Cullen/Frost Bankers (CFR) 10-Q25 Jul 242024 Q2 Quarterly reportFinancial data

Company Profile

Document and Entity Information

Document and Entity Information - $ / shares	6 Months Ended
Document and Entity Information - $ / shares	Jun. 30, 2024	Jul. 18, 2024	Dec. 31, 2023
Entity Information [Line Items]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Jun. 30, 2024
Document Transition Report	false
Entity File Number	001-13221
Entity Registrant Name	Cullen/Frost Bankers, Inc.
Entity Incorporation, State or Country Code	TX
Entity Tax Identification Number	74-1751768
Entity Address, Address Line One	111 W. Houston Street,
Entity Address, City or Town	San Antonio,
Entity Address, State or Province	TX
Entity Address, Postal Zip Code	78205
City Area Code	(210)
Local Phone Number	220-4011
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		64,020,978
Common stock, par value	$ 0.01		$ 0.01
Amendment Flag	false
Document Fiscal Year Focus	2024
Document Fiscal Period Focus	Q2
Entity Central Index Key	0000039263
Current Fiscal Year End Date	--12-31
Common Stock [Member] \| NEW YORK STOCK EXCHANGE, INC. [Member]
Entity Information [Line Items]
Title of 12(b) Security	Common Stock, $.01 Par Value
Trading Symbol	CFR
Security Exchange Name	NYSE
Series B Preferred Stock [Member] \| NEW YORK STOCK EXCHANGE, INC. [Member]
Entity Information [Line Items]
Title of 12(b) Security	Depositary Shares, each representing a 1/40th interest in a share of 4.450% Non-Cumulative Perpetual Preferred Stock, Series B
Trading Symbol	CFR.PrB
Security Exchange Name	NYSE

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Jun. 30, 2024	Dec. 31, 2023
Assets:
Cash and due from banks	$ 612,648	$ 617,569
Interest-bearing deposits	6,445,461	7,985,057
Federal funds sold	2,025	0
Resell agreements	84,650	84,650
Total cash and cash equivalents	7,144,784	8,687,276
Securities held to maturity, net of allowance for credit losses of $310 at both June 30, 2024 and December 31, 2023	3,586,116	3,619,428
Securities available for sale, at estimated fair value	15,197,638	16,578,371
Trading account securities	32,186	31,717
Loans, net of unearned discounts	19,995,756	18,824,251
Less: Allowance for credit losses on loans	(256,307)	(245,996)
Net loans	19,739,449	18,578,255
Premises and equipment, net	1,221,043	1,190,033
Accrued interest receivable and other assets	1,921,477	2,159,958
Total assets	48,842,693	50,845,038
Liabilities:
Non-interest-bearing demand deposits	13,484,977	14,926,094
Interest-bearing deposits	26,833,163	26,994,474
Total deposits	40,318,140	41,920,568
Federal funds purchased	35,925	14,200
Repurchase agreements	3,762,942	4,127,188
Junior subordinated deferrable interest debentures, net of unamortized issuance costs	123,155	123,127
Subordinated notes, net of unamortized issuance costs	99,569	99,491
Accrued interest payable and other liabilities	837,157	844,017
Total liabilities	45,176,888	47,128,591
Shareholders’ Equity:
Preferred stock, par value $0.01 per share; 10,000,000 shares authorized; 150,000 Series B shares ($1,000 liquidation preference) issued at June 30, 2024 and December 31, 2023	145,452	145,452
Common stock, par value $0.01 per share; 210,000,000 shares authorized; 64,404,582 shares issued at both June 30, 2024 and December 31, 2023	644	644
Additional paid-in capital	1,064,070	1,055,809
Retained earnings	3,810,008	3,657,688
Accumulated other comprehensive income (loss), net of tax	(1,309,344)	(1,119,219)
Treasury stock, at cost; 415,954 shares at June 30, 2024 and 219,295 at December 31, 2023	(45,025)	(23,927)
Total shareholders’ equity	3,665,805	3,716,447
Total liabilities and shareholders’ equity	$ 48,842,693	$ 50,845,038

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Jun. 30, 2024	Dec. 31, 2023
Securities, held-to-maturity, allowance for credit loss	$ 310	$ 310
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	210,000,000	210,000,000
Common stock, shares issued	64,404,582	64,404,582
Treasury stock, shares	415,954	219,295
Series B Preferred Stock [Member]
Preferred stock, par value	$ 0.01	$ 0.01
Preferred stock, shares authorized	10,000,000	10,000,000
Preferred stock, shares issued	150,000	150,000
Preferred stock, liquidation preference value	$ 1,000	$ 1,000

Consolidated Statements of Inco

Consolidated Statements of Income - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
Consolidated Statements of Income - USD ($) $ in Thousands	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Interest income:
Loans, including fees	$ 343,776	$ 290,552	$ 674,316	$ 560,267
Securities:
Taxable	99,012	101,960	197,074	199,735
Tax-exempt	54,579	60,637	109,838	127,271
Interest-bearing deposits	97,639	87,748	198,000	186,993
Federal funds sold	80	305	160	1,063
Resell agreements	1,199	1,126	2,397	2,194
Total interest income	596,285	542,328	1,181,785	1,077,523
Interest expense:
Deposits	159,260	120,266	314,894	218,255
Federal funds purchased	547	412	991	995
Repurchase agreements	36,302	33,114	72,250	66,765
Junior subordinated deferrable interest debentures	2,300	2,106	4,559	4,094
Subordinated notes	1,164	1,164	2,328	2,328
Total interest expense	199,573	157,062	395,022	292,437
Net interest income	396,712	385,266	786,763	785,086
Credit loss expense	15,787	9,901	29,437	19,005
Net interest income after credit loss expense	380,925	375,365	757,326	766,081
Non-interest income:
Trust and investment management fees	41,404	39,392	80,489	75,536
Service charges on deposit accounts	26,114	23,487	50,909	45,366
Insurance commissions and fees	13,919	12,940	32,215	31,892
Interchange and card transaction fees	5,351	5,250	9,825	10,139
Other charges, commissions, and fees	13,020	12,090	25,080	23,794
Net gain (loss) on securities transactions	0	33	0	54
Other	11,382	10,336	24,049	22,012
Total non-interest income	111,190	103,528	222,567	208,793
Non-interest expense:
Salaries and wages	151,237	133,195	299,237	263,540
Employee benefits	28,802	26,792	64,772	60,714
Net occupancy	32,374	31,714	64,152	62,063
Technology, furniture, and equipment	35,951	33,043	70,946	65,524
Deposit insurance	8,383	6,202	23,107	12,447
Other	60,217	54,096	120,967	105,896
Total non-interest expense	316,964	285,042	643,181	570,184
Income before income taxes	175,151	193,851	336,712	404,690
Income taxes	29,652	31,733	55,523	64,919
Net income	145,499	162,118	281,189	339,771
Preferred stock dividends	1,669	1,669	3,338	3,338
Net income available to common shareholders	$ 143,830	$ 160,449	$ 277,851	$ 336,433
Earnings per common share:
Basic	$ 2.21	$ 2.47	$ 4.27	$ 5.18
Diluted	$ 2.21	$ 2.47	$ 4.27	$ 5.17

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Net income	$ 145,499	$ 162,118	$ 281,189	$ 339,771
Other comprehensive income (loss), before tax:
Change in net unrealized gain/loss on securities available for sale during the period	(42,111)	(206,863)	(241,186)	53,406
Change in net unrealized gain on securities transferred to held to maturity	(157)	(162)	(316)	(322)
Reclassification adjustment for net (gains) losses included in net income	0	(33)	0	(54)
Total securities available for sale and transferred securities, before tax amount	(42,268)	(207,058)	(241,502)	53,030
Defined-benefit post-retirement benefit plans:
Reclassification adjustment for net amortization of actuarial gain/loss included in net income as a component of net periodic cost (benefit)	419	870	837	1,740
Total defined-benefit post-retirement benefit plans	419	870	837	1,740
Other comprehensive income (loss), before tax	(41,849)	(206,188)	(240,665)	54,770
Deferred tax expense (benefit)	(8,788)	(43,299)	(50,540)	11,503
Other comprehensive income (loss), net of tax	(33,061)	(162,889)	(190,125)	43,267
Comprehensive income (loss)	$ 112,438	$ (771)	$ 91,064	$ 383,038

Consolidated Statements of Chan

Consolidated Statements of Changes in Shareholders' Equity - USD ($) $ in Thousands	Total	Preferred Stock [Member]	Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	AOCI Attributable to Parent [Member]	Treasury Stock, Common
Total shareholders’ equity at beginning of period at Dec. 31, 2022	$ 3,137,228	$ 145,452	$ 643	$ 1,029,756	$ 3,309,671	$ (1,348,294)	$ 0
Net income	339,771				339,771
Other comprehensive income (loss)	43,267					43,267
Stock option exercises/stock unit conversions (38,452 shares QTD and 122,628 shares YTD in 2024 and 13,626 shares QTD and 64,013 shares YTD in 2023)	2,446		1	1,463	(519)		1,501
Stock compensation expense recognized in earnings	9,535			9,535
Purchase of treasury stock (301,094 shares QTD and 319,287 shares YTD in 2024 and 289,149 shares QTD and 298,332 shares YTD in 2023)	(29,124)						(29,124)
Cash dividends – preferred stock (approximately $11.13 per share which is equivalent to approximately $0.28 per depository share QTD and $22.25 per share which is equivalent to approximately $0.56 per depository share YTD in both 2024 and 2023, respectively.)	(3,338)				(3,338)
Cash dividends – common stock ($0.92 per share QTD and $1.84 per share YTD in 2024 and $0.87 per share QTD and $1.74 per share YTD in 2023)	(113,043)				(113,043)
Total shareholders’ equity at end of period at Jun. 30, 2023	3,386,742	145,452	644	1,040,754	3,532,542	(1,305,027)	(27,623)
Total shareholders’ equity at beginning of period at Dec. 31, 2022	3,137,228	145,452	643	1,029,756	3,309,671	(1,348,294)	0
Total shareholders’ equity at end of period at Dec. 31, 2023	3,716,447	145,452	644	1,055,809	3,657,688	(1,119,219)	(23,927)
Total shareholders’ equity at beginning of period at Mar. 31, 2023	3,467,801	145,452	644	1,035,961	3,428,991	(1,142,138)	(1,109)
Net income	162,118				162,118
Other comprehensive income (loss)	(162,889)					(162,889)
Stock option exercises/stock unit conversions (38,452 shares QTD and 122,628 shares YTD in 2024 and 13,626 shares QTD and 64,013 shares YTD in 2023)	946				(491)		1,437
Stock compensation expense recognized in earnings	4,793			4,793
Purchase of treasury stock (301,094 shares QTD and 319,287 shares YTD in 2024 and 289,149 shares QTD and 298,332 shares YTD in 2023)	(27,951)						(27,951)
Cash dividends – preferred stock (approximately $11.13 per share which is equivalent to approximately $0.28 per depository share QTD and $22.25 per share which is equivalent to approximately $0.56 per depository share YTD in both 2024 and 2023, respectively.)	(1,669)				(1,669)
Cash dividends – common stock ($0.92 per share QTD and $1.84 per share YTD in 2024 and $0.87 per share QTD and $1.74 per share YTD in 2023)	(56,407)				(56,407)
Total shareholders’ equity at end of period at Jun. 30, 2023	3,386,742	145,452	644	1,040,754	3,532,542	(1,305,027)	(27,623)
Total shareholders’ equity at beginning of period at Dec. 31, 2023	3,716,447	145,452	644	1,055,809	3,657,688	(1,119,219)	(23,927)
Net income	281,189				281,189
Other comprehensive income (loss)	(190,125)					(190,125)
Stock option exercises/stock unit conversions (38,452 shares QTD and 122,628 shares YTD in 2024 and 13,626 shares QTD and 64,013 shares YTD in 2023)	5,209				(5,919)		11,128
Stock compensation expense recognized in earnings	8,261			8,261
Purchase of treasury stock (301,094 shares QTD and 319,287 shares YTD in 2024 and 289,149 shares QTD and 298,332 shares YTD in 2023)	(32,226)						(32,226)
Cash dividends – preferred stock (approximately $11.13 per share which is equivalent to approximately $0.28 per depository share QTD and $22.25 per share which is equivalent to approximately $0.56 per depository share YTD in both 2024 and 2023, respectively.)	(3,338)				(3,338)
Cash dividends – common stock ($0.92 per share QTD and $1.84 per share YTD in 2024 and $0.87 per share QTD and $1.74 per share YTD in 2023)	(119,612)				(119,612)
Total shareholders’ equity at end of period at Jun. 30, 2024	3,665,805	145,452	644	1,064,070	3,810,008	(1,309,344)	(45,025)
Total shareholders’ equity at beginning of period at Mar. 31, 2024	3,638,180	145,452	644	1,059,547	3,726,559	(1,276,283)	(17,739)
Net income	145,499				145,499
Other comprehensive income (loss)	(33,061)					(33,061)
Stock option exercises/stock unit conversions (38,452 shares QTD and 122,628 shares YTD in 2024 and 13,626 shares QTD and 64,013 shares YTD in 2023)	2,294				(573)		2,867
Stock compensation expense recognized in earnings	4,523			4,523
Purchase of treasury stock (301,094 shares QTD and 319,287 shares YTD in 2024 and 289,149 shares QTD and 298,332 shares YTD in 2023)	(30,153)						(30,153)
Cash dividends – preferred stock (approximately $11.13 per share which is equivalent to approximately $0.28 per depository share QTD and $22.25 per share which is equivalent to approximately $0.56 per depository share YTD in both 2024 and 2023, respectively.)	(1,669)				(1,669)
Cash dividends – common stock ($0.92 per share QTD and $1.84 per share YTD in 2024 and $0.87 per share QTD and $1.74 per share YTD in 2023)	(59,808)				(59,808)
Total shareholders’ equity at end of period at Jun. 30, 2024	$ 3,665,805	$ 145,452	$ 644	$ 1,064,070	$ 3,810,008	$ (1,309,344)	$ (45,025)

Consolidated Statements of Ch_2

Consolidated Statements of Changes in Shareholders' Equity (Parenthetical) - $ / shares	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Statement of Stockholders' Equity [Abstract]
Stock option exercises/stock unit conversions (38,452 shares QTD and 122,628 shares YTD in 2024 and 13,626 shares QTD and 64,013 shares YTD in 2023)	38,452	13,626	122,628	64,013
Purchase of treasury stock (301,094 shares QTD and 319,287 shares YTD in 2024 and 289,149 shares QTD and 298,332 shares YTD in 2023)	301,094	289,149	319,287	298,332
Cash dividends – preferred stock (approximately $11.13 per share and $22.25 per share YTD in both 2024 and 2023)	$ 11.13	$ 11.13	$ 22.25	$ 22.25
Cash dividend - Preferred Stock Dividends equivalent Per depositary Share Declared ($0.28 QTD and $0.56 YTD during both 2024 and 2023)	0.28	0.28	0.56	0.56
Cash dividends – common stock ($0.92 per share QTD and $1.84 per share YTD in 2024 and $0.87 per share QTD and $1.74 per share YTD in 2023)	$ 0.92	$ 0.87	$ 1.84	$ 1.74

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023
Operating Activities:
Net income	$ 281,189	$ 339,771
Adjustments to reconcile net income to net cash from operating activities:
Credit loss expense	29,437	19,005
Deferred tax expense (benefit)	(7,713)	(2,489)
Accretion of loan discounts	(10,245)	(9,265)
Securities premium amortization (discount accretion), net	24,786	36,919
Net (gain) loss on securities transactions	0	(54)
Depreciation and amortization	40,695	37,076
Net (gain) loss on sale/write-down of assets/foreclosed assets	110	(283)
Stock-based compensation	8,261	9,535
Net tax benefit from stock-based compensation	621	469
Earnings on life insurance policies	(1,840)	(1,387)
Net change in:
Trading account securities	(175)	335
Lease right-of-use assets	12,473	11,193
Accrued interest receivable and other assets	287,609	59,051
Accrued interest payable and other liabilities	(47,195)	(176,718)
Net cash from operating activities	618,013	323,158
Investing Activities:
Securities held-to-maturity - Purchases	0	(1,141,443)
Securities held to maturity: Maturities, calls and principal repayments	31,325	92,547
Securities available for sale:
Purchases	(3,757,122)	(7,607,014)
Sales	0	1,543,355
Maturities, calls and principal repayments	4,902,271	7,077,003
Proceeds from sale of loans	1,191	2,215
Net change in loans	(1,179,526)	(602,902)
Benefits received on life insurance policies	1,063	1,000
Proceeds from sales of premises and equipment	9	1,179
Purchases of premises and equipment	(64,800)	(85,156)
Proceeds from sales of repossessed properties	0	583
Net cash from investing activities	(65,589)	(718,633)
Financing Activities:
Net change in deposits	(1,602,428)	(3,253,366)
Net change in short-term borrowings	(342,521)	(1,128,896)
Proceeds from stock option exercises	5,209	2,446
Purchase of treasury stock	(32,226)	(29,124)
Cash dividends paid on preferred stock	(3,338)	(3,338)
Cash dividends paid on common stock	(119,612)	(113,043)
Net cash from financing activities	(2,094,916)	(4,525,321)
Net change in cash and cash equivalents	(1,542,492)	(4,920,796)
Cash and cash equivalents at beginning of period	8,687,276	12,028,132
Cash and cash equivalents at end of period	$ 7,144,784	$ 7,107,336

Significant Accounting Policies

Significant Accounting Policies	6 Months Ended
Significant Accounting Policies	Jun. 30, 2024
Accounting Policies [Abstract]
Significant Accounting Policies	Significant Accounting Policies Nature of Operations. Cullen/Frost Bankers, Inc. (“Cullen/Frost”) is a financial holding company and a bank holding company headquartered in San Antonio, Texas that provides, through its subsidiaries, a broad array of products and services throughout numerous Texas markets. The terms “Cullen/Frost,” “the Corporation,” “we,” “us” and “our” mean Cullen/Frost Bankers, Inc., and its subsidiaries, when appropriate. In addition to general commercial and consumer banking, other products and services offered include trust and investment management, insurance, brokerage, mutual funds, leasing, treasury management, capital markets advisory and item processing. Basis of Presentation. The consolidated financial statements in this Quarterly Report on Form 10-Q include the accounts of Cullen/Frost and all other entities in which Cullen/Frost has a controlling financial interest. All significant intercompany balances and transactions have been eliminated in consolidation. The accounting and financial reporting policies we follow conform, in all material respects, to accounting principles generally accepted in the United States and to general practices within the financial services industry. The consolidated financial statements in this Quarterly Report on Form 10-Q have not been audited by an independent registered public accounting firm, but in the opinion of management, reflect all adjustments necessary for a fair presentation of our financial position and results of operations. All such adjustments were of a normal and recurring nature. The consolidated financial statements have been prepared in accordance with accounting principles generally accepted in the United States for interim financial information and with the instructions to Form 10-Q adopted by the Securities and Exchange Commission (“SEC”). Accordingly, the financial statements do not include all of the information and footnotes required by accounting principles generally accepted in the United States for complete financial statements and should be read in conjunction with our consolidated financial statements, and notes thereto, for the year ended December 31, 2023, included in our Annual Report on Form 10-K filed with the SEC on February 6, 2024 (the “ 2023 Form 10-K ”). Operating results for the interim periods disclosed herein are not necessarily indicative of the results that may be expected for a full year or any future period. Use of Estimates . The preparation of financial statements in conformity with accounting principles generally accepted in the United States 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 financial statements. Actual results could differ from those estimates. The allowance for loan losses and the fair values of financial instruments and the status of contingencies are particularly subject to change. Cash Flow Reporting . Additional cash flow information was as follows: Six Months Ended 2024 2023 Cash paid for interest $ 389,432 $ 270,358 Cash paid for income taxes 62,000 66,500 Significant non-cash transactions: Unsettled securities transactions 29,011 10,988 Right-of-use lease assets obtained in exchange for lessee operating lease liabilities 9,218 8,914 Accounting Changes, Reclassifications and Restatements.

Securities

Securities	6 Months Ended
Securities	Jun. 30, 2024
Investments, Debt and Equity Securities [Abstract]
Securities	Securities Securities - Held to Maturity. A summary of the amortized cost, fair value and allowance for credit losses related to securities held to maturity as of June 30, 2024 and December 31, 2023 is presented below. Amortized Gross Gross Estimated Allowance Net June 30, 2024 Residential mortgage-backed securities $ 1,225,779 $ — $ 74,853 $ 1,150,926 $ — $ 1,225,779 States and political subdivisions 2,359,147 17,319 111,929 2,264,537 (310) 2,358,837 Other 1,500 — 26 1,474 — 1,500 Total $ 3,586,426 $ 17,319 $ 186,808 $ 3,416,937 $ (310) $ 3,586,116 December 31, 2023 Residential mortgage-backed securities $ 1,250,431 $ 76 $ 54,175 $ 1,196,332 $ — $ 1,250,431 States and political subdivisions 2,367,807 42,990 76,540 2,334,257 (310) 2,367,497 Other 1,500 — 45 1,455 — 1,500 Total $ 3,619,738 $ 43,066 $ 130,760 $ 3,532,044 $ (310) $ 3,619,428 All mortgage-backed securities included in the above table were issued by U.S. government agencies and corporations. The carrying value of held-to-maturity securities pledged to secure public funds, trust deposits, repurchase agreements and for other purposes, as required or permitted by law was $1.3 billion and $1.0 billion at June 30, 2024 and December 31, 2023, respectively. Accrued interest receivable on held-to-maturity securities totaled $38.2 million and $40.9 million at June 30, 2024 and December 31, 2023, respectively and is included in accrued interest receivable and other assets in the accompanying consolidated balance sheets. From time to time, we have reclassified certain securities from available for sale to held to maturity. The net unamortized, unrealized gain remaining on transferred securities included in accumulated other comprehensive income in the accompanying balance sheet totaled $835 thousand ($660 thousand, net of tax) at June 30, 2024 and $1.2 million ($909 thousand, net of tax) at December 31, 2023. This amount will be amortized out of accumulated other comprehensive income over the remaining life of the underlying securities as an adjustment of the yield on those securities. The following table summarizes Moody's and/or Standard & Poor's bond ratings for our portfolio of held-to-maturity securities issued by States and political subdivisions and other securities as of June 30, 2024 and December 31, 2023: States and Political Subdivisions Not Guaranteed or Pre-Refunded Guaranteed by the Texas PSF Guaranteed by Third Party Pre-Refunded Total Other June 30, 2024 Aaa/AAA $ 301,518 $ 1,538,227 $ 13,645 $ 1,090 $ 1,854,480 $ — Aa/AA 498,557 — 6,110 — 504,667 — Not rated — — — — — 1,500 Total $ 800,075 $ 1,538,227 $ 19,755 $ 1,090 $ 2,359,147 $ 1,500 December 31, 2023 Aaa/AAA $ 301,721 $ 1,541,913 $ 13,651 $ 1,401 $ 1,858,686 $ — Aa/AA 503,016 — 6,105 — 509,121 — Not rated — — — — — 1,500 Total $ 804,737 $ 1,541,913 $ 19,756 $ 1,401 $ 2,367,807 $ 1,500 The following table details activity in the allowance for credit losses on held-to-maturity securities during the three and six months ended June 30, 2024 and 2023. Three Months Ended Six Months Ended 2024 2023 2024 2023 Beginning balance $ 310 $ 262 $ 310 $ 158 Credit loss expense (benefit) — 5 — 109 Ending balance $ 310 $ 267 $ 310 $ 267 Securities - Available for Sale. A summary of the amortized cost, fair value and allowance for credit losses related to securities available for sale as of June 30, 2024 and December 31, 2023 is presented below. Amortized Gross Gross Allowance Estimated June 30, 2024 U.S. Treasury $ 4,184,938 $ — $ 302,607 $ — $ 3,882,331 Residential mortgage-backed securities 7,567,795 2,840 1,033,208 — 6,537,427 States and political subdivisions 5,030,087 2,316 297,494 — 4,734,909 Other 42,971 — — — 42,971 Total $ 16,825,791 $ 5,156 $ 1,633,309 $ — $ 15,197,638 December 31, 2023 U.S. Treasury $ 5,212,894 $ — $ 285,305 $ — $ 4,927,589 Residential mortgage-backed securities 7,463,954 9,066 876,338 — 6,596,682 States and political subdivisions 5,245,721 5,762 240,152 — 5,011,331 Other 42,769 — — — 42,769 Total $ 17,965,338 $ 14,828 $ 1,401,795 $ — $ 16,578,371 All mortgage-backed securities included in the above table were issued by U.S. government agencies and corporations. At June 30, 2024, all of the securities in our available for sale municipal bond portfolio were issued by the State of Texas or political subdivisions or agencies within the State of Texas, of which approximately 72.9% are either guaranteed by the Texas Permanent School Fund (“PSF”) or have been pre-refunded. Securities with limited marketability, such as stock in the Federal Reserve Bank and the Federal Home Loan Bank, are carried at cost and are reported as other available for sale securities in the table above. The carrying value of available-for-sale securities pledged to secure public funds, trust deposits, repurchase agreements and for other purposes, as required or permitted by law was $5.3 billion and $6.1 billion at June 30, 2024 and December 31, 2023, respectively. Accrued interest receivable on available-for-sale securities totaled $105.2 million and $114.9 million at June 30, 2024 and December 31, 2023, respectively, and is included in accrued interest receivable and other assets in the accompanying consolidated balance sheets. The table below summarizes, as of June 30, 2024, securities available for sale in an unrealized loss position for which an allowance for credit losses has not been recorded, aggregated by type of security and length of time in a continuous unrealized loss position. Less than 12 Months More than 12 Months Total Estimated Unrealized Estimated Unrealized Estimated Unrealized U.S. Treasury $ — $ — $ 3,882,331 $ 302,607 $ 3,882,331 $ 302,607 Residential mortgage-backed securities 508,001 5,469 5,561,705 1,027,739 6,069,706 1,033,208 States and political subdivisions 683,217 7,567 3,875,534 289,927 4,558,751 297,494 Total $ 1,191,218 $ 13,036 $ 13,319,570 $ 1,620,273 $ 14,510,788 $ 1,633,309 As of June 30, 2024, no allowance for credit losses has been recognized on available for sale securities in an unrealized loss position as management does not believe any of the securities are impaired due to reasons of credit quality. This is based upon our analysis of the underlying risk characteristics, including credit ratings, and other qualitative factors related to our available for sale securities and in consideration of our historical credit loss experience and internal forecasts. The issuers of these securities continue to make timely principal and interest payments under the contractual terms of the securities. Furthermore, management does not have the intent to sell any of the securities classified as available for sale in the table above and believes that it is more likely than not that we will not have to sell any such securities before a recovery of cost. The unrealized losses are due to increases in market interest rates over the yields available at the time the underlying securities were purchased. The fair value is expected to recover as the securities approach their maturity date or repricing date or if market yields for such investments decline. Contractual Maturities. The following table summarizes the maturity distribution schedule of securities held to maturity and securities available for sale as of June 30, 2024. Mortgage-backed securities are included in maturity categories based on their stated maturity date. Expected maturities may differ from contractual maturities because issuers may have the right to call or prepay obligations. Other securities classified as available for sale include stock in the Federal Reserve Bank and the Federal Home Loan Bank, which have no maturity date. These securities have been included in the total column only. Within 1 Year 1 - 5 Years 5 - 10 Years After 10 Years Total Held To Maturity Amortized Cost Residential mortgage-backed securities $ — $ 43,600 $ 467,780 $ 714,399 $ 1,225,779 States and political subdivisions 9,095 4,273 51,899 2,293,880 2,359,147 Other 1,500 — — — 1,500 Total $ 10,595 $ 47,873 $ 519,679 $ 3,008,279 $ 3,586,426 Estimated Fair Value Residential mortgage-backed securities $ — $ 38,538 $ 416,882 $ 695,506 $ 1,150,926 States and political subdivisions 9,068 4,254 49,314 2,201,901 2,264,537 Other 1,474 — — — 1,474 Total $ 10,542 $ 42,792 $ 466,196 $ 2,897,407 $ 3,416,937 Available For Sale Amortized Cost U. S. Treasury $ 1,173,271 $ 2,621,114 $ 197,956 $ 192,597 $ 4,184,938 Residential mortgage-backed securities 702 1,118 13,084 7,552,891 7,567,795 States and political subdivisions 176,288 248,998 830,750 3,774,051 5,030,087 Other — — — — 42,971 Total $ 1,350,261 $ 2,871,230 $ 1,041,790 $ 11,519,539 $ 16,825,791 Estimated Fair Value U. S. Treasury $ 1,152,647 $ 2,428,473 $ 163,742 $ 137,469 $ 3,882,331 Residential mortgage-backed securities 696 1,121 13,116 6,522,494 6,537,427 States and political subdivisions 175,880 244,313 787,791 3,526,925 4,734,909 Other — — — — 42,971 Total $ 1,329,223 $ 2,673,907 $ 964,649 $ 10,186,888 $ 15,197,638 Sales of Securities. Sales of available for sale securities were as follows: Three Months Ended Six Months Ended 2024 2023 2024 2023 Proceeds from sales $ — $ 659,082 $ — $ 1,543,355 Gross realized gains — 561 — 5,417 Gross realized losses — (528) — (5,363) Tax (expense) benefit of securities gains/losses — (7) — (11) Premiums and Discounts . Premium amortization and discount accretion included in interest income on securities was as follows: Three Months Ended Six Months Ended 2024 2023 2024 2023 Premium amortization $ (16,570) $ (21,242) $ (34,523) $ (47,167) Discount accretion 5,032 4,843 9,737 10,248 Net (premium amortization) discount accretion $ (11,538) $ (16,399) $ (24,786) $ (36,919) Trading Account Securities. Trading account securities, at estimated fair value, were as follows: June 30, December 31, U.S. Treasury $ 31,400 $ 30,265 States and political subdivisions 786 1,452 Total $ 32,186 $ 31,717 Net gains and losses on trading account securities were as follows: Three Months Ended Six Months Ended 2024 2023 2024 2023 Net gain on sales transactions $ 1,223 $ 903 $ 2,382 $ 1,871 Net mark-to-market gains (losses) (82) (10) (101) (27) Net gain (loss) on trading account securities $ 1,141 $ 893 $ 2,281 $ 1,844

Loans

Loans	6 Months Ended
Loans	Jun. 30, 2024
Receivables [Abstract]
Loans	Loans Loans were as follows: June 30, December 31, Commercial and industrial $ 6,210,179 $ 5,967,182 Energy: Production 858,990 681,568 Service 209,658 194,126 Other 28,009 61,043 Total energy 1,096,657 936,737 Commercial real estate: Commercial mortgages 6,955,118 6,746,709 Construction 1,997,545 1,680,724 Land 542,549 555,211 Total commercial real estate 9,495,212 8,982,644 Consumer real estate: Home equity lines of credit 832,307 792,876 Home equity loans 790,727 694,966 Home improvement loans 813,799 765,887 Other 303,895 206,997 Total consumer real estate 2,740,728 2,460,726 Total real estate 12,235,940 11,443,370 Consumer and other 452,980 476,962 Total loans $ 19,995,756 $ 18,824,251 Concentrations of Credit. Most of our lending activity occurs within the State of Texas, including the four largest metropolitan areas of Austin, Dallas/Ft. Worth, Houston, and San Antonio, as well as other markets. The majority of our loan portfolio consists of commercial and industrial and commercial real estate loans. As of June 30, 2024, there were no concentrations of loans related to any single industry in excess of 10% of total loans. At that date, the largest industry concentrations were related to the automobile dealerships industry, which totaled 5.8% of total loans and the energy industry, which totaled 5.4% of total loans. Unfunded commitments to extend credit and standby letters of credit issued to customers in the automobile dealership industry totaled $490.4 million and $20.3 million, respectively, as of June 30, 2024, while unfunded commitments to extend credit and standby letters of credit issued to customers in the energy industry totaled $1.0 billion and $65.8 million, respectively, as of June 30, 2024. Foreign Loans. We have U.S. dollar denominated loans and commitments to borrowers in Mexico. The outstanding balance of these loans and the unfunded amounts available under these commitments were not significant at June 30, 2024 or December 31, 2023. Related Party Loans . In the ordinary course of business, we have granted loans to certain directors, executive officers, and their affiliates (collectively referred to as “related parties”). Such loans totaled $281.0 million at June 30, 2024 and $416.1 million at December 31, 2023. Accrued Interest Receivable. Accrued interest receivable on loans totaled $96.2 million and $90.8 million at June 30, 2024 and December 31, 2023, respectively, and is included in accrued interest receivable and other assets in the accompanying consolidated balance sheets. Non-Accrual and Past Due Loans. Loans are considered past due if the required principal and interest payments have not been received as of the date such payments were due. Loans are placed on non-accrual status when, in management’s opinion, the borrower may be unable to meet payment obligations as they become due, as well as when required by regulatory provisions. Non-accrual loans, segregated by class of loans, were as follows: June 30, 2024 December 31, 2023 Total Non-Accrual Non-Accrual with No Credit Loss Allowance Total Non-Accrual Non-Accrual with No Credit Loss Allowance Commercial and industrial $ 26,329 $ 8,044 $ 19,545 $ 5,391 Energy 9,147 6,045 11,500 7,398 Commercial real estate: Buildings, land, and other 33,092 14,099 22,420 4,983 Construction — — — — Consumer real estate 6,419 4,188 7,442 5,160 Consumer and other — — — — Total $ 74,987 $ 32,376 $ 60,907 $ 22,932 The following table presents non-accrual loans as of June 30, 2024 by class and year of origination. 2024 2023 2022 2021 2020 Prior Revolving Loans Revolving Loans Converted to Term Total Commercial and industrial $ 746 $ 3,764 $ 1,159 $ 3,066 $ 514 $ 2,197 $ 2,149 $ 12,734 $ 26,329 Energy 4,522 — — — 56 1,321 3,102 146 9,147 Commercial real estate: Buildings, land, and other 328 20,115 3,027 5,374 — 1,411 2,837 — 33,092 Construction — — — — — — — — — Consumer real estate — — — — — 6,419 — — 6,419 Consumer and other — — — — — — — — — Total $ 5,596 $ 23,879 $ 4,186 $ 8,440 $ 570 $ 11,348 $ 8,088 $ 12,880 $ 74,987 In the table above, loans reported as 2024 originations as of June 30, 2024 were, for the most part, first originated in years prior to 2024 but were renewed in the current year. Had non-accrual loans performed in accordance with their original contract terms, we would have recognized additional interest income, net of tax, of approximately $1.3 million and $2.5 million for the three and six months ended June 30, 2024 and approximately $835 thousand and $1.4 million for the three and six months ended June 30, 2023. An age analysis of past due loans (including both accruing and non-accruing loans), segregated by class of loans, as of June 30, 2024 was as follows: Loans Loans Total Current Total Accruing Commercial and industrial $ 38,806 $ 24,640 $ 63,446 $ 6,146,733 $ 6,210,179 $ 5,568 Energy — 4,625 4,625 1,092,032 1,096,657 — Commercial real estate: Buildings, land, and other 20,272 14,620 34,892 7,462,775 7,497,667 1,687 Construction 24,535 — 24,535 1,973,010 1,997,545 — Consumer real estate 17,659 8,819 26,478 2,714,250 2,740,728 4,707 Consumer and other 5,734 577 6,311 446,669 452,980 577 Total $ 107,006 $ 53,281 $ 160,287 $ 19,835,469 $ 19,995,756 $ 12,539 Modifications to Borrowers Experiencing Financial Difficulty. From time to time, we may modify certain loans to borrowers who are experiencing financial difficulty. In some cases, these modifications may result in new loans. Loan modifications to borrowers experiencing financial difficulty may be in the form of a principal forgiveness, an interest rate reduction, an other-than-insignificant payment delay, or a term extension or a combination thereof, among other things. The period-end balance of loan modifications, segregated by type of modification, to borrowers experiencing financial difficulty during the six months ended June 30, 2024 and 2023 are set forth in the table below, regardless of whether such modifications resulted in a new loan. There were no commitments to lend additional funds to these borrowers at June 30, 2024. Combination: Payment Delay and Term Extension Percent of June 30, 2024 Commercial and industrial $ 27,731 0.4 % June 30, 2023 Commercial and industrial $ 16,020 0.3 % Commercial real estate: Buildings, land, and other 20,466 0.3 $ 36,486 0.2 The financial effects of the loan modifications made to borrowers experiencing financial difficulty were not significant during the six months ended June 30, 2024 and June 30, 2023. Furthermore, such modifications did not significantly impact our determination of the allowance for credit losses during those periods. Information as of June 30, 2024 and June 30, 2023 related to loans modified (by type of modification) in the preceding twelve months, respectively, whereby the borrower was experiencing financial difficulty at the time of modification is set forth in the following table. June 30, 2024 June 30, 2023 Combination: Payment Delay and Term Extension Combination: Payment Delay and Term Extension Past due in excess of 90 days or on non-accrual status at period-end: Commercial and industrial $ — $ 16,020 Commercial real estate: Buildings, land, and other — 20,466 $ — $ 36,486 Credit Quality Indicators. As part of the on-going monitoring of the credit quality of our loan portfolio, management tracks certain credit quality indicators including trends related to (i) the weighted-average risk grade of commercial loans, (ii) the level of classified commercial loans, (iii) the delinquency status of consumer loans, (iv) non-performing loans (see details above) and (v) the general economic conditions in the State of Texas. We utilize a risk grading matrix to assign a risk grade to each of our commercial loans. Loans are graded on a scale of 1 to 14. A description of the general characteristics of the 14 risk grades is set forth in our 2023 Form 10-K. We monitor portfolio credit quality by the weighted-average risk grade of each class of commercial loan. Individual relationship managers, under the oversight of credit administration, review updated financial information for all pass grade loans to reassess the risk grade on at least an annual basis. When a loan has a risk grade of 9, it is still considered a pass grade loan; however, it is considered to be on management’s “watch list,” where a significant risk-modifying action is anticipated in the near term. When a loan has a risk grade of 10 or higher, a special assets officer monitors the loan on an on-going basis. The following table presents weighted-average risk grades for all commercial loans, by class and year of origination/renewal, as of June 30, 2024. 2024 2023 2022 2021 2020 Prior Revolving Loans Revolving Loans Converted to Term Total W/A Risk Grade Commercial and industrial Risk grades 1-8 $ 1,095,611 $ 672,837 $ 566,640 $ 340,735 $ 310,052 $ 316,544 $ 2,208,140 $ 45,210 $ 5,555,769 6.40 Risk grade 9 16,980 9,095 65,217 10,609 5,220 9,906 92,920 4,372 214,319 9.00 Risk grade 10 1,114 434 14,799 687 218 12,285 43,049 3,775 76,361 10.00 Risk grade 11 93,737 32,948 20,080 36,358 5,840 2,046 140,163 6,229 337,401 11.00 Risk grade 12 746 2,474 1,015 3,062 503 2,197 646 9,658 20,301 12.00 Risk grade 13 — 1,290 144 4 11 — 1,503 3,076 6,028 13.00 $ 1,208,188 $ 719,078 $ 667,895 $ 391,455 $ 321,844 $ 342,978 $ 2,486,421 $ 72,320 $ 6,210,179 6.81 W/A risk grade 7.27 6.93 7.29 7.32 5.72 6.07 6.53 8.52 6.81 Energy Risk grades 1-8 $ 300,048 $ 34,672 $ 49,350 $ 49,328 $ 3,927 $ 5,041 $ 597,664 $ 6,669 $ 1,046,699 5.63 Risk grade 9 — 1,342 3,634 755 — 414 23,888 652 30,685 9.00 Risk grade 10 — — — 21 — 694 4,100 — 4,815 10.00 Risk grade 11 — — 2,075 — 72 2,945 — 219 5,311 11.00 Risk grade 12 4,522 — — — 56 1,321 402 146 6,447 12.00 Risk grade 13 — — — — — — 2,700 — 2,700 13.00 $ 304,570 $ 36,014 $ 55,059 $ 50,104 $ 4,055 $ 10,415 $ 628,754 $ 7,686 $ 1,096,657 5.83 W/A risk grade 6.11 6.80 7.00 5.88 6.56 9.00 5.44 7.32 5.83 Commercial real estate: Buildings, land, other Risk grades 1-8 $ 675,926 $ 1,431,165 $ 1,485,228 $ 1,150,261 $ 706,667 $ 1,153,397 $ 119,008 $ 96,456 $ 6,818,108 7.05 Risk grade 9 4,176 5,529 128,935 35,986 7,420 38,849 43,689 61,767 326,351 9.00 Risk grade 10 5,047 24,596 53,834 18,244 15,912 11,330 1,723 — 130,686 10.00 Risk grade 11 5,177 8,854 37,368 24,337 21,975 91,719 — — 189,430 11.00 Risk grade 12 328 15,965 3,027 5,152 — 1,411 2,593 — 28,476 12.00 Risk grade 13 — 4,150 — 222 — — 244 — 4,616 13.00 $ 690,654 $ 1,490,259 $ 1,708,392 $ 1,234,202 $ 751,974 $ 1,296,706 $ 167,257 $ 158,223 $ 7,497,667 7.31 W/A risk grade 7.21 7.31 7.39 7.34 7.17 7.18 8.02 7.53 7.31 Construction Risk grades 1-8 $ 247,162 $ 475,920 $ 575,573 $ 119,299 $ 28,003 $ 1,296 $ 149,756 $ 165 $ 1,597,174 7.32 Risk grade 9 90,634 5,282 26,585 118,546 — — 5,650 — 246,697 9.00 Risk grade 10 13,601 34,842 13,513 49,088 — — — — 111,044 10.00 Risk grade 11 — — 31,500 11,130 — — — — 42,630 11.00 Risk grade 12 — — — — — — — — — 12.00 Risk grade 13 — — — — — — — — — 13.00 $ 351,397 $ 516,044 $ 647,171 $ 298,063 $ 28,003 $ 1,296 $ 155,406 $ 165 $ 1,997,545 7.75 W/A risk grade 7.68 7.54 7.83 8.70 2.53 6.81 7.46 6.98 7.75 Total commercial real estate $ 1,042,051 $ 2,006,303 $ 2,355,563 $ 1,532,265 $ 779,977 $ 1,298,002 $ 322,663 $ 158,388 $ 9,495,212 7.40 W/A risk grade 7.36 7.37 7.51 7.61 7.00 7.18 7.75 7.53 7.40 In the table above, certain loans are reported as 2024 originations and have risk grades of 11 or higher. These loans were, for the most part, first originated in various years prior to 2024 but were renewed in the current year. The following tables present weighted average risk grades for all commercial loans by class as of December 31, 2023. Refer to our 2023 Form 10-K for details of these loans by year of origination/renewal. Commercial and Industrial Energy Commercial Real Estate - Buildings, Land and Other Commercial Real Estate - Construction Total Commercial Real Estate W/A Risk Grade Loans W/A Risk Grade Loans W/A Risk Grade Loans W/A Risk Grade Loans W/A Risk Grade Loans Risk grades 1-8 6.32 $ 5,507,878 5.73 $ 871,221 7.03 $ 6,895,358 7.27 $ 1,526,086 7.07 $ 8,421,444 Risk grade 9 9.00 205,244 9.00 27,643 9.00 173,470 9.00 127,102 9.00 300,572 Risk grade 10 10.00 109,254 10.00 818 10.00 96,601 10.00 17,035 10.00 113,636 Risk grade 11 11.00 125,261 11.00 25,555 11.00 114,071 11.00 10,501 11.00 124,572 Risk grade 12 12.00 17,102 12.00 8,800 12.00 19,770 12.00 — 12.00 19,770 Risk grade 13 13.00 2,443 13.00 2,700 13.00 2,650 13.00 — 13.00 2,650 Total 6.60 $ 5,967,182 6.05 $ 936,737 7.20 $ 7,301,920 7.45 $ 1,680,724 7.24 $ 8,982,644 Information about the payment status of consumer loans, segregated by portfolio segment and year of origination, as of June 30, 2024 was as follows: 2024 2023 2022 2021 2020 Prior Revolving Loans Revolving Loans Converted to Term Total Consumer real estate: Past due 30-89 days $ 158 $ 450 $ 1,396 $ 2,151 $ 1,005 $ 4,813 $ 7,284 $ 402 $ 17,659 Past due 90 or more days — 565 772 309 60 772 2,624 3,717 8,819 Total past due 158 1,015 2,168 2,460 1,065 5,585 9,908 4,119 26,478 Current loans 314,290 575,925 410,016 263,679 158,204 173,773 810,696 7,667 2,714,250 Total $ 314,448 $ 576,940 $ 412,184 $ 266,139 $ 159,269 $ 179,358 $ 820,604 $ 11,786 $ 2,740,728 Consumer and other: Past due 30-89 days $ 2,429 $ 174 $ 231 $ 122 $ 118 $ 64 $ 2,559 $ 37 $ 5,734 Past due 90 or more days 217 — 16 1 — — 162 181 577 Total past due 2,646 174 247 123 118 64 2,721 218 6,311 Current loans 35,410 40,943 19,574 3,921 2,691 1,457 319,622 23,051 446,669 Total $ 38,056 $ 41,117 $ 19,821 $ 4,044 $ 2,809 $ 1,521 $ 322,343 $ 23,269 $ 452,980 Period-end balances for revolving loans that converted to term during the three and six months ended June 30, 2024 and 2023 were as follows: Three Months Ended June 30, Six Months Ended June 30, 2024 2023 2024 2023 Commercial and industrial $ 10,557 $ 3,835 $ 24,813 $ 14,606 Energy 604 — 646 2,567 Commercial real estate: Buildings, land and other 65,642 5,944 66,238 5,944 Construction 165 — 165 — Consumer real estate 971 1,064 1,703 1,743 Consumer and other 3,541 1,669 6,094 3,671 Total $ 81,480 $ 12,512 $ 99,659 $ 28,531 In assessing the general economic conditions in the State of Texas, management monitors and tracks the Texas Leading Index (“TLI”), which is produced by the Federal Reserve Bank of Dallas. The TLI, the components of which are more fully described in our 2023 Form 10-K, totaled 116.9 at June 30, 2024 and 127.2 at December 31, 2023. A lower TLI value implies less favorable economic conditions. Allowance For Credit Losses - Loans. The allowance for credit losses on loans is a contra-asset valuation account, calculated in accordance with ASC 326, that is deducted from the amortized cost basis of loans to present the net amount expected to be collected. The amount of the allowance represents management's best estimate of current expected credit losses on loans considering available information, from internal and external sources, relevant to assessing collectibility over the loans' contractual terms, adjusted for expected prepayments when appropriate. Credit loss expense related to loans reflects the totality of actions taken on all loans for a particular period including any necessary increases or decreases in the allowance related to changes in credit loss expectations associated with specific loans or pools of loans. Portions of the allowance may be allocated for specific credits; however, the entire allowance is available for any credit that, in management’s judgment, should be charged off. While management utilizes its best judgment and information available, the ultimate appropriateness of the allowance is dependent upon a variety of factors beyond our control, including the performance of our loan portfolio, the economy, changes in interest rates and the view of the regulatory authorities toward loan classifications. Our allowance methodology is more fully described in our 2023 Form 10-K. During the first quarter of 2024, we updated our non-owner-occupied commercial real estate loan models as well as our consumer and other loan models. Our prior non-owner-occupied commercial real estate loan models were legacy models developed for stress-testing purposes by a third-party using external market data. The updated non-owner-occupied commercial real estate loan models are now based on internal historical loan data and risk grade information and the modeling processes are now consistent with those used with our other commercial loan models. Our prior consumer and other loan models relied upon certain components that did not use loan level attributes and were less sensitive to macroeconomic variables. The updated consumer and other loan models are now based on internal historical loan data and utilize more loan-level attributes and the modeling processes are now consistent with those used with our consumer real estate loan models. The overall approximate impact of the model updates during the first quarter was a $7.2 million increase ($6.2 million related to non-owner-occupied commercial real estate loans and $923 thousand related to consumer and other loans) in modeled expected credit losses on loans; however, the impact of this increase was largely offset by reductions in qualitative adjustments as some of the risks to which those qualitative adjustments related are now considered and incorporated in the updated models. The following table presents details of the allowance for credit losses on loans segregated by loan portfolio segment as of June 30, 2024 and December 31, 2023. June 30, 2024 Commercial Energy Commercial Consumer Consumer Total Modeled expected credit losses $ 56,937 $ 3,841 $ 20,961 $ 14,508 $ 7,415 $ 103,662 Q-Factor and other qualitative adjustments 15,589 4,944 114,443 508 3,126 138,610 Specific allocations 6,028 2,700 4,616 691 — 14,035 Total $ 78,554 $ 11,485 $ 140,020 $ 15,707 $ 10,541 $ 256,307 December 31, 2023 Modeled expected credit losses $ 50,959 $ 7,838 $ 15,443 $ 12,364 $ 5,969 $ 92,573 Q-Factor and other qualitative adjustments 20,612 7,276 112,505 433 4,071 144,897 Specific allocations 2,435 2,700 2,650 741 — 8,526 Total $ 74,006 $ 17,814 $ 130,598 $ 13,538 $ 10,040 $ 245,996 The following table details activity in the allowance for credit losses on loans by portfolio segment for the three and six months ended June 30, 2024 and 2023. Allocation of a portion of the allowance to one category of loans does not preclude its availability to absorb losses in other categories. Commercial Energy Commercial Consumer Consumer Total Three months ended: June 30, 2024 Beginning balance $ 75,596 $ 14,218 $ 138,224 $ 13,857 $ 8,402 $ 250,297 Credit loss expense (benefit) 6,936 (3,038) 1,903 2,175 7,760 15,736 Charge-offs (4,282) (79) (122) (408) (8,360) (13,251) Recoveries 304 384 15 83 2,739 3,525 Net (charge-offs) recoveries (3,978) 305 (107) (325) (5,621) (9,726) Ending balance $ 78,554 $ 11,485 $ 140,020 $ 15,707 $ 10,541 $ 256,307 June 30, 2023 Beginning balance 78,465 19,191 115,693 9,708 8,457 $ 231,514 Credit loss expense (benefit) 2,404 (4,433) 5,133 3,822 5,007 11,933 Charge-offs (7,136) (518) — (1,080) (7,016) (15,750) Recoveries 1,433 689 100 585 3,115 5,922 Net (charge-offs) recoveries (5,703) 171 100 (495) (3,901) (9,828) Ending balance $ 75,166 $ 14,929 $ 120,926 $ 13,035 $ 9,563 $ 233,619 Six months ended: June 30, 2024 Beginning balance $ 74,006 $ 17,814 $ 130,598 $ 13,538 $ 10,040 $ 245,996 Credit loss expense (benefit) 8,928 (6,814) 9,513 3,981 11,778 27,386 Charge-offs (6,426) (79) (122) (2,077) (16,617) (25,321) Recoveries 2,046 564 31 265 5,340 8,246 Net (charge-offs) recoveries (4,380) 485 (91) (1,812) (11,277) (17,075) Ending balance $ 78,554 $ 11,485 $ 140,020 $ 15,707 $ 10,541 $ 256,307 June 30, 2023 Beginning balance 104,237 18,062 90,301 8,004 7,017 $ 227,621 Credit loss expense (benefit) (18,280) (3,467) 30,494 5,105 10,756 24,608 Charge-offs (13,316) (518) — (1,330) (13,958) (29,122) Recoveries 2,525 852 131 1,256 5,748 10,512 Net (charge-offs) recoveries (10,791) 334 131 (74) (8,210) (18,610) Ending balance $ 75,166 $ 14,929 $ 120,926 $ 13,035 $ 9,563 $ 233,619 The following table presents year-to-date gross charge-offs by year of origination as of June 30, 2024. 2024 2023 2022 2021 2020 Prior Revolving Loans Revolving Loans Converted to Term Total Commercial and industrial $ — $ 471 $ 676 $ 467 $ 401 $ 625 $ 2,902 $ 884 $ 6,426 Energy — 79 — — — — — — 79 Commercial real estate: Buildings, land and other — — 122 — — — — — 122 Construction — — — — — — — — — Consumer real estate — — 148 253 — 384 1,225 67 2,077 Consumer and other 9,369 5,713 131 4 4 51 1,332 13 16,617 Total $ 9,369 $ 6,263 $ 1,077 $ 724 $ 405 $ 1,060 $ 5,459 $ 964 $ 25,321 In the table above, $9.4 million of the consumer and other loan charge-offs reported as 2024 originations and $5.5 million of the total reported as 2023 originations were related to deposit overdrafts. The following table presents loans that were evaluated for expected credit losses on an individual basis and the related specific allocations, by loan portfolio segment, as of June 30, 2024 and December 31, 2023. June 30, 2024 December 31, 2023 Loan Specific Allocations Loan Specific Allocations Commercial and industrial $ 25,508 $ 6,028 $ 18,670 $ 2,435 Energy 9,001 2,700 11,353 2,700 Commercial real estate: Buildings, land and other 32,316 4,616 21,373 2,650 Construction — — — — Consumer real estate 5,807 691 7,235 741 Consumer and other — — — — Total $ 72,632 $ 14,035 $ 58,631 $ 8,526

Deposits

Deposits	6 Months Ended
Deposits	Jun. 30, 2024
Disclosure Text Block [Abstract]
Deposits	Deposits Deposits were as follows: June 30, December 31, Non-interest-bearing demand deposits $ 13,484,977 $ 14,926,094 Interest-bearing deposits: Savings and interest checking 9,629,146 10,512,637 Money market accounts 10,899,993 10,997,279 Time accounts 6,304,024 5,484,558 Total interest-bearing deposits 26,833,163 26,994,474 Total deposits $ 40,318,140 $ 41,920,568 The table below presents additional information about our deposits. Public funds in excess of deposit insurance limits are included in the totals for deposits not covered by insurance; however, such deposits are generally fully collateralized by securities. June 30, December 31, Deposits from foreign sources (primarily Mexico) $ 1,114,319 $ 1,061,701 Non-interest-bearing public funds deposits 451,472 675,016 Interest-bearing public funds deposits 636,415 630,455 Total deposits not covered by deposit insurance 20,774,932 22,393,786 Time deposits not covered by deposit insurance 2,721,625 2,339,716

Commitments and Contingencies

Commitments and Contingencies	6 Months Ended
Commitments and Contingencies	Jun. 30, 2024
Commitments and Contingencies Disclosure [Abstract]
Commitments Contingencies and Guarantees	Off-Balance-Sheet Arrangements, Commitments, Guarantees and Contingencies Financial Instruments with Off-Balance-Sheet Risk . In the normal course of business, we enter into various transactions, which, in accordance with generally accepted accounting principles are not included in our consolidated balance sheets. We enter into these transactions to meet the financing needs of our customers. As more fully discussed in our 2023 Form 10-K, these transactions include commitments to extend credit and standby letters of credit, which involve, to varying degrees, elements of credit risk and interest rate risk in excess of the amounts recognized in the consolidated balance sheets. We minimize our exposure to loss under these commitments by subjecting them to credit approval and monitoring procedures. Financial instruments with off-balance-sheet risk were as follows: June 30, December 31, Commitments to extend credit $ 11,908,533 $ 12,195,073 Standby letters of credit 404,673 438,635 Deferred standby letter of credit fees 2,614 2,912 Allowance For Credit Losses - Off-Balance-Sheet Credit Exposures. The allowance for credit losses on off-balance-sheet credit exposures is a liability account, calculated in accordance with ASC 326, representing expected credit losses over the contractual period for which we are exposed to credit risk resulting from a contractual obligation to extend credit. No allowance is recognized if we have the unconditional right to cancel the obligation. Off-balance-sheet credit exposures primarily consist of amounts available under outstanding lines of credit and letters of credit detailed in the table above. The amount of the allowance represents management's best estimate of expected credit losses on commitments expected to be funded over the contractual life of the commitment. Our allowance methodology is more fully described in our 2023 Form 10-K. This methodology was also impacted by the model updates during the first quarter of 2024 as described in Note 3 - Loans. The overall approximate impact of the model updates was a $1.8 million increase in modeled expected credit losses for off-balance-sheet credit exposures ($1.6 million related to consumer and other loan commitments and $211 thousand related to non-owner-occupied commercial real estate loan commitments). The following table details activity in the allowance for credit losses on off-balance-sheet credit exposures. Three Months Ended Six Months Ended 2024 2023 2024 2023 Beginning balance $ 53,751 $ 54,918 $ 51,751 $ 58,593 Credit loss expense (benefit) 51 (2,037) 2,051 (5,712) Ending balance $ 53,802 $ 52,881 $ 53,802 $ 52,881 Lease Commitments . We lease certain office facilities and office equipment under operating leases. The components of total lease expense were as follows: Three Months Ended Six Months Ended 2024 2023 2024 2023 Amortization of lease right-of-use assets $ 8,829 $ 8,747 $ 17,619 $ 17,512 Short-term lease expense 394 493 719 902 Non-lease components (including taxes, insurance, common maintenance, etc.) 3,466 3,662 7,015 7,043 Total $ 12,689 $ 12,902 $ 25,353 $ 25,457 Right-of-use lease assets totaled $277.2 million at June 30, 2024 and $280.5 million at December 31, 2023 and are reported as a component of premises and equipment on our accompanying consolidated balance sheets. The related lease liabilities totaled $313.8 million at June 30, 2024 and $316.4 million at December 31, 2023 and are reported as a component of accrued interest payable and other liabilities in the accompanying consolidated balance sheets. Lease payments under operating leases that were applied to our operating lease liability totaled $8.9 million and $17.0 million during the three and six months ended June 30, 2024, respectively, and $8.2 million and $16.6 million during the three and six months ended June 30, 2023, respectively. There has been no significant change in our expected future minimum lease payments since December 31, 2023. See the 2023 Form 10-K for information regarding these commitments. Litigation.

Capital and Regulatory Matters

Capital and Regulatory Matters	6 Months Ended
Capital and Regulatory Matters	Jun. 30, 2024
Banking Regulation, Common Equity Tier 1 Risk-Based Capital [Abstract]
Capital and Regulatory Matters	Capital and Regulatory Matters Banks and bank holding companies are subject to various regulatory capital requirements administered by state and federal banking agencies. Capital adequacy guidelines and, additionally for banks, prompt corrective action regulations, involve quantitative measures of assets, liabilities, and certain off-balance-sheet items calculated under regulatory accounting practices. Capital amounts and classifications are also subject to qualitative judgments by regulators about components, risk weighting and other factors. Cullen/Frost’s and Frost Bank’s Common Equity Tier 1 capital (“CET1”) includes common stock and related paid-in capital, net of treasury stock, and retained earnings. In connection with the adoption of the Basel III Capital Rules, we elected to opt-out of the requirement to include most components of accumulated other comprehensive income in CET1. We also elected to exclude the effects of credit loss accounting under CECL from CET1 for a five-year transitional period, as further discussed in our 2023 Form 10-K. This CECL transitional adjustment totaled $15.4 million and $30.8 million at June 30, 2024 and December 31, 2023, respectively. CET1 is reduced by goodwill and other intangible assets, net of associated deferred tax liabilities. Frost Bank's CET1 is also reduced by its equity investment in its financial subsidiary, Frost Insurance Agency (“FIA”). Tier 1 capital includes CET1 and additional Tier 1 capital. For Cullen/Frost, additional Tier 1 capital included $145.5 million of 4.450% non-cumulative perpetual preferred stock at June 30, 2024 and December 31, 2023, the details of which are further discussed below. Frost Bank did not have any additional Tier 1 capital beyond Common Equity Tier 1 at June 30, 2024 or December 31, 2023. Total capital includes Tier 1 capital and Tier 2 capital. Tier 2 capital for both Cullen/Frost and Frost Bank includes a permissible portion of the allowances for credit losses on securities, loans, and off-balance-sheet credit exposures. Tier 2 capital for Cullen/Frost also includes the permissible portion of qualified subordinated debt (which decreases 20.0% per year during the final five The following table presents actual and required capital ratios as of June 30, 2024 and December 31, 2023 for Cullen/Frost and Frost Bank under the Basel III Capital Rules. Capital levels required to be considered well-capitalized are based upon prompt corrective action regulations, as amended to reflect the changes under the Basel III Capital Rules. See the 2023 Form 10-K for a more detailed discussion of the Basel III Capital Rules. Actual Minimum Capital Required Plus Capital Conservation Buffer Required to be Considered Well- Capitalized (1) Capital Ratio Capital Ratio Capital Ratio June 30, 2024 Common Equity Tier 1 to Risk-Weighted Assets Cullen/Frost $ 4,164,990 13.35 % $ 2,183,331 7.00 % N/A N/A Frost Bank 4,228,311 13.56 2,182,110 7.00 $ 2,026,245 6.50 % Tier 1 Capital to Risk-Weighted Assets Cullen/Frost 4,310,442 13.82 2,651,188 8.50 1,871,427 6.00 Frost Bank 4,228,311 13.56 2,649,705 8.50 2,493,840 8.00 Total Capital to Risk-Weighted Assets Cullen/Frost 4,763,514 15.27 3,274,997 10.50 3,119,044 10.00 Frost Bank 4,521,383 14.50 3,273,165 10.50 3,117,300 10.00 Leverage Ratio Cullen/Frost 4,310,442 8.62 1,999,776 4.00 N/A N/A Frost Bank 4,228,311 8.46 1,999,934 4.00 2,499,918 5.00 December 31, 2023 Common Equity Tier 1 to Risk-Weighted Assets Cullen/Frost $ 4,036,945 13.25 % $ 2,132,516 7.00 % N/A N/A Frost Bank 4,057,111 13.33 2,129,784 7.00 $ 1,977,656 6.50 % Tier 1 Capital to Risk-Weighted Assets Cullen/Frost 4,182,397 13.73 2,589,484 8.50 1,827,871 6.00 Frost Bank 4,057,111 13.33 2,586,166 8.50 2,434,038 8.00 Total Capital to Risk-Weighted Assets Cullen/Frost 4,625,760 15.18 3,198,774 10.50 3,046,452 10.00 Frost Bank 4,320,474 14.20 3,194,676 10.50 3,042,548 10.00 Leverage Ratio Cullen/Frost 4,182,397 8.35 2,003,020 4.00 N/A N/A Frost Bank 4,057,111 8.10 2,003,152 4.00 2,503,940 5.00 ____________________ (1) “Well-capitalized” minimum Common Equity Tier 1 to Risk-Weighted Assets and Leverage Ratio are not formally defined under applicable banking regulations for bank holding companies. As of June 30, 2024, capital levels at Cullen/Frost and Frost Bank exceed all capital adequacy requirements under the Basel III Capital Rules. Based on the ratios presented above, capital levels as of June 30, 2024 at Cullen/Frost and Frost Bank exceed the minimum levels necessary to be considered “well-capitalized.” Cullen/Frost and Frost Bank are subject to the regulatory capital requirements administered by the Federal Reserve Board and, for Frost Bank, the Federal Deposit Insurance Corporation (“FDIC”). Regulatory authorities can initiate certain mandatory actions if Cullen/Frost or Frost Bank fail to meet the minimum capital requirements, which could have a direct material effect on our financial statements. Management believes, as of June 30, 2024, that Cullen/Frost and Frost Bank meet all capital adequacy requirements to which they are subject. Preferred Stock. Outstanding preferred stock includes 150,000 shares, or $150.0 million in aggregate liquidation preference, of our 4.450% Non-Cumulative Perpetual Preferred Stock, Series B, par value $0.01 and liquidation preference $1,000 per share (“Series B Preferred Stock”). Each share of Series B Preferred Stock issued and outstanding is represented by 40 depositary shares, each representing a 1/40th ownership interest in a share of the Series B Preferred Stock (equivalent to a liquidation preference of $25 per share). The Series B Preferred Stock qualifies as Tier 1 capital for the purposes of the regulatory capital calculations. The net proceeds from the issuance and sale of the Series B Preferred Stock, after deducting $4.5 million of issuance costs including the underwriting discount and professional service fees, among other things, were approximately $145.5 million. Refer to our 2023 Form 10-K for additional details related to our Series B Preferred Stock. Stock Repurchase Plans. From time to time, our board of directors has authorized stock repurchase plans. The purpose of such plans and the manner in which shares are repurchased is discussed in more detail in our 2023 Form 10-K. Most recently, on January 24, 2024, our board of directors authorized a $150.0 million stock repurchase program (the “2024 Repurchase Plan”), allowing us to repurchase shares of our common stock over a one Dividend Restrictions . In the ordinary course of business, Cullen/Frost is dependent upon dividends from Frost Bank to provide funds for the payment of dividends to shareholders and to provide for other cash requirements, including to repurchase its common stock. Banking regulations may limit the amount of dividends that may be paid. Approval by regulatory authorities is required if the effect of dividends declared would cause the regulatory capital of Frost Bank to fall below specified minimum levels. Approval is also required if dividends declared exceed the net profits for that year combined with the retained net profits for the preceding two years. Under the foregoing dividend restrictions and while maintaining its “well-capitalized” status, at June 30, 2024, Frost Bank could pay aggregate dividends of up to $1.0 billion to Cullen/Frost without prior regulatory approval. Under the terms of the junior subordinated deferrable interest debentures that Cullen/Frost has issued to Cullen/Frost Capital Trust II, Cullen/Frost has the right at any time during the term of the debentures to defer the payment of interest at any time or from time to time for an extension period not exceeding 20 consecutive quarterly periods with respect to each extension period. In the event that we have elected to defer interest on the debentures, we may not, with certain exceptions, declare or pay any dividends or distributions on our capital stock or purchase or acquire any of our capital stock. Under the terms of the Series B Preferred Stock, in the event that we do not declare and pay dividends on the Series B Preferred Stock for the most recent dividend period, we may not, with certain exceptions, declare or pay dividends on, or purchase, redeem or otherwise acquire, shares of our common stock or any of our securities that rank junior to the Series B Preferred Stock.

Derivative Financial Instrument

Derivative Financial Instruments	6 Months Ended
Derivative Financial Instruments	Jun. 30, 2024
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Derivative Financial Instruments	Derivative Financial Instruments The fair value of derivative positions outstanding is included in accrued interest receivable and other assets and accrued interest payable and other liabilities in the accompanying consolidated balance sheets and in the net change in each of these financial statement line items in the accompanying consolidated statements of cash flows. Interest Rate Derivatives. We utilize various interest rate swaps, caps, and floors, among other things, to mitigate exposure to interest rate risk and to facilitate the needs of our customers. Our objectives for utilizing these derivative instruments are described in our 2023 Form 10-K. The notional amounts and estimated fair values of interest rate derivative contracts are presented in the following table. The fair values of interest rate derivative contracts are estimated utilizing internal valuation methods with observable market data inputs, or as determined by the Chicago Mercantile Exchange (“CME”) for centrally cleared derivative contracts. CME rules legally characterize variation margin payments for centrally cleared derivatives as settlements of the derivatives' exposure rather than collateral. As a result, the variation margin payment and the related derivative instruments are considered a single unit of account for accounting and financial reporting purposes. Variation margin, as determined by the CME, is settled daily. As a result, derivative contracts that clear through the CME have an estimated fair value of zero as of June 30, 2024 and December 31, 2023. June 30, 2024 December 31, 2023 Notional Estimated Notional Estimated Non-hedging interest rate derivatives: Financial institution counterparties: Loan/lease interest rate swaps – assets 1,176,104 $ 70,070 1,040,659 $ 58,486 Loan/lease interest rate swaps – liabilities 553,195 (7,166) 617,266 (20,293) Loan/lease interest rate caps – assets 235,699 10,021 275,000 11,747 Customer counterparties: Loan/lease interest rate swaps – assets 553,195 7,166 617,266 20,482 Loan/lease interest rate swaps – liabilities 1,176,104 (70,069) 1,040,659 (58,485) Loan/lease interest rate caps – liabilities 235,699 (10,019) 275,000 (11,747) The weighted-average rates paid and received for interest rate swaps outstanding at June 30, 2024 were as follows: Weighted-Average Interest Interest Interest rate swaps: Non-hedging interest rate swaps – financial institution counterparties 4.98 % 7.08 % Non-hedging interest rate swaps – customer counterparties 7.08 4.98 The weighted-average strike rate for outstanding interest rate caps was 3.58% at June 30, 2024. Commodity Derivatives. We enter into commodity swaps and option contracts that are not designated as hedging instruments primarily to accommodate the business needs of our customers. Upon the origination of a commodity swap or option contract with a customer, we simultaneously enter into an offsetting contract with a third-party financial institution to mitigate the exposure to fluctuations in commodity prices. The notional amounts and estimated fair values of non-hedging commodity swap and option derivative positions outstanding are presented in the following table. We obtain dealer quotations and use internal valuation methods with observable market data inputs to value our commodity derivative positions. June 30, 2024 December 31, 2023 Notional Notional Estimated Notional Estimated Financial institution counterparties: Oil – assets Barrels 4,541 $ 14,580 5,601 $ 37,667 Oil – liabilities Barrels 7,437 (28,552) 4,581 (18,500) Natural gas – assets MMBTUs 21,934 8,831 17,363 11,822 Natural gas – liabilities MMBTUs 10,785 (3,474) 6,462 (2,499) Customer counterparties: Oil – assets Barrels 7,498 29,330 4,618 18,722 Oil – liabilities Barrels 4,480 (14,315) 5,564 (36,877) Natural gas – assets MMBTUs 12,693 3,552 6,462 2,499 Natural gas – liabilities MMBTUs 20,025 (8,478) 17,363 (11,571) Foreign Currency Derivatives . We enter into foreign currency forward and option contracts that are not designated as hedging instruments primarily to accommodate the business needs of our customers. Upon the origination of a foreign currency denominated transaction with a customer, we simultaneously enter into an offsetting contract with a third-party financial institution to negate the exposure to fluctuations in foreign currency exchange rates. We also utilize foreign currency forward contracts and options that are not designated as hedging instruments to mitigate the economic effect of fluctuations in foreign currency exchange rates on foreign currency holdings and certain short-term, non-U.S. dollar denominated loans. The notional amounts and fair values of open foreign currency forward and option contracts are presented in the following table. June 30, 2024 December 31, 2023 Notional Notional Estimated Notional Estimated Financial institution counterparties: Forward and option contracts – assets CAD — $ — 250 $ 1 Forward and option contracts – liabilities EUR — — 3,000 (14) Forward and option contracts – liabilities CAD — — 250 (5) Customer counterparties: Forward and option contracts – assets EUR — — 3,000 16 Forward and option contracts – assets CAD — — 250 5 Forward and option contracts – liabilities CAD — — 250 — Gains, Losses, and Derivative Cash Flows . For fair value hedges, the changes in the fair value of both the derivative hedging instrument and the hedged item are included in other non-interest income or other non-interest expense. The extent that such changes in fair value do not offset represents hedge ineffectiveness. Net cash flows from interest rate swaps on commercial loans/leases designated as hedging instruments in effective hedges of fair value are included in interest income on loans. For non-hedging derivative instruments, gains and losses due to changes in fair value and all cash flows are included in other non-interest income and other non-interest expense. Amounts included in the consolidated statements of income related to interest rate derivatives designated as hedges of fair value were as follows: Three Months Ended Six Months Ended 2024 2023 2024 2023 Commercial loan/lease interest rate swaps: Amount of gain (loss) included in interest income on loans $ — $ 4 $ — $ 16 Amount of (gain) loss included in other non-interest expense — 4 — 4 As stated above, we enter into non-hedge related derivative positions primarily to accommodate the business needs of our customers. Upon the origination of a derivative contract with a customer, we simultaneously enter into an offsetting derivative contract with a third-party financial institution. We recognize immediate income based upon the difference in the bid/ask spread of the underlying transactions with our customers and the third party. Because we act only as an intermediary for our customer, subsequent changes in the fair value of the underlying derivative contracts for the most part offset each other and do not significantly impact our results of operations. Amounts included in the consolidated statements of income related to non-hedge related derivative instruments are presented in the table below. Three Months Ended Six Months Ended 2024 2023 2024 2023 Non-hedging interest rate derivatives: Other non-interest income $ 512 $ 1,002 $ 1,637 $ 1,712 Other non-interest expense 3 1 3 — Non-hedging commodity derivatives: Other non-interest income 946 503 1,325 925 Non-hedging foreign currency derivatives: Other non-interest income — — 11 25 Counterparty Credit Risk.

Balance Sheet Offsetting

Balance Sheet Offsetting	6 Months Ended
Balance Sheet Offsetting	Jun. 30, 2024
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Balance Sheet Offsetting	Balance Sheet Offsetting and Repurchase Agreements Balance Sheet Offsetting. Certain financial instruments, including resell and repurchase agreements and derivatives, may be eligible for offset in the consolidated balance sheet and/or subject to master netting arrangements or similar agreements. Our derivative transactions with upstream financial institution 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. Nonetheless, we do not generally offset such financial instruments for financial reporting purposes. Information about financial instruments that are eligible for offset in the consolidated balance sheet as of June 30, 2024 is presented in the following tables. Gross Amount Gross Amount Net Amount June 30, 2024 Financial assets: Derivatives: Interest rate contracts $ 80,091 $ — $ 80,091 Commodity contracts 23,411 — 23,411 Total derivatives 103,502 — 103,502 Resell agreements 84,650 — 84,650 Total $ 188,152 $ — $ 188,152 Financial liabilities: Derivatives: Interest rate contracts $ 7,166 $ — $ 7,166 Commodity contracts 32,026 — 32,026 Total derivatives 39,192 — 39,192 Repurchase agreements 3,762,942 — 3,762,942 Total $ 3,802,134 $ — $ 3,802,134 Gross Amounts Not Offset Net Amount Financial Collateral Net June 30, 2024 Financial assets: Derivatives: Counterparty H $ 32,594 $ (15,265) $ (16,030) $ 1,299 Counterparty F 16,299 (10,399) (3,889) 2,011 Counterparty B 24,125 (6,362) (16,870) 893 Counterparty E 15,855 (1,913) (13,040) 902 Other counterparties 14,629 (5,253) (8,294) 1,082 Total derivatives 103,502 (39,192) (58,123) 6,187 Resell agreements 84,650 — (84,650) — Total $ 188,152 $ (39,192) $ (142,773) $ 6,187 Financial liabilities: Derivatives: Counterparty H $ 15,265 $ (15,265) $ — $ — Counterparty F 10,399 (10,399) — — Counterparty B 6,362 (6,362) — — Counterparty E 1,913 (1,913) — — Other counterparties 5,253 (5,253) — — Total derivatives 39,192 (39,192) — — Repurchase agreements 3,762,942 — (3,762,942) — Total $ 3,802,134 $ (39,192) $ (3,762,942) $ — Information about financial instruments that are eligible for offset in the consolidated balance sheet as of December 31, 2023 is presented in the following tables. Gross Amount Gross Amount Net Amount December 31, 2023 Financial assets: Derivatives: Interest rate contracts $ 70,233 $ — $ 70,233 Commodity contracts 49,489 — 49,489 Foreign currency contracts 1 — 1 Total derivatives 119,723 — 119,723 Resell agreements 84,650 — 84,650 Total $ 204,373 $ — $ 204,373 Financial liabilities: Derivatives: Interest rate contracts $ 20,293 $ — $ 20,293 Commodity contracts 20,999 — 20,999 Foreign currency contracts 19 — 19 Total derivatives 41,311 — 41,311 Repurchase agreements 4,127,188 — 4,127,188 Total $ 4,168,499 $ — $ 4,168,499 Gross Amounts Not Offset Net Amount Financial Collateral Net December 31, 2023 Financial assets: Derivatives: Counterparty H $ 36,551 $ (8,870) $ (27,170) $ 511 Counterparty F 31,202 (7,444) (22,954) 804 Counterparty B 23,829 (5,151) (18,472) 206 Counterparty E 13,271 (4,548) (8,723) — Other counterparties 14,870 (6,418) (7,520) 932 Total derivatives 119,723 (32,431) (84,839) 2,453 Resell agreements 84,650 — (84,650) — Total $ 204,373 $ (32,431) $ (169,489) $ 2,453 Financial liabilities: Derivatives: Counterparty H $ 8,870 $ (8,870) $ — $ — Counterparty F 7,444 (7,444) — — Counterparty B 5,151 (5,151) — — Counterparty E 4,548 (4,548) — — Other counterparties 15,298 (6,418) (8,580) 300 Total derivatives 41,311 (32,431) (8,580) 300 Repurchase agreements 4,127,188 — (4,127,188) — Total $ 4,168,499 $ (32,431) $ (4,135,768) $ 300 Repurchase Agreements. We utilize securities sold under agreements to repurchase to facilitate the needs of our customers and to facilitate secured short-term funding needs. Securities sold under agreements to repurchase are stated at the amount of cash received in connection with the transaction. We monitor collateral levels on a continuous basis. We may be required to provide additional collateral based on the fair value of the underlying securities. Securities pledged as collateral under repurchase agreements are maintained with our safekeeping agents. The remaining contractual maturity of repurchase agreements in the consolidated balance sheets as of June 30, 2024 and December 31, 2023 is presented in the following tables. Remaining Contractual Maturity of the Agreements Overnight and Continuous Up to 30 Days 30-90 Days Greater than 90 Days Total June 30, 2024 Repurchase agreements: U.S. Treasury $ 1,889,019 $ — $ — $ — $ 1,889,019 Residential mortgage-backed securities 1,873,923 — — — 1,873,923 Total borrowings $ 3,762,942 $ — $ — $ — $ 3,762,942 Gross amount of recognized liabilities for repurchase agreements $ 3,762,942 Amounts related to agreements not included in offsetting disclosures above $ — December 31, 2023 Repurchase agreements: U.S. Treasury $ 3,300,662 $ — $ — $ — $ 3,300,662 Residential mortgage-backed securities 826,526 — — — 826,526 Total borrowings $ 4,127,188 $ — $ — $ — $ 4,127,188 Gross amount of recognized liabilities for repurchase agreements $ 4,127,188 Amounts related to agreements not included in offsetting disclosures above $ —

Stock-Based Compensation

Stock-Based Compensation	6 Months Ended
Stock-Based Compensation	Jun. 30, 2024
Share-Based Payment Arrangement [Abstract]
Stock-Based Compensation	Stock-Based Compensation A combined summary of activity in our active stock plans is presented in the table below. Performance stock units outstanding are presented assuming attainment of the maximum payout rate as set forth by the performance criteria. On April 24, 2024, the shareholders of Cullen/Frost approved the 2024 Equity Incentive Plan (the “2024 Plan”) to replace the 2015 Omnibus Incentive Plan (the “2015 Plan”). Under the 2024 Plan, shareholders approved the issuance, pursuant to the plan, of 2,576,038 shares of our common stock. This amount included 2,350,000 newly authorized shares and the 226,038 shares remaining available for issuance under the superseded 2015 Plan. As of June 30, 2024, there were 2,567,893 shares remaining available for grant for future stock-based compensation awards. Deferred Non-Vested Performance Stock Options Number Weighted- Number Weighted- Number Weighted- Number Weighted- Balance, January 1, 2024 54,164 $ 89.71 566,806 $ 99.77 267,054 $ 89.99 485,941 $ 71.25 Granted 7,997 116.84 2,826 107.95 — — — — Exercised/vested (9,382) 80.99 (458) 65.43 (45,818) 57.89 (66,970) 77.79 Forfeited/expired — — (1,408) 106.18 (22,913) 57.89 — — Balance, June 30, 2024 52,779 95.37 567,766 99.82 198,323 101.12 418,971 70.20 Shares issued in connection with stock compensation awards are issued from available treasury shares. If no treasury shares are available, new shares are issued from available authorized shares. Shares issued in connection with stock compensation awards along with other related information were as follows: Three Months Ended Six Months Ended 2024 2023 2024 2023 New shares issued from available authorized shares — — — 49,887 Shares issued from available treasury stock 38,452 13,626 122,628 14,126 Proceeds from stock option exercises $ 2,294 $ 946 $ 5,209 $ 2,446 Stock-based compensation expense is recognized ratably over the requisite service period for all awards. For most stock option awards, the service period generally matches the vesting period. For stock options granted to certain executive officers and for non-vested stock units granted to all participants, the service period does not extend past the date the participant reaches 65 years of age. Deferred stock units granted to non-employee directors generally have immediate vesting and the related expense is fully recognized on the date of grant. For performance stock units, the service period generally matches the three-year performance period specified by the award, however, the service period does not extend past the date the participant reaches 65 years of age. Expense recognized each period is dependent upon our estimate of the number of shares that will ultimately be issued. Stock-based compensation expense or benefit and the related income tax benefit is presented in the following table. The service period for performance stock units granted each year begins on January 1 of the following year. Three Months Ended Six Months Ended 2024 2023 2024 2023 Non-vested stock units $ 3,100 $ 2,864 $ 6,479 $ 6,171 Deferred stock units 934 880 934 880 Performance stock units 489 1,049 848 2,484 Total $ 4,523 $ 4,793 $ 8,261 $ 9,535 Income tax benefit $ 846 $ 800 $ 1,991 $ 1,868 Unrecognized stock-based compensation expense at June 30, 2024 is presented in the table below. Unrecognized stock-based compensation expense related to performance stock units is presented assuming attainment of the maximum payout rate as set forth by the performance criteria. Non-vested stock units $ 16,341 Performance stock units 7,583 Total $ 23,924

Earnings Per Common Share

Earnings Per Common Share	6 Months Ended
Earnings Per Common Share	Jun. 30, 2024
Earnings Per Share [Abstract]
Earnings Per Common Share	Earnings Per Common Share Earnings per common share is computed using the two-class method as more fully described in our 2023 Form 10-K. The following table presents a reconciliation of net income available to common shareholders, net earnings allocated to common stock and the number of shares used in the calculation of basic and diluted earnings per common share. Three Months Ended Six Months Ended 2024 2023 2024 2023 Net income $ 145,499 $ 162,118 $ 281,189 $ 339,771 Less: Preferred stock dividends 1,669 1,669 3,338 3,338 Net income available to common shareholders 143,830 160,449 277,851 336,433 Less: Earnings allocated to participating securities 1,693 1,645 3,334 3,468 Net earnings allocated to common stock $ 142,137 $ 158,804 $ 274,517 $ 332,965 Distributed earnings allocated to common stock $ 59,108 $ 55,783 $ 118,188 $ 111,789 Undistributed earnings allocated to common stock 83,029 103,021 156,329 221,176 Net earnings allocated to common stock $ 142,137 $ 158,804 $ 274,517 $ 332,965 Weighted-average shares outstanding for basic earnings per common share 64,192,907 64,240,789 64,204,615 64,306,809 Dilutive effect of stock compensation 140,280 187,172 147,693 225,267 Weighted-average shares outstanding for diluted earnings per common share 64,333,187 64,427,961 64,352,308 64,532,076

Defined Benefit Plans

Defined Benefit Plans	6 Months Ended
Defined Benefit Plans	Jun. 30, 2024
Retirement Benefits [Abstract]
Defined Benefit Plans	Defined Benefit Plans The components of the combined net periodic expense (benefit) for our defined benefit pension plans are presented in the table below. Three Months Ended Six Months Ended 2024 2023 2024 2023 Expected return on plan assets, net of expenses $ (2,412) $ (2,740) $ (4,823) $ (5,480) Interest cost on projected benefit obligation 1,661 1,746 3,323 3,492 Net amortization and deferral 419 870 837 1,740 Net periodic expense (benefit) $ (332) $ (124) $ (663) $ (248) Our non-qualified defined benefit pension plan is not funded. No contributions to the qualified defined benefit pension plan were made during the six months ended June 30, 2024. We do not expect to make any contributions to the qualified defined benefit plan during the remainder of 2024.

Income Taxes

Income Taxes	6 Months Ended
Income Taxes	Jun. 30, 2024
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes Income tax expense was as follows: Three Months Ended Six Months Ended 2024 2023 2024 2023 Current income tax expense $ 32,919 $ 32,413 $ 63,236 $ 67,408 Deferred income tax expense (benefit) (3,267) (680) (7,713) (2,489) Income tax expense, as reported $ 29,652 $ 31,733 $ 55,523 $ 64,919 Effective tax rate 16.9 % 16.4 % 16.5 % 16.0 % We had a net deferred tax asset totaling $386.6 million at June 30, 2024 and $328.3 million at December 31, 2023. No valuation allowance for deferred tax assets was recorded as of those dates as management believes it is more likely than not that all of the deferred tax assets will be realized against deferred tax liabilities and projected future taxable income. The effective income tax rates differed from the U.S. statutory federal income tax rates of 21% during the comparable periods primarily due to the effect of tax-exempt income from securities, loans and life insurance policies and the income tax effects associated with stock-based compensation, among other things. There were no unrecognized tax benefits during any of the reported periods. Interest and/or penalties related to income taxes are reported as a component of income tax expense. Such amounts were not significant during the reported periods. We file income tax returns in the U.S. federal jurisdiction. We are no longer subject to U.S. federal income tax examinations by tax authorities for years before 2020.

Other Comprehensive Income (Los

Other Comprehensive Income (Loss)	6 Months Ended
Other Comprehensive Income (Loss)	Jun. 30, 2024
Equity [Abstract]
Comprehensive Income (Loss) Note	Other Comprehensive Income (Loss) The before and after-tax amounts allocated to each component of other comprehensive income (loss) are presented in the following table. Reclassification adjustments related to securities available for sale are included in net gain (loss) on securities transactions in the accompanying consolidated statements of income. Reclassification adjustments related to defined-benefit post-retirement benefit plans are included in the computation of net periodic pension expense (see Note 11 – Defined Benefit Plans). Three Months Ended Three Months Ended Before Tax Tax Expense, Net of Tax Before Tax Tax Expense, Net of Tax Securities available for sale and transferred securities: Change in net unrealized gain/loss during the period $ (42,111) $ (8,843) $ (33,268) $ (206,863) $ (43,441) $ (163,422) Change in net unrealized gain on securities transferred to held to maturity (157) (33) (124) (162) (34) (128) Reclassification adjustment for net (gains) losses included in net income — — — (33) (7) (26) Total securities available for sale and transferred securities (42,268) (8,876) (33,392) (207,058) (43,482) (163,576) Defined-benefit post-retirement benefit plans: Reclassification adjustment for net amortization of actuarial gain/loss included in net income as a component of net periodic cost (benefit) 419 88 331 870 183 687 Total defined-benefit post-retirement benefit plans 419 88 331 870 183 687 Total other comprehensive income (loss) $ (41,849) $ (8,788) $ (33,061) $ (206,188) $ (43,299) $ (162,889) Six Months Ended Six Months Ended Before Tax Tax Expense, Net of Tax Before Tax Tax Expense, Net of Tax Securities available for sale and transferred securities: Change in net unrealized gain/loss during the period $ (241,186) $ (50,649) $ (190,537) $ 53,406 $ 11,215 $ 42,191 Change in net unrealized gain on securities transferred to held to maturity (316) (67) (249) (322) (67) (255) Reclassification adjustment for net (gains) losses included in net income — — — (54) (11) (43) Total securities available for sale and transferred securities (241,502) (50,716) (190,786) 53,030 11,137 41,893 Defined-benefit post-retirement benefit plans: Reclassification adjustment for net amortization of actuarial gain/loss included in net income as a component of net periodic expense (benefit) 837 176 661 1,740 366 1,374 Total defined-benefit post-retirement benefit plans 837 176 661 1,740 366 1,374 Total other comprehensive income (loss) $ (240,665) $ (50,540) $ (190,125) $ 54,770 $ 11,503 $ 43,267 Activity in accumulated other comprehensive income (loss), net of tax, was as follows: Securities Defined Accumulated Balance at January 1, 2024 $ (1,094,794) $ (24,425) $ (1,119,219) Other comprehensive income (loss) before reclassifications (190,786) — (190,786) Reclassification of amounts included in net income — 661 661 Net other comprehensive income (loss) during period (190,786) 661 (190,125) Balance at June 30, 2024 $ (1,285,580) $ (23,764) $ (1,309,344) Balance at January 1, 2023 $ (1,313,791) $ (34,503) $ (1,348,294) Other comprehensive income (loss) before reclassifications 41,936 — 41,936 Reclassification of amounts included in net income (43) 1,374 1,331 Net other comprehensive income (loss) during period 41,893 1,374 43,267 Balance at June 30, 2023 $ (1,271,898) $ (33,129) $ (1,305,027)

Operating Segments

Operating Segments	6 Months Ended
Operating Segments	Jun. 30, 2024
Segment Reporting [Abstract]
Operating Segments	Operating Segments We are managed under a matrix organizational structure whereby our two primary operating segments, Banking and Frost Wealth Advisors, overlap a regional reporting structure. See our 2023 Form 10-K for additional information about our operating segments and related accounting policies. Summarized operating results by operating segment were as follows: Banking Frost Wealth Non-Banks Consolidated Three months ended: June 30, 2024 Net interest income (expense) $ 398,270 $ 1,907 $ (3,465) $ 396,712 Credit loss expense 15,787 — — 15,787 Non-interest income 62,178 49,489 (477) 111,190 Non-interest expense 276,196 37,875 2,893 316,964 Income (loss) before income taxes 168,465 13,521 (6,835) 175,151 Income tax expense (benefit) 28,819 2,839 (2,006) 29,652 Net income (loss) 139,646 10,682 (4,829) 145,499 Preferred stock dividends — — 1,669 1,669 Net income (loss) available to common shareholders $ 139,646 $ 10,682 $ (6,498) $ 143,830 Revenues from (expenses to) external customers $ 460,448 $ 51,396 $ (3,942) $ 507,902 June 30, 2023 Net interest income (expense) $ 385,720 $ 2,090 $ (2,544) $ 385,266 Credit loss expense (benefit) 9,901 — — 9,901 Non-interest income 57,808 46,147 (427) 103,528 Non-interest expense 246,927 35,558 2,557 285,042 Income (loss) before income taxes 186,700 12,679 (5,528) 193,851 Income tax expense (benefit) 30,636 2,663 (1,566) 31,733 Net income (loss) 156,064 10,016 (3,962) 162,118 Preferred stock dividends — — 1,669 1,669 Net income (loss) available to common shareholders $ 156,064 $ 10,016 $ (5,631) $ 160,449 Revenues from (expenses to) external customers $ 443,528 $ 48,237 $ (2,971) $ 488,794 Banking Frost Wealth Non-Banks Consolidated Six months ended: June 30, 2024 Net interest income (expense) $ 790,075 $ 3,576 $ (6,888) $ 786,763 Credit loss expense (benefit) 29,437 — — 29,437 Non-interest income 128,558 94,915 (906) 222,567 Non-interest expense 563,026 75,848 4,307 643,181 Income (loss) before income taxes 326,170 22,643 (12,101) 336,712 Income tax expense (benefit) 54,454 4,755 (3,686) 55,523 Net income (loss) 271,716 17,888 (8,415) 281,189 Preferred stock dividends — — 3,338 3,338 Net income (loss) available to common shareholders $ 271,716 $ 17,888 $ (11,753) $ 277,851 Revenues from (expenses to) external customers $ 918,633 $ 98,491 $ (7,794) $ 1,009,330 June 30, 2023 Net interest income (expense) $ 785,857 $ 3,744 $ (4,515) $ 785,086 Credit loss expense 19,005 — — 19,005 Non-interest income 121,451 88,185 (843) 208,793 Non-interest expense 496,792 69,507 3,885 570,184 Income (loss) before income taxes 391,511 22,422 (9,243) 404,690 Income tax expense (benefit) 62,754 4,709 (2,544) 64,919 Net income (loss) 328,757 17,713 (6,699) 339,771 Preferred stock dividends — — 3,338 3,338 Net income (loss) available to common shareholders $ 328,757 $ 17,713 $ (10,037) $ 336,433 Revenues from (expenses to) external customers $ 907,308 $ 91,929 $ (5,358) $ 993,879

Fair Value Measurements

Fair Value Measurements	6 Months Ended
Fair Value Measurements	Jun. 30, 2024
Fair Value Disclosures [Abstract]
Fair Value Measurements	Fair Value Measurements The fair value of an asset or liability is the price that would be received to sell that asset or paid to transfer that liability in an orderly transaction occurring in the principal market (or most advantageous market in the absence of a principal market) for such asset or liability. In estimating fair value, we utilize valuation techniques that are consistent with the market approach, the income approach and/or the cost approach. Such valuation techniques are consistently applied. Inputs to valuation techniques include the assumptions that market participants would use in pricing an asset or liability. ASC Topic 820 establishes a three-level fair value hierarchy for valuation inputs that gives the highest priority to quoted prices in active markets for identical assets or liabilities and the lowest priority to unobservable inputs. See our 2023 Form 10-K for additional information regarding the fair value hierarchy and a description of our valuation techniques. Financial Assets and Financial Liabilities. The tables below summarize financial assets and financial liabilities measured at fair value on a recurring basis as of June 30, 2024 and December 31, 2023, segregated by the level of the valuation inputs within the fair value hierarchy of ASC Topic 820 utilized to measure fair value. Level 1 Inputs Level 2 Inputs Level 3 Inputs Total Fair Value June 30, 2024 Securities available for sale: U.S. Treasury $ 3,882,331 $ — $ — $ 3,882,331 Residential mortgage-backed securities — 6,537,427 — 6,537,427 States and political subdivisions — 4,734,909 — 4,734,909 Other — 42,971 — 42,971 Trading account securities: U.S. Treasury 31,400 — — 31,400 States and political subdivisions — 786 — 786 Derivative assets: Interest rate swaps, caps, and floors — 87,257 — 87,257 Commodity swaps and options — 56,293 — 56,293 Derivative liabilities: Interest rate swaps, caps, and floors — 87,254 — 87,254 Commodity swaps and options — 54,819 — 54,819 December 31, 2023 Securities available for sale: U.S. Treasury $ 4,927,589 $ — $ — $ 4,927,589 Residential mortgage-backed securities — 6,596,682 — 6,596,682 States and political subdivisions — 5,011,331 — 5,011,331 Other — 42,769 — 42,769 Trading account securities: U.S. Treasury 30,265 — — 30,265 States and political subdivisions — 1,452 — 1,452 Derivative assets: Interest rate swaps, caps, and floors — 90,715 — 90,715 Commodity swaps and options — 70,710 — 70,710 Foreign currency forward contracts 22 — — 22 Derivative liabilities: Interest rate swaps, caps, and floors — 90,525 — 90,525 Commodity swaps and options — 69,447 — 69,447 Foreign currency forward contracts 19 — — 19 Certain financial assets and financial liabilities are measured at fair value on a nonrecurring basis; that is, the instruments are not measured at fair value on an ongoing basis but are subject to fair value adjustments in certain circumstances. Financial assets measured at fair value on a non-recurring basis during the reported periods include certain collateral dependent loans reported at the fair value of the underlying collateral if repayment is expected solely from the collateral. The following table presents collateral dependent loans that were remeasured and reported at fair value through a specific allocation of the allowance for credit losses on loans based upon the fair value of the underlying collateral during the reported periods. Six Months Ended Six Months Ended Level 2 Level 3 Level 2 Level 3 Carrying value before allocations $ 17,832 $ 14,159 $ 19,064 $ 20,171 Specific (allocations) reversals of prior allocations (1,916) (1,501) (1,300) (2,100) Fair value $ 15,916 $ 12,658 $ 17,764 $ 18,071 Non-Financial Assets and Non-Financial Liabilities. We do not have any non-financial assets or non-financial liabilities measured at fair value on a recurring basis. From time to time, non-financial assets measured at fair value on a non-recurring basis may include certain foreclosed assets which, upon initial recognition, were remeasured and reported at fair value through a charge-off to the allowance for loan losses and certain foreclosed assets which, subsequent to their initial recognition, were remeasured at fair value through a write-down included in other non-interest expense. There were no such fair value measurements during the reported periods. Financial Instruments Reported at Amortized Cost. The estimated fair values of financial instruments that are reported at amortized cost in our consolidated balance sheets, segregated by the level of the valuation inputs within the fair value hierarchy utilized to measure fair value, were as follows: June 30, 2024 December 31, 2023 Carrying Estimated Carrying Estimated Financial assets: Level 2 inputs: Cash and cash equivalents $ 7,144,784 $ 7,144,784 $ 8,687,276 $ 8,687,276 Securities held to maturity 3,586,116 3,416,937 3,619,428 3,532,044 Accrued interest receivable 243,951 243,951 251,385 251,385 Level 3 inputs: Loans, net 19,739,449 19,241,857 18,578,255 18,117,369 Financial liabilities: Level 2 inputs: Deposits 40,318,140 40,303,423 41,920,568 41,903,580 Federal funds purchased 35,925 35,925 14,200 14,200 Repurchase agreements 3,762,942 3,762,942 4,127,188 4,127,188 Junior subordinated deferrable interest debentures 123,155 123,712 123,127 123,712 Subordinated notes 99,569 96,645 99,491 96,071 Accrued interest payable 66,812 66,812 61,222 61,222 Under ASC Topic 825, entities may choose to measure eligible financial instruments at fair value at specified election dates. The fair value measurement option (i) may be applied instrument by instrument, with certain exceptions, (ii) is generally irrevocable and (iii) is applied only to entire instruments and not to portions of instruments. Unrealized gains and losses on items for which the fair value measurement option has been elected must be reported in earnings at each subsequent reporting date. During the reported periods, we had no financial instruments measured at fair value under the fair value measurement option.

Accounting Standards Updates

Accounting Standards Updates	6 Months Ended
Accounting Standards Updates	Jun. 30, 2024
Accounting Changes and Error Corrections [Abstract]
Accounting Standards Updates	Accounting Standards Updates Information about certain recently issued accounting standards updates is presented below. Also refer to Note 19 - Accounting Standards Updates in our 2023 Form 10-K for additional information related to previously issued accounting standards updates. ASU 2022-03, “Fair Value Measurement (Topic 820): Fair Value Measurement of Equity Securities Subject to Contractual Sale Restrictions.” ASU 2022-03 clarifies that a contractual restriction on the sale of an equity security is not considered part of the unit of account of the equity security and, therefore, is not considered in measuring fair value. ASU 2022-03 also clarifies that an entity cannot, as a separate unit of account, recognize and measure a contractual sale restriction and requires certain new disclosures for equity securities subject to contractual sale restrictions. ASU 2022-03 became effective for us on January 1, 2024 and did not have a significant effect on our financial statements. ASU 2023-01, “Leases (Topic 842): Common Control Arrangements.” ASU 2023-01 requires entities to amortize leasehold improvements associated with common control leases over the useful life to the common control group. ASU 2023-01 also provides certain practical expedients applicable to private companies and not-for-profit organizations. ASU 2023-01 became effective for us on January 1, 2024 and did not have a significant effect on our financial statements. ASU No. 2023-02, “Investments - Equity Method and Joint Ventures (Topic 323): Accounting for Investments in Tax Credit Structures Using the Proportional Amortization Method.” ASU 2023-02 is intended to improve the accounting and disclosures for investments in tax credit structures. ASU 2023-02 allows entities to elect to account for qualifying tax equity investments using the proportional amortization method, regardless of the program giving rise to the related income tax credits. Previously, this method was only available for qualifying tax equity investments in low-income housing tax credit structures. ASU 2023-02 became effective for us on January 1, 2024 and did not have a significant effect on our financial statements.

Pay vs Performance Disclosure

Pay vs Performance Disclosure - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
Pay vs Performance Disclosure - USD ($) $ in Thousands	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Pay vs Performance Disclosure
Net income	$ 145,499	$ 162,118	$ 281,189	$ 339,771

Insider Trading Arrangements

Insider Trading Arrangements	6 Months Ended
Insider Trading Arrangements	Jun. 30, 2024
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

Significant Accounting Polici_2

Significant Accounting Policies (Policies)	6 Months Ended
Significant Accounting Policies (Policies)	Jun. 30, 2024
Accounting Policies [Abstract]
Nature of Operations	Nature of Operations. Cullen/Frost Bankers, Inc. (“Cullen/Frost”) is a financial holding company and a bank holding company headquartered in San Antonio, Texas that provides, through its subsidiaries, a broad array of products and services throughout numerous Texas markets. The terms “Cullen/Frost,” “the Corporation,” “we,” “us” and “our” mean Cullen/Frost Bankers, Inc., and its subsidiaries, when appropriate. In addition to general commercial and consumer banking, other products and services offered include trust and investment management, insurance, brokerage, mutual funds, leasing, treasury management, capital markets advisory and item processing.
Basis of Presentation	Basis of Presentation. The consolidated financial statements in this Quarterly Report on Form 10-Q include the accounts of Cullen/Frost and all other entities in which Cullen/Frost has a controlling financial interest. All significant intercompany balances and transactions have been eliminated in consolidation. The accounting and financial reporting policies we follow conform, in all material respects, to accounting principles generally accepted in the United States and to general practices within the financial services industry. The consolidated financial statements in this Quarterly Report on Form 10-Q have not been audited by an independent registered public accounting firm, but in the opinion of management, reflect all adjustments necessary for a fair presentation of our financial position and results of operations. All such adjustments were of a normal and recurring nature. The consolidated financial statements have been prepared in accordance with accounting principles generally accepted in the United States for interim financial information and with the instructions to Form 10-Q adopted by the Securities and Exchange Commission (“SEC”). Accordingly, the financial statements do not include all of the information and footnotes required by accounting principles generally accepted in the United States for complete financial statements and should be read in conjunction with our consolidated financial statements, and notes thereto, for the year ended December 31, 2023, included in our Annual Report on Form 10-K filed with the SEC on February 6, 2024 (the “ 2023 Form 10-K ”). Operating results for the interim periods disclosed herein are not necessarily indicative of the results that may be expected for a full year or any future period.
Use of Estimates	Use of Estimates . The preparation of financial statements in conformity with accounting principles generally accepted in the United States 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 financial statements. Actual results could differ from those estimates. The allowance for loan losses and the fair values of financial instruments and the status of contingencies are particularly subject to change.
Reclassification, Policy [Policy Text Block]	Certain items in prior financial statements have been reclassified to conform to the current presentation.

Loans Loans - Allowance For Cre

Loans Loans - Allowance For Credit Losses (Policies)	6 Months Ended
Loans Loans - Allowance For Credit Losses (Policies)	Jun. 30, 2024
Accounting Policies [Abstract]
Financing Receivable, Allowance for Credit Losses, Policy for Uncollectible Amounts	Allowance For Credit Losses - Loans. The allowance for credit losses on loans is a contra-asset valuation account, calculated in accordance with ASC 326, that is deducted from the amortized cost basis of loans to present the net amount expected to be collected. The amount of the allowance represents management's best estimate of current expected credit losses on loans considering available information, from internal and external sources, relevant to assessing collectibility over the loans' contractual terms, adjusted for expected prepayments when appropriate. Credit loss expense related to loans reflects the totality of actions taken on all loans for a particular period including any necessary increases or decreases in the allowance related to changes in credit loss expectations associated with specific loans or pools of loans. Portions of the allowance may be allocated for specific credits; however, the entire allowance is available for any credit that, in management’s judgment, should be charged off. While management utilizes its best judgment and information available, the ultimate appropriateness of the allowance is dependent upon a variety of factors beyond our control, including the performance of our loan portfolio, the economy, changes in interest rates and the view of the regulatory authorities toward loan classifications. Our allowance methodology is more fully described in our 2023 Form 10-K. During the first quarter of 2024, we updated our non-owner-occupied commercial real estate loan models as well as our consumer and other loan models. Our prior non-owner-occupied commercial real estate loan models were legacy models developed for stress-testing purposes by a third-party using external market data. The updated non-owner-occupied commercial real estate loan models are now based on internal historical loan data and risk grade information and the modeling processes are now consistent with those used with our other commercial loan models. Our prior consumer and other loan models relied upon certain components that did not use loan level attributes and were less sensitive to macroeconomic variables. The updated consumer and other loan models are now based on internal historical loan data and utilize more loan-level attributes and the modeling processes are now consistent with those used with our consumer real estate loan models. The overall approximate impact of the model updates during the first quarter was a $7.2 million increase ($6.2 million related to non-owner-occupied commercial real estate loans and $923 thousand related to consumer and other loans) in modeled expected credit losses on loans; however, the impact of this increase was largely offset by reductions in qualitative adjustments as some of the risks to which those qualitative adjustments related are now considered and incorporated in the updated models.

Significant Accounting Polici_3

Significant Accounting Policies (Tables)	6 Months Ended
Significant Accounting Policies (Tables)	Jun. 30, 2024
Accounting Policies [Abstract]
Additional Cash Flow Information	Additional cash flow information was as follows: Six Months Ended 2024 2023 Cash paid for interest $ 389,432 $ 270,358 Cash paid for income taxes 62,000 66,500 Significant non-cash transactions: Unsettled securities transactions 29,011 10,988 Right-of-use lease assets obtained in exchange for lessee operating lease liabilities 9,218 8,914

Securities (Tables)

Securities (Tables)	6 Months Ended
Securities (Tables)	Jun. 30, 2024
Investments, Debt and Equity Securities [Abstract]
Debt Securities, Held-to-maturity [Table Text Block]	A summary of the amortized cost, fair value and allowance for credit losses related to securities held to maturity as of June 30, 2024 and December 31, 2023 is presented below. Amortized Gross Gross Estimated Allowance Net June 30, 2024 Residential mortgage-backed securities $ 1,225,779 $ — $ 74,853 $ 1,150,926 $ — $ 1,225,779 States and political subdivisions 2,359,147 17,319 111,929 2,264,537 (310) 2,358,837 Other 1,500 — 26 1,474 — 1,500 Total $ 3,586,426 $ 17,319 $ 186,808 $ 3,416,937 $ (310) $ 3,586,116 December 31, 2023 Residential mortgage-backed securities $ 1,250,431 $ 76 $ 54,175 $ 1,196,332 $ — $ 1,250,431 States and political subdivisions 2,367,807 42,990 76,540 2,334,257 (310) 2,367,497 Other 1,500 — 45 1,455 — 1,500 Total $ 3,619,738 $ 43,066 $ 130,760 $ 3,532,044 $ (310) $ 3,619,428
Moody's and Standard & Poor's Bond Ratings [Table Text Block]	The following table summarizes Moody's and/or Standard & Poor's bond ratings for our portfolio of held-to-maturity securities issued by States and political subdivisions and other securities as of June 30, 2024 and December 31, 2023: States and Political Subdivisions Not Guaranteed or Pre-Refunded Guaranteed by the Texas PSF Guaranteed by Third Party Pre-Refunded Total Other June 30, 2024 Aaa/AAA $ 301,518 $ 1,538,227 $ 13,645 $ 1,090 $ 1,854,480 $ — Aa/AA 498,557 — 6,110 — 504,667 — Not rated — — — — — 1,500 Total $ 800,075 $ 1,538,227 $ 19,755 $ 1,090 $ 2,359,147 $ 1,500 December 31, 2023 Aaa/AAA $ 301,721 $ 1,541,913 $ 13,651 $ 1,401 $ 1,858,686 $ — Aa/AA 503,016 — 6,105 — 509,121 — Not rated — — — — — 1,500 Total $ 804,737 $ 1,541,913 $ 19,756 $ 1,401 $ 2,367,807 $ 1,500
Debt Securities, Held-to-maturity, Allowance for Credit Loss [Table Text Block]	The following table details activity in the allowance for credit losses on held-to-maturity securities during the three and six months ended June 30, 2024 and 2023. Three Months Ended Six Months Ended 2024 2023 2024 2023 Beginning balance $ 310 $ 262 $ 310 $ 158 Credit loss expense (benefit) — 5 — 109 Ending balance $ 310 $ 267 $ 310 $ 267
Amortized Cost, Estimated Fair Value and Allowance for Credit Losses of Securities Available for Sale	A summary of the amortized cost, fair value and allowance for credit losses related to securities available for sale as of June 30, 2024 and December 31, 2023 is presented below. Amortized Gross Gross Allowance Estimated June 30, 2024 U.S. Treasury $ 4,184,938 $ — $ 302,607 $ — $ 3,882,331 Residential mortgage-backed securities 7,567,795 2,840 1,033,208 — 6,537,427 States and political subdivisions 5,030,087 2,316 297,494 — 4,734,909 Other 42,971 — — — 42,971 Total $ 16,825,791 $ 5,156 $ 1,633,309 $ — $ 15,197,638 December 31, 2023 U.S. Treasury $ 5,212,894 $ — $ 285,305 $ — $ 4,927,589 Residential mortgage-backed securities 7,463,954 9,066 876,338 — 6,596,682 States and political subdivisions 5,245,721 5,762 240,152 — 5,011,331 Other 42,769 — — — 42,769 Total $ 17,965,338 $ 14,828 $ 1,401,795 $ — $ 16,578,371
Securities, with Unrealized Losses Segregated by Length of Impairment	The table below summarizes, as of June 30, 2024, securities available for sale in an unrealized loss position for which an allowance for credit losses has not been recorded, aggregated by type of security and length of time in a continuous unrealized loss position. Less than 12 Months More than 12 Months Total Estimated Unrealized Estimated Unrealized Estimated Unrealized U.S. Treasury $ — $ — $ 3,882,331 $ 302,607 $ 3,882,331 $ 302,607 Residential mortgage-backed securities 508,001 5,469 5,561,705 1,027,739 6,069,706 1,033,208 States and political subdivisions 683,217 7,567 3,875,534 289,927 4,558,751 297,494 Total $ 1,191,218 $ 13,036 $ 13,319,570 $ 1,620,273 $ 14,510,788 $ 1,633,309
Amortized Cost and Estimated Fair Value of Securities, Excluding Trading Securities, Presented by Contractual Maturity	The following table summarizes the maturity distribution schedule of securities held to maturity and securities available for sale as of June 30, 2024. Mortgage-backed securities are included in maturity categories based on their stated maturity date. Expected maturities may differ from contractual maturities because issuers may have the right to call or prepay obligations. Other securities classified as available for sale include stock in the Federal Reserve Bank and the Federal Home Loan Bank, which have no maturity date. These securities have been included in the total column only. Within 1 Year 1 - 5 Years 5 - 10 Years After 10 Years Total Held To Maturity Amortized Cost Residential mortgage-backed securities $ — $ 43,600 $ 467,780 $ 714,399 $ 1,225,779 States and political subdivisions 9,095 4,273 51,899 2,293,880 2,359,147 Other 1,500 — — — 1,500 Total $ 10,595 $ 47,873 $ 519,679 $ 3,008,279 $ 3,586,426 Estimated Fair Value Residential mortgage-backed securities $ — $ 38,538 $ 416,882 $ 695,506 $ 1,150,926 States and political subdivisions 9,068 4,254 49,314 2,201,901 2,264,537 Other 1,474 — — — 1,474 Total $ 10,542 $ 42,792 $ 466,196 $ 2,897,407 $ 3,416,937 Available For Sale Amortized Cost U. S. Treasury $ 1,173,271 $ 2,621,114 $ 197,956 $ 192,597 $ 4,184,938 Residential mortgage-backed securities 702 1,118 13,084 7,552,891 7,567,795 States and political subdivisions 176,288 248,998 830,750 3,774,051 5,030,087 Other — — — — 42,971 Total $ 1,350,261 $ 2,871,230 $ 1,041,790 $ 11,519,539 $ 16,825,791 Estimated Fair Value U. S. Treasury $ 1,152,647 $ 2,428,473 $ 163,742 $ 137,469 $ 3,882,331 Residential mortgage-backed securities 696 1,121 13,116 6,522,494 6,537,427 States and political subdivisions 175,880 244,313 787,791 3,526,925 4,734,909 Other — — — — 42,971 Total $ 1,329,223 $ 2,673,907 $ 964,649 $ 10,186,888 $ 15,197,638
Schedule of Realized Gain (Loss)	Sales of available for sale securities were as follows: Three Months Ended Six Months Ended 2024 2023 2024 2023 Proceeds from sales $ — $ 659,082 $ — $ 1,543,355 Gross realized gains — 561 — 5,417 Gross realized losses — (528) — (5,363) Tax (expense) benefit of securities gains/losses — (7) — (11)
Investment Income	Premium amortization and discount accretion included in interest income on securities was as follows: Three Months Ended Six Months Ended 2024 2023 2024 2023 Premium amortization $ (16,570) $ (21,242) $ (34,523) $ (47,167) Discount accretion 5,032 4,843 9,737 10,248 Net (premium amortization) discount accretion $ (11,538) $ (16,399) $ (24,786) $ (36,919)
Trading Account Securities, at Estimated Fair Value	Trading account securities, at estimated fair value, were as follows: June 30, December 31, U.S. Treasury $ 31,400 $ 30,265 States and political subdivisions 786 1,452 Total $ 32,186 $ 31,717
Net Gains and Losses on Trading Account Securities	Net gains and losses on trading account securities were as follows: Three Months Ended Six Months Ended 2024 2023 2024 2023 Net gain on sales transactions $ 1,223 $ 903 $ 2,382 $ 1,871 Net mark-to-market gains (losses) (82) (10) (101) (27) Net gain (loss) on trading account securities $ 1,141 $ 893 $ 2,281 $ 1,844

Loans (Tables)

Loans (Tables)	6 Months Ended
Loans (Tables)	Jun. 30, 2024
Receivables [Abstract]
Loans	Loans were as follows: June 30, December 31, Commercial and industrial $ 6,210,179 $ 5,967,182 Energy: Production 858,990 681,568 Service 209,658 194,126 Other 28,009 61,043 Total energy 1,096,657 936,737 Commercial real estate: Commercial mortgages 6,955,118 6,746,709 Construction 1,997,545 1,680,724 Land 542,549 555,211 Total commercial real estate 9,495,212 8,982,644 Consumer real estate: Home equity lines of credit 832,307 792,876 Home equity loans 790,727 694,966 Home improvement loans 813,799 765,887 Other 303,895 206,997 Total consumer real estate 2,740,728 2,460,726 Total real estate 12,235,940 11,443,370 Consumer and other 452,980 476,962 Total loans $ 19,995,756 $ 18,824,251
Non-Accrual Loans, Segregated by Class of Loans	Non-accrual loans, segregated by class of loans, were as follows: June 30, 2024 December 31, 2023 Total Non-Accrual Non-Accrual with No Credit Loss Allowance Total Non-Accrual Non-Accrual with No Credit Loss Allowance Commercial and industrial $ 26,329 $ 8,044 $ 19,545 $ 5,391 Energy 9,147 6,045 11,500 7,398 Commercial real estate: Buildings, land, and other 33,092 14,099 22,420 4,983 Construction — — — — Consumer real estate 6,419 4,188 7,442 5,160 Consumer and other — — — — Total $ 74,987 $ 32,376 $ 60,907 $ 22,932
Financing Receivable, Non-Accrual Loans, Segregated by Class of Loan and Year of Origination	The following table presents non-accrual loans as of June 30, 2024 by class and year of origination. 2024 2023 2022 2021 2020 Prior Revolving Loans Revolving Loans Converted to Term Total Commercial and industrial $ 746 $ 3,764 $ 1,159 $ 3,066 $ 514 $ 2,197 $ 2,149 $ 12,734 $ 26,329 Energy 4,522 — — — 56 1,321 3,102 146 9,147 Commercial real estate: Buildings, land, and other 328 20,115 3,027 5,374 — 1,411 2,837 — 33,092 Construction — — — — — — — — — Consumer real estate — — — — — 6,419 — — 6,419 Consumer and other — — — — — — — — — Total $ 5,596 $ 23,879 $ 4,186 $ 8,440 $ 570 $ 11,348 $ 8,088 $ 12,880 $ 74,987
Age Analysis of Past Due Loans, Segregated by Class of Loans	An age analysis of past due loans (including both accruing and non-accruing loans), segregated by class of loans, as of June 30, 2024 was as follows: Loans Loans Total Current Total Accruing Commercial and industrial $ 38,806 $ 24,640 $ 63,446 $ 6,146,733 $ 6,210,179 $ 5,568 Energy — 4,625 4,625 1,092,032 1,096,657 — Commercial real estate: Buildings, land, and other 20,272 14,620 34,892 7,462,775 7,497,667 1,687 Construction 24,535 — 24,535 1,973,010 1,997,545 — Consumer real estate 17,659 8,819 26,478 2,714,250 2,740,728 4,707 Consumer and other 5,734 577 6,311 446,669 452,980 577 Total $ 107,006 $ 53,281 $ 160,287 $ 19,835,469 $ 19,995,756 $ 12,539
Modification to Borrowers Experiencing Financial Difficulty	The period-end balance of loan modifications, segregated by type of modification, to borrowers experiencing financial difficulty during the six months ended June 30, 2024 and 2023 are set forth in the table below, regardless of whether such modifications resulted in a new loan. There were no commitments to lend additional funds to these borrowers at June 30, 2024. Combination: Payment Delay and Term Extension Percent of June 30, 2024 Commercial and industrial $ 27,731 0.4 % June 30, 2023 Commercial and industrial $ 16,020 0.3 % Commercial real estate: Buildings, land, and other 20,466 0.3 $ 36,486 0.2
Financing Receivables, Modified Loans Past Due in Excess of 90 Days or on Non-Accrual Status, Charge-offs and Proceeds From Sales at Period-End	Information as of June 30, 2024 and June 30, 2023 related to loans modified (by type of modification) in the preceding twelve months, respectively, whereby the borrower was experiencing financial difficulty at the time of modification is set forth in the following table. June 30, 2024 June 30, 2023 Combination: Payment Delay and Term Extension Combination: Payment Delay and Term Extension Past due in excess of 90 days or on non-accrual status at period-end: Commercial and industrial $ — $ 16,020 Commercial real estate: Buildings, land, and other — 20,466 $ — $ 36,486
Weighted Average Risk Grades for All Commercial Loans by Class and Year of Origination	The following table presents weighted-average risk grades for all commercial loans, by class and year of origination/renewal, as of June 30, 2024. 2024 2023 2022 2021 2020 Prior Revolving Loans Revolving Loans Converted to Term Total W/A Risk Grade Commercial and industrial Risk grades 1-8 $ 1,095,611 $ 672,837 $ 566,640 $ 340,735 $ 310,052 $ 316,544 $ 2,208,140 $ 45,210 $ 5,555,769 6.40 Risk grade 9 16,980 9,095 65,217 10,609 5,220 9,906 92,920 4,372 214,319 9.00 Risk grade 10 1,114 434 14,799 687 218 12,285 43,049 3,775 76,361 10.00 Risk grade 11 93,737 32,948 20,080 36,358 5,840 2,046 140,163 6,229 337,401 11.00 Risk grade 12 746 2,474 1,015 3,062 503 2,197 646 9,658 20,301 12.00 Risk grade 13 — 1,290 144 4 11 — 1,503 3,076 6,028 13.00 $ 1,208,188 $ 719,078 $ 667,895 $ 391,455 $ 321,844 $ 342,978 $ 2,486,421 $ 72,320 $ 6,210,179 6.81 W/A risk grade 7.27 6.93 7.29 7.32 5.72 6.07 6.53 8.52 6.81 Energy Risk grades 1-8 $ 300,048 $ 34,672 $ 49,350 $ 49,328 $ 3,927 $ 5,041 $ 597,664 $ 6,669 $ 1,046,699 5.63 Risk grade 9 — 1,342 3,634 755 — 414 23,888 652 30,685 9.00 Risk grade 10 — — — 21 — 694 4,100 — 4,815 10.00 Risk grade 11 — — 2,075 — 72 2,945 — 219 5,311 11.00 Risk grade 12 4,522 — — — 56 1,321 402 146 6,447 12.00 Risk grade 13 — — — — — — 2,700 — 2,700 13.00 $ 304,570 $ 36,014 $ 55,059 $ 50,104 $ 4,055 $ 10,415 $ 628,754 $ 7,686 $ 1,096,657 5.83 W/A risk grade 6.11 6.80 7.00 5.88 6.56 9.00 5.44 7.32 5.83 Commercial real estate: Buildings, land, other Risk grades 1-8 $ 675,926 $ 1,431,165 $ 1,485,228 $ 1,150,261 $ 706,667 $ 1,153,397 $ 119,008 $ 96,456 $ 6,818,108 7.05 Risk grade 9 4,176 5,529 128,935 35,986 7,420 38,849 43,689 61,767 326,351 9.00 Risk grade 10 5,047 24,596 53,834 18,244 15,912 11,330 1,723 — 130,686 10.00 Risk grade 11 5,177 8,854 37,368 24,337 21,975 91,719 — — 189,430 11.00 Risk grade 12 328 15,965 3,027 5,152 — 1,411 2,593 — 28,476 12.00 Risk grade 13 — 4,150 — 222 — — 244 — 4,616 13.00 $ 690,654 $ 1,490,259 $ 1,708,392 $ 1,234,202 $ 751,974 $ 1,296,706 $ 167,257 $ 158,223 $ 7,497,667 7.31 W/A risk grade 7.21 7.31 7.39 7.34 7.17 7.18 8.02 7.53 7.31 Construction Risk grades 1-8 $ 247,162 $ 475,920 $ 575,573 $ 119,299 $ 28,003 $ 1,296 $ 149,756 $ 165 $ 1,597,174 7.32 Risk grade 9 90,634 5,282 26,585 118,546 — — 5,650 — 246,697 9.00 Risk grade 10 13,601 34,842 13,513 49,088 — — — — 111,044 10.00 Risk grade 11 — — 31,500 11,130 — — — — 42,630 11.00 Risk grade 12 — — — — — — — — — 12.00 Risk grade 13 — — — — — — — — — 13.00 $ 351,397 $ 516,044 $ 647,171 $ 298,063 $ 28,003 $ 1,296 $ 155,406 $ 165 $ 1,997,545 7.75 W/A risk grade 7.68 7.54 7.83 8.70 2.53 6.81 7.46 6.98 7.75 Total commercial real estate $ 1,042,051 $ 2,006,303 $ 2,355,563 $ 1,532,265 $ 779,977 $ 1,298,002 $ 322,663 $ 158,388 $ 9,495,212 7.40 W/A risk grade 7.36 7.37 7.51 7.61 7.00 7.18 7.75 7.53 7.40
Weighted Average Risk Grades for All Commercial Loans by Class	The following tables present weighted average risk grades for all commercial loans by class as of December 31, 2023. Refer to our 2023 Form 10-K for details of these loans by year of origination/renewal. Commercial and Industrial Energy Commercial Real Estate - Buildings, Land and Other Commercial Real Estate - Construction Total Commercial Real Estate W/A Risk Grade Loans W/A Risk Grade Loans W/A Risk Grade Loans W/A Risk Grade Loans W/A Risk Grade Loans Risk grades 1-8 6.32 $ 5,507,878 5.73 $ 871,221 7.03 $ 6,895,358 7.27 $ 1,526,086 7.07 $ 8,421,444 Risk grade 9 9.00 205,244 9.00 27,643 9.00 173,470 9.00 127,102 9.00 300,572 Risk grade 10 10.00 109,254 10.00 818 10.00 96,601 10.00 17,035 10.00 113,636 Risk grade 11 11.00 125,261 11.00 25,555 11.00 114,071 11.00 10,501 11.00 124,572 Risk grade 12 12.00 17,102 12.00 8,800 12.00 19,770 12.00 — 12.00 19,770 Risk grade 13 13.00 2,443 13.00 2,700 13.00 2,650 13.00 — 13.00 2,650 Total 6.60 $ 5,967,182 6.05 $ 936,737 7.20 $ 7,301,920 7.45 $ 1,680,724 7.24 $ 8,982,644
Age analysis of Past Due Consumer Loans by Class and Year of Origination	Information about the payment status of consumer loans, segregated by portfolio segment and year of origination, as of June 30, 2024 was as follows: 2024 2023 2022 2021 2020 Prior Revolving Loans Revolving Loans Converted to Term Total Consumer real estate: Past due 30-89 days $ 158 $ 450 $ 1,396 $ 2,151 $ 1,005 $ 4,813 $ 7,284 $ 402 $ 17,659 Past due 90 or more days — 565 772 309 60 772 2,624 3,717 8,819 Total past due 158 1,015 2,168 2,460 1,065 5,585 9,908 4,119 26,478 Current loans 314,290 575,925 410,016 263,679 158,204 173,773 810,696 7,667 2,714,250 Total $ 314,448 $ 576,940 $ 412,184 $ 266,139 $ 159,269 $ 179,358 $ 820,604 $ 11,786 $ 2,740,728 Consumer and other: Past due 30-89 days $ 2,429 $ 174 $ 231 $ 122 $ 118 $ 64 $ 2,559 $ 37 $ 5,734 Past due 90 or more days 217 — 16 1 — — 162 181 577 Total past due 2,646 174 247 123 118 64 2,721 218 6,311 Current loans 35,410 40,943 19,574 3,921 2,691 1,457 319,622 23,051 446,669 Total $ 38,056 $ 41,117 $ 19,821 $ 4,044 $ 2,809 $ 1,521 $ 322,343 $ 23,269 $ 452,980
Revolving Loans Converted to Term [Table Text Block]	Period-end balances for revolving loans that converted to term during the three and six months ended June 30, 2024 and 2023 were as follows: Three Months Ended June 30, Six Months Ended June 30, 2024 2023 2024 2023 Commercial and industrial $ 10,557 $ 3,835 $ 24,813 $ 14,606 Energy 604 — 646 2,567 Commercial real estate: Buildings, land and other 65,642 5,944 66,238 5,944 Construction 165 — 165 — Consumer real estate 971 1,064 1,703 1,743 Consumer and other 3,541 1,669 6,094 3,671 Total $ 81,480 $ 12,512 $ 99,659 $ 28,531
Financing Receivable, Allowance for Credit Loss By Loan Class Calculated in Accordance With CECL Methodology	The following table presents details of the allowance for credit losses on loans segregated by loan portfolio segment as of June 30, 2024 and December 31, 2023. June 30, 2024 Commercial Energy Commercial Consumer Consumer Total Modeled expected credit losses $ 56,937 $ 3,841 $ 20,961 $ 14,508 $ 7,415 $ 103,662 Q-Factor and other qualitative adjustments 15,589 4,944 114,443 508 3,126 138,610 Specific allocations 6,028 2,700 4,616 691 — 14,035 Total $ 78,554 $ 11,485 $ 140,020 $ 15,707 $ 10,541 $ 256,307 December 31, 2023 Modeled expected credit losses $ 50,959 $ 7,838 $ 15,443 $ 12,364 $ 5,969 $ 92,573 Q-Factor and other qualitative adjustments 20,612 7,276 112,505 433 4,071 144,897 Specific allocations 2,435 2,700 2,650 741 — 8,526 Total $ 74,006 $ 17,814 $ 130,598 $ 13,538 $ 10,040 $ 245,996
Activity in Allowance for Loan Losses by Portfolio Segment	The following table details activity in the allowance for credit losses on loans by portfolio segment for the three and six months ended June 30, 2024 and 2023. Allocation of a portion of the allowance to one category of loans does not preclude its availability to absorb losses in other categories. Commercial Energy Commercial Consumer Consumer Total Three months ended: June 30, 2024 Beginning balance $ 75,596 $ 14,218 $ 138,224 $ 13,857 $ 8,402 $ 250,297 Credit loss expense (benefit) 6,936 (3,038) 1,903 2,175 7,760 15,736 Charge-offs (4,282) (79) (122) (408) (8,360) (13,251) Recoveries 304 384 15 83 2,739 3,525 Net (charge-offs) recoveries (3,978) 305 (107) (325) (5,621) (9,726) Ending balance $ 78,554 $ 11,485 $ 140,020 $ 15,707 $ 10,541 $ 256,307 June 30, 2023 Beginning balance 78,465 19,191 115,693 9,708 8,457 $ 231,514 Credit loss expense (benefit) 2,404 (4,433) 5,133 3,822 5,007 11,933 Charge-offs (7,136) (518) — (1,080) (7,016) (15,750) Recoveries 1,433 689 100 585 3,115 5,922 Net (charge-offs) recoveries (5,703) 171 100 (495) (3,901) (9,828) Ending balance $ 75,166 $ 14,929 $ 120,926 $ 13,035 $ 9,563 $ 233,619 Six months ended: June 30, 2024 Beginning balance $ 74,006 $ 17,814 $ 130,598 $ 13,538 $ 10,040 $ 245,996 Credit loss expense (benefit) 8,928 (6,814) 9,513 3,981 11,778 27,386 Charge-offs (6,426) (79) (122) (2,077) (16,617) (25,321) Recoveries 2,046 564 31 265 5,340 8,246 Net (charge-offs) recoveries (4,380) 485 (91) (1,812) (11,277) (17,075) Ending balance $ 78,554 $ 11,485 $ 140,020 $ 15,707 $ 10,541 $ 256,307 June 30, 2023 Beginning balance 104,237 18,062 90,301 8,004 7,017 $ 227,621 Credit loss expense (benefit) (18,280) (3,467) 30,494 5,105 10,756 24,608 Charge-offs (13,316) (518) — (1,330) (13,958) (29,122) Recoveries 2,525 852 131 1,256 5,748 10,512 Net (charge-offs) recoveries (10,791) 334 131 (74) (8,210) (18,610) Ending balance $ 75,166 $ 14,929 $ 120,926 $ 13,035 $ 9,563 $ 233,619
Financing Receivable, Gross Charge-Offs By Year of Origination	The following table presents year-to-date gross charge-offs by year of origination as of June 30, 2024. 2024 2023 2022 2021 2020 Prior Revolving Loans Revolving Loans Converted to Term Total Commercial and industrial $ — $ 471 $ 676 $ 467 $ 401 $ 625 $ 2,902 $ 884 $ 6,426 Energy — 79 — — — — — — 79 Commercial real estate: Buildings, land and other — — 122 — — — — — 122 Construction — — — — — — — — — Consumer real estate — — 148 253 — 384 1,225 67 2,077 Consumer and other 9,369 5,713 131 4 4 51 1,332 13 16,617 Total $ 9,369 $ 6,263 $ 1,077 $ 724 $ 405 $ 1,060 $ 5,459 $ 964 $ 25,321
Investment in Loans Related to Allowance for Loan Losses by Portfolio Segment Disaggregated Based on Impairment Methodology	The following table presents loans that were evaluated for expected credit losses on an individual basis and the related specific allocations, by loan portfolio segment, as of June 30, 2024 and December 31, 2023. June 30, 2024 December 31, 2023 Loan Specific Allocations Loan Specific Allocations Commercial and industrial $ 25,508 $ 6,028 $ 18,670 $ 2,435 Energy 9,001 2,700 11,353 2,700 Commercial real estate: Buildings, land and other 32,316 4,616 21,373 2,650 Construction — — — — Consumer real estate 5,807 691 7,235 741 Consumer and other — — — — Total $ 72,632 $ 14,035 $ 58,631 $ 8,526

Deposits (Tables)

Deposits (Tables)	6 Months Ended
Deposits (Tables)	Jun. 30, 2024
Disclosure Text Block [Abstract]
Deposit Liabilities, Type	Deposits were as follows: June 30, December 31, Non-interest-bearing demand deposits $ 13,484,977 $ 14,926,094 Interest-bearing deposits: Savings and interest checking 9,629,146 10,512,637 Money market accounts 10,899,993 10,997,279 Time accounts 6,304,024 5,484,558 Total interest-bearing deposits 26,833,163 26,994,474 Total deposits $ 40,318,140 $ 41,920,568
Additional Information About Corporation's Deposits	The table below presents additional information about our deposits. Public funds in excess of deposit insurance limits are included in the totals for deposits not covered by insurance; however, such deposits are generally fully collateralized by securities. June 30, December 31, Deposits from foreign sources (primarily Mexico) $ 1,114,319 $ 1,061,701 Non-interest-bearing public funds deposits 451,472 675,016 Interest-bearing public funds deposits 636,415 630,455 Total deposits not covered by deposit insurance 20,774,932 22,393,786 Time deposits not covered by deposit insurance 2,721,625 2,339,716

Commitments and Contingencies (

Commitments and Contingencies (Tables)	6 Months Ended
Commitments and Contingencies (Tables)	Jun. 30, 2024
Commitments and Contingencies Disclosure [Abstract]
Financial Instruments with Off-Balance-Sheet Risk	Financial instruments with off-balance-sheet risk were as follows: June 30, December 31, Commitments to extend credit $ 11,908,533 $ 12,195,073 Standby letters of credit 404,673 438,635 Deferred standby letter of credit fees 2,614 2,912
Commitments, Off-Balance-Sheet, Allowance for Credit Losses [Table Text Block]	The following table details activity in the allowance for credit losses on off-balance-sheet credit exposures. Three Months Ended Six Months Ended 2024 2023 2024 2023 Beginning balance $ 53,751 $ 54,918 $ 51,751 $ 58,593 Credit loss expense (benefit) 51 (2,037) 2,051 (5,712) Ending balance $ 53,802 $ 52,881 $ 53,802 $ 52,881
Lease Commitments, Components of Lease Expense [Table Text Block]	We lease certain office facilities and office equipment under operating leases. The components of total lease expense were as follows: Three Months Ended Six Months Ended 2024 2023 2024 2023 Amortization of lease right-of-use assets $ 8,829 $ 8,747 $ 17,619 $ 17,512 Short-term lease expense 394 493 719 902 Non-lease components (including taxes, insurance, common maintenance, etc.) 3,466 3,662 7,015 7,043 Total $ 12,689 $ 12,902 $ 25,353 $ 25,457

Capital and Regulatory Matters

Capital and Regulatory Matters (Tables)	6 Months Ended
Capital and Regulatory Matters (Tables)	Jun. 30, 2024
Banking Regulation, Common Equity Tier 1 Risk-Based Capital [Abstract]
Actual and Required Capital Ratios	The following table presents actual and required capital ratios as of June 30, 2024 and December 31, 2023 for Cullen/Frost and Frost Bank under the Basel III Capital Rules. Capital levels required to be considered well-capitalized are based upon prompt corrective action regulations, as amended to reflect the changes under the Basel III Capital Rules. See the 2023 Form 10-K for a more detailed discussion of the Basel III Capital Rules. Actual Minimum Capital Required Plus Capital Conservation Buffer Required to be Considered Well- Capitalized (1) Capital Ratio Capital Ratio Capital Ratio June 30, 2024 Common Equity Tier 1 to Risk-Weighted Assets Cullen/Frost $ 4,164,990 13.35 % $ 2,183,331 7.00 % N/A N/A Frost Bank 4,228,311 13.56 2,182,110 7.00 $ 2,026,245 6.50 % Tier 1 Capital to Risk-Weighted Assets Cullen/Frost 4,310,442 13.82 2,651,188 8.50 1,871,427 6.00 Frost Bank 4,228,311 13.56 2,649,705 8.50 2,493,840 8.00 Total Capital to Risk-Weighted Assets Cullen/Frost 4,763,514 15.27 3,274,997 10.50 3,119,044 10.00 Frost Bank 4,521,383 14.50 3,273,165 10.50 3,117,300 10.00 Leverage Ratio Cullen/Frost 4,310,442 8.62 1,999,776 4.00 N/A N/A Frost Bank 4,228,311 8.46 1,999,934 4.00 2,499,918 5.00 December 31, 2023 Common Equity Tier 1 to Risk-Weighted Assets Cullen/Frost $ 4,036,945 13.25 % $ 2,132,516 7.00 % N/A N/A Frost Bank 4,057,111 13.33 2,129,784 7.00 $ 1,977,656 6.50 % Tier 1 Capital to Risk-Weighted Assets Cullen/Frost 4,182,397 13.73 2,589,484 8.50 1,827,871 6.00 Frost Bank 4,057,111 13.33 2,586,166 8.50 2,434,038 8.00 Total Capital to Risk-Weighted Assets Cullen/Frost 4,625,760 15.18 3,198,774 10.50 3,046,452 10.00 Frost Bank 4,320,474 14.20 3,194,676 10.50 3,042,548 10.00 Leverage Ratio Cullen/Frost 4,182,397 8.35 2,003,020 4.00 N/A N/A Frost Bank 4,057,111 8.10 2,003,152 4.00 2,503,940 5.00 ____________________ (1) “Well-capitalized” minimum Common Equity Tier 1 to Risk-Weighted Assets and Leverage Ratio are not formally defined under applicable banking regulations for bank holding companies.

Derivative Financial Instrume_2

Derivative Financial Instruments (Tables)	6 Months Ended
Derivative Financial Instruments (Tables)	Jun. 30, 2024
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Schedule of Notional Amounts and Estimated Fair Values of Interest Rate Derivative Contracts Outstanding	The notional amounts and estimated fair values of interest rate derivative contracts are presented in the following table. The fair values of interest rate derivative contracts are estimated utilizing internal valuation methods with observable market data inputs, or as determined by the Chicago Mercantile Exchange (“CME”) for centrally cleared derivative contracts. CME rules legally characterize variation margin payments for centrally cleared derivatives as settlements of the derivatives' exposure rather than collateral. As a result, the variation margin payment and the related derivative instruments are considered a single unit of account for accounting and financial reporting purposes. Variation margin, as determined by the CME, is settled daily. As a result, derivative contracts that clear through the CME have an estimated fair value of zero as of June 30, 2024 and December 31, 2023. June 30, 2024 December 31, 2023 Notional Estimated Notional Estimated Non-hedging interest rate derivatives: Financial institution counterparties: Loan/lease interest rate swaps – assets 1,176,104 $ 70,070 1,040,659 $ 58,486 Loan/lease interest rate swaps – liabilities 553,195 (7,166) 617,266 (20,293) Loan/lease interest rate caps – assets 235,699 10,021 275,000 11,747 Customer counterparties: Loan/lease interest rate swaps – assets 553,195 7,166 617,266 20,482 Loan/lease interest rate swaps – liabilities 1,176,104 (70,069) 1,040,659 (58,485) Loan/lease interest rate caps – liabilities 235,699 (10,019) 275,000 (11,747)
Schedule of Weighted-Average Rates Paid and Received for Interest Rate Swaps Outstanding	The weighted-average rates paid and received for interest rate swaps outstanding at June 30, 2024 were as follows: Weighted-Average Interest Interest Interest rate swaps: Non-hedging interest rate swaps – financial institution counterparties 4.98 % 7.08 % Non-hedging interest rate swaps – customer counterparties 7.08 4.98
Schedule of Notional Amounts and Estimated Fair Values of Commodity Derivative Positions	The notional amounts and estimated fair values of non-hedging commodity swap and option derivative positions outstanding are presented in the following table. We obtain dealer quotations and use internal valuation methods with observable market data inputs to value our commodity derivative positions. June 30, 2024 December 31, 2023 Notional Notional Estimated Notional Estimated Financial institution counterparties: Oil – assets Barrels 4,541 $ 14,580 5,601 $ 37,667 Oil – liabilities Barrels 7,437 (28,552) 4,581 (18,500) Natural gas – assets MMBTUs 21,934 8,831 17,363 11,822 Natural gas – liabilities MMBTUs 10,785 (3,474) 6,462 (2,499) Customer counterparties: Oil – assets Barrels 7,498 29,330 4,618 18,722 Oil – liabilities Barrels 4,480 (14,315) 5,564 (36,877) Natural gas – assets MMBTUs 12,693 3,552 6,462 2,499 Natural gas – liabilities MMBTUs 20,025 (8,478) 17,363 (11,571)
Schedule of Foreign Exchange Contracts, Statement of Financial Position	The notional amounts and fair values of open foreign currency forward and option contracts are presented in the following table. June 30, 2024 December 31, 2023 Notional Notional Estimated Notional Estimated Financial institution counterparties: Forward and option contracts – assets CAD — $ — 250 $ 1 Forward and option contracts – liabilities EUR — — 3,000 (14) Forward and option contracts – liabilities CAD — — 250 (5) Customer counterparties: Forward and option contracts – assets EUR — — 3,000 16 Forward and option contracts – assets CAD — — 250 5 Forward and option contracts – liabilities CAD — — 250 —
Schedule of Amounts Related to Interest Rate Derivatives Designated as Hedges of Fair Value	Amounts included in the consolidated statements of income related to interest rate derivatives designated as hedges of fair value were as follows: Three Months Ended Six Months Ended 2024 2023 2024 2023 Commercial loan/lease interest rate swaps: Amount of gain (loss) included in interest income on loans $ — $ 4 $ — $ 16 Amount of (gain) loss included in other non-interest expense — 4 — 4
Schedule of Amounts Related to Non-Hedging Interest Rate and Commodity Derivatives	Amounts included in the consolidated statements of income related to non-hedge related derivative instruments are presented in the table below. Three Months Ended Six Months Ended 2024 2023 2024 2023 Non-hedging interest rate derivatives: Other non-interest income $ 512 $ 1,002 $ 1,637 $ 1,712 Other non-interest expense 3 1 3 — Non-hedging commodity derivatives: Other non-interest income 946 503 1,325 925 Non-hedging foreign currency derivatives: Other non-interest income — — 11 25

Balance Sheet Offsetting (Table

Balance Sheet Offsetting (Tables)	6 Months Ended	12 Months Ended
Balance Sheet Offsetting (Tables)	Jun. 30, 2024	Dec. 31, 2023
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Financial Instruments Eligible for Offset Consolidated Balance Sheet	Information about financial instruments that are eligible for offset in the consolidated balance sheet as of June 30, 2024 is presented in the following tables. Gross Amount Gross Amount Net Amount June 30, 2024 Financial assets: Derivatives: Interest rate contracts $ 80,091 $ — $ 80,091 Commodity contracts 23,411 — 23,411 Total derivatives 103,502 — 103,502 Resell agreements 84,650 — 84,650 Total $ 188,152 $ — $ 188,152 Financial liabilities: Derivatives: Interest rate contracts $ 7,166 $ — $ 7,166 Commodity contracts 32,026 — 32,026 Total derivatives 39,192 — 39,192 Repurchase agreements 3,762,942 — 3,762,942 Total $ 3,802,134 $ — $ 3,802,134	Information about financial instruments that are eligible for offset in the consolidated balance sheet as of December 31, 2023 is presented in the following tables. Gross Amount Gross Amount Net Amount December 31, 2023 Financial assets: Derivatives: Interest rate contracts $ 70,233 $ — $ 70,233 Commodity contracts 49,489 — 49,489 Foreign currency contracts 1 — 1 Total derivatives 119,723 — 119,723 Resell agreements 84,650 — 84,650 Total $ 204,373 $ — $ 204,373 Financial liabilities: Derivatives: Interest rate contracts $ 20,293 $ — $ 20,293 Commodity contracts 20,999 — 20,999 Foreign currency contracts 19 — 19 Total derivatives 41,311 — 41,311 Repurchase agreements 4,127,188 — 4,127,188 Total $ 4,168,499 $ — $ 4,168,499
Financial Instruments Derivative Assets Liabilities and Resell Agreements Net of Amount Not Offset	Gross Amounts Not Offset Net Amount Financial Collateral Net June 30, 2024 Financial assets: Derivatives: Counterparty H $ 32,594 $ (15,265) $ (16,030) $ 1,299 Counterparty F 16,299 (10,399) (3,889) 2,011 Counterparty B 24,125 (6,362) (16,870) 893 Counterparty E 15,855 (1,913) (13,040) 902 Other counterparties 14,629 (5,253) (8,294) 1,082 Total derivatives 103,502 (39,192) (58,123) 6,187 Resell agreements 84,650 — (84,650) — Total $ 188,152 $ (39,192) $ (142,773) $ 6,187 Financial liabilities: Derivatives: Counterparty H $ 15,265 $ (15,265) $ — $ — Counterparty F 10,399 (10,399) — — Counterparty B 6,362 (6,362) — — Counterparty E 1,913 (1,913) — — Other counterparties 5,253 (5,253) — — Total derivatives 39,192 (39,192) — — Repurchase agreements 3,762,942 — (3,762,942) — Total $ 3,802,134 $ (39,192) $ (3,762,942) $ —	Gross Amounts Not Offset Net Amount Financial Collateral Net December 31, 2023 Financial assets: Derivatives: Counterparty H $ 36,551 $ (8,870) $ (27,170) $ 511 Counterparty F 31,202 (7,444) (22,954) 804 Counterparty B 23,829 (5,151) (18,472) 206 Counterparty E 13,271 (4,548) (8,723) — Other counterparties 14,870 (6,418) (7,520) 932 Total derivatives 119,723 (32,431) (84,839) 2,453 Resell agreements 84,650 — (84,650) — Total $ 204,373 $ (32,431) $ (169,489) $ 2,453 Financial liabilities: Derivatives: Counterparty H $ 8,870 $ (8,870) $ — $ — Counterparty F 7,444 (7,444) — — Counterparty B 5,151 (5,151) — — Counterparty E 4,548 (4,548) — — Other counterparties 15,298 (6,418) (8,580) 300 Total derivatives 41,311 (32,431) (8,580) 300 Repurchase agreements 4,127,188 — (4,127,188) — Total $ 4,168,499 $ (32,431) $ (4,135,768) $ 300
Remaining Contractual Maturity of the Securities Sold Under Agreement [Table Text Block]	The remaining contractual maturity of repurchase agreements in the consolidated balance sheets as of June 30, 2024 and December 31, 2023 is presented in the following tables. Remaining Contractual Maturity of the Agreements Overnight and Continuous Up to 30 Days 30-90 Days Greater than 90 Days Total June 30, 2024 Repurchase agreements: U.S. Treasury $ 1,889,019 $ — $ — $ — $ 1,889,019 Residential mortgage-backed securities 1,873,923 — — — 1,873,923 Total borrowings $ 3,762,942 $ — $ — $ — $ 3,762,942 Gross amount of recognized liabilities for repurchase agreements $ 3,762,942 Amounts related to agreements not included in offsetting disclosures above $ — December 31, 2023 Repurchase agreements: U.S. Treasury $ 3,300,662 $ — $ — $ — $ 3,300,662 Residential mortgage-backed securities 826,526 — — — 826,526 Total borrowings $ 4,127,188 $ — $ — $ — $ 4,127,188 Gross amount of recognized liabilities for repurchase agreements $ 4,127,188 Amounts related to agreements not included in offsetting disclosures above $ —

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	6 Months Ended
Stock-Based Compensation (Tables)	Jun. 30, 2024
Share-Based Payment Arrangement [Abstract]
Disclosure of Share-based Compensation Arrangements by Share-based Payment Award	A combined summary of activity in our active stock plans is presented in the table below. Performance stock units outstanding are presented assuming attainment of the maximum payout rate as set forth by the performance criteria. On April 24, 2024, the shareholders of Cullen/Frost approved the 2024 Equity Incentive Plan (the “2024 Plan”) to replace the 2015 Omnibus Incentive Plan (the “2015 Plan”). Under the 2024 Plan, shareholders approved the issuance, pursuant to the plan, of 2,576,038 shares of our common stock. This amount included 2,350,000 newly authorized shares and the 226,038 shares remaining available for issuance under the superseded 2015 Plan. As of June 30, 2024, there were 2,567,893 shares remaining available for grant for future stock-based compensation awards. Deferred Non-Vested Performance Stock Options Number Weighted- Number Weighted- Number Weighted- Number Weighted- Balance, January 1, 2024 54,164 $ 89.71 566,806 $ 99.77 267,054 $ 89.99 485,941 $ 71.25 Granted 7,997 116.84 2,826 107.95 — — — — Exercised/vested (9,382) 80.99 (458) 65.43 (45,818) 57.89 (66,970) 77.79 Forfeited/expired — — (1,408) 106.18 (22,913) 57.89 — — Balance, June 30, 2024 52,779 95.37 567,766 99.82 198,323 101.12 418,971 70.20
Shares Issued in Connection with Stock Compensation Awards	Shares issued in connection with stock compensation awards along with other related information were as follows: Three Months Ended Six Months Ended 2024 2023 2024 2023 New shares issued from available authorized shares — — — 49,887 Shares issued from available treasury stock 38,452 13,626 122,628 14,126 Proceeds from stock option exercises $ 2,294 $ 946 $ 5,209 $ 2,446
Share-based Payment Arrangement, Cost by Plan	Stock-based compensation expense or benefit and the related income tax benefit is presented in the following table. The service period for performance stock units granted each year begins on January 1 of the following year. Three Months Ended Six Months Ended 2024 2023 2024 2023 Non-vested stock units $ 3,100 $ 2,864 $ 6,479 $ 6,171 Deferred stock units 934 880 934 880 Performance stock units 489 1,049 848 2,484 Total $ 4,523 $ 4,793 $ 8,261 $ 9,535 Income tax benefit $ 846 $ 800 $ 1,991 $ 1,868
Unrecognized Stock-Based Compensation Expense	Unrecognized stock-based compensation expense at June 30, 2024 is presented in the table below. Unrecognized stock-based compensation expense related to performance stock units is presented assuming attainment of the maximum payout rate as set forth by the performance criteria. Non-vested stock units $ 16,341 Performance stock units 7,583 Total $ 23,924

Earnings Per Common Share (Tabl

Earnings Per Common Share (Tables)	6 Months Ended
Earnings Per Common Share (Tables)	Jun. 30, 2024
Earnings Per Share [Abstract]
Basic and Diluted Earnings Per Common Share	The following table presents a reconciliation of net income available to common shareholders, net earnings allocated to common stock and the number of shares used in the calculation of basic and diluted earnings per common share. Three Months Ended Six Months Ended 2024 2023 2024 2023 Net income $ 145,499 $ 162,118 $ 281,189 $ 339,771 Less: Preferred stock dividends 1,669 1,669 3,338 3,338 Net income available to common shareholders 143,830 160,449 277,851 336,433 Less: Earnings allocated to participating securities 1,693 1,645 3,334 3,468 Net earnings allocated to common stock $ 142,137 $ 158,804 $ 274,517 $ 332,965 Distributed earnings allocated to common stock $ 59,108 $ 55,783 $ 118,188 $ 111,789 Undistributed earnings allocated to common stock 83,029 103,021 156,329 221,176 Net earnings allocated to common stock $ 142,137 $ 158,804 $ 274,517 $ 332,965 Weighted-average shares outstanding for basic earnings per common share 64,192,907 64,240,789 64,204,615 64,306,809 Dilutive effect of stock compensation 140,280 187,172 147,693 225,267 Weighted-average shares outstanding for diluted earnings per common share 64,333,187 64,427,961 64,352,308 64,532,076

Defined Benefit Plans (Tables)

Defined Benefit Plans (Tables)	6 Months Ended
Defined Benefit Plans (Tables)	Jun. 30, 2024
Retirement Benefits [Abstract]
Net Periodic Cost (Benefit)	The components of the combined net periodic expense (benefit) for our defined benefit pension plans are presented in the table below. Three Months Ended Six Months Ended 2024 2023 2024 2023 Expected return on plan assets, net of expenses $ (2,412) $ (2,740) $ (4,823) $ (5,480) Interest cost on projected benefit obligation 1,661 1,746 3,323 3,492 Net amortization and deferral 419 870 837 1,740 Net periodic expense (benefit) $ (332) $ (124) $ (663) $ (248)

Income Taxes (Tables)

Income Taxes (Tables)	6 Months Ended
Income Taxes (Tables)	Jun. 30, 2024
Income Tax Disclosure [Abstract]
Income Tax Expense	Income tax expense was as follows: Three Months Ended Six Months Ended 2024 2023 2024 2023 Current income tax expense $ 32,919 $ 32,413 $ 63,236 $ 67,408 Deferred income tax expense (benefit) (3,267) (680) (7,713) (2,489) Income tax expense, as reported $ 29,652 $ 31,733 $ 55,523 $ 64,919 Effective tax rate 16.9 % 16.4 % 16.5 % 16.0 %

Other Comprehensive Income (L_2

Other Comprehensive Income (Loss) (Tables)	6 Months Ended
Other Comprehensive Income (Loss) (Tables)	Jun. 30, 2024
Equity [Abstract]
Comprehensive Income (Loss)	The before and after-tax amounts allocated to each component of other comprehensive income (loss) are presented in the following table. Reclassification adjustments related to securities available for sale are included in net gain (loss) on securities transactions in the accompanying consolidated statements of income. Reclassification adjustments related to defined-benefit post-retirement benefit plans are included in the computation of net periodic pension expense (see Note 11 – Defined Benefit Plans). Three Months Ended Three Months Ended Before Tax Tax Expense, Net of Tax Before Tax Tax Expense, Net of Tax Securities available for sale and transferred securities: Change in net unrealized gain/loss during the period $ (42,111) $ (8,843) $ (33,268) $ (206,863) $ (43,441) $ (163,422) Change in net unrealized gain on securities transferred to held to maturity (157) (33) (124) (162) (34) (128) Reclassification adjustment for net (gains) losses included in net income — — — (33) (7) (26) Total securities available for sale and transferred securities (42,268) (8,876) (33,392) (207,058) (43,482) (163,576) Defined-benefit post-retirement benefit plans: Reclassification adjustment for net amortization of actuarial gain/loss included in net income as a component of net periodic cost (benefit) 419 88 331 870 183 687 Total defined-benefit post-retirement benefit plans 419 88 331 870 183 687 Total other comprehensive income (loss) $ (41,849) $ (8,788) $ (33,061) $ (206,188) $ (43,299) $ (162,889) Six Months Ended Six Months Ended Before Tax Tax Expense, Net of Tax Before Tax Tax Expense, Net of Tax Securities available for sale and transferred securities: Change in net unrealized gain/loss during the period $ (241,186) $ (50,649) $ (190,537) $ 53,406 $ 11,215 $ 42,191 Change in net unrealized gain on securities transferred to held to maturity (316) (67) (249) (322) (67) (255) Reclassification adjustment for net (gains) losses included in net income — — — (54) (11) (43) Total securities available for sale and transferred securities (241,502) (50,716) (190,786) 53,030 11,137 41,893 Defined-benefit post-retirement benefit plans: Reclassification adjustment for net amortization of actuarial gain/loss included in net income as a component of net periodic expense (benefit) 837 176 661 1,740 366 1,374 Total defined-benefit post-retirement benefit plans 837 176 661 1,740 366 1,374 Total other comprehensive income (loss) $ (240,665) $ (50,540) $ (190,125) $ 54,770 $ 11,503 $ 43,267
Schedule of Accumulated Other Comprehensive Income (Loss)	Activity in accumulated other comprehensive income (loss), net of tax, was as follows: Securities Defined Accumulated Balance at January 1, 2024 $ (1,094,794) $ (24,425) $ (1,119,219) Other comprehensive income (loss) before reclassifications (190,786) — (190,786) Reclassification of amounts included in net income — 661 661 Net other comprehensive income (loss) during period (190,786) 661 (190,125) Balance at June 30, 2024 $ (1,285,580) $ (23,764) $ (1,309,344) Balance at January 1, 2023 $ (1,313,791) $ (34,503) $ (1,348,294) Other comprehensive income (loss) before reclassifications 41,936 — 41,936 Reclassification of amounts included in net income (43) 1,374 1,331 Net other comprehensive income (loss) during period 41,893 1,374 43,267 Balance at June 30, 2023 $ (1,271,898) $ (33,129) $ (1,305,027)

Operating Segments (Tables)

Operating Segments (Tables)	6 Months Ended
Operating Segments (Tables)	Jun. 30, 2024
Segment Reporting [Abstract]
Summary of Operating Results by Segment	Summarized operating results by operating segment were as follows: Banking Frost Wealth Non-Banks Consolidated Three months ended: June 30, 2024 Net interest income (expense) $ 398,270 $ 1,907 $ (3,465) $ 396,712 Credit loss expense 15,787 — — 15,787 Non-interest income 62,178 49,489 (477) 111,190 Non-interest expense 276,196 37,875 2,893 316,964 Income (loss) before income taxes 168,465 13,521 (6,835) 175,151 Income tax expense (benefit) 28,819 2,839 (2,006) 29,652 Net income (loss) 139,646 10,682 (4,829) 145,499 Preferred stock dividends — — 1,669 1,669 Net income (loss) available to common shareholders $ 139,646 $ 10,682 $ (6,498) $ 143,830 Revenues from (expenses to) external customers $ 460,448 $ 51,396 $ (3,942) $ 507,902 June 30, 2023 Net interest income (expense) $ 385,720 $ 2,090 $ (2,544) $ 385,266 Credit loss expense (benefit) 9,901 — — 9,901 Non-interest income 57,808 46,147 (427) 103,528 Non-interest expense 246,927 35,558 2,557 285,042 Income (loss) before income taxes 186,700 12,679 (5,528) 193,851 Income tax expense (benefit) 30,636 2,663 (1,566) 31,733 Net income (loss) 156,064 10,016 (3,962) 162,118 Preferred stock dividends — — 1,669 1,669 Net income (loss) available to common shareholders $ 156,064 $ 10,016 $ (5,631) $ 160,449 Revenues from (expenses to) external customers $ 443,528 $ 48,237 $ (2,971) $ 488,794 Banking Frost Wealth Non-Banks Consolidated Six months ended: June 30, 2024 Net interest income (expense) $ 790,075 $ 3,576 $ (6,888) $ 786,763 Credit loss expense (benefit) 29,437 — — 29,437 Non-interest income 128,558 94,915 (906) 222,567 Non-interest expense 563,026 75,848 4,307 643,181 Income (loss) before income taxes 326,170 22,643 (12,101) 336,712 Income tax expense (benefit) 54,454 4,755 (3,686) 55,523 Net income (loss) 271,716 17,888 (8,415) 281,189 Preferred stock dividends — — 3,338 3,338 Net income (loss) available to common shareholders $ 271,716 $ 17,888 $ (11,753) $ 277,851 Revenues from (expenses to) external customers $ 918,633 $ 98,491 $ (7,794) $ 1,009,330 June 30, 2023 Net interest income (expense) $ 785,857 $ 3,744 $ (4,515) $ 785,086 Credit loss expense 19,005 — — 19,005 Non-interest income 121,451 88,185 (843) 208,793 Non-interest expense 496,792 69,507 3,885 570,184 Income (loss) before income taxes 391,511 22,422 (9,243) 404,690 Income tax expense (benefit) 62,754 4,709 (2,544) 64,919 Net income (loss) 328,757 17,713 (6,699) 339,771 Preferred stock dividends — — 3,338 3,338 Net income (loss) available to common shareholders $ 328,757 $ 17,713 $ (10,037) $ 336,433 Revenues from (expenses to) external customers $ 907,308 $ 91,929 $ (5,358) $ 993,879

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	6 Months Ended
Fair Value Measurements (Tables)	Jun. 30, 2024
Fair Value Disclosures [Abstract]
Financial Assets and Financial Liabilities Measured at Fair Value on Recurring Basis	The tables below summarize financial assets and financial liabilities measured at fair value on a recurring basis as of June 30, 2024 and December 31, 2023, segregated by the level of the valuation inputs within the fair value hierarchy of ASC Topic 820 utilized to measure fair value. Level 1 Inputs Level 2 Inputs Level 3 Inputs Total Fair Value June 30, 2024 Securities available for sale: U.S. Treasury $ 3,882,331 $ — $ — $ 3,882,331 Residential mortgage-backed securities — 6,537,427 — 6,537,427 States and political subdivisions — 4,734,909 — 4,734,909 Other — 42,971 — 42,971 Trading account securities: U.S. Treasury 31,400 — — 31,400 States and political subdivisions — 786 — 786 Derivative assets: Interest rate swaps, caps, and floors — 87,257 — 87,257 Commodity swaps and options — 56,293 — 56,293 Derivative liabilities: Interest rate swaps, caps, and floors — 87,254 — 87,254 Commodity swaps and options — 54,819 — 54,819 December 31, 2023 Securities available for sale: U.S. Treasury $ 4,927,589 $ — $ — $ 4,927,589 Residential mortgage-backed securities — 6,596,682 — 6,596,682 States and political subdivisions — 5,011,331 — 5,011,331 Other — 42,769 — 42,769 Trading account securities: U.S. Treasury 30,265 — — 30,265 States and political subdivisions — 1,452 — 1,452 Derivative assets: Interest rate swaps, caps, and floors — 90,715 — 90,715 Commodity swaps and options — 70,710 — 70,710 Foreign currency forward contracts 22 — — 22 Derivative liabilities: Interest rate swaps, caps, and floors — 90,525 — 90,525 Commodity swaps and options — 69,447 — 69,447 Foreign currency forward contracts 19 — — 19
Impaired Loans Remeasured And Reported At Fair Value Specific Valuation Allowance Allocation Method Of Underlying Collateral [Table Text Block]	The following table presents collateral dependent loans that were remeasured and reported at fair value through a specific allocation of the allowance for credit losses on loans based upon the fair value of the underlying collateral during the reported periods. Six Months Ended Six Months Ended Level 2 Level 3 Level 2 Level 3 Carrying value before allocations $ 17,832 $ 14,159 $ 19,064 $ 20,171 Specific (allocations) reversals of prior allocations (1,916) (1,501) (1,300) (2,100) Fair value $ 15,916 $ 12,658 $ 17,764 $ 18,071
Estimated Fair Values of Financial Instruments	The estimated fair values of financial instruments that are reported at amortized cost in our consolidated balance sheets, segregated by the level of the valuation inputs within the fair value hierarchy utilized to measure fair value, were as follows: June 30, 2024 December 31, 2023 Carrying Estimated Carrying Estimated Financial assets: Level 2 inputs: Cash and cash equivalents $ 7,144,784 $ 7,144,784 $ 8,687,276 $ 8,687,276 Securities held to maturity 3,586,116 3,416,937 3,619,428 3,532,044 Accrued interest receivable 243,951 243,951 251,385 251,385 Level 3 inputs: Loans, net 19,739,449 19,241,857 18,578,255 18,117,369 Financial liabilities: Level 2 inputs: Deposits 40,318,140 40,303,423 41,920,568 41,903,580 Federal funds purchased 35,925 35,925 14,200 14,200 Repurchase agreements 3,762,942 3,762,942 4,127,188 4,127,188 Junior subordinated deferrable interest debentures 123,155 123,712 123,127 123,712 Subordinated notes 99,569 96,645 99,491 96,071 Accrued interest payable 66,812 66,812 61,222 61,222

Significant Accounting Polici_4

Significant Accounting Policies - Additional Cash Flow Information (Detail) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023
Accounting Policies [Abstract]
Cash paid for interest	$ 389,432	$ 270,358
Cash paid for income taxes	62,000	66,500
Unsettled securities transactions	29,011	10,988
Right-of-use lease assets obtained in exchange for lessee operating lease liabilities	$ 9,218	$ 8,914

Securities - Additional Informa

Securities - Additional Information (Detail) - USD ($) $ in Thousands	Jun. 30, 2024	Dec. 31, 2023
Schedule Of Marketable Securities [Line Items]
AOCI, Debt Securities, Available-for-sale, Adjustment, Pre Tax	$ 835	$ 1,200
Net unamortized unrealized gain on transferred securities included in accumulated other comprehensive income, net of tax	$ 660	909
Percent Municipal Bond Portfolio Issued By Political Subdivision Or Agencies Within State Of Texas Guaranteed By Texas Permanent School Fund Or Have Been Pre-Refunded	72.90%
Debt Securities, Available-for-sale, Allowance for Credit Loss	$ 0	0
Held-to-maturity Securities [Member]
Schedule Of Marketable Securities [Line Items]
Carry Value of Securities Pledged	1,300,000	1,000,000
Accrued interest receivable	38,200	40,900
Available-for-sale Securities [Member]
Schedule Of Marketable Securities [Line Items]
Carry Value of Securities Pledged	5,300,000	6,100,000
Accrued interest receivable	$ 105,200	$ 114,900

Securities Securities - Amortiz

Securities Securities - Amortized Cost, Allowance for Credit Losses and Estimated Fair Value of Securities Held to Maturity (Details) - USD ($) $ in Thousands	Jun. 30, 2024	Dec. 31, 2023
Schedule of Investments [Line Items]
Held to Maturity, Amortized Cost	$ 3,586,426	$ 3,619,738
Debt Securities, Held-to-maturity, Accumulated Unrecognized Gain	17,319	43,066
Debt Securities, Held-to-maturity, Accumulated Unrecognized Loss	186,808	130,760
Debt Securities, Held-to-maturity, Fair Value	3,416,937	3,532,044
Securities, held-to-maturity, allowance for credit loss	(310)	(310)
Securities held to maturity, net of allowance for credit losses of $310 at both June 30, 2024 and December 31, 2023	3,586,116	3,619,428
Residential Mortgage Backed Securities [Member]
Schedule of Investments [Line Items]
Held to Maturity, Amortized Cost	1,225,779	1,250,431
Debt Securities, Held-to-maturity, Accumulated Unrecognized Gain	0	76
Debt Securities, Held-to-maturity, Accumulated Unrecognized Loss	74,853	54,175
Debt Securities, Held-to-maturity, Fair Value	1,150,926	1,196,332
Securities, held-to-maturity, allowance for credit loss	0	0
Securities held to maturity, net of allowance for credit losses of $310 at both June 30, 2024 and December 31, 2023	1,225,779	1,250,431
US States and Political Subdivisions Debt Securities [Member]
Schedule of Investments [Line Items]
Held to Maturity, Amortized Cost	2,359,147	2,367,807
Debt Securities, Held-to-maturity, Accumulated Unrecognized Gain	17,319	42,990
Debt Securities, Held-to-maturity, Accumulated Unrecognized Loss	111,929	76,540
Debt Securities, Held-to-maturity, Fair Value	2,264,537	2,334,257
Securities, held-to-maturity, allowance for credit loss	(310)	(310)
Securities held to maturity, net of allowance for credit losses of $310 at both June 30, 2024 and December 31, 2023	2,358,837	2,367,497
Other Investments [Member]
Schedule of Investments [Line Items]
Held to Maturity, Amortized Cost	1,500	1,500
Debt Securities, Held-to-maturity, Accumulated Unrecognized Gain	0	0
Debt Securities, Held-to-maturity, Accumulated Unrecognized Loss	26	45
Debt Securities, Held-to-maturity, Fair Value	1,474	1,455
Securities, held-to-maturity, allowance for credit loss	0	0
Securities held to maturity, net of allowance for credit losses of $310 at both June 30, 2024 and December 31, 2023	$ 1,500	$ 1,500

Securities Securities - Moody's

Securities Securities - Moody's and/or Standard & Poor's Bond Rating (Details) - USD ($) $ in Thousands	Jun. 30, 2024	Dec. 31, 2023
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-maturity	$ 3,586,426	$ 3,619,738
US States and Political Subdivisions Debt Securities [Member]
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-maturity	2,359,147	2,367,807
Other Investments [Member]
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-maturity	1,500	1,500
Moody's, Aaa Rating \| US States and Political Subdivisions Debt Securities [Member]
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-maturity	1,854,480	1,858,686
Moody's, Aaa Rating \| Other Investments [Member]
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-maturity	0	0
Moody's, Aa1 Rating \| US States and Political Subdivisions Debt Securities [Member]
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-maturity	504,667	509,121
Moody's, Aa1 Rating \| Other Investments [Member]
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-maturity	0	0
Not rated [Member] \| US States and Political Subdivisions Debt Securities [Member]
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-maturity	0	0
Not rated [Member] \| Other Investments [Member]
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-maturity	1,500	1,500
Not Guaranteed or Pre-Refunded [Member] \| US States and Political Subdivisions Debt Securities [Member]
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-maturity	800,075	804,737
Not Guaranteed or Pre-Refunded [Member] \| Moody's, Aaa Rating \| US States and Political Subdivisions Debt Securities [Member]
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-maturity	301,518	301,721
Not Guaranteed or Pre-Refunded [Member] \| Moody's, Aa1 Rating \| US States and Political Subdivisions Debt Securities [Member]
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-maturity	498,557	503,016
Not Guaranteed or Pre-Refunded [Member] \| Not rated [Member] \| US States and Political Subdivisions Debt Securities [Member]
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-maturity	0	0
Guaranteed by the Texas PSF [Member] \| US States and Political Subdivisions Debt Securities [Member]
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-maturity	1,538,227	1,541,913
Guaranteed by the Texas PSF [Member] \| Moody's, Aaa Rating \| US States and Political Subdivisions Debt Securities [Member]
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-maturity	1,538,227	1,541,913
Guaranteed by the Texas PSF [Member] \| Moody's, Aa1 Rating \| US States and Political Subdivisions Debt Securities [Member]
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-maturity	0	0
Guaranteed by the Texas PSF [Member] \| Not rated [Member] \| US States and Political Subdivisions Debt Securities [Member]
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-maturity	0	0
Guaranteed by Third Party \| US States and Political Subdivisions Debt Securities [Member]
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-maturity	19,755	19,756
Guaranteed by Third Party \| Moody's, Aaa Rating \| US States and Political Subdivisions Debt Securities [Member]
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-maturity	13,645	13,651
Guaranteed by Third Party \| Moody's, Aa1 Rating \| US States and Political Subdivisions Debt Securities [Member]
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-maturity	6,110	6,105
Guaranteed by Third Party \| Not rated [Member] \| US States and Political Subdivisions Debt Securities [Member]
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-maturity	0	0
Pre-Refunded [Member] \| US States and Political Subdivisions Debt Securities [Member]
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-maturity	1,090	1,401
Pre-Refunded [Member] \| Moody's, Aaa Rating \| US States and Political Subdivisions Debt Securities [Member]
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-maturity	1,090	1,401
Pre-Refunded [Member] \| Moody's, Aa1 Rating \| US States and Political Subdivisions Debt Securities [Member]
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-maturity	0	0
Pre-Refunded [Member] \| Not rated [Member] \| US States and Political Subdivisions Debt Securities [Member]
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-maturity	$ 0	$ 0

Securities Securities - Allowan

Securities Securities - Allowance for Credit Losses on Held to Maturity Securities (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023	Mar. 31, 2024	Dec. 31, 2023	Mar. 31, 2023	Dec. 31, 2022
Schedule of Held-to-maturity Securities [Line Items]
Securities, held-to-maturity, allowance for credit loss	$ 310		$ 310			$ 310
Debt Securities [Member]
Schedule of Held-to-maturity Securities [Line Items]
Securities, held-to-maturity, allowance for credit loss	310	$ 267	310	$ 267	$ 310	$ 310	$ 262	$ 158
Credit loss expense (benefit)	$ 0	$ 5	$ 0	$ 109

Securities Securities - Amort_2

Securities Securities - Amortized Cost, Allowance for Credit Losses and Estimated Fair Value of Securities Available for Sale (Details) - USD ($) $ in Thousands	Jun. 30, 2024	Dec. 31, 2023
Schedule of Investments [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	$ 16,825,791	$ 17,965,338
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	5,156	14,828
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	1,633,309	1,401,795
Debt Securities, Available-for-sale, Allowance for Credit Loss	0	0
Securities available for sale, at estimated fair value	15,197,638	16,578,371
US Treasury Securities [Member]
Schedule of Investments [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	4,184,938	5,212,894
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	0	0
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	302,607	285,305
Debt Securities, Available-for-sale, Allowance for Credit Loss	0	0
Securities available for sale, at estimated fair value	3,882,331	4,927,589
Residential Mortgage Backed Securities [Member]
Schedule of Investments [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	7,567,795	7,463,954
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	2,840	9,066
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	1,033,208	876,338
Debt Securities, Available-for-sale, Allowance for Credit Loss	0	0
Securities available for sale, at estimated fair value	6,537,427	6,596,682
US States and Political Subdivisions Debt Securities [Member]
Schedule of Investments [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	5,030,087	5,245,721
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	2,316	5,762
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	297,494	240,152
Debt Securities, Available-for-sale, Allowance for Credit Loss	0	0
Securities available for sale, at estimated fair value	4,734,909	5,011,331
Other Investments [Member]
Schedule of Investments [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	42,971	42,769
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	0	0
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	0	0
Debt Securities, Available-for-sale, Allowance for Credit Loss	0	0
Securities available for sale, at estimated fair value	$ 42,971	$ 42,769

Securities - Securities Availab

Securities - Securities Available for Sale, with Unrealized Losses Segregated by Length of Impairment (Detail) - USD ($) $ in Thousands	Jun. 30, 2024	Dec. 31, 2023
Schedule of Available-for-Sale Securities [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	$ 1,191,218
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	13,036
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	13,319,570
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	1,620,273
Debt Securities, Available-for-sale, Unrealized Loss Position	14,510,788
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	1,633,309	$ 1,401,795
U.S. Treasury [Member]
Schedule of Available-for-Sale Securities [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	0
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	0
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	3,882,331
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	302,607
Debt Securities, Available-for-sale, Unrealized Loss Position	3,882,331
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	302,607	285,305
Residential Mortgage Backed Securities [Member]
Schedule of Available-for-Sale Securities [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	508,001
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	5,469
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	5,561,705
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	1,027,739
Debt Securities, Available-for-sale, Unrealized Loss Position	6,069,706
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	1,033,208	876,338
States and political subdivisions [Member]
Schedule of Available-for-Sale Securities [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	683,217
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	7,567
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	3,875,534
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	289,927
Debt Securities, Available-for-sale, Unrealized Loss Position	4,558,751
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	$ 297,494	$ 240,152

Securities - Amortized Cost and

Securities - Amortized Cost and Estimated Fair Value of Securities, Excluding Trading Securities, Presented by Contractual Maturity (Detail) - USD ($) $ in Thousands	Jun. 30, 2024	Dec. 31, 2023
Schedule of Investments [Line Items]
Held to Maturity, Due in one year or less, Amortized Cost	$ 10,595
Held to Maturity, Due after one year through five years, Amortized Cost	47,873
Held to Maturity, Due after five years through ten years, Amortized Cost	519,679
Held to Maturity, Due after ten years, Amortized Cost	3,008,279
Held to Maturity, Amortized Cost	3,586,426	$ 3,619,738
Held to Maturity, Due in one year or less, Estimated Fair Value	10,542
Held to Maturity, Due after one year through five years, Estimated Fair Value	42,792
Held to Maturity, Due after five years through ten years, Estimated Fair Value	466,196
Held to Maturity, Due after ten years, Estimated Fair Value	2,897,407
Held to Maturity, Estimated Fair Value	3,416,937	3,532,044
Available-for-sale Securities, Due in one year or less, Amortized Cost	1,350,261
Available for Sale, Due after one year through five years, Amortized Cost	2,871,230
Available for Sale, Due after five years through ten years, Amortized Cost	1,041,790
Available for Sale, Due after ten years, Amortized Cost	11,519,539
Debt Securities, Available-for-sale, Amortized Cost	16,825,791	17,965,338
Available for Sale, Due in one year or less, Estimated Fair Value	1,329,223
Available for Sale, Due after one year through five years, Estimated Fair Value	2,673,907
Available for Sale, Due after five years through ten years, Estimated Fair Value	964,649
Available for Sale, Due after ten years, Estimated Fair Value	10,186,888
Securities available for sale, at estimated fair value	15,197,638	16,578,371
US Treasury Securities [Member]
Schedule of Investments [Line Items]
Available-for-sale Securities, Due in one year or less, Amortized Cost	1,173,271
Available for Sale, Due after one year through five years, Amortized Cost	2,621,114
Available for Sale, Due after five years through ten years, Amortized Cost	197,956
Available for Sale, Due after ten years, Amortized Cost	192,597
Debt Securities, Available-for-sale, Amortized Cost	4,184,938	5,212,894
Available for Sale, Due in one year or less, Estimated Fair Value	1,152,647
Available for Sale, Due after one year through five years, Estimated Fair Value	2,428,473
Available for Sale, Due after five years through ten years, Estimated Fair Value	163,742
Available for Sale, Due after ten years, Estimated Fair Value	137,469
Securities available for sale, at estimated fair value	3,882,331	4,927,589
Residential Mortgage Backed Securities [Member]
Schedule of Investments [Line Items]
Held to Maturity, Due in one year or less, Amortized Cost	0
Held to Maturity, Due after one year through five years, Amortized Cost	43,600
Held to Maturity, Due after five years through ten years, Amortized Cost	467,780
Held to Maturity, Due after ten years, Amortized Cost	714,399
Held to Maturity, Amortized Cost	1,225,779	1,250,431
Held to Maturity, Due in one year or less, Estimated Fair Value	0
Held to Maturity, Due after one year through five years, Estimated Fair Value	38,538
Held to Maturity, Due after five years through ten years, Estimated Fair Value	416,882
Held to Maturity, Due after ten years, Estimated Fair Value	695,506
Held to Maturity, Estimated Fair Value	1,150,926	1,196,332
Available-for-sale Securities, Due in one year or less, Amortized Cost	702
Available for Sale, Due after one year through five years, Amortized Cost	1,118
Available for Sale, Due after five years through ten years, Amortized Cost	13,084
Available for Sale, Due after ten years, Amortized Cost	7,552,891
Debt Securities, Available-for-sale, Amortized Cost	7,567,795	7,463,954
Available for Sale, Due in one year or less, Estimated Fair Value	696
Available for Sale, Due after one year through five years, Estimated Fair Value	1,121
Available for Sale, Due after five years through ten years, Estimated Fair Value	13,116
Available for Sale, Due after ten years, Estimated Fair Value	6,522,494
Securities available for sale, at estimated fair value	6,537,427	6,596,682
US States and Political Subdivisions Debt Securities [Member]
Schedule of Investments [Line Items]
Held to Maturity, Due in one year or less, Amortized Cost	9,095
Held to Maturity, Due after one year through five years, Amortized Cost	4,273
Held to Maturity, Due after five years through ten years, Amortized Cost	51,899
Held to Maturity, Due after ten years, Amortized Cost	2,293,880
Held to Maturity, Amortized Cost	2,359,147	2,367,807
Held to Maturity, Due in one year or less, Estimated Fair Value	9,068
Held to Maturity, Due after one year through five years, Estimated Fair Value	4,254
Held to Maturity, Due after five years through ten years, Estimated Fair Value	49,314
Held to Maturity, Due after ten years, Estimated Fair Value	2,201,901
Held to Maturity, Estimated Fair Value	2,264,537	2,334,257
Available-for-sale Securities, Due in one year or less, Amortized Cost	176,288
Available for Sale, Due after one year through five years, Amortized Cost	248,998
Available for Sale, Due after five years through ten years, Amortized Cost	830,750
Available for Sale, Due after ten years, Amortized Cost	3,774,051
Debt Securities, Available-for-sale, Amortized Cost	5,030,087	5,245,721
Available for Sale, Due in one year or less, Estimated Fair Value	175,880
Available for Sale, Due after one year through five years, Estimated Fair Value	244,313
Available for Sale, Due after five years through ten years, Estimated Fair Value	787,791
Available for Sale, Due after ten years, Estimated Fair Value	3,526,925
Securities available for sale, at estimated fair value	4,734,909	5,011,331
Other Investments [Member]
Schedule of Investments [Line Items]
Held to Maturity, Due in one year or less, Amortized Cost	1,500
Held to Maturity, Due after one year through five years, Amortized Cost	0
Held to Maturity, Due after five years through ten years, Amortized Cost	0
Held to Maturity, Due after ten years, Amortized Cost	0
Held to Maturity, Amortized Cost	1,500	1,500
Held to Maturity, Due in one year or less, Estimated Fair Value	1,474
Held to Maturity, Due after one year through five years, Estimated Fair Value	0
Held to Maturity, Due after five years through ten years, Estimated Fair Value	0
Held to Maturity, Due after ten years, Estimated Fair Value	0
Held to Maturity, Estimated Fair Value	1,474	1,455
Available-for-sale Securities, Due in one year or less, Amortized Cost	0
Available for Sale, Due after one year through five years, Amortized Cost	0
Available for Sale, Due after five years through ten years, Amortized Cost	0
Available for Sale, Due after ten years, Amortized Cost	0
Debt Securities, Available-for-sale, Amortized Cost	42,971	42,769
Available for Sale, Due in one year or less, Estimated Fair Value	0
Available for Sale, Due after one year through five years, Estimated Fair Value	0
Available for Sale, Due after five years through ten years, Estimated Fair Value	0
Available for Sale, Due after ten years, Estimated Fair Value	0
Securities available for sale, at estimated fair value	$ 42,971	$ 42,769

Securities - Sales of Available

Securities - Sales of Available for Sale Securities (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Investments, Debt and Equity Securities [Abstract]
Proceeds from sales	$ 0	$ 659,082	$ 0	$ 1,543,355
Gross realized gains	0	561	0	5,417
Gross realized losses	0	(528)	0	(5,363)
Tax (expense) benefit of securities gains/losses	$ 0	$ (7)	$ 0	$ (11)

Securities Securities - Premium

Securities Securities - Premium Amortization and Discount Accretion Included in Income on Securities (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Investments, Debt and Equity Securities [Abstract]
Premium amortization	$ (16,570)	$ (21,242)	$ (34,523)	$ (47,167)
Discount accretion	5,032	4,843	9,737	10,248
Net (premium amortization) discount accretion	$ (11,538)	$ (16,399)	$ (24,786)	$ (36,919)

Securities - Trading Account Se

Securities - Trading Account Securities, at Estimated Fair Value (Detail) - USD ($) $ in Thousands	Jun. 30, 2024	Dec. 31, 2023
Debt and Equity Securities, FV-NI [Line Items]
Trading account securities	$ 32,186	$ 31,717
U.S. Treasury [Member]
Debt and Equity Securities, FV-NI [Line Items]
Trading account securities	31,400	30,265
States and political subdivisions [Member]
Debt and Equity Securities, FV-NI [Line Items]
Trading account securities	$ 786	$ 1,452

Securities - Net Gains and Loss

Securities - Net Gains and Losses on Trading Account Securities (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Investments, Debt and Equity Securities [Abstract]
Net gain on sales transactions	$ 1,223	$ 903	$ 2,382	$ 1,871
Net mark-to-market gains (losses)	(82)	(10)	(101)	(27)
Net gain (loss) on trading account securities	$ 1,141	$ 893	$ 2,281	$ 1,844

Loans - Additional Information

Loans - Additional Information (Detail) $ in Thousands	3 Months Ended		6 Months Ended
Loans - Additional Information (Detail) $ in Thousands	Jun. 30, 2024 USD ($)	Jun. 30, 2023 USD ($)	Jun. 30, 2024 USD ($)	Jun. 30, 2023 USD ($)	Mar. 31, 2024 USD ($)	Dec. 31, 2023 USD ($)	Mar. 31, 2023 USD ($)	Dec. 31, 2022 USD ($)
Accounts, Notes, Loans and Financing Receivable [Line Items]
Concentration of loans in a single industry in excess of ten percent	0%		0%
Maximum percentage loan related to single industry	10%		10%
U.S. dollar denominated loans and commitments to borrowers in Mexico	$ 0		$ 0			$ 0
Loans and Leases Receivable, Related Parties	$ 281,000		$ 281,000			$ 416,100
Texas Leading Index economic condition indicator	116.9		116.9			127.2
Financing Receivable, Change in Method, Credit Loss Expense (Reversal)			$ 7,200
Financing Receivable, Allowance for Credit Loss	$ 256,307		256,307			$ 245,996
Loans, net of unearned discounts	19,995,756		19,995,756			18,824,251
Nonperforming Financial Instruments [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	5,596		5,596
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	23,879		23,879
Financial Asset, Other than Financial Asset Acquired with Credit Deterioration \| Nonperforming Financial Instruments [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	9,369		9,369
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	$ 6,263		$ 6,263
Combination: Payment Delay and Term Extention
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts		$ 36,486		$ 36,486
Automobile Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Percentage of total loans	5.80%		5.80%
Commercial and Industrial Total Energy Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Percentage of total loans	5.40%		5.40%
Financing Receivable, Allowance for Credit Loss	$ 11,485	14,929	$ 11,485	14,929	$ 14,218	17,814	$ 19,191	$ 18,062
Financing Receivable, Allowance for Credit Loss, Writeoff	79	518	79	518
Loans, net of unearned discounts	1,096,657		1,096,657			936,737
Financing Receivable, Year One, Originated, Current Fiscal Year	304,570		304,570
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	36,014		36,014
Commercial and Industrial Total Energy Loans [Member] \| Nonperforming Financial Instruments [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	4,522		4,522
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	0		0
Commercial and Industrial Total Energy Loans [Member] \| Financial Asset, Other than Financial Asset Acquired with Credit Deterioration \| Nonperforming Financial Instruments [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	0		0
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	79		79
Non Accrual Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Additional interest that would have been recognized on non-accrual loans, net of tax	1,300	835	2,500	1,400
Total consumer real estate loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Allowance for Credit Loss	15,707	13,035	15,707	13,035	13,857	13,538	9,708	8,004
Financing Receivable, Allowance for Credit Loss, Writeoff	408	1,080	2,077	1,330
Loans, net of unearned discounts	2,740,728		2,740,728			2,460,726
Total consumer real estate loans [Member] \| Nonperforming Financial Instruments [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	0		0
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	0		0
Total consumer real estate loans [Member] \| Financial Asset, Other than Financial Asset Acquired with Credit Deterioration \| Nonperforming Financial Instruments [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	0		0
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	0		0
Commercial Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Allowance for Credit Loss	78,554	75,166	78,554	75,166	75,596	74,006	78,465	104,237
Financing Receivable, Allowance for Credit Loss, Writeoff	4,282	7,136	6,426	13,316
Loans, net of unearned discounts	6,210,179		6,210,179			5,967,182
Financing Receivable, Year One, Originated, Current Fiscal Year	1,208,188		1,208,188
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	719,078		719,078
Commercial Portfolio Segment [Member] \| Nonperforming Financial Instruments [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	746		746
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	3,764		3,764
Commercial Portfolio Segment [Member] \| Financial Asset, Other than Financial Asset Acquired with Credit Deterioration \| Nonperforming Financial Instruments [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	0		0
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	471		471
Commercial Portfolio Segment [Member] \| Additional Funding Agreement Terms
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	0		0
Commercial Portfolio Segment [Member] \| Combination: Payment Delay and Term Extention
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	27,731	16,020	27,731	16,020
Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Change in Method, Credit Loss Expense (Reversal)			923
Financing Receivable, Allowance for Credit Loss	10,541	9,563	10,541	9,563	$ 8,402	10,040	$ 8,457	$ 7,017
Financing Receivable, Allowance for Credit Loss, Writeoff	8,360	$ 7,016	16,617	$ 13,958
Loans, net of unearned discounts	452,980		452,980			476,962
Consumer Loan [Member] \| Nonperforming Financial Instruments [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	0		0
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	0		0
Consumer Loan [Member] \| Financial Asset, Other than Financial Asset Acquired with Credit Deterioration \| Nonperforming Financial Instruments [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	9,369		9,369
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	5,713		5,713
Bank Overdrafts \| Financial Asset, Other than Financial Asset Acquired with Credit Deterioration \| Nonperforming Financial Instruments [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	9,400		9,400
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	5,500		5,500
Commercial mortgage [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Change in Method, Credit Loss Expense (Reversal)			6,200
Loans, net of unearned discounts	6,955,118		6,955,118			6,746,709
Commitments to Extend Credit [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financial instruments with off- balance-sheet risk	11,908,533		11,908,533			12,195,073
Commitments to Extend Credit [Member] \| Automobile Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unfunded balances	490,400		490,400
Commitments to Extend Credit [Member] \| Commercial and Industrial Total Energy Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unfunded balances	1,000,000		1,000,000
Standby Letters of Credit [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financial instruments with off- balance-sheet risk	404,673		404,673			438,635
Standby Letters of Credit [Member] \| Automobile Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unfunded balances	20,300		20,300
Standby Letters of Credit [Member] \| Commercial and Industrial Total Energy Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unfunded balances	65,800		65,800
Loans Receivable [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Interest Receivable	$ 96,200		$ 96,200			$ 90,800

Loans - Loans (Detail)

Loans - Loans (Detail) - USD ($) $ in Thousands	Jun. 30, 2024	Dec. 31, 2023
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	$ 19,995,756	$ 18,824,251
Commercial Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	6,210,179	5,967,182
Energy Production [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	858,990	681,568
Energy Service [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	209,658	194,126
Energy Other [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	28,009	61,043
Commercial and Industrial Total Energy Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	1,096,657	936,737
Commercial mortgage [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	6,955,118	6,746,709
Construction Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	1,997,545	1,680,724
Commercial land loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	542,549	555,211
Commercial Real Estate Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	9,495,212	8,982,644
Home Equity Line of Credit [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	832,307	792,876
Home Equity Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	790,727	694,966
Home Improvement Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	813,799	765,887
Other consumer real estate loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	303,895	206,997
Total consumer real estate loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	2,740,728	2,460,726
Real Estate Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	12,235,940	11,443,370
Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	$ 452,980	$ 476,962

Loans - Non-Accrual Loans, Segr

Loans - Non-Accrual Loans, Segregated by Class of Loans (Detail) - USD ($) $ in Thousands	Jun. 30, 2024	Dec. 31, 2023
Non Accrual Loans Segregated By Class Of Loans [Line Items]
Non-accrual loans	$ 74,987	$ 60,907
Non-accrual with no credit loss allowance	32,376	22,932
Commercial Portfolio Segment [Member]
Non Accrual Loans Segregated By Class Of Loans [Line Items]
Non-accrual loans	26,329	19,545
Non-accrual with no credit loss allowance	8,044	5,391
Commercial and Industrial Total Energy Loans [Member]
Non Accrual Loans Segregated By Class Of Loans [Line Items]
Non-accrual loans	9,147	11,500
Non-accrual with no credit loss allowance	6,045	7,398
Commercial Real Estate Buildings Land And Other Loans [Member]
Non Accrual Loans Segregated By Class Of Loans [Line Items]
Non-accrual loans	33,092	22,420
Non-accrual with no credit loss allowance	14,099	4,983
Construction Loans [Member]
Non Accrual Loans Segregated By Class Of Loans [Line Items]
Non-accrual loans	0	0
Non-accrual with no credit loss allowance	0	0
Total consumer real estate loans [Member]
Non Accrual Loans Segregated By Class Of Loans [Line Items]
Non-accrual loans	6,419	7,442
Non-accrual with no credit loss allowance	4,188	5,160
Consumer Loan [Member]
Non Accrual Loans Segregated By Class Of Loans [Line Items]
Non-accrual loans	0	0
Non-accrual with no credit loss allowance	$ 0	$ 0

Loans Loans - Non-Accrual Loans

Loans Loans - Non-Accrual Loans, Segregated by Class of Loans and Year of Origination (Details) - USD ($) $ in Thousands	Jun. 30, 2024	Dec. 31, 2023
Loans and Leases Receivable Disclosure [Line Items]
Non-accrual loans	$ 74,987	$ 60,907
Nonperforming Financial Instruments [Member]
Loans and Leases Receivable Disclosure [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	5,596
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	23,879
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	4,186
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	8,440
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	570
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	11,348
Financing Receivable, Revolving	8,088
Financing Receivable, Revolving, Converted to Term Loan	12,880
Commercial Portfolio Segment [Member]
Loans and Leases Receivable Disclosure [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	1,208,188
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	719,078
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	667,895
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	391,455
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	321,844
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	342,978
Financing Receivable, Revolving	2,486,421
Non-accrual loans	26,329	19,545
Commercial Portfolio Segment [Member] \| Nonperforming Financial Instruments [Member]
Loans and Leases Receivable Disclosure [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	746
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	3,764
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	1,159
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	3,066
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	514
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	2,197
Financing Receivable, Revolving	2,149
Financing Receivable, Revolving, Converted to Term Loan	12,734
Commercial and Industrial Total Energy Loans [Member]
Loans and Leases Receivable Disclosure [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	304,570
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	36,014
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	55,059
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	50,104
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	4,055
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	10,415
Financing Receivable, Revolving	628,754
Non-accrual loans	9,147	11,500
Commercial and Industrial Total Energy Loans [Member] \| Nonperforming Financial Instruments [Member]
Loans and Leases Receivable Disclosure [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	4,522
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	0
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	0
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	0
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	56
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	1,321
Financing Receivable, Revolving	3,102
Financing Receivable, Revolving, Converted to Term Loan	146
Commercial Real Estate Buildings Land And Other Loans [Member]
Loans and Leases Receivable Disclosure [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	690,654
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	1,490,259
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	1,708,392
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	1,234,202
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	751,974
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	1,296,706
Financing Receivable, Revolving	167,257
Non-accrual loans	33,092	22,420
Commercial Real Estate Buildings Land And Other Loans [Member] \| Nonperforming Financial Instruments [Member]
Loans and Leases Receivable Disclosure [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	328
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	20,115
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	3,027
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	5,374
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	0
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	1,411
Financing Receivable, Revolving	2,837
Financing Receivable, Revolving, Converted to Term Loan	0
Construction Loans [Member]
Loans and Leases Receivable Disclosure [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	351,397
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	516,044
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	647,171
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	298,063
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	28,003
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	1,296
Financing Receivable, Revolving	155,406
Non-accrual loans	0	0
Construction Loans [Member] \| Nonperforming Financial Instruments [Member]
Loans and Leases Receivable Disclosure [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	0
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	0
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	0
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	0
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	0
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	0
Financing Receivable, Revolving	0
Financing Receivable, Revolving, Converted to Term Loan	0
Total consumer real estate loans [Member]
Loans and Leases Receivable Disclosure [Line Items]
Non-accrual loans	6,419	7,442
Total consumer real estate loans [Member] \| Nonperforming Financial Instruments [Member]
Loans and Leases Receivable Disclosure [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	0
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	0
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	0
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	0
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	0
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	6,419
Financing Receivable, Revolving	0
Financing Receivable, Revolving, Converted to Term Loan	0
Consumer Loan [Member]
Loans and Leases Receivable Disclosure [Line Items]
Non-accrual loans	0	$ 0
Consumer Loan [Member] \| Nonperforming Financial Instruments [Member]
Loans and Leases Receivable Disclosure [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	0
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	0
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	0
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	0
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	0
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	0
Financing Receivable, Revolving	0
Financing Receivable, Revolving, Converted to Term Loan	$ 0

Loans - Age Analysis of Past Du

Loans - Age Analysis of Past Due Loans, Segregated by Class of Loans (Detail) - USD ($) $ in Thousands	Jun. 30, 2024	Dec. 31, 2023
Financing Receivable, Past Due [Line Items]
Total loans	$ 19,995,756	$ 18,824,251
Accruing Loans 90 or More Days Past Due	12,539
Commercial Portfolio Segment [Member]
Financing Receivable, Past Due [Line Items]
Total loans	6,210,179	5,967,182
Accruing Loans 90 or More Days Past Due	5,568
Commercial and Industrial Total Energy Loans [Member]
Financing Receivable, Past Due [Line Items]
Total loans	1,096,657	936,737
Accruing Loans 90 or More Days Past Due	0
Commercial Real Estate Buildings Land And Other Loans [Member]
Financing Receivable, Past Due [Line Items]
Total loans	7,497,667	7,301,920
Accruing Loans 90 or More Days Past Due	1,687
Construction Loans [Member]
Financing Receivable, Past Due [Line Items]
Total loans	1,997,545	1,680,724
Accruing Loans 90 or More Days Past Due	0
Total consumer real estate loans [Member]
Financing Receivable, Past Due [Line Items]
Total loans	2,740,728	2,460,726
Accruing Loans 90 or More Days Past Due	4,707
Consumer Loan [Member]
Financing Receivable, Past Due [Line Items]
Total loans	452,980	$ 476,962
Accruing Loans 90 or More Days Past Due	577
Financing Receivables, 30 to 89 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	107,006
Financing Receivables, 30 to 89 Days Past Due [Member] \| Commercial Portfolio Segment [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	38,806
Financing Receivables, 30 to 89 Days Past Due [Member] \| Commercial and Industrial Total Energy Loans [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	0
Financing Receivables, 30 to 89 Days Past Due [Member] \| Commercial Real Estate Buildings Land And Other Loans [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	20,272
Financing Receivables, 30 to 89 Days Past Due [Member] \| Construction Loans [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	24,535
Financing Receivables, 30 to 89 Days Past Due [Member] \| Total consumer real estate loans [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	17,659
Financing Receivables, 30 to 89 Days Past Due [Member] \| Consumer Loan [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	5,734
Financial Asset, Equal to or Greater than 90 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	53,281
Financial Asset, Equal to or Greater than 90 Days Past Due [Member] \| Commercial Portfolio Segment [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	24,640
Financial Asset, Equal to or Greater than 90 Days Past Due [Member] \| Commercial and Industrial Total Energy Loans [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	4,625
Financial Asset, Equal to or Greater than 90 Days Past Due [Member] \| Commercial Real Estate Buildings Land And Other Loans [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	14,620
Financial Asset, Equal to or Greater than 90 Days Past Due [Member] \| Construction Loans [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	0
Financial Asset, Equal to or Greater than 90 Days Past Due [Member] \| Total consumer real estate loans [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	8,819
Financial Asset, Equal to or Greater than 90 Days Past Due [Member] \| Consumer Loan [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	577
Financial Asset, Past Due
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	160,287
Financial Asset, Past Due \| Commercial Portfolio Segment [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	63,446
Financial Asset, Past Due \| Commercial and Industrial Total Energy Loans [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	4,625
Financial Asset, Past Due \| Commercial Real Estate Buildings Land And Other Loans [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	34,892
Financial Asset, Past Due \| Construction Loans [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	24,535
Financial Asset, Past Due \| Total consumer real estate loans [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	26,478
Financial Asset, Past Due \| Consumer Loan [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	6,311
Financial Asset, Not Past Due
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	19,835,469
Financial Asset, Not Past Due \| Commercial Portfolio Segment [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	6,146,733
Financial Asset, Not Past Due \| Commercial and Industrial Total Energy Loans [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	1,092,032
Financial Asset, Not Past Due \| Commercial Real Estate Buildings Land And Other Loans [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	7,462,775
Financial Asset, Not Past Due \| Construction Loans [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	1,973,010
Financial Asset, Not Past Due \| Total consumer real estate loans [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	2,714,250
Financial Asset, Not Past Due \| Consumer Loan [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	$ 446,669

Loans - Modification to Borrowe

Loans - Modification to Borrowers Experiencing Financial Difficulty (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Dec. 31, 2023
Financing Receivable, Troubled Debt Restructuring [Line Items]
Loans, net of unearned discounts	$ 19,995,756		$ 18,824,251
Combination: Payment Delay and Term Extention
Financing Receivable, Troubled Debt Restructuring [Line Items]
Loans, net of unearned discounts		$ 36,486
Financing Receivable, Modified in Period, to Total Financing Receivables, Percentage		0.20%
Commercial Portfolio Segment [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Loans, net of unearned discounts	6,210,179		5,967,182
Commercial Portfolio Segment [Member] \| Combination: Payment Delay and Term Extention
Financing Receivable, Troubled Debt Restructuring [Line Items]
Loans, net of unearned discounts	$ 27,731	$ 16,020
Financing Receivable, Modified in Period, to Total Financing Receivables, Percentage	0.40%	0.30%
Commercial Real Estate Buildings Land And Other Loans [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Loans, net of unearned discounts	$ 7,497,667		$ 7,301,920
Commercial Real Estate Buildings Land And Other Loans [Member] \| Combination: Payment Delay and Term Extention
Financing Receivable, Troubled Debt Restructuring [Line Items]
Loans, net of unearned discounts		$ 20,466
Financing Receivable, Modified in Period, to Total Financing Receivables, Percentage		0.30%

Loans - Financing Receivables,

Loans - Financing Receivables, Modified Loans Past Due in Excess of 90 Days or on Non-Accrual Status at Period-End (Details) - USD ($) $ in Thousands	Jun. 30, 2024	Dec. 31, 2023	Jun. 30, 2023
Financing Receivable, Troubled Debt Restructuring [Line Items]
Loans, net of unearned discounts	$ 19,995,756	$ 18,824,251
Combination: Payment Delay and Term Extention
Financing Receivable, Troubled Debt Restructuring [Line Items]
Loans, net of unearned discounts			$ 36,486
Combination: Payment Delay and Term Extention \| Financial Asset, Equal to or Greater than 90 Days Past Due [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Loans, net of unearned discounts	0		36,486
Commercial Portfolio Segment [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Loans, net of unearned discounts	6,210,179	5,967,182
Commercial Portfolio Segment [Member] \| Combination: Payment Delay and Term Extention
Financing Receivable, Troubled Debt Restructuring [Line Items]
Loans, net of unearned discounts	27,731		16,020
Commercial Portfolio Segment [Member] \| Combination: Payment Delay and Term Extention \| Financial Asset, Equal to or Greater than 90 Days Past Due [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Loans, net of unearned discounts	0		16,020
Commercial Real Estate Buildings Land And Other Loans [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Loans, net of unearned discounts	7,497,667	$ 7,301,920
Commercial Real Estate Buildings Land And Other Loans [Member] \| Combination: Payment Delay and Term Extention
Financing Receivable, Troubled Debt Restructuring [Line Items]
Loans, net of unearned discounts			20,466
Commercial Real Estate Buildings Land And Other Loans [Member] \| Combination: Payment Delay and Term Extention \| Financial Asset, Equal to or Greater than 90 Days Past Due [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Loans, net of unearned discounts	$ 0		$ 20,466

Loans Loans - Weighted Average

Loans Loans - Weighted Average Risk Grade for All Commercial Loans by Class and Year of Origination (Details) $ in Thousands	Jun. 30, 2024 USD ($) Grade	Dec. 31, 2023 USD ($) Grade
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Net of Deferred Income	$ 19,995,756	$ 18,824,251
Commercial Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	1,208,188
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	719,078
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	667,895
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	391,455
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	321,844
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	342,978
Financing Receivable, Revolving	2,486,421
Loans and Leases Receivable, Net of Deferred Income	$ 6,210,179	$ 5,967,182
Weighted Average Risk Grade For Loans \| Grade	6.81	6.60
Commercial and Industrial Total Energy Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	$ 304,570
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	36,014
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	55,059
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	50,104
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	4,055
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	10,415
Financing Receivable, Revolving	628,754
Loans and Leases Receivable, Net of Deferred Income	$ 1,096,657	$ 936,737
Weighted Average Risk Grade For Loans \| Grade	5.83	6.05
Commercial Real Estate Buildings Land And Other Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	$ 690,654
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	1,490,259
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	1,708,392
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	1,234,202
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	751,974
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	1,296,706
Financing Receivable, Revolving	167,257
Loans and Leases Receivable, Net of Deferred Income	$ 7,497,667	$ 7,301,920
Weighted Average Risk Grade For Loans \| Grade	7.31	7.20
Construction Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	$ 351,397
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	516,044
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	647,171
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	298,063
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	28,003
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	1,296
Financing Receivable, Revolving	155,406
Loans and Leases Receivable, Net of Deferred Income	$ 1,997,545	$ 1,680,724
Weighted Average Risk Grade For Loans \| Grade	7.75	7.45
Commercial Real Estate Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	$ 1,042,051
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	2,006,303
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	2,355,563
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	1,532,265
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	779,977
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	1,298,002
Financing Receivable, Revolving	322,663
Loans and Leases Receivable, Net of Deferred Income	$ 9,495,212	$ 8,982,644
Weighted Average Risk Grade For Loans \| Grade	7.40	7.24
Risk Grade One To Eight [Member] \| Commercial Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	$ 1,095,611
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	672,837
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	566,640
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	340,735
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	310,052
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	316,544
Financing Receivable, Revolving	2,208,140
Loans and Leases Receivable, Net of Deferred Income	$ 5,555,769	$ 5,507,878
Weighted Average Risk Grade For Loans \| Grade	6.40	6.32
Risk Grade One To Eight [Member] \| Commercial and Industrial Total Energy Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	$ 300,048
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	34,672
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	49,350
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	49,328
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	3,927
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	5,041
Financing Receivable, Revolving	597,664
Loans and Leases Receivable, Net of Deferred Income	$ 1,046,699	$ 871,221
Weighted Average Risk Grade For Loans \| Grade	5.63	5.73
Risk Grade One To Eight [Member] \| Commercial Real Estate Buildings Land And Other Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	$ 675,926
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	1,431,165
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	1,485,228
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	1,150,261
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	706,667
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	1,153,397
Financing Receivable, Revolving	119,008
Loans and Leases Receivable, Net of Deferred Income	$ 6,818,108	$ 6,895,358
Weighted Average Risk Grade For Loans \| Grade	7.05	7.03
Risk Grade One To Eight [Member] \| Construction Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	$ 247,162
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	475,920
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	575,573
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	119,299
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	28,003
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	1,296
Financing Receivable, Revolving	149,756
Loans and Leases Receivable, Net of Deferred Income	$ 1,597,174	$ 1,526,086
Weighted Average Risk Grade For Loans \| Grade	7.32	7.27
Risk Grade One To Eight [Member] \| Commercial Real Estate Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Net of Deferred Income		$ 8,421,444
Weighted Average Risk Grade For Loans \| Grade		7.07
Risk Grade Nine [Member] \| Commercial Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	$ 16,980
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	9,095
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	65,217
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	10,609
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	5,220
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	9,906
Financing Receivable, Revolving	92,920
Loans and Leases Receivable, Net of Deferred Income	$ 214,319	$ 205,244
Weighted Average Risk Grade For Loans \| Grade	9	9
Risk Grade Nine [Member] \| Commercial and Industrial Total Energy Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	$ 0
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	1,342
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	3,634
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	755
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	0
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	414
Financing Receivable, Revolving	23,888
Loans and Leases Receivable, Net of Deferred Income	$ 30,685	$ 27,643
Weighted Average Risk Grade For Loans \| Grade	9	9
Risk Grade Nine [Member] \| Commercial Real Estate Buildings Land And Other Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	$ 4,176
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	5,529
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	128,935
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	35,986
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	7,420
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	38,849
Financing Receivable, Revolving	43,689
Loans and Leases Receivable, Net of Deferred Income	$ 326,351	$ 173,470
Weighted Average Risk Grade For Loans \| Grade	9	9
Risk Grade Nine [Member] \| Construction Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	$ 90,634
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	5,282
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	26,585
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	118,546
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	0
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	0
Financing Receivable, Revolving	5,650
Loans and Leases Receivable, Net of Deferred Income	$ 246,697	$ 127,102
Weighted Average Risk Grade For Loans \| Grade	9	9
Risk Grade Nine [Member] \| Commercial Real Estate Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Net of Deferred Income		$ 300,572
Weighted Average Risk Grade For Loans \| Grade		9
Risk Grade Ten [Member] \| Commercial Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	$ 1,114
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	434
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	14,799
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	687
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	218
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	12,285
Financing Receivable, Revolving	43,049
Loans and Leases Receivable, Net of Deferred Income	$ 76,361	$ 109,254
Weighted Average Risk Grade For Loans \| Grade	10	10
Risk Grade Ten [Member] \| Commercial and Industrial Total Energy Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	$ 0
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	0
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	0
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	21
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	0
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	694
Financing Receivable, Revolving	4,100
Loans and Leases Receivable, Net of Deferred Income	$ 4,815	$ 818
Weighted Average Risk Grade For Loans \| Grade	10	10
Risk Grade Ten [Member] \| Commercial Real Estate Buildings Land And Other Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	$ 5,047
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	24,596
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	53,834
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	18,244
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	15,912
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	11,330
Financing Receivable, Revolving	1,723
Loans and Leases Receivable, Net of Deferred Income	$ 130,686	$ 96,601
Weighted Average Risk Grade For Loans \| Grade	10	10
Risk Grade Ten [Member] \| Construction Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	$ 13,601
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	34,842
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	13,513
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	49,088
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	0
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	0
Financing Receivable, Revolving	0
Loans and Leases Receivable, Net of Deferred Income	$ 111,044	$ 17,035
Weighted Average Risk Grade For Loans \| Grade	10	10
Risk Grade Ten [Member] \| Commercial Real Estate Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Net of Deferred Income		$ 113,636
Weighted Average Risk Grade For Loans \| Grade		10
Risk Grade Eleven [Member] \| Commercial Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	$ 93,737
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	32,948
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	20,080
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	36,358
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	5,840
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	2,046
Financing Receivable, Revolving	140,163
Loans and Leases Receivable, Net of Deferred Income	$ 337,401	$ 125,261
Weighted Average Risk Grade For Loans \| Grade	11	11
Risk Grade Eleven [Member] \| Commercial and Industrial Total Energy Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	$ 0
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	0
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	2,075
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	0
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	72
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	2,945
Financing Receivable, Revolving	0
Loans and Leases Receivable, Net of Deferred Income	$ 5,311	$ 25,555
Weighted Average Risk Grade For Loans \| Grade	11	11
Risk Grade Eleven [Member] \| Commercial Real Estate Buildings Land And Other Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	$ 5,177
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	8,854
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	37,368
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	24,337
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	21,975
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	91,719
Financing Receivable, Revolving	0
Loans and Leases Receivable, Net of Deferred Income	$ 189,430	$ 114,071
Weighted Average Risk Grade For Loans \| Grade	11	11
Risk Grade Eleven [Member] \| Construction Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	$ 0
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	0
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	31,500
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	11,130
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	0
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	0
Financing Receivable, Revolving	0
Loans and Leases Receivable, Net of Deferred Income	$ 42,630	$ 10,501
Weighted Average Risk Grade For Loans \| Grade	11	11
Risk Grade Eleven [Member] \| Commercial Real Estate Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Net of Deferred Income		$ 124,572
Weighted Average Risk Grade For Loans \| Grade		11
Risk Grade Twelve [Member] \| Commercial Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	$ 746
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	2,474
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	1,015
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	3,062
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	503
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	2,197
Financing Receivable, Revolving	646
Loans and Leases Receivable, Net of Deferred Income	$ 20,301	$ 17,102
Weighted Average Risk Grade For Loans \| Grade	12	12
Risk Grade Twelve [Member] \| Commercial and Industrial Total Energy Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	$ 4,522
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	0
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	0
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	0
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	56
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	1,321
Financing Receivable, Revolving	402
Loans and Leases Receivable, Net of Deferred Income	$ 6,447	$ 8,800
Weighted Average Risk Grade For Loans \| Grade	12	12
Risk Grade Twelve [Member] \| Commercial Real Estate Buildings Land And Other Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	$ 328
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	15,965
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	3,027
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	5,152
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	0
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	1,411
Financing Receivable, Revolving	2,593
Loans and Leases Receivable, Net of Deferred Income	$ 28,476	$ 19,770
Weighted Average Risk Grade For Loans \| Grade	12	12
Risk Grade Twelve [Member] \| Construction Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	$ 0
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	0
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	0
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	0
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	0
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	0
Financing Receivable, Revolving	0
Loans and Leases Receivable, Net of Deferred Income	$ 0	$ 0
Weighted Average Risk Grade For Loans \| Grade	12	12
Risk Grade Twelve [Member] \| Commercial Real Estate Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Net of Deferred Income		$ 19,770
Weighted Average Risk Grade For Loans \| Grade		12
Risk Grade Thirteen [Member] \| Commercial Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	$ 0
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	1,290
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	144
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	4
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	11
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	0
Financing Receivable, Revolving	1,503
Loans and Leases Receivable, Net of Deferred Income	$ 6,028	$ 2,443
Weighted Average Risk Grade For Loans \| Grade	13	13
Risk Grade Thirteen [Member] \| Commercial and Industrial Total Energy Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	$ 0
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	0
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	0
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	0
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	0
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	0
Financing Receivable, Revolving	2,700
Loans and Leases Receivable, Net of Deferred Income	$ 2,700	$ 2,700
Weighted Average Risk Grade For Loans \| Grade	13	13
Risk Grade Thirteen [Member] \| Commercial Real Estate Buildings Land And Other Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	$ 0
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	4,150
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	0
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	222
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	0
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	0
Financing Receivable, Revolving	244
Loans and Leases Receivable, Net of Deferred Income	$ 4,616	$ 2,650
Weighted Average Risk Grade For Loans \| Grade	13	13
Risk Grade Thirteen [Member] \| Construction Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	$ 0
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	0
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	0
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	0
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	0
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	0
Financing Receivable, Revolving	0
Loans and Leases Receivable, Net of Deferred Income	$ 0	$ 0
Weighted Average Risk Grade For Loans \| Grade	13	13
Risk Grade Thirteen [Member] \| Commercial Real Estate Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Net of Deferred Income		$ 2,650
Weighted Average Risk Grade For Loans \| Grade		13
Revolving Credit Facility [Member] \| Commercial Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade For Loans \| Grade	6.53
Revolving Credit Facility [Member] \| Commercial and Industrial Total Energy Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade For Loans \| Grade	5.44
Revolving Credit Facility [Member] \| Commercial Real Estate Buildings Land And Other Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade For Loans \| Grade	8.02
Revolving Credit Facility [Member] \| Construction Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade For Loans \| Grade	7.46
Revolving Credit Facility [Member] \| Commercial Real Estate Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade For Loans \| Grade	7.75
Revolving Loans Converted to Term [Member] \| Commercial Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Revolving, Converted to Term Loan	$ 72,320
Weighted Average Risk Grade For Loans \| Grade	8.52
Revolving Loans Converted to Term [Member] \| Commercial and Industrial Total Energy Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Revolving, Converted to Term Loan	$ 7,686
Weighted Average Risk Grade For Loans \| Grade	7.32
Revolving Loans Converted to Term [Member] \| Commercial Real Estate Buildings Land And Other Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Revolving, Converted to Term Loan	$ 158,223
Weighted Average Risk Grade For Loans \| Grade	7.53
Revolving Loans Converted to Term [Member] \| Construction Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Revolving, Converted to Term Loan	$ 165
Weighted Average Risk Grade For Loans \| Grade	6.98
Revolving Loans Converted to Term [Member] \| Commercial Real Estate Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Revolving, Converted to Term Loan	$ 158,388
Weighted Average Risk Grade For Loans \| Grade	7.53
Revolving Loans Converted to Term [Member] \| Risk Grade One To Eight [Member] \| Commercial Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Revolving, Converted to Term Loan	$ 45,210
Revolving Loans Converted to Term [Member] \| Risk Grade One To Eight [Member] \| Commercial and Industrial Total Energy Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Revolving, Converted to Term Loan	6,669
Revolving Loans Converted to Term [Member] \| Risk Grade One To Eight [Member] \| Commercial Real Estate Buildings Land And Other Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Revolving, Converted to Term Loan	96,456
Revolving Loans Converted to Term [Member] \| Risk Grade One To Eight [Member] \| Construction Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Revolving, Converted to Term Loan	165
Revolving Loans Converted to Term [Member] \| Risk Grade Nine [Member] \| Commercial Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Revolving, Converted to Term Loan	4,372
Revolving Loans Converted to Term [Member] \| Risk Grade Nine [Member] \| Commercial and Industrial Total Energy Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Revolving, Converted to Term Loan	652
Revolving Loans Converted to Term [Member] \| Risk Grade Nine [Member] \| Commercial Real Estate Buildings Land And Other Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Revolving, Converted to Term Loan	61,767
Revolving Loans Converted to Term [Member] \| Risk Grade Nine [Member] \| Construction Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Revolving, Converted to Term Loan	0
Revolving Loans Converted to Term [Member] \| Risk Grade Ten [Member] \| Commercial Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Revolving, Converted to Term Loan	3,775
Revolving Loans Converted to Term [Member] \| Risk Grade Ten [Member] \| Commercial and Industrial Total Energy Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Revolving, Converted to Term Loan	0
Revolving Loans Converted to Term [Member] \| Risk Grade Ten [Member] \| Commercial Real Estate Buildings Land And Other Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Revolving, Converted to Term Loan	0
Revolving Loans Converted to Term [Member] \| Risk Grade Ten [Member] \| Construction Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Revolving, Converted to Term Loan	0
Revolving Loans Converted to Term [Member] \| Risk Grade Eleven [Member] \| Commercial Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Revolving, Converted to Term Loan	6,229
Revolving Loans Converted to Term [Member] \| Risk Grade Eleven [Member] \| Commercial and Industrial Total Energy Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Revolving, Converted to Term Loan	219
Revolving Loans Converted to Term [Member] \| Risk Grade Eleven [Member] \| Commercial Real Estate Buildings Land And Other Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Revolving, Converted to Term Loan	0
Revolving Loans Converted to Term [Member] \| Risk Grade Eleven [Member] \| Construction Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Revolving, Converted to Term Loan	0
Revolving Loans Converted to Term [Member] \| Risk Grade Twelve [Member] \| Commercial Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Revolving, Converted to Term Loan	9,658
Revolving Loans Converted to Term [Member] \| Risk Grade Twelve [Member] \| Commercial and Industrial Total Energy Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Revolving, Converted to Term Loan	146
Revolving Loans Converted to Term [Member] \| Risk Grade Twelve [Member] \| Commercial Real Estate Buildings Land And Other Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Revolving, Converted to Term Loan	0
Revolving Loans Converted to Term [Member] \| Risk Grade Twelve [Member] \| Construction Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Revolving, Converted to Term Loan	0
Revolving Loans Converted to Term [Member] \| Risk Grade Thirteen [Member] \| Commercial Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Revolving, Converted to Term Loan	3,076
Revolving Loans Converted to Term [Member] \| Risk Grade Thirteen [Member] \| Commercial and Industrial Total Energy Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Revolving, Converted to Term Loan	0
Revolving Loans Converted to Term [Member] \| Risk Grade Thirteen [Member] \| Commercial Real Estate Buildings Land And Other Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Revolving, Converted to Term Loan	0
Revolving Loans Converted to Term [Member] \| Risk Grade Thirteen [Member] \| Construction Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Revolving, Converted to Term Loan	$ 0
2024 [Member] \| Commercial Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade For Loans \| Grade	7.27
2024 [Member] \| Commercial and Industrial Total Energy Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade For Loans \| Grade	6.11
2024 [Member] \| Commercial Real Estate Buildings Land And Other Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade For Loans \| Grade	7.21
2024 [Member] \| Construction Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade For Loans \| Grade	7.68
2024 [Member] \| Commercial Real Estate Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade For Loans \| Grade	7.36
2023 [Member] \| Commercial Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade For Loans \| Grade	6.93
2023 [Member] \| Commercial and Industrial Total Energy Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade For Loans \| Grade	6.80
2023 [Member] \| Commercial Real Estate Buildings Land And Other Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade For Loans \| Grade	7.31
2023 [Member] \| Construction Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade For Loans \| Grade	7.54
2023 [Member] \| Commercial Real Estate Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade For Loans \| Grade	7.37
2022 [Member] \| Commercial Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade For Loans \| Grade	7.29
2022 [Member] \| Commercial and Industrial Total Energy Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade For Loans \| Grade	7
2022 [Member] \| Commercial Real Estate Buildings Land And Other Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade For Loans \| Grade	7.39
2022 [Member] \| Construction Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade For Loans \| Grade	7.83
2022 [Member] \| Commercial Real Estate Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade For Loans \| Grade	7.51
2021 [Member] \| Commercial Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade For Loans \| Grade	7.32
2021 [Member] \| Commercial and Industrial Total Energy Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade For Loans \| Grade	5.88
2021 [Member] \| Commercial Real Estate Buildings Land And Other Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade For Loans \| Grade	7.34
2021 [Member] \| Construction Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade For Loans \| Grade	8.70
2021 [Member] \| Commercial Real Estate Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade For Loans \| Grade	7.61
2020 [Member] \| Commercial Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade For Loans \| Grade	5.72
2020 [Member] \| Commercial and Industrial Total Energy Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade For Loans \| Grade	6.56
2020 [Member] \| Commercial Real Estate Buildings Land And Other Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade For Loans \| Grade	7.17
2020 [Member] \| Construction Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade For Loans \| Grade	2.53
2020 [Member] \| Commercial Real Estate Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade For Loans \| Grade	7
Prior Years [Member] \| Commercial Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade For Loans \| Grade	6.07
Prior Years [Member] \| Commercial and Industrial Total Energy Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade For Loans \| Grade	9
Prior Years [Member] \| Commercial Real Estate Buildings Land And Other Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade For Loans \| Grade	7.18
Prior Years [Member] \| Construction Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade For Loans \| Grade	6.81
Prior Years [Member] \| Commercial Real Estate Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade For Loans \| Grade	7.18

Loans - Weighted Average Risk G

Loans - Weighted Average Risk Grades for All Commercial Loans by Class (Detail) $ in Thousands	Jun. 30, 2024 USD ($) Grade	Dec. 31, 2023 USD ($) Grade
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Net of Deferred Income	$ 19,995,756	$ 18,824,251
Commercial Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade \| Grade	6.81	6.60
Loans and Leases Receivable, Net of Deferred Income	$ 6,210,179	$ 5,967,182
Commercial and Industrial Total Energy Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade \| Grade	5.83	6.05
Loans and Leases Receivable, Net of Deferred Income	$ 1,096,657	$ 936,737
Commercial Real Estate Buildings Land And Other Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade \| Grade	7.31	7.20
Loans and Leases Receivable, Net of Deferred Income	$ 7,497,667	$ 7,301,920
Construction Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade \| Grade	7.75	7.45
Loans and Leases Receivable, Net of Deferred Income	$ 1,997,545	$ 1,680,724
Commercial Real Estate Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade \| Grade	7.40	7.24
Loans and Leases Receivable, Net of Deferred Income	$ 9,495,212	$ 8,982,644
Risk Grade One To Eight [Member] \| Commercial Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade \| Grade	6.40	6.32
Loans and Leases Receivable, Net of Deferred Income	$ 5,555,769	$ 5,507,878
Risk Grade One To Eight [Member] \| Commercial and Industrial Total Energy Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade \| Grade	5.63	5.73
Loans and Leases Receivable, Net of Deferred Income	$ 1,046,699	$ 871,221
Risk Grade One To Eight [Member] \| Commercial Real Estate Buildings Land And Other Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade \| Grade	7.05	7.03
Loans and Leases Receivable, Net of Deferred Income	$ 6,818,108	$ 6,895,358
Risk Grade One To Eight [Member] \| Construction Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade \| Grade	7.32	7.27
Loans and Leases Receivable, Net of Deferred Income	$ 1,597,174	$ 1,526,086
Risk Grade One To Eight [Member] \| Commercial Real Estate Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade \| Grade		7.07
Loans and Leases Receivable, Net of Deferred Income		$ 8,421,444
Risk Grade Nine [Member] \| Commercial Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade \| Grade	9	9
Loans and Leases Receivable, Net of Deferred Income	$ 214,319	$ 205,244
Risk Grade Nine [Member] \| Commercial and Industrial Total Energy Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade \| Grade	9	9
Loans and Leases Receivable, Net of Deferred Income	$ 30,685	$ 27,643
Risk Grade Nine [Member] \| Commercial Real Estate Buildings Land And Other Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade \| Grade	9	9
Loans and Leases Receivable, Net of Deferred Income	$ 326,351	$ 173,470
Risk Grade Nine [Member] \| Construction Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade \| Grade	9	9
Loans and Leases Receivable, Net of Deferred Income	$ 246,697	$ 127,102
Risk Grade Nine [Member] \| Commercial Real Estate Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade \| Grade		9
Loans and Leases Receivable, Net of Deferred Income		$ 300,572
Risk Grade Ten [Member] \| Commercial Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade \| Grade	10	10
Loans and Leases Receivable, Net of Deferred Income	$ 76,361	$ 109,254
Risk Grade Ten [Member] \| Commercial and Industrial Total Energy Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade \| Grade	10	10
Loans and Leases Receivable, Net of Deferred Income	$ 4,815	$ 818
Risk Grade Ten [Member] \| Commercial Real Estate Buildings Land And Other Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade \| Grade	10	10
Loans and Leases Receivable, Net of Deferred Income	$ 130,686	$ 96,601
Risk Grade Ten [Member] \| Construction Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade \| Grade	10	10
Loans and Leases Receivable, Net of Deferred Income	$ 111,044	$ 17,035
Risk Grade Ten [Member] \| Commercial Real Estate Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade \| Grade		10
Loans and Leases Receivable, Net of Deferred Income		$ 113,636
Risk Grade Eleven [Member] \| Commercial Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade \| Grade	11	11
Loans and Leases Receivable, Net of Deferred Income	$ 337,401	$ 125,261
Risk Grade Eleven [Member] \| Commercial and Industrial Total Energy Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade \| Grade	11	11
Loans and Leases Receivable, Net of Deferred Income	$ 5,311	$ 25,555
Risk Grade Eleven [Member] \| Commercial Real Estate Buildings Land And Other Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade \| Grade	11	11
Loans and Leases Receivable, Net of Deferred Income	$ 189,430	$ 114,071
Risk Grade Eleven [Member] \| Construction Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade \| Grade	11	11
Loans and Leases Receivable, Net of Deferred Income	$ 42,630	$ 10,501
Risk Grade Eleven [Member] \| Commercial Real Estate Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade \| Grade		11
Loans and Leases Receivable, Net of Deferred Income		$ 124,572
Risk Grade Twelve [Member] \| Commercial Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade \| Grade	12	12
Loans and Leases Receivable, Net of Deferred Income	$ 20,301	$ 17,102
Risk Grade Twelve [Member] \| Commercial and Industrial Total Energy Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade \| Grade	12	12
Loans and Leases Receivable, Net of Deferred Income	$ 6,447	$ 8,800
Risk Grade Twelve [Member] \| Commercial Real Estate Buildings Land And Other Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade \| Grade	12	12
Loans and Leases Receivable, Net of Deferred Income	$ 28,476	$ 19,770
Risk Grade Twelve [Member] \| Construction Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade \| Grade	12	12
Loans and Leases Receivable, Net of Deferred Income	$ 0	$ 0
Risk Grade Twelve [Member] \| Commercial Real Estate Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade \| Grade		12
Loans and Leases Receivable, Net of Deferred Income		$ 19,770
Risk Grade Thirteen [Member] \| Commercial Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade \| Grade	13	13
Loans and Leases Receivable, Net of Deferred Income	$ 6,028	$ 2,443
Risk Grade Thirteen [Member] \| Commercial and Industrial Total Energy Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade \| Grade	13	13
Loans and Leases Receivable, Net of Deferred Income	$ 2,700	$ 2,700
Risk Grade Thirteen [Member] \| Commercial Real Estate Buildings Land And Other Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade \| Grade	13	13
Loans and Leases Receivable, Net of Deferred Income	$ 4,616	$ 2,650
Risk Grade Thirteen [Member] \| Construction Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade \| Grade	13	13
Loans and Leases Receivable, Net of Deferred Income	$ 0	$ 0
Risk Grade Thirteen [Member] \| Commercial Real Estate Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade \| Grade		13
Loans and Leases Receivable, Net of Deferred Income		$ 2,650

Loans Loans - Age Analysis of P

Loans Loans - Age Analysis of Past Due Consumer Loans,Segregated by Class and Year of Origination (Details) - USD ($) $ in Thousands	Jun. 30, 2024	Dec. 31, 2023
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Net of Deferred Income	$ 19,995,756	$ 18,824,251
Total consumer real estate loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Net of Deferred Income	2,740,728	2,460,726
Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Net of Deferred Income	452,980	$ 476,962
Financing Receivables, 30 to 89 Days Past Due [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	107,006
Financing Receivables, 30 to 89 Days Past Due [Member] \| Total consumer real estate loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	17,659
Financing Receivables, 30 to 89 Days Past Due [Member] \| Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	5,734
Financial Asset, Equal to or Greater than 90 Days Past Due [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	53,281
Financial Asset, Equal to or Greater than 90 Days Past Due [Member] \| Total consumer real estate loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	8,819
Financial Asset, Equal to or Greater than 90 Days Past Due [Member] \| Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	577
Financial Asset, Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	160,287
Financial Asset, Past Due \| Total consumer real estate loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	26,478
Financial Asset, Past Due \| Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	6,311
Financial Asset, Not Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	19,835,469
Financial Asset, Not Past Due \| Total consumer real estate loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	2,714,250
Financial Asset, Not Past Due \| Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	446,669
Revolving Credit Facility [Member] \| Total consumer real estate loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Net of Deferred Income	820,604
Revolving Credit Facility [Member] \| Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Net of Deferred Income	322,343
Revolving Credit Facility [Member] \| Financing Receivables, 30 to 89 Days Past Due [Member] \| Total consumer real estate loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	7,284
Revolving Credit Facility [Member] \| Financing Receivables, 30 to 89 Days Past Due [Member] \| Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	2,559
Revolving Credit Facility [Member] \| Financial Asset, Equal to or Greater than 90 Days Past Due [Member] \| Total consumer real estate loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	2,624
Revolving Credit Facility [Member] \| Financial Asset, Equal to or Greater than 90 Days Past Due [Member] \| Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	162
Revolving Credit Facility [Member] \| Financial Asset, Past Due \| Total consumer real estate loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	9,908
Revolving Credit Facility [Member] \| Financial Asset, Past Due \| Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	2,721
Revolving Credit Facility [Member] \| Financial Asset, Not Past Due \| Total consumer real estate loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	810,696
Revolving Credit Facility [Member] \| Financial Asset, Not Past Due \| Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	319,622
Revolving Loans Converted to Term [Member] \| Total consumer real estate loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Net of Deferred Income	11,786
Revolving Loans Converted to Term [Member] \| Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Net of Deferred Income	23,269
Revolving Loans Converted to Term [Member] \| Financing Receivables, 30 to 89 Days Past Due [Member] \| Total consumer real estate loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	402
Revolving Loans Converted to Term [Member] \| Financing Receivables, 30 to 89 Days Past Due [Member] \| Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	37
Revolving Loans Converted to Term [Member] \| Financial Asset, Equal to or Greater than 90 Days Past Due [Member] \| Total consumer real estate loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	3,717
Revolving Loans Converted to Term [Member] \| Financial Asset, Equal to or Greater than 90 Days Past Due [Member] \| Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	181
Revolving Loans Converted to Term [Member] \| Financial Asset, Past Due \| Total consumer real estate loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	4,119
Revolving Loans Converted to Term [Member] \| Financial Asset, Past Due \| Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	218
Revolving Loans Converted to Term [Member] \| Financial Asset, Not Past Due \| Total consumer real estate loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	7,667
Revolving Loans Converted to Term [Member] \| Financial Asset, Not Past Due \| Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	23,051
2024 [Member] \| Total consumer real estate loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Net of Deferred Income	314,448
2024 [Member] \| Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Net of Deferred Income	38,056
2024 [Member] \| Financing Receivables, 30 to 89 Days Past Due [Member] \| Total consumer real estate loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	158
2024 [Member] \| Financing Receivables, 30 to 89 Days Past Due [Member] \| Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	2,429
2024 [Member] \| Financial Asset, Equal to or Greater than 90 Days Past Due [Member] \| Total consumer real estate loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	0
2024 [Member] \| Financial Asset, Equal to or Greater than 90 Days Past Due [Member] \| Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	217
2024 [Member] \| Financial Asset, Past Due \| Total consumer real estate loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	158
2024 [Member] \| Financial Asset, Past Due \| Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	2,646
2024 [Member] \| Financial Asset, Not Past Due \| Total consumer real estate loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	314,290
2024 [Member] \| Financial Asset, Not Past Due \| Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	35,410
2023 [Member] \| Total consumer real estate loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Net of Deferred Income	576,940
2023 [Member] \| Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Net of Deferred Income	41,117
2023 [Member] \| Financing Receivables, 30 to 89 Days Past Due [Member] \| Total consumer real estate loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	450
2023 [Member] \| Financing Receivables, 30 to 89 Days Past Due [Member] \| Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	174
2023 [Member] \| Financial Asset, Equal to or Greater than 90 Days Past Due [Member] \| Total consumer real estate loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	565
2023 [Member] \| Financial Asset, Equal to or Greater than 90 Days Past Due [Member] \| Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	0
2023 [Member] \| Financial Asset, Past Due \| Total consumer real estate loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	1,015
2023 [Member] \| Financial Asset, Past Due \| Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	174
2023 [Member] \| Financial Asset, Not Past Due \| Total consumer real estate loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	575,925
2023 [Member] \| Financial Asset, Not Past Due \| Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	40,943
2022 [Member] \| Total consumer real estate loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Net of Deferred Income	412,184
2022 [Member] \| Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Net of Deferred Income	19,821
2022 [Member] \| Financing Receivables, 30 to 89 Days Past Due [Member] \| Total consumer real estate loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	1,396
2022 [Member] \| Financing Receivables, 30 to 89 Days Past Due [Member] \| Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	231
2022 [Member] \| Financial Asset, Equal to or Greater than 90 Days Past Due [Member] \| Total consumer real estate loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	772
2022 [Member] \| Financial Asset, Equal to or Greater than 90 Days Past Due [Member] \| Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	16
2022 [Member] \| Financial Asset, Past Due \| Total consumer real estate loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	2,168
2022 [Member] \| Financial Asset, Past Due \| Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	247
2022 [Member] \| Financial Asset, Not Past Due \| Total consumer real estate loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	410,016
2022 [Member] \| Financial Asset, Not Past Due \| Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	19,574
2021 [Member] \| Total consumer real estate loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Net of Deferred Income	266,139
2021 [Member] \| Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Net of Deferred Income	4,044
2021 [Member] \| Financing Receivables, 30 to 89 Days Past Due [Member] \| Total consumer real estate loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	2,151
2021 [Member] \| Financing Receivables, 30 to 89 Days Past Due [Member] \| Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	122
2021 [Member] \| Financial Asset, Equal to or Greater than 90 Days Past Due [Member] \| Total consumer real estate loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	309
2021 [Member] \| Financial Asset, Equal to or Greater than 90 Days Past Due [Member] \| Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	1
2021 [Member] \| Financial Asset, Past Due \| Total consumer real estate loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	2,460
2021 [Member] \| Financial Asset, Past Due \| Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	123
2021 [Member] \| Financial Asset, Not Past Due \| Total consumer real estate loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	263,679
2021 [Member] \| Financial Asset, Not Past Due \| Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	3,921
2020 [Member] \| Total consumer real estate loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Net of Deferred Income	159,269
2020 [Member] \| Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Net of Deferred Income	2,809
2020 [Member] \| Financing Receivables, 30 to 89 Days Past Due [Member] \| Total consumer real estate loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	1,005
2020 [Member] \| Financing Receivables, 30 to 89 Days Past Due [Member] \| Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	118
2020 [Member] \| Financial Asset, Equal to or Greater than 90 Days Past Due [Member] \| Total consumer real estate loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	60
2020 [Member] \| Financial Asset, Equal to or Greater than 90 Days Past Due [Member] \| Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	0
2020 [Member] \| Financial Asset, Past Due \| Total consumer real estate loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	1,065
2020 [Member] \| Financial Asset, Past Due \| Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	118
2020 [Member] \| Financial Asset, Not Past Due \| Total consumer real estate loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	158,204
2020 [Member] \| Financial Asset, Not Past Due \| Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	2,691
Prior Years [Member] \| Total consumer real estate loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Net of Deferred Income	179,358
Prior Years [Member] \| Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Net of Deferred Income	1,521
Prior Years [Member] \| Financing Receivables, 30 to 89 Days Past Due [Member] \| Total consumer real estate loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	4,813
Prior Years [Member] \| Financing Receivables, 30 to 89 Days Past Due [Member] \| Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	64
Prior Years [Member] \| Financial Asset, Equal to or Greater than 90 Days Past Due [Member] \| Total consumer real estate loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	772
Prior Years [Member] \| Financial Asset, Equal to or Greater than 90 Days Past Due [Member] \| Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	0
Prior Years [Member] \| Financial Asset, Past Due \| Total consumer real estate loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	5,585
Prior Years [Member] \| Financial Asset, Past Due \| Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	64
Prior Years [Member] \| Financial Asset, Not Past Due \| Total consumer real estate loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	173,773
Prior Years [Member] \| Financial Asset, Not Past Due \| Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	$ 1,457

Loans Loans - Revolving Loans C

Loans Loans - Revolving Loans Converted to Term (Details) - Revolving Loans Converted to Term [Member] - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Accounts, Notes, Loans and Financing Receivable [Line Items]
Remaining Revolving Loans Converted to Term During Period	$ 81,480	$ 12,512	$ 99,659	$ 28,531
Commercial Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Remaining Revolving Loans Converted to Term During Period	10,557	3,835	24,813	14,606
Commercial and Industrial Total Energy Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Remaining Revolving Loans Converted to Term During Period	604	0	646	2,567
Commercial Real Estate Buildings Land And Other Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Remaining Revolving Loans Converted to Term During Period	65,642	5,944	66,238	5,944
Construction Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Remaining Revolving Loans Converted to Term During Period	165	0	165	0
Total consumer real estate loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Remaining Revolving Loans Converted to Term During Period	971	1,064	1,703	1,743
Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Remaining Revolving Loans Converted to Term During Period	$ 3,541	$ 1,669	$ 6,094	$ 3,671

Loans Loans - Allowance for C_2

Loans Loans - Allowance for Credit Loss By Loan Class Calculated in Accordance With CECL Methodology (Details) - USD ($) $ in Thousands	Jun. 30, 2024	Mar. 31, 2024	Dec. 31, 2023	Jun. 30, 2023	Mar. 31, 2023	Dec. 31, 2022
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, Allowance for Credit Loss	$ 256,307		$ 245,996
Commercial Portfolio Segment [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, Allowance for Credit Loss	78,554	$ 75,596	74,006	$ 75,166	$ 78,465	$ 104,237
Commercial and Industrial Total Energy Loans [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, Allowance for Credit Loss	11,485	14,218	17,814	14,929	19,191	18,062
Commercial Real Estate Portfolio Segment [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, Allowance for Credit Loss	140,020	138,224	130,598	120,926	115,693	90,301
Total consumer real estate loans [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, Allowance for Credit Loss	15,707	13,857	13,538	13,035	9,708	8,004
Consumer Loan [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, Allowance for Credit Loss	10,541	8,402	10,040	9,563	8,457	7,017
Loans Receivable [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, Allowance for Credit Loss	256,307	$ 250,297	245,996	$ 233,619	$ 231,514	$ 227,621
Modeled Expected Credit Losses [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, Allowance for Credit Loss	103,662		92,573
Modeled Expected Credit Losses [Member] \| Commercial Portfolio Segment [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, Allowance for Credit Loss	56,937		50,959
Modeled Expected Credit Losses [Member] \| Commercial and Industrial Total Energy Loans [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, Allowance for Credit Loss	3,841		7,838
Modeled Expected Credit Losses [Member] \| Commercial Real Estate Portfolio Segment [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, Allowance for Credit Loss	20,961		15,443
Modeled Expected Credit Losses [Member] \| Total consumer real estate loans [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, Allowance for Credit Loss	14,508		12,364
Modeled Expected Credit Losses [Member] \| Consumer Loan [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, Allowance for Credit Loss	7,415		5,969
Q-factor adjustments [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, Allowance for Credit Loss	138,610		144,897
Q-factor adjustments [Member] \| Commercial Portfolio Segment [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, Allowance for Credit Loss	15,589		20,612
Q-factor adjustments [Member] \| Commercial and Industrial Total Energy Loans [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, Allowance for Credit Loss	4,944		7,276
Q-factor adjustments [Member] \| Commercial Real Estate Portfolio Segment [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, Allowance for Credit Loss	114,443		112,505
Q-factor adjustments [Member] \| Total consumer real estate loans [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, Allowance for Credit Loss	508		433
Q-factor adjustments [Member] \| Consumer Loan [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, Allowance for Credit Loss	3,126		4,071
Specific Valuation Allowances [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, Allowance for Credit Loss	14,035		8,526
Specific Valuation Allowances [Member] \| Commercial Portfolio Segment [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, Allowance for Credit Loss	6,028		2,435
Specific Valuation Allowances [Member] \| Commercial and Industrial Total Energy Loans [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, Allowance for Credit Loss	2,700		2,700
Specific Valuation Allowances [Member] \| Commercial Real Estate Portfolio Segment [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, Allowance for Credit Loss	4,616		2,650
Specific Valuation Allowances [Member] \| Total consumer real estate loans [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, Allowance for Credit Loss	691		741
Specific Valuation Allowances [Member] \| Consumer Loan [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, Allowance for Credit Loss	$ 0		$ 0

Loans - Activity in the Allowan

Loans - Activity in the Allowance for Credit Losses on Loans by Portfolio Segment (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning balance			$ 245,996
Ending balance	$ 256,307		256,307
Commercial Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning balance	75,596	$ 78,465	74,006	$ 104,237
Credit loss, expense (reversal)	6,936	2,404	8,928	(18,280)
Charge-offs	(4,282)	(7,136)	(6,426)	(13,316)
Recoveries	304	1,433	2,046	2,525
Net charge-offs	(3,978)	(5,703)	(4,380)	(10,791)
Ending balance	78,554	75,166	78,554	75,166
Commercial and Industrial Total Energy Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning balance	14,218	19,191	17,814	18,062
Credit loss, expense (reversal)	(3,038)	(4,433)	(6,814)	(3,467)
Charge-offs	(79)	(518)	(79)	(518)
Recoveries	384	689	564	852
Net charge-offs	305	171	485	334
Ending balance	11,485	14,929	11,485	14,929
Commercial Real Estate Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning balance	138,224	115,693	130,598	90,301
Credit loss, expense (reversal)	1,903	5,133	9,513	30,494
Charge-offs	(122)	0	(122)	0
Recoveries	15	100	31	131
Net charge-offs	(107)	100	(91)	131
Ending balance	140,020	120,926	140,020	120,926
Total consumer real estate loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning balance	13,857	9,708	13,538	8,004
Credit loss, expense (reversal)	2,175	3,822	3,981	5,105
Charge-offs	(408)	(1,080)	(2,077)	(1,330)
Recoveries	83	585	265	1,256
Net charge-offs	(325)	(495)	(1,812)	(74)
Ending balance	15,707	13,035	15,707	13,035
Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning balance	8,402	8,457	10,040	7,017
Credit loss, expense (reversal)	7,760	5,007	11,778	10,756
Charge-offs	(8,360)	(7,016)	(16,617)	(13,958)
Recoveries	2,739	3,115	5,340	5,748
Net charge-offs	(5,621)	(3,901)	(11,277)	(8,210)
Ending balance	10,541	9,563	10,541	9,563
Loans Receivable [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning balance	250,297	231,514	245,996	227,621
Credit loss, expense (reversal)	15,736	11,933	27,386	24,608
Charge-offs	(13,251)	(15,750)	(25,321)	(29,122)
Recoveries	3,525	5,922	8,246	10,512
Net charge-offs	(9,726)	(9,828)	(17,075)	(18,610)
Ending balance	$ 256,307	$ 233,619	$ 256,307	$ 233,619

Loans - Financing Receivable, G

Loans - Financing Receivable, Gross Charge-Offs By Year of Origination (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Commercial Portfolio Segment [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	$ 1,208,188		$ 1,208,188
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	719,078		719,078
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	667,895		667,895
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	391,455		391,455
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	321,844		321,844
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	342,978		342,978
Financing Receivable, Revolving	2,486,421		2,486,421
Financing Receivable, Allowance for Credit Loss, Writeoff	4,282	$ 7,136	6,426	$ 13,316
Commercial and Industrial Total Energy Loans [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	304,570		304,570
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	36,014		36,014
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	55,059		55,059
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	50,104		50,104
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	4,055		4,055
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	10,415		10,415
Financing Receivable, Revolving	628,754		628,754
Financing Receivable, Allowance for Credit Loss, Writeoff	79	518	79	518
Commercial Real Estate Buildings Land And Other Loans [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	690,654		690,654
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	1,490,259		1,490,259
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	1,708,392		1,708,392
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	1,234,202		1,234,202
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	751,974		751,974
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	1,296,706		1,296,706
Financing Receivable, Revolving	167,257		167,257
Financing Receivable, Allowance for Credit Loss, Writeoff			122
Construction Loans [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	351,397		351,397
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	516,044		516,044
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	647,171		647,171
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	298,063		298,063
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	28,003		28,003
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	1,296		1,296
Financing Receivable, Revolving	155,406		155,406
Financing Receivable, Allowance for Credit Loss, Writeoff			0
Total consumer real estate loans [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, Allowance for Credit Loss, Writeoff	408	1,080	2,077	1,330
Consumer Loan [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, Allowance for Credit Loss, Writeoff	8,360	7,016	16,617	13,958
Loans Receivable [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, Allowance for Credit Loss, Writeoff	13,251	$ 15,750	25,321	$ 29,122
Nonperforming Financial Instruments [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	5,596		5,596
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	23,879		23,879
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	4,186		4,186
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	8,440		8,440
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	570		570
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	11,348		11,348
Financing Receivable, Revolving	8,088		8,088
Financing Receivable, Revolving, Converted to Term Loan	12,880		12,880
Nonperforming Financial Instruments [Member] \| Commercial Portfolio Segment [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	746		746
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	3,764		3,764
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	1,159		1,159
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	3,066		3,066
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	514		514
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	2,197		2,197
Financing Receivable, Revolving	2,149		2,149
Financing Receivable, Revolving, Converted to Term Loan	12,734		12,734
Nonperforming Financial Instruments [Member] \| Commercial and Industrial Total Energy Loans [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	4,522		4,522
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	0		0
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	0		0
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	0		0
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	56		56
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	1,321		1,321
Financing Receivable, Revolving	3,102		3,102
Financing Receivable, Revolving, Converted to Term Loan	146		146
Nonperforming Financial Instruments [Member] \| Commercial Real Estate Buildings Land And Other Loans [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	328		328
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	20,115		20,115
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	3,027		3,027
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	5,374		5,374
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	0		0
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	1,411		1,411
Financing Receivable, Revolving	2,837		2,837
Financing Receivable, Revolving, Converted to Term Loan	0		0
Nonperforming Financial Instruments [Member] \| Construction Loans [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	0		0
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	0		0
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	0		0
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	0		0
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	0		0
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	0		0
Financing Receivable, Revolving	0		0
Financing Receivable, Revolving, Converted to Term Loan	0		0
Nonperforming Financial Instruments [Member] \| Total consumer real estate loans [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	0		0
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	0		0
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	0		0
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	0		0
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	0		0
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	6,419		6,419
Financing Receivable, Revolving	0		0
Financing Receivable, Revolving, Converted to Term Loan	0		0
Nonperforming Financial Instruments [Member] \| Consumer Loan [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	0		0
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	0		0
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	0		0
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	0		0
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	0		0
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	0		0
Financing Receivable, Revolving	0		0
Financing Receivable, Revolving, Converted to Term Loan	0		0
Financial Asset, Other than Financial Asset Acquired with Credit Deterioration \| Nonperforming Financial Instruments [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	9,369		9,369
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	6,263		6,263
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	1,077		1,077
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	724		724
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	405		405
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	1,060		1,060
Financing Receivable, Revolving	5,459		5,459
Financing Receivable, Revolving, Converted to Term Loan	964		964
Financial Asset, Other than Financial Asset Acquired with Credit Deterioration \| Nonperforming Financial Instruments [Member] \| Commercial Portfolio Segment [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	0		0
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	471		471
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	676		676
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	467		467
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	401		401
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	625		625
Financing Receivable, Revolving	2,902		2,902
Financing Receivable, Revolving, Converted to Term Loan	884		884
Financial Asset, Other than Financial Asset Acquired with Credit Deterioration \| Nonperforming Financial Instruments [Member] \| Commercial and Industrial Total Energy Loans [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	0		0
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	79		79
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	0		0
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	0		0
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	0		0
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	0		0
Financing Receivable, Revolving	0		0
Financing Receivable, Revolving, Converted to Term Loan	0		0
Financial Asset, Other than Financial Asset Acquired with Credit Deterioration \| Nonperforming Financial Instruments [Member] \| Commercial Real Estate Buildings Land And Other Loans [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	0		0
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	0		0
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	122		122
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	0		0
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	0		0
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	0		0
Financing Receivable, Revolving	0		0
Financing Receivable, Revolving, Converted to Term Loan	0		0
Financial Asset, Other than Financial Asset Acquired with Credit Deterioration \| Nonperforming Financial Instruments [Member] \| Construction Loans [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	0		0
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	0		0
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	0		0
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	0		0
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	0		0
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	0		0
Financing Receivable, Revolving	0		0
Financing Receivable, Revolving, Converted to Term Loan	0		0
Financial Asset, Other than Financial Asset Acquired with Credit Deterioration \| Nonperforming Financial Instruments [Member] \| Total consumer real estate loans [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	0		0
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	0		0
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	148		148
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	253		253
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	0		0
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	384		384
Financing Receivable, Revolving	1,225		1,225
Financing Receivable, Revolving, Converted to Term Loan	67		67
Financial Asset, Other than Financial Asset Acquired with Credit Deterioration \| Nonperforming Financial Instruments [Member] \| Consumer Loan [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	9,369		9,369
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	5,713		5,713
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	131		131
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	4		4
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	4		4
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	51		51
Financing Receivable, Revolving	1,332		1,332
Financing Receivable, Revolving, Converted to Term Loan	$ 13		$ 13

Loans - Investment in Loans Rel

Loans - Investment in Loans Related to Allowance for Loan Losses by Portfolio Segment Disaggregated Based on Impairment Methodology (Detail) - USD ($) $ in Thousands	Jun. 30, 2024	Dec. 31, 2023
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Net of Deferred Income	$ 19,995,756	$ 18,824,251
Commercial Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Net of Deferred Income	6,210,179	5,967,182
Commercial and Industrial Total Energy Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Net of Deferred Income	1,096,657	936,737
Commercial Real Estate Buildings Land And Other Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Net of Deferred Income	7,497,667	7,301,920
Construction Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Net of Deferred Income	1,997,545	1,680,724
Total consumer real estate loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Net of Deferred Income	2,740,728	2,460,726
Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Net of Deferred Income	452,980	476,962
Specific Valuation Allowances [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Specific Allocations	14,035	8,526
Specific Valuation Allowances [Member] \| Commercial Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Specific Allocations	6,028	2,435
Specific Valuation Allowances [Member] \| Commercial and Industrial Total Energy Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Specific Allocations	2,700	2,700
Specific Valuation Allowances [Member] \| Commercial Real Estate Buildings Land And Other Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Specific Allocations	4,616	2,650
Specific Valuation Allowances [Member] \| Construction Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Specific Allocations	0	0
Specific Valuation Allowances [Member] \| Total consumer real estate loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Specific Allocations	691	741
Specific Valuation Allowances [Member] \| Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Specific Allocations	0	0
Loans Individually Evaluated for Impairment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Net of Deferred Income	72,632	58,631
Loans Individually Evaluated for Impairment [Member] \| Commercial Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Net of Deferred Income	25,508	18,670
Loans Individually Evaluated for Impairment [Member] \| Commercial and Industrial Total Energy Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Net of Deferred Income	9,001	11,353
Loans Individually Evaluated for Impairment [Member] \| Commercial Real Estate Buildings Land And Other Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Net of Deferred Income	32,316	21,373
Loans Individually Evaluated for Impairment [Member] \| Construction Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Net of Deferred Income	0	0
Loans Individually Evaluated for Impairment [Member] \| Total consumer real estate loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Net of Deferred Income	5,807	7,235
Loans Individually Evaluated for Impairment [Member] \| Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Net of Deferred Income	$ 0	$ 0

Deposits - Schedule of Deposits

Deposits - Schedule of Deposits (Detail) - USD ($) $ in Thousands	Jun. 30, 2024	Dec. 31, 2023
Deposit [Line Items]
Non-interest-bearing demand deposits	$ 13,484,977	$ 14,926,094
Interest-bearing Domestic Deposit, Savings	9,629,146	10,512,637
Interest-bearing Domestic Deposit, Money Market	10,899,993	10,997,279
Interest-bearing Domestic Deposit, Time Deposits	6,304,024	5,484,558
Total interest-bearing deposit	26,833,163	26,994,474
Total deposits	$ 40,318,140	$ 41,920,568

Deposits - Additional Informati

Deposits - Additional Information About Corporation's Deposits (Detail) - USD ($) $ in Thousands	Jun. 30, 2024	Dec. 31, 2023
Deposit Liability [Line Items]
Deposits from foreign sources (primarily Mexico)	$ 1,114,319	$ 1,061,701
Non-interest-bearing public funds deposits	13,484,977	14,926,094
Interest-bearing public funds deposits	26,833,163	26,994,474
Total deposits not covered by deposit insurance	20,774,932	22,393,786
Time deposits not covered by deposit insurance	2,721,625	2,339,716
Public Funds [Member]
Deposit Liability [Line Items]
Non-interest-bearing public funds deposits	451,472	675,016
Interest-bearing public funds deposits	$ 636,415	$ 630,455

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023	Dec. 31, 2023
Off-Balance-Sheet, Credit Loss, Liability, Change in Method, Credit Loss Expense (Reversal)			$ 1,800
Lessee, Operating Lease, Liability, Payments, Due	$ 8,900	$ 8,200	17,000	$ 16,600
Significant change in expected future minimum lease payments since year end			0
Consumer Loan [Member]
Off-Balance-Sheet, Credit Loss, Liability, Change in Method, Credit Loss Expense (Reversal)			1,600
Commercial mortgage [Member]
Off-Balance-Sheet, Credit Loss, Liability, Change in Method, Credit Loss Expense (Reversal)			211
Property, Plant and Equipment Member
Operating Lease, Right-of-Use Asset	277,200		277,200		$ 280,500
Other Liabilities [Member]
Operating Lease, Liability	$ 313,800		$ 313,800		$ 316,400

Commitments and Contingencies_2

Commitments and Contingencies - Financial Instruments with Off-Balance-Sheet Risk (Detail) - USD ($) $ in Thousands	Jun. 30, 2024	Dec. 31, 2023
Standby Letters of Credit [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Financial instruments with off- balance-sheet risk	$ 404,673	$ 438,635
Deferred Standby Letter Of Credit Fees [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Financial instruments with off- balance-sheet risk	2,614	2,912
Commitments to Extend Credit [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Financial instruments with off- balance-sheet risk	$ 11,908,533	$ 12,195,073

Commitments and Contingencies C

Commitments and Contingencies Commitments and Contingencies - Credit Losses on Off-Balance-Sheet Commitments (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Commitments and Contingencies Disclosure [Abstract]
Off-Balance Sheet, Credit Loss, Liability	$ 53,751	$ 54,918	$ 51,751	$ 58,593
Credit loss expense (benefit)	51	(2,037)	2,051	(5,712)
Off-Balance Sheet, Credit Loss, Liability	$ 53,802	$ 52,881	$ 53,802	$ 52,881

Commitments and Contingencies_3

Commitments and Contingencies Commitments and Contingencies - Components of Lease Commitments Expense (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Commitments and Contingencies Disclosure [Abstract]
Operating Lease, Right-of-Use Asset, Amortization Expense	$ 8,829	$ 8,747	$ 17,619	$ 17,512
Short-term lease expense	394	493	719	902
Non-lease components (including taxes, insurance, common maintenance, etc.)	3,466	3,662	7,015	7,043
Total operating lease expense, excluding rent	$ 12,689	$ 12,902	$ 25,353	$ 25,457

Capital and Regulatory Matter_2

Capital and Regulatory Matters - Additional Information (Detail) $ / shares in Units, $ in Thousands			3 Months Ended		6 Months Ended		12 Months Ended
	Jan. 24, 2024 USD ($)	Nov. 19, 2020 USD ($)	Jun. 30, 2024 USD ($) $ / shares shares	Jun. 30, 2023 USD ($) shares	Jun. 30, 2024 USD ($) quarter $ / shares shares	Jun. 30, 2023 USD ($) shares	Dec. 31, 2023 USD ($) $ / shares shares
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
CECL Transition Amount			$ 15,400		$ 15,400		$ 30,800
Treasury Stock, Shares, Acquired \| shares			301,094	289,149	319,287	298,332
Purchase of treasury stock (289,149 shares QTD and 298,332 shares YTD in 2023 and 7,459 shares YTD in 2022)			$ 30,153	$ 27,951	$ 32,226	$ 29,124
Maximum dividends available without prior regulatory approval			$ 1,000,000		$ 1,000,000
Maximum number of quarterly periods by which the corporation has the right to defer interest payments on junior subordinated deferrable interest debentures \| quarter					20
Series B Preferred Stock [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Preferred stock, shares issued \| shares			150,000		150,000		150,000
Preferred Stock, Aggregate Liquidation Preference, Value			$ 150,000		$ 150,000
Preferred stock, par value \| $ / shares			$ 0.01		$ 0.01		$ 0.01
Preferred Stock, Liquidation Preference Per Share \| $ / shares			$ 1,000		$ 1,000		$ 1,000
Number of Preferred Stock equivalent depositary shares \| shares			40		40
Payments of Stock Issuance Costs		$ 4,500
Proceeds from Issuance of Preferred Stock and Preference Stock		$ 145,500
Series B Preferred Stock Equivalent Depositary Shares Member
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Preferred Stock, Liquidation Preference Per Share \| $ / shares			$ 25		$ 25
Cullen/Frost [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Additional Tier 1 Capital beyond Common Equity Tier 1			$ 145,500		$ 145,500		$ 145,500
Preferred stock dividend rate percentage					4.45%		4.45%
Cullen/Frost [Member] \| Trust Preferred Securities Tier Two Capital Allowable Portion [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Trust preferred securities					$ 120,000		$ 120,000
Frost Bank [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Additional Tier 1 Capital beyond Common Equity Tier 1			0		$ 0		$ 0
prior stock repurchase plans \| Treasury Stock, Common
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Treasury Stock, Shares, Acquired \| shares							400,868
Purchase of treasury stock (289,149 shares QTD and 298,332 shares YTD in 2023 and 7,459 shares YTD in 2022)							$ 39,200
stock repurchase 2024 plan
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Stock Repurchase Program, Authorized Amount	$ 150,000
Stock Repurchase Program, Period in Force	1 year
stock repurchase 2024 plan \| Treasury Stock, Common
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Treasury Stock, Shares, Acquired \| shares					301,094
Purchase of treasury stock (289,149 shares QTD and 298,332 shares YTD in 2023 and 7,459 shares YTD in 2022)					$ 30,200
Subordinated Debt [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Permissible Percentage Decreased Each Of Final Five Years Of Term Of Notes					20%		20%
Final years of the term of the notes					5 years		5 years
Subordinated Debt [Member] \| Cullen/Frost [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Permissible portion of subordinated note included in capital			$ 40,000		$ 40,000		$ 60,000

Capital and Regulatory Matter_3

Capital and Regulatory Matters - Actual and Required Capital Ratios (Detail) - USD ($) $ in Thousands	Jun. 30, 2024	Dec. 31, 2023
Cullen/Frost [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Common Equity Tier 1 to Risk-Weighted Assets, Actual, Capital Amount	$ 4,164,990	$ 4,036,945
Common Equity Tier 1 to Risk-Weighted Assets, Actual , Ratio	13.35%	13.25%
Common Equity Tier 1 to Risk-Weighted Assets, Minimum Capital Required Plus Capital Conservation Buffer, Capital Amount	$ 2,183,331	$ 2,132,516
Common Equity Tier 1 to Risk-Weighted Assets, Minimum Capital Required Plus Capital Conservation Buffer, Ratio	7%	7%
Tier 1 Capital to Risk-Weighted Assets, Actual, Capital Amount	$ 4,310,442	$ 4,182,397
Tier 1 Capital to Risk-Weighted Assets, Actual, Ratio	13.82%	13.73%
Tier 1 Capital to Risk-Weighted Assets, Minimum Capital Required Plus Capital Conservation Buffer, Capital Amount	$ 2,651,188	$ 2,589,484
Tier 1 Capital to Risk-Weighted Assets, Minimum Capital Required Plus Capital Conservation Buffer, Ratio	8.50%	8.50%
Tier 1 Capital to Risk-Weighted Assets, Required to be Considered Well Capitalized, Capital Amount	$ 1,871,427	$ 1,827,871
Tier 1 Capital to Risk-Weighted Assets, Required to be Considered Well Capitalized, Ratio	6%	6%
Total Capital to Risk-Weighted Assets, Actual, Capital Amount	$ 4,763,514	$ 4,625,760
Total Capital to Risk-Weighted Assets, Actual, Ratio	15.27%	15.18%
Total Capital to Risk-Weighted Assets, Minimum Capital Required Plus Capital Conservation Buffer, Capital Amount	$ 3,274,997	$ 3,198,774
Total Capital to Risk-Weighted Assets, Minimum Capital Required Plus Capital Conservation Buffer, Ratio	10.50%	10.50%
Total Capital to Risk-Weighted Assets, Required to be Considered Well Capitalized, Capital Amount	$ 3,119,044	$ 3,046,452
Total Capital to Risk-Weighted Assets, Required to be Considered Well Capitalized, Ratio	10%	10%
Leverage Ratio, Actual, Capital Amount	$ 4,310,442	$ 4,182,397
Leverage Ratio, Actual, Ratio	8.62%	8.35%
Leverage Ratio, Minimum Capital Required Plus Capital Conservation Buffer, Capital Amount	$ 1,999,776	$ 2,003,020
Leverage Ratio, Minimum Capital Required Plus Capital Conservation Buffer, Ratio	4%	4%
Frost Bank [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Common Equity Tier 1 to Risk-Weighted Assets, Actual, Capital Amount	$ 4,228,311	$ 4,057,111
Common Equity Tier 1 to Risk-Weighted Assets, Actual , Ratio	13.56%	13.33%
Common Equity Tier 1 to Risk-Weighted Assets, Minimum Capital Required Plus Capital Conservation Buffer, Capital Amount	$ 2,182,110	$ 2,129,784
Common Equity Tier 1 to Risk-Weighted Assets, Minimum Capital Required Plus Capital Conservation Buffer, Ratio	7%	7%
Common Equity Tier 1 to Risk-Weighted Assets, Required To Be Considered Well Capitalized, Capital Amount	$ 2,026,245	$ 1,977,656
Common Equity Tier 1 to Risk-Weighted Assets, Required To Be Considered Well Capitalized, Ratio	6.50%	6.50%
Tier 1 Capital to Risk-Weighted Assets, Actual, Capital Amount	$ 4,228,311	$ 4,057,111
Tier 1 Capital to Risk-Weighted Assets, Actual, Ratio	13.56%	13.33%
Tier 1 Capital to Risk-Weighted Assets, Minimum Capital Required Plus Capital Conservation Buffer, Capital Amount	$ 2,649,705	$ 2,586,166
Tier 1 Capital to Risk-Weighted Assets, Minimum Capital Required Plus Capital Conservation Buffer, Ratio	8.50%	8.50%
Tier 1 Capital to Risk-Weighted Assets, Required to be Considered Well Capitalized, Capital Amount	$ 2,493,840	$ 2,434,038
Tier 1 Capital to Risk-Weighted Assets, Required to be Considered Well Capitalized, Ratio	8%	8%
Total Capital to Risk-Weighted Assets, Actual, Capital Amount	$ 4,521,383	$ 4,320,474
Total Capital to Risk-Weighted Assets, Actual, Ratio	14.50%	14.20%
Total Capital to Risk-Weighted Assets, Minimum Capital Required Plus Capital Conservation Buffer, Capital Amount	$ 3,273,165	$ 3,194,676
Total Capital to Risk-Weighted Assets, Minimum Capital Required Plus Capital Conservation Buffer, Ratio	10.50%	10.50%
Total Capital to Risk-Weighted Assets, Required to be Considered Well Capitalized, Capital Amount	$ 3,117,300	$ 3,042,548
Total Capital to Risk-Weighted Assets, Required to be Considered Well Capitalized, Ratio	10%	10%
Leverage Ratio, Actual, Capital Amount	$ 4,228,311	$ 4,057,111
Leverage Ratio, Actual, Ratio	8.46%	8.10%
Leverage Ratio, Minimum Capital Required Plus Capital Conservation Buffer, Capital Amount	$ 1,999,934	$ 2,003,152
Leverage Ratio, Minimum Capital Required Plus Capital Conservation Buffer, Ratio	4%	4%
Leverage Ratio, Required to be Considered Well Capitalized, Capital Amount	$ 2,499,918	$ 2,503,940
Leverage Ratio, Required to be Considered Well Capitalized, Ratio	5%	5%

Derivative Financial Instrume_3

Derivative Financial Instruments - Additional Information (Detail) - USD ($) $ in Thousands	Jun. 30, 2024	Dec. 31, 2023
Derivative [Line Items]
Weighted-average strike rate for outstanding interest rate caps	3.58%
Approximate credit exposure related to swaps with bank customers	$ 19,500
Interest rate swaps with upstream financial institution counterparties [Member]
Derivative [Line Items]
Approximate credit exposure related to swaps with bank customers	6,200
Not Designated as Hedging Instrument [Member] \| Financial Institution Counterparties Loan Lease Interest Rate Swaps Liabilities [Member]
Derivative [Line Items]
Estimated fair value of derivative contracts cleared through Chicago Mercantile Exchange	$ 0	$ 0

Derivative Financial Instrume_4

Derivative Financial Instruments - Schedule of Notional Amounts and Estimated Fair Values of Interest Rate Derivative Contracts Outstanding (Detail) - Non Designated as Hedging Instrument [Member] - USD ($) $ in Thousands	Jun. 30, 2024	Dec. 31, 2023
Financial institution counterparties Loan/lease interest rate swaps assets [Member]
Derivatives, Fair Value [Line Items]
Forward Contracts – Assets Notional Amount	$ 1,176,104	$ 1,040,659
Estimated Fair Value	70,070	58,486
Financial institution counterparties Loan/lease interest rate swaps liabilities [Member]
Derivatives, Fair Value [Line Items]
Forward Contracts – Liability Notional Amount	553,195	617,266
Estimated Fair Value	(7,166)	(20,293)
Financial institution counterparties Loan/lease interest-rate caps assets [Member]
Derivatives, Fair Value [Line Items]
Forward Contracts – Assets Notional Amount	235,699	275,000
Estimated Fair Value	10,021	11,747
Customer counterparties Loan/lease interest rate swaps assets [Member]
Derivatives, Fair Value [Line Items]
Forward Contracts – Assets Notional Amount	553,195	617,266
Estimated Fair Value	7,166	20,482
Customer counterparties Loan/lease interest rate swaps liabilities [Member]
Derivatives, Fair Value [Line Items]
Forward Contracts – Liability Notional Amount	1,176,104	1,040,659
Estimated Fair Value	(70,069)	(58,485)
Customer counterparties Loan/lease interest rate caps liabilities [Member]
Derivatives, Fair Value [Line Items]
Forward Contracts – Liability Notional Amount	235,699	275,000
Estimated Fair Value	$ (10,019)	$ (11,747)

Derivative Financial Instrume_5

Derivative Financial Instruments - Schedule of Weighted-Average Rates Paid and Received for Interest Rate Swaps Outstanding (Detail)	Jun. 30, 2024
Financial Institution Counterparties [Member] \| Weighted Average Interest Rate Paid [Member]
Short-duration insurance contracts, discounted liabilities [Line Items]
Non-hedging interest rate swaps – financial institution counterparties	4.98%
Financial Institution Counterparties [Member] \| Weighted-Average Interest Rate Received [Member]
Short-duration insurance contracts, discounted liabilities [Line Items]
Non-hedging interest rate swaps – financial institution counterparties	7.08%
Customer Counterparties [Member] \| Weighted Average Interest Rate Paid [Member]
Short-duration insurance contracts, discounted liabilities [Line Items]
Non-hedging interest rate swaps – customer counterparties	7.08%
Customer Counterparties [Member] \| Weighted-Average Interest Rate Received [Member]
Short-duration insurance contracts, discounted liabilities [Line Items]
Non-hedging interest rate swaps – customer counterparties	4.98%

Derivative Financial Instrume_6

Derivative Financial Instruments - Schedule of Notional Amounts and Estimated Fair Values of Commodity Derivative Positions (Detail) bbl in Thousands, MMBTU in Thousands, $ in Thousands	Jun. 30, 2024 USD ($) MMBTU bbl	Dec. 31, 2023 USD ($) MMBTU bbl
Financial Institution Counterparties [Member] \| Oil Commodity Derivative [Member]
Derivative Instruments [Line Items]
Oil/Natural Gas Derivative Assets, Notional Amount \| bbl	4,541	5,601
Oil/Natural Gas Derivative Liabilities, Notional Amount \| bbl	7,437	4,581
Oil/Natural Gas Derivative Assets, Estimated Fair Value	$ 14,580	$ 37,667
Oil/Natural Gas Derivative Liabilities, Estimated Fair Value	$ (28,552)	$ (18,500)
Financial Institution Counterparties [Member] \| Natural Gas Commodity Derivative [Member]
Derivative Instruments [Line Items]
Oil/Natural Gas Derivative Assets, Notional Amount \| MMBTU	21,934	17,363
Oil/Natural Gas Derivative Liabilities, Notional Amount \| MMBTU	10,785	6,462
Oil/Natural Gas Derivative Assets, Estimated Fair Value	$ 8,831	$ 11,822
Oil/Natural Gas Derivative Liabilities, Estimated Fair Value	$ (3,474)	$ (2,499)
Customer Counterparties [Member] \| Oil Commodity Derivative [Member]
Derivative Instruments [Line Items]
Oil/Natural Gas Derivative Assets, Notional Amount \| bbl	7,498	4,618
Oil/Natural Gas Derivative Liabilities, Notional Amount \| bbl	4,480	5,564
Oil/Natural Gas Derivative Assets, Estimated Fair Value	$ 29,330	$ 18,722
Oil/Natural Gas Derivative Liabilities, Estimated Fair Value	$ (14,315)	$ (36,877)
Customer Counterparties [Member] \| Natural Gas Commodity Derivative [Member]
Derivative Instruments [Line Items]
Oil/Natural Gas Derivative Assets, Notional Amount \| MMBTU	12,693	6,462
Oil/Natural Gas Derivative Liabilities, Notional Amount \| MMBTU	20,025	17,363
Oil/Natural Gas Derivative Assets, Estimated Fair Value	$ 3,552	$ 2,499
Oil/Natural Gas Derivative Liabilities, Estimated Fair Value	$ (8,478)	$ (11,571)

Derivative Financial Instrume_7

Derivative Financial Instruments - Schedule of Notional Amounts and Fair Values of Open Foreign Currency Forward Contracts (Details) € in Thousands, $ in Thousands, $ in Thousands	Jun. 30, 2024 USD ($)	Jun. 30, 2024 CAD ($)	Jun. 30, 2024 EUR (€)	Dec. 31, 2023 USD ($)	Dec. 31, 2023 CAD ($)	Dec. 31, 2023 EUR (€)
Financial Institution Counterparties [Member] \| GBP Foreign Exchange Forward
Derivative Instruments [Line Items]
Forward Contracts - Liability Estimated Fair Value	$ 0			$ (14)
Financial Institution Counterparties [Member] \| Foreign Exchange Forward [Member]
Derivative Instruments [Line Items]
Forward Contracts – Assets Estimated Fair Value	0			1
Forward Contracts - Liability Estimated Fair Value	0			(5)
Financial Institution Counterparties [Member] \| Other Assets [Member] \| Non Designated as Hedging Instrument [Member]
Derivative Instruments [Line Items]
Forward Contracts – Assets Notional Amount		$ 0			$ 250
Financial Institution Counterparties [Member] \| Other Liabilities [Member] \| Non Designated as Hedging Instrument [Member]
Derivative Instruments [Line Items]
Forward Contracts – Liability Notional Amount		0	€ 0		250	€ 3,000
Customer Counterparties [Member] \| GBP Foreign Exchange Forward
Derivative Instruments [Line Items]
Forward Contracts – Assets Estimated Fair Value	0			16
Customer Counterparties [Member] \| Foreign Exchange Forward [Member]
Derivative Instruments [Line Items]
Forward Contracts – Assets Estimated Fair Value	0			5
Forward Contracts - Liability Estimated Fair Value	$ 0			$ 0
Customer Counterparties [Member] \| Other Assets [Member] \| Non Designated as Hedging Instrument [Member]
Derivative Instruments [Line Items]
Forward Contracts – Assets Notional Amount		0	€ 0		250	€ 3,000
Customer Counterparties [Member] \| Other Liabilities [Member] \| Non Designated as Hedging Instrument [Member]
Derivative Instruments [Line Items]
Forward Contracts – Liability Notional Amount		$ 0			$ 250

Derivative Financial Instrume_8

Derivative Financial Instruments - Schedule of Amounts Related to Interest Rate Derivatives Designated as Hedges of Fair Value (Detail) - Designated as Hedging Instrument [Member] - Commercial Loan/Lease Interest Rate Swaps [Member] - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Interest Income on Loans [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of gain (loss) included in income	$ 0	$ 4	$ 0	$ 16
Other Non-Interest Expense [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of gain (loss) included in income	$ 0	$ 4	$ 0	$ 4

Derivative Financial Instrume_9

Derivative Financial Instruments - Schedule of Amounts Related to Non-Hedging Interest Rate and Commodity Derivatives (Detail) - Non Designated as Hedging Instrument [Member] - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Interest Rate Contract [Member] \| Other Non-Interest Income [Member]
Other Non Interest Income Non Hedging Interest Rate Derivatives [Line Items]
Amount of gain (loss) included in income (expense)	$ 512	$ 1,002	$ 1,637	$ 1,712
Interest Rate Contract [Member] \| Other Non-Interest Expense [Member]
Other Non Interest Income Non Hedging Interest Rate Derivatives [Line Items]
Amount of gain (loss) included in income (expense)	3	1	3	0
Commodity Contract [Member] \| Other Non-Interest Income [Member]
Other Non Interest Income Non Hedging Interest Rate Derivatives [Line Items]
Amount of gain (loss) included in income (expense)	946	503	1,325	925
Foreign Currency Derivative Contracts [Member] \| Other Non-Interest Income [Member]
Other Non Interest Income Non Hedging Interest Rate Derivatives [Line Items]
Amount of gain (loss) included in income (expense)	$ 0	$ 0	$ 11	$ 25

Balance Sheet Offsetting - Fina

Balance Sheet Offsetting - Financial Instruments Eligible for Offset Consolidated Balance Sheet (Detail) - USD ($) $ in Thousands	Jun. 30, 2024	Dec. 31, 2023
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Gross Amount Recognized, Derivatives, Financial Assets	$ 103,502	$ 119,723
Gross Amount Offset, Derivatives, Financial assets	0	0
Net Amount Recognized, Derivatives, Financial assets	103,502	119,723
Gross Amount Recognized, Resell agreements, Financial assets	84,650	84,650
Gross Amount Offset, Resell agreements, Financial assets	0	0
Net Amount Recognized, Resell agreements, Financial assets	84,650	84,650
Gross Amount Recognized, Financial assets	188,152	204,373
Gross Amount Offset, Financial assets	0	0
Net Amount Recognized, Financial assets	188,152	204,373
Gross Amount Recognized, Derivatives, Financial Liabilities	39,192	41,311
Gross Amount Offset, Derivatives, Financial liabilities	0	0
Net Amount Recognized, Derivatives, Financial liabilities	39,192	41,311
Gross Amount Recognized, Repurchase agreements, Financial liabilities	3,762,942	4,127,188
Gross Amount Offset, Repurchase agreements, Financial liabilities	0	0
Net Amount Recognized, Repurchase agreements, Financial liabilities	3,762,942	4,127,188
Gross Amount Recognized, Financial liabilities	3,802,134	4,168,499
Gross Amount Offset, Financial liabilities	0	0
Net Amount Recognized, Financial Liabilities	3,802,134	4,168,499
Loan/lease interest rate swaps and caps [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Gross Amount Recognized, Derivatives, Financial Assets	80,091	70,233
Gross Amount Offset, Derivatives, Financial assets	0	0
Net Amount Recognized, Derivatives, Financial assets	80,091	70,233
Gross Amount Recognized, Derivatives, Financial Liabilities	7,166	20,293
Gross Amount Offset, Derivatives, Financial liabilities	0	0
Net Amount Recognized, Derivatives, Financial liabilities	7,166	20,293
Commodity swaps and options [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Gross Amount Recognized, Derivatives, Financial Assets	23,411	49,489
Gross Amount Offset, Derivatives, Financial assets	0	0
Net Amount Recognized, Derivatives, Financial assets	23,411	49,489
Gross Amount Recognized, Derivatives, Financial Liabilities	32,026	20,999
Gross Amount Offset, Derivatives, Financial liabilities	0	0
Net Amount Recognized, Derivatives, Financial liabilities	$ 32,026	20,999
Foreign currency forward contracts [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Gross Amount Recognized, Derivatives, Financial Assets		1
Gross Amount Offset, Derivatives, Financial assets		0
Net Amount Recognized, Derivatives, Financial assets		1
Gross Amount Recognized, Derivatives, Financial Liabilities		19
Gross Amount Offset, Derivatives, Financial liabilities		0
Net Amount Recognized, Derivatives, Financial liabilities		$ 19

Balance Sheet Offsetting - Fi_2

Balance Sheet Offsetting - Financial Instruments Derivative Assets Liabilities and Resell Agreements Net of Amount Not Offset (Detail) - USD ($) $ in Thousands	Jun. 30, 2024	Dec. 31, 2023
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Net Amount Recognized, Derivatives, Financial Assets	$ 103,502	$ 119,723
Gross Amounts Not Offset, Financial Instruments, Total Derivatives, Financial Assets	(39,192)	(32,431)
Gross Amount Not Offset Collateral, Derivatives, Financial Assets	(58,123)	(84,839)
Net Amount, Derivatives, Financial Assets	6,187	2,453
Net Amount Recognized, Resell agreements, Financial Assets	84,650	84,650
Gross Amounts Not Offset Financial Instruments, Resell Agreements	0	0
Gross Amounts Not Offset Collateral, Resell Agreements, Financial Assets	(84,650)	(84,650)
Net Amount, Financial Assets, Resell Agreements	0	0
Net Amount Recognized, Total Financial Assets	188,152	204,373
Gross Amounts Not Offset Collateral, Financial Assets	(142,773)	(169,489)
Net Amount, Financial Assets	6,187	2,453
Net Amount Recognized, Derivatives, Financial Liabilities	39,192	41,311
Gross Amounts Not Offset Financial Instruments, Total Derivatives, Financial Liabilities	(39,192)	(32,431)
Gross Amounts Not Offset Collateral, Derivatives, Financial Liabilities	0	(8,580)
Net Amount, Derivatives, Financial Liabilities	0	300
Net Amount Recognized, Repurchase Agreements, Financial Liabilities	3,762,942	4,127,188
Gross Amounts Not Offset Financial Instruments, Repurchase Agreements, Financial Liabilities	0	0
Gross Amounts Not Offset Collateral, Repurchase Agreements, Financial Liabilities	(3,762,942)	(4,127,188)
Net Amount, Repurchase Agreements, Financial Liabilities	0	0
Net Amount Recognized, Total Financial Liabilities	3,802,134	4,168,499
Gross Amounts Not Offset Collateral, Financial Liabilities	(3,762,942)	(4,135,768)
Net Amount, Financial Liabilities	0	300
Counterparty H
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Net Amount Recognized, Derivatives, Financial Assets	32,594	36,551
Gross Amounts Not Offset, Financial Instruments, Total Derivatives, Financial Assets	(15,265)	(8,870)
Gross Amount Not Offset Collateral, Derivatives, Financial Assets	(16,030)	(27,170)
Net Amount, Derivatives, Financial Assets	1,299	511
Net Amount Recognized, Derivatives, Financial Liabilities	15,265	8,870
Gross Amounts Not Offset Financial Instruments, Total Derivatives, Financial Liabilities	(15,265)	(8,870)
Gross Amounts Not Offset Collateral, Derivatives, Financial Liabilities	0	0
Net Amount, Derivatives, Financial Liabilities	0	0
Counterparty F
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Net Amount Recognized, Derivatives, Financial Assets	16,299	31,202
Gross Amounts Not Offset, Financial Instruments, Total Derivatives, Financial Assets	(10,399)	(7,444)
Gross Amount Not Offset Collateral, Derivatives, Financial Assets	(3,889)	(22,954)
Net Amount, Derivatives, Financial Assets	2,011	804
Net Amount Recognized, Derivatives, Financial Liabilities	10,399	7,444
Gross Amounts Not Offset Financial Instruments, Total Derivatives, Financial Liabilities	(10,399)	(7,444)
Gross Amounts Not Offset Collateral, Derivatives, Financial Liabilities	0	0
Net Amount, Derivatives, Financial Liabilities	0	0
Counterparty B
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Net Amount Recognized, Derivatives, Financial Assets	24,125	23,829
Gross Amounts Not Offset, Financial Instruments, Total Derivatives, Financial Assets	(6,362)	(5,151)
Gross Amount Not Offset Collateral, Derivatives, Financial Assets	(16,870)	(18,472)
Net Amount, Derivatives, Financial Assets	893	206
Net Amount Recognized, Derivatives, Financial Liabilities	6,362	5,151
Gross Amounts Not Offset Financial Instruments, Total Derivatives, Financial Liabilities	(6,362)	(5,151)
Gross Amounts Not Offset Collateral, Derivatives, Financial Liabilities	0	0
Net Amount, Derivatives, Financial Liabilities	0	0
Counterparty E
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Net Amount Recognized, Derivatives, Financial Assets	15,855	13,271
Gross Amounts Not Offset, Financial Instruments, Total Derivatives, Financial Assets	(1,913)	(4,548)
Gross Amount Not Offset Collateral, Derivatives, Financial Assets	(13,040)	(8,723)
Net Amount, Derivatives, Financial Assets	902	0
Net Amount Recognized, Derivatives, Financial Liabilities	1,913	4,548
Gross Amounts Not Offset Financial Instruments, Total Derivatives, Financial Liabilities	(1,913)	(4,548)
Gross Amounts Not Offset Collateral, Derivatives, Financial Liabilities	0	0
Net Amount, Derivatives, Financial Liabilities	0	0
Other counterparties
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Net Amount Recognized, Derivatives, Financial Assets	14,629	14,870
Gross Amounts Not Offset, Financial Instruments, Total Derivatives, Financial Assets	(5,253)	(6,418)
Gross Amount Not Offset Collateral, Derivatives, Financial Assets	(8,294)	(7,520)
Net Amount, Derivatives, Financial Assets	1,082	932
Net Amount Recognized, Derivatives, Financial Liabilities	5,253	15,298
Gross Amounts Not Offset Financial Instruments, Total Derivatives, Financial Liabilities	(5,253)	(6,418)
Gross Amounts Not Offset Collateral, Derivatives, Financial Liabilities	0	(8,580)
Net Amount, Derivatives, Financial Liabilities	$ 0	$ 300

Balance Sheet Offsetting Balanc

Balance Sheet Offsetting Balance Sheet Offsetting - Remaining Contractual Maturity of the Securities Sold Under Agreement to Repurchase (Details) - USD ($) $ in Thousands	Jun. 30, 2024	Dec. 31, 2023
Remaining Contractual Maturity of the Securities Sold Under Agreement to Repurchase [Line Items]
Remaining contractual maturity of the agreements overnight and continuous	$ 3,762,942	$ 4,127,188
Remaining contractual maturity of the agreements up to 30 Days	0	0
Remaining contractual maturity of the agreements 30 to 90 Days	0	0
Remaining contractual maturity of the agreements greater than 90 Days	0	0
Remaining contractual maturity of the agreements total	3,762,942	4,127,188
Securities Sold under Agreements to Repurchase, Gross	3,762,942	4,127,188
Securities Sold under Agreements to Repurchase, Collateral, Right to Reclaim Securities	0	0
US Treasury Securities [Member]
Remaining Contractual Maturity of the Securities Sold Under Agreement to Repurchase [Line Items]
Remaining contractual maturity of the agreements overnight and continuous	1,889,019	3,300,662
Remaining contractual maturity of the agreements up to 30 Days	0	0
Remaining contractual maturity of the agreements 30 to 90 Days	0	0
Remaining contractual maturity of the agreements greater than 90 Days	0	0
Remaining contractual maturity of the agreements total	1,889,019	3,300,662
Residential Mortgage Backed Securities [Member]
Remaining Contractual Maturity of the Securities Sold Under Agreement to Repurchase [Line Items]
Remaining contractual maturity of the agreements overnight and continuous	1,873,923	826,526
Remaining contractual maturity of the agreements up to 30 Days	0	0
Remaining contractual maturity of the agreements 30 to 90 Days	0	0
Remaining contractual maturity of the agreements greater than 90 Days	0	0
Remaining contractual maturity of the agreements total	$ 1,873,923	$ 826,526

Stock-Based Compensation Stock-

Stock-Based Compensation Stock-Based Compensation - Narrative (Details) - shares	Apr. 24, 2024	Jun. 30, 2024
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-Based Compensation Arrangement by Share-Based Payment Award, Number of Shares Authorized	2,576,038
Share-Based Compensation Arrangement by Share-Based Payment Award, Number of Additional Shares Authorized	2,350,000
Performance Stock Units Outstanding
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant		2,567,893
Superseded 2015 Plan [Domain]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-Based Compensation Arrangement by Share-Based Payment Award, Number of Shares Authorized	226,038

Stock-Based Compensation - Summ

Stock-Based Compensation - Summary of Activity in Corporation's Active Stock Plans (Detail) - $ / shares	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock options exercised, Number of Shares	(38,452)	(13,626)	(122,628)	(64,013)
Deferred Stock Units Outstanding
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Beginning Balance, Number of Shares/Units			54,164
Granted, Number of Units			7,997
Stock Awards exercised/vested, Number of Shares			(9,382)
Ending Balance, Number of Shares/Units	52,779		52,779
Beginning Balance, Weighted-Average Grant-Date Fair Value			$ 89.71
Granted Weighted-Average Grant-Date Fair Value			116.84
Stock Award Exercised/Vested, Weighted Average Grant Date Fair Value			80.99
Ending Balance, Weighted-Average Grant-Date Fair Value	$ 95.37		$ 95.37
Non-Vested Restricted Stock Units Outstanding
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Beginning Balance, Number of Shares/Units			566,806
Granted, Number of Units			2,826
Stock Awards exercised/vested, Number of Shares			(458)
Forfeited/expired, Number of Shares/Units			(1,408)
Ending Balance, Number of Shares/Units	567,766		567,766
Beginning Balance, Weighted-Average Grant-Date Fair Value			$ 99.77
Granted Weighted-Average Grant-Date Fair Value			107.95
Stock Award Exercised/Vested, Weighted Average Grant Date Fair Value			65.43
Forfeited/Expired, Weighted-Average Price			106.18
Ending Balance, Weighted-Average Grant-Date Fair Value	$ 99.82		$ 99.82
Stock Options Outstanding
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Beginning Balance, Number of Shares			485,941
Stock options exercised, Number of Shares			(66,970)
Ending Balance, Number of Shares	418,971		418,971
Beginning Balance, Weighted-Average Exercise Price			$ 71.25
Stock options exercised, Weighted-Average Exercise Price			77.79
Ending Balance, Weighted-Average Exercise Price	$ 70.20		$ 70.20
Maximum [Member] \| Performance Stock Units Outstanding
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Beginning Balance, Number of Shares/Units			267,054
Stock Awards exercised/vested, Number of Shares			(45,818)
Forfeited/expired, Number of Shares/Units			(22,913)
Ending Balance, Number of Shares/Units	198,323		198,323
Beginning Balance, Weighted-Average Grant-Date Fair Value			$ 89.99
Stock Award Exercised/Vested, Weighted Average Grant Date Fair Value			57.89
Forfeited/Expired, Weighted-Average Price			57.89
Ending Balance, Weighted-Average Grant-Date Fair Value	$ 101.12		$ 101.12

Stock-Based Compensation - Shar

Stock-Based Compensation - Shares Issued in Connection with Stock Compensation Awards (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Share-Based Payment Arrangement [Abstract]
New shares issued from available authorized shares	0	0	0	49,887
Shares issued from available treasury stock	38,452	13,626	122,628	14,126
Proceeds from stock option exercises	$ 2,294	$ 946	$ 5,209	$ 2,446

Stock-Based Compensation - Stoc

Stock-Based Compensation - Stock-Based Compensation Expense (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Payment Arrangement, Expense	$ 4,523	$ 4,793	$ 8,261	$ 9,535
Income tax benefit	846	800	1,991	1,868
Non-Vested Stock Awards/Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted Stock or Unit Expense	3,100	2,864	6,479	6,171
Deferred Stock Units Outstanding
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted Stock or Unit Expense	934	880	934	880
Performance Stock Units Outstanding
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted Stock or Unit Expense	$ 489	$ 1,049	$ 848	$ 2,484

Stock-Based Compensation - Unre

Stock-Based Compensation - Unrecognized Stock-Based Compensation Expense (Detail) $ in Thousands	Jun. 30, 2024 USD ($)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Non-vested stock units	$ 16,341
Performance stock units	7,583
Total	$ 23,924

Earnings Per Common Share - Bas

Earnings Per Common Share - Basic and Diluted Earnings Per Common Share (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Earnings Per Share [Abstract]
Net income	$ 145,499	$ 162,118	$ 281,189	$ 339,771
Less: Preferred stock dividends	1,669	1,669	3,338	3,338
Net income available to common shareholders	143,830	160,449	277,851	336,433
Less: Earnings allocated to participating securities	1,693	1,645	3,334	3,468
Distributed earnings allocated to common stock	59,108	55,783	118,188	111,789
Undistributed earnings allocated to common stock	83,029	103,021	156,329	221,176
Net earnings allocated to common stock	$ 142,137	$ 158,804	$ 274,517	$ 332,965
Weighted-average shares outstanding for basic earnings per common share	64,192,907	64,240,789	64,204,615	64,306,809
Dilutive effect of stock compensation	140,280	187,172	147,693	225,267
Weighted-average shares outstanding for diluted earnings per common share	64,333,187	64,427,961	64,352,308	64,532,076

Defined Benefit Plans Additiona

Defined Benefit Plans Additional Information (Details) $ in Thousands	6 Months Ended
	Jun. 30, 2024 USD ($)
Retirement Benefits [Abstract]
Defined Benefit Plan, Plan Assets, Contributions by Employer	$ 0
Defined Benefit Plan, Expected Future Employer Contributions, Current Fiscal Year	$ 0

Defined Benefit Plans - Net Per

Defined Benefit Plans - Net Periodic Cost (Benefit) (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Retirement Benefits [Abstract]
Expected return on plan assets, net of expenses	$ (2,412)	$ (2,740)	$ (4,823)	$ (5,480)
Interest cost on projected benefit obligation	1,661	1,746	3,323	3,492
Net amortization and deferral	419	870	837	1,740
Net periodic expense (benefit)	$ (332)	$ (124)	$ (663)	$ (248)

Income Taxes - Additional Infor

Income Taxes - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023	Dec. 31, 2023
Income Tax Disclosure [Abstract]
Deferred Tax Assets, Net	$ 386.6		$ 386.6		$ 328.3
Valuation allowance	$ 0		$ 0		$ 0
U.S. federal statutory income tax rate, percent	21%	21%	21%	21%
Unrecognized tax benefits	$ 0	$ 0	$ 0	$ 0

Income Taxes - Income Tax Expen

Income Taxes - Income Tax Expense (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Income Tax Disclosure [Abstract]
Current income tax expense	$ 32,919	$ 32,413	$ 63,236	$ 67,408
Deferred income tax expense (benefit)	(3,267)	(680)	(7,713)	(2,489)
Income tax expense, as reported	$ 29,652	$ 31,733	$ 55,523	$ 64,919
Effective tax rate	16.90%	16.40%	16.50%	16%

Other Comprehensive Income (L_3

Other Comprehensive Income (Loss) - Component of Other Comprehensive Income (Loss) (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Equity [Abstract]
Securities available for sale and transferred securities, Change in net unrealized gain/loss during the period, Before Tax Amount	$ (42,111)	$ (206,863)	$ (241,186)	$ 53,406
Securities available for sale and transferred securities, Change in net unrealized gain on securities transferred to held to maturity, Before Tax Amount	(157)	(162)	(316)	(322)
Securities available for sale and transferred securities, Reclassification adjustment for net (gains) losses included in net income, Before Tax Amount	0	(33)	0	(54)
Total securities available for sale and transferred securities, before tax amount	(42,268)	(207,058)	(241,502)	53,030
Reclassification adjustment for net amortization of actuarial gain/loss included in net income as a component of net periodic cost (benefit), before tax amount	419	870	837	1,740
Total defined-benefit post-retirement benefit plans	419	870	837	1,740
Total other comprehensive income (loss), before tax	(41,849)	(206,188)	(240,665)	54,770
Securities available for sale and transferred securities, Change in net unrealized gain/loss during the period, Tax Expense (Benefit)	(8,843)	(43,441)	(50,649)	11,215
Securities available for sale and transferred securities, Change in net unrealized gain on securities transferred to held to maturity, Tax Expense (Benefit)	(33)	(34)	(67)	(67)
Securities available for sale and transferred securities, Reclassification adjustment for net (gains) losses included in net income, Tax Expense (Benefit)	0	(7)	0	(11)
Total securities available for sale and transferred securities, Tax Expense (Benefit)	(8,876)	(43,482)	(50,716)	11,137
Reclassification adjustment for net amortization of actuarial gain/loss included in net income as a component of net periodic cost (benefit), Tax Expense (Benefit)	88	183	176	366
Total defined-benefit post-retirement benefit plans, Tax Expense (Benefit)	88	183	176	366
Total other comprehensive income (loss), Tax Expense (Benefit)	(8,788)	(43,299)	(50,540)	11,503
Securities available for sale and transferred securities, Change in net unrealized gain/loss during the period, Net of Tax	(33,268)	(163,422)	(190,537)	42,191
Securities available for sale and transferred securities, Change in net unrealized gain on securities transferred to held to maturity, Net of Tax	(124)	(128)	(249)	(255)
Securities available for sale and transferred securities, Reclassification adjustment for net (gains) losses included in net income, Net of Tax	0	(26)	0	(43)
Total securities available for sale and transferred securities, Net of Tax	(33,392)	(163,576)	(190,786)	41,893
Reclassification adjustment for net amortization of actuarial gain/lloss included in net income as a component of net periodic cost (benefit), Net of Tax	331	687	661	1,374
Total defined-benefit post-retirement benefit plans, Net of Tax Amount	331	687	661	1,374
Other comprehensive income (loss), net of tax	$ (33,061)	$ (162,889)	$ (190,125)	$ 43,267

Other Comprehensive Income - Sc

Other Comprehensive Income - Schedule of Accumulated Other Comprehensive Income, Net of Tax (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning Balance			$ (1,119,219)
Other comprehensive income (loss), net of tax	$ (33,061)	$ (162,889)	(190,125)	$ 43,267
Ending Balance	(1,309,344)		(1,309,344)
Securities Available For Sale [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning Balance			(1,094,794)	(1,313,791)
Other comprehensive income (loss) before reclassifications			(190,786)	41,936
Reclassification of amounts included in net income			0	(43)
Other comprehensive income (loss), net of tax			(190,786)	41,893
Ending Balance	(1,285,580)	(1,271,898)	(1,285,580)	(1,271,898)
Defined Benefit Plans [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning Balance			(24,425)	(34,503)
Other comprehensive income (loss) before reclassifications			0	0
Reclassification of amounts included in net income			661	1,374
Other comprehensive income (loss), net of tax			661	1,374
Ending Balance	(23,764)	(33,129)	(23,764)	(33,129)
AOCI Attributable to Parent [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning Balance			(1,119,219)	(1,348,294)
Other comprehensive income (loss) before reclassifications			(190,786)	41,936
Reclassification of amounts included in net income			661	1,331
Other comprehensive income (loss), net of tax			(190,125)	43,267
Ending Balance	$ (1,309,344)	$ (1,305,027)	$ (1,309,344)	$ (1,305,027)

Operating Segments - Additional

Operating Segments - Additional Information (Detail) - Segment	6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023
Segment Reporting [Abstract]
Number of primary operating segments	2	2

Operating Segments - Summary of

Operating Segments - Summary of Operating Results by Segment (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Segment Reporting Information [Line Items]
Interest Income (Expense), Net	$ 396,712	$ 385,266	$ 786,763	$ 785,086
Credit loss expense	15,787	9,901	29,437	19,005
Total non-interest income	111,190	103,528	222,567	208,793
Total non-interest expense	316,964	285,042	643,181	570,184
Income (loss) before income taxes	175,151	193,851	336,712	404,690
Income tax expense (benefit)	29,652	31,733	55,523	64,919
Net income (loss)	145,499	162,118	281,189	339,771
Preferred stock dividends	1,669	1,669	3,338	3,338
Net income (loss) available to common shareholders	143,830	160,449	277,851	336,433
Revenues from (expenses to) external customers	507,902	488,794	1,009,330	993,879
Bank
Segment Reporting Information [Line Items]
Interest Income (Expense), Net	398,270	385,720	790,075	785,857
Credit loss expense	15,787	9,901	29,437	19,005
Total non-interest income	62,178	57,808	128,558	121,451
Total non-interest expense	276,196	246,927	563,026	496,792
Income (loss) before income taxes	168,465	186,700	326,170	391,511
Income tax expense (benefit)	28,819	30,636	54,454	62,754
Net income (loss)	139,646	156,064	271,716	328,757
Preferred stock dividends	0	0	0	0
Net income (loss) available to common shareholders	139,646	156,064	271,716	328,757
Revenues from (expenses to) external customers	460,448	443,528	918,633	907,308
Frost Wealth Advisors [Member]
Segment Reporting Information [Line Items]
Interest Income (Expense), Net	1,907	2,090	3,576	3,744
Credit loss expense	0	0	0	0
Total non-interest income	49,489	46,147	94,915	88,185
Total non-interest expense	37,875	35,558	75,848	69,507
Income (loss) before income taxes	13,521	12,679	22,643	22,422
Income tax expense (benefit)	2,839	2,663	4,755	4,709
Net income (loss)	10,682	10,016	17,888	17,713
Preferred stock dividends	0	0	0	0
Net income (loss) available to common shareholders	10,682	10,016	17,888	17,713
Revenues from (expenses to) external customers	51,396	48,237	98,491	91,929
Non-Banks [Member]
Segment Reporting Information [Line Items]
Interest Income (Expense), Net	(3,465)	(2,544)	(6,888)	(4,515)
Credit loss expense	0	0	0	0
Total non-interest income	(477)	(427)	(906)	(843)
Total non-interest expense	2,893	2,557	4,307	3,885
Income (loss) before income taxes	(6,835)	(5,528)	(12,101)	(9,243)
Income tax expense (benefit)	(2,006)	(1,566)	(3,686)	(2,544)
Net income (loss)	(4,829)	(3,962)	(8,415)	(6,699)
Preferred stock dividends	1,669	1,669	3,338	3,338
Net income (loss) available to common shareholders	(6,498)	(5,631)	(11,753)	(10,037)
Revenues from (expenses to) external customers	$ (3,942)	$ (2,971)	$ (7,794)	$ (5,358)

Fair Value Measurements - Addit

Fair Value Measurements - Additional Information (Detail) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Dec. 31, 2023
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Non-financial assets or non-financial liabilities	$ 0	$ 0
Remeasured and reported at fair value	0	$ 0
Financial instruments using fair value measurement option	$ 0		$ 0

Fair Value Measurements - Finan

Fair Value Measurements - Financial Assets and Financial Liabilities Measured at Fair Value on Recurring Basis (Detail) - USD ($) $ in Thousands	Jun. 30, 2024	Dec. 31, 2023
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale, at estimated fair value	$ 15,197,638	$ 16,578,371
Trading account securities	32,186	31,717
Derivative assets	103,502	119,723
Derivative liabilities	39,192	41,311
Interest rate swaps, caps and floors [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	87,257	90,715
Derivative liabilities	87,254	90,525
Commodity swaps and options [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	56,293	70,710
Derivative liabilities	54,819	69,447
Foreign Exchange Forward [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets		22
Derivative liabilities		19
U.S. Treasury [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale, at estimated fair value	3,882,331	4,927,589
Trading account securities	31,400	30,265
Residential Mortgage Backed Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale, at estimated fair value	6,537,427	6,596,682
States and political subdivisions [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale, at estimated fair value	4,734,909	5,011,331
Trading account securities	786	1,452
Other [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale, at estimated fair value	42,971	42,769
Level 1 [Member] \| Foreign Exchange Forward [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets		22
Derivative liabilities		19
Level 1 [Member] \| U.S. Treasury [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale, at estimated fair value	3,882,331	4,927,589
Trading account securities	31,400	30,265
Level 2 [Member] \| Interest rate swaps, caps and floors [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	87,257	90,715
Derivative liabilities	87,254	90,525
Level 2 [Member] \| Commodity swaps and options [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	56,293	70,710
Derivative liabilities	54,819	69,447
Level 2 [Member] \| Residential Mortgage Backed Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale, at estimated fair value	6,537,427	6,596,682
Level 2 [Member] \| States and political subdivisions [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale, at estimated fair value	4,734,909	5,011,331
Trading account securities	786	1,452
Level 2 [Member] \| Other [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale, at estimated fair value	$ 42,971	$ 42,769

Fair Value Measurements - Impai

Fair Value Measurements - Impaired Loans Remeasured and Reported at Fair Value of Underlying Collateral (Detail) - USD ($) $ in Thousands	Jun. 30, 2024	Jun. 30, 2023
Level 2 [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Carrying value of impaired loans before allocations	$ 17,832	$ 19,064
Impaired Financing Receivable, Related Allowance	(1,916)	(1,300)
Loans receivable, fair value disclosure	15,916	17,764
Level 3 [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Carrying value of impaired loans before allocations	14,159	20,171
Impaired Financing Receivable, Related Allowance	(1,501)	(2,100)
Loans receivable, fair value disclosure	$ 12,658	$ 18,071

Fair Value Measurements - Estim

Fair Value Measurements - Estimated Fair Values of Financial Instruments (Detail) - USD ($) $ in Thousands	Jun. 30, 2024	Dec. 31, 2023	Jun. 30, 2023	Dec. 31, 2022
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	$ 7,144,784	$ 8,687,276	$ 7,107,336	$ 12,028,132
Securities held to maturity, net of allowance for credit losses of $310 at both June 30, 2024 and December 31, 2023	3,586,116	3,619,428
Loans, net	19,739,449	18,578,255
Deposits	40,318,140	41,920,568
Federal funds purchased	35,925	14,200
Repurchase agreements	3,762,942	4,127,188
Junior subordinated deferrable interest debentures	123,155	123,127
Subordinated notes	99,569	99,491
Carrying Amount [Member] \| Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	7,144,784	8,687,276
Securities held to maturity, net of allowance for credit losses of $310 at both June 30, 2024 and December 31, 2023	3,586,116	3,619,428
Accrued interest receivable	243,951	251,385
Deposits	40,318,140	41,920,568
Federal funds purchased	35,925	14,200
Repurchase agreements	3,762,942	4,127,188
Junior subordinated deferrable interest debentures	123,155	123,127
Subordinated notes	99,569	99,491
Accrued interest payable	66,812	61,222
Carrying Amount [Member] \| Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans, net	19,739,449	18,578,255
Estimated Fair Value [Member] \| Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	7,144,784	8,687,276
Securities held to maturity, net of allowance for credit losses of $310 at both June 30, 2024 and December 31, 2023	3,416,937	3,532,044
Accrued interest receivable	243,951	251,385
Deposits	40,303,423	41,903,580
Federal funds purchased	35,925	14,200
Repurchase agreements	3,762,942	4,127,188
Junior subordinated deferrable interest debentures	123,712	123,712
Subordinated notes	96,645	96,071
Accrued interest payable	66,812	61,222
Estimated Fair Value [Member] \| Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans, net	$ 19,241,857	$ 18,117,369