comprehensive income (loss) (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2019	Dec. 31, 2018	Sep. 30, 2017	Jan. 01, 2019	Oct. 01, 2017
Before Tax
Other comprehensive income (loss)	$ (11,819)	$ 4,690	$ (7,378)	$ 8,051
Tax Effect
Other comprehensive income (loss)	(7,411)	(980)	891	(2,873)
After Tax
Other comprehensive income (loss)	(19,230)	3,710	(6,487)	5,178
Unrealized (Losses) Gains on Debt Securities Available for Sale
Before Tax
Other comprehensive income (loss), before reclassifications	(3,012)	26,601	(7,224)	(17,877)
Other comprehensive income (loss)	(2,954)	29,224	(7,353)	(15,239)
Tax Effect
Other comprehensive income (loss), before reclassifications	(119)	(5,534)	1,446	6,379
Reclassification of tax effect resulting from adoption					$ (548)	$ (1,314)
Other comprehensive income (loss)	(188)	(6,137)	1,470	5,438
After Tax
Other comprehensive income (loss), before reclassifications	(3,131)	21,067	(5,778)	(11,498)
Other comprehensive income (loss)	(3,142)	23,087	(5,883)	(9,801)
AOCI, Accumulated Gain (Loss), Debt Securities, Available-for-sale, Accretion Of Unrealized Gains (Losses), Parent
Before Tax
Reclassification from accumulated other comprehensive income, current period	(2)	11	(13)	12
Tax Effect
Reclassification from AOCI, current period	(56)	(2)	0	(4)
After Tax
Reclassification from AOCI, current period	(58)	9	(13)	8
AOCI, Accumulated Gain (Loss), Debt Securities, Available-for-sale, Other Reclassifications, Parent
Before Tax
Reclassification from accumulated other comprehensive income, current period	60	2,612	(116)	2,626
Tax Effect
Reclassification from AOCI, current period	(13)	(601)	24	(937)
After Tax
Reclassification from AOCI, current period	47	2,011	(92)	1,689
Accumulated Gain (Loss), Net, Cash Flow Hedge, Parent
Before Tax
Other comprehensive income (loss), before reclassifications		(8,193)
Tax Effect
Other comprehensive income (loss), before reclassifications		1,725
After Tax
Other comprehensive income (loss), before reclassifications		(6,468)
Unrealized (Losses) on Swaps
Before Tax
Other comprehensive income (loss), before reclassifications	192		(2,825)	95
Tax Effect
Other comprehensive income (loss), before reclassifications	(30)		595	(33)
Reclassification of tax effect resulting from adoption						40
After Tax
Other comprehensive income (loss), before reclassifications	162		(2,230)	62
Accumulated Defined Benefit Plans Adjustment, Net Prior Service Attributable to Parent
Before Tax
Reclassification from accumulated other comprehensive income, current period	(24)	(56)	(623)	(114)
Tax Effect
Reclassification from AOCI, current period	(19)	12	132	41
After Tax
Reclassification from AOCI, current period	(43)	(44)	(491)	(73)
Accumulated Defined Benefit Plans Adjustment, Net Gain (Loss) Attributable to Parent
Before Tax
Reclassification from accumulated other comprehensive income, current period	(9)	(3,709)	2,526	11,806
Tax Effect
Reclassification from AOCI, current period	(94)	779	(530)	(4,213)
After Tax
Reclassification from AOCI, current period	(103)	(2,930)	1,996	7,593
Accumulated Defined Benefit Plans Adjustment Attributable to Parent
Before Tax
Other comprehensive income (loss), before reclassifications	(9,024)	(12,576)	897	11,503
Other comprehensive income (loss)	(9,057)	(16,341)	2,800	23,195
Tax Effect
Other comprehensive income (loss), before reclassifications	3,354	2,641	(776)	(4,106)
Reclassification of tax effect resulting from adoption						$ (10,434)
Other comprehensive income (loss)	(7,193)	3,432	(1,174)	(8,278)
After Tax
Other comprehensive income (loss), before reclassifications	(5,670)	(9,935)	121	7,397
Other comprehensive income (loss)	$ (16,250)	$ (12,909)	$ 1,626	$ 14,917

Other Comprehensive Income (L_4

Other Comprehensive Income (Loss) - Changes in components of other comprehensive income (loss) (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2019	Dec. 31, 2018	Sep. 30, 2017	Jan. 01, 2019	Jan. 01, 2018	Oct. 01, 2017
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at beginning of period	$ 475,914	$ 972,060	$ 472,070	$ 439,664
Adjusted balance					$ 972,060
Current period changes in other comprehensive income (loss)	(19,230)	3,710	(6,487)	5,178
Current period changes in other comprehensive (loss) income	(7,522)
Balance at end of year	472,070	982,517	972,060	475,914
Accumulated Other Comprehensive (Loss)
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at beginning of period	(46,180)	(71,897)	(65,410)	(51,358)
Reclassification of tax effect resulting from adoption					(548)		$ (11,708)
Adjusted balance					(72,445)	$ (65,410)
Current period changes in other comprehensive income (loss)		3,710	(6,487)	5,178
Current period changes in other comprehensive (loss) income	(7,522)
Balance at end of year	(65,410)	(68,735)	(71,897)	(46,180)
Unrealized (Losses) Gains on Debt Securities Available for Sale
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at beginning of period	(4,137)	(13,162)	(7,279)	5,664
Reclassification of tax effect resulting from adoption					(548)		(1,314)
Adjusted balance					(13,710)	(7,279)
Current period changes in other comprehensive income (loss)		23,087	(5,883)	(9,801)
Current period changes in other comprehensive (loss) income	(1,828)
Balance at end of year	(7,279)	9,377	(13,162)	(4,137)
Unrealized (Losses) on Swaps
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at beginning of period	62	(2,006)	224	0
Reclassification of tax effect resulting from adoption							40
Adjusted balance					(2,006)	224
Current period changes in other comprehensive income (loss)		(6,468)	(2,230)	62
Current period changes in other comprehensive (loss) income	122
Balance at end of year	224	(8,474)	(2,006)	62
Employee Benefit Plans
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at beginning of period	(42,105)	(56,729)	(58,355)	(57,022)
Reclassification of tax effect resulting from adoption							$ (10,434)
Adjusted balance					$ (56,729)	$ (58,355)
Current period changes in other comprehensive income (loss)		(12,909)	1,626	14,917
Current period changes in other comprehensive (loss) income	(5,816)
Balance at end of year	$ (58,355)	$ (69,638)	$ (56,729)	$ (42,105)

Other Comprehensive Income (L_5

Other Comprehensive Income (Loss) - Reclassification out of AOCI (Details) - USD ($) $ in Thousands	3 Months Ended													12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Dec. 31, 2019	Dec. 31, 2018	Sep. 30, 2017
Accumulated Other Comprehensive Income (Loss) [Line Items]
Gain (loss) on securities transactions									$ (60)					$ 2,612	$ 116	$ (1,689)
Other non-interest expense									3,780					11,769	5,597	14,207
Income before income tax expense	$ 17,381	$ 19,610	$ 15,665	$ 18,426	$ 17,990	$ 17,783	$ (17,703)	$ 15,589	12,661	$ 1,708	$ 15,206	$ 15,305	$ 14,861	71,082	33,659	47,080
Income tax (benefit)	(3,832)	(5,392)	(3,634)	(3,507)	(3,123)	(6,956)	2,961	(3,805)	(8,983)	(194)	(5,934)	(5,012)	(4,868)	(16,365)	(10,923)	(16,008)
Net income	$ 13,549	$ 14,218	$ 12,031	$ 14,919	$ 14,867	$ 10,827	$ (14,742)	$ 11,784	3,678	$ 1,514	$ 9,272	$ 10,293	$ 9,993	54,717	22,736	31,072
Accumulated Other Comprehensive (Loss) Income Components
Accumulated Other Comprehensive Income (Loss) [Line Items]
Income before income tax expense									51					(1,097)	2,410	14,432
Income tax (benefit)									(107)					178	(506)	(5,150)
Net income									(56)					(919)	1,904	9,282
Accumulated Other Comprehensive (Loss) Income Components \| Reclassification adjustment for gains (losses) included in net income
Accumulated Other Comprehensive Income (Loss) [Line Items]
Gain (loss) on securities transactions									60					2,612	(116)	2,626
Accumulated Other Comprehensive (Loss) Income Components \| Reclassification adjustment of actuarial net (loss) gain included in net income
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other non-interest expense									$ (9)					$ (3,709)	$ 2,526	$ 11,806

Derivatives and Hedging Activ_3

Derivatives and Hedging Activities - Narrative (Details)	3 Months Ended	12 Months Ended
Derivatives and Hedging Activities - Narrative (Details)	Dec. 31, 2017USD ($)	Dec. 31, 2019USD ($)swap	Dec. 31, 2018USD ($)swap	Sep. 30, 2017USD ($)
Derivative [Line Items]
Accrued interest on derivative, at fair value		$ 344,000	$ 65,000
Net liability position		17,500,000
Collateral against obligations		18,400,000
Interest rate swaps
Derivative [Line Items]
Derivative gains (losses) recorded in the Statements of Income	$ 0	204,000	(52,000)	$ 0
Federal Home Loan Bank advances \| Interest rate swaps
Derivative [Line Items]
Notional amount of derivative		410,000,000	320,000,000
Not-designated hedge \| Currency forward contract - non-designated hedge
Derivative [Line Items]
Notional amount of derivative		0	0
Not-designated hedge \| Interest rate swaps
Derivative [Line Items]
Notional amount of derivative		$ 169,900,000	$ 36,600,000
Number of commercial banking customers \| swap		22	3
Designated as hedging instrument \| Federal Home Loan Bank advances \| Interest rate swaps
Derivative [Line Items]
Notional amount of derivative		$ 410,000,000	$ 320,000,000
Number of interest rate derivatives held \| swap		29	24

Derivatives and Hedging Activ_4

Derivatives and Hedging Activities - Derivative Financial Instruments (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Interest rate swaps \| Designated as hedging instrument \| Other Assets
Derivatives, Fair Value [Line Items]
Derivative assets	$ 185	$ 1,342
Interest rate swaps \| Designated as hedging instrument \| Other Liabilities
Derivatives, Fair Value [Line Items]
Derivative liabilities	11,546	3,944
Carrying Value
Derivatives, Fair Value [Line Items]
Derivative assets	185	1,342
Derivative liabilities	$ 11,546	$ 3,944

Revenue Recognition (Details)

Revenue Recognition (Details) - USD ($) $ in Thousands	3 Months Ended													12 Months Ended
Revenue Recognition (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Dec. 31, 2019	Dec. 31, 2018	Sep. 30, 2017
Disaggregation of Revenue [Line Items]
Total out-of-scope non-interest income														$ 17,333	$ 8,725
Total non-interest income	$ 8,709	$ 10,115	$ 6,775	$ 6,037	$ 6,405	$ 5,290	$ 5,450	$ 4,543	$ 4,733	$ 1,630	$ 4,645	$ 5,806	$ 5,534	31,636	21,688	$ 17,172
Deposit Account, Title Insurance And Other Non-Interest Income
Disaggregation of Revenue [Line Items]
Revenue														14,303	12,963
Demand deposit account fees
Disaggregation of Revenue [Line Items]
Revenue									960					4,478	3,987	3,669
Title insurance fees
Disaggregation of Revenue [Line Items]
Revenue									$ 1,017					4,981	4,297	$ 4,163
Other non-interest income
Disaggregation of Revenue [Line Items]
Revenue														$ 4,844	$ 4,679

Uncategorized Items - a10k2019.

Label	Element	Value
Treasury Stock [Member]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest, Adjusted Balance	us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterestAdjustedBalance1	$ 0
Retained Earnings [Member]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest, Adjusted Balance	us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterestAdjustedBalance1	560,764,000
Additional Paid-in Capital [Member]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest, Adjusted Balance	us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterestAdjustedBalance1	527,037,000
Common Stock [Member]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest, Adjusted Balance	us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterestAdjustedBalance1	1,159,000
Stock Held by Rabbi Trust [Member]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest, Adjusted Balance	us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterestAdjustedBalance1	(1,259,000)
Unallocated Common Stock Held By The Employee Stock Ownership Plan [Member]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest, Adjusted Balance	us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterestAdjustedBalance1	(43,835,000)
Deferred Compensation Obligation [Member]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest, Adjusted Balance	us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterestAdjustedBalance1	639,000
Accounting Standards Update 2016-01 [Member] \| AOCI Attributable to Parent [Member]
Cumulative Effect of New Accounting Principle in Period of Adoption	us-gaap_CumulativeEffectOfNewAccountingPrincipleInPeriodOfAdoption	(548,000)
Accounting Standards Update 2018-02 [Member]
Cumulative Effect of New Accounting Principle in Period of Adoption	us-gaap_CumulativeEffectOfNewAccountingPrincipleInPeriodOfAdoption	0
Accounting Standards Update 2018-02 [Member] \| Retained Earnings [Member]
Cumulative Effect of New Accounting Principle in Period of Adoption	us-gaap_CumulativeEffectOfNewAccountingPrincipleInPeriodOfAdoption	11,708,000
Accounting Standards Update 2018-02 [Member] \| AOCI Attributable to Parent [Member]
Cumulative Effect of New Accounting Principle in Period of Adoption	us-gaap_CumulativeEffectOfNewAccountingPrincipleInPeriodOfAdoption	$ (11,708,000)