Cambridge Bancorp (CATC) 10-K12 Mar 242023 FY Annual reportFinancial data

Company Profile

Document and Entity Information

Document and Entity Information - USD ($) $ in Millions	12 Months Ended
Document and Entity Information - USD ($) $ in Millions	Dec. 31, 2023	Mar. 08, 2024	Jun. 30, 2023
Cover [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2023
Document Fiscal Year Focus	2023
Document Fiscal Period Focus	FY
Trading Symbol	CATC
Entity Registrant Name	CAMBRIDGE BANCORP
Entity Central Index Key	0000711772
Current Fiscal Year End Date	--12-31
Entity Filer Category	Accelerated Filer
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Document Financial Statement Error Correction [Flag]	false
Entity Shell Company	false
Entity Emerging Growth Company	false
Entity Small Business	false
Title of 12(b) Security	Common Stock
Security Exchange Name	NASDAQ
Entity Public Float			$ 391.7
Entity Common Stock, Shares Outstanding		7,846,510
Entity File Number	001-38184
Entity Incorporation, State or Country Code	MA
Entity Tax Identification Number	04-2777442
Entity Address, Address Line One	1336 Massachusetts Avenue
Entity Address, City or Town	Cambridge
Entity Address, State or Province	MA
Entity Address, Postal Zip Code	02138
City Area Code	617
Local Phone Number	876-5500
Document Annual Report	true
Document Transition Report	false
ICFR Auditor Attestation Flag	true
Documents Incorporated by Reference	DOCUMENTS INCORPORATED BY REFERENCE None
Auditor Name	Wolf & Company, P.C.
Auditor Location	Boston, Massachusetts
Auditor Firm ID	392

CONSOLIDATED BALANCE SHEETS

CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Assets
Cash and cash equivalents	$ 33,004	$ 30,719
Investment securities
Available for sale, at fair value (amortized cost $163,376 and $182,027, respectively)	137,838	153,416
Held to maturity, at amortized cost (fair value $805,428 and $885,586, respectively)	959,332	1,051,997
Total investment securities	1,097,170	1,205,413
Loans
Total loans	4,021,544	4,062,856
Less: allowance for credit losses on loans	(38,944)	(37,774)
Net loans	3,982,600	4,025,082
Federal Home Loan Bank of Boston Stock, at cost	19,056	6,264
Bank owned life insurance	35,265	34,484
Banking premises and equipment, net	21,753	23,297
Right-of-use asset operating leases	23,233	25,098
Deferred income taxes, net	15,299	17,990
Accrued interest receivable	15,765	14,118
Goodwill	64,539	64,539
Merger-related intangibles, net	6,550	7,443
Other assets	103,432	105,290
Total assets	5,417,666	5,559,737
Deposits
Demand non interest bearing	1,032,413	1,366,395
Interest-bearing checking	1,132,518	908,961
Money market	983,480	1,162,773
Savings	498,386	790,628
Certificates of deposit	674,381	586,619
Total deposits	4,321,178	4,815,376
Borrowings	452,155	105,212
Operating lease liabilities	25,165	27,413
Other liabilities	84,595	94,184
Total liabilities	4,883,093	5,042,185
Shareholders’ Equity
Common stock, par value $1.00; Authorized 10,000,000 shares; Outstanding: 7,845,452 shares and 7,796,440 shares, respectively	7,845	7,796
Additional paid-in capital	293,950	293,186
Retained earnings	250,492	237,369
Accumulated other comprehensive loss	(17,714)	(20,799)
Total shareholders’ equity	534,573	517,552
Total liabilities and shareholders’ equity	5,417,666	5,559,737
Residential Mortgage
Loans
Total loans	1,626,264	1,648,838
Commercial Mortgage
Loans
Total loans	1,931,473	1,914,423
Home Equity
Loans
Total loans	95,649	111,351
Commercial and Industrial
Loans
Total loans	343,711	350,650
Consumer
Loans
Total loans	$ 24,447	$ 37,594

CONSOLIDATED BALANCE SHEETS (Pa

CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Statement of Financial Position [Abstract]
Available for sale securities, amortized cost	$ 163,376	$ 182,027
Held-to-maturity securities, fair value	$ 805,428	$ 885,586
Common stock, par value	$ 1	$ 1
Common stock, shares authorized	10,000,000	10,000,000
Common stock, shares, outstanding	7,845,452	7,796,440

CONSOLIDATED STATEMENTS OF INCO

CONSOLIDATED STATEMENTS OF INCOME - USD ($) $ in Thousands	12 Months Ended
CONSOLIDATED STATEMENTS OF INCOME - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Interest and dividend income
Interest on taxable loans	$ 193,483	$ 135,965	$ 120,019
Interest on tax-exempt loans	1,555	1,447	1,205
Interest on taxable investment securities	19,589	19,555	9,464
Interest on tax-exempt investment securities	2,215	2,477	2,630
Dividends on FHLB of Boston stock	970	287	46
Interest on overnight investments	722	262	150
Total interest and dividend income	218,534	159,993	133,514
Interest expense
Interest on deposits	84,965	14,598	4,974
Interest on borrowed funds	12,763	2,180	559
Total interest expense	97,728	16,778	5,533
Net interest and dividend income	120,806	143,215	127,981
Provision for (release of) credit losses	904	3,881	(1,294)
Net interest and dividend income after provision for credit losses	119,902	139,334	129,275
Noninterest income
Bank owned life insurance income	778	1,808	801
Gain on loans sold, net	56	98	832
Loan related derivative income	399	625	2,124
Other income	2,420	2,868	2,024
Total noninterest income	41,730	43,009	44,324
Noninterest expense
Salaries and employee benefits	69,806	70,109	65,127
Occupancy and equipment	14,454	14,364	13,898
Data processing	10,313	10,706	8,829
Professional services	3,675	4,728	5,391
Marketing	1,773	2,301	2,536
FDIC insurance	2,835	1,845	1,318
Non-operating expenses	7,180	3,059	1,118
Other expenses	5,187	3,270	2,267
Total noninterest expense	115,223	110,382	100,484
Income before income taxes	46,409	71,961	73,115
Income tax expense	12,300	19,052	19,091
Net income	$ 34,109	$ 52,909	$ 54,024
Share data:
Weighted average shares outstanding, basic	7,828,316	7,163,223	6,926,257
Weighted average shares outstanding, diluted	7,843,482	7,213,913	6,990,603
Basic earnings per share	$ 4.35	$ 7.35	$ 7.76
Diluted earnings per share	$ 4.34	$ 7.3	$ 7.69
Wealth Management Revenue
Noninterest income
Noninterest income	$ 33,004	$ 33,034	$ 35,037
Deposit Account Fees
Noninterest income
Noninterest income	3,345	2,913	1,939
ATM/Debit Card Income
Noninterest income
Noninterest income	$ 1,728	$ 1,663	$ 1,567

CONSOLIDATED STATEMENTS OF COMP

CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Statement of Comprehensive Income [Abstract]
Net income		$ 34,109	$ 52,909	$ 54,024
Available for sale securities
Unrealized holding gains (losses)		2,336	(18,736)	(4,622)
Interest rate swaps designated as cash flow hedges
Unrealized holding losses		(495)	(1,563)	(959)
Less: reclassification adjustment for gains (losses) realized in net income	[1]	389	(600)	(1,864)
Total unrealized losses on interest rate swaps		(106)	(2,163)	(2,823)
Defined benefit retirement plans
Change in retirement liabilities		855	1,310	3,801
Other comprehensive income (loss)		3,085	(19,589)	(3,644)
Comprehensive income		$ 37,194	$ 33,320	$ 50,380

[1] Reported in interest on payable loans line item in the Consolidated Statements of Income.

CONSOLIDATED STATEMENTS OF CHAN

CONSOLIDATED STATEMENTS OF CHANGES IN SHAREHOLDERS' EQUITY - USD ($) $ in Thousands	Total	North Mark Merger	Common Stock	Common Stock North Mark Merger	Additional Paid-In Capital	Additional Paid-In Capital North Mark Merger	Retained Earnings	Accumulated Other Comprehensive Income / (Loss)
Beginning balance at Dec. 31, 2020	$ 401,732		$ 6,927		$ 226,967		$ 165,404	$ 2,434
Net income	54,024						54,024
Other comprehensive income (loss)	(3,644)							(3,644)
Share based compensation and other share-based activity	2,279		41		2,238
Dividends declared	(16,554)						(16,554)
Ending balance at Dec. 31, 2021	437,837		6,968		229,205		202,874	(1,210)
Net income	52,909						52,909
Other comprehensive income (loss)	(19,589)							(19,589)
Share based compensation and other share-based activity	1,959		39		1,920
Dividends declared	(18,414)						(18,414)
Common stock issued for Northmark merger		$ 62,850		$ 789		$ 62,061
Ending balance at Dec. 31, 2022	517,552		7,796		293,186		237,369	(20,799)
Net income	34,109						34,109
Other comprehensive income (loss)	3,085							3,085
Share based compensation and other share-based activity	813		49		764
Dividends declared	(20,986)						(20,986)
Ending balance at Dec. 31, 2023	$ 534,573		$ 7,845		$ 293,950		$ 250,492	$ (17,714)

CONSOLIDATED STATEMENTS OF CH_2

CONSOLIDATED STATEMENTS OF CHANGES IN SHAREHOLDERS' EQUITY (Parenthetical) - $ / shares	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Retained Earnings
Dividends declared, per share	$ 2.68	$ 2.56	$ 2.38

CONSOLIDATED STATEMENTS OF CASH

CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
CASH FLOWS FROM OPERATING ACTIVITIES
Net income	$ 34,109	$ 52,909	$ 54,024
Adjustments to reconcile net income to net cash provided by operating activities:
Provision for (release of) credit losses	904	3,881	(1,294)
Amortization (accretion) of deferred charges and fees, net	2,330	2,282	(1,434)
Depreciation (accretion), and amortization, net	1,193	726	(1,838)
Bank owned life insurance income	(778)	(1,808)	(801)
Share-based compensation and other share-based activity	813	1,959	2,279
Change in accrued interest receivable	(1,647)	(4,280)	352
Deferred income tax expense	1,665	587	2,899
Change in loans held for sale		1,490	5,419
Change in other assets, net	2,950	(32,056)	5,473
Change in other liabilities, net	(8,449)	26,260	429
Net cash provided by operating activities	33,090	51,950	65,508
CASH FLOWS FROM INVESTING ACTIVITIES
Origination of loans	(650,604)	(1,265,305)	(1,327,044)
Proceeds from principal payments of loans	692,563	850,886	1,170,430
Purchase of loans		(23,655)
Proceeds from calls/maturities of securities available for sale	18,414	29,040	42,169
Purchase of securities available for sale		(10,170)	(9,927)
Proceeds from sales of securities		19,018
Proceeds from calls/maturities of securities held to maturity	91,558	132,173	70,800
Purchase of securities held to maturity		(205,137)	(801,775)
Death benefit on bank-owned life insurance		4,025
Redemption on bank-owned life insurance		10,759
(Purchase) redemption of FHLB of Boston stock	(12,792)	(1,215)	918
Purchase of banking premises and equipment	(1,372)	(1,776)	(2,033)
Net cash acquired in business combinations		82,174
Net cash provided by (used in) investing activities	137,767	(379,183)	(856,462)
CASH FLOWS FROM FINANCING ACTIVITIES
Change in demand, interest-bearing, money market and savings accounts	(581,959)	(216,751)	1,020,821
Change in certificates of deposit	87,430	327,938	(92,552)
Change in borrowings	346,943	85,026	(16,393)
Cash dividends paid on common stock	(20,986)	(18,414)	(16,554)
Net cash (used in) provided by financing activities	(168,572)	177,799	895,322
Net change in cash and cash equivalents	2,285	(149,434)	104,368
Cash and cash equivalents at beginning of period	30,719	180,153	75,785
Cash and cash equivalents at end of period	33,004	30,719	180,153
Cash paid during the period for:
Interest	92,544	15,805	5,656
Income taxes	$ 12,902	21,822	$ 9,054
Significant non-cash transactions
Common Stock issued to shareholders due to merger		62,850
Fair value of assets acquired, net of cash acquired		346,501
Fair value of liabilities assumed		$ 378,453

Pay vs Performance Disclosure

Pay vs Performance Disclosure - USD ($) $ in Thousands	12 Months Ended
Pay vs Performance Disclosure - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Pay vs Performance Disclosure
Net Income (Loss)	$ 34,109	$ 52,909	$ 54,024

Insider Trading Arrangements

Insider Trading Arrangements	3 Months Ended
Insider Trading Arrangements	Dec. 31, 2023
Trading Arrangements, by Individual
Rule 10b5-1 Arrangement Adopted	false
Non-Rule 10b5-1 Arrangement Adopted	false
Rule 10b5-1 Arrangement Terminated	false
Non-Rule 10b5-1 Arrangement Terminated	false

Insider Trading Policies and Pr

Insider Trading Policies and Procedures	12 Months Ended
Insider Trading Policies and Procedures	Dec. 31, 2023
Insider Trading Policies and Procedures [Line Items]
Insider Trading Policies and Procedures Adopted	true

The Business

The Business	12 Months Ended
The Business	Dec. 31, 2023
Organization, Consolidation and Presentation of Financial Statements [Abstract]
The Business	1. THE BUSINESS The accompanying consolidated financial statements include the accounts of Cambridge Bancorp (the “Company”) and its wholly owned subsidiary, Cambridge Trust Company (the “Bank”), and the Bank’s subsidiaries, Cambridge Trust Company of New Hampshire, Inc., CTC Security Corporation, and CTC Security Corporation III. References to the Company herein relate to the consolidated group of companies. All significant intercompany accounts and transactions have been eliminated in preparation of the consolidated financial statements. The Company is a state-chartered, federally registered bank holding company headquartered in Cambridge, Massachusetts, incorporated in 1983. The Company is the sole shareholder of the Bank, a Massachusetts trust company chartered in 1890 which is a commercial bank. The Company is a private bank offering a full range of private banking and wealth management services to its clients. The private banking business, the Company’s only reportable operating segment, is managed as a single strategic unit. As a private bank, the Company focuses on four core services that center around client needs. The core services include Wealth Management, Commercial Banking, Residential Lending, and Personal Banking. The Bank offers a full range of commercial and consumer banking services through its network of 22 banking offices in Massachusetts and New Hampshire. The Bank is engaged principally in the business of attracting deposits from the public and investing those deposits. The Bank invests those funds in various types of loans, including residential and commercial real estate, and a variety of commercial and consumer loans. The Bank also invests its deposits and borrowed funds in investment securities and has two wholly owned Massachusetts security corporations, CTC Security Corporation and CTC Security Corporation III, for this purpose. Deposits at the Bank are insured by the Federal Deposit Insurance Corporation (“FDIC”) for the maximum amount permitted by FDIC Regulations. Trust and investment management services are offered through the Bank’s private banking offices in Massachusetts and New Hampshire, and its wealth management offices located in Boston, Massachusetts, Concord, Manchester, and Portsmouth, New Hampshire, and Southport, Connecticut . The Bank also has a non-depository trust company, Cambridge Trust Company of New Hampshire, Inc., which allows non-New Hampshire residents the opportunity to take advantage of the state’s favorable trust laws. The assets held for wealth management clients are not assets of the Bank and, accordingly, are not reflected in the accompanying consolidated balance sheets.

Summary of Significant Accounti

Summary of Significant Accounting Policies	12 Months Ended
Summary of Significant Accounting Policies	Dec. 31, 2023
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	2. SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES Basis of Presentation The consolidated financial statements have been prepared in conformity with U.S. generally accepted accounting principles (“GAAP”). Use of Estimates The preparation of consolidated financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the consolidated financial statements. Actual results could differ from those estimates. The allowance for credit losses, the valuation of deferred tax assets, and the valuation of assets acquired and liabilities assumed in business combinations are particularly subject to change. Reclassifications Certain amounts in the prior year’s financial statements may have been reclassified to conform with the current year’s presentation. Cash and Cash Equivalents Cash and cash equivalents consist of cash on hand, amounts due from banks, and overnight investments. Investment Securities Investment securities are classified as either “held to maturity” or “available for sale” in accordance with the Financial Accounting Standards Board (“FASB”) Accounting Standards Codification (“ASC”) Topic 320, Investments – Debt Securities. Debt securities that management has the positive intent and ability to hold to maturity are classified as held to maturity and recorded at amortized cost. Debt securities not classified as held to maturity are classified as available for sale and carried at fair value with unrealized after-tax gains and losses reported net as a separate component of shareholders’ equity. The Company classifies its securities based on its intention at the time of purchase. Purchase premiums and discounts are recognized in interest income using the effective yield or straight-line method over the term of the securities, except for callable debt securities for which the purchase premiums are recognized through the earliest call date. Gains and losses on the sale of debt securities are recorded on the trade date and determined using the specific identification method. Allowance for Credit Losses - Held to Maturity Securities The Company measures expected credit losses on held to maturity debt securities on a collective basis by security type and risk rating where available. The reserve for each pool is calculated based on a Probability of Default/Loss Given Default (“PD/LGD”) basis taking into consideration the expected life of each security. Held to maturity securities which are issued by the United States of America (“U.S.”) or are guaranteed by U.S. federal agencies do not currently have an allowance for credit loss as the Company determined these securities are either backed by the full faith and credit of the U.S. government and/or there is an unconditional commitment to make interest payments and to return the principal investment in full to investors when a debt security reaches maturity. The Company will evaluate this position no less than annually, however, certain items which may cause the Company to change this methodology include legislative changes that remove a government-sponsored enterprise’s (“GSE”) ability to draw funds from the U.S. government, or legislative changes to housing policy that reduce or eliminate the U.S. government’s implicit guarantee on such securities. For securities which are not U.S. treasury or agency backed, risk ratings are generally sourced from Moody’s or Standard & Poor’s. The Company updates loss given default, probability of default, and recovery rates for each security as that information becomes available but no less than annually. The expected remaining life to maturity of each applicable security is updated quarterly. Any expected credit losses on held to maturity securities would be presented as an allowance rather than as a direct write-down through the consolidated statements of income if the Company does not intend to sell or believes that it is more likely than not that the Company will be required to sell the security. Allowance for Credit Losses - Available for Sale Securities The Company measures expected credit losses on available for sale securities based upon the gain or loss position of the security. For available for sale debt securities in an unrealized loss position, which the Company does not intend to sell, or it is not more likely than not that the Company will be required to sell the security before recovery of the Company’s amortized cost, the Company evaluates qualitative criteria to determine any expected loss. This includes among other items the financial health of, and specific prospects for the issuer, including whether the issuer is in compliance with the terms and covenants of the security. The Company also evaluates quantitative criteria including determining whether there has been an adverse change in expected future cash flows of the security. If the Company does not expect to recover the entire amortized cost basis of the security, an allowance for credit losses would be recorded, with a related charge to earnings, limited by the amount of the fair value of the security less its amortized cost. If the Company intends to sell the security or it is more likely than not that the Company will be required to sell the debt security before recovery of its amortized cost basis, the Company recognizes the entire difference between the security’s amortized cost basis and its fair value in earnings. Loans Loans are reported at the amount of their outstanding principal, including deferred loan origination fees and costs, reduced by unearned discounts, and the allowance for credit losses. Loans are considered delinquent when a payment of principal and/or interest becomes past due 30 days following its scheduled payment due date. Loans on which the accrual of interest has been discontinued are designated as non-accrual loans. Loans may be removed from non-accrual when they become less than 90 days past due, they have maintained current payment status for a sustained period of time, and when concern no longer exists as to the collectability of principal or interest. Allowance for Credit Losses - Loans Losses on loan receivables are estimated and recognized upon origination of the loan, based on expected credit losses for the life of the loan balance as of the period end date. The Company’s methodology for calculating the allowance for credit losses (“ACL”) on loans consists of quantitative and qualitative components. The Company uses a discounted cash flow method incorporating probability of default and loss given default forecasted based on statistically derived economic variable loss drivers combined with qualitative factors, to estimate expected credit losses. This process includes estimates which involve modeling loss projections attributable to existing loan balances, considering historical experience, current conditions, and future expectations for homogeneous pools of loans over the reasonable and supportable forecast period. The reasonable and supportable forecast period is determined based upon the accuracy level of historical loss forecast estimates, the specific loan level models and methodology utilized, and considers material changes in growth and credit strategy, and business changes. For periods beyond a reasonable and supportable forecast interval, the Company reverts to historical information over a period for which comparable data is available. The historical information either experienced by the Company, or by a selection of peer banks when appropriate, is derived from a combination of recessionary and non-recessionary performance periods for which data is available. Similar to the reasonable and supportable forecast period, the Company reassesses the reversion period at the segment level, considering any required adjustments for differences in underwriting standards, portfolio mix, and other relevant data shifts over time. The Company generally segments its loan receivable population into homogeneous pools of loans. Consistent with the Company’s other assumptions, the Company regularly reviews segmentation to determine whether the homogeneous pools remain relevant as risk characteristics change. When a loan no longer meets the criteria of its initial pooling as a result of credit deterioration or other changes, the Company may evaluate the credit for estimated losses on an individual basis if the Company determines that the credit no longer retains the same risk characteristics. To the extent that there are a multitude of these loans with new similar risk characteristics, the Company would anticipate a change to the pooling methodology. Loans that do not share risk characteristics are evaluated on an individual basis and are not included in the collective evaluation. For loans with real estate collateral, when management determines that foreclosure is probable, expected credit losses are based on the fair value of the collateral at the reporting date, adjusted for selling costs as appropriate. The qualitative component of the ACL considers (i) the uncertainty of forward-looking scenarios; (ii) certain portfolio characteristics, such as portfolio concentrations, real estate values, changes in the number and amount of non-accrual and past due loans; and (iii) model limitations; among other factors. Qualitative adjustments are considered when management believes expected credit losses are not representative of historical loss experience alone, and should be adjusted to reflect the current conditions and characteristics of the Company’s own portfolio. They are made at the segment level, considering any required adjustments for differences in underwriting standards, portfolio mix, and other relevant data shifts over time. The Company evaluates the allowance for credit losses on loans quarterly. The Company regularly reviews its collection experience (including delinquencies and net charge-offs) in determining its allowance for credit losses. The Company also considers its historical loss experience to date based on actual defaulted loans and overall portfolio indicators including delinquent and non-accrual loans, trends in loan volume and lending terms, credit policies and other observable environmental factors such as unemployment and interest rate changes. The underlying assumption estimates and assessments the Company uses to estimate the allowance for credit losses reflects the Company’s best estimate of model assumptions and forecasted conditions at that time. Changes in such estimates can significantly affect the allowance and provision for (release of) credit losses. It is possible and likely that the Company will experience credit losses that are different from the current estimates. The provision for (release of) credit losses charged to income is based on management’s judgment of the amount necessary to maintain the allowance at a level to provide for expected credit losses for the life of the loan balances as of the evaluation date. When management believes that the collectability of a loan’s principal balance, or portions thereof, is unlikely, the principal amount is charged against the allowance for credit losses. Recoveries on loans that have been previously charged off are credited to the allowance for credit losses, generally at the time cash is received on a charged-off account. The allowance is an estimate, and ultimate losses may vary from current estimates. As adjustments become necessary, they are reported in the results of operations through the provision for (release of) credit losses in the period in which they become known. Risk characteristics relevant to each portfolio segment are as follows: Residential mortgage and home equity loans – The Company generally does not originate loans in these segments with a loan-to-value ratio greater than 80 %, unless covered by private mortgage insurance, and in all cases not greater than a loan-to-value ratio of 97 %. The Company does not originate subprime loans. Loans in these segments are secured by one-to-four family residential real estate, and repayment is primarily dependent on the credit quality of the individual borrower. Commercial mortgage loans – This includes multi-family properties and construction. The Company generally does not originate loans in this segment with a loan-to-value ratio greater than 75 % . Loans in this segment are secured by owner-occupied and non-owner-occupied commercial real estate (“CRE”), and repayment is primarily dependent on the cash flows of the property (if non-owner-occupied) or of the business (if owner-occupied). Commercial and industrial loans (“C&I”) – Loans in this segment are made to businesses and are generally secured by equipment, accounts receivable, or inventory, as well as the personal guarantees of the principal owners of the business, and repayment is primarily dependent on the cash flows generated by the business. In addition, this segment includes certain loans issued under the U. S. Small Business Administration’s (“SBA”) Paycheck Protection Program (“PPP”). These loans are guaranteed and are not evaluated for an allowance for credit losses because the Company expects the guarantees will be effective, if necessary. Consumer loans – Loans in this segment are made to individuals and can be secured or unsecured. Repayment is primarily dependent on the credit quality of the individual borrower. The majority of the Company’s loans are concentrated in Eastern Massachusetts and Southern New Hampshire and therefore the overall health of the local economy, including unemployment rates, vacancy rates, and consumer spending levels, can have a material effect on the credit quality of all of these portfolio segments. The process to determine the allowance for credit losses requires management to exercise considerable judgment regarding the risk characteristics of the loan portfolio segments and the effect of relevant internal and external factors. Allowance for Credit Losses - Unfunded Commitments The expected credit losses for unfunded commitments are measured over the contractual period of the Company’s exposure to credit risk. The estimate of credit loss incorporates assumptions for both the likelihood and amount of funding over the estimated life of the commitments, for the risk of loss, and current conditions and expectations. Management periodically reviews and updates its assumptions for estimated funding rates based on historical rates, and factors such as portfolio growth, changes to organizational structure, economic conditions, borrowing habits, or any other factor which could impact the likelihood that funding will occur. The Company does not reserve for unfunded commitments which are unconditionally cancellable. Acquired Loans Acquired loans are recorded at fair value at the date of acquisition based on a discounted cash flow methodology that considers various factors, including the type of loan and related collateral, classification status, fixed or variable interest rate, term of loan and whether or not the loan was amortizing, and a discount rate reflecting the Company’s assessment of risk inherent in the cash flow estimates. Purchased loans are grouped together according to similar risk characteristics and are treated in the aggregate when applying various valuation techniques. These cash flow evaluations are inherently subjective as they may be susceptible to significant change. Effective January 1, 2020, loans acquired in a business combination that have experienced more-than-insignificant deterioration in credit quality since origination are considered purchased credit deteriorated (“PCD”) loans. The Company evaluates acquired loans for deterioration in credit quality based on, but not limited to, the following: (1) non-accrual status; (2) troubled debt restructured designation; (3) risk ratings of special mention, substandard or doubtful; (4) watchlist credits; and (5) delinquency status, including loans that are current on acquisition date, but had been previously delinquent. At the acquisition date, an estimate of expected credit losses is made for groups of PCD loans with similar risk characteristics and individual PCD loans without similar risk characteristics. This initial allowance for credit losses is allocated to individual PCD loans and added to the purchase price or acquisition date fair values to establish the initial amortized cost basis of the PCD loans. As the initial allowance for credit losses is added to the purchase price, there is no credit loss expense recognized upon acquisition of a PCD loan. Any difference between the unpaid principal balance of PCD loans and the amortized cost basis is considered to relate to noncredit factors and results in a discount or premium. Discounts and premiums are recognized through interest income on a level-yield method over the life of the loans. For acquired loans not deemed PCD at acquisition, the differences between the initial fair value and the unpaid principal balance are recognized as interest income on a level-yield basis over the lives of the related loans. At the acquisition date, an initial allowance for expected credit losses is estimated and recorded as provision for credit losses. The subsequent measurement of expected credit losses for all acquired loans is the same as the subsequent measurement of expected credit losses for originated loans. Loans Held for Sale Residential mortgage loans originated and intended for sale in the secondary market are classified as held for sale at the time of their origination and are carried at the lower of cost or fair value on an individual loan basis. Changes in fair value relating to loans held for sale below the loans cost basis are charged against gain on loans sold. Gains and losses on the actual sale of the residential loans are recorded in earnings as gains on loans sold, net on the consolidated statements of income. Bank Owned Life Insurance Bank owned life insurance (“BOLI”) represents life insurance on the lives of certain active and former employees who have provided positive consent allowing the Company to be the beneficiary of such policies. Since the Company is the primary beneficiary of the insurance policies, increases in the cash value of the policies, as well as insurance proceeds received in excess of cash surrender value, are recorded in noninterest income, and are not subject to income taxes. Applicable regulations generally limit the Company’s investment in BOLI to 25 % of its Tier 1 capital plus its allowance for credit losses. The Company reviews the financial strength of the insurance carriers prior to the purchase of BOLI and at least annually thereafter. Banking Premises and Equipment Land is stated at cost. Buildings, leasehold improvements, and equipment are stated at cost, less accumulated depreciation, and amortization, which is computed using the straight-line method over the estimated useful lives of the assets or the terms of the leases, if shorter. The cost of ordinary maintenance and repairs is charged to expense when incurred. Leases The Company leases office space and certain branch locations under noncancelable operating leases, several of which have renewal options to extend lease terms. Upon commencement of a new lease, the Company will recognize a right-of-use (“ROU”) asset and corresponding lease liability. The Company makes the decision on whether to renew an option to extend a lease by considering various factors. The Company will recognize an adjustment to its ROU asset and lease liability when lease agreements are amended and executed. The discount rate used in determining the present value of lease payments is based on the Company’s incremental borrowing rate for borrowings with terms similar to each lease at commencement date. The Company has lease agreements with lease and non-lease components, which are generally accounted for separately. For real estate leases, non-lease components and other non-components, such as common area maintenance charges, real estate taxes, and insurance, are not included in the measurement of the lease liability since they are generally able to be segregated. Marketing Expense Advertising costs are expensed as incurred. Other Real Estate Owned Other real estate owned consists of properties formerly pledged as collateral to loans, which have been acquired by the Company through foreclosure proceedings or acceptance of a deed in lieu of foreclosure. Upon transfer of a loan to foreclosure status, an appraisal is obtained and any excess of the loan balance over the fair value, less estimated costs to sell, is charged against the allowance for credit losses. Expenses and subsequent adjustments to the fair value are treated as noninterest expense through other expenses. Goodwill, Core Deposit Intangibles, and Other Intangible Assets Goodwill represents the excess of the purchase price over the fair value of net assets acquired in a business combination. Core deposit intangible (“CDI”) represents a premium paid to acquire the core deposits of an institution and is recorded as an intangible asset. Goodwill and intangible assets that are not amortized are tested for impairment, based on their fair values, at least annual ly. There was no goodwill impairment recognized during 2023, 2022, or 2021. Identifiable intangible assets that are subject to amortizatio n are also reviewed for impairment based on their fair value. Any impairment is recognized as a charge to earnings and the adjusted carrying amount of the intangible asset becomes its new accounting basis. The remaining useful life of an intangible asset that is being amortized is also evaluated each reporting period to determine whether events and circumstances warrant a revision to the remaining period of amortization. The Company is amortizing the CDI on a straight-line basis over a ten-year period. Mortgage servicing rights (“MSR”) are recognized as separate assets when rights are acquired through purchase or through sale of financial assets with servicing rights retained. The fair value of the servicing rights is determined by estimating the present value of future net cash flows, taking into consideration market loan prepayment speeds, discount rates, servicing costs, and other economic factors. For purposes of measuring impairment, the underlying loans are generally stratified into relatively homogeneous pools based on predominant risk characteristics. Because of the small size of this asset class, and its relative homogeneity, only one stratum is used. I f the aggregate carrying value of the capitalized mortgage servicing rights for this stratum exceeds its fair value, MSR impairment is recognized in earnings through a valuation allowance for the difference. As the loans are repaid and net servicing revenue is earned, the MSR asset is amortized as an offset to loan servicing income. Servicing revenues are expected to exceed this amortization expense. However, if actual prepayment experience or defaults exceed what was originally anticipated, net servicing revenues may be less than expected and mortgage servicing income may be negative. Income Taxes The Company and its subsidiaries file income tax returns in the U.S. federal jurisdiction, the Commonwealth of Massachusetts, the state of New Hampshire, the State of Connecticut, the state of Maine, and other states as required. For the tax year ended December 31, 2023, the Company expects to file taxes in Massachusetts, New Hampshire, and Maine. Income taxes are accounted for under the asset and liability method. Deferred tax assets and liabilities are reflected at currently enacted income tax rates applicable to the period in which the deferred tax assets or liabilities are expected to be realized or settled. As changes in tax laws or rates are enacted, deferred tax assets and liabilities are adjusted through income tax expenses in the period of enactment. Deferred tax assets are reviewed quarterly and reduced by a valuation allowance if, based upon the information available, it is more likely than not that some or all of the deferred tax assets will not be realized. Interest and penalties related to unrecognized tax benefits, if incurred, are recognized as a component of income tax expense. Wealth Management Fee Revenue The Company earns wealth management fees for providing investment management, trust administration, and financial planning services to clients. The Company’s performance obligation under these contracts is satisfied over time as the wealth management services are provided. Fees are recognized monthly based on the monthly value of the assets under management and the applicable fee rate, or at a fixed annual rate, depending on the terms of the contract. No performance-based incentives are earned on wealth management contracts. The Company also earns trust fees for servicing as trustee for certain clients. As trustee, the Company serves as a fiduciary, administers the client’s trust, and in some cases, manages the assets of the trust. The Company’s performance obligation under these agreements is satisfied over time as the administrative and management services are provided. Fees are recognized monthly based on a percentage of the market value of the account or at a fixed annual rate as outlined in the agreement. The Company also earns fees for trust related activities. The Company’s performance obligation under these agreements is satisfied at a point in time and recognized when these services have been performed. Other Banking Fee Income The Company charges a variety of fees to its clients for services provided on the deposit and deposit management related accounts. Each fee is either transaction-based or assessed monthly. The types of fees include service charges on accounts, wire transfer fees, maintenance fees, ATM fee charges, and other miscellaneous charges related to the accounts. These fees are not governed by individual contracts with clients. They are charged to clients based on disclosures presented to these clients upon opening these accounts, along with updated disclosures when changes are made to the fee structures. The transaction-based fees are recognized in revenue when charged to the client based on specific activity on the client’s account. Monthly service and maintenance charges are recognized in the month they are earned and are charged directly to the client’s account. Pension and Retirement Plans The Company sponsors a defined benefit pension plan (the “Pension Plan”) and a postretirement health care plan covering substantially all employees hired before May 2, 2011. Effective December 31, 2017, the accrual of benefits for all participants in the Pension Plan was frozen. Benefits for the postretirement health care plan are based on years of service. Expenses for the postretirement health care plan are recognized over the employee’s service life utilizing the projected unit credit actuarial cost method. Effective November 7, 2019, the postretirement health care plan was frozen for employees hired after that date. The Company also sponsors non-qualified retirement programs that provide supplemental retirement benefits to certain current and former executives. Prior to 2016, the Company provided individual non-qualified defined benefit supplemental executive retirement plans (“DB SERPs”) to certain executives. The DB SERPs generally provide for an annual benefit payable in equal monthly installments following the executive’s retirement and continuing for at least the remainder of his or her lifetime, with such annual benefit generally based on the executive’s years of service and his or her highest three consecutive years of base salary and bonus. In 2016, the Company’s Board of Directors discontinued the use of DB SERPs for new entrants to the Company’s non-qualified retirement programs. Instead, new entrants are provided with individual non-qualified defined contribution supplemental executive retirement plans (“DC SERPs”). Under the DC SERPs, the Company may contribute an amount equal to 10 % of the executive’s base salary and bonus to his or her account under the Company’s non-qualified deferred compensation plan, the Executive Deferred Compensation Plan. Expense for the DB SERPs is recognized over the executive’s service life utilizing the projected unit credit actuarial cost method. Expense for the DC SERPs is recognized as incurred. The Company maintains a Profit-Sharing Plan (“PSP”) that provides for deferral of federal and state income taxes on employee contributions allowed under Section 401(k) of federal law. The Company matches employee contributions up to 100 % of the first 4 % of each participant’s salary, eligible bonus, and eligible incentive. Each year, the Company may also make a discretionary contribution to the PSP based on eligible salary, bonus, and incentive. Employees are eligible to participate in the PSP on the first day of their initial date of service. Employees are also eligible to participate in the discretionary contribution portion of the PSP on the first date of their initial date of service. The employee must be employed on the last day of the calendar year or retire at the normal retirement age of 65 during the calendar year to receive the discretionary contribution. Share-Based Compensation Share-based compensation plans provide for stock option awards, restricted stock awards, time-based restricted stock units (“RSUs”), and performance-based restricted stock units (“PRSUs”). Compensation expense for restricted stock awards is recognized over the vesting period based on the fair value at the date of grant. RSUs and PRSUs are valued at the fair market value of the Company’s common stock as of the award date. PRSUs’ compensation expense is based on the most recent performance assumption available and is adjusted as assumptions change. If the goals are not met, vesting does not occur, no compensation cost will be recognized and any recognized compensation costs will be reversed. Stock-based awards that do not require future service are expensed in the year of grant. Derivative Instruments and Hedging Activities Derivatives are recognized as either assets or liabilities on the consolidated balance sheets and are measured at fair value. The accounting for changes in the fair value of such derivatives depends on the intended use of the derivative and resulting designation. For derivatives not designated as hedges, changes in fair value of the derivative instruments are recognized in earnings in noninterest income. For derivatives designated as fair value hedges, changes in the fair value of such derivatives are recognized in earnings together with the changes in the fair value of the related hedged item. The net amount, if any, represents hedge ineffectiveness and is reflected in earnings. For derivatives designated as cash flow hedges, the effective portion of changes in the fair value of the derivative is recorded in other comprehensive income (loss) and recognized in earnings when the hedged transaction affects earnings. The ineffective portion of changes in the fair value of cash flow hedges is recognized directly in earnings. Fair Value Measurements Fair value is defined as the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date. The Company measures the fair values of its financial instruments in accordance with accounting guidance that requires an entity to base fair value on exit price and maximize the use of observable inputs and minimize the use of unobservable inputs to determine the exit price. ASC 820, “ Fair Value Measurements and Disclosures” establishes a fair value hierarchy that gives the highest priority to quoted prices in active markets and the lowest priority to unobservable data and requires fair value measurements to be disclosed by level within the hierarchy. The three broad levels defined by the fair value hierarchy are as follows: Level 1 – Quoted prices are available in active markets for identical assets or liabilities as of the reported date. The type of financial instruments included in Level 1 are highly liquid cash instruments with quoted prices such as government or agency securities, listed equities, and money market securities, as well as listed derivative instruments. Level 2 – Pricing inputs are other than quoted prices in active markets, which are either directly or indirectly observable as of the reported date. The nature of these financial instruments includes cash instruments for

Recently Issued and Adopted Acc

Recently Issued and Adopted Accounting Standards	12 Months Ended
Recently Issued and Adopted Accounting Standards	Dec. 31, 2022
Accounting Standards Update and Change in Accounting Principle [Abstract]
Recently Issued and Adopted Accounting Standards	3. Recently Issued and Adopted Accounting Standards Accounting Pronouncements Adopted in 2023 In March 2022, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) 2022-02, Financial Instruments – Credit Losses (Topic 326): Troubled Debt Restructurings and Vintage Disclosures. The amendments in this ASU eliminate the accounting guidance for troubled debt restructurings (“TDRs”) by creditors in Subtopic 310-40, Receivables – Troubled Debt Restructurings by Creditors , while enhancing disclosure requirements for certain loan refinancings and restructurings by creditors when a borrower is experiencing financial difficulty. For public business entities, the amendments in this ASU require an entity to disclose current-period gross write-offs by year of origination for financing receivables and net investments in leases. This ASU was effective for fiscal years beginning after December 15, 2022, including interim periods within those fiscal years. Early adoption was permitted. The Company adopted the new standard on January 1, 2023 and the adoption did not have a material impact on the consolidated financial statements. In March 2022, the FASB issued ASU 2022-01, Derivatives and Hedging (Topic 815): Fair Value Hedging - Portfolio Layer Method . The amendments in this ASU allow multiple hedged layers to be designated for a single closed portfolio of financial assets or one or more beneficial interests secured by a portfolio of financial instruments. The amendments in this ASU also clarify the accounting for and promote consistency in the reporting of hedge basis adjustments applicable to both a single hedged layer and multiple hedged layers. These amendments are effective for fiscal years beginning after December 15, 2022, and interim periods within those fiscal years. The Company adopted the new standard on January 1, 2023 and provided the additional disclosures required for the Company's fair value hedging relationships. Accounting Pronouncements Yet to be Adopted In December 2023, the FASB issued ASU 2023-09, Income Taxes (Topic 740): Improvements to Income Tax Disclosures. The amendments are to enhance the transparency and decision usefulness of income tax disclosures. The ASU requires that public business entities on an annual basis (1) disclose specific categories in the rate reconciliation, (2) provide additional information for reconciling items that meet a quantitative threshold. and also includes certain other amendments to improve the effectiveness of income tax disclosures. The amendments in this Update are effective for annual periods beginning after December 15, 2024. The Company is currently assessing the impact the adoption of this guidance will have on its consolidated financial statements and disclosures.

Mergers

Mergers	12 Months Ended
Mergers	Dec. 31, 2023
Business Combinations [Abstract]
Mergers	4. Mergers Eastern Bankshares, Inc. On September 19, 2023, the Company, the Bank, Eastern Bankshares, Inc. (“Eastern”), Eastern Bank, Eastern’s subsidiary bank, and Citadel MS 2023, Inc. a direct, wholly owned subsidiary of Eastern (“Merger Sub”) entered into an Agreement and Plan of Merger (the “Merger Agreement”). Pursuant to the terms and subject to the conditions set forth in the Merger Agreement, Eastern will acquire the Company and the Bank through the merger of Merger Sub with and into the Company, with the Company as the surviving entity (the “Merger”). As soon as reasonably practicable following the Merger, the Company will merge with and into Eastern, with Eastern as the surviving entity (the “Holdco Merger”). The Merger Agreement further provides that following the Holdco Merger, at a time to be determined by Eastern, the Bank will merge with and into Eastern Bank, with Eastern Bank as the surviving entity. Upon the terms and conditions set forth in the Merger Agreement, at the effective time of the Merger (the “Effective Time”) each share of Company common stock, par value $ 1.00 per share, outstanding immediately prior to the Effective Time, other than certain shares held by Eastern or the Company, will be converted into the right to receive 4.956 shares of common stock (the “Exchange Ratio”), par value $ 0.01 per share, of Eastern (“Eastern Common Stock”). Company shareholders will receive cash in lieu of fractional shares of Eastern Common Stock (the Exchange Ratio and any cash in lieu of fractional shares collectively, the “Merger Consideration”). Northmark Bank The Company completed its merger (the “Northmark Merger”) with Northmark Bank. (“Northmark”) on October 1, 2022 Under the terms of the Agreement and Plan of Merger, each outstanding share of Northmark common stock was converted into 0.9950 shares of the Company’s common stock. As a result of the merger, former Northmark stockholders received an aggregate of 788,137 shares of the Company's common stock. The total consideration paid amounted to $ 62.8 million, based on the closing price of $ 79.74 of the Company’s common stock and cash paid for fractional shares on October 1, 2022. The Company accounted for the merger using the acquisition method pursuant to ASC Topic 805, “Business Combinations.” and recorded total assets of $ 428.7 million, including $ 12.6 million in goodwill, and assumed total liabilities of $ 378.5 million.

Cash and Cash Equivalents

Cash and Cash Equivalents	12 Months Ended
Cash and Cash Equivalents	Dec. 31, 2023
Cash and Cash Equivalents [Abstract]
Cash and Cash Equivalents	5. CASH AND CASH EQUIVALENTS At December 31, 2023 and December 31, 2022, cash and cash equivalents totaled $ 33.0 million and $ 30.7 million , respectively. There were no amounts required to be maintained at the Federal Reserve Bank of Boston (“FRB of Boston”) at December 31, 2023 and December 31, 2022. At December 31, 2023 and December 31, 2022 , the Company pledged $ 500,000 to the New Hampshire Banking Department relating to Cambridge Trust Company of New Hampshire, Inc.’s operations in that state. The Company did no t have any cash pledged as collateral to derivative counterparties at December 31, 2023 or at December 31, 2022. See Note 21 - Derivatives and Hedging Activities for a discussion of the Company’s derivative and hedging activities .

Investment Securities

Investment Securities	12 Months Ended
Investment Securities	Dec. 31, 2023
Investments, Debt and Equity Securities [Abstract]
Investment Securities	6. INVESTMENT SECURITIES Investment securities have been classified in the accompanying consolidated balance sheets according to management’s intent. The carrying amounts of securities and their approximate fair values were as follows: December 31, 2023 December 31, 2022 Amortized Gross Gross Fair Amortized Gross Gross Fair (dollars in thousands) Available for sale securities U.S. Government Sponsored $ 22,998 $ — $ ( 2,536 ) $ 20,462 $ 22,997 $ — $ ( 3,264 ) $ 19,733 Mortgage-backed securities 140,378 4 ( 23,006 ) 117,376 158,034 3 ( 25,354 ) 132,683 Corporate debt securities — — — — 996 4 — 1,000 Total available for sale securities $ 163,376 $ 4 $ ( 25,542 ) $ 137,838 $ 182,027 $ 7 $ ( 28,618 ) $ 153,416 Held to maturity securities U.S. Treasury Notes $ 3,039 $ — $ ( 13 ) $ 3,026 $ 3,970 $ — $ ( 18 ) $ 3,952 Mortgage-backed securities 871,426 17 ( 146,397 ) 725,046 951,372 4 ( 157,208 ) 794,168 Corporate debt securities 250 — ( 2 ) 248 250 — ( 6 ) 244 Municipal securities 84,617 24 ( 7,533 ) 77,108 96,405 88 ( 9,271 ) 87,222 Total held to maturity securities $ 959,332 $ 41 $ ( 153,945 ) $ 805,428 $ 1,051,997 $ 92 $ ( 166,503 ) $ 885,586 Total $ 1,122,708 $ 45 $ ( 179,487 ) $ 943,266 $ 1,234,024 $ 99 $ ( 195,121 ) $ 1,039,002 All of the Company’s mortgage-backed securities have been issued by, or are collateralized by securities issued by, the Government National Mortgage Association (“Ginnie Mae” or “GNMA”), the Federal National Mortgage Association (“Fannie Mae” or “FNMA”), or the Federal Home Loan Mortgage Corporation (“Freddie Mac” or “FHLMC”). The amortized cost and fair value of investment securities, aggregated by the contractual maturity, are shown below. Municipal securities are aggregated by the earliest of call date or contractual maturity. Maturities of mortgage-backed securities do not take into consideration scheduled amortization or prepayments. Actual maturities may differ from contractual maturities because issuers may have the right to call or prepay obligations with or without call or prepayment penalties. December 31, 2023 Within One Year After One, But After Five, But After Ten Years Total Amortized Fair Amortized Fair Amortized Fair Amortized Fair Amortized Fair (dollars in thousands) Available for sale securities U.S. Government Sponsored Enterprise obligations $ — $ — $ 9,998 $ 9,360 $ 5,000 $ 4,506 $ 8,000 $ 6,596 $ 22,998 $ 20,462 Mortgage-backed securities — — 11,466 10,877 37,207 31,611 91,705 74,888 140,378 117,376 Total available for sale securities $ — $ — $ 21,464 $ 20,237 $ 42,207 $ 36,117 $ 99,705 $ 81,484 $ 163,376 $ 137,838 Held to maturity securities U.S. Treasury Notes $ 2,076 $ 2,065 $ 963 $ 961 $ — $ — $ — $ — $ 3,039 $ 3,026 Mortgage-backed securities — — 23,490 22,378 50,094 43,247 797,842 659,421 871,426 725,046 Corporate debt securities 250 248 — — — — — — 250 248 Municipal securities 2,666 2,663 22,397 22,309 22,051 21,620 37,503 30,516 84,617 77,108 Total held to maturity securities $ 4,992 $ 4,976 $ 46,850 $ 45,648 $ 72,145 $ 64,867 $ 835,345 $ 689,937 $ 959,332 $ 805,428 Total $ 4,992 $ 4,976 $ 68,314 $ 65,885 $ 114,352 $ 100,984 $ 935,050 $ 771,421 $ 1,122,708 $ 943,266 The following tables show the Company’s investment securities with gross unrealized losses, for which an allowance for credit losses has not been recorded at December 31, 2023 or at December 31, 2022, aggregated by investment category and length of time that individual investment securities have been in a continuous loss position: December 31, 2023 Less than 12 months 12 months or longer Total Fair Unrealized Fair Unrealized Fair Unrealized (dollars in thousands) Available for sale securities U.S. Government Sponsored Enterprise $ — $ — $ 20,462 $ ( 2,536 ) $ 20,462 $ ( 2,536 ) Mortgage-backed securities 79 ( 1 ) 113,478 ( 23,005 ) 113,557 ( 23,006 ) Total available for sale securities $ 79 $ ( 1 ) $ 133,940 $ ( 25,541 ) $ 134,019 $ ( 25,542 ) Held to maturity securities U.S. Treasury Notes $ 961 $ ( 2 ) $ 2,065 $ ( 11 ) $ 3,026 $ ( 13 ) Mortgage-backed securities — — 723,042 ( 146,397 ) 723,042 ( 146,397 ) Corporate debt securities — — 248 ( 2 ) 248 ( 2 ) Municipal securities 17,401 ( 79 ) 44,548 ( 7,454 ) 61,949 ( 7,533 ) Total held to maturity securities $ 18,362 $ ( 81 ) $ 769,903 $ ( 153,864 ) $ 788,265 $ ( 153,945 ) Total $ 18,441 $ ( 82 ) $ 903,843 $ ( 179,405 ) $ 922,284 $ ( 179,487 ) December 31, 2022 Less than 12 months 12 months or longer Total Fair Unrealized Fair Unrealized Fair Unrealized (dollars in thousands) Available for sale securities U.S. Government Sponsored Enterprise $ 10,722 $ ( 2,278 ) $ 9,012 $ ( 986 ) $ 19,734 $ ( 3,264 ) Mortgage-backed securities 41,832 ( 3,097 ) 90,545 ( 22,257 ) 132,377 ( 25,354 ) Total available for sale securities $ 52,554 $ ( 5,375 ) $ 99,557 $ ( 23,243 ) $ 152,111 $ ( 28,618 ) Held to maturity securities U.S. Treasury Notes $ 3,952 $ ( 18 ) $ — $ — $ 3,952 $ ( 18 ) Mortgage-backed securities 230,708 ( 22,362 ) 562,835 ( 134,846 ) 793,543 ( 157,208 ) Corporate debt securities 243 ( 6 ) — — 243 ( 6 ) Municipal securities 51,969 ( 4,388 ) 13,714 ( 4,883 ) 65,683 ( 9,271 ) Total held to maturity securities $ 286,872 $ ( 26,774 ) $ 576,549 $ ( 139,729 ) $ 863,421 $ ( 166,503 ) Total $ 339,426 $ ( 32,149 ) $ 676,106 $ ( 162,972 ) $ 1,015,532 $ ( 195,121 ) As of December 31, 2023 , 415 debt securities had gross unrealized losses, with an aggregate depreciation of 16.3 % from the Company’s amortized cost basis. The largest unrealized dollar loss of any single security was $ 1.9 million, or 22.2 % of its amortized cost. The largest unrealized loss percentage of any single security was 36.6 % of its amortized cost, or $ 855,000 . The Company believes that the nature and duration of unrealized losses on its debt security positions are primarily a function of interest rate movements and changes in investment spreads and does not consider full repayment of principal on the reported debt obligations to be at risk. Since nearly all of these securities are rated “investment grade” and (a) the Company does not intend to sell these securities before recovery and (b) it is more likely than not that the Company will not be required to sell these securities before recovery, the Company does not expect to suffer a credit loss as of December 31, 2023. There were no investment securities pledged as collateral for repurchase agreements at December 31, 2023. The following table sets forth information regarding sales of investment securities and the resulting gains or losses from such sales: For the Year Ended December 31, 2023 2022 2021 (dollars in thousands) Amortized cost of securities sold $ — $ 19,018 $ — Gross gains realized on securities sold — — — Gross losses realized on securities sold — — — Net proceeds from securities sold $ — $ 19,018 $ — The Company monitors the credit quality of certain debt securities through the use of credit rating among other factors on a quarterly basis. Credit ratings are opinions about the credit quality of a security and are utilized by the Company to make informed decisions. Investment grade securities are rated BBB-/Baa3 or higher and are generally considered to be of low risk. At December 31, 2023 and 2022 respectively, the Company’s debt securities portfolio did not contain any securities below investment grade, as reported by major credit rating agencies. At December 31, 2023 and 2022, respectively, none of the Company's investment securities were delinquent or in non-accrual status . The following tables summarize the credit rating of the Company’s debt securities portfolio at December 31, 2023 and December 31, 2022. December 31, 2023 Mortgage-backed Securities (1) Corporate Debt Securities Municipal Securities U.S. GSE Obligations U.S. Treasury Notes Total (dollars in thousands) Available for sale securities, at fair value AAA/AA/A $ 117,376 $ — $ — $ 20,462 $ — $ 137,838 Total available for sale securities $ 117,376 $ — $ — $ 20,462 $ — $ 137,838 Held to maturity securities, at amortized cost AAA/AA/A $ 871,426 $ 250 $ 84,617 $ — $ 3,039 $ 959,332 Total held to maturity securities $ 871,426 $ 250 $ 84,617 $ — $ 3,039 $ 959,332 December 31, 2022 Mortgage-backed Securities (1) Corporate Debt Securities Municipal Securities U.S. GSE Obligations U.S. Treasury Notes Total (dollars in thousands) Available for sale securities, at fair value AAA/AA/A $ 132,683 $ — $ — $ 19,733 $ — $ 152,416 BBB/BB/B — 1,000 — — — 1,000 Total available for sale securities $ 132,683 $ 1,000 $ — $ 19,733 $ — $ 153,416 Held to maturity securities, at amortized cost AAA/AA/A $ 951,372 $ 250 $ 96,405 $ — $ 3,970 $ 1,051,997 Total held to maturity securities $ 951,372 $ 250 $ 96,405 $ — $ 3,970 $ 1,051,997 Includes Agency mortgage-backed pass-through securities and collateralized mortgage obligations issued by U.S. Government Sponsored Enterprises (“GSEs”) and U.S. government agencies, such as FNMA, FHLMC, and GNMA that are not rated by Moody’s or Standard & Poor's. Each security contains a guarantee by the issuing GSE or agency and therefore carries an implicit guarantee of the U.S. government. These have been categorized as AAA/AA/A.

Loans and the Allowance for Cre

Loans and the Allowance for Credit Losses	12 Months Ended
Loans and the Allowance for Credit Losses	Dec. 31, 2023
Receivables [Abstract]
Loans and the Allowance for Credit Losses	7. LOANS AND THE ALLOWANCE FOR CREDIT LOSSES Loans outstanding are detailed by category as follows: December 31, 2023 December 31, 2022 (dollars in thousands) Residential mortgage Mortgages - fixed rate $ 813,374 $ 902,968 Mortgages - adjustable rate 760,632 703,958 Construction 45,863 35,299 Deferred costs, net of unearned fees 6,395 6,613 Total residential mortgages 1,626,264 1,648,838 Commercial mortgage Mortgages - non-owner occupied 1,648,408 1,592,732 Mortgages - owner occupied 167,522 183,591 Construction 113,133 135,782 Deferred costs, net of unearned fees 2,410 2,318 Total commercial mortgages 1,931,473 1,914,423 Home equity Home equity - lines of credit 92,730 108,961 Home equity - term loans 2,679 2,098 Deferred costs, net of unearned fees 240 292 Total home equity 95,649 111,351 Commercial and industrial Commercial and industrial 342,475 349,026 Paycheck Protection Program loans 653 1,384 Unearned fees, net of deferred costs 583 240 Total commercial and industrial 343,711 350,650 Consumer Secured 22,592 35,679 Unsecured 1,822 1,897 Deferred costs, net of unearned fees 33 18 Total consumer 24,447 37,594 Total loans $ 4,021,544 $ 4,062,856 Directors and officers of the Company and their associates are clients of, and have other transactions with, the Company in the normal course of business. All loans and commitments included in such transactions were made on substantially the same terms, including interest rates and collateral, as those prevailing at the time for comparable transactions with other persons and do not involve more than normal risk of collection or present other unfavorable features. Asset Quality The Company’s philosophy toward managing its loan portfolios is predicated upon careful monitoring, which stresses early detection and response to delinquent and default situations. The Company seeks to make arrangements to resolve any delinquent or default situation over the shortest possible time frame. As a general rule, loans more than 90 days past due with respect to principal or interest are classified as non-accrual loans. The Company may use discretion regarding other loans over 90 days past due if the loan is well secured and/or in process of collection. The following tables set forth information regarding non-performing loans disaggregated by loan category: December 31, 2023 Residential Commercial Home Commercial and Total (dollars in thousands) Non-performing loans: Non-accrual loans $ 6,412 $ 9,758 $ 285 $ 61 $ 16,516 Loans past due >90 days, but still accruing — — — 51 51 Total $ 6,412 $ 9,758 $ 285 $ 112 $ 16,567 December 31, 2022 Residential Commercial Home Commercial and Total (dollars in thousands) Non-performing loans: Non-accrual loans $ 4,733 $ 311 $ 722 $ 73 $ 5,839 Troubled debt restructurings 622 — — 81 $ 703 Total $ 5,355 $ 311 $ 722 $ 154 $ 6,542 It is the Company’s policy to reverse any accrued interest when a loan is put on non-accrual status and, generally, to record any payments received from a borrower related to a loan on non-accrual status as a reduction of the amortized cost basis of the loan. The Company did not record any interest income on non-accrual loans during the years ended December 31, 2023 and December 31, 2022. Accrued interest reversed against interest income for the year ended December 31, 2023 and December 31, 2022 was immaterial. There were no significant commitments to lend additional funds to borrowers whose loans were on non-accrual status at December 31, 2023 and December 31, 2022. A financial asset is considered collateral-dependent when the debtor is experiencing financial difficulty and repayment is expected to be provided substantially through the sale or operation of the collateral. Expected credit losses for collateral-dependent loans are based on the fair value of the collateral at the reporting date, adjusted for selling costs as appropriate. The following table presents the amortized costs basis and related reserve amount of individually analyzed collateral-dependent loans by portfolio segment. For the Year Ended December 31, 2023 2022 Amortized Cost Basis Reserve Amount Amortized Cost Basis Reserve Amount (dollars in thousands) Commercial mortgage $ 9,611 $ 2,345 $ - $ - Commercial & Industrial 64 43 103 82 Total $ 9,675 $ 2,388 $ 103 $ 82 Loan Modifications Pursuant to ASU 2022-02, the Company evaluates all loan restructurings according to the accounting guidance for loan modifications to determine if the restructuring results in a new loan or a continuation of the existing loan. An assessment of whether a borrower is experiencing financial difficulty is made at the time of a modification. Loan modifications to borrowers experiencing financial difficulty that result in a change in the timing or amount of contractual cash flows include situations where there is principal forgiveness, interest rate reductions, other-than-insignificant payment delays, term extensions, and combinations of the listed modifications. Therefore, the disclosures related to loan restructurings are only for modifications that directly affect cash flows. For the year ended December 31, 2023, the Company made no loan modifications to borrower’s experiencing financial difficulty. Troubled Debt Restructurings (“TDRs”) Prior to the adoption of ASU 2022-02, loans were considered restructured in a troubled debt restructuring when the Company granted concessions to a borrower due to the borrower’s financial condition that it otherwise would not have considered. These concessions may have include modifications of the terms of the debt such as deferral of payments, extension of maturity, reduction of principal balance, reduction of the stated interest rate other than normal market rate adjustments, or a combination of these concessions. Restructured loans were classified as accruing or non-accruing based on management’s assessment of the collectability of the loan. Loans which were already on non-accrual status at the time of the restructuring generally remained on non-accrual status for approximately six months or longer before management considered such loans for return to accruing status. Accruing restructured loans were placed into non-accrual status if and when the borrower failed to comply with the restructured terms and management deemed it unlikely that the borrower will return to a status of compliance in the near term. TDRs were individually evaluated for credit losses. There were no new TDRs during the year ended December 31, 2022. As of December 31, 2022 , four loans were TDRs with a total carrying value of $ 704,000 . There were no TDR defaults during the year ended December 31, 2022. As of December 31, 2023 and December 31, 2022 , there were no significant commitments to lend additional funds to borrowers whose loans were restructured. Pursuant to Section 4013 of the CARES Act, financial institutions could suspend the requirements under U.S. GAAP related to TDRs for modifications made before December 31, 2020 to loans that were current as of December 31, 2019. As a result of the enactment of the Consolidated Appropriations Act, 2021, in January 2021, the suspension of TDR accounting was extended to, and expired on January 1, 2022. The requirement that a loan be not more than 30 days past due as of December 31, 2019 was still applicable. In response to the COVID-19 pandemic and its economic impact to clients, a short-term modification program that complied with the CARES Act was implemented to provide temporary payment relief to those borrowers directly impacted by COVID-19. The deferred payments along with interest accrued during the deferral period are due and payable on the maturity date. Under issued guidance, provided that these loans were current as of either year end or the date of the modification, these loans were not considered TDR loans at December 31, 2023 and will not be reported as past due during the deferral period. The Company had no loans in deferral as of December 31, 2023. Foreclosure proceedings As of December 31, 2023 , there were two loans in process of foreclosure with a carrying value of approximately $ 1.5 million. Both of these loans are secured by one to four family residential property. As of December 31, 2022, there were no loans in process of foreclosure. Loans by Credit Quality Indicator With respect to residential real estate mortgages, home equity, and consumer loans, the Company utilizes the following categories as indicators of credit quality: • Performing – These loans are accruing and are considered having low to moderate risk. • Non-performing – These loans are on non-accrual or are past due more than 90 days but are still accruing or are restructured. These loans may contain greater than average risk. With respect to commercial real estate mortgages and commercial loans, the Company utilizes a 10-grade internal loan rating system as an indicator of credit quality. The grades are as follows: • Loans rated 1-6 (Pass) – These loans are considered “pass” rated with low to moderate risk. • Loans rated 7 (Special Mention) – These loans have potential weaknesses warranting close attention, which, if left uncorrected, may result in deterioration of the credit at some future date. • Loans rated 8 (Substandard) – These loans have well-defined weaknesses that jeopardize the orderly liquidation of the debt under the original loan terms. Loss potential exists but is not identifiable in any one client. • Loans rated 9 (Doubtful) – These loans have pronounced weaknesses that make full collection highly questionable and improbable. • Loans rated 10 (Loss) – These loans are considered uncollectible and continuance as a bankable asset is not warranted. The following tables contain period-end balances of loans receivable disaggregated by credit quality indicator: Credit Quality Indicator - by Origination Year as of December 31, 2023 2023 2022 2021 2020 2019 Prior Revolving loans amortized cost basis Total (dollars in thousands) Residential Mortgage: Current $ 92,911 $ 331,817 $ 507,677 $ 274,988 $ 111,715 $ 300,744 $ — $ 1,619,852 Non-performing 193 1,490 4,729 — 6,412 Total $ 92,911 $ 331,817 $ 507,677 $ 275,181 $ 113,205 $ 305,473 $ — $ 1,626,264 Current-period gross write-offs $ — $ — $ — $ — $ — $ — $ — $ — Home equity: Current $ 8,085 $ 2,411 $ 2,241 $ 1,399 $ 2,587 $ 14,674 $ 63,967 $ 95,364 Non-performing 58 227 — 285 Total $ 8,085 $ 2,469 $ 2,241 $ 1,399 $ 2,587 $ 14,901 $ 63,967 $ 95,649 Current-period gross write-offs $ — $ — $ — $ — $ — $ — $ — $ — Consumer: Current $ 7,281 $ 7,459 $ 1,706 $ 2,841 $ 694 $ 3,842 $ 624 $ 24,447 Non-performing — — — — — — — — Total $ 7,281 $ 7,459 $ 1,706 $ 2,841 $ 694 $ 3,842 $ 624 $ 24,447 Current-period gross write-offs $ — $ — $ — $ — $ — $ 67 $ — $ 67 Credit Quality Indicator - by Origination Year as of December 31, 2023 2023 2022 2021 2020 2019 Prior Revolving loans amortized cost basis Total (dollars in thousands) Commercial Mortgage: Credit risk profile by internally assigned grade: 1-6 (Pass) $ 69,636 $ 466,760 $ 360,331 $ 226,994 $ 258,296 $ 459,472 $ — $ 1,841,489 7 (Special Mention) 1,826 1,822 — 1,507 48,470 25,493 — 79,118 8 (Substandard) — 1,096 — — — 9,770 — 10,866 9 (Doubtful) — — — — — — — — 10 (Loss) — — — — — — — — Total $ 71,462 $ 469,678 $ 360,331 $ 228,501 $ 306,766 $ 494,735 $ — $ 1,931,473 Current-period gross write-offs $ — $ — $ — $ — $ — $ — $ — $ — Commercial and Industrial: Credit risk profile by internally assigned grade: 1-6 (Pass) $ 43,388 $ 107,494 $ 46,678 $ 50,660 $ 22,325 $ 40,647 $ 436 $ 311,628 7 (Special Mention) 60 25,057 92 3,467 2 121 10 28,809 8 (Substandard) — 1,321 — 256 1,575 122 — 3,274 9 (Doubtful) — — — — — — — — 10 (Loss) — — — — — — — — Total $ 43,448 $ 133,872 $ 46,770 $ 54,383 $ 23,902 $ 40,890 $ 446 $ 343,711 Current-period gross write-offs $ — $ — $ — $ — $ — $ 62 $ — $ 62 Credit Quality Indicator - by Origination Year as of December 31, 2022 2022 2021 2020 2019 2018 Prior Revolving loans amortized cost basis Total (dollars in thousands) Residential Mortgage: Current $ 339,634 $ 531,147 $ 294,370 $ 119,414 $ 84,215 $ 274,703 $ — $ 1,643,483 Non-performing — — 206 315 684 4,150 — 5,355 Total $ 339,634 $ 531,147 $ 294,576 $ 119,729 $ 84,899 $ 278,853 $ — $ 1,648,838 Home equity: Current $ 5,291 $ 2,958 $ 1,349 $ 1,541 $ 867 $ 479 $ 98,144 $ 110,629 Non-performing — — — — — — 722 722 Total $ 5,291 $ 2,958 $ 1,349 $ 1,541 $ 867 $ 479 $ 98,866 $ 111,351 Consumer: Current $ 13,263 $ 8,573 $ 5,602 $ 836 $ 2,092 $ 6,631 $ 597 $ 37,594 Non-performing — — — — — — — — Total $ 13,263 $ 8,573 $ 5,602 $ 836 $ 2,092 $ 6,631 $ 597 $ 37,594 Credit Quality Indicator - by Origination Year as of December 31, 2022 2022 2021 2020 2019 2018 Prior Revolving loans amortized cost basis Total (dollars in thousands) Commercial Mortgage: Credit risk profile by internally 1-6 (Pass) $ 448,919 $ 366,414 $ 240,023 $ 269,899 $ 131,415 $ 383,473 $ — $ 1,840,143 7 (Special Mention) — — 4,562 41,578 21,697 6,132 — 73,969 8 (Substandard) — — — — — 311 — 311 9 (Doubtful) — — — — — — — — 10 (Loss) — — — — — — — — Total $ 448,919 $ 366,414 $ 244,585 $ 311,477 $ 153,112 $ 389,916 $ — $ 1,914,423 Commercial and Industrial: Credit risk profile by internally 1-6 (Pass) $ 130,418 $ 69,030 $ 65,390 $ 29,543 $ 20,549 $ 27,310 $ 475 $ 342,715 7 (Special Mention) — 4,211 130 161 407 121 10 5,040 8 (Substandard) — — 628 2,102 81 84 — 2,895 9 (Doubtful) — — — — — — — — 10 (Loss) — — — — — — — — Total $ 130,418 $ 73,241 $ 66,148 $ 31,806 $ 21,037 $ 27,515 $ 485 $ 350,650 Loans origination dates in the tables above reflect the original date, or the date of a material modification of a previously originated loan, for both organic originations and acquired loans. Delinquencies The past due status of a loan is determined in accordance with its contractual repayment terms. All loan types are reported past due when one scheduled payment is due and unpaid for 30 days or more. Loan delinquencies can be attributed to many factors, such as but not limited to, a continuing weakness in, or deteriorating, economic conditions in the region in which the collateral is located, the loss of a tenant or lower lease rates for commercial borrowers, or the loss of income for consumers and the resulting liquidity impacts on the borrowers. The following tables contain period-end balances of loans receivable disaggregated by past due status: December 31, 2023 30-59 Days 60-89 Days 90 Days or Greater Total Current Total (dollars in thousands) Residential mortgage $ 16,768 $ 1,234 $ 2,548 $ 20,550 $ 1,605,714 $ 1,626,264 Commercial mortgage 1,885 — — 1,885 1,929,588 1,931,473 Home equity 1,855 171 — 2,026 93,623 95,649 Commercial and industrial 1,477 301 58 1,836 341,875 343,711 Consumer 251 14 — 265 24,182 24,447 Total $ 22,236 $ 1,720 $ 2,606 $ 26,562 $ 3,994,982 $ 4,021,544 December 31, 2022 30-59 Days 60-89 Days 90 Days Total Current Total (dollars in thousands) Residential mortgage $ 11,359 $ 1,454 $ 1,809 $ 14,622 $ 1,634,216 $ 1,648,838 Commercial mortgage — — — — 1,914,423 1,914,423 Home equity 962 393 214 1,569 109,782 111,351 Commercial and industrial 65 269 — 334 350,316 350,650 Consumer 81 — — 81 37,513 37,594 Total $ 12,467 $ 2,116 $ 2,023 $ 16,606 $ 4,046,250 $ 4,062,856 There were two loans 90 days or more past due and still accruing at December 31, 2023 totaling $ 51,000 . There were no significant commitments to lend additional funds to borrowers whose loans were on non-accrual status at December 31, 2023 and December 31, 2022. Allowance for Credit Losses The following tables contain changes in the allowance for credit losses disaggregated by loan category: For The Year Ended December 31, 2023 Residential Commercial Home Commercial & Consumer Unfunded Commitments Total (dollars in thousands) Allowance for credit loss: Allowance for credit losses - loan Balance at December 31, 2022 $ 13,321 $ 19,086 $ 573 $ 4,153 $ 641 $ — $ 37,774 Charge-offs — — — ( 62 ) ( 67 ) — ( 129 ) Recoveries — — — 37 22 — 59 Provision for (release of) credit ( 4,922 ) 5,366 7 812 ( 23 ) — 1,240 Allowance for credit losses - loan portfolio $ 8,399 $ 24,452 $ 580 $ 4,940 $ 573 $ — $ 38,944 Allowance for credit losses - Balance at December 31, 2022 $ — $ — $ — $ — $ — $ 2,096 $ 2,096 Provision for (release of) credit — — — — — ( 336 ) ( 336 ) Allowance for credit losses- $ — $ — $ — $ — $ — $ 1,760 $ 1,760 Total allowance for credit loss $ 8,399 $ 24,452 $ 580 $ 4,940 $ 573 $ 1,760 $ 40,704 For The Year Ended December 30, 2022 Residential Commercial Home Commercial & Consumer Unfunded Commitments Total (dollars in thousands) Allowance for credit loss: Allowance for credit losses - loan Balance at December 31, 2021 $ 13,383 $ 17,133 $ 406 $ 2,989 $ 585 $ — $ 34,496 Provision for acquired loans 527 1,337 117 113 8 — 2,102 Initial allowance for PCD 19 37 — — — — 56 Charge-offs — — — ( 23 ) ( 29 ) — ( 52 ) Recoveries 4 — — 89 12 — 105 Provision for (release of) credit ( 612 ) 579 50 985 65 — 1,067 Allowance for credit losses - loan portfolio $ 13,321 $ 19,086 $ 573 $ 4,153 $ 641 $ — $ 37,774 Allowance for credit losses - Balance at December 31, 2021 $ — $ — $ — $ — $ — $ 1,384 $ 1,384 Acquired loan commitments — — — — — 137 137 Provision for credit — — — — — 575 575 Allowance for credit losses- — — — — — 2,096 2,096 Total allowance for credit loss $ 13,321 $ 19,086 $ 573 $ 4,153 $ 641 $ 2,096 $ 39,870 Balances of accrued interest receivable excluded from amortized cost and the calculation of allowance for credit losses amounted to $ 13.5 million, $ 11.6 million, and $ 6.8 million at December 31, 2023, December 31, 2022, and December 31, 2021, respectively.

Federal Home Loan Bank ("FHLB")

Federal Home Loan Bank ("FHLB") of Boston Stock	12 Months Ended
Federal Home Loan Bank ("FHLB") of Boston Stock	Dec. 31, 2023
Federal Home Loan Bank ("FHLB") of Boston
Federal Home Loan Bank ("FHLB") Stock [Line Items]
Federal Home Loan Bank ("FHLB") of Boston Stock	8. FEDERAL HOME LOAN BANK (“FHLB”) OF BOSTON STOCK As a voluntary member of the FHLB of Boston, the Company is required to invest in stock of the FHLB of Boston (which is considered a restricted equity security) in an amount based upon its outstanding advances from the FHLB of Boston. At December 31, 2023 and 2022, the Company’s investment in FHLB of Boston stock totaled $ 19.1 million and $ 6.3 million , respectively. No market exists for shares of this stock. The Company’s cost for FHLB of Boston stock is equal to its par value. Upon redemption of the stock, which is at the discretion of the FHLB of Boston, the Bank would receive an amount equal to the par value of the stock. At its discretion, the FHLB of Boston may also declare dividends on its stock. The Company’s investment in FHLB of Boston stock is reviewed for impairment at each reporting date based on the ultimate recoverability of the cost basis of the stock. As of December 31, 2023 and December 31, 2022, no impairment has been recognized.

Banking Premises and Equipment

Banking Premises and Equipment	12 Months Ended
Banking Premises and Equipment	Dec. 31, 2023
Property, Plant and Equipment [Abstract]
Banking Premises and Equipment	9. BANKING PREMISES AND EQUIPMENT A summary of the cost and accumulated depreciation and amortization of property, leasehold improvements, and equipment is presented below: December 31, Estimated 2023 2022 Useful Lives (dollars in thousands) Land $ 3,396 $ 3,396 Building and leasehold improvements 25,586 25,588 3 - 30 years Equipment, including vaults 21,460 20,165 3 - 20 years Work in process 149 22 Subtotal 50,591 49,171 Accumulated depreciation and amortization ( 28,838 ) ( 25,874 ) Total $ 21,753 $ 23,297 Total depreciation expense for the years ended December 31, 2023, 2022 , and 2021 amounted to $ 2.8 million, $ 2.7 million, and $ 2.6 million, and is included in occupancy and equipment expenses in the accompanying consolidated statements of income.

Intangible Assets

Intangible Assets	12 Months Ended
Intangible Assets	Dec. 31, 2023
Goodwill and Intangible Assets Disclosure [Abstract]
Intangible Assets	10. INTANGIBLE ASSETS Core deposit intangible (“CDI”) . At December 31, 2023 and December 31, 2022, the carrying value of CDI assets totaled $ 6.5 million and $ 7.4 million, respectively. The Company recorded a mortization expense of CDI assets totaling $ 893,000 , $ 494,000 , and $ 361,000 for the years ended December 31, 2023 , December 31, 2022, and December 31, 2021, respectively. The weighted-average remaining amortization period for CDI was 7.7 years and 8.7 years at December 31, 2023 and December 31, 2022, respectively. Mortgage servicing rights. Periodically, the Company sells certain residential mortgage loans to the secondary market. Generally, these loans are sold without recourse or other credit enhancements. The Company sells loans and either releases or retains the servicing rights. For loans sold with servicing rights retained, the Company provides the servicing for the loans on a per-loan fee basis. The Company was servicing mortgage loans sold to others without recourse of approxi mately $ 173.9 million a t December 31, 2023 and $ 191.9 million at December 31, 2022 . Mortgage loans sold with servicing rights retained during the years ended December 31, 2023, December 31, 2022 , and December 31, 2021 were $ 6.4 million, $ 5.8 million, and $ 25.3 million, respectively. The following table provides an analysis of mortgage servicing rights, which are included in other assets: Mortgage Valuation Total (dollars in thousands) Balance at December 31, 2020 $ 1,361 $ ( 142 ) $ 1,219 Mortgage servicing rights capitalized 281 — 281 Amortization charged against servicing income ( 559 ) — ( 559 ) Change in impairment reserve — 142 142 Balance at December 31, 2021 $ 1,083 $ — $ 1,083 Balance at December 31, 2021 $ 1,083 $ — $ 1,083 Mortgage servicing rights acquired as a result of the Northmark merger 785 — 785 Mortgage servicing rights capitalized 71 — 71 Amortization charged against servicing income ( 274 ) — ( 274 ) Balance at December 31, 2022 $ 1,665 $ — $ 1,665 Balance at December 31, 2022 $ 1,665 $ — $ 1,665 Mortgage servicing rights capitalized 74 — 74 Amortization charged against servicing income ( 269 ) — ( 269 ) Balance at December 31, 2023 $ 1,470 $ — $ 1,470 The fair value of the Company’s mortgage servicing rights portfolio was $ 2.4 million and $ 2.3 million as of December 31, 2023 and 2022, respectively. The fair value of mortgage servicing rights is estimated based on the present value of expected cash flows, incorporating assumptions for discount rate, prepayment speed, and servicing cost. The weighted-average amortization period for mortgage servicing rights portfolio was 7.8 years and 7.1 years at December 31, 2023 and 2022, respectively. The estimated aggregate future amortization expense for mortgage servicing rights for each of the next five years and thereafter is as follows: Future Amortization Expense (dollars in thousands) 2024 $ 173 2025 153 2026 136 2027 121 2028 109 Thereafter 778 Total $ 1,470

Deposits

Deposits	12 Months Ended
Deposits	Dec. 31, 2023
Deposits [Abstract]
Deposit	11. DEPOSITS Deposits are summarized as follows: December 31, 2023 December 31, 2022 (dollars in thousands) Demand deposits (non-interest bearing) $ 1,032,413 $ 1,366,395 Interest bearing checking 1,132,518 908,961 Money market 983,480 1,162,773 Savings 498,386 790,628 Retail certificates of deposit under $250,000 212,694 117,532 Retail certificates of deposit $250,000 or greater 170,020 87,528 Brokered certificates of deposit 291,667 381,559 Total deposits $ 4,321,178 $ 4,815,376 Certificates of deposit had the following schedule of maturities: December 31, 2023 December 31, 2022 (dollars in thousands) 2023 $ — $ 533,513 2024 655,266 39,753 2025 11,388 5,377 2026 5,918 6,021 2027 1,315 1,955 2028 and after 494 — Total certificates of deposit $ 674,381 $ 586,619 Related Party Deposits Deposit accounts of directors, executive officers, and their respective affiliates tot aled $ 1.7 million an d $ 2.7 million as of December 31, 2023 and 2022 , respectively.

Borrowings

Borrowings	12 Months Ended
Borrowings	Dec. 31, 2023
Debt Disclosure [Abstract]
Borrowings	12. BORROWINGS Federal Home Loan Bank Advances At December 31, 2023 the Company had $ 406.0 million of short-term advances from the FHLB of Boston, with a weighted average rate of 5.38 %. For the year ended December 31, 2023 the average daily balance for short-term advances was $ 157.1 million and the highest month end balance was $ 406.0 million. At December 31, 2022 , the Company had $ 100.2 million of short-term advances from the FHLB of Boston, with a weighted average rate of 4.38 %. For the year ended December 31, 2022 the average daily balance for short-term advances was $ 68.4 million and the highest month end balance was $ 279.0 million. At December 31, 2023 the Company had $ 46.2 million of long-term advances from the FHLB of Boston, with a weighted average rate of 4.17 %. At December 31, 2022 , the Company had no long-term advances from the FHLB of Boston. Information relating to the Company’s borrowings, their remaining maturities, and weighted average interest rates are presented below: For the Year Ended December 31, 2023 2022 Amount Weighted Average Interest Rate Amount Weighted Average Interest Rate (dollars in thousands) Within one year $ 406,000 5.38 % $ 100,176 4.38 % Over one year to three years 45,000 4.27 % — — % Over three years to five years (1) 717 — % — — % Over five years (1) 438 — % — — % Total FHLB of Boston $ 452,155 5.26 % $ 100,176 4.38 % (1) Includes advances under the FHLB of Boston Jobs for New England (“JNE”) program, which are zero rate borrowings. Securities Sold Under Agreements to Repurchase The Company periodically enters into repurchase agreements with its larger deposit and commercial clients as part of its cash management services which are typically overnight borrowings. There were no repurchase agreements with clients outstanding as of December 31, 2023. Repurchase agreements with clients totaled $ 5.0 million as of December 31, 2022. The daily average balance of securities sold under agreements to repurchase during the year ended December 31, 2023 was $ 1.7 million and during the year ended December 31, 2022 was $ 1.2 million. The Company retained control of the securities underlying these agreements. Unused Borrowing Capacity with the FHLB of Boston and FRB of Boston All short- and long-term borrowings with the FHLB of Boston are secured by the Company’s stock in the FHLB of Boston and a blanket lien on “qualified collateral” defined principally as 60 % - 70 % of the carrying value of certain residential mortgage loans. Based upon collateral pledged, the Bank’s unused borrowing capacity with the FHLB of Boston at December 31, 2023 was approximately $ 532.0 million. The Company also has a line of credit with the FRB of Boston. The Company did no t have any outstanding FRB borrowings at December 31, 2023 or December 31, 2022. At December 31, 2023 and December 31, 2022, the Company had pledged investment securities, CRE, and home equity loans with aggregate principal balances of approximate ly $ 2.11 billion and $ 970.1 million, respectively, as collateral for this line of credit. Based upon the collateral pledged, the Company’s unused borrowing capacity with the FRB of Boston at December 31, 2023 and 2022 was approximately $ 1.76 billion and $ 680.4 million, respectively.

Income Taxes

Income Taxes	12 Months Ended
Income Taxes	Dec. 31, 2023
Income Tax Disclosure [Abstract]
Income Taxes	13. INCOME TAXES The components of income tax expense were as follows: For the Year Ended December 31, 2023 2022 2021 (dollars in thousands) Current income tax expense Federal $ 7,740 $ 12,906 $ 11,330 State 2,895 5,559 4,862 Total current income tax expense 10,635 18,465 16,192 Deferred income tax expense Federal 1,091 455 1,840 State 574 132 1,059 Total deferred income tax expense 1,665 587 2,899 Total income tax expense $ 12,300 $ 19,052 $ 19,091 The following is a reconciliation of the total income tax expense, calculated at statutory federal income tax rates, to the income tax provision in the consolidated statements of income: For the Year Ended December 31, 2023 2022 2021 (dollars in thousands) Income tax expense at statutory rate of 21.0 % $ 9,746 $ 15,112 $ 15,354 Increase/(decrease) resulting from: State tax, net of federal tax benefit 2,741 4,496 4,678 Tax-exempt income ( 597 ) ( 814 ) ( 795 ) ESOP dividends ( 151 ) ( 150 ) ( 145 ) Bank owned life insurance ( 148 ) ( 133 ) ( 165 ) Compensation limited under 162(m) 112 193 226 Benefit from stock compensation 17 ( 81 ) ( 46 ) Non-deductible acquisition costs 657 182 — Non-deductible expenses 71 44 55 BOLI surrender, death benefit — 310 — Other ( 148 ) ( 107 ) ( 71 ) Total income tax expense $ 12,300 $ 19,052 $ 19,091 The Company’s 2023 and 2022 net deferred tax assets were measured using a 27.95 % federal and state blended tax rate, respectively, and consisted of the following components: December 31, 2023 December 31, 2022 (dollars in thousands) Gross deferred tax assets Allowance for credit losses $ 11,377 $ 11,142 Unrealized losses on available for sale securities 6,652 7,390 Incentive compensation 1,379 1,819 Equity based compensation 910 1,298 Lease liabilities 7,033 7,661 ESOP dividends 202 200 Intangibles and fair value marks (merger related) 1,841 2,322 Other 528 931 Total gross deferred tax assets 29,922 32,763 Gross deferred tax liabilities Deferred loan origination costs ( 2,835 ) ( 2,886 ) Retirement benefits ( 2,460 ) ( 1,745 ) Depreciation of premises and equipment ( 2,353 ) ( 2,551 ) Right-of-use asset ( 6,493 ) ( 7,014 ) Mortgage servicing rights ( 411 ) ( 465 ) Goodwill ( 115 ) ( 115 ) Derivative transactions 44 3 Total gross deferred tax liabilities ( 14,623 ) ( 14,773 ) Net deferred tax asset $ 15,299 $ 17,990 It is management’s belief that it is more likely than not that the reversal of deferred tax liabilities and results of future operations will generate sufficient taxable income to realize the deferred tax assets. Therefore, no valuation allowance was required at either December 31, 2023 and December 31, 2022 for the deferred tax assets. It should be noted, however, that factors beyond management’s control, such as the general state of the economy and real estate values, can affect future levels of taxable income and that no assurance can be given that sufficient taxable income will be generated in future periods to fully absorb deductible temporary differences. A summary of the change in the net deferred tax asset is as follows: For the Year Ended December 31, 2023 2022 Balance at beginning of year: $ 17,990 $ 9,985 Deferred tax expense ( 1,665 ) ( 587 ) Merger accounting — 1,853 Accumulated other comprehensive income ( 1,026 ) 6,739 Balance at end of year $ 15,299 $ 17,990 At December 31, 2023 and December 31, 2022 , the Company had no unrecognized tax benefits or any uncertain tax positions. The Company does not expect the total amount of unrecognized tax benefits to significantly increase in the next 12 months. The Company’s federal income tax returns are open and subject to examination from the 2020 through 2023 tax return years. The Company’s state income tax returns are open from the 2020 through 2023 tax return years based on individual states’ statute of limitations.

Pension and Retirement Plans

Pension and Retirement Plans	12 Months Ended
Pension and Retirement Plans	Dec. 31, 2023
Retirement Benefits [Abstract]
Pension and Retirement Plans	14. PENSION AND RETIREMENT PLANS The Company has a noncontributory, defined benefit pension plan (“Pension Plan”) covering substantially all employees hired before May 2, 2011. The Company also provides supplemental retirement benefits to certain current and former executive officers of the Company under the terms of Supplemental Executive Retirement Agreements (“Supplemental Retirement Plan”). The Company also offers postretirement health care benefits for current and future retirees of the Bank. Certain employees receive a fixed monthly benefit at age 65 toward the purchase of postretirement medical coverage. The benefit received is based on the employee’s years of active service. Effective November 7, 2019, the postretirement health care plan was frozen for employees hired after that date. The Company froze the accrual of benefits on the qualified defined benefit pension plan in 2017. The Company did not make any contributions to the qualified defined benefit pension plan during the years ended December 31, 2023 and December 31, 2022. The Company uses a December 31 st measurement date each year to determine the benefit obligations for these plans. Projected benefit obligations and funded status were as follows: Pension Plan Supplemental 2023 2022 2023 2022 (dollars in thousands) Change in projected benefit obligation Obligation at beginning of year $ 35,598 $ 47,875 $ 8,060 $ 10,075 Service cost — — 273 399 Interest cost 1,806 1,309 399 260 Actuarial (gain) loss 1,175 ( 11,754 ) 81 ( 2,057 ) Benefits paid ( 1,937 ) ( 1,832 ) ( 616 ) ( 617 ) Obligation at end of year 36,642 35,598 8,197 8,060 Change in plan assets Fair value at beginning of year 50,349 60,638 — — Actual return on plan assets 5,716 ( 8,457 ) — — Employer contribution — — 616 617 Benefits paid ( 1,937 ) ( 1,832 ) ( 616 ) ( 617 ) Fair value at end of year 54,128 50,349 — — Funded status at end of year $ 17,486 $ 14,751 $ ( 8,197 ) $ ( 8,060 ) The funded status of the Company’s Pension Plan is included within other assets and the funded status of the Company’s Supplemental Retirement Plan is included within other liabilities on the Company’s consolidated balance sheets at December 31, 2023 and 2022. Pension Plan Supplemental 2023 2022 2023 2022 (dollars in thousands) Accumulated benefit obligation $ 36,642 $ 35,598 $ 7,823 $ 7,627 Amounts recognized in accumulated other comprehensive income (loss) consisted of: Pension Plan Supplemental 2023 2022 2023 2022 (dollars in thousands) Net actuarial (gain) loss $ ( 964 ) $ 373 $ ( 535 ) $ ( 617 ) Total $ ( 964 ) $ 373 $ ( 535 ) $ ( 617 ) The components of net periodic benefit cost and amounts recognized in other comprehensive income (loss) were as follows: Pension Plan Supplemental 2023 2022 2023 2022 (dollars in thousands) Net periodic benefit cost Service cost $ — $ — $ 273 $ 399 Interest cost 1,806 1,309 399 260 Expected return on assets ( 3,204 ) ( 3,876 ) — — Amortization of net actuarial loss — — — 28 Net periodic expense (benefit) ( 1,398 ) ( 2,567 ) 672 687 Amounts recognized in other comprehensive income (loss) Net actuarial loss/(gain) ( 1,337 ) 579 81 ( 2,057 ) Amortization of net actuarial loss — — — ( 28 ) Total recognized in other comprehensive income (loss) ( 1,337 ) 579 81 ( 2,085 ) Total recognized in net periodic expense (benefit) and other $ ( 2,735 ) $ ( 1,988 ) $ 753 $ ( 1,398 ) Weighted-average assumptions used to determine projected benefit obligations are as follows: Pension Plan Supplemental 2023 2022 2023 2022 Discount rate 5.00 % 5.22 % 4.95 % 5.15 % Rate of compensation increase N/A N/A 4.00 % 4.00 % Weighted-average assumptions used to determine the net periodic benefit cost in each year were as follows: Pension Plan Supplemental 2023 2022 2023 2022 Discount rate 5.22 % 2.79 % 5.15 % 2.63 % Expected long-term return on plan assets 6.50 % 6.50 % N/A N/A Rate of compensation increase N/A N/A 4.00 % 4.00 % To develop the expected long-term rate of return on assets assumption for the Pension Plan, the Company considered the historical returns and the future expectations for returns for each asset class, as well as target asset allocations of the pension portfolio. The Company maintains an Investment Policy for its Pension Plan. The objective of this policy is to seek a balance between capital appreciation, current income, and preservation of capital. The Investment Policy guidelines suggest that the target asset allocation percentages are from 0 % to 60 % in domestic large cap equities, from 0 % to 20 % in domestic small/mid cap equities, from 0 % to 20 % in international and emerging equities, and from 20 % to 10 0 % in cash and fixed income. The Company’s Pension Plan weighted-average asset allocations by asset category were as follows: December 31, 2023 2022 Equity securities 45 % 60 % Debt securities 20 33 Cash and equivalents 35 7 Total 100 % 100 % The three broad levels of fair values used to measure the Pension Plan assets are as follows: • Level 1 – Quoted prices for identical assets in active markets. • Level 2 – Quoted prices for similar assets in active markets; quoted prices for identical or similar assets in inactive markets; and model-derived valuations in which all significant inputs and significant value drivers are observable in active markets. • Level 3 – Valuations derived from techniques in which one or more significant inputs or significant value drivers are unobservable in the markets and which reflect the Company’s market assumptions. The following table summarizes the various categories of the Pension Plan’s assets: Fair Value as of December 31, 2023 Level 1 Level 2 Level 3 Total (dollars in thousands) Asset category Cash and cash equivalents $ 18,755 $ — $ — $ 18,755 Fixed income — 8,129 — 8,129 Equity securities Mutual funds Domestic equity 15,285 — — 15,285 International 2,798 — — 2,798 Domestic fixed income 9,161 — — 9,161 Total $ 45,999 $ 8,129 $ — $ 54,128 Fair Value as of December 31, 2022 Level 1 Level 2 Level 3 Total (dollars in thousands) Asset category Cash and cash equivalents $ 3,676 $ — $ — $ 3,676 Fixed income — 12,347 — 12,347 Equity securities Mutual funds Domestic equity 24,201 — — 24,201 International 3,942 — — 3,942 Domestic fixed income 6,183 — — 6,183 Total $ 38,002 $ 12,347 $ — $ 50,349 There were no transfers between fair value levels during the years ended December 31, 2023 and December 31, 2022. The Company offers postretirement health care benefits for current and future retirees of the Bank. Employees receive a fixed monthly benefit at age 65 toward the purchase of postretirement medical coverage. The benefit received is based on the employee’s years of active service. The Company uses a December 31 measurement date each year to determine the benefit obligation for this plan. On November 7, 2019, the Company announced its decision to freeze the accrual of benefits to new hires within the plan. The plan is unfunded and plan obligations were $ 489,000 and $ 424,000 at December 31, 2023 and December 31, 2022, respectively. Benefits expected to be paid in the next ten years are as follows: Pension Supplemental Postretirement Total (dollars in thousands) Year-ended December 31, 2024 $ 2,207 $ 614 $ 23 $ 2,844 2025 2,287 611 24 2,922 2026 2,413 607 24 3,044 2027 2,340 602 24 2,966 2028 2,483 596 25 3,104 2029-2033 12,961 4,192 141 17,294 Total $ 24,691 $ 7,222 $ 261 $ 32,174 Employee Profit Sharing and 401(k) Plan The Company maintains a Profit-Sharing Plan (“PSP”) that provides for deferral of federal and state income taxes on employee contributions allowed under Section 401(k) of federal law. The Company matches employee contributions up to 100 % of the first 4 % of each participant’s salary, eligible bonus, and eligible incentive. Employees are eligible to participate in the PSP on the first day of their initial date of service. The Company may also make discretionary contributions to the PSP. Employee Stock Ownership Plan The Company has an Employee Stock Ownership Plan (“ESOP”) for its eligible employees. Employees are eligible to participate upon the attainment of age 21 and the completion of 12 months of service consisting of at least 1,000 hours. Purchases of the Company’s stock by the ESOP will be funded by employer contributions or reinvestment of cash dividends. Total expenses related to the Profit Sharing and ESOP Plans for the years ended December 31, 2023, 2022 , and 2021 amounted to $ 2.8 million, $ 4.5 million, and $ 4.0 million, respectively. Defined Contribution SERP Plan For executives participating in the Defined Contribution SERP Plan (“DC SERP”) plan, the Company made a contribution of 10 % of each executive’s base salary and bonus to his or her account under the Company’s DC SERP. Total expenses related to the Company’s DC SERP for the years ended December 31, 2023, 2022 , and 2021 amounted to $ 25,000 , $ 271,000 , and $ 201,000 , respectively.

Share-Based Compensation

Share-Based Compensation	12 Months Ended
Share-Based Compensation	Dec. 31, 2023
Share-Based Payment Arrangement, Noncash Expense [Abstract]
Share-Based Compensation	15. SHARE-BASED COMPENSATION In 2017, the Company adopted the 2017 Equity and Cash Incentive Plan (the “2017 Plan”) and all future awards from date of adoption are anticipated to be made under the 2017 Plan. The 2017 Plan permits the issuance of restricted stock, restricted stock units (both time and performance-based), stock options, and stock appreciation rights. Restricted stock awards time-vest either over a three-year or five-year period and are fair valued as of the date of grant. The holders of restricted stock awards participate fully in the rewards of stock ownership of the Company, including voting and dividend rights. A summary of restricted stock outstanding as of December 31, 2023 and 2022, and changes during the years ended on those dates, is presented below: December 31, 2023 December 31, 2022 Number Weighted Number Weighted Restricted stock Non-vested at beginning of year 34,572 $ 82.19 34,622 $ 78.20 Granted 16,468 81.49 14,380 87.10 Vested ( 10,771 ) 80.94 ( 11,450 ) 76.50 Forfeited ( 2,363 ) 84.25 ( 2,980 ) 81.43 Non-vested at end of year 37,906 $ 82.11 34,572 $ 82.19 Performance-based restricted stock units vest based upon the Company’s performance over a three-year period and are fair valued as of the date of grant. The holders of performance-based restricted stock units do not participate in the rewards of stock ownership of the Company until vested. A summary of non-vested performance-based restricted stock units outstanding as of December 31, 2023 and 2022, and changes during the years ended on those dates, is presented below: December 31, 2023 December 31, 2022 Number Weighted Number Weighted Performance-based restricted stock units Non-vested at beginning of year 72,134 $ 80.83 74,699 $ 73.59 Granted 31,744 59.19 37,263 88.18 Vested (Performance achieved) ( 27,965 ) 76.00 ( 34,248 ) 70.36 Forfeited ( 7,984 ) 73.87 ( 5,580 ) 79.92 Non-vested at end of year 67,929 $ 73.87 72,134 $ 80.83 Time-based restricted stock units vest over a three-year -period and are fair valued as of the date of the grant. The holders of time-based restricted stock units do not participate in the rewards of stock ownership of the Company until vested. A summary of non-vested time-based restricted stock units outstanding as of December 31, 2023 and December 31, 2022, and changes during the years ended on those dates, is presented below: December 31, 2023 December 31, 2022 Number Weighted Number Weighted Time-based restricted stock units Non-vested at beginning of year 13,551 $ 82.81 13,836 $ 75.91 Granted 28,946 53.94 8,796 88.18 Vested ( 7,431 ) 80.96 ( 7,417 ) 75.94 Forfeited ( 3,048 ) 63.54 ( 1,664 ) 84.40 Non-vested at end of year 32,018 $ 58.98 13,551 $ 82.81 The following table presents the amounts recognized in the consolidated statements of income for restricted stock, time-based restricted stock units, and performance-based restricted stock units: For the Year Ended December 31, 2023 2022 2021 (dollars in thousands) Share-based compensation expense $ 1,589 $ 2,875 $ 3,476 Related income tax benefit $ 444 $ 804 $ 970 The 2017 Plan allows Directors of the Company to receive their annual retainer fee in the form of stock in the Company. Total shares issued to Directors under the 2017 Plan in the years ended December 31, 2023 and December 31, 2022 were 12,195 and 7,386 , respectively.

Financial Instruments with Off-

Financial Instruments with Off-Balance-Sheet Risk	12 Months Ended
Financial Instruments with Off-Balance-Sheet Risk	Dec. 31, 2023
Fair Value Disclosures [Abstract]
Financial Instruments with Off-Balance-Sheet Risk	16. FINANCIAL INSTRUMENTS WITH OFF-BALANCE-SHEET RISK To meet the financing needs of its clients, the Company is a party to financial instruments with off-balance-sheet risk in the normal course of business. These financial instruments are primarily comprised of commitments to extend credit, commitments to sell residential real estate mortgage loans and standby letters of credit. Those instruments involve, to varying degrees, elements of credit and interest rate risk in excess of the amounts recognized in the consolidated balance sheets. The Company’s exposure to credit loss in the event of nonperformance by the other party to the financial instrument for loan commitments and standby letters of credit is represented by the contractual amount of those instruments assuming that the amounts are fully advanced and that collateral or other security is of no value. The Company generally uses the same credit policies in making commitments and conditional obligations as it does for on-balance-sheet instruments. Off-balance-sheet financial instruments with contractual amounts that present credit risk include the following: December 31, 2023 December 31, 2022 (dollars in thousands) Financial instruments whose contractual amount represents credit risk: Commitments to extend credit: Unused portion of existing lines of credit $ 994,196 $ 1,073,567 Origination of new loans 18,341 25,411 Standby letters of credit 34,063 24,234 Financial instruments whose notional amount exceeds the amount of credit risk: Commitments to sell residential mortgage loans 795 250 Standby letters of credit are conditional commitments issued by the Company to guarantee performance of a client to a third party. Those guarantees are primarily issued to support public and private borrowing arrangements. Most guarantees extend for one year. The credit risk involved in issuing letters of credit is essentially the same as that involved in extending loan facilities to clients. The collateral supporting those commitments varies and may include real property, accounts receivable, or inventory. Commitments to extend credit are agreements to lend to a client 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 some of the commitments may expire without being drawn upon, the total commitment amounts do not necessarily represent future cash requirements. The Company evaluates each client’s creditworthiness on a case-by-case basis. The amount of collateral obtained upon extension of the credit is based on management’s credit evaluation of the client. Collateral held varies, but may include primary residences, accounts receivable, inventory, property, plant and equipment, and income-producing CRE. See Note 21 - Derivatives and Hedging Activities for a discussion of the Company’s derivatives and hedging activities.

Commitment and Contingencies

Commitment and Contingencies	12 Months Ended
Commitment and Contingencies	Dec. 31, 2023
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	17. COMMITMENTS AND CONTINGENCIES Lease Commitments . The Company is obligated under various lease agreements covering its main office, branch offices, and other locations. These agreements are accounted for as operating leases and their terms expire betw een 2022 and 2032 and, in some instances, contain options to renew for periods up to 25 years. The Company recognizes its operating leases on its consolidated balance sheet by recording a lease liability, representing the Company’s legal obligation to make lease payments, and a ROU asset, representing the Company’s legal right to use the leased office space and banking centers. The Company does not include renewal options for leases as part of its ROU assets and lease liabilities unless they are deemed reasonably certain to exercise. The Company does not have any material sub-lease agreements as of December 31, 2023. Operating lease expenses are comprised of operating lease costs and variable lease costs, net of sublease income, and are recognized over the lease term. Variable lease payments that are not dependent on an index or a rate or changes in variable payments based on an index or rate after the commencement date are excluded from the measurement of the lease liability, recognized in the period incurred and included within variable lease costs below. The Company determines whether a contract contains a lease based on whether a contract, or a part of a contract, conveys the right to control the use of an identified asset for a period of time in exchange for consideration. The discount rate is determined as either the rate implicit in the lease or, when a rate cannot be readily determined, the Company’s incremental borrowing rate. The incremental borrowing rate is the rate of interest that the Company would have to pay to borrow on a collateralized basis over a similar term. The components of operating lease cost and other related information are as follows: For the Year Ended December 31, 2023 2022 2021 (dollars in thousands) Operating lease cost $ 6,849 $ 6,965 $ 6,976 Variable lease cost (cost excluded from lease payments) 27 38 13 Sublease income ( 512 ) ( 316 ) ( 65 ) Total operating lease cost $ 6,364 $ 6,687 $ 6,924 Other Information Cash paid for amounts included in the measurement of lease liabilities - operating cash flows for operating leases $ 7,370 $ 7,263 $ 7,259 Operating Lease - operating cash flows (liability reduction) 6,619 6,401 6,252 Weighted average lease term - operating leases 4.92 Years 5.45 Years 6.13 Years Weighted average discount rate - operating leases 3.01 % 3.01 % 2.94 % The total minimum lease payments due in future periods under these agreements in effect at December 31, 2023 were as follows: Future Minimum December 31, 2023 Lease Payments (dollars in thousands) 2024 $ 6,959 2025 5,982 2026 4,745 2027 2,958 2028 2,589 Thereafter 3,900 Total minimum lease payments $ 27,133 Less: interest ( 1,968 ) Total lease liability $ 25,165 Several lease agreements contain clauses calling for escalation of minimum lease payments contingent on increases in real estate taxes, gross income adjustments, percentage increases in the consumer price index, and certain ancillary maintenance costs. Total rental expense wa s $ 7.5 mi llion, $ 7.6 million, and $ 7.3 million for the years ended December 31, 2023, December 31, 2022, and December 31, 2021, respectively. Change in Control Agreements . The Company has entered into agreements with its Chief Executive Officer and with certain other senior officers, whereby, following the occurrence of a change in control of the Company, if employment is terminated (except because of death, retirement, disability, or for “cause” as defined in the agreements) or is voluntarily terminated for “good reason,” as defined in the agreements, said officers will be entitled to receive additional compensation, as defined in the agreements.

Shareholders' Equity

Shareholders' Equity	12 Months Ended
Shareholders' Equity	Dec. 31, 2023
Equity [Abstract]
Shareholders' Equity	18. SHAREHOLDERS’ EQUITY Capital guidelines issued by the Federal Reserve Bank and by the FDIC require that the Company and the Bank maintain minimum capital levels for capital adequacy purposes. These regulations also require banks and their holding companies to maintain higher capital levels to be considered “well-capitalized.” 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 financial statements. Under capital adequacy guidelines and the regulatory framework for prompt corrective action, there are specific capital guidelines that involve quantitative measures of assets, liabilities, and certain off-balance-sheet items as calculated under regulatory accounting practices. The Capital Rules: (i) include “Common Equity Tier 1” (“CET1”) and related regulatory capital ratio of CET1 to risk-weighted assets; (ii) specify that Tier 1 capital consists of CET1 and “Additional Tier 1 capital” instruments meeting certain revised requirements; (iii) mandate that most deductions/adjustments to regulatory capital measures be made to CET1 and not to the other components of capital; and (iv) expand the scope of the deductions from and adjustments to capital as compared to existing regulations. Under the Capital Rules, for most banking organizations, including the Company, the most common form of Additional Tier 1 capital is non-cumulative perpetual preferred stock, and the most common forms of Tier 2 capital are subordinated notes and a portion of the allowance for credit losses, in each case, subject to the Capital Rules’ specific requirements. Pursuant to the Capital Rules, effective January 1, 2015, the minimum capital ratios are as follows: • 4.5 % CET1 to risk-weighted assets; • 6.0 % Tier 1 capital (that is, CET1 plus Additional Tier 1 capital) to risk-weighted assets; • 8.0 % Total capital (that is, Tier 1 capital plus Tier 2 capital) to risk-weighted assets; and • 4.0 % Tier 1 capital to average consolidated assets as reported on consolidated financial statements (called “leverage ratio”). Additionally, the Company is required to maintain additional capital conservation buffer of 2.5 % of CET1, effectively resulting in minimum ratios inclusive of the capital conservation buffer of (i) CET1 to risk-weighted assets of at least 7 %, (ii) Tier 1 capital to risk-weighted assets of at least 8.5 %, and (iii) total capital to risk-weighted assets of at least 10.5 %. Management believes that as of December 31, 2023 and 2022, the Company and the Bank met all applicable minimum capital requirements and were considered “well-capitalized” by both the Federal Reserve Board and the FDIC. The Company adopted ASU 2016-13 on January 1, 2020. The joint federal bank regulatory agencies issued an interim final rule that allows banking organizations to phase-in the effects of the CECL accounting standard in their regulatory capital, over a three-year period from January 1, 2022 through December 31, 2024. The Company did not elect to delay the adoption of CECL and did not adopt the transition period for regulatory capital. The Company’s and the Bank’s actual and required capital measures were as follows: Actual Minimum Capital Minimum To Be Amount Ratio Amount Ratio Amount Ratio (dollars in thousands) At December 31, 2023 Cambridge Bancorp: Total capital (to risk-weighted assets) $ 521,903 14.1 % $ 387,763 10.5 % N/A N/A Tier 1 capital (to risk-weighted assets) 481,198 13.0 % 313,903 8.5 % N/A N/A Common equity tier I capital (to risk-weighted assets) 481,198 13.0 % 258,508 7.0 % N/A N/A Tier 1 capital (to average assets) 481,198 8.9 % 216,281 4.0 % N/A N/A Cambridge Trust Company: Total capital (to risk-weighted assets) $ 500,355 13.6 % $ 387,727 10.5 % $ 369,264 10.0 % Tier 1 capital (to risk-weighted assets) 459,650 12.5 % 313,874 8.5 % 295,411 8.0 % Common equity tier I capital (to risk-weighted assets) 459,650 12.5 % 258,485 7.0 % 240,022 6.5 % Tier 1 capital (to average assets) 459,650 8.5 % 216,268 4.0 % 270,335 5.0 % Actual Minimum Capital Minimum To Be Amount Ratio Amount Ratio Amount Ratio (dollars in thousands) At December 31, 2022 Cambridge Bancorp: Total capital (to risk-weighted assets) $ 506,239 13.5 % $ 393,285 10.5 % N/A N/A Tier 1 capital (to risk-weighted assets) 466,369 12.5 % 318,373 8.5 % N/A N/A Common equity tier I capital (to risk-weighted assets) 466,369 12.5 % 262,190 7.0 % N/A N/A Tier 1 capital (to average assets) 466,369 8.5 % 219,309 4.0 % N/A N/A Cambridge Trust Company: Total capital (to risk-weighted assets) $ 490,175 13.1 % $ 393,246 10.5 % $ 374,520 10.0 % Tier 1 capital (to risk-weighted assets) 450,305 12.0 % 318,342 8.5 % 299,616 8.0 % Common equity tier I capital (to risk-weighted assets) 450,305 12.0 % 262,164 7.0 % 243,438 6.5 % Tier 1 capital (to average assets) 450,305 8.2 % 219,296 4.0 % 274,120 5.0 %

Comprehensive Income (Loss)

Comprehensive Income (Loss)	12 Months Ended
Comprehensive Income (Loss)	Dec. 31, 2023
Equity [Abstract]
Comprehensive Income (Loss)	19. COMPREHENSIVE INCOME (LOSS) Comprehensive income (loss) is defined as all changes to shareholders’ equity except investments by and distributions to shareholders. Net income is a component of comprehensive income (loss), with all other components referred to in the aggregate as “other comprehensive income (loss).” The Company’s other comprehensive income (loss) consists of unrealized gains or losses on securities held at year-end classified as available for sale, cash flow hedges, and the component of the unfunded retirement liability computed in accordance with the requirements of ASC Topic 715, “ Compensation – Retirement Benefits. ” The before-tax and after-tax amount of each of these categories, as well as the tax (expense)/benefit of each, is summarized as follows: For the Year Ended For the Year Ended For the Year Ended Before Tax Net-of- Before Tax Net-of- Before Tax Net-of- (dollars in thousands) Available for sale securities Unrealized holding gains (losses) $ 3,073 $ ( 737 ) $ 2,336 $ ( 25,144 ) $ 6,408 $ ( 18,736 ) $ ( 6,245 ) $ 1,623 $ ( 4,622 ) Reclassification adjustment for (gains) losses realized in net income (1) — — — — — — — — — Interest rate swaps designated as cash flow hedges Unrealized holding gains (losses) ( 687 ) 192 ( 495 ) ( 2,170 ) 607 ( 1,563 ) ( 1,329 ) 370 ( 959 ) Reclassification adjustment for (gains) losses recognized in net income (2) 539 ( 150 ) 389 ( 832 ) 232 ( 600 ) ( 2,587 ) 723 ( 1,864 ) Defined benefit retirement plans Net change in retirement liability 1,186 ( 331 ) 855 1,818 ( 508 ) 1,310 5,273 ( 1,472 ) 3,801 Total other comprehensive income (loss) $ 4,111 $ ( 1,026 ) $ 3,085 $ ( 26,328 ) $ 6,739 $ ( 19,589 ) $ ( 4,888 ) $ 1,244 $ ( 3,644 ) (1) Reported in gain (loss) on disposition of investment securities line item in the Consolidated Statements of Income. (2) Reported in interest on payable loans line item in the Consolidated Statements of Income. The components of accumulated other comprehensive income are as follows: For the Year Ended For the Year Ended Before Tax Amount Deferred (tax) benefit Net-of-tax Amount Before Tax Amount Deferred (tax) benefit Net-of-tax Amount (dollars in thousands) Available for sale securities $ ( 25,538 ) $ 6,651 $ ( 18,887 ) $ ( 28,611 ) $ 7,390 $ ( 21,221 ) Interest Rate swaps designated as cash flow hedges ( 157 ) 44 ( 113 ) ( 14 ) 4 ( 10 ) Defined benefit retirement plans 1,785 ( 499 ) 1,286 600 ( 168 ) 432 Total accumulated other comprehensive income $ ( 23,910 ) $ 6,196 $ ( 17,714 ) $ ( 28,025 ) $ 7,226 $ ( 20,799 )

Earnings Per Share

Earnings Per Share	12 Months Ended
Earnings Per Share	Dec. 31, 2023
Earnings Per Share [Abstract]
Earnings Per Share	20. EARNINGS PER SHARE The following represents a reconciliation between basic and diluted earnings per share: For the Year Ended December 31, 2023 2022 2021 (dollars in thousands, except per share data) Earnings per common share - basic: Numerator: Net income $ 34,109 $ 52,909 $ 54,024 Less dividends and undistributed earnings allocated ( 31 ) ( 257 ) ( 250 ) Net income applicable to common shareholders $ 34,078 $ 52,652 $ 53,774 Denominator: Weighted average common shares outstanding 7,828 7,163 6,926 Earnings per common share - basic $ 4.35 $ 7.35 $ 7.76 Earnings per common share - diluted: Numerator: Net income $ 34,109 $ 52,909 $ 54,024 Less dividends and undistributed earnings allocated ( 31 ) ( 257 ) ( 250 ) Net income applicable to common shareholders $ 34,078 $ 52,652 $ 53,774 Denominator: Weighted average common shares outstanding 7,828 7,163 6,926 Dilutive effect of common stock equivalents 15 51 65 Weighted average diluted common shares outstanding 7,843 7,214 6,991 Earnings per common share - diluted $ 4.34 $ 7.30 $ 7.69

Derivatives And Hedging Activit

Derivatives And Hedging Activities	12 Months Ended
Derivatives And Hedging Activities	Dec. 31, 2023
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Derivatives And Hedging Activities	21. DERIVATIVES and Hedging Activities The Company utilizes interest rate swaps and floors to mitigate exposure to interest rate risk and to facilitate the needs of its clients. 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 principally related to the Company’s assets. The Company is exposed to certain risk arising from both its business operations and economic conditions. The Company principally manages its exposures to a wide variety of business and operational risks through management of its core business activities. The Company manages economic risks, including interest rate, liquidity, and credit risk primarily by managing the amount, sources, and duration of its assets and liabilities and the use of derivative financial instruments. Specifically, the Company enters 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 existing credit derivatives result from loan participation arrangements, therefore, are not used to manage interest rate risk in the Company’s assets or liabilities. Cash Flow Hedges of Interest Rate Risk The Company’s objectives in using interest rate derivatives are to add stability to interest income and to manage its exposure to interest rate movements. To accomplish this objective, the Company primarily uses interest rate floors as part of its interest rate risk management strategy. Interest rate floors designated as cash flow hedges involve the receipt of variable-rate amounts from a counterparty if interest rates fall below the strike rate on the contract in exchange for an up-front premium. During 2023, such derivatives were used to hedge the variable cash flows associated with variable-rate assets. For derivatives designated and that qualify as cash flow hedges of interest rate risk, the gain or loss on the derivative is recorded in AOCI and AOCL and subsequently reclassified into interest income in the same period(s) during which the hedged transaction affects earnings. Gains and losses on the derivative representing hedge components excluded from the assessment of effectiveness are recognized over the life of the hedge on a systematic and rational basis. The earnings recognition of excluded components is presented in interest income. Amounts reported in AOCI and AOCL related to derivatives will be reclassified to interest income as interest payments are received on the Company’s variable-rate assets. During fiscal year 2024, the Company estimates that $ 391,000 will be reclassified out of AOCI into earnings, as a decrease to interest income. Fair Value Hedges of Interest Rate Risk The Company is exposed to changes in the fair value of certain pools of fixed-rate assets due to changes in benchmark interest rates. The Company uses interest rate swaps to manage its exposure to changes in fair value on these instruments attributable to changes in the designated benchmark interest rate. The Company’s interest rate swaps designated as fair value hedges involve the payment of fixed-rate amounts to a counterparty in exchange for the Company receiving variable-rate payments over the life of the agreements without the exchange of the underlying notional amount. For derivatives designated and that qualify as fair value hedges, the gain or loss on the derivative as well as the offsetting loss or gain on the hedged item attributable to the hedged risk are recognized in interest income. The Company recorded the following amounts on the balance sheet related to cumulative basis adjustment for fair value hedges: Line Item in the Statement of Financial Position in Which the Hedged Item is Included Carrying Amount of the Hedged Assets/(Liabilities) Cumulative Amount of Fair Value Hedging Adjustment Included in the Carrying Amount of the Hedged Assets/(Liabilities) December 31, 2023 December 31, 2022 December 31, 2023 December 31, 2022 (dollars in thousands) Fixed rate loans $ 498,825 $ — $ 1,175 $ — Total $ 498,825 $ — $ 1,175 $ — These amounts include the amortized cost basis of closed portfolios of fixed rate residential loans used to designate hedging relationships in which the hedged item is the stated amount of assets in the closed portfolio anticipated to be outstanding for the designated hedged period. At December 31, 2023 , the amortized cost basis of the closed portfolios used in these hedging relationships was $ 681.1 million; the cumulative basis adjustments associated with these hedging relationships was $ 1.2 million; and the notional amount of the designated hedged items were $ 500.0 million. The Company had no fair value hedges at December 31, 2022. The notional amounts of these agreements do not represent amounts exchanged by the parties and, thus, are not a measure of the potential loss exposure. At December 31, 2023 , the Company’s fair value hedges had a weighted average remaining maturity of 1.28 years, and a weighted average fixed rate of 4.16 %. Derivatives not designated as hedging instruments Derivatives not designated as hedges are not speculative and result from a service the Company provides to certain clients. For the Company’s clients, these are interest rate swaps and risk participation agreements. Interest Rate Swaps. The Company enters into interest rate swap contracts to help commercial loan borrowers manage their interest rate risk. The interest rate swap contracts with commercial loan borrowers allow them to convert floating-rate loan payments to fixed rate loan payments. When the Company enters into an interest rate swap contract with a commercial loan borrower, it simultaneously enters into a “mirror” swap contract with a third party. The third party exchanges the borrower’s fixed-rate loan payments for floating-rate loan payments. These derivatives are not designated as hedges and therefore, changes in fair value are recognized in earnings. Because these derivatives have mirror-image contractual terms, the changes in fair value substantially offset each other through earnings. Fees earned in connection with the execution of derivatives related to this program are recognized in earnings through loan related derivative income. The credit risk associated with swap transactions is the risk of default by the counterparty. To minimize this risk, the Company only enters into interest rate agreements with highly rated counterparties that management believes to be creditworthy. The notional amounts of these agreements do not represent amounts exchanged by the parties and, thus, are not a measure of the potential loss exposure. Risk Participation Agreements. The Company enters into risk participation agreements (“RPAs”) with other banks participating in commercial loan arrangements. Participating banks guarantee the performance on borrower-related interest rate swap contracts. RPAs are derivative financial instruments and are recorded at fair value. These derivatives are not designated as hedges and therefore, changes in fair value are recognized in earnings. Under a risk participation-out agreement, a derivative asset, the Company participates out a portion of the credit risk associated with the interest rate swap position executed with the commercial borrower, and pays a fee to the participating bank. Under a risk participation-in agreement, a derivative liability, the Company assumes, or participates in, a portion of the credit risk associated with the interest rate swap position with the commercial borrower and receives a fee from the other bank. The following tables present the notional amount, the location, and fair values of derivative instruments in the Company’s consolidated balance sheets: December 31, 2023 Derivative Assets Derivative Liabilities Notional Amount Balance Sheet Fair Value Notional Amount Balance Sheet Fair Value (dollars in thousands) (dollars in thousands) Derivatives designated as hedging instruments Interest rate contracts-cash flow hedging relationships $ 100,000 Other Assets $ 1,284 $ — Other Liabilities $ — Interest rate contracts-fair value hedging relationships 400,000 Other Assets 1,620 100,000 Other Liabilities 485 Total derivatives designated as hedging instruments $ 2,904 $ 485 Derivatives not designated as hedging instruments Loan related derivative contracts Interest rate contracts $ 486,310 Other Assets $ 40,338 $ 486,310 Other Liabilities $ 40,338 Risk participation agreements-out to counterparties 53,847 Other Assets 18 — Other Liabilities — Risk participation agreements-in with counterparties — Other Assets — 98,779 Other Liabilities 62 Total derivatives not designated as hedging instruments $ 40,356 $ 40,400 December 31, 2022 Derivative Assets Derivative Liabilities Notional Amount Balance Sheet Fair Value Notional Amount Balance Sheet Fair Value (dollars in thousands) (dollars in thousands) Derivatives designated as hedging instruments Interest rate contracts-cash flow hedging relationships $ 250,000 Other Assets $ 1,966 $ — Other Liabilities $ — Total derivatives designated as hedging instruments $ 1,966 $ — Derivatives not designated as hedging instruments Loan related derivative contracts Interest rate contracts $ 499,619 Other Assets $ 50,784 $ 499,619 Other Liabilities $ 50,784 Risk participation agreements-out to counterparties 46,604 Other Assets 23 — Other Liabilities — Risk participation agreements-in with counterparties — Other Assets — 71,046 Other Liabilities 43 Total derivatives not designated as hedging instruments $ 50,807 $ 50,827 The following tables present the changes to AOCI and AOCL as a result of cash flow hedge accounting as of the periods presented: Twelve Months Ended December 31, 2023 Amount of Gain or (Loss) Recognized in OCI Amount of Gain or (Loss) Recognized in OCI Included Component Amount of Gain or (Loss) Recognized in OCI Excluded Component Location of Gain or (Loss) Amount of Gain or (Loss) Reclassified from AOCL into Income Amount of Gain or (Loss) Reclassified from AOCL into Income Included Component Amount of Gain or (Loss) Reclassified from AOCL into Income Excluded Component (dollars in thousands) (dollars in thousands) Interest rate contracts $ ( 687 ) $ — $ ( 687 ) Interest Income $ ( 539 ) $ ( 96 ) $ ( 443 ) Twelve Months Ended December 31, 2022 Amount of Gain or (Loss) Recognized in OCI Amount of Gain or (Loss) Recognized in OCI - Included Component Amount of Gain or (Loss) Recognized in OCI - Excluded Component Location of Gain or (Loss) Amount of Gain or (Loss) Reclassified from AOCI into Income Amount of Gain or (Loss) Reclassified from AOCI into Income Included Component Amount of Gain or (Loss) Reclassified from AOCI into Income Excluded Component (dollars in thousands) (dollars in thousands) Interest rate contracts $ ( 2,170 ) $ 607 $ ( 1,563 ) Interest Income $ 832 $ 1,026 $ ( 194 ) The following table presents the effect of the Company’s derivative financial instruments that are not designated as hedging instruments on the consolidated statements of income as of the periods presented: Amount of Gain or (Loss) Recognized in Income For the Year Ended December 31, 2023 2022 2021 Location of Gain or (Loss) (dollars in thousands) Other contracts Loan-related derivative income $ ( 86 ) $ ( 166 ) $ ( 124 ) Credit-risk-related Contingent Features By entering into derivative transactions, the Company is exposed to credit risk to the extent that counterparties to the derivative contracts do not perform as required. Should a counterparty fail to perform under the terms of a derivative contract, the Company’s credit exposure on interest rate swaps is limited to the net positive fair value and accrued interest of all swaps with each counterparty. The Company seeks to minimize counterparty credit risk through credit approvals, limits, monitoring procedures, and obtaining collateral, where appropriate. Institutional counterparties must have an investment grade credit rating and be approved by the Company’s Board of Directors. As such, management believes the risk of incurring credit losses on derivative contracts with institutional counterparties is remote. The Company has agreements with its derivative counterparties that contain a provision where 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 on its derivative obligations. In addition, the Company also has agreements with certain of its derivative counterparties that contain a provision where if the Company fails to maintain its status as a well- capitalized institution, then the counterparty could terminate the derivative position(s) and the Company would be required to settle its obligations under the agreements. Balance Sheet Offsetting Certain financial instruments may be eligible for offset in the consolidated balance sheet and/or subject to master netting arrangements or similar agreements. The Company’s derivative transactions with institutional counterparties are generally executed under International Swaps and Derivative Association (“ISDA”) master agreements which include “right of set-off” provisions. In such cases there is generally a legally enforceable right to offset recognized amounts and there may be an intention to settle such amounts on a net basis. Generally, the Company does not offset such financial instruments for financial reporting purposes. The following tables present the information about financial instruments that are eligible for offset in the consolidated balance sheets as of December 31, 2023 and December 31, 2022: Gross Amounts Not Offset Gross Amounts Recognized Gross Amounts Offset Net Amounts Recognized Financial Instruments Collateral Pledged (Received) Net Amount December 31, 2023 (dollars in thousands) Offsetting of Derivative Assets Derivative Assets $ 43,260 $ — $ 43,260 $ 971 $ ( 41,319 ) $ 970 Offsetting of Derivative Liabilities Derivative Liabilities $ 40,885 $ — $ 40,885 $ 971 $ — $ 39,914 Gross Amounts Not Offset Gross Amounts Recognized Gross Amounts Offset Net Amounts Recognized Financial Instruments Collateral Pledged (Received) Net Amount December 31, 2022 (dollars in thousands) Offsetting of Derivative Assets Derivative Assets $ 52,773 $ — $ 52,773 $ 48 $ ( 52,130 ) $ 595 Offsetting of Derivative Liabilities Derivative Liabilities $ 50,827 $ — $ 50,827 $ 48 $ — $ 50,875 At December 31, 2023 and December 31, 2022, there were no derivatives in a net liability position related to these financial instruments.

Fair Value Measurements

Fair Value Measurements	12 Months Ended
Fair Value Measurements	Dec. 31, 2023
Fair Value Disclosures [Abstract]
Fair Value Measurements	22. FAIR VALUE MEASUREMENTS The following is a summary of the carrying values and estimated fair values of the Company’s significant financial instruments as of the dates indicated: December 31, 2023 December 31, 2022 Carrying Estimated Carrying Estimated (dollars in thousands) Financial assets Cash and cash equivalents $ 33,004 $ 33,004 $ 30,719 $ 30,719 Securities available for sale 137,838 137,838 153,416 153,416 Securities held to maturity 959,332 805,428 1,051,997 885,586 Loans, net 3,982,600 3,530,958 4,025,082 3,783,051 FHLB of Boston stock 19,056 19,056 6,264 6,264 Accrued interest receivable 15,765 15,765 14,118 14,118 Mortgage servicing rights 1,470 2,401 1,665 2,336 Interest rate contracts - cash flow hedge 1,284 1,284 1,966 1,966 Interest rate contracts - fair value hedge 1,620 1,620 — — Loan level interest rate swaps 40,338 40,338 50,784 50,784 Risk participation agreements out to counterparties 18 18 23 23 Financial liabilities Deposits, excluding wholesale deposits 4,029,511 4,026,404 4,433,817 4,429,190 Wholesale deposits 291,667 291,748 381,559 381,505 Borrowings 452,155 451,492 105,212 105,202 Interest rate contracts - fair value hedge 485 485 — — Loan level interest rate swaps 40,338 40,338 50,784 50,784 Risk participation agreements in with counterparties 62 62 43 43 The Company follows ASC Topic 820, Fair Value Measurements and Disclosures (“ASC 820”), for financial assets and liabilities. ASC Topic 820 defines fair value, establishes a framework for measuring fair value, and expands disclosure requirements about fair value measurements. ASC Topic 820, among other things, emphasizes that fair value is a market-based measurement, not an entity-specific measurement, and states that a fair value measurement should be determined based on the assumptions the market participants would use in pricing the asset or liability. In addition, ASC Topic 820 specifies a hierarchy of valuation techniques based on whether the types of valuation information (“inputs”) are observable or unobservable. Observable inputs reflect market data obtained from independent sources, while unobservable inputs reflect the Company’s market assumptions. These two types of inputs have created the following fair value hierarchy: • Level 1 – Quoted prices for identical assets or liabilities in active markets. • Level 2 – Quoted prices for similar assets or liabilities in active markets; quoted prices for identical or similar assets or liabilities in inactive markets; and model-derived valuations in which all significant inputs and significant value drivers are observable in active markets. • Level 3 – Valuations derived from techniques in which one or more significant inputs or significant value drivers are unobservable in the markets and which reflect the Company’s market assumptions. Under ASC Topic 820, fair values are based on the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date. When available, the Company uses quoted market prices to determine fair value. If quoted prices are not available, fair value is based upon valuation techniques, such as matrix pricing or other models that use, where possible, current market-based or independently sourced market parameters, such as interest rates. If observable market-based inputs are not available, the Company uses unobservable inputs to determine appropriate valuation adjustments using methodologies applied consistently over time. Valuation techniques based on unobservable inputs are highly subjective and require judgments regarding significant matters, such as the amount and timing of future cash flows and the selection of discount rates that may appropriately reflect market and credit risks. Changes in these judgments often have a material impact on the fair value estimates. In addition, since these estimates are as of a specific point in time, they are susceptible to material near-term changes. The fair values disclosed do not reflect any premium or discount that could result from offering significant holdings of financial instruments at bulk sale, nor do they reflect the possible tax ramifications or estimated transaction costs. Changes in economic conditions may also dramatically affect the estimated fair values. The Company uses fair value measurements to record fair value adjustments to certain assets and liabilities and to determine fair value disclosures. Securities available for sale, derivative instruments, and hedges are recorded at fair value on a recurring basis. Additionally, from time to time, the Company may be required to record at fair value other assets on a nonrecurring basis, such as loans held for sale, mortgage servicing rights, other real estate owned, and individually evaluated collateral dependent loans. The Company uses an exit price notion for its fair value disclosures. The following tables summarize certain assets reported at fair value on a recurring basis: Fair Value as of December 31, 2023 Level 1 Level 2 Level 3 Total (dollars in thousands) Measured on a recurring basis Securities available for sale U.S. GSE obligations $ — $ 20,462 $ — $ 20,462 Mortgage-backed securities — 117,376 — 117,376 Other assets Interest rate swaps with clients — 40,338 — 40,338 Risk participation agreements -out to counterparties — 18 — 18 Interest rate contracts - cash flow hedge — 1,284 — 1,284 Interest rate contracts - fair value hedge — 1,620 — 1,620 Other liabilities Interest rate swaps with counterparties — 40,338 — 40,338 Risk participation agreements-in with counterparties — 62 — 62 Interest rate contracts - fair value hedge — 485 — 485 Fair Value as of December 31, 2022 Level 1 Level 2 Level 3 Total (dollars in thousands) Measured on a recurring basis Securities available for sale U.S. GSE obligations $ — $ 19,733 $ — $ 19,733 Mortgage-backed securities — 132,683 — 132,683 Corporate debt securities — 1,000 — 1,000 Other assets Interest rate swaps with clients — 50,784 — 50,784 Risk participation agreements-out to counterparties — 23 — 23 Interest rate contracts — 1,966 — 1,966 Other liabilities Interest rate swaps with counterparties — 50,784 — 50,784 Risk participation agreements-in with counterparties — 43 — 43 The following table presents the carrying value of assets held at December 31, 2023 and December 31, 2022, which were measured at fair value on a non-recurring basis: December 31, 2023 Level 1 Level 2 Level 3 Total (dollars in thousands) Items recorded at fair value on a non-recurring basis Assets Individually evaluated collateral dependent loans $ — $ — $ 9,675 $ 9,675 Total $ — $ — $ 9,675 $ 9,675 December 31, 2022 Level 1 Level 2 Level 3 Total (dollars in thousands) Items recorded at fair value on a non-recurring basis Assets Individually evaluated collateral dependent loans $ — $ — $ 103 $ 103 Total $ — $ — $ 103 $ 103 Individually evaluated collateral dependent loans . Collateral dependent loans are carried at the lower of cost or fair value of the collateral less estimated costs to sell which approximates fair value. The Company uses the appraisal value of the collateral and applies certain adjustments depending on the nature, quality, and type of collateral securing the loan. There were no transfers between fair value levels for the years ended December 31, 2023 and 2022. The following is a description of the principal valuation methodologies used by the Company to estimate the fair values of its financial instruments. Investment Securities For investment securities, fair values are primarily based upon valuations obtained from a national pricing service which uses matrix pricing with inputs that are observable in the market or can be derived from, or corroborated by, observable market data. When available, quoted prices in active markets for identical securities are utilized. Loans Held for Sale For loans held for sale, fair values are estimated using projected future cash flows, discounted at rates based upon either trades of similar loans or mortgage-backed securities, or at current rates at which similar loans would be made to borrowers with similar credit ratings and for similar remaining maturities. Loans For most categories of loans, fair values are estimated using projected future cash flows, discounted at rates based upon current rates at which similar loans would be made to borrowers with similar credit ratings, and for similar remaining maturities. Projected estimated cash flows are adjusted for prepayment assumptions, liquidity premium assumptions, and credit loss assumptions. Loans that are deemed to be impaired in accordance with ASC Topic 310, Receivables , are valued based upon the lower of cost or fair value of the underlying collateral. FHLB of Boston Stock The fair value of FHLB of Boston stock equals its carrying value since such stock is only redeemable at its par value. Deposits The fair value of non-maturity deposit accounts is the amount payable on demand at the reporting date. This amount does not take into account the value of the Company’s long-term relationships with core depositors. The fair value of fixed-maturity certificates of deposit is estimated using a replacement cost of funds approach and is based upon rates currently offered for deposits of similar remaining maturities. Borrowings For long-term borrowings, fair values are estimated using future cash flows, discounted at rates based upon current costs for debt securities with similar terms and remaining maturities. Other Financial Assets and Liabilities Cash and cash equivalents, accrued interest receivable, and short-term borrowings have fair values which approximate their respective carrying values because these instruments are payable on demand or have short-term maturities and present relatively low credit risk and interest rate risk. Derivative Instruments and Hedges The valuation of these instruments is determined using widely accepted valuation techniques including discounted cash flow analysis on the expected cash flows of each derivative. This analysis reflects the contractual terms of the derivatives, including the period to maturity, and uses observable market-based inputs, including interest rate curves and implied volatilities. The Company incorporates credit valuation adjustments to appropriately reflect nonperformance risk in the fair value measurements. In adjusting the fair value of its derivative contracts for the effect of nonperformance risk, the Company has considered the impact of netting and any applicable credit enhancements, such as collateral postings. Off-Balance-Sheet Financial Instruments In the course of originating loans and extending credit, the Company will charge fees in exchange for its commitment. While these commitment fees have value, the Company has not estimated their value due to the short-term nature of the underlying commitments and their immateriality. Values Not Determined In accordance with ASC Topic 820, the Company has not estimated fair values for non-financial assets such as banking premises and equipment, goodwill, the intangible value of the Company’s portfolio of loans serviced for itself, and the intangible value inherent in the Company’s deposit relationships (i.e., core deposits), among others. Accordingly, the aggregate fair value amounts presented do not represent the underlying value of the Company.

Condensed Financial Statements

Condensed Financial Statements of Parent Company	12 Months Ended
Condensed Financial Statements of Parent Company	Dec. 31, 2023
Condensed Financial Information Disclosure [Abstract]
Condensed Financial Statements of Parent Company	23. Condensed Financial Statements of Parent Company The condensed balance sheets of Cambridge Bancorp, the Parent Company, as of December 31, 2023 and December 31, 2022 and the condensed statements of income and cash flows for each of the years in the three-year period ended December 31, 2023 are presented below. The statements of changes in shareholders’ equity are identical to the consolidated statements of changes in shareholders’ equity and are therefore not presented here. Condensed Balance Sheet December 31, 2023 2022 (dollars in thousands) ASSETS Cash and cash equivalents $ 21,212 $ 15,747 Goodwill 33 33 Other assets 337 318 Investment in subsidiary 512,991 501,454 Total assets $ 534,573 $ 517,552 SHAREHOLDERS’ EQUITY Shareholders’ equity $ 534,573 $ 517,552 Total shareholders’ equity $ 534,573 $ 517,552 Condensed Statements of Income For the Year Ended December 31, 2023 2022 2021 (dollars in thousands) Income Dividends from subsidiary $ 27,320 $ 24,734 $ 25,995 Total income 27,320 24,734 25,995 Expenses Interest expense — — — Other expenses 158 148 150 Total expenses 158 148 150 Income before income taxes and equity in undistributed income of subsidiary 27,162 24,586 25,845 Income tax benefit ( 43 ) ( 40 ) ( 42 ) Income of parent company 27,205 24,626 25,887 Equity in undistributed income of subsidiary 6,904 28,283 28,137 Net income $ 34,109 $ 52,909 $ 54,024 Condensed Statements of Cash Flows For the Year Ended December 31, 2023 2022 2021 (dollars in thousands) CASH FLOWS FROM OPERATING ACTIVITIES: Net income $ 34,109 $ 52,909 $ 54,024 Adjustments to reconcile net income to net cash provided Deferred income tax benefit ( 43 ) ( 40 ) ( 42 ) Change in other assets, net 24 12 — Change in other liabilities, net — — 13 Undistributed income of subsidiary ( 6,904 ) ( 28,283 ) ( 28,137 ) Net cash provided by operating activities 27,186 24,598 25,858 CASH FLOWS FROM INVESTING ACTIVITIES: Net cash used in investing activities — — — CASH FLOWS FROM FINANCING ACTIVITIES: Proceeds from the issuance of common stock 599 580 519 Repurchase of common stock ( 1,334 ) ( 1,320 ) ( 1,440 ) Cash dividends paid on common stock ( 20,986 ) ( 18,414 ) ( 16,554 ) Net cash provided by/(used in) financing activities ( 21,721 ) ( 19,154 ) ( 17,475 ) Net increase (decrease) in cash 5,465 5,444 8,383 Cash at beginning of year 15,747 10,303 1,920 Cash at end of year $ 21,212 $ 15,747 $ 10,303 SUPPLEMENTAL DISCLOSURES OF CASH FLOW INFORMATION: Significant non-cash transactions Common Stock issued to shareholders due to merger $ — $ 62,850 $ —

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	12 Months Ended
Summary of Significant Accounting Policies (Policies)	Dec. 31, 2023
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The consolidated financial statements have been prepared in conformity with U.S. generally accepted accounting principles (“GAAP”).
Use of Estimates	Use of Estimates The preparation of consolidated financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the consolidated financial statements. Actual results could differ from those estimates. The allowance for credit losses, the valuation of deferred tax assets, and the valuation of assets acquired and liabilities assumed in business combinations are particularly subject to change.
Reclassifications	Reclassifications Certain amounts in the prior year’s financial statements may have been reclassified to conform with the current year’s presentation.
Cash and Cash Equivalents	Cash and Cash Equivalents Cash and cash equivalents consist of cash on hand, amounts due from banks, and overnight investments.
Investment Securities	Investment Securities Investment securities are classified as either “held to maturity” or “available for sale” in accordance with the Financial Accounting Standards Board (“FASB”) Accounting Standards Codification (“ASC”) Topic 320, Investments – Debt Securities. Debt securities that management has the positive intent and ability to hold to maturity are classified as held to maturity and recorded at amortized cost. Debt securities not classified as held to maturity are classified as available for sale and carried at fair value with unrealized after-tax gains and losses reported net as a separate component of shareholders’ equity. The Company classifies its securities based on its intention at the time of purchase. Purchase premiums and discounts are recognized in interest income using the effective yield or straight-line method over the term of the securities, except for callable debt securities for which the purchase premiums are recognized through the earliest call date. Gains and losses on the sale of debt securities are recorded on the trade date and determined using the specific identification method. Allowance for Credit Losses - Held to Maturity Securities The Company measures expected credit losses on held to maturity debt securities on a collective basis by security type and risk rating where available. The reserve for each pool is calculated based on a Probability of Default/Loss Given Default (“PD/LGD”) basis taking into consideration the expected life of each security. Held to maturity securities which are issued by the United States of America (“U.S.”) or are guaranteed by U.S. federal agencies do not currently have an allowance for credit loss as the Company determined these securities are either backed by the full faith and credit of the U.S. government and/or there is an unconditional commitment to make interest payments and to return the principal investment in full to investors when a debt security reaches maturity. The Company will evaluate this position no less than annually, however, certain items which may cause the Company to change this methodology include legislative changes that remove a government-sponsored enterprise’s (“GSE”) ability to draw funds from the U.S. government, or legislative changes to housing policy that reduce or eliminate the U.S. government’s implicit guarantee on such securities. For securities which are not U.S. treasury or agency backed, risk ratings are generally sourced from Moody’s or Standard & Poor’s. The Company updates loss given default, probability of default, and recovery rates for each security as that information becomes available but no less than annually. The expected remaining life to maturity of each applicable security is updated quarterly. Any expected credit losses on held to maturity securities would be presented as an allowance rather than as a direct write-down through the consolidated statements of income if the Company does not intend to sell or believes that it is more likely than not that the Company will be required to sell the security. Allowance for Credit Losses - Available for Sale Securities The Company measures expected credit losses on available for sale securities based upon the gain or loss position of the security. For available for sale debt securities in an unrealized loss position, which the Company does not intend to sell, or it is not more likely than not that the Company will be required to sell the security before recovery of the Company’s amortized cost, the Company evaluates qualitative criteria to determine any expected loss. This includes among other items the financial health of, and specific prospects for the issuer, including whether the issuer is in compliance with the terms and covenants of the security. The Company also evaluates quantitative criteria including determining whether there has been an adverse change in expected future cash flows of the security. If the Company does not expect to recover the entire amortized cost basis of the security, an allowance for credit losses would be recorded, with a related charge to earnings, limited by the amount of the fair value of the security less its amortized cost. If the Company intends to sell the security or it is more likely than not that the Company will be required to sell the debt security before recovery of its amortized cost basis, the Company recognizes the entire difference between the security’s amortized cost basis and its fair value in earnings.
Loans	Loans Loans are reported at the amount of their outstanding principal, including deferred loan origination fees and costs, reduced by unearned discounts, and the allowance for credit losses. Loans are considered delinquent when a payment of principal and/or interest becomes past due 30 days following its scheduled payment due date. Loans on which the accrual of interest has been discontinued are designated as non-accrual loans. Loans may be removed from non-accrual when they become less than 90 days past due, they have maintained current payment status for a sustained period of time, and when concern no longer exists as to the collectability of principal or interest. Allowance for Credit Losses - Loans Losses on loan receivables are estimated and recognized upon origination of the loan, based on expected credit losses for the life of the loan balance as of the period end date. The Company’s methodology for calculating the allowance for credit losses (“ACL”) on loans consists of quantitative and qualitative components. The Company uses a discounted cash flow method incorporating probability of default and loss given default forecasted based on statistically derived economic variable loss drivers combined with qualitative factors, to estimate expected credit losses. This process includes estimates which involve modeling loss projections attributable to existing loan balances, considering historical experience, current conditions, and future expectations for homogeneous pools of loans over the reasonable and supportable forecast period. The reasonable and supportable forecast period is determined based upon the accuracy level of historical loss forecast estimates, the specific loan level models and methodology utilized, and considers material changes in growth and credit strategy, and business changes. For periods beyond a reasonable and supportable forecast interval, the Company reverts to historical information over a period for which comparable data is available. The historical information either experienced by the Company, or by a selection of peer banks when appropriate, is derived from a combination of recessionary and non-recessionary performance periods for which data is available. Similar to the reasonable and supportable forecast period, the Company reassesses the reversion period at the segment level, considering any required adjustments for differences in underwriting standards, portfolio mix, and other relevant data shifts over time. The Company generally segments its loan receivable population into homogeneous pools of loans. Consistent with the Company’s other assumptions, the Company regularly reviews segmentation to determine whether the homogeneous pools remain relevant as risk characteristics change. When a loan no longer meets the criteria of its initial pooling as a result of credit deterioration or other changes, the Company may evaluate the credit for estimated losses on an individual basis if the Company determines that the credit no longer retains the same risk characteristics. To the extent that there are a multitude of these loans with new similar risk characteristics, the Company would anticipate a change to the pooling methodology. Loans that do not share risk characteristics are evaluated on an individual basis and are not included in the collective evaluation. For loans with real estate collateral, when management determines that foreclosure is probable, expected credit losses are based on the fair value of the collateral at the reporting date, adjusted for selling costs as appropriate. The qualitative component of the ACL considers (i) the uncertainty of forward-looking scenarios; (ii) certain portfolio characteristics, such as portfolio concentrations, real estate values, changes in the number and amount of non-accrual and past due loans; and (iii) model limitations; among other factors. Qualitative adjustments are considered when management believes expected credit losses are not representative of historical loss experience alone, and should be adjusted to reflect the current conditions and characteristics of the Company’s own portfolio. They are made at the segment level, considering any required adjustments for differences in underwriting standards, portfolio mix, and other relevant data shifts over time. The Company evaluates the allowance for credit losses on loans quarterly. The Company regularly reviews its collection experience (including delinquencies and net charge-offs) in determining its allowance for credit losses. The Company also considers its historical loss experience to date based on actual defaulted loans and overall portfolio indicators including delinquent and non-accrual loans, trends in loan volume and lending terms, credit policies and other observable environmental factors such as unemployment and interest rate changes. The underlying assumption estimates and assessments the Company uses to estimate the allowance for credit losses reflects the Company’s best estimate of model assumptions and forecasted conditions at that time. Changes in such estimates can significantly affect the allowance and provision for (release of) credit losses. It is possible and likely that the Company will experience credit losses that are different from the current estimates. The provision for (release of) credit losses charged to income is based on management’s judgment of the amount necessary to maintain the allowance at a level to provide for expected credit losses for the life of the loan balances as of the evaluation date. When management believes that the collectability of a loan’s principal balance, or portions thereof, is unlikely, the principal amount is charged against the allowance for credit losses. Recoveries on loans that have been previously charged off are credited to the allowance for credit losses, generally at the time cash is received on a charged-off account. The allowance is an estimate, and ultimate losses may vary from current estimates. As adjustments become necessary, they are reported in the results of operations through the provision for (release of) credit losses in the period in which they become known. Risk characteristics relevant to each portfolio segment are as follows: Residential mortgage and home equity loans – The Company generally does not originate loans in these segments with a loan-to-value ratio greater than 80 %, unless covered by private mortgage insurance, and in all cases not greater than a loan-to-value ratio of 97 %. The Company does not originate subprime loans. Loans in these segments are secured by one-to-four family residential real estate, and repayment is primarily dependent on the credit quality of the individual borrower. Commercial mortgage loans – This includes multi-family properties and construction. The Company generally does not originate loans in this segment with a loan-to-value ratio greater than 75 % . Loans in this segment are secured by owner-occupied and non-owner-occupied commercial real estate (“CRE”), and repayment is primarily dependent on the cash flows of the property (if non-owner-occupied) or of the business (if owner-occupied). Commercial and industrial loans (“C&I”) – Loans in this segment are made to businesses and are generally secured by equipment, accounts receivable, or inventory, as well as the personal guarantees of the principal owners of the business, and repayment is primarily dependent on the cash flows generated by the business. In addition, this segment includes certain loans issued under the U. S. Small Business Administration’s (“SBA”) Paycheck Protection Program (“PPP”). These loans are guaranteed and are not evaluated for an allowance for credit losses because the Company expects the guarantees will be effective, if necessary. Consumer loans – Loans in this segment are made to individuals and can be secured or unsecured. Repayment is primarily dependent on the credit quality of the individual borrower. The majority of the Company’s loans are concentrated in Eastern Massachusetts and Southern New Hampshire and therefore the overall health of the local economy, including unemployment rates, vacancy rates, and consumer spending levels, can have a material effect on the credit quality of all of these portfolio segments. The process to determine the allowance for credit losses requires management to exercise considerable judgment regarding the risk characteristics of the loan portfolio segments and the effect of relevant internal and external factors. Allowance for Credit Losses - Unfunded Commitments The expected credit losses for unfunded commitments are measured over the contractual period of the Company’s exposure to credit risk. The estimate of credit loss incorporates assumptions for both the likelihood and amount of funding over the estimated life of the commitments, for the risk of loss, and current conditions and expectations. Management periodically reviews and updates its assumptions for estimated funding rates based on historical rates, and factors such as portfolio growth, changes to organizational structure, economic conditions, borrowing habits, or any other factor which could impact the likelihood that funding will occur. The Company does not reserve for unfunded commitments which are unconditionally cancellable. Acquired Loans Acquired loans are recorded at fair value at the date of acquisition based on a discounted cash flow methodology that considers various factors, including the type of loan and related collateral, classification status, fixed or variable interest rate, term of loan and whether or not the loan was amortizing, and a discount rate reflecting the Company’s assessment of risk inherent in the cash flow estimates. Purchased loans are grouped together according to similar risk characteristics and are treated in the aggregate when applying various valuation techniques. These cash flow evaluations are inherently subjective as they may be susceptible to significant change. Effective January 1, 2020, loans acquired in a business combination that have experienced more-than-insignificant deterioration in credit quality since origination are considered purchased credit deteriorated (“PCD”) loans. The Company evaluates acquired loans for deterioration in credit quality based on, but not limited to, the following: (1) non-accrual status; (2) troubled debt restructured designation; (3) risk ratings of special mention, substandard or doubtful; (4) watchlist credits; and (5) delinquency status, including loans that are current on acquisition date, but had been previously delinquent. At the acquisition date, an estimate of expected credit losses is made for groups of PCD loans with similar risk characteristics and individual PCD loans without similar risk characteristics. This initial allowance for credit losses is allocated to individual PCD loans and added to the purchase price or acquisition date fair values to establish the initial amortized cost basis of the PCD loans. As the initial allowance for credit losses is added to the purchase price, there is no credit loss expense recognized upon acquisition of a PCD loan. Any difference between the unpaid principal balance of PCD loans and the amortized cost basis is considered to relate to noncredit factors and results in a discount or premium. Discounts and premiums are recognized through interest income on a level-yield method over the life of the loans. For acquired loans not deemed PCD at acquisition, the differences between the initial fair value and the unpaid principal balance are recognized as interest income on a level-yield basis over the lives of the related loans. At the acquisition date, an initial allowance for expected credit losses is estimated and recorded as provision for credit losses. The subsequent measurement of expected credit losses for all acquired loans is the same as the subsequent measurement of expected credit losses for originated loans. Loans Held for Sale Residential mortgage loans originated and intended for sale in the secondary market are classified as held for sale at the time of their origination and are carried at the lower of cost or fair value on an individual loan basis. Changes in fair value relating to loans held for sale below the loans cost basis are charged against gain on loans sold. Gains and losses on the actual sale of the residential loans are recorded in earnings as gains on loans sold, net on the consolidated statements of income.
Bank Owned Life Insurance	Bank Owned Life Insurance Bank owned life insurance (“BOLI”) represents life insurance on the lives of certain active and former employees who have provided positive consent allowing the Company to be the beneficiary of such policies. Since the Company is the primary beneficiary of the insurance policies, increases in the cash value of the policies, as well as insurance proceeds received in excess of cash surrender value, are recorded in noninterest income, and are not subject to income taxes. Applicable regulations generally limit the Company’s investment in BOLI to 25 % of its Tier 1 capital plus its allowance for credit losses. The Company reviews the financial strength of the insurance carriers prior to the purchase of BOLI and at least annually thereafter.
Banking Premises and Equipment	Banking Premises and Equipment Land is stated at cost. Buildings, leasehold improvements, and equipment are stated at cost, less accumulated depreciation, and amortization, which is computed using the straight-line method over the estimated useful lives of the assets or the terms of the leases, if shorter. The cost of ordinary maintenance and repairs is charged to expense when incurred.
Leases	Leases The Company leases office space and certain branch locations under noncancelable operating leases, several of which have renewal options to extend lease terms. Upon commencement of a new lease, the Company will recognize a right-of-use (“ROU”) asset and corresponding lease liability. The Company makes the decision on whether to renew an option to extend a lease by considering various factors. The Company will recognize an adjustment to its ROU asset and lease liability when lease agreements are amended and executed. The discount rate used in determining the present value of lease payments is based on the Company’s incremental borrowing rate for borrowings with terms similar to each lease at commencement date. The Company has lease agreements with lease and non-lease components, which are generally accounted for separately. For real estate leases, non-lease components and other non-components, such as common area maintenance charges, real estate taxes, and insurance, are not included in the measurement of the lease liability since they are generally able to be segregated.
Marketing Expense	Marketing Expense Advertising costs are expensed as incurred.
Other Real Estate Owned	Other Real Estate Owned Other real estate owned consists of properties formerly pledged as collateral to loans, which have been acquired by the Company through foreclosure proceedings or acceptance of a deed in lieu of foreclosure. Upon transfer of a loan to foreclosure status, an appraisal is obtained and any excess of the loan balance over the fair value, less estimated costs to sell, is charged against the allowance for credit losses. Expenses and subsequent adjustments to the fair value are treated as noninterest expense through other expenses.
Goodwill, Core Deposit Intangibles, and Other Intangible Assets	Goodwill, Core Deposit Intangibles, and Other Intangible Assets Goodwill represents the excess of the purchase price over the fair value of net assets acquired in a business combination. Core deposit intangible (“CDI”) represents a premium paid to acquire the core deposits of an institution and is recorded as an intangible asset. Goodwill and intangible assets that are not amortized are tested for impairment, based on their fair values, at least annual ly. There was no goodwill impairment recognized during 2023, 2022, or 2021. Identifiable intangible assets that are subject to amortizatio n are also reviewed for impairment based on their fair value. Any impairment is recognized as a charge to earnings and the adjusted carrying amount of the intangible asset becomes its new accounting basis. The remaining useful life of an intangible asset that is being amortized is also evaluated each reporting period to determine whether events and circumstances warrant a revision to the remaining period of amortization. The Company is amortizing the CDI on a straight-line basis over a ten-year period. Mortgage servicing rights (“MSR”) are recognized as separate assets when rights are acquired through purchase or through sale of financial assets with servicing rights retained. The fair value of the servicing rights is determined by estimating the present value of future net cash flows, taking into consideration market loan prepayment speeds, discount rates, servicing costs, and other economic factors. For purposes of measuring impairment, the underlying loans are generally stratified into relatively homogeneous pools based on predominant risk characteristics. Because of the small size of this asset class, and its relative homogeneity, only one stratum is used. I f the aggregate carrying value of the capitalized mortgage servicing rights for this stratum exceeds its fair value, MSR impairment is recognized in earnings through a valuation allowance for the difference. As the loans are repaid and net servicing revenue is earned, the MSR asset is amortized as an offset to loan servicing income. Servicing revenues are expected to exceed this amortization expense. However, if actual prepayment experience or defaults exceed what was originally anticipated, net servicing revenues may be less than expected and mortgage servicing income may be negative.
Income Taxes	Income Taxes The Company and its subsidiaries file income tax returns in the U.S. federal jurisdiction, the Commonwealth of Massachusetts, the state of New Hampshire, the State of Connecticut, the state of Maine, and other states as required. For the tax year ended December 31, 2023, the Company expects to file taxes in Massachusetts, New Hampshire, and Maine. Income taxes are accounted for under the asset and liability method. Deferred tax assets and liabilities are reflected at currently enacted income tax rates applicable to the period in which the deferred tax assets or liabilities are expected to be realized or settled. As changes in tax laws or rates are enacted, deferred tax assets and liabilities are adjusted through income tax expenses in the period of enactment. Deferred tax assets are reviewed quarterly and reduced by a valuation allowance if, based upon the information available, it is more likely than not that some or all of the deferred tax assets will not be realized. Interest and penalties related to unrecognized tax benefits, if incurred, are recognized as a component of income tax expense.
Wealth Management Fee Revenue	Wealth Management Fee Revenue The Company earns wealth management fees for providing investment management, trust administration, and financial planning services to clients. The Company’s performance obligation under these contracts is satisfied over time as the wealth management services are provided. Fees are recognized monthly based on the monthly value of the assets under management and the applicable fee rate, or at a fixed annual rate, depending on the terms of the contract. No performance-based incentives are earned on wealth management contracts. The Company also earns trust fees for servicing as trustee for certain clients. As trustee, the Company serves as a fiduciary, administers the client’s trust, and in some cases, manages the assets of the trust. The Company’s performance obligation under these agreements is satisfied over time as the administrative and management services are provided. Fees are recognized monthly based on a percentage of the market value of the account or at a fixed annual rate as outlined in the agreement. The Company also earns fees for trust related activities. The Company’s performance obligation under these agreements is satisfied at a point in time and recognized when these services have been performed. Other Banking Fee Income The Company charges a variety of fees to its clients for services provided on the deposit and deposit management related accounts. Each fee is either transaction-based or assessed monthly. The types of fees include service charges on accounts, wire transfer fees, maintenance fees, ATM fee charges, and other miscellaneous charges related to the accounts. These fees are not governed by individual contracts with clients. They are charged to clients based on disclosures presented to these clients upon opening these accounts, along with updated disclosures when changes are made to the fee structures. The transaction-based fees are recognized in revenue when charged to the client based on specific activity on the client’s account. Monthly service and maintenance charges are recognized in the month they are earned and are charged directly to the client’s account.
Pension and Retirement Plans	Pension and Retirement Plans The Company sponsors a defined benefit pension plan (the “Pension Plan”) and a postretirement health care plan covering substantially all employees hired before May 2, 2011. Effective December 31, 2017, the accrual of benefits for all participants in the Pension Plan was frozen. Benefits for the postretirement health care plan are based on years of service. Expenses for the postretirement health care plan are recognized over the employee’s service life utilizing the projected unit credit actuarial cost method. Effective November 7, 2019, the postretirement health care plan was frozen for employees hired after that date. The Company also sponsors non-qualified retirement programs that provide supplemental retirement benefits to certain current and former executives. Prior to 2016, the Company provided individual non-qualified defined benefit supplemental executive retirement plans (“DB SERPs”) to certain executives. The DB SERPs generally provide for an annual benefit payable in equal monthly installments following the executive’s retirement and continuing for at least the remainder of his or her lifetime, with such annual benefit generally based on the executive’s years of service and his or her highest three consecutive years of base salary and bonus. In 2016, the Company’s Board of Directors discontinued the use of DB SERPs for new entrants to the Company’s non-qualified retirement programs. Instead, new entrants are provided with individual non-qualified defined contribution supplemental executive retirement plans (“DC SERPs”). Under the DC SERPs, the Company may contribute an amount equal to 10 % of the executive’s base salary and bonus to his or her account under the Company’s non-qualified deferred compensation plan, the Executive Deferred Compensation Plan. Expense for the DB SERPs is recognized over the executive’s service life utilizing the projected unit credit actuarial cost method. Expense for the DC SERPs is recognized as incurred. The Company maintains a Profit-Sharing Plan (“PSP”) that provides for deferral of federal and state income taxes on employee contributions allowed under Section 401(k) of federal law. The Company matches employee contributions up to 100 % of the first 4 % of each participant’s salary, eligible bonus, and eligible incentive. Each year, the Company may also make a discretionary contribution to the PSP based on eligible salary, bonus, and incentive. Employees are eligible to participate in the PSP on the first day of their initial date of service. Employees are also eligible to participate in the discretionary contribution portion of the PSP on the first date of their initial date of service. The employee must be employed on the last day of the calendar year or retire at the normal retirement age of 65 during the calendar year to receive the discretionary contribution.
Share-Based Compensation	Share-Based Compensation Share-based compensation plans provide for stock option awards, restricted stock awards, time-based restricted stock units (“RSUs”), and performance-based restricted stock units (“PRSUs”). Compensation expense for restricted stock awards is recognized over the vesting period based on the fair value at the date of grant. RSUs and PRSUs are valued at the fair market value of the Company’s common stock as of the award date. PRSUs’ compensation expense is based on the most recent performance assumption available and is adjusted as assumptions change. If the goals are not met, vesting does not occur, no compensation cost will be recognized and any recognized compensation costs will be reversed. Stock-based awards that do not require future service are expensed in the year of grant.
Derivative Instruments and Hedging Activities	Derivative Instruments and Hedging Activities Derivatives are recognized as either assets or liabilities on the consolidated balance sheets and are measured at fair value. The accounting for changes in the fair value of such derivatives depends on the intended use of the derivative and resulting designation. For derivatives not designated as hedges, changes in fair value of the derivative instruments are recognized in earnings in noninterest income. For derivatives designated as fair value hedges, changes in the fair value of such derivatives are recognized in earnings together with the changes in the fair value of the related hedged item. The net amount, if any, represents hedge ineffectiveness and is reflected in earnings. For derivatives designated as cash flow hedges, the effective portion of changes in the fair value of the derivative is recorded in other comprehensive income (loss) and recognized in earnings when the hedged transaction affects earnings. The ineffective portion of changes in the fair value of cash flow hedges is recognized directly in earnings.
Fair Value Measurements	Fair Value Measurements Fair value is defined as the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date. The Company measures the fair values of its financial instruments in accordance with accounting guidance that requires an entity to base fair value on exit price and maximize the use of observable inputs and minimize the use of unobservable inputs to determine the exit price. ASC 820, “ Fair Value Measurements and Disclosures” establishes a fair value hierarchy that gives the highest priority to quoted prices in active markets and the lowest priority to unobservable data and requires fair value measurements to be disclosed by level within the hierarchy. The three broad levels defined by the fair value hierarchy are as follows: Level 1 – Quoted prices are available in active markets for identical assets or liabilities as of the reported date. The type of financial instruments included in Level 1 are highly liquid cash instruments with quoted prices such as government or agency securities, listed equities, and money market securities, as well as listed derivative instruments. Level 2 – Pricing inputs are other than quoted prices in active markets, which are either directly or indirectly observable as of the reported date. The nature of these financial instruments includes cash instruments for which quoted prices are available but traded less frequently, derivative instruments whose fair value has been derived using a model where inputs to the model are directly observable in the market or can be derived principally from or corroborated by observable market data, and instruments that are fair valued using other financial instruments, the parameters of which can be directly observed. Instruments which are generally included in this category are corporate bonds and loans, mortgage whole loans, municipal bonds, and over-the-counter derivatives. Level 3 – Instruments that have little to no pricing observability as of the reported date. These financial instruments do not have two-way markets and are measured using management’s best estimate of fair value, where the inputs into the determination of fair value require significant management judgment to estimation. Instruments that are included in this category generally include certain commercial mortgage loans, certain private equity investments, distressed debt, non-investment grade residual interests in securitizations, as well as certain highly structured over-the-counter derivative contracts.
Earnings per Common Share	Earnings per Common Share Earnings per common share is computed using the more dilutive two-class method prescribed under ASC Topic 260, “Earnings Per Share.” ASC Topic 260 provides that unvested share-based payment awards that contain nonforfeitable rights to dividends or dividend equivalents (whether paid or unpaid) are participating securities and shall be included in the computation of earnings per share pursuant to the two-class method. The Company has determined that its outstanding non-vested stock awards are participating securities. Under the two-class method, basic earnings per common share is computed by dividing net earnings allocated to common stock by the weighted-average number of common shares outstanding during the applicable period, including outstanding participating securities. Diluted earnings per common share is computed using the weighted-average number of shares determined for the basic earnings per common share computation plus the dilutive effect of common stock equivalents. A reconciliation of the weighted-average shares used in calculating basic earnings per common share and the weighted average common shares used in calculating diluted earnings per common share for the reported periods is provided in Note 20 - Earnings Per Share .
Subsequent Events	Subsequent Events Management has reviewed events occurring through March 12, 2024, the date the consolidated financial statements were issued and determined that no subsequent events occurred requiring adjustment to or disclosure in these consolidated financial statements.
Recently Issued and Adopted Accounting Standards	3. Recently Issued and Adopted Accounting Standards Accounting Pronouncements Adopted in 2023 In March 2022, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) 2022-02, Financial Instruments – Credit Losses (Topic 326): Troubled Debt Restructurings and Vintage Disclosures. The amendments in this ASU eliminate the accounting guidance for troubled debt restructurings (“TDRs”) by creditors in Subtopic 310-40, Receivables – Troubled Debt Restructurings by Creditors , while enhancing disclosure requirements for certain loan refinancings and restructurings by creditors when a borrower is experiencing financial difficulty. For public business entities, the amendments in this ASU require an entity to disclose current-period gross write-offs by year of origination for financing receivables and net investments in leases. This ASU was effective for fiscal years beginning after December 15, 2022, including interim periods within those fiscal years. Early adoption was permitted. The Company adopted the new standard on January 1, 2023 and the adoption did not have a material impact on the consolidated financial statements. In March 2022, the FASB issued ASU 2022-01, Derivatives and Hedging (Topic 815): Fair Value Hedging - Portfolio Layer Method . The amendments in this ASU allow multiple hedged layers to be designated for a single closed portfolio of financial assets or one or more beneficial interests secured by a portfolio of financial instruments. The amendments in this ASU also clarify the accounting for and promote consistency in the reporting of hedge basis adjustments applicable to both a single hedged layer and multiple hedged layers. These amendments are effective for fiscal years beginning after December 15, 2022, and interim periods within those fiscal years. The Company adopted the new standard on January 1, 2023 and provided the additional disclosures required for the Company's fair value hedging relationships. Accounting Pronouncements Yet to be Adopted In December 2023, the FASB issued ASU 2023-09, Income Taxes (Topic 740): Improvements to Income Tax Disclosures. The amendments are to enhance the transparency and decision usefulness of income tax disclosures. The ASU requires that public business entities on an annual basis (1) disclose specific categories in the rate reconciliation, (2) provide additional information for reconciling items that meet a quantitative threshold. and also includes certain other amendments to improve the effectiveness of income tax disclosures. The amendments in this Update are effective for annual periods beginning after December 15, 2024. The Company is currently assessing the impact the adoption of this guidance will have on its consolidated financial statements and disclosures.

Investment Securities (Tables)

Investment Securities (Tables)	12 Months Ended
Investment Securities (Tables)	Dec. 31, 2023
Investments, Debt and Equity Securities [Abstract]
Summary of Carrying Amounts of Securities and Their Approximate Fair Values	Investment securities have been classified in the accompanying consolidated balance sheets according to management’s intent. The carrying amounts of securities and their approximate fair values were as follows: December 31, 2023 December 31, 2022 Amortized Gross Gross Fair Amortized Gross Gross Fair (dollars in thousands) Available for sale securities U.S. Government Sponsored $ 22,998 $ — $ ( 2,536 ) $ 20,462 $ 22,997 $ — $ ( 3,264 ) $ 19,733 Mortgage-backed securities 140,378 4 ( 23,006 ) 117,376 158,034 3 ( 25,354 ) 132,683 Corporate debt securities — — — — 996 4 — 1,000 Total available for sale securities $ 163,376 $ 4 $ ( 25,542 ) $ 137,838 $ 182,027 $ 7 $ ( 28,618 ) $ 153,416 Held to maturity securities U.S. Treasury Notes $ 3,039 $ — $ ( 13 ) $ 3,026 $ 3,970 $ — $ ( 18 ) $ 3,952 Mortgage-backed securities 871,426 17 ( 146,397 ) 725,046 951,372 4 ( 157,208 ) 794,168 Corporate debt securities 250 — ( 2 ) 248 250 — ( 6 ) 244 Municipal securities 84,617 24 ( 7,533 ) 77,108 96,405 88 ( 9,271 ) 87,222 Total held to maturity securities $ 959,332 $ 41 $ ( 153,945 ) $ 805,428 $ 1,051,997 $ 92 $ ( 166,503 ) $ 885,586 Total $ 1,122,708 $ 45 $ ( 179,487 ) $ 943,266 $ 1,234,024 $ 99 $ ( 195,121 ) $ 1,039,002
Schedule of Amortized Cost and Fair Value of Investment Securities, Aggregated By Earlier of Guaranteed Call Date or Contractual Maturity	The amortized cost and fair value of investment securities, aggregated by the contractual maturity, are shown below. Municipal securities are aggregated by the earliest of call date or contractual maturity. Maturities of mortgage-backed securities do not take into consideration scheduled amortization or prepayments. Actual maturities may differ from contractual maturities because issuers may have the right to call or prepay obligations with or without call or prepayment penalties. December 31, 2023 Within One Year After One, But After Five, But After Ten Years Total Amortized Fair Amortized Fair Amortized Fair Amortized Fair Amortized Fair (dollars in thousands) Available for sale securities U.S. Government Sponsored Enterprise obligations $ — $ — $ 9,998 $ 9,360 $ 5,000 $ 4,506 $ 8,000 $ 6,596 $ 22,998 $ 20,462 Mortgage-backed securities — — 11,466 10,877 37,207 31,611 91,705 74,888 140,378 117,376 Total available for sale securities $ — $ — $ 21,464 $ 20,237 $ 42,207 $ 36,117 $ 99,705 $ 81,484 $ 163,376 $ 137,838 Held to maturity securities U.S. Treasury Notes $ 2,076 $ 2,065 $ 963 $ 961 $ — $ — $ — $ — $ 3,039 $ 3,026 Mortgage-backed securities — — 23,490 22,378 50,094 43,247 797,842 659,421 871,426 725,046 Corporate debt securities 250 248 — — — — — — 250 248 Municipal securities 2,666 2,663 22,397 22,309 22,051 21,620 37,503 30,516 84,617 77,108 Total held to maturity securities $ 4,992 $ 4,976 $ 46,850 $ 45,648 $ 72,145 $ 64,867 $ 835,345 $ 689,937 $ 959,332 $ 805,428 Total $ 4,992 $ 4,976 $ 68,314 $ 65,885 $ 114,352 $ 100,984 $ 935,050 $ 771,421 $ 1,122,708 $ 943,266
Gross Unrealized Losses of Aggregated by Investment Category and Length of Time that Individual Investment Securities have been in Continuous Loss Position	The following tables show the Company’s investment securities with gross unrealized losses, for which an allowance for credit losses has not been recorded at December 31, 2023 or at December 31, 2022, aggregated by investment category and length of time that individual investment securities have been in a continuous loss position: December 31, 2023 Less than 12 months 12 months or longer Total Fair Unrealized Fair Unrealized Fair Unrealized (dollars in thousands) Available for sale securities U.S. Government Sponsored Enterprise $ — $ — $ 20,462 $ ( 2,536 ) $ 20,462 $ ( 2,536 ) Mortgage-backed securities 79 ( 1 ) 113,478 ( 23,005 ) 113,557 ( 23,006 ) Total available for sale securities $ 79 $ ( 1 ) $ 133,940 $ ( 25,541 ) $ 134,019 $ ( 25,542 ) Held to maturity securities U.S. Treasury Notes $ 961 $ ( 2 ) $ 2,065 $ ( 11 ) $ 3,026 $ ( 13 ) Mortgage-backed securities — — 723,042 ( 146,397 ) 723,042 ( 146,397 ) Corporate debt securities — — 248 ( 2 ) 248 ( 2 ) Municipal securities 17,401 ( 79 ) 44,548 ( 7,454 ) 61,949 ( 7,533 ) Total held to maturity securities $ 18,362 $ ( 81 ) $ 769,903 $ ( 153,864 ) $ 788,265 $ ( 153,945 ) Total $ 18,441 $ ( 82 ) $ 903,843 $ ( 179,405 ) $ 922,284 $ ( 179,487 ) December 31, 2022 Less than 12 months 12 months or longer Total Fair Unrealized Fair Unrealized Fair Unrealized (dollars in thousands) Available for sale securities U.S. Government Sponsored Enterprise $ 10,722 $ ( 2,278 ) $ 9,012 $ ( 986 ) $ 19,734 $ ( 3,264 ) Mortgage-backed securities 41,832 ( 3,097 ) 90,545 ( 22,257 ) 132,377 ( 25,354 ) Total available for sale securities $ 52,554 $ ( 5,375 ) $ 99,557 $ ( 23,243 ) $ 152,111 $ ( 28,618 ) Held to maturity securities U.S. Treasury Notes $ 3,952 $ ( 18 ) $ — $ — $ 3,952 $ ( 18 ) Mortgage-backed securities 230,708 ( 22,362 ) 562,835 ( 134,846 ) 793,543 ( 157,208 ) Corporate debt securities 243 ( 6 ) — — 243 ( 6 ) Municipal securities 51,969 ( 4,388 ) 13,714 ( 4,883 ) 65,683 ( 9,271 ) Total held to maturity securities $ 286,872 $ ( 26,774 ) $ 576,549 $ ( 139,729 ) $ 863,421 $ ( 166,503 ) Total $ 339,426 $ ( 32,149 ) $ 676,106 $ ( 162,972 ) $ 1,015,532 $ ( 195,121 )
Summary of Gains (Losses) from Sale of Investment Securities	The following table sets forth information regarding sales of investment securities and the resulting gains or losses from such sales: For the Year Ended December 31, 2023 2022 2021 (dollars in thousands) Amortized cost of securities sold $ — $ 19,018 $ — Gross gains realized on securities sold — — — Gross losses realized on securities sold — — — Net proceeds from securities sold $ — $ 19,018 $ —
Summary of Credit Rating of Debt Securities Portfolio	The following tables summarize the credit rating of the Company’s debt securities portfolio at December 31, 2023 and December 31, 2022. December 31, 2023 Mortgage-backed Securities (1) Corporate Debt Securities Municipal Securities U.S. GSE Obligations U.S. Treasury Notes Total (dollars in thousands) Available for sale securities, at fair value AAA/AA/A $ 117,376 $ — $ — $ 20,462 $ — $ 137,838 Total available for sale securities $ 117,376 $ — $ — $ 20,462 $ — $ 137,838 Held to maturity securities, at amortized cost AAA/AA/A $ 871,426 $ 250 $ 84,617 $ — $ 3,039 $ 959,332 Total held to maturity securities $ 871,426 $ 250 $ 84,617 $ — $ 3,039 $ 959,332 December 31, 2022 Mortgage-backed Securities (1) Corporate Debt Securities Municipal Securities U.S. GSE Obligations U.S. Treasury Notes Total (dollars in thousands) Available for sale securities, at fair value AAA/AA/A $ 132,683 $ — $ — $ 19,733 $ — $ 152,416 BBB/BB/B — 1,000 — — — 1,000 Total available for sale securities $ 132,683 $ 1,000 $ — $ 19,733 $ — $ 153,416 Held to maturity securities, at amortized cost AAA/AA/A $ 951,372 $ 250 $ 96,405 $ — $ 3,970 $ 1,051,997 Total held to maturity securities $ 951,372 $ 250 $ 96,405 $ — $ 3,970 $ 1,051,997 1. Includes Agency mortgage-backed pass-through securities and collateralized mortgage obligations issued by U.S. Government Sponsored Enterprises (“GSEs”) and U.S. government agencies, such as FNMA, FHLMC, and GNMA that are not rated by Moody’s or Standard & Poor's. Each security contains a guarantee by the issuing GSE or agency and therefore carries an implicit guarantee of the U.S. government. These have been categorized as AAA/AA/A.

Loans and the Allowance for C_2

Loans and the Allowance for Credit Losses (Tables)	12 Months Ended
Loans and the Allowance for Credit Losses (Tables)	Dec. 31, 2023
Receivables [Abstract]
Loans Outstanding by Category	Loans outstanding are detailed by category as follows: December 31, 2023 December 31, 2022 (dollars in thousands) Residential mortgage Mortgages - fixed rate $ 813,374 $ 902,968 Mortgages - adjustable rate 760,632 703,958 Construction 45,863 35,299 Deferred costs, net of unearned fees 6,395 6,613 Total residential mortgages 1,626,264 1,648,838 Commercial mortgage Mortgages - non-owner occupied 1,648,408 1,592,732 Mortgages - owner occupied 167,522 183,591 Construction 113,133 135,782 Deferred costs, net of unearned fees 2,410 2,318 Total commercial mortgages 1,931,473 1,914,423 Home equity Home equity - lines of credit 92,730 108,961 Home equity - term loans 2,679 2,098 Deferred costs, net of unearned fees 240 292 Total home equity 95,649 111,351 Commercial and industrial Commercial and industrial 342,475 349,026 Paycheck Protection Program loans 653 1,384 Unearned fees, net of deferred costs 583 240 Total commercial and industrial 343,711 350,650 Consumer Secured 22,592 35,679 Unsecured 1,822 1,897 Deferred costs, net of unearned fees 33 18 Total consumer 24,447 37,594 Total loans $ 4,021,544 $ 4,062,856
Non-performing Loans Disaggregated by Loan Category	The following tables set forth information regarding non-performing loans disaggregated by loan category: December 31, 2023 Residential Commercial Home Commercial and Total (dollars in thousands) Non-performing loans: Non-accrual loans $ 6,412 $ 9,758 $ 285 $ 61 $ 16,516 Loans past due >90 days, but still accruing — — — 51 51 Total $ 6,412 $ 9,758 $ 285 $ 112 $ 16,567 December 31, 2022 Residential Commercial Home Commercial and Total (dollars in thousands) Non-performing loans: Non-accrual loans $ 4,733 $ 311 $ 722 $ 73 $ 5,839 Troubled debt restructurings 622 — — 81 $ 703 Total $ 5,355 $ 311 $ 722 $ 154 $ 6,542
Schedule of Amortized Costs Basis and Related Reserve Amount	The following table presents the amortized costs basis and related reserve amount of individually analyzed collateral-dependent loans by portfolio segment. For the Year Ended December 31, 2023 2022 Amortized Cost Basis Reserve Amount Amortized Cost Basis Reserve Amount (dollars in thousands) Commercial mortgage $ 9,611 $ 2,345 $ - $ - Commercial & Industrial 64 43 103 82 Total $ 9,675 $ 2,388 $ 103 $ 82
Loans Receivable Disaggregated by Credit Quality Indicator	The following tables contain period-end balances of loans receivable disaggregated by credit quality indicator: Credit Quality Indicator - by Origination Year as of December 31, 2023 2023 2022 2021 2020 2019 Prior Revolving loans amortized cost basis Total (dollars in thousands) Residential Mortgage: Current $ 92,911 $ 331,817 $ 507,677 $ 274,988 $ 111,715 $ 300,744 $ — $ 1,619,852 Non-performing 193 1,490 4,729 — 6,412 Total $ 92,911 $ 331,817 $ 507,677 $ 275,181 $ 113,205 $ 305,473 $ — $ 1,626,264 Current-period gross write-offs $ — $ — $ — $ — $ — $ — $ — $ — Home equity: Current $ 8,085 $ 2,411 $ 2,241 $ 1,399 $ 2,587 $ 14,674 $ 63,967 $ 95,364 Non-performing 58 227 — 285 Total $ 8,085 $ 2,469 $ 2,241 $ 1,399 $ 2,587 $ 14,901 $ 63,967 $ 95,649 Current-period gross write-offs $ — $ — $ — $ — $ — $ — $ — $ — Consumer: Current $ 7,281 $ 7,459 $ 1,706 $ 2,841 $ 694 $ 3,842 $ 624 $ 24,447 Non-performing — — — — — — — — Total $ 7,281 $ 7,459 $ 1,706 $ 2,841 $ 694 $ 3,842 $ 624 $ 24,447 Current-period gross write-offs $ — $ — $ — $ — $ — $ 67 $ — $ 67 Credit Quality Indicator - by Origination Year as of December 31, 2023 2023 2022 2021 2020 2019 Prior Revolving loans amortized cost basis Total (dollars in thousands) Commercial Mortgage: Credit risk profile by internally assigned grade: 1-6 (Pass) $ 69,636 $ 466,760 $ 360,331 $ 226,994 $ 258,296 $ 459,472 $ — $ 1,841,489 7 (Special Mention) 1,826 1,822 — 1,507 48,470 25,493 — 79,118 8 (Substandard) — 1,096 — — — 9,770 — 10,866 9 (Doubtful) — — — — — — — — 10 (Loss) — — — — — — — — Total $ 71,462 $ 469,678 $ 360,331 $ 228,501 $ 306,766 $ 494,735 $ — $ 1,931,473 Current-period gross write-offs $ — $ — $ — $ — $ — $ — $ — $ — Commercial and Industrial: Credit risk profile by internally assigned grade: 1-6 (Pass) $ 43,388 $ 107,494 $ 46,678 $ 50,660 $ 22,325 $ 40,647 $ 436 $ 311,628 7 (Special Mention) 60 25,057 92 3,467 2 121 10 28,809 8 (Substandard) — 1,321 — 256 1,575 122 — 3,274 9 (Doubtful) — — — — — — — — 10 (Loss) — — — — — — — — Total $ 43,448 $ 133,872 $ 46,770 $ 54,383 $ 23,902 $ 40,890 $ 446 $ 343,711 Current-period gross write-offs $ — $ — $ — $ — $ — $ 62 $ — $ 62 Credit Quality Indicator - by Origination Year as of December 31, 2022 2022 2021 2020 2019 2018 Prior Revolving loans amortized cost basis Total (dollars in thousands) Residential Mortgage: Current $ 339,634 $ 531,147 $ 294,370 $ 119,414 $ 84,215 $ 274,703 $ — $ 1,643,483 Non-performing — — 206 315 684 4,150 — 5,355 Total $ 339,634 $ 531,147 $ 294,576 $ 119,729 $ 84,899 $ 278,853 $ — $ 1,648,838 Home equity: Current $ 5,291 $ 2,958 $ 1,349 $ 1,541 $ 867 $ 479 $ 98,144 $ 110,629 Non-performing — — — — — — 722 722 Total $ 5,291 $ 2,958 $ 1,349 $ 1,541 $ 867 $ 479 $ 98,866 $ 111,351 Consumer: Current $ 13,263 $ 8,573 $ 5,602 $ 836 $ 2,092 $ 6,631 $ 597 $ 37,594 Non-performing — — — — — — — — Total $ 13,263 $ 8,573 $ 5,602 $ 836 $ 2,092 $ 6,631 $ 597 $ 37,594 Credit Quality Indicator - by Origination Year as of December 31, 2022 2022 2021 2020 2019 2018 Prior Revolving loans amortized cost basis Total (dollars in thousands) Commercial Mortgage: Credit risk profile by internally 1-6 (Pass) $ 448,919 $ 366,414 $ 240,023 $ 269,899 $ 131,415 $ 383,473 $ — $ 1,840,143 7 (Special Mention) — — 4,562 41,578 21,697 6,132 — 73,969 8 (Substandard) — — — — — 311 — 311 9 (Doubtful) — — — — — — — — 10 (Loss) — — — — — — — — Total $ 448,919 $ 366,414 $ 244,585 $ 311,477 $ 153,112 $ 389,916 $ — $ 1,914,423 Commercial and Industrial: Credit risk profile by internally 1-6 (Pass) $ 130,418 $ 69,030 $ 65,390 $ 29,543 $ 20,549 $ 27,310 $ 475 $ 342,715 7 (Special Mention) — 4,211 130 161 407 121 10 5,040 8 (Substandard) — — 628 2,102 81 84 — 2,895 9 (Doubtful) — — — — — — — — 10 (Loss) — — — — — — — — Total $ 130,418 $ 73,241 $ 66,148 $ 31,806 $ 21,037 $ 27,515 $ 485 $ 350,650
Schedule of Loans Receivable Disaggregated by Past Due Status	The following tables contain period-end balances of loans receivable disaggregated by past due status: December 31, 2023 30-59 Days 60-89 Days 90 Days or Greater Total Current Total (dollars in thousands) Residential mortgage $ 16,768 $ 1,234 $ 2,548 $ 20,550 $ 1,605,714 $ 1,626,264 Commercial mortgage 1,885 — — 1,885 1,929,588 1,931,473 Home equity 1,855 171 — 2,026 93,623 95,649 Commercial and industrial 1,477 301 58 1,836 341,875 343,711 Consumer 251 14 — 265 24,182 24,447 Total $ 22,236 $ 1,720 $ 2,606 $ 26,562 $ 3,994,982 $ 4,021,544 December 31, 2022 30-59 Days 60-89 Days 90 Days Total Current Total (dollars in thousands) Residential mortgage $ 11,359 $ 1,454 $ 1,809 $ 14,622 $ 1,634,216 $ 1,648,838 Commercial mortgage — — — — 1,914,423 1,914,423 Home equity 962 393 214 1,569 109,782 111,351 Commercial and industrial 65 269 — 334 350,316 350,650 Consumer 81 — — 81 37,513 37,594 Total $ 12,467 $ 2,116 $ 2,023 $ 16,606 $ 4,046,250 $ 4,062,856
Summary of Changes in Allowance for Credit Losses Disaggregated by Loan Category	The following tables contain changes in the allowance for credit losses disaggregated by loan category: For The Year Ended December 31, 2023 Residential Commercial Home Commercial & Consumer Unfunded Commitments Total (dollars in thousands) Allowance for credit loss: Allowance for credit losses - loan Balance at December 31, 2022 $ 13,321 $ 19,086 $ 573 $ 4,153 $ 641 $ — $ 37,774 Charge-offs — — — ( 62 ) ( 67 ) — ( 129 ) Recoveries — — — 37 22 — 59 Provision for (release of) credit ( 4,922 ) 5,366 7 812 ( 23 ) — 1,240 Allowance for credit losses - loan portfolio $ 8,399 $ 24,452 $ 580 $ 4,940 $ 573 $ — $ 38,944 Allowance for credit losses - Balance at December 31, 2022 $ — $ — $ — $ — $ — $ 2,096 $ 2,096 Provision for (release of) credit — — — — — ( 336 ) ( 336 ) Allowance for credit losses- $ — $ — $ — $ — $ — $ 1,760 $ 1,760 Total allowance for credit loss $ 8,399 $ 24,452 $ 580 $ 4,940 $ 573 $ 1,760 $ 40,704 For The Year Ended December 30, 2022 Residential Commercial Home Commercial & Consumer Unfunded Commitments Total (dollars in thousands) Allowance for credit loss: Allowance for credit losses - loan Balance at December 31, 2021 $ 13,383 $ 17,133 $ 406 $ 2,989 $ 585 $ — $ 34,496 Provision for acquired loans 527 1,337 117 113 8 — 2,102 Initial allowance for PCD 19 37 — — — — 56 Charge-offs — — — ( 23 ) ( 29 ) — ( 52 ) Recoveries 4 — — 89 12 — 105 Provision for (release of) credit ( 612 ) 579 50 985 65 — 1,067 Allowance for credit losses - loan portfolio $ 13,321 $ 19,086 $ 573 $ 4,153 $ 641 $ — $ 37,774 Allowance for credit losses - Balance at December 31, 2021 $ — $ — $ — $ — $ — $ 1,384 $ 1,384 Acquired loan commitments — — — — — 137 137 Provision for credit — — — — — 575 575 Allowance for credit losses- — — — — — 2,096 2,096 Total allowance for credit loss $ 13,321 $ 19,086 $ 573 $ 4,153 $ 641 $ 2,096 $ 39,870

Banking Premises and Equipment

Banking Premises and Equipment (Tables)	12 Months Ended
Banking Premises and Equipment (Tables)	Dec. 31, 2023
Property, Plant and Equipment [Abstract]
Summary of Cost and Accumulated Depreciation and Amortization of Property, Leasehold Improvements and Equipment	A summary of the cost and accumulated depreciation and amortization of property, leasehold improvements, and equipment is presented below: December 31, Estimated 2023 2022 Useful Lives (dollars in thousands) Land $ 3,396 $ 3,396 Building and leasehold improvements 25,586 25,588 3 - 30 years Equipment, including vaults 21,460 20,165 3 - 20 years Work in process 149 22 Subtotal 50,591 49,171 Accumulated depreciation and amortization ( 28,838 ) ( 25,874 ) Total $ 21,753 $ 23,297

Intangible Assets (Tables)

Intangible Assets (Tables)	12 Months Ended
Intangible Assets (Tables)	Dec. 31, 2023
Schedule of Mortgage Servicing Rights	The following table provides an analysis of mortgage servicing rights, which are included in other assets: Mortgage Valuation Total (dollars in thousands) Balance at December 31, 2020 $ 1,361 $ ( 142 ) $ 1,219 Mortgage servicing rights capitalized 281 — 281 Amortization charged against servicing income ( 559 ) — ( 559 ) Change in impairment reserve — 142 142 Balance at December 31, 2021 $ 1,083 $ — $ 1,083 Balance at December 31, 2021 $ 1,083 $ — $ 1,083 Mortgage servicing rights acquired as a result of the Northmark merger 785 — 785 Mortgage servicing rights capitalized 71 — 71 Amortization charged against servicing income ( 274 ) — ( 274 ) Balance at December 31, 2022 $ 1,665 $ — $ 1,665 Balance at December 31, 2022 $ 1,665 $ — $ 1,665 Mortgage servicing rights capitalized 74 — 74 Amortization charged against servicing income ( 269 ) — ( 269 ) Balance at December 31, 2023 $ 1,470 $ — $ 1,470
Mortgage Servicing Rights
Schedule of Aggregate Estimated Future Amortization Expense	The estimated aggregate future amortization expense for mortgage servicing rights for each of the next five years and thereafter is as follows: Future Amortization Expense (dollars in thousands) 2024 $ 173 2025 153 2026 136 2027 121 2028 109 Thereafter 778 Total $ 1,470

Deposits (Tables)

Deposits (Tables)	12 Months Ended
Deposits (Tables)	Dec. 31, 2023
Deposits [Abstract]
Summary of Deposits	Deposits are summarized as follows: December 31, 2023 December 31, 2022 (dollars in thousands) Demand deposits (non-interest bearing) $ 1,032,413 $ 1,366,395 Interest bearing checking 1,132,518 908,961 Money market 983,480 1,162,773 Savings 498,386 790,628 Retail certificates of deposit under $250,000 212,694 117,532 Retail certificates of deposit $250,000 or greater 170,020 87,528 Brokered certificates of deposit 291,667 381,559 Total deposits $ 4,321,178 $ 4,815,376
Scheduled Maturities of Certificates of Deposits	Certificates of deposit had the following schedule of maturities: December 31, 2023 December 31, 2022 (dollars in thousands) 2023 $ — $ 533,513 2024 655,266 39,753 2025 11,388 5,377 2026 5,918 6,021 2027 1,315 1,955 2028 and after 494 — Total certificates of deposit $ 674,381 $ 586,619

Borrowings (Tables)

Borrowings (Tables)	12 Months Ended
Borrowings (Tables)	Dec. 31, 2023
Debt Disclosure [Abstract]
Schedule of Information Relating to Borrowings and Weighted Average Interest Rates	Information relating to the Company’s borrowings, their remaining maturities, and weighted average interest rates are presented below: For the Year Ended December 31, 2023 2022 Amount Weighted Average Interest Rate Amount Weighted Average Interest Rate (dollars in thousands) Within one year $ 406,000 5.38 % $ 100,176 4.38 % Over one year to three years 45,000 4.27 % — — % Over three years to five years (1) 717 — % — — % Over five years (1) 438 — % — — % Total FHLB of Boston $ 452,155 5.26 % $ 100,176 4.38 % (1) Includes advances under the FHLB of Boston Jobs for New England (“JNE”) program, which are zero rate borrowings.

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
Income Taxes (Tables)	Dec. 31, 2023
Income Tax Disclosure [Abstract]
Components of Income Tax Expense	The components of income tax expense were as follows: For the Year Ended December 31, 2023 2022 2021 (dollars in thousands) Current income tax expense Federal $ 7,740 $ 12,906 $ 11,330 State 2,895 5,559 4,862 Total current income tax expense 10,635 18,465 16,192 Deferred income tax expense Federal 1,091 455 1,840 State 574 132 1,059 Total deferred income tax expense 1,665 587 2,899 Total income tax expense $ 12,300 $ 19,052 $ 19,091
Reconciliation of Total Income Tax Expense, Calculated at Statutory Federal Income Tax Expense in Consolidated Statements of Income	The following is a reconciliation of the total income tax expense, calculated at statutory federal income tax rates, to the income tax provision in the consolidated statements of income: For the Year Ended December 31, 2023 2022 2021 (dollars in thousands) Income tax expense at statutory rate of 21.0 % $ 9,746 $ 15,112 $ 15,354 Increase/(decrease) resulting from: State tax, net of federal tax benefit 2,741 4,496 4,678 Tax-exempt income ( 597 ) ( 814 ) ( 795 ) ESOP dividends ( 151 ) ( 150 ) ( 145 ) Bank owned life insurance ( 148 ) ( 133 ) ( 165 ) Compensation limited under 162(m) 112 193 226 Benefit from stock compensation 17 ( 81 ) ( 46 ) Non-deductible acquisition costs 657 182 — Non-deductible expenses 71 44 55 BOLI surrender, death benefit — 310 — Other ( 148 ) ( 107 ) ( 71 ) Total income tax expense $ 12,300 $ 19,052 $ 19,091
Summary of Net Deferred Tax Asset	The Company’s 2023 and 2022 net deferred tax assets were measured using a 27.95 % federal and state blended tax rate, respectively, and consisted of the following components: December 31, 2023 December 31, 2022 (dollars in thousands) Gross deferred tax assets Allowance for credit losses $ 11,377 $ 11,142 Unrealized losses on available for sale securities 6,652 7,390 Incentive compensation 1,379 1,819 Equity based compensation 910 1,298 Lease liabilities 7,033 7,661 ESOP dividends 202 200 Intangibles and fair value marks (merger related) 1,841 2,322 Other 528 931 Total gross deferred tax assets 29,922 32,763 Gross deferred tax liabilities Deferred loan origination costs ( 2,835 ) ( 2,886 ) Retirement benefits ( 2,460 ) ( 1,745 ) Depreciation of premises and equipment ( 2,353 ) ( 2,551 ) Right-of-use asset ( 6,493 ) ( 7,014 ) Mortgage servicing rights ( 411 ) ( 465 ) Goodwill ( 115 ) ( 115 ) Derivative transactions 44 3 Total gross deferred tax liabilities ( 14,623 ) ( 14,773 ) Net deferred tax asset $ 15,299 $ 17,990
Summary of the Change in Net Deferred Tax Asset	A summary of the change in the net deferred tax asset is as follows: For the Year Ended December 31, 2023 2022 Balance at beginning of year: $ 17,990 $ 9,985 Deferred tax expense ( 1,665 ) ( 587 ) Merger accounting — 1,853 Accumulated other comprehensive income ( 1,026 ) 6,739 Balance at end of year $ 15,299 $ 17,990

Pension and Retirement Plans (T

Pension and Retirement Plans (Tables)	12 Months Ended
Pension and Retirement Plans (Tables)	Dec. 31, 2023
Retirement Benefits [Abstract]
Components of Projected Benefit Obligations and Funded Status	Projected benefit obligations and funded status were as follows: Pension Plan Supplemental 2023 2022 2023 2022 (dollars in thousands) Change in projected benefit obligation Obligation at beginning of year $ 35,598 $ 47,875 $ 8,060 $ 10,075 Service cost — — 273 399 Interest cost 1,806 1,309 399 260 Actuarial (gain) loss 1,175 ( 11,754 ) 81 ( 2,057 ) Benefits paid ( 1,937 ) ( 1,832 ) ( 616 ) ( 617 ) Obligation at end of year 36,642 35,598 8,197 8,060 Change in plan assets Fair value at beginning of year 50,349 60,638 — — Actual return on plan assets 5,716 ( 8,457 ) — — Employer contribution — — 616 617 Benefits paid ( 1,937 ) ( 1,832 ) ( 616 ) ( 617 ) Fair value at end of year 54,128 50,349 — — Funded status at end of year $ 17,486 $ 14,751 $ ( 8,197 ) $ ( 8,060 )
Schedule of Accumulated Benefit Obligation	Pension Plan Supplemental 2023 2022 2023 2022 (dollars in thousands) Accumulated benefit obligation $ 36,642 $ 35,598 $ 7,823 $ 7,627
Schedule of Amounts Recognized in Accumulated Other Comprehensive Income (Loss)	Amounts recognized in accumulated other comprehensive income (loss) consisted of: Pension Plan Supplemental 2023 2022 2023 2022 (dollars in thousands) Net actuarial (gain) loss $ ( 964 ) $ 373 $ ( 535 ) $ ( 617 ) Total $ ( 964 ) $ 373 $ ( 535 ) $ ( 617 )
Components of Net Periodic Benefit Cost and Amounts Recognized in Other Comprehensive Income/ (Loss)	The components of net periodic benefit cost and amounts recognized in other comprehensive income (loss) were as follows: Pension Plan Supplemental 2023 2022 2023 2022 (dollars in thousands) Net periodic benefit cost Service cost $ — $ — $ 273 $ 399 Interest cost 1,806 1,309 399 260 Expected return on assets ( 3,204 ) ( 3,876 ) — — Amortization of net actuarial loss — — — 28 Net periodic expense (benefit) ( 1,398 ) ( 2,567 ) 672 687 Amounts recognized in other comprehensive income (loss) Net actuarial loss/(gain) ( 1,337 ) 579 81 ( 2,057 ) Amortization of net actuarial loss — — — ( 28 ) Total recognized in other comprehensive income (loss) ( 1,337 ) 579 81 ( 2,085 ) Total recognized in net periodic expense (benefit) and other $ ( 2,735 ) $ ( 1,988 ) $ 753 $ ( 1,398 )
Schedule of Weighted-average Assumptions Used to Determine Projected Benefit Obligations and Net Periodic Benefit Cost	Weighted-average assumptions used to determine projected benefit obligations are as follows: Pension Plan Supplemental 2023 2022 2023 2022 Discount rate 5.00 % 5.22 % 4.95 % 5.15 % Rate of compensation increase N/A N/A 4.00 % 4.00 % Weighted-average assumptions used to determine the net periodic benefit cost in each year were as follows: Pension Plan Supplemental 2023 2022 2023 2022 Discount rate 5.22 % 2.79 % 5.15 % 2.63 % Expected long-term return on plan assets 6.50 % 6.50 % N/A N/A Rate of compensation increase N/A N/A 4.00 % 4.00 %
Schedule of Pension Plan Weighted-average Asset Allocations by Asset	The Company’s Pension Plan weighted-average asset allocations by asset category were as follows: December 31, 2023 2022 Equity securities 45 % 60 % Debt securities 20 33 Cash and equivalents 35 7 Total 100 % 100 %
Summary of Various Categories of Pension Plan Assets	The following table summarizes the various categories of the Pension Plan’s assets: Fair Value as of December 31, 2023 Level 1 Level 2 Level 3 Total (dollars in thousands) Asset category Cash and cash equivalents $ 18,755 $ — $ — $ 18,755 Fixed income — 8,129 — 8,129 Equity securities Mutual funds Domestic equity 15,285 — — 15,285 International 2,798 — — 2,798 Domestic fixed income 9,161 — — 9,161 Total $ 45,999 $ 8,129 $ — $ 54,128 Fair Value as of December 31, 2022 Level 1 Level 2 Level 3 Total (dollars in thousands) Asset category Cash and cash equivalents $ 3,676 $ — $ — $ 3,676 Fixed income — 12,347 — 12,347 Equity securities Mutual funds Domestic equity 24,201 — — 24,201 International 3,942 — — 3,942 Domestic fixed income 6,183 — — 6,183 Total $ 38,002 $ 12,347 $ — $ 50,349
Schedule of Benefits Expected to be Paid in the Next Ten Years	Benefits expected to be paid in the next ten years are as follows: Pension Supplemental Postretirement Total (dollars in thousands) Year-ended December 31, 2024 $ 2,207 $ 614 $ 23 $ 2,844 2025 2,287 611 24 2,922 2026 2,413 607 24 3,044 2027 2,340 602 24 2,966 2028 2,483 596 25 3,104 2029-2033 12,961 4,192 141 17,294 Total $ 24,691 $ 7,222 $ 261 $ 32,174

Share-Based Compensation (Table

Share-Based Compensation (Tables)	12 Months Ended
Share-Based Compensation (Tables)	Dec. 31, 2023
Summary of Non-vested Restricted Shares Outstanding	A summary of restricted stock outstanding as of December 31, 2023 and 2022, and changes during the years ended on those dates, is presented below: December 31, 2023 December 31, 2022 Number Weighted Number Weighted Restricted stock Non-vested at beginning of year 34,572 $ 82.19 34,622 $ 78.20 Granted 16,468 81.49 14,380 87.10 Vested ( 10,771 ) 80.94 ( 11,450 ) 76.50 Forfeited ( 2,363 ) 84.25 ( 2,980 ) 81.43 Non-vested at end of year 37,906 $ 82.11 34,572 $ 82.19
Schedule of Amounts Recognized in Consolidated Statement of Income for Restricted Stock, Time Based Restricted Stock Units and Performance Based Restricted Stock Units	The following table presents the amounts recognized in the consolidated statements of income for restricted stock, time-based restricted stock units, and performance-based restricted stock units: For the Year Ended December 31, 2023 2022 2021 (dollars in thousands) Share-based compensation expense $ 1,589 $ 2,875 $ 3,476 Related income tax benefit $ 444 $ 804 $ 970
Performance-Based Restricted Stock Units
Summary of Non-vested Restricted Stock Units Outstanding	A summary of non-vested performance-based restricted stock units outstanding as of December 31, 2023 and 2022, and changes during the years ended on those dates, is presented below: December 31, 2023 December 31, 2022 Number Weighted Number Weighted Performance-based restricted stock units Non-vested at beginning of year 72,134 $ 80.83 74,699 $ 73.59 Granted 31,744 59.19 37,263 88.18 Vested (Performance achieved) ( 27,965 ) 76.00 ( 34,248 ) 70.36 Forfeited ( 7,984 ) 73.87 ( 5,580 ) 79.92 Non-vested at end of year 67,929 $ 73.87 72,134 $ 80.83
Time Based Restricted Stock Units
Summary of Non-vested Restricted Stock Units Outstanding	A summary of non-vested time-based restricted stock units outstanding as of December 31, 2023 and December 31, 2022, and changes during the years ended on those dates, is presented below: December 31, 2023 December 31, 2022 Number Weighted Number Weighted Time-based restricted stock units Non-vested at beginning of year 13,551 $ 82.81 13,836 $ 75.91 Granted 28,946 53.94 8,796 88.18 Vested ( 7,431 ) 80.96 ( 7,417 ) 75.94 Forfeited ( 3,048 ) 63.54 ( 1,664 ) 84.40 Non-vested at end of year 32,018 $ 58.98 13,551 $ 82.81

Financial Instruments with Of_2

Financial Instruments with Off-Balance-Sheet Risk (Tables)	12 Months Ended
Financial Instruments with Off-Balance-Sheet Risk (Tables)	Dec. 31, 2023
Fair Value Disclosures [Abstract]
Summary of Off-Balance-Sheet Financial Instruments with Contractual Amounts Include Present Credit Risk	Off-balance-sheet financial instruments with contractual amounts that present credit risk include the following: December 31, 2023 December 31, 2022 (dollars in thousands) Financial instruments whose contractual amount represents credit risk: Commitments to extend credit: Unused portion of existing lines of credit $ 994,196 $ 1,073,567 Origination of new loans 18,341 25,411 Standby letters of credit 34,063 24,234 Financial instruments whose notional amount exceeds the amount of credit risk: Commitments to sell residential mortgage loans 795 250

Commitment and Contingencies (T

Commitment and Contingencies (Tables)	12 Months Ended
Commitment and Contingencies (Tables)	Dec. 31, 2023
Commitments and Contingencies Disclosure [Abstract]
Summary of Components of Operating Lease Cost and Other Related Information	The components of operating lease cost and other related information are as follows: For the Year Ended December 31, 2023 2022 2021 (dollars in thousands) Operating lease cost $ 6,849 $ 6,965 $ 6,976 Variable lease cost (cost excluded from lease payments) 27 38 13 Sublease income ( 512 ) ( 316 ) ( 65 ) Total operating lease cost $ 6,364 $ 6,687 $ 6,924 Other Information Cash paid for amounts included in the measurement of lease liabilities - operating cash flows for operating leases $ 7,370 $ 7,263 $ 7,259 Operating Lease - operating cash flows (liability reduction) 6,619 6,401 6,252 Weighted average lease term - operating leases 4.92 Years 5.45 Years 6.13 Years Weighted average discount rate - operating leases 3.01 % 3.01 % 2.94 %
Schedule of Total Minimum Lease Payments Due in Future Periods under Lease Agreements	The total minimum lease payments due in future periods under these agreements in effect at December 31, 2023 were as follows: Future Minimum December 31, 2023 Lease Payments (dollars in thousands) 2024 $ 6,959 2025 5,982 2026 4,745 2027 2,958 2028 2,589 Thereafter 3,900 Total minimum lease payments $ 27,133 Less: interest ( 1,968 ) Total lease liability $ 25,165

Shareholders' Equity (Tables)

Shareholders' Equity (Tables)	12 Months Ended
Shareholders' Equity (Tables)	Dec. 31, 2023
Equity [Abstract]
Schedule of Minimum Capital Requirements Considered Well Capitalized by FRB and FDIC	The Company’s and the Bank’s actual and required capital measures were as follows: Actual Minimum Capital Minimum To Be Amount Ratio Amount Ratio Amount Ratio (dollars in thousands) At December 31, 2023 Cambridge Bancorp: Total capital (to risk-weighted assets) $ 521,903 14.1 % $ 387,763 10.5 % N/A N/A Tier 1 capital (to risk-weighted assets) 481,198 13.0 % 313,903 8.5 % N/A N/A Common equity tier I capital (to risk-weighted assets) 481,198 13.0 % 258,508 7.0 % N/A N/A Tier 1 capital (to average assets) 481,198 8.9 % 216,281 4.0 % N/A N/A Cambridge Trust Company: Total capital (to risk-weighted assets) $ 500,355 13.6 % $ 387,727 10.5 % $ 369,264 10.0 % Tier 1 capital (to risk-weighted assets) 459,650 12.5 % 313,874 8.5 % 295,411 8.0 % Common equity tier I capital (to risk-weighted assets) 459,650 12.5 % 258,485 7.0 % 240,022 6.5 % Tier 1 capital (to average assets) 459,650 8.5 % 216,268 4.0 % 270,335 5.0 % Actual Minimum Capital Minimum To Be Amount Ratio Amount Ratio Amount Ratio (dollars in thousands) At December 31, 2022 Cambridge Bancorp: Total capital (to risk-weighted assets) $ 506,239 13.5 % $ 393,285 10.5 % N/A N/A Tier 1 capital (to risk-weighted assets) 466,369 12.5 % 318,373 8.5 % N/A N/A Common equity tier I capital (to risk-weighted assets) 466,369 12.5 % 262,190 7.0 % N/A N/A Tier 1 capital (to average assets) 466,369 8.5 % 219,309 4.0 % N/A N/A Cambridge Trust Company: Total capital (to risk-weighted assets) $ 490,175 13.1 % $ 393,246 10.5 % $ 374,520 10.0 % Tier 1 capital (to risk-weighted assets) 450,305 12.0 % 318,342 8.5 % 299,616 8.0 % Common equity tier I capital (to risk-weighted assets) 450,305 12.0 % 262,164 7.0 % 243,438 6.5 % Tier 1 capital (to average assets) 450,305 8.2 % 219,296 4.0 % 274,120 5.0 %

Comprehensive Income (Loss) (Ta

Comprehensive Income (Loss) (Tables)	12 Months Ended
Comprehensive Income (Loss) (Tables)	Dec. 31, 2023
Equity [Abstract]
Summary of Comprehensive Income(Loss)	The Company’s other comprehensive income (loss) consists of unrealized gains or losses on securities held at year-end classified as available for sale, cash flow hedges, and the component of the unfunded retirement liability computed in accordance with the requirements of ASC Topic 715, “ Compensation – Retirement Benefits. ” The before-tax and after-tax amount of each of these categories, as well as the tax (expense)/benefit of each, is summarized as follows: For the Year Ended For the Year Ended For the Year Ended Before Tax Net-of- Before Tax Net-of- Before Tax Net-of- (dollars in thousands) Available for sale securities Unrealized holding gains (losses) $ 3,073 $ ( 737 ) $ 2,336 $ ( 25,144 ) $ 6,408 $ ( 18,736 ) $ ( 6,245 ) $ 1,623 $ ( 4,622 ) Reclassification adjustment for (gains) losses realized in net income (1) — — — — — — — — — Interest rate swaps designated as cash flow hedges Unrealized holding gains (losses) ( 687 ) 192 ( 495 ) ( 2,170 ) 607 ( 1,563 ) ( 1,329 ) 370 ( 959 ) Reclassification adjustment for (gains) losses recognized in net income (2) 539 ( 150 ) 389 ( 832 ) 232 ( 600 ) ( 2,587 ) 723 ( 1,864 ) Defined benefit retirement plans Net change in retirement liability 1,186 ( 331 ) 855 1,818 ( 508 ) 1,310 5,273 ( 1,472 ) 3,801 Total other comprehensive income (loss) $ 4,111 $ ( 1,026 ) $ 3,085 $ ( 26,328 ) $ 6,739 $ ( 19,589 ) $ ( 4,888 ) $ 1,244 $ ( 3,644 ) (1) Reported in gain (loss) on disposition of investment securities line item in the Consolidated Statements of Income. (2) Reported in interest on payable loans line item in the Consolidated Statements of Income. The components of accumulated other comprehensive income are as follows: For the Year Ended For the Year Ended Before Tax Amount Deferred (tax) benefit Net-of-tax Amount Before Tax Amount Deferred (tax) benefit Net-of-tax Amount (dollars in thousands) Available for sale securities $ ( 25,538 ) $ 6,651 $ ( 18,887 ) $ ( 28,611 ) $ 7,390 $ ( 21,221 ) Interest Rate swaps designated as cash flow hedges ( 157 ) 44 ( 113 ) ( 14 ) 4 ( 10 ) Defined benefit retirement plans 1,785 ( 499 ) 1,286 600 ( 168 ) 432 Total accumulated other comprehensive income $ ( 23,910 ) $ 6,196 $ ( 17,714 ) $ ( 28,025 ) $ 7,226 $ ( 20,799 )
Summary of Components of Accumulated Other Comprehensive Income	The components of accumulated other comprehensive income are as follows: For the Year Ended For the Year Ended Before Tax Amount Deferred (tax) benefit Net-of-tax Amount Before Tax Amount Deferred (tax) benefit Net-of-tax Amount (dollars in thousands) Available for sale securities $ ( 25,538 ) $ 6,651 $ ( 18,887 ) $ ( 28,611 ) $ 7,390 $ ( 21,221 ) Interest Rate swaps designated as cash flow hedges ( 157 ) 44 ( 113 ) ( 14 ) 4 ( 10 ) Defined benefit retirement plans 1,785 ( 499 ) 1,286 600 ( 168 ) 432 Total accumulated other comprehensive income $ ( 23,910 ) $ 6,196 $ ( 17,714 ) $ ( 28,025 ) $ 7,226 $ ( 20,799 )

Earnings Per Share (Tables)

Earnings Per Share (Tables)	12 Months Ended
Earnings Per Share (Tables)	Dec. 31, 2023
Earnings Per Share [Abstract]
Summary of Reconciliation Between Basic and Diluted Earnings Per Share	The following represents a reconciliation between basic and diluted earnings per share: For the Year Ended December 31, 2023 2022 2021 (dollars in thousands, except per share data) Earnings per common share - basic: Numerator: Net income $ 34,109 $ 52,909 $ 54,024 Less dividends and undistributed earnings allocated ( 31 ) ( 257 ) ( 250 ) Net income applicable to common shareholders $ 34,078 $ 52,652 $ 53,774 Denominator: Weighted average common shares outstanding 7,828 7,163 6,926 Earnings per common share - basic $ 4.35 $ 7.35 $ 7.76 Earnings per common share - diluted: Numerator: Net income $ 34,109 $ 52,909 $ 54,024 Less dividends and undistributed earnings allocated ( 31 ) ( 257 ) ( 250 ) Net income applicable to common shareholders $ 34,078 $ 52,652 $ 53,774 Denominator: Weighted average common shares outstanding 7,828 7,163 6,926 Dilutive effect of common stock equivalents 15 51 65 Weighted average diluted common shares outstanding 7,843 7,214 6,991 Earnings per common share - diluted $ 4.34 $ 7.30 $ 7.69

Derivatives And Hedging Activ_2

Derivatives And Hedging Activities (Tables)	12 Months Ended
Derivatives And Hedging Activities (Tables)	Dec. 31, 2023
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Summary of Cumulative Basis Adjustment for Fair Value Hedges	The Company recorded the following amounts on the balance sheet related to cumulative basis adjustment for fair value hedges: Line Item in the Statement of Financial Position in Which the Hedged Item is Included Carrying Amount of the Hedged Assets/(Liabilities) Cumulative Amount of Fair Value Hedging Adjustment Included in the Carrying Amount of the Hedged Assets/(Liabilities) December 31, 2023 December 31, 2022 December 31, 2023 December 31, 2022 (dollars in thousands) Fixed rate loans $ 498,825 $ — $ 1,175 $ — Total $ 498,825 $ — $ 1,175 $ —
Summary of Fair Values of Derivative Instruments in the Company's Consolidated Balance Sheets	The following tables present the notional amount, the location, and fair values of derivative instruments in the Company’s consolidated balance sheets: December 31, 2023 Derivative Assets Derivative Liabilities Notional Amount Balance Sheet Fair Value Notional Amount Balance Sheet Fair Value (dollars in thousands) (dollars in thousands) Derivatives designated as hedging instruments Interest rate contracts-cash flow hedging relationships $ 100,000 Other Assets $ 1,284 $ — Other Liabilities $ — Interest rate contracts-fair value hedging relationships 400,000 Other Assets 1,620 100,000 Other Liabilities 485 Total derivatives designated as hedging instruments $ 2,904 $ 485 Derivatives not designated as hedging instruments Loan related derivative contracts Interest rate contracts $ 486,310 Other Assets $ 40,338 $ 486,310 Other Liabilities $ 40,338 Risk participation agreements-out to counterparties 53,847 Other Assets 18 — Other Liabilities — Risk participation agreements-in with counterparties — Other Assets — 98,779 Other Liabilities 62 Total derivatives not designated as hedging instruments $ 40,356 $ 40,400 December 31, 2022 Derivative Assets Derivative Liabilities Notional Amount Balance Sheet Fair Value Notional Amount Balance Sheet Fair Value (dollars in thousands) (dollars in thousands) Derivatives designated as hedging instruments Interest rate contracts-cash flow hedging relationships $ 250,000 Other Assets $ 1,966 $ — Other Liabilities $ — Total derivatives designated as hedging instruments $ 1,966 $ — Derivatives not designated as hedging instruments Loan related derivative contracts Interest rate contracts $ 499,619 Other Assets $ 50,784 $ 499,619 Other Liabilities $ 50,784 Risk participation agreements-out to counterparties 46,604 Other Assets 23 — Other Liabilities — Risk participation agreements-in with counterparties — Other Assets — 71,046 Other Liabilities 43 Total derivatives not designated as hedging instruments $ 50,807 $ 50,827
Summary of Changes to AOCI and AOCL as a Result of Cash Flow Hedge Accounting	The following tables present the changes to AOCI and AOCL as a result of cash flow hedge accounting as of the periods presented: Twelve Months Ended December 31, 2023 Amount of Gain or (Loss) Recognized in OCI Amount of Gain or (Loss) Recognized in OCI Included Component Amount of Gain or (Loss) Recognized in OCI Excluded Component Location of Gain or (Loss) Amount of Gain or (Loss) Reclassified from AOCL into Income Amount of Gain or (Loss) Reclassified from AOCL into Income Included Component Amount of Gain or (Loss) Reclassified from AOCL into Income Excluded Component (dollars in thousands) (dollars in thousands) Interest rate contracts $ ( 687 ) $ — $ ( 687 ) Interest Income $ ( 539 ) $ ( 96 ) $ ( 443 ) Twelve Months Ended December 31, 2022 Amount of Gain or (Loss) Recognized in OCI Amount of Gain or (Loss) Recognized in OCI - Included Component Amount of Gain or (Loss) Recognized in OCI - Excluded Component Location of Gain or (Loss) Amount of Gain or (Loss) Reclassified from AOCI into Income Amount of Gain or (Loss) Reclassified from AOCI into Income Included Component Amount of Gain or (Loss) Reclassified from AOCI into Income Excluded Component (dollars in thousands) (dollars in thousands) Interest rate contracts $ ( 2,170 ) $ 607 $ ( 1,563 ) Interest Income $ 832 $ 1,026 $ ( 194 )
Summary of Derivative Financial Instruments Not Designated as Hedging Instruments on the Consolidated Statements of Income	The following table presents the effect of the Company’s derivative financial instruments that are not designated as hedging instruments on the consolidated statements of income as of the periods presented: Amount of Gain or (Loss) Recognized in Income For the Year Ended December 31, 2023 2022 2021 Location of Gain or (Loss) (dollars in thousands) Other contracts Loan-related derivative income $ ( 86 ) $ ( 166 ) $ ( 124 )
Schedule of Financial Instruments Eligible for Offset in Consolidated Balance Sheet	The following tables present the information about financial instruments that are eligible for offset in the consolidated balance sheets as of December 31, 2023 and December 31, 2022: Gross Amounts Not Offset Gross Amounts Recognized Gross Amounts Offset Net Amounts Recognized Financial Instruments Collateral Pledged (Received) Net Amount December 31, 2023 (dollars in thousands) Offsetting of Derivative Assets Derivative Assets $ 43,260 $ — $ 43,260 $ 971 $ ( 41,319 ) $ 970 Offsetting of Derivative Liabilities Derivative Liabilities $ 40,885 $ — $ 40,885 $ 971 $ — $ 39,914 Gross Amounts Not Offset Gross Amounts Recognized Gross Amounts Offset Net Amounts Recognized Financial Instruments Collateral Pledged (Received) Net Amount December 31, 2022 (dollars in thousands) Offsetting of Derivative Assets Derivative Assets $ 52,773 $ — $ 52,773 $ 48 $ ( 52,130 ) $ 595 Offsetting of Derivative Liabilities Derivative Liabilities $ 50,827 $ — $ 50,827 $ 48 $ — $ 50,875

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	12 Months Ended
Fair Value Measurements (Tables)	Dec. 31, 2023
Fair Value Disclosures [Abstract]
Summary of Carrying Values and Estimated Fair Values of Financial Instruments	The following is a summary of the carrying values and estimated fair values of the Company’s significant financial instruments as of the dates indicated: December 31, 2023 December 31, 2022 Carrying Estimated Carrying Estimated (dollars in thousands) Financial assets Cash and cash equivalents $ 33,004 $ 33,004 $ 30,719 $ 30,719 Securities available for sale 137,838 137,838 153,416 153,416 Securities held to maturity 959,332 805,428 1,051,997 885,586 Loans, net 3,982,600 3,530,958 4,025,082 3,783,051 FHLB of Boston stock 19,056 19,056 6,264 6,264 Accrued interest receivable 15,765 15,765 14,118 14,118 Mortgage servicing rights 1,470 2,401 1,665 2,336 Interest rate contracts - cash flow hedge 1,284 1,284 1,966 1,966 Interest rate contracts - fair value hedge 1,620 1,620 — — Loan level interest rate swaps 40,338 40,338 50,784 50,784 Risk participation agreements out to counterparties 18 18 23 23 Financial liabilities Deposits, excluding wholesale deposits 4,029,511 4,026,404 4,433,817 4,429,190 Wholesale deposits 291,667 291,748 381,559 381,505 Borrowings 452,155 451,492 105,212 105,202 Interest rate contracts - fair value hedge 485 485 — — Loan level interest rate swaps 40,338 40,338 50,784 50,784 Risk participation agreements in with counterparties 62 62 43 43
Summary of Certain Assets Reported at Fair Value on a Recurring Basis	The following tables summarize certain assets reported at fair value on a recurring basis: Fair Value as of December 31, 2023 Level 1 Level 2 Level 3 Total (dollars in thousands) Measured on a recurring basis Securities available for sale U.S. GSE obligations $ — $ 20,462 $ — $ 20,462 Mortgage-backed securities — 117,376 — 117,376 Other assets Interest rate swaps with clients — 40,338 — 40,338 Risk participation agreements -out to counterparties — 18 — 18 Interest rate contracts - cash flow hedge — 1,284 — 1,284 Interest rate contracts - fair value hedge — 1,620 — 1,620 Other liabilities Interest rate swaps with counterparties — 40,338 — 40,338 Risk participation agreements-in with counterparties — 62 — 62 Interest rate contracts - fair value hedge — 485 — 485 Fair Value as of December 31, 2022 Level 1 Level 2 Level 3 Total (dollars in thousands) Measured on a recurring basis Securities available for sale U.S. GSE obligations $ — $ 19,733 $ — $ 19,733 Mortgage-backed securities — 132,683 — 132,683 Corporate debt securities — 1,000 — 1,000 Other assets Interest rate swaps with clients — 50,784 — 50,784 Risk participation agreements-out to counterparties — 23 — 23 Interest rate contracts — 1,966 — 1,966 Other liabilities Interest rate swaps with counterparties — 50,784 — 50,784 Risk participation agreements-in with counterparties — 43 — 43
Schedule of Carrying Value of Assets Measured at Fair Value on a Non-Recurring Basis	The following table presents the carrying value of assets held at December 31, 2023 and December 31, 2022, which were measured at fair value on a non-recurring basis: December 31, 2023 Level 1 Level 2 Level 3 Total (dollars in thousands) Items recorded at fair value on a non-recurring basis Assets Individually evaluated collateral dependent loans $ — $ — $ 9,675 $ 9,675 Total $ — $ — $ 9,675 $ 9,675 December 31, 2022 Level 1 Level 2 Level 3 Total (dollars in thousands) Items recorded at fair value on a non-recurring basis Assets Individually evaluated collateral dependent loans $ — $ — $ 103 $ 103 Total $ — $ — $ 103 $ 103

Condensed Financial Statement_2

Condensed Financial Statements of Parent Company (Tables)	12 Months Ended
Condensed Financial Statements of Parent Company (Tables)	Dec. 31, 2023
Condensed Financial Information Disclosure [Abstract]
Condensed Balance Sheet	Condensed Balance Sheet December 31, 2023 2022 (dollars in thousands) ASSETS Cash and cash equivalents $ 21,212 $ 15,747 Goodwill 33 33 Other assets 337 318 Investment in subsidiary 512,991 501,454 Total assets $ 534,573 $ 517,552 SHAREHOLDERS’ EQUITY Shareholders’ equity $ 534,573 $ 517,552 Total shareholders’ equity $ 534,573 $ 517,552
Condensed Statements of Income	Condensed Statements of Income For the Year Ended December 31, 2023 2022 2021 (dollars in thousands) Income Dividends from subsidiary $ 27,320 $ 24,734 $ 25,995 Total income 27,320 24,734 25,995 Expenses Interest expense — — — Other expenses 158 148 150 Total expenses 158 148 150 Income before income taxes and equity in undistributed income of subsidiary 27,162 24,586 25,845 Income tax benefit ( 43 ) ( 40 ) ( 42 ) Income of parent company 27,205 24,626 25,887 Equity in undistributed income of subsidiary 6,904 28,283 28,137 Net income $ 34,109 $ 52,909 $ 54,024
Condensed Statements of Cash Flows	Condensed Statements of Cash Flows For the Year Ended December 31, 2023 2022 2021 (dollars in thousands) CASH FLOWS FROM OPERATING ACTIVITIES: Net income $ 34,109 $ 52,909 $ 54,024 Adjustments to reconcile net income to net cash provided Deferred income tax benefit ( 43 ) ( 40 ) ( 42 ) Change in other assets, net 24 12 — Change in other liabilities, net — — 13 Undistributed income of subsidiary ( 6,904 ) ( 28,283 ) ( 28,137 ) Net cash provided by operating activities 27,186 24,598 25,858 CASH FLOWS FROM INVESTING ACTIVITIES: Net cash used in investing activities — — — CASH FLOWS FROM FINANCING ACTIVITIES: Proceeds from the issuance of common stock 599 580 519 Repurchase of common stock ( 1,334 ) ( 1,320 ) ( 1,440 ) Cash dividends paid on common stock ( 20,986 ) ( 18,414 ) ( 16,554 ) Net cash provided by/(used in) financing activities ( 21,721 ) ( 19,154 ) ( 17,475 ) Net increase (decrease) in cash 5,465 5,444 8,383 Cash at beginning of year 15,747 10,303 1,920 Cash at end of year $ 21,212 $ 15,747 $ 10,303 SUPPLEMENTAL DISCLOSURES OF CASH FLOW INFORMATION: Significant non-cash transactions Common Stock issued to shareholders due to merger $ — $ 62,850 $ —

The Business - Additional Infor

The Business - Additional Information (Details) - Cambridge Bancorp	12 Months Ended
	Dec. 31, 2023 Corporation Bank Service
Description Of Business [Line Items]
Number of core services \| Service	4
Number of wholly owned investment in corporations \| Corporation	2
Massachusetts and New Hampshire
Description Of Business [Line Items]
Number of banking office \| Bank	22

Summary of Significant Accoun_3

Summary of Significant Accounting Policies - Additional Information (Details) - USD ($)	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2018	Dec. 31, 2016
Summary Of Significant Accounting Policies [Line Items]
Lessee, operating lease, existence of option to extend	true
Impairment of goodwill recognized	$ 0	$ 0	$ 0
Defined contribution plan, employer matching contribution, percent					10%
Defined benefit pension highest consecutive plan period					3 years
Compensation cost	$ 0
Profit Sharing Plan
Summary Of Significant Accounting Policies [Line Items]
Defined contribution plan, maximum employee contribution, percent				100%
Defined contribution plan, employer matching contribution, percent				4%
Normal retirement age of employees				65 years
Commercial Mortgage
Summary Of Significant Accounting Policies [Line Items]
Percentage of loan to value ratio	75%
Minimum \| Residential Mortgage and Home Equity Loans
Summary Of Significant Accounting Policies [Line Items]
Percentage of loan to value ratio	80%
Maximum
Summary Of Significant Accounting Policies [Line Items]
Percentage of bank-owned life insurance	25%
Maximum \| Residential Mortgage and Home Equity Loans
Summary Of Significant Accounting Policies [Line Items]
Percentage of loan to value ratio	97%

Mergers - Additional Informatio

Mergers - Additional Information (Details) - USD ($) $ / shares in Units, $ in Thousands	Sep. 19, 2023	Oct. 01, 2022	Dec. 31, 2023	Dec. 31, 2022
Business Acquisition [Line Items]
Common stock, par value			$ 1	$ 1
Goodwill			$ 64,539	$ 64,539
Eastern Common Stock
Business Acquisition [Line Items]
Common stock, par value	$ 0.01
Eastern Bankshares Inc
Business Acquisition [Line Items]
Business combination, share conversion ratio	4.956%
Common stock, par value	$ 1
Northmark Bank
Business Acquisition [Line Items]
Business combination, share conversion ratio		0.995%
Total consideration paid		$ 62,800
Common stock issued related to merger		788,137
Business combination, share price		$ 79.74
Eastern Bankshares, Inc and Northmark Bank
Business Acquisition [Line Items]
Total assets acquired			428,700
Goodwill			12,600
Total liabilities assumed			$ 378,500

Cash and Cash Equivalents - Add

Cash and Cash Equivalents - Additional Information (Details) - USD ($)	Dec. 31, 2023	Dec. 31, 2022
Cash And Cash Equivalents [Line Items]
Cash and cash equivalents	$ 33,004,000	$ 30,719,000
Cash pledged as collateral to derivative counterparties	0	0
Federal Reserve Bank of Boston
Cash And Cash Equivalents [Line Items]
Reserve balance of cash and due from banks	0	0
New Hampshire
Cash And Cash Equivalents [Line Items]
Pledged amount to federal banking department	$ 500,000	$ 500,000

Investment Securities - Summary

Investment Securities - Summary of Carrying Amounts of Securities and Their Approximate Fair Values (Details) - USD ($) $ in Thousands		Dec. 31, 2023	Dec. 31, 2022
Schedule of Available for Sale Securities and Held to Maturity Securities [Line Items]
Available for sale securities, Amortized Cost		$ 163,376	$ 182,027
Available for sale securities, Gross Unrealized Gains		4	7
Available for sale securities, Gross Unrealized Losses		(25,542)	(28,618)
Total available for sale securities		137,838	153,416
Held to maturity securities, Amortized Cost		959,332	1,051,997
Held to maturity securities, Gross Unrealized Gains		41	92
Held to maturity securities, Gross Unrealized Losses		(153,945)	(166,503)
Held-to-maturity securities, fair value		805,428	885,586
Total, Amortized Cost		1,122,708	1,234,024
Total, Gross Unrealized Gains		45	99
Total, Gross Unrealized Losses		(179,487)	(195,121)
Total, Fair Value		943,266	1,039,002
U.S. Government Sponsored Enterprise Obligations
Schedule of Available for Sale Securities and Held to Maturity Securities [Line Items]
Available for sale securities, Amortized Cost		22,998	22,997
Available for sale securities, Gross Unrealized Losses		(2,536)	(3,264)
Total available for sale securities		20,462	19,733
U.S. Treasury Notes
Schedule of Available for Sale Securities and Held to Maturity Securities [Line Items]
Held to maturity securities, Amortized Cost		3,039	3,970
Held to maturity securities, Gross Unrealized Losses		(13)	(18)
Held-to-maturity securities, fair value		3,026	3,952
Corporate Debt Securities
Schedule of Available for Sale Securities and Held to Maturity Securities [Line Items]
Available for sale securities, Amortized Cost			996
Available for sale securities, Gross Unrealized Gains			4
Total available for sale securities			1,000
Held to maturity securities, Amortized Cost		250	250
Held to maturity securities, Gross Unrealized Losses		(2)	(6)
Held-to-maturity securities, fair value		248	244
Mortgage Backed Securities
Schedule of Available for Sale Securities and Held to Maturity Securities [Line Items]
Available for sale securities, Amortized Cost		140,378	158,034
Available for sale securities, Gross Unrealized Gains		4	3
Available for sale securities, Gross Unrealized Losses		(23,006)	(25,354)
Total available for sale securities	[1]	117,376	132,683
Held to maturity securities, Amortized Cost	[1]	871,426	951,372
Held to maturity securities, Gross Unrealized Gains		17	4
Held to maturity securities, Gross Unrealized Losses		(146,397)	(157,208)
Held-to-maturity securities, fair value		725,046	794,168
Municipal Securities
Schedule of Available for Sale Securities and Held to Maturity Securities [Line Items]
Held to maturity securities, Amortized Cost		84,617	96,405
Held to maturity securities, Gross Unrealized Gains		24	88
Held to maturity securities, Gross Unrealized Losses		(7,533)	(9,271)
Held-to-maturity securities, fair value		$ 77,108	$ 87,222

[1] Includes Agency mortgage-backed pass-through securities and collateralized mortgage obligations issued by U.S. Government Sponsored Enterprises (“GSEs”) and U.S. government agencies, such as FNMA, FHLMC, and GNMA that are not rated by Moody’s or Standard & Poor's. Each security contains a guarantee by the issuing GSE or agency and therefore carries an implicit guarantee of the U.S. government. These have been categorized as AAA/AA/A.

Investment Securities - Schedul

Investment Securities - Schedule of Amortized Cost and Fair Value of Investment Securities, Aggregated By Earlier of Guaranteed Call Date or Contractual Maturity (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Schedule of Available for Sale Securities and Held to Maturity Securities [Line Items]
Available for sale securities, After One, But Within Five Years, Amortized Cost	$ 21,464
Available for sale securities, After One, But Within Five Years, Fair Value	20,237
Available for sale securities, After Five, But Within Ten Years, Amortized Cost	42,207
Available for sale securities, After Five, But Within Ten Years, Fair Value	36,117
Available for sale securities, After Ten Years, Amortized Cost	99,705
Available for sale securities, After Ten Years, Fair Value	81,484
Available for sale securities, Total, Amortized Cost	163,376
Available for sale securities, Total, Fair Value	137,838
Held to maturity securities, Within One Year, Amortized Cost	4,992
Held to maturity securities, Within One Year, Fair Value	4,976
Held to maturity securities, After One, But Within Five Years, Amortized Cost	46,850
Held to maturity securities, After One, But Within Five Years, Fair Value	45,648
Held to maturity securities, After Five, But Within Ten Years, Amortized Cost	72,145
Held to maturity securities, After Five, But Within Ten Years, Fair Value	64,867
Held to maturity securities, After Ten Years, Amortized Cost	835,345
Held to maturity securities, After Ten Years, Fair Value	689,937
Held to maturity securities, Amortized Cost	959,332	$ 1,051,997
Held to maturity securities, Fair Value	805,428	885,586
Available for sale securities and Held to maturity securities, Within One Year, Amortized Cost	4,992
Available for sale securities and Held to maturity securities, Within One Year, Fair Value	4,976
Available for sale securities and Held to maturity securities, After One, But Within Five Years, Amortized Cost	68,314
Available for sale securities and Held to maturity securities, After One, But Within Five Years, Fair Value	65,885
Available for sale securities and Held to maturity securities, After Five, But Within Ten Years, Amortized Cost	114,352
Available for sale securities and Held to maturity securities, After Five, But Within Ten Years, Fair Value	100,984
Available for sale securities and Held to maturity securities, After Ten Years, Amortized Cost	935,050
Available for sale securities and Held to maturity securities, After Ten Years, Fair Value	771,421
Available for sale securities and Held to maturity securities, Total, Amortized Cost	1,122,708
Available for sale securities and Held to maturity securities, Total, Fair Value	943,266
U.S. Government Sponsored Enterprise Obligations
Schedule of Available for Sale Securities and Held to Maturity Securities [Line Items]
Available for sale securities, After One, But Within Five Years, Amortized Cost	9,998
Available for sale securities, After One, But Within Five Years, Fair Value	9,360
Available for sale securities, After Five, But Within Ten Years, Amortized Cost	5,000
Available for sale securities, After Five, But Within Ten Years, Fair Value	4,506
Available for sale securities, After Ten Years, Amortized Cost	8,000
Available for sale securities, After Ten Years, Fair Value	6,596
Available for sale securities, Total, Amortized Cost	22,998
Available for sale securities, Total, Fair Value	20,462
U.S. Treasury Notes
Schedule of Available for Sale Securities and Held to Maturity Securities [Line Items]
Held to maturity securities, Within One Year, Amortized Cost	2,076
Held to maturity securities, Within One Year, Fair Value	2,065
Held to maturity securities, After One, But Within Five Years, Amortized Cost	963
Held to maturity securities, After One, But Within Five Years, Fair Value	961
Held to maturity securities, Amortized Cost	3,039
Held to maturity securities, Fair Value	3,026
Mortgage Backed Securities
Schedule of Available for Sale Securities and Held to Maturity Securities [Line Items]
Available for sale securities, After One, But Within Five Years, Amortized Cost	11,466
Available for sale securities, After One, But Within Five Years, Fair Value	10,877
Available for sale securities, After Five, But Within Ten Years, Amortized Cost	37,207
Available for sale securities, After Five, But Within Ten Years, Fair Value	31,611
Available for sale securities, After Ten Years, Amortized Cost	91,705
Available for sale securities, After Ten Years, Fair Value	74,888
Available for sale securities, Total, Amortized Cost	140,378
Available for sale securities, Total, Fair Value	117,376
Held to maturity securities, After One, But Within Five Years, Amortized Cost	23,490
Held to maturity securities, After One, But Within Five Years, Fair Value	22,378
Held to maturity securities, After Five, But Within Ten Years, Amortized Cost	50,094
Held to maturity securities, After Five, But Within Ten Years, Fair Value	43,247
Held to maturity securities, After Ten Years, Amortized Cost	797,842
Held to maturity securities, After Ten Years, Fair Value	659,421
Held to maturity securities, Amortized Cost	871,426
Held to maturity securities, Fair Value	725,046
Corporate Debt Securities
Schedule of Available for Sale Securities and Held to Maturity Securities [Line Items]
Held to maturity securities, Within One Year, Amortized Cost	250
Held to maturity securities, Within One Year, Fair Value	248
Held to maturity securities, Amortized Cost	250
Held to maturity securities, Fair Value	248
Municipal Securities
Schedule of Available for Sale Securities and Held to Maturity Securities [Line Items]
Held to maturity securities, Within One Year, Amortized Cost	2,666
Held to maturity securities, Within One Year, Fair Value	2,663
Held to maturity securities, After One, But Within Five Years, Amortized Cost	22,397
Held to maturity securities, After One, But Within Five Years, Fair Value	22,309
Held to maturity securities, After Five, But Within Ten Years, Amortized Cost	22,051
Held to maturity securities, After Five, But Within Ten Years, Fair Value	21,620
Held to maturity securities, After Ten Years, Amortized Cost	37,503
Held to maturity securities, After Ten Years, Fair Value	30,516
Held to maturity securities, Amortized Cost	84,617	96,405
Held to maturity securities, Fair Value	$ 77,108	$ 87,222

Investment Securities - Gross U

Investment Securities - Gross Unrealized Losses of Aggregated by Investment Category and Length of Time that Individual Investment Securities have been in Continuous Loss Position (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Schedule of Available for Sale Securities and Held to Maturity Securities [Line Items]
Available for sale securities, Fair Value, Less than 12 months	$ 79	$ 52,554
Available for sale securities, Unrealized Losses, Less than 12 months	(1)	(5,375)
Available for sale securities, Fair Value, 12 months or longer	133,940	99,557
Available for sale securities, Unrealized Losses, 12 months or longer	(25,541)	(23,243)
Available for sale securities, Fair Value	134,019	152,111
Available for sale securities, Unrealized Losses	(25,542)	(28,618)
Held to maturity securities, Fair Value, Less than 12 months	18,362	286,872
Held to maturity securities, Unrealized Losses, Less than 12 months	(81)	(26,774)
Held to maturity securities, Fair Value, 12 months or longer	769,903	576,549
Held to maturity securities, Unrealized Losses, 12 months or longer	(153,864)	(139,729)
Held to maturity securities, Fair Value	788,265	863,421
Held to maturity securities, Unrealized Losses	(153,945)	(166,503)
Fair Value, Less than 12 months	18,441	339,426
Unrealized Losses, Less than 12 months	(82)	(32,149)
Fair Value, 12 months or longer	903,843	676,106
Unrealized Losses, 12 months or longer	(179,405)	(162,972)
Fair Value	922,284	1,015,532
Unrealized Losses	(179,487)	(195,121)
U.S. Government Sponsored Enterprise Obligations
Schedule of Available for Sale Securities and Held to Maturity Securities [Line Items]
Available for sale securities, Fair Value, Less than 12 months		10,722
Available for sale securities, Unrealized Losses, Less than 12 months		(2,278)
Available for sale securities, Fair Value, 12 months or longer	20,462	9,012
Available for sale securities, Unrealized Losses, 12 months or longer	(2,536)	(986)
Available for sale securities, Fair Value	20,462	19,734
Available for sale securities, Unrealized Losses	(2,536)	(3,264)
U.S. Treasury Notes
Schedule of Available for Sale Securities and Held to Maturity Securities [Line Items]
Available for sale securities, Fair Value, 12 months or longer	2,065
Held to maturity securities, Fair Value, Less than 12 months	961	3,952
Held to maturity securities, Unrealized Losses, Less than 12 months	(2)	(18)
Held to maturity securities, Unrealized Losses, 12 months or longer	(11)
Held to maturity securities, Fair Value	3,026	3,952
Held to maturity securities, Unrealized Losses	(13)	(18)
Mortgage Backed Securities
Schedule of Available for Sale Securities and Held to Maturity Securities [Line Items]
Available for sale securities, Fair Value, Less than 12 months	79	41,832
Available for sale securities, Unrealized Losses, Less than 12 months	(1)	(3,097)
Available for sale securities, Fair Value, 12 months or longer	723,042	90,545
Available for sale securities, Unrealized Losses, 12 months or longer	(23,005)	(22,257)
Available for sale securities, Fair Value	113,557	132,377
Available for sale securities, Unrealized Losses	(23,006)	(25,354)
Held to maturity securities, Fair Value, Less than 12 months		230,708
Held to maturity securities, Unrealized Losses, Less than 12 months		(22,362)
Held to maturity securities, Fair Value, 12 months or longer	113,478	562,835
Held to maturity securities, Unrealized Losses, 12 months or longer	(146,397)	(134,846)
Held to maturity securities, Fair Value	723,042	793,543
Held to maturity securities, Unrealized Losses	(146,397)	(157,208)
Corporate Debt Securities
Schedule of Available for Sale Securities and Held to Maturity Securities [Line Items]
Held to maturity securities, Fair Value, Less than 12 months		243
Held to maturity securities, Unrealized Losses, Less than 12 months		(6)
Held to maturity securities, Fair Value, 12 months or longer	248
Held to maturity securities, Unrealized Losses, 12 months or longer	(2)
Held to maturity securities, Fair Value	248	243
Held to maturity securities, Unrealized Losses	(2)	(6)
Municipal Securities
Schedule of Available for Sale Securities and Held to Maturity Securities [Line Items]
Held to maturity securities, Fair Value, Less than 12 months	17,401	51,969
Held to maturity securities, Unrealized Losses, Less than 12 months	(79)	(4,388)
Held to maturity securities, Fair Value, 12 months or longer	44,548	13,714
Held to maturity securities, Unrealized Losses, 12 months or longer	(7,454)	(4,883)
Held to maturity securities, Fair Value	61,949	65,683
Held to maturity securities, Unrealized Losses	$ (7,533)	$ (9,271)

Investment Securities - Additio

Investment Securities - Additional Information (Details)	Dec. 31, 2023 USD ($) Security
Schedule of Available for Sale Securities and Held to Maturity Securities [Line Items]
Number of debt securities with unrealized losses \| Security	415
Aggregate depreciation percentage of gross unrealized losses from amortized cost	16.30%
Percentage of unrealized dollar loss on amortized cost	22.20%
Percentage of unrealized loss on amortized cost	36.60%
Unrealized dollar loss of amortized cost basis \| $	$ 1,900,000
Unrealized loss of amortized cost basis \| $	$ 855,000
Number of investment securities pledged \| Security	0

Investment Securities - Summa_2

Investment Securities - Summary of Gains (Losses) from Sale of Investment Securities (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2022 USD ($)
Investments, Debt and Equity Securities [Abstract]
Amortized cost of securities sold	$ 19,018
Net proceeds from securities sold	$ 19,018

Investment Securities - Summa_3

Investment Securities - Summary of Credit Rating of Debt Securities Portfolio (Details) - USD ($) $ in Thousands		Dec. 31, 2023	Dec. 31, 2022
Schedule of Available for Sale Securities and Held to Maturity Securities [Line Items]
Total available for sale securities		$ 137,838	$ 153,416
Total held to maturity securities		959,332	1,051,997
Municipal Securities
Schedule of Available for Sale Securities and Held to Maturity Securities [Line Items]
Total held to maturity securities		84,617	96,405
Corporate Debt Securities
Schedule of Available for Sale Securities and Held to Maturity Securities [Line Items]
Total available for sale securities			1,000
Total held to maturity securities		250	250
U.S. Government Sponsored Enterprise Obligations
Schedule of Available for Sale Securities and Held to Maturity Securities [Line Items]
Total available for sale securities		20,462	19,733
U.S. Treasury Notes
Schedule of Available for Sale Securities and Held to Maturity Securities [Line Items]
Total held to maturity securities		3,039	3,970
Municipal Securities [Member]
Schedule of Available for Sale Securities and Held to Maturity Securities [Line Items]
Total held to maturity securities		84,617	96,405
AAA/AA/A
Schedule of Available for Sale Securities and Held to Maturity Securities [Line Items]
Total available for sale securities		137,838	152,416
Total held to maturity securities		959,332	1,051,997
AAA/AA/A \| Corporate Debt Securities
Schedule of Available for Sale Securities and Held to Maturity Securities [Line Items]
Total held to maturity securities		250	250
AAA/AA/A \| U.S. Government Sponsored Enterprise Obligations
Schedule of Available for Sale Securities and Held to Maturity Securities [Line Items]
Total available for sale securities		20,462	19,733
AAA/AA/A \| U.S. Treasury Notes
Schedule of Available for Sale Securities and Held to Maturity Securities [Line Items]
Total held to maturity securities		3,039	3,970
AAA/AA/A \| Municipal Securities [Member]
Schedule of Available for Sale Securities and Held to Maturity Securities [Line Items]
Total held to maturity securities		84,617	96,405
BBB/BB/B
Schedule of Available for Sale Securities and Held to Maturity Securities [Line Items]
Total available for sale securities			1,000
BBB/BB/B \| Corporate Debt Securities
Schedule of Available for Sale Securities and Held to Maturity Securities [Line Items]
Total available for sale securities			1,000
Mortgage Backed Securities
Schedule of Available for Sale Securities and Held to Maturity Securities [Line Items]
Total available for sale securities	[1]	117,376	132,683
Total held to maturity securities	[1]	871,426	951,372
Mortgage Backed Securities \| AAA/AA/A
Schedule of Available for Sale Securities and Held to Maturity Securities [Line Items]
Total available for sale securities	[1]	117,376	132,683
Total held to maturity securities	[1]	$ 871,426	$ 951,372

[1] Includes Agency mortgage-backed pass-through securities and collateralized mortgage obligations issued by U.S. Government Sponsored Enterprises (“GSEs”) and U.S. government agencies, such as FNMA, FHLMC, and GNMA that are not rated by Moody’s or Standard & Poor's. Each security contains a guarantee by the issuing GSE or agency and therefore carries an implicit guarantee of the U.S. government. These have been categorized as AAA/AA/A.

Loans and the Allowance for C_3

Loans and the Allowance for Credit Losses - Loans Outstanding by Category (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Loans And Leases Receivable Disclosure [Line Items]
Total loans	$ 4,021,544	$ 4,062,856
Residential Mortgage
Loans And Leases Receivable Disclosure [Line Items]
Deferred costs (fees) net of unearned fees	6,395	6,613
Total loans	1,626,264	1,648,838
Residential Mortgage \| Construction
Loans And Leases Receivable Disclosure [Line Items]
Loans outstanding by category gross	45,863	35,299
Residential Mortgage \| Mortgages - Fixed Rate
Loans And Leases Receivable Disclosure [Line Items]
Loans outstanding by category gross	813,374	902,968
Residential Mortgage \| Mortgages - Adjustable Rate
Loans And Leases Receivable Disclosure [Line Items]
Loans outstanding by category gross	760,632	703,958
Commercial Mortgage
Loans And Leases Receivable Disclosure [Line Items]
Deferred costs (fees) net of unearned fees	2,410	2,318
Total loans	1,931,473	1,914,423
Commercial Mortgage \| Construction
Loans And Leases Receivable Disclosure [Line Items]
Loans outstanding by category gross	113,133	135,782
Commercial Mortgage \| Mortgages - Non-owner Occupied
Loans And Leases Receivable Disclosure [Line Items]
Loans outstanding by category gross	1,648,408	1,592,732
Commercial Mortgage \| Mortgages - Owner Occupied
Loans And Leases Receivable Disclosure [Line Items]
Loans outstanding by category gross	167,522	183,591
Home Equity
Loans And Leases Receivable Disclosure [Line Items]
Deferred costs (fees) net of unearned fees	240	292
Total loans	95,649	111,351
Home Equity \| Home Equity - Lines of Credit
Loans And Leases Receivable Disclosure [Line Items]
Loans outstanding by category gross	92,730	108,961
Home Equity \| Home Equity - Term Loans
Loans And Leases Receivable Disclosure [Line Items]
Loans outstanding by category gross	2,679	2,098
Commercial and Industrial
Loans And Leases Receivable Disclosure [Line Items]
Loans outstanding by category gross	342,475	349,026
Unearned fees, net of deferred costs	583	240
Total loans	343,711	350,650
Commercial and Industrial \| Paycheck Protection Program Loans
Loans And Leases Receivable Disclosure [Line Items]
Loans outstanding by category gross	653	1,384
Consumer
Loans And Leases Receivable Disclosure [Line Items]
Deferred costs (fees) net of unearned fees	33	18
Total loans	24,447	37,594
Consumer \| Secured
Loans And Leases Receivable Disclosure [Line Items]
Loans outstanding by category gross	22,592	35,679
Consumer \| Unsecured
Loans And Leases Receivable Disclosure [Line Items]
Loans outstanding by category gross	$ 1,822	$ 1,897

Loans and the Allowance for C_4

Loans and the Allowance for Credit Losses - Additional Information (Details)	12 Months Ended
	Dec. 31, 2023 USD ($) Loan	Dec. 31, 2022 USD ($) Loan	Dec. 31, 2021 USD ($)
Financing Receivable Modifications [Line Items]
Commitments to lend additional funds to borrowers whose loans were on non-accrual status	$ 0	$ 0
Number of loans modified during the period \| Loan		0
Number of loans determined to be troubled debt restructurings \| Loan		4
Number of TDRs defaulted during the period \| Loan		0
Allowance for credit losses	40,704,000	$ 39,870,000
Number of loans in process of foreclosure \| Loan		0
Loans in deferral	0
Loans 90 days or more past due and still accruing	$ 51,000
Number of loans 90 days past \| Loan	2
Financing Receivable, Accrued Interest, after Allowance for Credit Loss, Statement of Financial Position [Extensible Enumeration]	Interest Receivable	Interest Receivable	Interest Receivable
Accrued interest receivable excluded from amortized cost and allowance for credit loss	$ 13,500,000	$ 11,600,000	$ 6,800,000
Residential Mortgage
Financing Receivable Modifications [Line Items]
Number of loans in process of foreclosure \| Loan	2
Loans in process of foreclosure, carrying value	$ 1,500,000
Troubled Debt Restructurings
Financing Receivable Modifications [Line Items]
Troubled debt restructuring carrying value		$ 704,000

Loans and the Allowance for C_5

Loans and the Allowance for Credit Losses - Non-performing Loans Disaggregated by Loan Category (Details) - Non-Performing Loans - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Financing Receivable Recorded Investment Past Due [Line Items]
Non-accrual loans	$ 16,516	$ 5,839
Loans past due >90 days, but still accruing	51
Troubled debt restructurings		703
Total	16,567	6,542
Residential Mortgage
Financing Receivable Recorded Investment Past Due [Line Items]
Non-accrual loans	6,412	4,733
Troubled debt restructurings		622
Total	6,412	5,355
Commercial Mortgage
Financing Receivable Recorded Investment Past Due [Line Items]
Non-accrual loans	9,758	311
Total	9,758	311
Home Equity
Financing Receivable Recorded Investment Past Due [Line Items]
Non-accrual loans	285	722
Total	285	722
Commercial and Industrial
Financing Receivable Recorded Investment Past Due [Line Items]
Non-accrual loans	61	73
Loans past due >90 days, but still accruing	51
Troubled debt restructurings		81
Total	$ 112	$ 154

Loans and the Allowance for C_6

Loans and the Allowance for Credit Losses - Schedule of Amortized Costs Basis and Related Reserve Amount (Details) - Collateral Pledged - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Financing Receivable, Credit Quality Indicator [Line Items]
Amortized Cost Basis	$ 9,675	$ 103
Reserve Amount	2,388	82
Commercial Mortgage
Financing Receivable, Credit Quality Indicator [Line Items]
Amortized Cost Basis	9,611
Reserve Amount	2,345
Commercial & Industrial
Financing Receivable, Credit Quality Indicator [Line Items]
Amortized Cost Basis	64	103
Reserve Amount	$ 43	$ 82

Loans and the Allowance for C_7

Loans and the Allowance for Credit Losses - Loans Receivable Disaggregated by Credit Quality Indicator (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Residential Mortgage
Financing Receivable Recorded Investment [Line Items]
2023	$ 92,911	$ 339,634
2022	331,817	531,147
2021	507,677	294,576
2020	275,181	119,729
2019	113,205	84,899
Prior	305,473	278,853
Total	1,626,264	1,648,838
Residential Mortgage \| Current
Financing Receivable Recorded Investment [Line Items]
2023	92,911	339,634
2022	331,817	531,147
2021	507,677	294,370
2020	274,988	119,414
2019	111,715	84,215
Prior	300,744	274,703
Total	1,619,852	1,643,483
Residential Mortgage \| Non-Performing Loans
Financing Receivable Recorded Investment [Line Items]
2021		206
2020	193	315
2019	1,490	684
Prior	4,729	4,150
Total	6,412	5,355
Home Equity
Financing Receivable Recorded Investment [Line Items]
2023	8,085	5,291
2022	2,469	2,958
2021	2,241	1,349
2020	1,399	1,541
2019	2,587	867
Prior	14,901	479
Revolving loans amortized cost basis	63,967	98,866
Total	95,649	111,351
Home Equity \| Current
Financing Receivable Recorded Investment [Line Items]
2023	8,085	5,291
2022	2,411	2,958
2021	2,241	1,349
2020	1,399	1,541
2019	2,587	867
Prior	14,674	479
Revolving loans amortized cost basis	63,967	98,144
Total	95,364	110,629
Home Equity \| Non-Performing Loans
Financing Receivable Recorded Investment [Line Items]
2022	58
Prior	227
Revolving loans amortized cost basis		722
Total	285	722
Consumer
Financing Receivable Recorded Investment [Line Items]
2023	7,281	13,263
2022	7,459	8,573
2021	1,706	5,602
2020	2,841	836
2019	694	2,092
Prior	3,842	6,631
Current period gross write-offs	67
Revolving loans amortized cost basis	624	597
Total	24,447	37,594
Consumer \| Current
Financing Receivable Recorded Investment [Line Items]
2023	7,281	13,263
2022	7,459	8,573
2021	1,706	5,602
2020	2,841	836
2019	694	2,092
Prior	3,842	6,631
Revolving loans amortized cost basis	624	597
Total	24,447	37,594
Commercial Mortgage
Financing Receivable Recorded Investment [Line Items]
2023	71,462	448,919
2022	469,678	366,414
2021	360,331	244,585
2020	228,501	311,477
2019	306,766	153,112
Prior	494,735	389,916
Total	1,931,473	1,914,423
Commercial Mortgage \| 1-6 (Pass)
Financing Receivable Recorded Investment [Line Items]
2023	69,636	448,919
2022	466,760	366,414
2021	360,331	240,023
2020	226,994	269,899
2019	258,296	131,415
Prior	459,472	383,473
Total	1,841,489	1,840,143
Commercial Mortgage \| 7 (Special Mention)
Financing Receivable Recorded Investment [Line Items]
2023	1,826
2022	1,822
2021		4,562
2020	1,507	41,578
2019	48,470	21,697
Prior	25,493	6,132
Total	79,118	73,969
Commercial Mortgage \| 8 (Substandard)
Financing Receivable Recorded Investment [Line Items]
2022	1,096
Prior	9,770	311
Total	10,866	311
Commercial and Industrial
Financing Receivable Recorded Investment [Line Items]
2023	43,448	130,418
2022	133,872	73,241
2021	46,770	66,148
2020	54,383	31,806
2019	23,902	21,037
Prior	40,890	27,515
Current period gross write-offs	62
Revolving loans amortized cost basis	446	485
Total	343,711	350,650
Commercial and Industrial \| 1-6 (Pass)
Financing Receivable Recorded Investment [Line Items]
2023	43,388	130,418
2022	107,494	69,030
2021	46,678	65,390
2020	50,660	29,543
2019	22,325	20,549
Prior	40,647	27,310
Revolving loans amortized cost basis	436	475
Total	311,628	342,715
Commercial and Industrial \| 7 (Special Mention)
Financing Receivable Recorded Investment [Line Items]
2023	60
2022	25,057	4,211
2021	92	130
2020	3,467	161
2019	2	407
Prior	121	121
Revolving loans amortized cost basis	10	10
Total	28,809	5,040
Commercial and Industrial \| 8 (Substandard)
Financing Receivable Recorded Investment [Line Items]
2022	1,321
2021		628
2020	256	2,102
2019	1,575	81
Prior	122	84
Total	$ 3,274	$ 2,895

Loans and the Allowance for C_8

Loans and the Allowance for Credit Losses - Schedule of Loans Receivable Disaggregated by Past Due Status (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Financing Receivable Allowance For Credit Losses [Line Items]
Total Principal Balance/Past Due	$ 3,994,982	$ 4,046,250
Total loans	4,021,544	4,062,856
30-59 Days Past Due
Financing Receivable Allowance For Credit Losses [Line Items]
Total Principal Balance/Past Due	22,236	12,467
60-89 Days Past Due
Financing Receivable Allowance For Credit Losses [Line Items]
Total Principal Balance/Past Due	1,720	2,116
90 Days or Greater
Financing Receivable Allowance For Credit Losses [Line Items]
Total Principal Balance/Past Due	2,606	2,023
Total Past Due
Financing Receivable Allowance For Credit Losses [Line Items]
Total Principal Balance/Past Due	26,562	16,606
Residential Mortgage
Financing Receivable Allowance For Credit Losses [Line Items]
Total Principal Balance/Past Due	1,605,714	1,634,216
Total loans	1,626,264	1,648,838
Residential Mortgage \| 30-59 Days Past Due
Financing Receivable Allowance For Credit Losses [Line Items]
Total Principal Balance/Past Due	16,768	11,359
Residential Mortgage \| 60-89 Days Past Due
Financing Receivable Allowance For Credit Losses [Line Items]
Total Principal Balance/Past Due	1,234	1,454
Residential Mortgage \| 90 Days or Greater
Financing Receivable Allowance For Credit Losses [Line Items]
Total Principal Balance/Past Due	2,548	1,809
Residential Mortgage \| Total Past Due
Financing Receivable Allowance For Credit Losses [Line Items]
Total Principal Balance/Past Due	20,550	14,622
Commercial Mortgage
Financing Receivable Allowance For Credit Losses [Line Items]
Total Principal Balance/Past Due	1,929,588	1,914,423
Total loans	1,931,473	1,914,423
Commercial Mortgage \| 30-59 Days Past Due
Financing Receivable Allowance For Credit Losses [Line Items]
Total Principal Balance/Past Due	1,885
Commercial Mortgage \| Total Past Due
Financing Receivable Allowance For Credit Losses [Line Items]
Total Principal Balance/Past Due	1,885
Home Equity
Financing Receivable Allowance For Credit Losses [Line Items]
Total Principal Balance/Past Due	93,623	109,782
Total loans	95,649	111,351
Home Equity \| 30-59 Days Past Due
Financing Receivable Allowance For Credit Losses [Line Items]
Total Principal Balance/Past Due	1,855	962
Home Equity \| 60-89 Days Past Due
Financing Receivable Allowance For Credit Losses [Line Items]
Total Principal Balance/Past Due	171	393
Home Equity \| 90 Days or Greater
Financing Receivable Allowance For Credit Losses [Line Items]
Total Principal Balance/Past Due		214
Home Equity \| Total Past Due
Financing Receivable Allowance For Credit Losses [Line Items]
Total Principal Balance/Past Due	2,026	1,569
Commercial and Industrial
Financing Receivable Allowance For Credit Losses [Line Items]
Total Principal Balance/Past Due	341,875	350,316
Total loans	343,711	350,650
Commercial and Industrial \| 30-59 Days Past Due
Financing Receivable Allowance For Credit Losses [Line Items]
Total Principal Balance/Past Due	1,477	65
Commercial and Industrial \| 60-89 Days Past Due
Financing Receivable Allowance For Credit Losses [Line Items]
Total Principal Balance/Past Due	301	269
Commercial and Industrial \| 90 Days or Greater
Financing Receivable Allowance For Credit Losses [Line Items]
Total Principal Balance/Past Due	58
Commercial and Industrial \| Total Past Due
Financing Receivable Allowance For Credit Losses [Line Items]
Total Principal Balance/Past Due	1,836	334
Consumer
Financing Receivable Allowance For Credit Losses [Line Items]
Total Principal Balance/Past Due	24,182	37,513
Total loans	24,447	37,594
Consumer \| 30-59 Days Past Due
Financing Receivable Allowance For Credit Losses [Line Items]
Total Principal Balance/Past Due	251	81
Consumer \| 60-89 Days Past Due
Financing Receivable Allowance For Credit Losses [Line Items]
Total Principal Balance/Past Due	14
Consumer \| Total Past Due
Financing Receivable Allowance For Credit Losses [Line Items]
Total Principal Balance/Past Due	$ 265	$ 81

Loans and the Allowance for C_9

Loans and the Allowance for Credit Losses - Summary of Changes in Allowance for Credit Losses Disaggregated by Loan Category (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Financing Receivable Allowance For Credit Losses [Line Items]
Allowance for credit losses-loan portfolio, Beginning Balance	$ 39,870
Provision for (release of) credit losses - unfunded commitments	904	$ 3,881	$ (1,294)
Allowance for credit losses-loan portfolio, Ending Balance	40,704	39,870
Funded Commitments
Financing Receivable Allowance For Credit Losses [Line Items]
Allowance for credit losses-loan portfolio, Beginning Balance	37,774	34,496
Provision for acquired loans		2,102
Initial allowance for PCD		56
Charge-offs	(129)	(52)
Recoveries	59	105
Provision for (release of) credit losses - loan portfolio	1,240	1,067
Allowance for credit losses-loan portfolio, Ending Balance	38,944	37,774	34,496
Unfunded Commitments
Financing Receivable Allowance For Credit Losses [Line Items]
Allowance for credit losses-loan portfolio, Beginning Balance	2,096	1,384
Acquired loan commitments		137
Provision for (release of) credit losses - unfunded commitments	(336)	575
Allowance for credit losses-unfunded commitments	1,760	2,096
Allowance for credit losses-loan portfolio, Ending Balance		2,096	1,384
Residential Mortgage
Financing Receivable Allowance For Credit Losses [Line Items]
Allowance for credit losses-loan portfolio, Beginning Balance	13,321
Allowance for credit losses-loan portfolio, Ending Balance	8,399	13,321
Residential Mortgage \| Funded Commitments
Financing Receivable Allowance For Credit Losses [Line Items]
Allowance for credit losses-loan portfolio, Beginning Balance	13,321	13,383
Provision for acquired loans		527
Initial allowance for PCD		19
Recoveries		4
Provision for (release of) credit losses - loan portfolio	(4,922)	(612)
Allowance for credit losses-loan portfolio, Ending Balance	8,399	13,321	13,383
Commercial Mortgage
Financing Receivable Allowance For Credit Losses [Line Items]
Allowance for credit losses-loan portfolio, Beginning Balance	19,086
Allowance for credit losses-loan portfolio, Ending Balance	24,452	19,086
Commercial Mortgage \| Funded Commitments
Financing Receivable Allowance For Credit Losses [Line Items]
Allowance for credit losses-loan portfolio, Beginning Balance	19,086	17,133
Provision for acquired loans		1,337
Initial allowance for PCD		37
Provision for (release of) credit losses - loan portfolio	5,366	579
Allowance for credit losses-loan portfolio, Ending Balance	24,452	19,086	17,133
Home Equity
Financing Receivable Allowance For Credit Losses [Line Items]
Allowance for credit losses-loan portfolio, Beginning Balance	573
Allowance for credit losses-loan portfolio, Ending Balance	580	573
Home Equity \| Funded Commitments
Financing Receivable Allowance For Credit Losses [Line Items]
Allowance for credit losses-loan portfolio, Beginning Balance	573	406
Provision for acquired loans		117
Provision for (release of) credit losses - loan portfolio	7	50
Allowance for credit losses-loan portfolio, Ending Balance	580	573	406
Commercial & Industrial
Financing Receivable Allowance For Credit Losses [Line Items]
Allowance for credit losses-loan portfolio, Beginning Balance	4,153
Allowance for credit losses-loan portfolio, Ending Balance	4,940	4,153
Commercial & Industrial \| Funded Commitments
Financing Receivable Allowance For Credit Losses [Line Items]
Allowance for credit losses-loan portfolio, Beginning Balance	4,153	2,989
Provision for acquired loans		113
Charge-offs	(62)	(23)
Recoveries	37	89
Provision for (release of) credit losses - loan portfolio	812	985
Allowance for credit losses-loan portfolio, Ending Balance	4,940	4,153	2,989
Consumer
Financing Receivable Allowance For Credit Losses [Line Items]
Allowance for credit losses-loan portfolio, Beginning Balance	641
Allowance for credit losses-loan portfolio, Ending Balance	573	641
Consumer \| Funded Commitments
Financing Receivable Allowance For Credit Losses [Line Items]
Allowance for credit losses-loan portfolio, Beginning Balance	641	585
Provision for acquired loans		8
Charge-offs	(67)	(29)
Recoveries	22	12
Provision for (release of) credit losses - loan portfolio	(23)	65
Allowance for credit losses-loan portfolio, Ending Balance	573	641	585
Unfunded Commitments
Financing Receivable Allowance For Credit Losses [Line Items]
Allowance for credit losses-loan portfolio, Ending Balance	1,760
Unfunded Commitments \| Unfunded Commitments
Financing Receivable Allowance For Credit Losses [Line Items]
Allowance for credit losses-loan portfolio, Beginning Balance	2,096	1,384
Acquired loan commitments		137
Provision for (release of) credit losses - unfunded commitments	(336)	575
Allowance for credit losses-unfunded commitments	$ 1,760	2,096
Allowance for credit losses-loan portfolio, Ending Balance		$ 2,096	$ 1,384

Federal Home Loan Bank ("FHLB_2

Federal Home Loan Bank ("FHLB") of Boston Stock - Additional Information (Details) - USD ($)	Dec. 31, 2023	Dec. 31, 2022
Federal Home Loan Bank ("FHLB") Stock [Line Items]
Federal Home Loan Bank ("FHLB") of Boston Stock, at cost	$ 19,056,000	$ 6,264,000
Federal Home Loan Bank ("FHLB") of Boston
Federal Home Loan Bank ("FHLB") Stock [Line Items]
Federal Home Loan Bank ("FHLB") of Boston Stock, at cost	19,100,000	6,300,000
Impairment on investment of federal home loan bank ("FHLB") stock	$ 0	$ 0

Banking Premises and Equipmen_2

Banking Premises and Equipment - Summary of Cost and Accumulated Depreciation and Amortization of Property, Leasehold Improvements and Equipment (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Property Plant And Equipment [Line Items]
Banking premises and equipment, Subtotal	$ 50,591	$ 49,171
Accumulated depreciation and amortization	(28,838)	(25,874)
Total	21,753	23,297
Land
Property Plant And Equipment [Line Items]
Banking premises and equipment, Subtotal	3,396	3,396
Building and leasehold improvements
Property Plant And Equipment [Line Items]
Banking premises and equipment, Subtotal	$ 25,586	25,588
Building and leasehold improvements \| Minimum
Property Plant And Equipment [Line Items]
Estimated Useful Lives	3 years
Building and leasehold improvements \| Maximum
Property Plant And Equipment [Line Items]
Estimated Useful Lives	30 years
Equipment, including vaults
Property Plant And Equipment [Line Items]
Banking premises and equipment, Subtotal	$ 21,460	20,165
Equipment, including vaults \| Minimum
Property Plant And Equipment [Line Items]
Estimated Useful Lives	3 years
Equipment, including vaults \| Maximum
Property Plant And Equipment [Line Items]
Estimated Useful Lives	20 years
Work in process
Property Plant And Equipment [Line Items]
Banking premises and equipment, Subtotal	$ 149	$ 22

Banking Premises and Equipmen_3

Banking Premises and Equipment - Additional Information (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Property, Plant and Equipment [Abstract]
Depreciation expense	$ 2.8	$ 2.7	$ 2.6

Intangible Assets - Additional

Intangible Assets - Additional Information (Details) - USD ($)	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Finite Lived Intangible Assets [Line Items]
Carrying value of intangible asset	$ 6,550,000	$ 7,443,000
Servicing mortgage loans sold	$ 173,900,000	$ 191,900,000
Mortgage Servicing Rights
Finite Lived Intangible Assets [Line Items]
Weighted average amortization period	7 years 9 months 18 days	7 years 1 month 6 days
Amount of mortgage loans sold and servicing rights retained	$ 6,400,000	$ 5,800,000	$ 25,300,000
Fair value of mortgage servicing rights portfolio	2,400,000	2,300,000
North Mark Merger \| Core Deposit Intangibles
Finite Lived Intangible Assets [Line Items]
Amortization of intangible asset	893,000	494,000	$ 361,000
Carrying value of intangible asset	$ 6,500,000	$ 7,400,000
Weighted average amortization period	7 years 8 months 12 days	8 years 8 months 12 days

Intangible Assets - Schedule of

Intangible Assets - Schedule of Mortgage Servicing Rights (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Finite-Lived Intangible Assets [Line Items]
Beginning Balance, Mortgage servicing rights	$ 1,665	$ 1,083	$ 1,361
Mortgage servicing rights capitalized, Mortgage servicing rights	74	71	281
Amortization charged against servicing income, Mortgage servicing rights	(269)	(274)	(559)
Ending Balance, Mortgage servicing rights	1,470	1,665	1,083
Beginning Balance, Valuation allowance			(142)
Change in impairment reserve, Valuation allowance			142
Beginning Balance, Total	1,665	1,083	1,219
Mortgage servicing rights capitalized, Total	74	71	281
Amortization charged against servicing income, Total	$ (269)	(274)	(559)
Change in impairment reserve, Total			142
Ending Balance, Total		1,665	$ 1,083
North Mark Merger
Finite-Lived Intangible Assets [Line Items]
Mortgage servicing rights acquired as a result of the merger, Mortgage servicing rights		785
Mortgage servicing rights acquired as a result of the merger, Total		$ 785

Intangible Assets - Schedule _2

Intangible Assets - Schedule of Aggregate Estimated Future Amortization Expense (Details) - Mortgage Servicing Rights $ in Thousands	Dec. 31, 2023 USD ($)
Future Amortization Expense
2024	$ 173
2025	153
2026	136
2027	121
2028	109
Thereafter	778
Total	$ 1,470

Deposits - Summary of Deposits

Deposits - Summary of Deposits (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Deposits [Abstract]
Demand deposits (non-interest bearing)	$ 1,032,413	$ 1,366,395
Interest bearing checking	1,132,518	908,961
Money market	983,480	1,162,773
Savings	498,386	790,628
Retail certificates of deposit under $250,000	212,694	117,532
Retail certificates of deposit $250,000 or greater	170,020	87,528
Brokered certificates of deposit	291,667	381,559
Total deposits	$ 4,321,178	$ 4,815,376

Deposits - Schedule of Maturiti

Deposits - Schedule of Maturities (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Deposits [Abstract]
2023		$ 533,513
2024	$ 655,266	39,753
2025	11,388	5,377
2026	5,918	6,021
2027	1,315	1,955
2028 and after	494
Total certificates of deposit	$ 674,381	$ 586,619

Deposits - Additional Informati

Deposits - Additional Information (Detail) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Deposits [Abstract]
Deposit accounts of directors, executive officers and their respective affiliates	$ 1.7	$ 2.7

Borrowings - Additional Informa

Borrowings - Additional Information (Details) - USD ($)	12 Months Ended
Borrowings - Additional Information (Details) - USD ($)	Dec. 31, 2023	Dec. 31, 2022
Debt Instrument [Line Items]
Short-term advances outstanding from FHLB of boston	$ 406,000,000	$ 100,200,000
Weighted average interest rate	5.38%	4.38%
Long-term advances outstanding from FHLB of boston	$ 452,155,000	$ 100,176,000
Long-term advances outstanding from FHLB of boston	$ 46,200,000	0
Weighted average interest rate	4.17%
Repurchase agreement	$ 0	5,000,000
Average balance of securities sold under agreements to repurchase	1,700,000	1,200,000
Borrowings under PPP loan	0	0
Unused borrowing capacity based upon collateral pledged	$ 532,000,000
Minimum
Debt Instrument [Line Items]
Percentage of carrying value, secured blanket lien on qualified collateral	60%
Maximum
Debt Instrument [Line Items]
Percentage of carrying value, secured blanket lien on qualified collateral	70%
Federal Home Loan Bank ("FHLB") of Boston \| Short-term Advances
Debt Instrument [Line Items]
Average daily balance for short-term advances	$ 157,100,000	68,400,000
Highest month-end balance	406,000,000	279,000,000
Investment Securities Commercial Real Estate and Commercial and Industrial Loans \| Line of Credit
Debt Instrument [Line Items]
Collateral pledged amount	2,110,000,000	970,100,000
FRB Boston \| Investment Securities Commercial Real Estate and Commercial and Industrial Loans
Debt Instrument [Line Items]
Line of credit unused borrowing capacity	$ 1,760,000,000	$ 680,400,000

Borrowings - Schedule of Inform

Borrowings - Schedule of Information Relating to Borrowings and Weighted Average Interest Rates (Details) - USD ($) $ in Thousands		Dec. 31, 2023	Dec. 31, 2022
Federal Home Loan Bank Advances [Line Items]
FHLB of Boston long-term borrowings		$ 452,155	$ 100,176
FHLB of Boston long-term borrowings, percentage		5.26%	4.38%
Within One Year
Federal Home Loan Bank Advances [Line Items]
FHLB of Boston long-term borrowings		$ 406,000	$ 100,176
FHLB of Boston long-term borrowings, percentage		5.38%	4.38%
Over One Year To Three Years
Federal Home Loan Bank Advances [Line Items]
FHLB of Boston long-term borrowings		$ 45,000
FHLB of Boston long-term borrowings, percentage		4.27%	0%
Over Three Years To Five Years
Federal Home Loan Bank Advances [Line Items]
FHLB of Boston long-term borrowings	[1]	$ 717
FHLB of Boston long-term borrowings, percentage	[1]	0%	0%
Over Five Years
Federal Home Loan Bank Advances [Line Items]
FHLB of Boston long-term borrowings	[1]	$ 438
FHLB of Boston long-term borrowings, percentage	[1]	0%	0%

[1] (1) Includes advances under the FHLB of Boston Jobs for New England (“JNE”) program, which are zero rate borrowings.

Income Taxes - Components of In

Income Taxes - Components of Income Tax Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Current income tax expense
Federal	$ 7,740	$ 12,906	$ 11,330
State	2,895	5,559	4,862
Total current income tax expense	10,635	18,465	16,192
Deferred income tax expense
Federal	1,091	455	1,840
State	574	132	1,059
Total deferred income tax expense	1,665	587	2,899
Total income tax expense	$ 12,300	$ 19,052	$ 19,091

Income Taxes - Reconciliation o

Income Taxes - Reconciliation of Total Income Tax Expense, Calculated at Statutory Federal Income Tax Rates, to Income Tax Expense in Consolidated Statements of Income (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Income Tax Disclosure [Abstract]
Income tax expense at statutory rate of 21.0%	$ 9,746	$ 15,112	$ 15,354
Increase/(decrease) resulting from:
State tax, net of federal tax benefit	2,741	4,496	4,678
Tax-exempt income	(597)	(814)	(795)
ESOP dividends	(151)	(150)	(145)
Bank owned life insurance	(148)	(133)	(165)
Compensation limited under 162(m)	112	193	226
Benefit from stock compensation	17	(81)	(46)
Non-deductible acquisition costs	657	182	0
Non-deductible expenses	71	44	55
BOLI surrender, death benefit	0	310	0
Other	(148)	(107)	(71)
Total income tax expense	$ 12,300	$ 19,052	$ 19,091
Income tax expense at statutory rates	21%

Income Taxes - Additional Infor

Income Taxes - Additional Information (Details) - USD ($)	12 Months Ended
Income Taxes - Additional Information (Details) - USD ($)	Dec. 31, 2023	Dec. 31, 2022
Income Taxes [Line Items]
Current federal tax rates	21%
Federal and state blended tax rate, net deferred tax assets were measured	27.95%	27.95%
Deferred tax assets, valuation allowance	$ 0	$ 0
Unrecognized tax benefits	$ 0	$ 0
Federal Income Tax \| Earliest Tax Year
Income Taxes [Line Items]
Income tax returns year open and subject to examination	2020
Federal Income Tax \| Latest Tax Year
Income Taxes [Line Items]
Income tax returns year open and subject to examination	2023
State Income Tax \| Earliest Tax Year
Income Taxes [Line Items]
Income tax returns year open and subject to examination	2020
State Income Tax \| Latest Tax Year
Income Taxes [Line Items]
Income tax returns year open and subject to examination	2023

Income Taxes - Summary of Net D

Income Taxes - Summary of Net Deferred Tax Asset (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Gross deferred tax assets
Allowance for credit losses	$ 11,377	$ 11,142
Unrealized losses on available for sale securities	6,652	7,390
Incentive compensation	1,379	1,819
Equity based compensation	910	1,298
Lease liabilities	7,033	7,661
ESOP dividends	202	200
Intangibles and fair value marks (merger related)	1,841	2,322
Other	528	931
Total gross deferred tax assets	29,922	32,763
Gross deferred tax liabilities
Deferred loan origination costs	(2,835)	(2,886)
Retirement benefits	(2,460)	(1,745)
Depreciation of premises and equipment	(2,353)	(2,551)
Right of use asset	(6,493)	(7,014)
Mortgage servicing rights	(411)	(465)
Goodwill	(115)	(115)
Derivative transactions	44	3
Total gross deferred tax liabilities	(14,623)	(14,773)
Net deferred tax asset	$ 15,299	$ 17,990	$ 9,985

Income Taxes - Summary of the C

Income Taxes - Summary of the Change in Net Deferred Tax Asset (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Income Tax Disclosure [Abstract]
Balance at beginning of year	$ 17,990	$ 9,985
Deferred tax expense	(1,665)	(587)
Merger accounting	0	1,853
Accumulated other comprehensive income	(1,026)	6,739
Balance at end of year	$ 15,299	$ 17,990

Pension and Retirement Plans -

Pension and Retirement Plans - Additional Information (Details) - USD ($)	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Defined Benefit Plan Disclosure [Line Items]
Defined contribution plan, employer matching contribution, percent						10%
Transfers between fair value levels	$ 0	$ 0
Benefit obligation	$ 489,000	424,000
Minimum \| Domestic Large Cap Equities
Defined Benefit Plan Disclosure [Line Items]
Target asset allocation percentages	0%
Minimum \| Domestic Small/Mid Cap Equities
Defined Benefit Plan Disclosure [Line Items]
Target asset allocation percentages	0%
Minimum \| International and emerging Equities
Defined Benefit Plan Disclosure [Line Items]
Target asset allocation percentages	0%
Minimum \| Cash and Fixed Income
Defined Benefit Plan Disclosure [Line Items]
Target asset allocation percentages	20%
Maximum \| Domestic Large Cap Equities
Defined Benefit Plan Disclosure [Line Items]
Target asset allocation percentages	60%
Maximum \| Domestic Small/Mid Cap Equities
Defined Benefit Plan Disclosure [Line Items]
Target asset allocation percentages	20%
Maximum \| International and emerging Equities
Defined Benefit Plan Disclosure [Line Items]
Target asset allocation percentages	20%
Maximum \| Cash and Fixed Income
Defined Benefit Plan Disclosure [Line Items]
Target asset allocation percentages	0%
Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, description	The Company has a noncontributory, defined benefit pension plan (“Pension Plan”) covering substantially all employees hired before May 2, 2011. The Company also provides supplemental retirement benefits to certain current and former executive officers of the Company under the terms of Supplemental Executive Retirement Agreements (“Supplemental Retirement Plan”).
Benefit obligation	$ 36,642,000	35,598,000	$ 47,875,000
Postretirement Medical Coverage
Defined Benefit Plan Disclosure [Line Items]
Employee eligibility age under the plan					65 years
Profit Sharing Plan
Defined Benefit Plan Disclosure [Line Items]
Defined contribution plan, maximum employee contribution, percent				100%
Defined contribution plan, employer matching contribution, percent				4%
Profit Sharing Plan \| 401(k)
Defined Benefit Plan Disclosure [Line Items]
Defined contribution plan, maximum employee contribution, percent				100%
Profit Sharing Plan \| Maximum \| 401(k)
Defined Benefit Plan Disclosure [Line Items]
Defined contribution plan, employer matching contribution, percent				4%
Employee Stock Ownership Plan (ESOP)
Defined Benefit Plan Disclosure [Line Items]
Defined contribution plan, minimum number of hours of service per year required for eligibility	1000 hours
Defined contribution plan, minimum service period required for eligibility	12 months
Employee Stock Ownership Plan (ESOP) \| Minimum
Defined Benefit Plan Disclosure [Line Items]
Employee eligibility age under the plan	21 years
Profit Sharing and ESOP Plans
Defined Benefit Plan Disclosure [Line Items]
Contribution expense related to plans	$ 2,800,000	4,500,000	4,000,000
Defined Contribution SERP Plan (“DC SERP”)
Defined Benefit Plan Disclosure [Line Items]
Defined contribution plan, employer matching contribution, percent	10%
Contribution expense related to plans	$ 25,000	$ 271,000	$ 201,000

Pension and Retirement Plans _2

Pension and Retirement Plans - Schedule of Projected Benefit Obligations and Funded Status (Details) - USD ($)	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Change in projected benefit obligation
Obligation at beginning of year	$ 424,000
Obligation at end of year	489,000	$ 424,000
Pension Plan
Change in projected benefit obligation
Obligation at beginning of year	35,598,000	47,875,000
Interest cost	1,806,000	1,309,000
Actuarial (gain) loss	1,175,000	(11,754,000)
Benefits paid	(1,937,000)	(1,832,000)
Obligation at end of year	36,642,000	35,598,000
Change in plan assets
Fair value at beginning of year	50,349,000	60,638,000
Actual return on plan assets	5,716,000	(8,457,000)
Benefits paid	(1,937,000)	(1,832,000)
Fair value at end of year	54,128,000	50,349,000
Funded (underfunded) status at end of year	17,486,000	14,751,000
Supplemental Retirement Plan
Change in projected benefit obligation
Obligation at beginning of year	8,060,000	10,075,000
Service cost	273,000	399,000
Interest cost	399,000	260,000
Actuarial (gain) loss	81,000	(2,057,000)
Benefits paid	(616,000)	(617,000)
Obligation at end of year	8,197,000	8,060,000
Change in plan assets
Employer contribution	616,000	617,000
Benefits paid	(616,000)	(617,000)
Funded (underfunded) status at end of year	$ (8,197,000)	$ (8,060,000)

Pension and Retirement Plans _3

Pension and Retirement Plans - Schedule of Accumulated Benefit Obligation (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Accumulated benefit obligation	$ 36,642	$ 35,598
Supplemental Retirement Plan
Defined Benefit Plan Disclosure [Line Items]
Accumulated benefit obligation	$ 7,823	$ 7,627

Pension and Retirement Plans _4

Pension and Retirement Plans - Schedule of Amounts Recognized in Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Net actuarial (gain) loss	$ (964)	$ 373
Total	(964)	373
Supplemental Retirement Plan
Defined Benefit Plan Disclosure [Line Items]
Net actuarial (gain) loss	(535)	(617)
Total	$ (535)	$ (617)

Pension and Retirement Plans _5

Pension and Retirement Plans - Components of Net Periodic Benefit Cost and Amounts Recognized in Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Amounts recognized in other comprehensive income (loss)
Total recognized in other comprehensive income (loss)	$ (1,186)	$ (1,818)	$ (5,273)
Pension Plan
Net periodic benefit cost
Interest cost	1,806	1,309
Expected return on assets	(3,204)	(3,876)
Net periodic expense (benefit)	(1,398)	(2,567)
Amounts recognized in other comprehensive income (loss)
Net actuarial loss/(gain)	(1,337)	579
Total recognized in other comprehensive income (loss)	(1,337)	579
Total recognized in net periodic expense (benefit) and other comprehensive income (loss)	(2,735)	(1,988)
Supplemental Retirement Plan
Net periodic benefit cost
Service cost	273	399
Interest cost	$ 399	$ 260
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) Excluding Service Cost, Statement of Income or Comprehensive Income [Extensible Enumeration]	Other Comprehensive Income (Loss), Net of Tax	Other Comprehensive Income (Loss), Net of Tax
Amortization of net actuarial loss		$ 28
Net periodic expense (benefit)	$ 672	687
Amounts recognized in other comprehensive income (loss)
Net actuarial loss/(gain)	81	(2,057)
Amortization of net actuarial loss		(28)
Total recognized in other comprehensive income (loss)	81	(2,085)
Total recognized in net periodic expense (benefit) and other comprehensive income (loss)	$ 753	$ (1,398)

Pension and Retirement Plans _6

Pension and Retirement Plans - Schedule of Weighted-average Assumptions Used to Determine Projected Benefit Obligations and Net Periodic Benefit Cost (Details)	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Discount rate	5%	5.22%
Discount rate	5.22%	2.79%
Expected long-term return on plan assets	6.50%	6.50%
Supplemental Retirement Plan
Defined Benefit Plan Disclosure [Line Items]
Discount rate	4.95%	5.15%
Rate of compensation increase	4%	4%
Discount rate	5.15%	2.63%
Rate of compensation increase	4%	4%

Pension and Retirement Plans _7

Pension and Retirement Plans - Schedule of Pension Plan Weighted-average Asset Allocations by Asset (Details)	Dec. 31, 2023	Dec. 31, 2022
Defined Benefit Plan Disclosure [Line Items]
Weighted average asset allocations percentage	100%	100%
Equity Securities
Defined Benefit Plan Disclosure [Line Items]
Weighted average asset allocations percentage	45%	60%
Debt Securities
Defined Benefit Plan Disclosure [Line Items]
Weighted average asset allocations percentage	20%	33%
Cash and Equivalents
Defined Benefit Plan Disclosure [Line Items]
Weighted average asset allocations percentage	35%	7%

Pension and Retirement Plans _8

Pension and Retirement Plans - Summary of Various Categories of Pension Plan Assets (Details) - Pension Plan - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension plan assets	$ 54,128	$ 50,349	$ 60,638
Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension plan assets	45,999	38,002
Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension plan assets	8,129	12,347
Cash and Cash Equivalents
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension plan assets	18,755	3,676
Cash and Cash Equivalents \| Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension plan assets	18,755	3,676
Fixed Income
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension plan assets	8,129	12,347
Fixed Income \| Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension plan assets	8,129	12,347
Mutual Funds, Domestic Equity
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension plan assets	15,285	24,201
Mutual Funds, Domestic Equity \| Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension plan assets	15,285	24,201
Mutual Funds, International
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension plan assets	2,798	3,942
Mutual Funds, International \| Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension plan assets	2,798	3,942
Mutual Funds, Domestic Fixed Income
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension plan assets	9,161	6,183
Mutual Funds, Domestic Fixed Income \| Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension plan assets	$ 9,161	$ 6,183

Pension and Retirement Plans _9

Pension and Retirement Plans - Schedule of Benefits Expected to be Paid in the Next Ten Years (Details) $ in Thousands	Dec. 31, 2023 USD ($)
Year-ended December 31,
2024	$ 2,844
2025	2,922
2026	3,044
2027	2,966
2028	3,104
2029-2033	17,294
Total	32,174
Pension Plan
Year-ended December 31,
2024	2,207
2025	2,287
2026	2,413
2027	2,340
2028	2,483
2029-2033	12,961
Total	24,691
Supplemental Retirement Plan
Year-ended December 31,
2024	614
2025	611
2026	607
2027	602
2028	596
2029-2033	4,192
Total	7,222
Postretirement Healthcare Plan
Year-ended December 31,
2024	23
2025	24
2026	24
2027	24
2028	25
2029-2033	141
Total	$ 261

Share-Based Compensation - Addi

Share-Based Compensation - Additional Information (Details) - shares	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
DSP Plan and 2017 Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total shares issued under this plan	12,195	7,386
Restricted Stock \| Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options time-vest period	3 years
Restricted Stock \| Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options time-vest period		5 years
Performance-Based Restricted Stock Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options time-vest period	3 years
Time Based Restricted Stock Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options time-vest period	3 years

Share-Based Compensation - Summ

Share-Based Compensation - Summary of Non-vested Restricted Shares Outstanding (Details) - Restricted Stock - $ / shares	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of Shares, Non-vested at beginning of year	34,572	34,622
Number of Shares, Granted	16,468	14,380
Number of Shares, Vested	(10,771)	(11,450)
Number of Shares, Forfeited	(2,363)	(2,980)
Number of Shares, Non-vested at end of year	37,906	34,572
Weighted Average Grant Value, Non-vested at beginning of year	$ 82.19	$ 78.20
Weighted Average Grant Value, Granted	81.49	87.10
Weighted Average Grant Value, Vested	80.94	76.50
Weighted Average Grant Value, Forfeited	84.25	81.43
Weighted Average Grant Value, Non-vested at end of year	$ 82.11	$ 82.19

Share-Based Compensation - Su_2

Share-Based Compensation - Summary of Non-vested Performance-Based Restricted Stock Units Outstanding (Details) - Performance-Based Restricted Stock Units - $ / shares	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of Units, Non-vested at beginning of year	72,134	74,699
Number of Units, Granted	31,744	37,263
Number of Units, Vested (Performance achieved)	(27,965)	(34,248)
Number of Units, Forfeited	(7,984)	(5,580)
Number of Units, Non-vested at end of year	67,929	72,134
Weighted Average Grant Value, Non-vested at beginning of year	$ 80.83	$ 73.59
Weighted Average Grant Value, Granted	59.19	88.18
Weighted Average Grant Value, Vested (Performance achieved)	76	70.36
Weighted Average Grant Value, Forfeited	73.87	79.92
Weighted Average Grant Value, Non-vested at end of year	$ 73.87	$ 80.83

Share-Based Compensation - Su_3

Share-Based Compensation - Summary of Non-vested Time-Based Restricted Stock Units Outstanding (Details) - Time Based Restricted Stock Units - $ / shares	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of Shares, Non-vested at beginning of year	13,551	13,836
Number of Shares, Granted	28,946	8,796
Number of Shares, Vested	(7,431)	(7,417)
Number of Shares, Forfeited	(3,048)	(1,664)
Number of Shares, Non-vested at end of year	32,018	13,551
Weighted Average Grant Value, Non-vested at beginning of year	$ 82.81	$ 75.91
Weighted Average Grant Value, Granted	53.94	88.18
Weighted Average Grant Value, Vested	80.96	75.94
Weighted Average Grant Value, Forfeited	63.54	84.40
Weighted Average Grant Value, Non-vested at end of year	$ 58.98	$ 82.81

Share-Based Compensation - Sche

Share-Based Compensation - Schedule of Amounts Recognized in Consolidated Statement of Income for Restricted Stock, Time Based Restricted Stock Units and Performance Based Restricted Stock Units (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Share-Based Payment Arrangement, Noncash Expense [Abstract]
Share-based compensation expense	$ 1,589	$ 2,875	$ 3,476
Related income tax benefit	$ 444	$ 804	$ 970

Financial Instruments with Of_3

Financial Instruments with Off-Balance-Sheet Risk - Summary of Off-Balance-Sheet Financial Instruments with Contractual Amounts Include Present Credit Risk (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Standby Letters of Credit
Financial instruments whose contractual amount represents credit risk:
Financial instruments with off-balance-sheet risk	$ 34,063	$ 24,234
Unused Portion of Existing Lines of Credit
Financial instruments whose contractual amount represents credit risk:
Financial instruments with off-balance-sheet risk	994,196	1,073,567
Origination of New Loans
Financial instruments whose contractual amount represents credit risk:
Financial instruments with off-balance-sheet risk	18,341	25,411
Commitments to Sell Residential Mortgage Loans
Financial instruments whose notional amount exceeds the amount of credit risk:
Financial instrument notional amount exceeds credit risk	$ 795	$ 250

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Commitments and Contingencies [Line Items]
Description of operating lease expiration terms	operating leases and their terms expire between 2022 and 2032 and, in some instances, contain options to renew for periods up to
Renewal option period for operating leases	25 years
Existence of option to expire	true
Total rental expense	$ 7.5	$ 7.6	$ 7.3

Commitments and Contingencies_2

Commitments and Contingencies - Summary of Components of Operating Lease Cost and Other Related Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Commitments and Contingencies Disclosure [Abstract]
Operating lease cost	$ 6,849	$ 6,965	$ 6,976
Variable lease cost (cost excluded from lease payments)	27	38	13
Sublease income	(512)	(316)	(65)
Total operating lease cost	6,364	6,687	6,924
Other Information
Cash paid for amounts included in the measurement of lease liabilities – operating cash flows for operating leases	7,370	7,263	7,259
Operating Lease -operating cash flows (liability reduction)	$ 6,619	$ 6,401	$ 6,252
Weighted average lease term - operating leases	4 years 11 months 1 day	5 years 5 months 12 days	6 years 1 month 17 days
Weighted average discount rate - operating leases	3.01%	3.01%	2.94%

Commitments and Contingencies_3

Commitments and Contingencies - Schedule of Total Minimum Lease Payments Due in Future Periods under Lease Agreements (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Lessee, Operating Lease, Liability, to be Paid, Fiscal Year Maturity [Abstract]
Year 1	$ 6,959
Year 2	5,982
Year 3	4,745
Year 4	2,958
Year 5	2,589
Thereafter	3,900
Total minimum lease payments	27,133
Less: interest	(1,968)
Total lease liability	$ 25,165	$ 27,413

Shareholders' Equity - Addition

Shareholders' Equity - Additional Information (Details)	Dec. 31, 2023	Dec. 31, 2022	Jan. 01, 2015
Compliance With Regulatory Capital Requirements Under Banking Regulations [Line Items]
Tier 1 risk based capital to risk weighted assets	0.13	0.125
Capital to risk weighted assets	0.141	0.135
Tier 1 capital to average assets of leverage ratio	0.089	0.085
Minimum
Compliance With Regulatory Capital Requirements Under Banking Regulations [Line Items]
Common equity tier 1 risk based capital to risk weighted assets	0.07		0.045
Tier 1 risk based capital to risk weighted assets			0.060
Tier 1 risk based capital to risk weighted assets	0.085
Capital to risk weighted assets	0.105		0.080
Tier 1 capital to average assets of leverage ratio			0.040
Capital conservation buffer rate	2.50%

Shareholders' Equity - Minimum

Shareholders' Equity - Minimum Capital Requirements were Considered Well Capitalized by FRB and FDIC (Details)	Dec. 31, 2023 USD ($)	Dec. 31, 2022 USD ($)	Jan. 01, 2015
Compliance With Regulatory Capital Requirements Under Banking Regulations [Line Items]
Total capital (to risk-weighted assets), Actual, Amount	$ 521,903,000	$ 506,239,000
Tier I capital (to risk-weighted assets), Actual, Amount	481,198,000	466,369,000
Common equity tier I capital (to risk-weighted assets), Actual, Amount	481,198,000	466,369,000
Tier I capital (to average assets), Actual, Amount	$ 481,198,000	$ 466,369,000
Total capital (to risk-weighted assets), Actual, Ratio	0.141	0.135
Tier I capital (to risk-weighted assets), Actual, Ratio	0.13	0.125
Common equity tier I capital (to risk-weighted assets), Actual, Ratio	0.13	0.125
Tier I capital (to average assets), Actual, Ratio	0.089	0.085
Total capital (to risk-weighted assets), Minimum Capital Required For Capital Adequacy Plus Capital Conservation Buffer, Amount	$ 387,763,000	$ 393,285,000
Tier I capital (to risk-weighted assets), Minimum Capital Required For Capital Adequacy Plus Capital Conservation Buffer, Amount	313,903,000	318,373,000
Common equity tier I capital (to risk-weighted assets), Minimum Capital Required For Capital Adequacy Plus Capital Conservation Buffer, Amount	258,508,000	262,190,000
Tier I capital (to average assets), Minimum Capital Required For Capital Adequacy Plus Capital Conservation Buffer, Amount	$ 216,281,000	$ 219,309,000
Total capital (to risk-weighted assets), Minimum Capital Required For Capital Adequacy Plus Capital Conservation Buffer, Ratio	0.105	0.105
Tier I capital (to risk-weighted assets), Minimum Capital Required For Capital Adequacy Plus Capital Conservation Buffer, Ratio	0.085	0.085
Common equity tier I capital (to risk-weighted assets), Minimum Capital Required For Capital Adequacy Plus Capital Conservation Buffer, Ratio	0.070	0.070
Tier I capital (to average assets), Minimum Capital Required For Capital Adequacy Plus Capital Conservation Buffer, Ratio	0.040	0.040
Minimum
Compliance With Regulatory Capital Requirements Under Banking Regulations [Line Items]
Total capital (to risk-weighted assets), Actual, Ratio	0.105		0.080
Tier I capital (to risk-weighted assets), Actual, Ratio	0.085
Tier I capital (to average assets), Actual, Ratio			0.040
Cambridge Trust Company
Compliance With Regulatory Capital Requirements Under Banking Regulations [Line Items]
Total capital (to risk-weighted assets), Actual, Amount	$ 500,355,000	$ 490,175,000
Tier I capital (to risk-weighted assets), Actual, Amount	459,650,000	450,305,000
Common equity tier I capital (to risk-weighted assets), Actual, Amount	459,650,000	450,305,000
Tier I capital (to average assets), Actual, Amount	$ 459,650,000	$ 450,305,000
Total capital (to risk-weighted assets), Actual, Ratio	0.136	0.131
Tier I capital (to risk-weighted assets), Actual, Ratio	0.125	0.120
Common equity tier I capital (to risk-weighted assets), Actual, Ratio	0.125	0.120
Tier I capital (to average assets), Actual, Ratio	0.085	0.082
Total capital (to risk-weighted assets), Minimum Capital Required For Capital Adequacy Plus Capital Conservation Buffer, Amount	$ 387,727,000	$ 393,246,000
Tier I capital (to risk-weighted assets), Minimum Capital Required For Capital Adequacy Plus Capital Conservation Buffer, Amount	313,874,000	318,342,000
Common equity tier I capital (to risk-weighted assets), Minimum Capital Required For Capital Adequacy Plus Capital Conservation Buffer, Amount	258,485,000	262,164,000
Tier I capital (to average assets), Minimum Capital Required For Capital Adequacy Plus Capital Conservation Buffer, Amount	$ 216,268,000	$ 219,296,000
Total capital (to risk-weighted assets), Minimum Capital Required For Capital Adequacy Plus Capital Conservation Buffer, Ratio	0.105	0.105
Tier I capital (to risk-weighted assets), Minimum Capital Required For Capital Adequacy Plus Capital Conservation Buffer, Ratio	0.085	0.085
Common equity tier I capital (to risk-weighted assets), Minimum Capital Required For Capital Adequacy Plus Capital Conservation Buffer, Ratio	0.070	0.070
Tier I capital (to average assets), Minimum Capital Required For Capital Adequacy Plus Capital Conservation Buffer, Ratio	0.040	0.040
Cambridge Trust Company \| Minimum
Compliance With Regulatory Capital Requirements Under Banking Regulations [Line Items]
Total capital (to risk-weighted assets), Minimum To Be Well-Capitalized Under Prompt Corrective Action Provisions, Amount	$ 369,264,000	$ 374,520,000
Tier I capital (to risk-weighted assets), Minimum To Be Well-Capitalized Under Prompt Corrective Action Provisions, Amount	295,411,000	299,616,000
Common equity tier I capital (to risk-weighted assets), Minimum To Be Well-Capitalized Under Prompt Corrective Action Provisions, Amount	240,022,000	243,438,000
Tier I capital (to average assets), Minimum To Be Well-Capitalized Under Prompt Corrective Action Provisions, Amount	$ 270,335,000	$ 274,120,000
Total capital (to risk-weighted assets), Minimum To Be Well-Capitalized Under Prompt Corrective Action Provisions, Ratio	0.100	0.100
Tier I capital (to risk-weighted assets), Minimum To Be Well-Capitalized Under Prompt Corrective Action Provisions, Ratio	0.080	0.080
Common equity tier I capital (to risk-weighted assets), Minimum To Be Well-Capitalized Under Prompt Corrective Action Provisions, Ratio	0.065	0.065
Tier I capital (to average assets), Minimum To Be Well-Capitalized Under Prompt Corrective Action Provisions, Ratio	0.050	0.050

Comprehensive Income (Loss) - S

Comprehensive Income (Loss) - Summary of Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Available for sale securities, before tax amount
Unrealized holding gains/(losses), before tax amount		$ 3,073	$ (25,144)	$ (6,245)
Interest rate swaps designated as cash flow hedges, before tax amount
Unrealized holding gains/(losses), before tax amount		(687)	(2,170)	(1,329)
Reclassification adjustment for (gains)/losses recognized in net income, before tax amount	[1]	539	(832)	(2,587)
Defined benefit retirement plans, before tax amount
Net change in retirement liability, before tax amount		1,186	1,818	5,273
Total Other Comprehensive Income/(Loss), before tax amount		4,111	(26,328)	(4,888)
Available for sale securities, tax (expense) or benefit
Unrealized holding gains/(losses),tax (expense) or benefit		(737)	6,408	1,623
Interest rate swaps designated as cash flow hedges, tax (expense) or benefit
Unrealized holding gains/(losses), tax (expense) or benefit		192	607	370
Reclassification adjustment for (gains)/losses recognized in net income, tax (expense) or benefit	[1]	(150)	232	723
Defined benefit retirement plans, tax (expense) or benefit
Net change in retirement liability, tax (expense) or benefit		(331)	(508)	(1,472)
Total Other Comprehensive Income/(Loss), tax (expense) or benefit		(1,026)	6,739	1,244
Available for sale securities
Unrealized holding gains (losses)		2,336	(18,736)	(4,622)
Interest rate swaps designated as cash flow hedges
Unrealized holding losses		(495)	(1,563)	(959)
Less: reclassification adjustment for gains (losses) realized in net income	[1]	389	(600)	(1,864)
Defined benefit retirement plans
Net change in retirement liability, net-of-tax amount		855	1,310	3,801
Other comprehensive income (loss)		$ 3,085	$ (19,589)	$ (3,644)

[1] Reported in interest on payable loans line item in the Consolidated Statements of Income.

Comprehensive Income (Loss) -_2

Comprehensive Income (Loss) - Summary of Components of Accumulated Other Comprehensive Income (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive income, before tax amount	$ (23,910)	$ (28,025)
Accumulated other comprehensive income, deferred (tax) benefit	6,196	7,226
Total accumulated other comprehensive income, net-of-tax amount	(17,714)	(20,799)
Available for Sale Securities
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive income, before tax amount	(25,538)	(28,611)
Accumulated other comprehensive income, deferred (tax) benefit	6,651	7,390
Total accumulated other comprehensive income, net-of-tax amount	(18,887)	(21,221)
Interest Rate Swaps Designated as Cash Flow Hedges
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive income, before tax amount	(157)	(14)
Accumulated other comprehensive income, deferred (tax) benefit	44	4
Total accumulated other comprehensive income, net-of-tax amount	(113)	(10)
Defined Benefit Retirement Plans
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive income, before tax amount	1,785	600
Accumulated other comprehensive income, deferred (tax) benefit	(499)	(168)
Total accumulated other comprehensive income, net-of-tax amount	$ 1,286	$ 432

Earnings Per Share - Summary of

Earnings Per Share - Summary of Reconciliation Between Basic and Diluted Earnings Per Share (Detail) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Numerator:
Net income	$ 34,109	$ 52,909	$ 54,024
Less dividends and undistributed earnings allocated to participating securities	(31)	(257)	(250)
Net income applicable to common shareholders	$ 34,078	$ 52,652	$ 53,774
Denominator:
Weighted average shares outstanding, basic	7,828,316	7,163,223	6,926,257
Earnings per common share – basic	$ 4.35	$ 7.35	$ 7.76
Numerator:
Net Income (Loss)	$ 34,109	$ 52,909	$ 54,024
Less dividends and undistributed earnings allocated to participating securities	(31)	(257)	(250)
Net income applicable to common shareholders	$ 34,078	$ 52,652	$ 53,774
Denominator:
Weighted average shares outstanding, basic	7,828,316	7,163,223	6,926,257
Dilutive effect of common stock equivalents	15,000	51,000	65,000
Weighted average diluted common shares outstanding	7,843,482	7,213,913	6,990,603
Earnings per common share – diluted	$ 4.34	$ 7.3	$ 7.69

Derivatives And Hedging Activ_3

Derivatives And Hedging Activities - Additional Information (Details) - USD ($)	Dec. 31, 2023	Dec. 31, 2022
Derivative Instruments And Hedging Activities Disclosures [Line Items]
Estimated amount will be reclassified out of AOCI in to earnings	$ 391,000
Fair value of derivative liability	40,885,000	$ 50,827,000
Available for sale securities, amortized cost	163,376,000	182,027,000
Fair Value Hedges
Derivative Instruments And Hedging Activities Disclosures [Line Items]
Cumulative amount of fair value hedging adjustment included in the carrying amount of the hedged assets/(liabilities)	1,175,000
Carrying Amount of Hedged Assets/(Liabilities)	$ 498,825,000	0
Weighted average remaining maturity	1 year 3 months 10 days
Weighted average fixed interest rate	4.16%
Fair Value Hedges \| Fixed Rate Assets [Member]
Derivative Instruments And Hedging Activities Disclosures [Line Items]
Cumulative amount of fair value hedging adjustment included in the carrying amount of the hedged assets/(liabilities)	$ 1,200,000
Available for sale securities, amortized cost	681,100,000
Derivatives Designated as Hedging Instruments
Derivative Instruments And Hedging Activities Disclosures [Line Items]
Notional amount	500,000,000
Accrued Interest
Derivative Instruments And Hedging Activities Disclosures [Line Items]
Fair value of derivative liability	$ 0	$ 0

Derivative And Hedging Activiti

Derivative And Hedging Activities - Summary of Cumulative Basis Adjustment for Fair Value Hedges (Details) - Fair Value Hedges - USD ($)	Dec. 31, 2023	Dec. 31, 2022
Derivatives, Fair Value [Line Items]
Carrying Amount of Hedged Assets/(Liabilities)	$ 498,825,000	$ 0
Cumulative amount of fair value hedging adjustment included in the carrying amount of the hedged assets/(liabilities)	1,175,000
Fixed Rate Loans
Derivatives, Fair Value [Line Items]
Carrying Amount of Hedged Assets/(Liabilities)	498,825,000
Cumulative amount of fair value hedging adjustment included in the carrying amount of the hedged assets/(liabilities)	$ 1,175,000

Derivatives And Hedging Activ_4

Derivatives And Hedging Activities - Summary of Fair Values of Derivative Instruments in the Company's Consolidated Balance Sheets (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Derivative Instruments And Hedging Activities Disclosures [Line Items]
Derivative Assets, Fair value	$ 43,260	$ 52,773
Derivative Liabilities, Fair value	40,885	50,827
Derivatives Designated as Hedging Instruments
Derivative Instruments And Hedging Activities Disclosures [Line Items]
Derivative Assets, Fair value	2,904	1,966
Derivative Liabilities, Fair value	485
Derivatives Designated as Hedging Instruments \| Other Assets \| Fair Value Hedging
Derivative Instruments And Hedging Activities Disclosures [Line Items]
Derivative Assets, Fair value	1,620
Derivatives Designated as Hedging Instruments \| Interest Rate Contracts \| Cash Flow Hedging
Derivative Instruments And Hedging Activities Disclosures [Line Items]
Derivative Assets, Notional amount	100,000	250,000
Derivatives Designated as Hedging Instruments \| Interest Rate Contracts \| Fair Value Hedging
Derivative Instruments And Hedging Activities Disclosures [Line Items]
Derivative Assets, Notional amount	400,000
Derivative Liabilities, Notional Amount	100,000
Derivatives Designated as Hedging Instruments \| Interest Rate Contracts \| Other Assets \| Cash Flow Hedging
Derivative Instruments And Hedging Activities Disclosures [Line Items]
Derivative Assets, Fair value	1,284	1,966
Derivatives Designated as Hedging Instruments \| Interest Rate Contracts \| Other Liabilities \| Fair Value Hedging
Derivative Instruments And Hedging Activities Disclosures [Line Items]
Derivative Liabilities, Fair value	485
Derivatives Not Designated as Hedging Instruments
Derivative Instruments And Hedging Activities Disclosures [Line Items]
Derivative Assets, Fair value	40,356	50,807
Derivative Liabilities, Fair value	40,400	50,827
Derivatives Not Designated as Hedging Instruments \| Loan Related Derivative Contracts \| Other Liabilities
Derivative Instruments And Hedging Activities Disclosures [Line Items]
Derivative Liabilities, Fair value	40,338
Derivatives Not Designated as Hedging Instruments \| Loan Related Derivative Contracts \| Interest Rate Contracts
Derivative Instruments And Hedging Activities Disclosures [Line Items]
Derivative Assets, Notional amount	486,310
Derivative Liabilities, Notional Amount	486,310	499,619
Derivatives Not Designated as Hedging Instruments \| Loan Related Derivative Contracts \| Interest Rate Contracts \| Other Assets
Derivative Instruments And Hedging Activities Disclosures [Line Items]
Derivative Assets, Fair value	40,338
Derivatives Not Designated as Hedging Instruments \| Loan Related Derivative Contracts \| Interest Rate Contracts \| Other Liabilities
Derivative Instruments And Hedging Activities Disclosures [Line Items]
Derivative Liabilities, Fair value		50,784
Derivatives Not Designated as Hedging Instruments \| Loan Related Derivative Contracts \| Interest Rate Swaps with Clients
Derivative Instruments And Hedging Activities Disclosures [Line Items]
Derivative Assets, Notional amount		499,619
Derivatives Not Designated as Hedging Instruments \| Loan Related Derivative Contracts \| Interest Rate Swaps with Clients \| Other Assets
Derivative Instruments And Hedging Activities Disclosures [Line Items]
Derivative Assets, Fair value		50,784
Derivatives Not Designated as Hedging Instruments \| Loan Related Derivative Contracts \| Risk Participation Agreements Out to Counterparties
Derivative Instruments And Hedging Activities Disclosures [Line Items]
Derivative Assets, Notional amount	53,847	46,604
Derivatives Not Designated as Hedging Instruments \| Loan Related Derivative Contracts \| Risk Participation Agreements Out to Counterparties \| Other Assets
Derivative Instruments And Hedging Activities Disclosures [Line Items]
Derivative Assets, Fair value	18	23
Derivatives Not Designated as Hedging Instruments \| Loan Related Derivative Contracts \| Risk Participation Agreements with Counterparties
Derivative Instruments And Hedging Activities Disclosures [Line Items]
Derivative Liabilities, Notional Amount	98,779	71,046
Derivatives Not Designated as Hedging Instruments \| Loan Related Derivative Contracts \| Risk Participation Agreements with Counterparties \| Other Liabilities
Derivative Instruments And Hedging Activities Disclosures [Line Items]
Derivative Liabilities, Fair value	$ 62	$ 43

Derivatives And Hedging Activ_5

Derivatives And Hedging Activities - Summary of Cash Flow Hedge Accounting on AOCI (Details) - Cash Flow Hedging - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Interest Income
Derivative Instruments And Hedging Activities Disclosures [Line Items]
Amount of Gain or (Loss) Recognized in OCI - Included Component	$ (96)	$ 1,026
Amount of Gain or (Loss) Reclassified from AOCI into Income	(539)	832
Amount of Gain or (Loss) Recognized in OCI - Excluded Component	(443)	(194)
Interest Rate Contracts
Derivative Instruments And Hedging Activities Disclosures [Line Items]
Amount of Gain or (Loss) Recognized in OCI	(687)	(2,170)
Amount of Gain or (Loss) Recognized in OCI - Included Component		607
Amount of Gain or (Loss) Recognized in OCI - Excluded Component	$ (687)	$ (1,563)

Derivatives And Hedging Activ_6

Derivatives And Hedging Activities - Summary of Derivative Financial Instruments Not Designated as Hedging Instruments on the Consolidated Statements of Income (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Other contracts \| Loan related derivative income \| Derivatives Not Designated as Hedging Instruments
Derivative Instruments And Hedging Activities Disclosures [Line Items]
Amount of Gain or (Loss) Recognized in Income on Derivative	$ (86)	$ (166)	$ (124)

Derivatives And Hedging Activ_7

Derivatives And Hedging Activities - Schedule of Financial Instruments Eligible for Offset in Consolidated Balance Sheet (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Offsetting [Abstract]
Gross Amounts Recognized, Derivative assets	$ 43,260	$ 52,773
Net Amounts Recognized, Derivative Assets	$ 43,260	$ 52,773
Derivative Asset, Statement of Financial Position [Extensible Enumeration]	Other Assets	Other Assets
Gross Amounts Not Offset, Financial Instruments, Derivative Assets	$ 971	$ 48
Gross Amounts Not Offset, Net amount, Derivative Assets	970	595
Gross Amounts Recognized, Derivative Liabilities	40,885	50,827
Net Amounts Recognized, Derivative Liabilities	$ 40,885	$ 50,827
Derivative Liability, Statement of Financial Position [Extensible Enumeration]	Other Liabilities	Other Liabilities
Gross Amounts Not Offset, Financial Instruments, Derivative Liabilities	$ 971	$ 48
Gross Amounts Not Offset, Collateral Pledged (Received), Derivative Assets	(41,319)	(52,130)
Gross Amounts Not Offset, Net amount, Derivative Liabilities	$ 39,914	$ 50,875

Fair Value Measurements - Summa

Fair Value Measurements - Summary of Carrying Values and Estimated Fair Values of Financial Instruments (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Financial assets
Securities available for sale	$ 137,838	$ 153,416
Securities held to maturity	805,428	885,586
FHLB of Boston stock	19,056	6,264
Recurring Basis \| Carrying Value
Financial assets
Cash and cash equivalents	33,004	30,719
Securities available for sale	137,838	153,416
Securities held to maturity	959,332	1,051,997
Loans, net	3,982,600	4,025,082
FHLB of Boston stock	19,056	6,264
Accrued interest receivable	15,765	14,118
Mortgage servicing rights	1,470	1,665
Loan level interest rate swaps	40,338	50,784
Risk participation agreements out to counterparties	18	23
Financial liabilities
Deposits, excluding wholesale deposits	4,029,511	4,433,817
Wholesale deposits	291,667	381,559
Borrowings	452,155	105,212
Loan level interest rate swaps	40,338	50,784
Risk participation agreements in with counterparties	62	43
Recurring Basis \| Carrying Value \| Fair Value Hedge
Financial assets
Interest rate contracts	1,620
Financial liabilities
Interest rate contracts - fair value hedge	485
Recurring Basis \| Carrying Value \| Cash Flow Hedge
Financial assets
Interest rate contracts	1,284	1,966
Recurring Basis \| Estimated Fair Value
Financial assets
Cash and cash equivalents	33,004	30,719
Securities available for sale	137,838	153,416
Securities held to maturity	805,428	885,586
Loans, net	3,530,958	3,783,051
FHLB of Boston stock	19,056	6,264
Accrued interest receivable	15,765	14,118
Mortgage servicing rights	2,401	2,336
Loan level interest rate swaps	40,338	50,784
Risk participation agreements out to counterparties	18	23
Financial liabilities
Deposits, excluding wholesale deposits	4,026,404	4,429,190
Wholesale deposits	291,748	381,505
Borrowings	451,492	105,202
Loan level interest rate swaps	40,338	50,784
Risk participation agreements in with counterparties	62	43
Recurring Basis \| Estimated Fair Value \| Fair Value Hedge
Financial assets
Interest rate contracts	1,620
Financial liabilities
Interest rate contracts - fair value hedge	485
Recurring Basis \| Estimated Fair Value \| Cash Flow Hedge
Financial assets
Interest rate contracts	$ 1,284	$ 1,966

Fair Value Measurements - Sum_2

Fair Value Measurements - Summary of Certain Assets Reported at Fair Value on a Recurring Basis (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Securities available for sale	$ 137,838	$ 153,416
U.S. GSE Obligations
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Securities available for sale	20,462	19,733
Corporate Debt Securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Securities available for sale		1,000
Recurring Basis \| U.S. GSE Obligations
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Securities available for sale	20,462	19,733
Recurring Basis \| U.S. GSE Obligations \| Level 2
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Securities available for sale	20,462	19,733
Recurring Basis \| Mortgage Backed Securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Securities available for sale	117,376	132,683
Recurring Basis \| Mortgage Backed Securities \| Level 2
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Securities available for sale	117,376	132,683
Recurring Basis \| Corporate Debt Securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Securities available for sale		1,000
Recurring Basis \| Corporate Debt Securities \| Level 2
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Securities available for sale		1,000
Recurring Basis \| Interest Rate Swaps with Clients
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Other assets	40,338	50,784
Recurring Basis \| Interest Rate Swaps with Clients \| Level 2
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Other assets	40,338	50,784
Recurring Basis \| Risk Participation Agreements Out to Counterparties
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Other assets	18	23
Recurring Basis \| Risk Participation Agreements Out to Counterparties \| Level 2
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Other assets	18	23
Recurring Basis \| Interest Rate Contracts
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Other assets		1,966
Recurring Basis \| Interest Rate Contracts \| Fair Value Hedge
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Other assets	1,620
Other liabilities	485
Recurring Basis \| Interest Rate Contracts \| Cash Flow Hedge
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Other assets	1,284
Recurring Basis \| Interest Rate Contracts \| Level 2
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Other assets		1,966
Recurring Basis \| Interest Rate Contracts \| Level 2 \| Fair Value Hedge
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Other assets	1,620
Other liabilities	485
Recurring Basis \| Interest Rate Contracts \| Level 2 \| Cash Flow Hedge
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Other assets	1,284
Recurring Basis \| Interest rate swaps with counterparties
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Other liabilities	40,338	50,784
Recurring Basis \| Interest rate swaps with counterparties \| Level 2
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Other liabilities	40,338	50,784
Recurring Basis \| Risk Participation Agreements in With Counterparties
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Other liabilities	62	43
Recurring Basis \| Risk Participation Agreements in With Counterparties \| Level 2
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Other liabilities	$ 62	$ 43

Fair Value Measurements - Sched

Fair Value Measurements - Schedule of Carrying Value of Assets Measured at Fair Value on a Non-Recurring Basis (Details) - Non-recurring - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Assets, fair value, non-recurring basis	$ 9,675	$ 103
Level 3
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Assets, fair value, non-recurring basis	9,675	103
Individually Evaluated Collateral Dependent Loans
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Assets, fair value, non-recurring basis	9,675	103
Individually Evaluated Collateral Dependent Loans \| Level 3
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Assets, fair value, non-recurring basis	$ 9,675	$ 103

Fair Value Measurements - Addit

Fair Value Measurements - Additional Information (Details) - USD ($)	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Fair Value Disclosures [Abstract]
Transfers between levels	$ 0	$ 0

Condensed Financial Statement_3

Condensed Financial Statements of Parent Company - Condensed Balance Sheet (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Assets
Cash and cash equivalents	$ 33,004	$ 30,719
Goodwill	64,539	64,539
Other assets	103,432	105,290
Total assets	5,417,666	5,559,737
Shareholders’ Equity
Total shareholders' equity	534,573	517,552	$ 437,837	$ 401,732
Cambridge Bancorp [Member]
Assets
Cash and cash equivalents	21,212	15,747
Goodwill	33	33
Other assets	337	318
Investment in subsidiary	512,991	501,454
Total assets	534,573	517,552
Shareholders’ Equity
Total shareholders' equity	$ 534,573	$ 517,552

Condensed Financial Statement_4

Condensed Financial Statements of Parent Company - Condensed Statements of Income (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Interest expense
Total interest expense	$ 97,728	$ 16,778	$ 5,533
Income tax benefit	12,300	19,052	19,091
Income of parent company	34,109	52,909	54,024
Net Income	34,109	52,909	54,024
Cambridge Bancorp [Member]
Interest and dividend income
Dividends from subsidiary	27,320	24,734	25,995
Total income	27,320	24,734	25,995
Interest expense
Other expenses	158	148	150
Total interest expense	158	148	150
Income before income taxes and equity in undistributed income of subsidiary	27,162	24,586	25,845
Income tax benefit	(43)	(40)	(42)
Income of parent company	27,205	24,626	25,887
Equity in undistributed income of subsidiary	6,904	28,283	28,137
Net Income	$ 34,109	$ 52,909	$ 54,024

Condensed Financial Statement_5

Condensed Financial Statements of Parent Company - Condensed Statements of Cash Flows (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income	$ 34,109	$ 52,909	$ 54,024
Adjustments to reconcile net income to net cash provided by operating activities:
Deferred income tax benefit	1,665	587	2,899
Change in other assets, net	(2,950)	32,056	(5,473)
Change in other liabilities, net	(8,449)	26,260	429
Net cash provided by operating activities	33,090	51,950	65,508
CASH FLOWS FROM INVESTING ACTIVITIES:
Net cash provided by (used in) investing activities	137,767	(379,183)	(856,462)
CASH FLOWS FROM FINANCING ACTIVITIES:
Cash dividends paid on common stock	(20,986)	(18,414)	(16,554)
Net cash (used in) provided by financing activities	(168,572)	177,799	895,322
Net change in cash and cash equivalents	2,285	(149,434)	104,368
Cash and cash equivalents at beginning of period	30,719	180,153	75,785
Cash and cash equivalents at end of period	33,004	30,719	180,153
Significant non-cash transactions
Common Stock issued to shareholders due to merger		62,850
Cambridge Bancorp [Member]
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income	34,109	52,909	54,024
Adjustments to reconcile net income to net cash provided by operating activities:
Deferred income tax benefit	(43)	(40)	(42)
Change in other assets, net	24	12
Change in other liabilities, net			13
Undistributed income of subsidiary	(6,904)	(28,283)	(28,137)
Net cash provided by operating activities	27,186	24,598	25,858
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from the issuance of common stock	599	580	519
Repurchase of common stock	(1,334)	(1,320)	(1,440)
Cash dividends paid on common stock	(20,986)	(18,414)	(16,554)
Net cash (used in) provided by financing activities	(21,721)	(19,154)	(17,475)
Net change in cash and cash equivalents	5,465	5,444	8,383
Cash and cash equivalents at beginning of period	15,747	10,303	1,920
Cash and cash equivalents at end of period	$ 21,212	15,747	$ 10,303
Significant non-cash transactions
Common Stock issued to shareholders due to merger		$ 62,850