Cullen/Frost Bankers (CFR) 10-Q 25 Apr 24 2024 Q1 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - $ / shares	3 Months Ended
	Mar. 31, 2024	Apr. 18, 2024	Dec. 31, 2023
Entity Information [Line Items]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Mar. 31, 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		64,254,270
Common stock, par value	$ 0.01		$ 0.01
Amendment Flag	false
Document Fiscal Year Focus	2024
Document Fiscal Period Focus	Q1
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	Mar. 31, 2024	Dec. 31, 2023
Assets:
Cash and due from banks	$ 511,173	$ 617,569
Interest-bearing deposits	7,868,694	7,985,057
Resell agreements	84,650	84,650
Total cash and cash equivalents	8,464,517	8,687,276
Securities held to maturity, net of allowance for credit losses of $310 at both March 31, 2024 and December 31, 2023	3,600,729	3,619,428
Securities available for sale, at estimated fair value	15,181,583	16,578,371
Trading account securities	39,645	31,717
Loans, net of unearned discounts	19,388,206	18,824,251
Less: Allowance for credit losses on loans	(250,297)	(245,996)
Net loans	19,137,909	18,578,255
Premises and equipment, net	1,210,897	1,190,033
Accrued interest receivable and other assets	1,870,144	2,159,958
Total assets	49,505,424	50,845,038
Liabilities:
Non-interest-bearing demand deposits	13,754,985	14,926,094
Interest-bearing deposits	27,051,501	26,994,474
Total deposits	40,806,486	41,920,568
Federal funds purchased	41,200	14,200
Repurchase agreements	3,943,207	4,127,188
Junior subordinated deferrable interest debentures, net of unamortized issuance costs	123,141	123,127
Subordinated notes, net of unamortized issuance costs	99,530	99,491
Accrued interest payable and other liabilities	853,680	844,017
Total liabilities	45,867,244	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 March 31, 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 March 31, 2024 and December 31, 2023	644	644
Additional paid-in capital	1,059,547	1,055,809
Retained earnings	3,726,559	3,657,688
Accumulated other comprehensive income (loss), net of tax	(1,276,283)	(1,119,219)
Treasury stock, at cost; 153,312 shares at March 31, 2024 and 219,295 at December 31, 2023	(17,739)	(23,927)
Total shareholders’ equity	3,638,180	3,716,447
Total liabilities and shareholders’ equity	$ 49,505,424	$ 50,845,038

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Mar. 31, 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	153,312	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
	Mar. 31, 2024	Mar. 31, 2023
Interest income:
Loans, including fees	$ 330,540	$ 269,715
Securities:
Taxable	98,062	97,775
Tax-exempt	55,259	66,634
Interest-bearing deposits	100,361	99,245
Federal funds sold	80	758
Resell agreements	1,198	1,068
Total interest income	585,500	535,195
Interest expense:
Deposits	155,634	97,989
Federal funds purchased	444	583
Repurchase agreements	35,948	33,651
Junior subordinated deferrable interest debentures	2,259	1,988
Subordinated notes	1,164	1,164
Total interest expense	195,449	135,375
Net interest income	390,051	399,820
Credit loss expense	13,650	9,104
Net interest income after credit loss expense	376,401	390,716
Non-interest income:
Trust and investment management fees	39,085	36,144
Service charges on deposit accounts	24,795	21,879
Insurance commissions and fees	18,296	18,952
Interchange and card transaction fees	4,474	4,889
Other charges, commissions, and fees	12,060	11,704
Net gain (loss) on securities transactions	0	21
Other	12,667	11,676
Total non-interest income	111,377	105,265
Non-interest expense:
Salaries and wages	148,000	130,345
Employee benefits	35,970	33,922
Net occupancy	31,778	30,349
Technology, furniture, and equipment	34,995	32,481
Deposit insurance	14,724	6,245
Other	60,750	51,800
Total non-interest expense	326,217	285,142
Income before income taxes	161,561	210,839
Income taxes	25,871	33,186
Net income	135,690	177,653
Preferred stock dividends	1,669	1,669
Net income available to common shareholders	$ 134,021	$ 175,984
Earnings per common share:
Basic	$ 2.06	$ 2.71
Diluted	$ 2.06	$ 2.70

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Net income	$ 135,690	$ 177,653
Other comprehensive income (loss), before tax:
Change in net unrealized gain/loss on securities available for sale during the period	(199,075)	260,269
Change in net unrealized gain on securities transferred to held to maturity	(159)	(160)
Reclassification adjustment for net (gains) losses included in net income	0	(21)
Total securities available for sale and transferred securities, before tax amount	(199,234)	260,088
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)	418	870
Total defined-benefit post-retirement benefit plans	418	870
Other comprehensive income (loss), before tax	(198,816)	260,958
Deferred tax expense (benefit)	(41,752)	54,802
Other comprehensive income (loss), net of tax	(157,064)	206,156
Comprehensive income (loss)	$ (21,374)	$ 383,809

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	177,653				177,653
Other comprehensive income (loss)	206,156					206,156
Stock option exercises/stock unit conversions (84,176 shares YTD in 2024 and 50,387 shares YTD in 2023)	1,500		1	1,463	(28)		64
Stock compensation expense recognized in earnings	4,742			4,742
Purchase of treasury stock (18,193 shares YTD in 2024 and 9,183 shares YTD in 2023)	(1,173)						(1,173)
Cash dividends – preferred stock (approximately $11.13 per share which is equivalent to approximately $0.28 per depository share YTD in 2024 and 2023, respectively.)	(1,669)				(1,669)
Cash dividends – common stock ($0.92 per share YTD in 2024 and $0.87 per share YTD in 2023)	(56,636)				(56,636)
Total shareholders’ equity at end of period at Mar. 31, 2023	3,467,801	145,452	644	1,035,961	3,428,991	(1,142,138)	(1,109)
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	135,690				135,690
Other comprehensive income (loss)	(157,064)					(157,064)
Stock option exercises/stock unit conversions (84,176 shares YTD in 2024 and 50,387 shares YTD in 2023)	2,915				(5,346)		8,261
Stock compensation expense recognized in earnings	3,738			3,738
Purchase of treasury stock (18,193 shares YTD in 2024 and 9,183 shares YTD in 2023)	(2,073)						(2,073)
Cash dividends – preferred stock (approximately $11.13 per share which is equivalent to approximately $0.28 per depository share YTD in 2024 and 2023, respectively.)	(1,669)				(1,669)
Cash dividends – common stock ($0.92 per share YTD in 2024 and $0.87 per share YTD in 2023)	(59,804)				(59,804)
Total shareholders’ equity at end of period at Mar. 31, 2024	$ 3,638,180	$ 145,452	$ 644	$ 1,059,547	$ 3,726,559	$ (1,276,283)	$ (17,739)

Consolidated Statements of Ch_2

Consolidated Statements of Changes in Shareholders' Equity (Parenthetical) - $ / shares	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Statement of Stockholders' Equity [Abstract]
Stock option exercise/stock unit conversions (84,176 shares YTD in 2024 and 50,387 shares YTD during 2023)	84,176	50,387
Purchase of treasury stock (18,193 shares YTD in 2024 and 9,183 shares YTD in 2023)	18,193	9,183
Cash dividend - preferred stock (Approximately $11.13 per share YTD in 2024 and 2023, respectively)	$ 11.13	$ 11.13
Cash dividend - Preferred Stock Dividends equivalent Per depositary Share Declared ($0.28 YTD during 2024 and 2023)	0.28	0.28
Cash dividends - common stock ($0.92 per share YTD in 2024 and $0.87 per share YTD in 2023)	$ 0.92	$ 0.87

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Operating Activities:
Net income	$ 135,690	$ 177,653
Adjustments to reconcile net income to net cash from operating activities:
Credit loss expense	13,650	9,104
Deferred tax expense (benefit)	(4,446)	(1,809)
Accretion of loan discounts	(4,966)	(5,125)
Securities premium amortization (discount accretion), net	13,248	20,520
Net (gain) loss on securities transactions	0	(21)
Depreciation and amortization	20,236	18,472
Net (gain) loss on sale/write-down of assets/foreclosed assets	91	(284)
Stock-based compensation	3,738	4,742
Net tax benefit from stock-based compensation	373	342
Earnings on life insurance policies	(909)	(625)
Net change in:
Trading account securities	(3,558)	1,739
Lease right-of-use assets	6,220	4,952
Accrued interest receivable and other assets	331,765	132,345
Accrued interest payable and other liabilities	(22,698)	(193,659)
Net cash from operating activities	488,434	168,346
Investing Activities:
Securities held-to-maturity - Purchases	0	(839,794)
Securities held to maturity: Maturities, calls and principal repayments	17,692	67,311
Securities available for sale:
Purchases	(927,165)	(7,308,338)
Sales	0	884,273
Maturities, calls and principal repayments	2,134,363	6,926,125
Proceeds from sale of loans	300	0
Net change in loans	(566,638)	(334,708)
Benefits received on life insurance policies	129	212
Proceeds from sales of premises and equipment	4	1,176
Purchases of premises and equipment	(38,184)	(46,103)
Proceeds from sales of repossessed properties	0	558
Net cash from investing activities	620,501	(649,288)
Financing Activities:
Net change in deposits	(1,114,082)	(1,770,041)
Net change in short-term borrowings	(156,981)	(417,397)
Proceeds from stock option exercises	2,915	1,500
Purchase of treasury stock	(2,073)	(1,173)
Cash dividends paid on preferred stock	(1,669)	(1,669)
Cash dividends paid on common stock	(59,804)	(56,636)
Net cash from financing activities	(1,331,694)	(2,245,416)
Net change in cash and cash equivalents	(222,759)	(2,726,358)
Cash and cash equivalents at beginning of period	8,687,276	12,028,132
Cash and cash equivalents at end of period	$ 8,464,517	$ 9,301,774

Significant Accounting Policies

Significant Accounting Policies	3 Months Ended
	Mar. 31, 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 “ 202 3 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: Three Months Ended 2024 2023 Cash paid for interest $ 191,569 $ 129,207 Cash paid for income taxes — — Significant non-cash transactions: Unsettled securities transactions 26,255 303,242 Right-of-use lease assets obtained in exchange for lessee operating lease liabilities 4,097 2,879 Accounting Changes, Reclassifications and Restatements.

Securities

Securities	3 Months Ended
	Mar. 31, 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 March 31, 2024 and December 31, 2023 is presented below. Amortized Gross Gross Estimated Allowance Net March 31, 2024 Residential mortgage-backed securities $ 1,239,420 $ — $ 69,069 $ 1,170,351 $ — $ 1,239,420 States and political subdivisions 2,360,119 20,197 100,817 2,279,499 (310) 2,359,809 Other 1,500 — 34 1,466 — 1,500 Total $ 3,601,039 $ 20,197 $ 169,920 $ 3,451,316 $ (310) $ 3,600,729 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 $820.1 million and $1.0 billion at March 31, 2024 and December 31, 2023, respectively. Accrued interest receivable on held-to-maturity securities totaled $20.3 million and $40.9 million at March 31, 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 $992 thousand ($784 thousand, net of tax) at March 31, 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 March 31, 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 March 31, 2024 Aaa/AAA $ 301,620 $ 1,538,918 $ 13,648 $ 1,091 $ 1,855,277 $ — Aa/AA 498,734 — 6,108 — 504,842 — Not rated — — — — — 1,500 Total $ 800,354 $ 1,538,918 $ 19,756 $ 1,091 $ 2,360,119 $ 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 months ended March 31, 2024 and 2023. Three Months Ended 2024 2023 Beginning balance $ 310 $ 158 Credit loss expense (benefit) — 104 Ending balance $ 310 $ 262 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 March 31, 2024 and December 31, 2023 is presented below. Amortized Gross Gross Allowance Estimated March 31, 2024 U.S. Treasury $ 4,181,301 $ — $ 308,729 $ — $ 3,872,572 Residential mortgage-backed securities 7,472,195 4,796 1,004,366 — 6,472,625 States and political subdivisions 5,071,259 2,313 280,056 — 4,793,516 Other 42,870 — — — 42,870 Total $ 16,767,625 $ 7,109 $ 1,593,151 $ — $ 15,181,583 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 March 31, 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 72.4% 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 $5.9 billion and $6.1 billion at March 31, 2024 and December 31, 2023, respectively. Accrued interest receivable on available-for-sale securities totaled $78.5 million and $114.9 million at March 31, 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 March 31, 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 $ — $ — $ 3,872,572 $ 308,729 $ 3,872,572 $ 308,729 Residential mortgage-backed securities 376,347 3,974 5,633,391 1,000,392 6,009,738 1,004,366 States and political subdivisions 780,308 6,535 3,740,945 273,521 4,521,253 280,056 Total $ 1,156,655 $ 10,509 $ 13,246,908 $ 1,582,642 $ 14,403,563 $ 1,593,151 As of March 31, 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 March 31, 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 $ — $ — $ 511,806 $ 727,614 $ 1,239,420 States and political subdivisions 9,131 4,281 52,003 2,294,704 2,360,119 Other 1,500 — — — 1,500 Total $ 10,631 $ 4,281 $ 563,809 $ 3,022,318 $ 3,601,039 Estimated Fair Value Residential mortgage-backed securities $ — $ — $ 455,963 $ 714,388 $ 1,170,351 States and political subdivisions 9,092 4,268 50,260 2,215,879 2,279,499 Other 1,466 — — — 1,466 Total $ 10,558 $ 4,268 $ 506,223 $ 2,930,267 $ 3,451,316 Available For Sale Amortized Cost U. S. Treasury $ 499,348 $ 3,291,567 $ 197,882 $ 192,504 $ 4,181,301 Residential mortgage-backed securities 1,348 1,272 13,807 7,455,768 7,472,195 States and political subdivisions 228,757 234,591 848,067 3,759,844 5,071,259 Other — — — — 42,870 Total $ 729,453 $ 3,527,430 $ 1,059,756 $ 11,408,116 $ 16,767,625 Estimated Fair Value U. S. Treasury $ 486,430 $ 3,082,345 $ 164,133 $ 139,664 $ 3,872,572 Residential mortgage-backed securities 1,333 1,275 13,793 6,456,224 6,472,625 States and political subdivisions 228,134 231,649 817,088 3,516,645 4,793,516 Other — — — — 42,870 Total $ 715,897 $ 3,315,269 $ 995,014 $ 10,112,533 $ 15,181,583 Sales of Securities. Sales of available for sale securities were as follows: Three Months Ended 2024 2023 Proceeds from sales $ — $ 884,273 Gross realized gains — 4,856 Gross realized losses — (4,835) Tax (expense) benefit of securities gains/losses — (4) Premiums and Discounts . Premium amortization and discount accretion included in interest income on securities was as follows: Three Months Ended 2024 2023 Premium amortization $ (17,953) $ (25,925) Discount accretion 4,705 5,405 Net (premium amortization) discount accretion $ (13,248) $ (20,520) Trading Account Securities. Trading account securities, at estimated fair value, were as follows: March 31, December 31, U.S. Treasury $ 29,608 $ 30,265 States and political subdivisions 10,037 1,452 Total $ 39,645 $ 31,717 Net gains and losses on trading account securities were as follows: Three Months Ended 2024 2023 Net gain on sales transactions $ 1,159 $ 968 Net mark-to-market gains (losses) (19) (17) Net gain (loss) on trading account securities $ 1,140 $ 951

Loans

Loans	3 Months Ended
	Mar. 31, 2024
Receivables [Abstract]
Loans	Loans Loans were as follows: March 31, December 31, Commercial and industrial $ 6,108,136 $ 5,967,182 Energy: Production 663,436 681,568 Service 195,227 194,126 Other 79,217 61,043 Total energy 937,880 936,737 Commercial real estate: Commercial mortgages 6,980,116 6,746,709 Construction 1,772,416 1,680,724 Land 568,106 555,211 Total commercial real estate 9,320,638 8,982,644 Consumer real estate: Home equity lines of credit 810,053 792,876 Home equity loans 731,736 694,966 Home improvement loans 786,681 765,887 Other 230,200 206,997 Total consumer real estate 2,558,670 2,460,726 Total real estate 11,879,308 11,443,370 Consumer and other 462,882 476,962 Total loans $ 19,388,206 $ 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 March 31, 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 4.8% of total loans. Unfunded commitments to extend credit and standby letters of credit issued to customers in the automobile dealership industry totaled $490.9 million and $20.3 million, respectively, as of March 31, 2024, while unfunded commitments to extend credit and standby letters of credit issued to customers in the energy industry totaled $1.1 billion and $91.7 million, respectively, as of March 31, 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 March 31, 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 $425.9 million at March 31, 2024 and $416.1 million at December 31, 2023. Accrued Interest Receivable. Accrued interest receivable on loans totaled $94.0 million and $90.8 million at March 31, 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: March 31, 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 $ 25,446 $ 6,119 $ 19,545 $ 5,391 Energy 10,293 6,791 11,500 7,398 Commercial real estate: Buildings, land, and other 30,012 12,519 22,420 4,983 Construction — — — — Consumer real estate 5,764 3,533 7,442 5,160 Consumer and other — — — — Total $ 71,515 $ 28,962 $ 60,907 $ 22,932 The following table presents non-accrual loans as of March 31, 2024 by class and year of origination. 2024 2023 2022 2021 2020 Prior Revolving Loans Revolving Loans Converted to Term Total Commercial and industrial $ 11 $ 2,059 $ 394 $ 2,941 $ 935 $ 2,719 $ 2,178 $ 14,209 $ 25,446 Energy 5,268 — — — 56 1,321 3,502 146 10,293 Commercial real estate: Buildings, land, and other — 19,812 3,360 3,656 — 3,184 — — 30,012 Construction — — — — — — — — — Consumer real estate — — — — 38 2,712 — 3,014 5,764 Consumer and other — — — — — — — — — Total $ 5,279 $ 21,871 $ 3,754 $ 6,597 $ 1,029 $ 9,936 $ 5,680 $ 17,369 $ 71,515 In the table above, energy and commercial and industrial loans reported as 2024 originations as of March 31, 2024 were 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 $1.2 million for the three months ended March 31, 2024 and approximately $600 thousand for the three months ended March 31, 2023. An age analysis of past due loans (including both accruing and non-accruing loans), segregated by class of loans, as of March 31, 2024 was as follows: Loans Loans Total Current Total Accruing Commercial and industrial $ 34,328 $ 25,713 $ 60,041 $ 6,048,095 $ 6,108,136 $ 7,319 Energy 2,349 24,375 26,724 911,156 937,880 19,351 Commercial real estate: Buildings, land, and other 43,836 11,206 55,042 7,493,180 7,548,222 8,223 Construction 891 — 891 1,771,525 1,772,416 — Consumer real estate 13,913 6,442 20,355 2,538,315 2,558,670 2,954 Consumer and other 5,889 253 6,142 456,740 462,882 253 Total $ 101,206 $ 67,989 $ 169,195 $ 19,219,011 $ 19,388,206 $ 38,100 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. During the three months ended March 31, 2024, we modified one commercial and industrial loan to a borrower who was experiencing financial difficulty. The loan had an outstanding balance of $28.9 million at March 31, 2024 and the modification included a payment delay and a term extension. There were no commitments to lend additional funds to this borrower. The financial effects of this loan modification were not significant and the modification did not significantly impact our determination of the allowance for credit losses on loans during the three months ended March 31, 2024. There were no modifications to borrowers experiencing financial difficulty during the three months ended March 31, 2023. Information as of or for the three months ended March 31, 2024 and March 31, 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. March 31, 2024 March 31, 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 $ 13,644 $ — Commercial real estate: Buildings, land, and other 19,137 — $ 32,781 $ — 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 March 31, 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 $ 788,259 $ 799,207 $ 640,565 $ 413,197 $ 331,143 $ 343,646 $ 2,103,487 $ 50,085 $ 5,469,589 6.28 Risk grade 9 41,562 43,457 43,429 6,436 5,063 17,960 89,123 5,008 252,038 9.00 Risk grade 10 25,688 5,250 5,278 15,136 2,927 4,848 100,864 707 160,698 10.00 Risk grade 11 23,260 23,096 20,467 24,455 6,621 2,941 91,166 8,359 200,365 11.00 Risk grade 12 11 1,257 250 2,937 924 2,719 450 11,779 20,327 12.00 Risk grade 13 — 802 144 4 11 — 1,728 2,430 5,119 13.00 $ 878,780 $ 873,069 $ 710,133 $ 462,165 $ 346,689 $ 372,114 $ 2,386,818 $ 78,368 $ 6,108,136 6.67 W/A risk grade 6.52 6.91 7.13 7.30 5.82 6.09 6.54 8.53 6.67 Energy Risk grades 1-8 $ 222,335 $ 32,898 $ 53,057 $ 69,990 $ 4,467 $ 5,496 $ 480,392 $ 7,897 $ 876,532 5.69 Risk grade 9 — 2,353 3,814 897 — 437 17,700 54 25,255 9.00 Risk grade 10 — — — 27 — 734 1,129 — 1,890 10.00 Risk grade 11 — — 2,094 18 89 2,963 18,311 435 23,910 11.00 Risk grade 12 5,268 — — — 56 1,321 802 146 7,593 12.00 Risk grade 13 — — — — — — 2,700 — 2,700 13.00 $ 227,603 $ 35,251 $ 58,965 $ 70,932 $ 4,612 $ 10,951 $ 521,034 $ 8,532 $ 937,880 6.00 W/A risk grade 5.89 6.95 7.17 5.98 6.37 8.90 5.76 7.27 6.00 Commercial real estate: Buildings, land, other Risk grades 1-8 $ 408,058 $ 1,515,706 $ 1,569,318 $ 1,195,050 $ 726,365 $ 1,285,229 $ 128,573 $ 97,011 $ 6,925,310 7.04 Risk grade 9 613 7,036 108,049 68,104 9,145 37,054 110,533 541 341,075 9.00 Risk grade 10 — 6,048 35,944 15,690 48,851 15,918 3,709 — 126,160 10.00 Risk grade 11 58 12,277 28,800 20,214 14,200 49,260 856 — 125,665 11.00 Risk grade 12 — 15,663 3,237 3,656 — 3,184 — — 25,740 12.00 Risk grade 13 — 4,149 123 — — — — — 4,272 13.00 $ 408,729 $ 1,560,879 $ 1,745,471 $ 1,302,714 $ 798,561 $ 1,390,645 $ 243,671 $ 97,552 $ 7,548,222 7.26 W/A risk grade 7.00 7.27 7.30 7.35 7.24 7.09 8.24 6.71 7.26 Construction Risk grades 1-8 $ 227,895 $ 433,679 $ 520,522 $ 187,481 $ 28,028 $ 1,353 $ 166,140 $ — $ 1,565,098 7.29 Risk grade 9 1,499 6,358 30,611 76,103 — — 5,396 — 119,967 9.00 Risk grade 10 13,555 — 12,299 15,000 — — — — 40,854 10.00 Risk grade 11 — — 35,367 11,130 — — — — 46,497 11.00 Risk grade 12 — — — — — — — — — 12.00 Risk grade 13 — — — — — — — — — 13.00 $ 242,949 $ 440,037 $ 598,799 $ 289,714 $ 28,028 $ 1,353 $ 171,536 $ — $ 1,772,416 7.56 W/A risk grade 7.46 7.39 7.70 8.28 2.54 6.82 7.27 — 7.56 Total commercial real estate $ 651,678 $ 2,000,916 $ 2,344,270 $ 1,592,428 $ 826,589 $ 1,391,998 $ 415,207 $ 97,552 $ 9,320,638 7.32 W/A risk grade 7.17 7.30 7.40 7.52 7.08 7.09 7.84 6.71 7.32 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 March 31, 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 $ — $ 1,216 $ 1,811 $ 1,601 $ 767 $ 2,390 $ 5,159 $ 969 $ 13,913 Past due 90 or more days — 366 606 390 207 1,050 805 3,018 6,442 Total past due — 1,582 2,417 1,991 974 3,440 5,964 3,987 20,355 Current loans 111,517 580,838 423,878 272,415 164,536 184,967 792,971 7,193 2,538,315 Total $ 111,517 $ 582,420 $ 426,295 $ 274,406 $ 165,510 $ 188,407 $ 798,935 $ 11,180 $ 2,558,670 Consumer and other: Past due 30-89 days $ 2,013 $ 600 $ 200 $ 75 $ 68 $ 34 $ 2,835 $ 64 $ 5,889 Past due 90 or more days 72 — 55 — — 12 101 13 253 Total past due 2,085 600 255 75 68 46 2,936 77 6,142 Current loans 30,106 46,779 25,114 4,709 3,062 1,961 322,406 22,603 456,740 Total $ 32,191 $ 47,379 $ 25,369 $ 4,784 $ 3,130 $ 2,007 $ 325,342 $ 22,680 $ 462,882 Revolving loans that converted to term during the three months ended March 31, 2024 and 2023 were as follows: Three Months Ended March 31, 2024 2023 Commercial and industrial $ 20,972 $ 15,490 Energy 44 3,435 Commercial real estate: Buildings, land and other 3,081 — Construction — — Consumer real estate 792 707 Consumer and other 3,020 6,342 Total $ 27,909 $ 25,974 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 128.2 at March 31, 2024 and 127.1 at December 31, 2023. A higher TLI value implies more 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 March 31, 2024 and December 31, 2023. March 31, 2024 Commercial Energy Commercial Consumer Consumer Total Modeled expected credit losses $ 52,835 $ 5,471 $ 20,199 $ 12,705 $ 6,293 $ 97,503 Q-Factor and other qualitative adjustments 17,642 6,047 113,753 444 2,109 139,995 Specific allocations 5,119 2,700 4,272 708 — 12,799 Total $ 75,596 $ 14,218 $ 138,224 $ 13,857 $ 8,402 $ 250,297 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 months ended March 31, 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: March 31, 2024 Beginning balance $ 74,006 $ 17,814 $ 130,598 $ 13,538 $ 10,040 $ 245,996 Credit loss expense (benefit) 1,992 (3,776) 7,610 1,806 4,018 11,650 Charge-offs (2,144) — — (1,669) (8,257) (12,070) Recoveries 1,742 180 16 182 2,601 4,721 Net (charge-offs) recoveries (402) 180 16 (1,487) (5,656) (7,349) Ending balance $ 75,596 $ 14,218 $ 138,224 $ 13,857 $ 8,402 $ 250,297 Commercial Energy Commercial Consumer Consumer Total March 31, 2023 Beginning balance $ 104,237 $ 18,062 $ 90,301 $ 8,004 $ 7,017 $ 227,621 Credit loss expense (benefit) (20,684) 966 25,361 1,283 5,749 12,675 Charge-offs (6,180) — — (250) (6,942) (13,372) Recoveries 1,092 163 31 671 2,633 4,590 Net (charge-offs) recoveries (5,088) 163 31 421 (4,309) (8,782) Ending balance $ 78,465 $ 19,191 $ 115,693 $ 9,708 $ 8,457 $ 231,514 The following table presents year-to-date gross charge-offs by year of origination as of March 31, 2024. 2024 2023 2022 2021 2020 Prior Revolving Loans Revolving Loans Converted to Term Total Commercial and industrial $ — $ 96 $ 572 $ 439 $ 6 $ 13 $ 794 $ 224 $ 2,144 Energy — — — — — — — — — Commercial real estate: Buildings, land and other — — — — — — — — — Construction — — — — — — — — — Consumer real estate — — 148 253 — 280 921 67 1,669 Consumer and other 1,958 5,543 64 4 4 34 650 — 8,257 Total $ 1,958 $ 5,639 $ 784 $ 696 $ 10 $ 327 $ 2,365 $ 291 $ 12,070 In the table above, $2.0 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 March 31, 2024 and December 31, 2023. March 31, 2024 December 31, 2023 Loan Specific Allocations Loan Specific Allocations Commercial and industrial $ 24,743 $ 5,119 $ 18,670 $ 2,435 Energy 10,147 2,700 11,353 2,700 Commercial real estate: Buildings, land and other 29,211 4,272 21,373 2,650 Construction — — — — Consumer real estate 5,584 708 7,235 741 Consumer and other — — — — Total $ 69,685 $ 12,799 $ 58,631 $ 8,526

Deposits

Deposits	3 Months Ended
	Mar. 31, 2024
Disclosure Text Block [Abstract]
Deposits	Deposits Deposits were as follows: March 31, December 31, Non-interest-bearing demand deposits $ 13,754,985 $ 14,926,094 Interest-bearing deposits: Savings and interest checking 9,994,133 10,512,637 Money market accounts 11,072,561 10,997,279 Time accounts 5,984,807 5,484,558 Total interest-bearing deposits 27,051,501 26,994,474 Total deposits $ 40,806,486 $ 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. March 31, December 31, Deposits from foreign sources (primarily Mexico) $ 1,087,494 $ 1,061,701 Non-interest-bearing public funds deposits 442,355 675,016 Interest-bearing public funds deposits 697,824 630,455 Total deposits not covered by deposit insurance 21,378,776 22,393,786 Time deposits not covered by deposit insurance 2,606,127 2,339,716

Commitments and Contingencies

Commitments and Contingencies	3 Months Ended
	Mar. 31, 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: March 31, December 31, Commitments to extend credit $ 12,027,630 $ 12,195,073 Standby letters of credit 416,084 438,635 Deferred standby letter of credit fees 2,750 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 2024 2023 Beginning balance $ 51,751 $ 58,593 Credit loss expense (benefit) 2,000 (3,675) Ending balance $ 53,751 $ 54,918 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 2024 2023 Amortization of lease right-of-use assets $ 8,790 $ 8,765 Short-term lease expense 325 409 Non-lease components (including taxes, insurance, common maintenance, etc.) 3,549 3,381 Total $ 12,664 $ 12,555 Right-of-use lease assets totaled $278.4 million at March 31, 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 $315.0 million at March 31, 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 $8.1 million during the three months ended March 31, 2024 and $8.3 million during the three months ended March 31, 2023. 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	3 Months Ended
	Mar. 31, 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 March 31, 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 March 31, 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 March 31, 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 March 31, 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 March 31, 2024 Common Equity Tier 1 to Risk-Weighted Assets Cullen/Frost $ 4,102,330 13.41 % $ 2,140,804 7.00 % N/A N/A Frost Bank 4,146,611 13.57 2,138,279 7.00 $ 1,985,545 6.50 % Tier 1 Capital to Risk-Weighted Assets Cullen/Frost 4,247,782 13.89 2,599,548 8.50 1,834,975 6.00 Frost Bank 4,146,611 13.57 2,596,482 8.50 2,443,748 8.00 Total Capital to Risk-Weighted Assets Cullen/Frost 4,694,792 15.35 3,211,206 10.50 3,058,292 10.00 Frost Bank 4,433,621 14.51 3,207,419 10.50 3,054,685 10.00 Leverage Ratio Cullen/Frost 4,247,782 8.44 2,012,280 4.00 N/A N/A Frost Bank 4,146,611 8.24 2,011,864 4.00 2,514,830 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 March 31, 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 March 31, 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 March 31, 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 March 31, 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	3 Months Ended
	Mar. 31, 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 March 31, 2024 and December 31, 2023. March 31, 2024 December 31, 2023 Notional Estimated Notional Estimated Non-hedging interest rate derivatives: Financial institution counterparties: Loan/lease interest rate swaps – assets 1,224,589 $ 69,640 1,040,659 $ 58,486 Loan/lease interest rate swaps – liabilities 538,648 (9,899) 617,266 (20,293) Loan/lease interest rate caps – assets 243,648 11,177 275,000 11,747 Customer counterparties: Loan/lease interest rate swaps – assets 538,648 9,899 617,266 20,482 Loan/lease interest rate swaps – liabilities 1,224,589 (69,639) 1,040,659 (58,485) Loan/lease interest rate caps – liabilities 243,648 (11,177) 275,000 (11,747) The weighted-average rates paid and received for interest rate swaps outstanding at March 31, 2024 were as follows: Weighted-Average Interest Interest Interest rate swaps: Non-hedging interest rate swaps – financial institution counterparties 4.91 % 5.01 % Non-hedging interest rate swaps – customer counterparties 5.01 4.91 The weighted-average strike rate for outstanding interest rate caps was 3.56% at March 31, 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. March 31, 2024 December 31, 2023 Notional Notional Estimated Notional Estimated Financial institution counterparties: Oil – assets Barrels 3,666 $ 11,866 5,601 $ 37,667 Oil – liabilities Barrels 6,183 (29,196) 4,581 (18,500) Natural gas – assets MMBTUs 15,537 10,208 17,363 11,822 Natural gas – liabilities MMBTUs 5,593 (1,715) 6,462 (2,499) Customer counterparties: Oil – assets Barrels 6,382 29,855 4,618 18,722 Oil – liabilities Barrels 3,468 (11,656) 5,564 (36,877) Natural gas – assets MMBTUs 5,593 1,717 6,462 2,499 Natural gas – liabilities MMBTUs 15,537 (9,956) 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. March 31, 2024 December 31, 2023 Notional Notional Estimated Notional Estimated Financial institution counterparties: Forward and option contracts – assets CAD 125 $ — 250 $ 1 Forward and option contracts – liabilities EUR — — 3,000 (14) Forward and option contracts – liabilities CAD 125 — 250 (5) Customer counterparties: Forward and option contracts – assets EUR — — 3,000 16 Forward and option contracts – assets CAD 250 1 250 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 2024 2023 Commercial loan/lease interest rate swaps: Amount of gain (loss) included in interest income on loans $ — $ 12 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 2024 2023 Non-hedging interest rate derivatives: Other non-interest income $ 1,125 $ 710 Other non-interest expense — (1) Non-hedging commodity derivatives: Other non-interest income 379 422 Non-hedging foreign currency derivatives: Other non-interest income 11 25 Counterparty Credit Risk.

Balance Sheet Offsetting

Balance Sheet Offsetting	3 Months Ended
	Mar. 31, 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 March 31, 2024 is presented in the following tables. Gross Amount Gross Amount Net Amount March 31, 2024 Financial assets: Derivatives: Interest rate contracts $ 80,817 $ — $ 80,817 Commodity contracts 22,074 — 22,074 Total derivatives 102,891 — 102,891 Resell agreements 84,650 — 84,650 Total $ 187,541 $ — $ 187,541 Financial liabilities: Derivatives: Interest rate contracts $ 9,899 $ — $ 9,899 Commodity contracts 30,911 — 30,911 Total derivatives 40,810 — 40,810 Repurchase agreements 3,943,207 — 3,943,207 Total $ 3,984,017 $ — $ 3,984,017 Gross Amounts Not Offset Net Amount Financial Collateral Net March 31, 2024 Financial assets: Derivatives: Counterparty H $ 31,738 $ (12,183) $ (19,555) $ — Counterparty F 17,484 (15,966) (1,136) 382 Counterparty B 22,234 (2,775) (19,459) — Counterparty E 15,519 (2,228) (13,080) 211 Other counterparties 15,916 (7,323) (8,270) 323 Total derivatives 102,891 (40,475) (61,500) 916 Resell agreements 84,650 — (84,650) — Total $ 187,541 $ (40,475) $ (146,150) $ 916 Financial liabilities: Derivatives: Counterparty H $ 12,183 $ (12,183) $ — $ — Counterparty F 15,966 (15,966) — — Counterparty B 2,775 (2,775) — — Counterparty E 2,228 (2,228) — — Other counterparties 7,658 (7,323) (335) — Total derivatives 40,810 (40,475) (335) — Repurchase agreements 3,943,207 — (3,943,207) — Total $ 3,984,017 $ (40,475) $ (3,943,542) $ — 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 March 31, 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 March 31, 2024 Repurchase agreements: U.S. Treasury $ 2,575,020 $ — $ — $ — $ 2,575,020 Residential mortgage-backed securities 1,368,187 — — — 1,368,187 Total borrowings $ 3,943,207 $ — $ — $ — $ 3,943,207 Gross amount of recognized liabilities for repurchase agreements $ 3,943,207 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	3 Months Ended
	Mar. 31, 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. As of March 31, 2024, there were 226,288 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 — — 2,142 107.41 — — — — Exercised/vested — — (458) 65.43 (45,818) 57.89 (37,900) 76.92 Forfeited/expired — — (427) 105.40 (22,913) 57.89 — — Balance, March 31, 2024 54,164 89.71 568,063 99.82 198,323 101.12 448,041 70.77 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 2024 2023 New shares issued from available authorized shares — 49,887 Shares issued from available treasury stock 84,176 500 Proceeds from stock option exercises $ 2,915 $ 1,500 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 2024 2023 Non-vested stock units $ 3,379 $ 3,307 Performance stock units 359 1,435 Total $ 3,738 $ 4,742 Income tax benefit $ 1,145 $ 1,068 Unrecognized stock-based compensation expense at March 31, 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 $ 19,470 Performance stock units 8,072 Total $ 27,542

Earnings Per Common Share

Earnings Per Common Share	3 Months Ended
	Mar. 31, 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 2024 2023 Net income $ 135,690 $ 177,653 Less: Preferred stock dividends 1,669 1,669 Net income available to common shareholders 134,021 175,984 Less: Earnings allocated to participating securities 1,639 1,807 Net earnings allocated to common stock $ 132,382 $ 174,177 Distributed earnings allocated to common stock $ 59,080 $ 56,006 Undistributed earnings allocated to common stock 73,302 118,171 Net earnings allocated to common stock $ 132,382 $ 174,177 Weighted-average shares outstanding for basic earnings per common share 64,216,323 64,373,563 Dilutive effect of stock compensation 155,408 258,513 Weighted-average shares outstanding for diluted earnings per common share 64,371,731 64,632,076

Defined Benefit Plans

Defined Benefit Plans	3 Months Ended
	Mar. 31, 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 2024 2023 Expected return on plan assets, net of expenses $ (2,411) $ (2,740) Interest cost on projected benefit obligation 1,662 1,746 Net amortization and deferral 418 870 Net periodic expense (benefit) $ (331) $ (124) Our non-qualified defined benefit pension plan is not funded. No contributions to the qualified defined benefit pension plan were made during the three months ended March 31, 2024. We do not expect to make any contributions to the qualified defined benefit plan during the remainder of 2024.

Income Taxes

Income Taxes	3 Months Ended
	Mar. 31, 2024
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes Income tax expense was as follows: Three Months Ended 2024 2023 Current income tax expense $ 30,317 $ 34,995 Deferred income tax expense (benefit) (4,446) (1,809) Income tax expense, as reported $ 25,871 $ 33,186 Effective tax rate 16.0 % 15.7 % We had a net deferred tax asset totaling $374.5 million at March 31, 2024 and $328.3 million at December 31, 2023. No valuation allowance for deferred tax assets was recorded at March 31, 2024 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)	3 Months Ended
	Mar. 31, 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 $ (199,075) $ (41,806) $ (157,269) $ 260,269 $ 54,656 $ 205,613 Change in net unrealized gain on securities transferred to held to maturity (159) (34) (125) (160) (33) (127) Reclassification adjustment for net (gains) losses included in net income — — — (21) (4) (17) Total securities available for sale and transferred securities (199,234) (41,840) (157,394) 260,088 54,619 205,469 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) 418 88 330 870 183 687 Total defined-benefit post-retirement benefit plans 418 88 330 870 183 687 Total other comprehensive income (loss) $ (198,816) $ (41,752) $ (157,064) $ 260,958 $ 54,802 $ 206,156 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 (157,394) — (157,394) Reclassification of amounts included in net income — 330 330 Net other comprehensive income (loss) during period (157,394) 330 (157,064) Balance at March 31, 2024 $ (1,252,188) $ (24,095) $ (1,276,283) Balance at January 1, 2023 $ (1,313,791) $ (34,503) $ (1,348,294) Other comprehensive income (loss) before reclassifications 205,486 — 205,486 Reclassification of amounts included in net income (17) 687 670 Net other comprehensive income (loss) during period 205,469 687 206,156 Balance at March 31, 2023 $ (1,108,322) $ (33,816) $ (1,142,138)

Operating Segments

Operating Segments	3 Months Ended
	Mar. 31, 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: March 31, 2024 Net interest income (expense) $ 391,805 $ 1,669 $ (3,423) $ 390,051 Credit loss expense (benefit) 13,650 — — 13,650 Non-interest income 66,380 45,426 (429) 111,377 Non-interest expense 286,830 37,973 1,414 326,217 Income (loss) before income taxes 157,705 9,122 (5,266) 161,561 Income tax expense (benefit) 25,635 1,916 (1,680) 25,871 Net income (loss) 132,070 7,206 (3,586) 135,690 Preferred stock dividends — — 1,669 1,669 Net income (loss) available to common shareholders $ 132,070 $ 7,206 $ (5,255) $ 134,021 Revenues from (expenses to) external customers $ 458,185 $ 47,095 $ (3,852) $ 501,428 March 31, 2023 Net interest income (expense) $ 401,318 $ 1,654 $ (3,152) $ 399,820 Non-interest income 63,643 42,038 (416) 105,265 Non-interest expense 249,865 33,949 1,328 285,142 Income (loss) before income taxes 205,992 9,743 (4,896) 210,839 Income tax expense (benefit) 32,366 2,046 (1,226) 33,186 Net income (loss) 173,626 7,697 (3,670) 177,653 Preferred stock dividends — — 1,669 1,669 Net income (loss) available to common shareholders $ 173,626 $ 7,697 $ (5,339) $ 175,984 Revenues from (expenses to) external customers $ 464,961 $ 43,692 $ (3,568) $ 505,085

Fair Value Measurements

Fair Value Measurements	3 Months Ended
	Mar. 31, 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 March 31, 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 March 31, 2024 Securities available for sale: U.S. Treasury $ 3,872,572 $ — $ — $ 3,872,572 Residential mortgage-backed securities — 6,472,625 — 6,472,625 States and political subdivisions — 4,793,516 — 4,793,516 Other — 42,870 — 42,870 Trading account securities: U.S. Treasury 29,608 — — 29,608 States and political subdivisions — 10,037 — 10,037 Derivative assets: Interest rate swaps, caps, and floors — 90,716 — 90,716 Commodity swaps and options — 53,646 — 53,646 Foreign currency forward contracts 1 — — 1 Derivative liabilities: Interest rate swaps, caps, and floors — 90,715 — 90,715 Commodity swaps and options — 52,523 — 52,523 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. Three Months Ended Three Months Ended Level 2 Level 3 Level 2 Level 3 Carrying value before allocations $ 16,332 $ 16,182 $ 368 $ 6,242 Specific (allocations) reversals of prior allocations (1,589) (1,172) — (900) Fair value $ 14,743 $ 15,010 $ 368 $ 5,342 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: March 31, 2024 December 31, 2023 Carrying Estimated Carrying Estimated Financial assets: Level 2 inputs: Cash and cash equivalents $ 8,464,517 $ 8,464,517 $ 8,687,276 $ 8,687,276 Securities held to maturity 3,600,729 3,451,316 3,619,428 3,532,044 Accrued interest receivable 206,090 206,090 251,385 251,385 Level 3 inputs: Loans, net 19,137,909 18,637,078 18,578,255 18,117,369 Financial liabilities: Level 2 inputs: Deposits 40,806,486 40,792,337 41,920,568 41,903,580 Federal funds purchased 41,200 41,200 14,200 14,200 Repurchase agreements 3,943,207 3,943,207 4,127,188 4,127,188 Junior subordinated deferrable interest debentures 123,141 123,712 123,127 123,712 Subordinated notes 99,530 96,513 99,491 96,071 Accrued interest payable 65,102 65,102 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	3 Months Ended
	Mar. 31, 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 20 - Accounting Standards Updates in our 2023 Form 10-K for additional information related to previously issued accounting standards updates. 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
	Mar. 31, 2024	Mar. 31, 2023
Pay vs Performance Disclosure
Net income	$ 135,690	$ 177,653

Insider Trading Arrangements

Insider Trading Arrangements	3 Months Ended
	Mar. 31, 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)	3 Months Ended
	Mar. 31, 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 “ 202 3 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)	3 Months Ended
	Mar. 31, 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)	3 Months Ended
	Mar. 31, 2024
Accounting Policies [Abstract]
Additional Cash Flow Information	Additional cash flow information was as follows: Three Months Ended 2024 2023 Cash paid for interest $ 191,569 $ 129,207 Cash paid for income taxes — — Significant non-cash transactions: Unsettled securities transactions 26,255 303,242 Right-of-use lease assets obtained in exchange for lessee operating lease liabilities 4,097 2,879

Securities (Tables)

Securities (Tables)	3 Months Ended
	Mar. 31, 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 March 31, 2024 and December 31, 2023 is presented below. Amortized Gross Gross Estimated Allowance Net March 31, 2024 Residential mortgage-backed securities $ 1,239,420 $ — $ 69,069 $ 1,170,351 $ — $ 1,239,420 States and political subdivisions 2,360,119 20,197 100,817 2,279,499 (310) 2,359,809 Other 1,500 — 34 1,466 — 1,500 Total $ 3,601,039 $ 20,197 $ 169,920 $ 3,451,316 $ (310) $ 3,600,729 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 March 31, 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 March 31, 2024 Aaa/AAA $ 301,620 $ 1,538,918 $ 13,648 $ 1,091 $ 1,855,277 $ — Aa/AA 498,734 — 6,108 — 504,842 — Not rated — — — — — 1,500 Total $ 800,354 $ 1,538,918 $ 19,756 $ 1,091 $ 2,360,119 $ 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 months ended March 31, 2024 and 2023. Three Months Ended 2024 2023 Beginning balance $ 310 $ 158 Credit loss expense (benefit) — 104 Ending balance $ 310 $ 262
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 March 31, 2024 and December 31, 2023 is presented below. Amortized Gross Gross Allowance Estimated March 31, 2024 U.S. Treasury $ 4,181,301 $ — $ 308,729 $ — $ 3,872,572 Residential mortgage-backed securities 7,472,195 4,796 1,004,366 — 6,472,625 States and political subdivisions 5,071,259 2,313 280,056 — 4,793,516 Other 42,870 — — — 42,870 Total $ 16,767,625 $ 7,109 $ 1,593,151 $ — $ 15,181,583 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 March 31, 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 $ — $ — $ 3,872,572 $ 308,729 $ 3,872,572 $ 308,729 Residential mortgage-backed securities 376,347 3,974 5,633,391 1,000,392 6,009,738 1,004,366 States and political subdivisions 780,308 6,535 3,740,945 273,521 4,521,253 280,056 Total $ 1,156,655 $ 10,509 $ 13,246,908 $ 1,582,642 $ 14,403,563 $ 1,593,151
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 March 31, 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 $ — $ — $ 511,806 $ 727,614 $ 1,239,420 States and political subdivisions 9,131 4,281 52,003 2,294,704 2,360,119 Other 1,500 — — — 1,500 Total $ 10,631 $ 4,281 $ 563,809 $ 3,022,318 $ 3,601,039 Estimated Fair Value Residential mortgage-backed securities $ — $ — $ 455,963 $ 714,388 $ 1,170,351 States and political subdivisions 9,092 4,268 50,260 2,215,879 2,279,499 Other 1,466 — — — 1,466 Total $ 10,558 $ 4,268 $ 506,223 $ 2,930,267 $ 3,451,316 Available For Sale Amortized Cost U. S. Treasury $ 499,348 $ 3,291,567 $ 197,882 $ 192,504 $ 4,181,301 Residential mortgage-backed securities 1,348 1,272 13,807 7,455,768 7,472,195 States and political subdivisions 228,757 234,591 848,067 3,759,844 5,071,259 Other — — — — 42,870 Total $ 729,453 $ 3,527,430 $ 1,059,756 $ 11,408,116 $ 16,767,625 Estimated Fair Value U. S. Treasury $ 486,430 $ 3,082,345 $ 164,133 $ 139,664 $ 3,872,572 Residential mortgage-backed securities 1,333 1,275 13,793 6,456,224 6,472,625 States and political subdivisions 228,134 231,649 817,088 3,516,645 4,793,516 Other — — — — 42,870 Total $ 715,897 $ 3,315,269 $ 995,014 $ 10,112,533 $ 15,181,583
Schedule of Realized Gain (Loss)	Sales of available for sale securities were as follows: Three Months Ended 2024 2023 Proceeds from sales $ — $ 884,273 Gross realized gains — 4,856 Gross realized losses — (4,835) Tax (expense) benefit of securities gains/losses — (4)
Investment Income	Premium amortization and discount accretion included in interest income on securities was as follows: Three Months Ended 2024 2023 Premium amortization $ (17,953) $ (25,925) Discount accretion 4,705 5,405 Net (premium amortization) discount accretion $ (13,248) $ (20,520)
Trading Account Securities, at Estimated Fair Value	Trading account securities, at estimated fair value, were as follows: March 31, December 31, U.S. Treasury $ 29,608 $ 30,265 States and political subdivisions 10,037 1,452 Total $ 39,645 $ 31,717
Net Gains and Losses on Trading Account Securities	Net gains and losses on trading account securities were as follows: Three Months Ended 2024 2023 Net gain on sales transactions $ 1,159 $ 968 Net mark-to-market gains (losses) (19) (17) Net gain (loss) on trading account securities $ 1,140 $ 951

Loans (Tables)

Loans (Tables)	3 Months Ended
	Mar. 31, 2024
Receivables [Abstract]
Loans	Loans were as follows: March 31, December 31, Commercial and industrial $ 6,108,136 $ 5,967,182 Energy: Production 663,436 681,568 Service 195,227 194,126 Other 79,217 61,043 Total energy 937,880 936,737 Commercial real estate: Commercial mortgages 6,980,116 6,746,709 Construction 1,772,416 1,680,724 Land 568,106 555,211 Total commercial real estate 9,320,638 8,982,644 Consumer real estate: Home equity lines of credit 810,053 792,876 Home equity loans 731,736 694,966 Home improvement loans 786,681 765,887 Other 230,200 206,997 Total consumer real estate 2,558,670 2,460,726 Total real estate 11,879,308 11,443,370 Consumer and other 462,882 476,962 Total loans $ 19,388,206 $ 18,824,251
Non-Accrual Loans, Segregated by Class of Loans	Non-accrual loans, segregated by class of loans, were as follows: March 31, 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 $ 25,446 $ 6,119 $ 19,545 $ 5,391 Energy 10,293 6,791 11,500 7,398 Commercial real estate: Buildings, land, and other 30,012 12,519 22,420 4,983 Construction — — — — Consumer real estate 5,764 3,533 7,442 5,160 Consumer and other — — — — Total $ 71,515 $ 28,962 $ 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 March 31, 2024 by class and year of origination. 2024 2023 2022 2021 2020 Prior Revolving Loans Revolving Loans Converted to Term Total Commercial and industrial $ 11 $ 2,059 $ 394 $ 2,941 $ 935 $ 2,719 $ 2,178 $ 14,209 $ 25,446 Energy 5,268 — — — 56 1,321 3,502 146 10,293 Commercial real estate: Buildings, land, and other — 19,812 3,360 3,656 — 3,184 — — 30,012 Construction — — — — — — — — — Consumer real estate — — — — 38 2,712 — 3,014 5,764 Consumer and other — — — — — — — — — Total $ 5,279 $ 21,871 $ 3,754 $ 6,597 $ 1,029 $ 9,936 $ 5,680 $ 17,369 $ 71,515
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 March 31, 2024 was as follows: Loans Loans Total Current Total Accruing Commercial and industrial $ 34,328 $ 25,713 $ 60,041 $ 6,048,095 $ 6,108,136 $ 7,319 Energy 2,349 24,375 26,724 911,156 937,880 19,351 Commercial real estate: Buildings, land, and other 43,836 11,206 55,042 7,493,180 7,548,222 8,223 Construction 891 — 891 1,771,525 1,772,416 — Consumer real estate 13,913 6,442 20,355 2,538,315 2,558,670 2,954 Consumer and other 5,889 253 6,142 456,740 462,882 253 Total $ 101,206 $ 67,989 $ 169,195 $ 19,219,011 $ 19,388,206 $ 38,100
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 or for the three months ended March 31, 2024 and March 31, 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. March 31, 2024 March 31, 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 $ 13,644 $ — Commercial real estate: Buildings, land, and other 19,137 — $ 32,781 $ —
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 March 31, 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 $ 788,259 $ 799,207 $ 640,565 $ 413,197 $ 331,143 $ 343,646 $ 2,103,487 $ 50,085 $ 5,469,589 6.28 Risk grade 9 41,562 43,457 43,429 6,436 5,063 17,960 89,123 5,008 252,038 9.00 Risk grade 10 25,688 5,250 5,278 15,136 2,927 4,848 100,864 707 160,698 10.00 Risk grade 11 23,260 23,096 20,467 24,455 6,621 2,941 91,166 8,359 200,365 11.00 Risk grade 12 11 1,257 250 2,937 924 2,719 450 11,779 20,327 12.00 Risk grade 13 — 802 144 4 11 — 1,728 2,430 5,119 13.00 $ 878,780 $ 873,069 $ 710,133 $ 462,165 $ 346,689 $ 372,114 $ 2,386,818 $ 78,368 $ 6,108,136 6.67 W/A risk grade 6.52 6.91 7.13 7.30 5.82 6.09 6.54 8.53 6.67 Energy Risk grades 1-8 $ 222,335 $ 32,898 $ 53,057 $ 69,990 $ 4,467 $ 5,496 $ 480,392 $ 7,897 $ 876,532 5.69 Risk grade 9 — 2,353 3,814 897 — 437 17,700 54 25,255 9.00 Risk grade 10 — — — 27 — 734 1,129 — 1,890 10.00 Risk grade 11 — — 2,094 18 89 2,963 18,311 435 23,910 11.00 Risk grade 12 5,268 — — — 56 1,321 802 146 7,593 12.00 Risk grade 13 — — — — — — 2,700 — 2,700 13.00 $ 227,603 $ 35,251 $ 58,965 $ 70,932 $ 4,612 $ 10,951 $ 521,034 $ 8,532 $ 937,880 6.00 W/A risk grade 5.89 6.95 7.17 5.98 6.37 8.90 5.76 7.27 6.00 Commercial real estate: Buildings, land, other Risk grades 1-8 $ 408,058 $ 1,515,706 $ 1,569,318 $ 1,195,050 $ 726,365 $ 1,285,229 $ 128,573 $ 97,011 $ 6,925,310 7.04 Risk grade 9 613 7,036 108,049 68,104 9,145 37,054 110,533 541 341,075 9.00 Risk grade 10 — 6,048 35,944 15,690 48,851 15,918 3,709 — 126,160 10.00 Risk grade 11 58 12,277 28,800 20,214 14,200 49,260 856 — 125,665 11.00 Risk grade 12 — 15,663 3,237 3,656 — 3,184 — — 25,740 12.00 Risk grade 13 — 4,149 123 — — — — — 4,272 13.00 $ 408,729 $ 1,560,879 $ 1,745,471 $ 1,302,714 $ 798,561 $ 1,390,645 $ 243,671 $ 97,552 $ 7,548,222 7.26 W/A risk grade 7.00 7.27 7.30 7.35 7.24 7.09 8.24 6.71 7.26 Construction Risk grades 1-8 $ 227,895 $ 433,679 $ 520,522 $ 187,481 $ 28,028 $ 1,353 $ 166,140 $ — $ 1,565,098 7.29 Risk grade 9 1,499 6,358 30,611 76,103 — — 5,396 — 119,967 9.00 Risk grade 10 13,555 — 12,299 15,000 — — — — 40,854 10.00 Risk grade 11 — — 35,367 11,130 — — — — 46,497 11.00 Risk grade 12 — — — — — — — — — 12.00 Risk grade 13 — — — — — — — — — 13.00 $ 242,949 $ 440,037 $ 598,799 $ 289,714 $ 28,028 $ 1,353 $ 171,536 $ — $ 1,772,416 7.56 W/A risk grade 7.46 7.39 7.70 8.28 2.54 6.82 7.27 — 7.56 Total commercial real estate $ 651,678 $ 2,000,916 $ 2,344,270 $ 1,592,428 $ 826,589 $ 1,391,998 $ 415,207 $ 97,552 $ 9,320,638 7.32 W/A risk grade 7.17 7.30 7.40 7.52 7.08 7.09 7.84 6.71 7.32
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 March 31, 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 $ — $ 1,216 $ 1,811 $ 1,601 $ 767 $ 2,390 $ 5,159 $ 969 $ 13,913 Past due 90 or more days — 366 606 390 207 1,050 805 3,018 6,442 Total past due — 1,582 2,417 1,991 974 3,440 5,964 3,987 20,355 Current loans 111,517 580,838 423,878 272,415 164,536 184,967 792,971 7,193 2,538,315 Total $ 111,517 $ 582,420 $ 426,295 $ 274,406 $ 165,510 $ 188,407 $ 798,935 $ 11,180 $ 2,558,670 Consumer and other: Past due 30-89 days $ 2,013 $ 600 $ 200 $ 75 $ 68 $ 34 $ 2,835 $ 64 $ 5,889 Past due 90 or more days 72 — 55 — — 12 101 13 253 Total past due 2,085 600 255 75 68 46 2,936 77 6,142 Current loans 30,106 46,779 25,114 4,709 3,062 1,961 322,406 22,603 456,740 Total $ 32,191 $ 47,379 $ 25,369 $ 4,784 $ 3,130 $ 2,007 $ 325,342 $ 22,680 $ 462,882
Revolving Loans Converted to Term [Table Text Block]	Revolving loans that converted to term during the three months ended March 31, 2024 and 2023 were as follows: Three Months Ended March 31, 2024 2023 Commercial and industrial $ 20,972 $ 15,490 Energy 44 3,435 Commercial real estate: Buildings, land and other 3,081 — Construction — — Consumer real estate 792 707 Consumer and other 3,020 6,342 Total $ 27,909 $ 25,974
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 March 31, 2024 and December 31, 2023. March 31, 2024 Commercial Energy Commercial Consumer Consumer Total Modeled expected credit losses $ 52,835 $ 5,471 $ 20,199 $ 12,705 $ 6,293 $ 97,503 Q-Factor and other qualitative adjustments 17,642 6,047 113,753 444 2,109 139,995 Specific allocations 5,119 2,700 4,272 708 — 12,799 Total $ 75,596 $ 14,218 $ 138,224 $ 13,857 $ 8,402 $ 250,297 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 months ended March 31, 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: March 31, 2024 Beginning balance $ 74,006 $ 17,814 $ 130,598 $ 13,538 $ 10,040 $ 245,996 Credit loss expense (benefit) 1,992 (3,776) 7,610 1,806 4,018 11,650 Charge-offs (2,144) — — (1,669) (8,257) (12,070) Recoveries 1,742 180 16 182 2,601 4,721 Net (charge-offs) recoveries (402) 180 16 (1,487) (5,656) (7,349) Ending balance $ 75,596 $ 14,218 $ 138,224 $ 13,857 $ 8,402 $ 250,297 Commercial Energy Commercial Consumer Consumer Total March 31, 2023 Beginning balance $ 104,237 $ 18,062 $ 90,301 $ 8,004 $ 7,017 $ 227,621 Credit loss expense (benefit) (20,684) 966 25,361 1,283 5,749 12,675 Charge-offs (6,180) — — (250) (6,942) (13,372) Recoveries 1,092 163 31 671 2,633 4,590 Net (charge-offs) recoveries (5,088) 163 31 421 (4,309) (8,782) Ending balance $ 78,465 $ 19,191 $ 115,693 $ 9,708 $ 8,457 $ 231,514
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 March 31, 2024. 2024 2023 2022 2021 2020 Prior Revolving Loans Revolving Loans Converted to Term Total Commercial and industrial $ — $ 96 $ 572 $ 439 $ 6 $ 13 $ 794 $ 224 $ 2,144 Energy — — — — — — — — — Commercial real estate: Buildings, land and other — — — — — — — — — Construction — — — — — — — — — Consumer real estate — — 148 253 — 280 921 67 1,669 Consumer and other 1,958 5,543 64 4 4 34 650 — 8,257 Total $ 1,958 $ 5,639 $ 784 $ 696 $ 10 $ 327 $ 2,365 $ 291 $ 12,070
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 March 31, 2024 and December 31, 2023. March 31, 2024 December 31, 2023 Loan Specific Allocations Loan Specific Allocations Commercial and industrial $ 24,743 $ 5,119 $ 18,670 $ 2,435 Energy 10,147 2,700 11,353 2,700 Commercial real estate: Buildings, land and other 29,211 4,272 21,373 2,650 Construction — — — — Consumer real estate 5,584 708 7,235 741 Consumer and other — — — — Total $ 69,685 $ 12,799 $ 58,631 $ 8,526

Deposits (Tables)

Deposits (Tables)	3 Months Ended
	Mar. 31, 2024
Disclosure Text Block [Abstract]
Deposit Liabilities, Type	Deposits were as follows: March 31, December 31, Non-interest-bearing demand deposits $ 13,754,985 $ 14,926,094 Interest-bearing deposits: Savings and interest checking 9,994,133 10,512,637 Money market accounts 11,072,561 10,997,279 Time accounts 5,984,807 5,484,558 Total interest-bearing deposits 27,051,501 26,994,474 Total deposits $ 40,806,486 $ 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. March 31, December 31, Deposits from foreign sources (primarily Mexico) $ 1,087,494 $ 1,061,701 Non-interest-bearing public funds deposits 442,355 675,016 Interest-bearing public funds deposits 697,824 630,455 Total deposits not covered by deposit insurance 21,378,776 22,393,786 Time deposits not covered by deposit insurance 2,606,127 2,339,716

Commitments and Contingencies (

Commitments and Contingencies (Tables)	3 Months Ended
	Mar. 31, 2024
Commitments and Contingencies Disclosure [Abstract]
Financial Instruments with Off-Balance-Sheet Risk	Financial instruments with off-balance-sheet risk were as follows: March 31, December 31, Commitments to extend credit $ 12,027,630 $ 12,195,073 Standby letters of credit 416,084 438,635 Deferred standby letter of credit fees 2,750 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 2024 2023 Beginning balance $ 51,751 $ 58,593 Credit loss expense (benefit) 2,000 (3,675) Ending balance $ 53,751 $ 54,918
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 2024 2023 Amortization of lease right-of-use assets $ 8,790 $ 8,765 Short-term lease expense 325 409 Non-lease components (including taxes, insurance, common maintenance, etc.) 3,549 3,381 Total $ 12,664 $ 12,555

Capital and Regulatory Matters

Capital and Regulatory Matters (Tables)	3 Months Ended
	Mar. 31, 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 March 31, 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 March 31, 2024 Common Equity Tier 1 to Risk-Weighted Assets Cullen/Frost $ 4,102,330 13.41 % $ 2,140,804 7.00 % N/A N/A Frost Bank 4,146,611 13.57 2,138,279 7.00 $ 1,985,545 6.50 % Tier 1 Capital to Risk-Weighted Assets Cullen/Frost 4,247,782 13.89 2,599,548 8.50 1,834,975 6.00 Frost Bank 4,146,611 13.57 2,596,482 8.50 2,443,748 8.00 Total Capital to Risk-Weighted Assets Cullen/Frost 4,694,792 15.35 3,211,206 10.50 3,058,292 10.00 Frost Bank 4,433,621 14.51 3,207,419 10.50 3,054,685 10.00 Leverage Ratio Cullen/Frost 4,247,782 8.44 2,012,280 4.00 N/A N/A Frost Bank 4,146,611 8.24 2,011,864 4.00 2,514,830 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)	3 Months Ended
	Mar. 31, 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 March 31, 2024 and December 31, 2023. March 31, 2024 December 31, 2023 Notional Estimated Notional Estimated Non-hedging interest rate derivatives: Financial institution counterparties: Loan/lease interest rate swaps – assets 1,224,589 $ 69,640 1,040,659 $ 58,486 Loan/lease interest rate swaps – liabilities 538,648 (9,899) 617,266 (20,293) Loan/lease interest rate caps – assets 243,648 11,177 275,000 11,747 Customer counterparties: Loan/lease interest rate swaps – assets 538,648 9,899 617,266 20,482 Loan/lease interest rate swaps – liabilities 1,224,589 (69,639) 1,040,659 (58,485) Loan/lease interest rate caps – liabilities 243,648 (11,177) 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 March 31, 2024 were as follows: Weighted-Average Interest Interest Interest rate swaps: Non-hedging interest rate swaps – financial institution counterparties 4.91 % 5.01 % Non-hedging interest rate swaps – customer counterparties 5.01 4.91
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. March 31, 2024 December 31, 2023 Notional Notional Estimated Notional Estimated Financial institution counterparties: Oil – assets Barrels 3,666 $ 11,866 5,601 $ 37,667 Oil – liabilities Barrels 6,183 (29,196) 4,581 (18,500) Natural gas – assets MMBTUs 15,537 10,208 17,363 11,822 Natural gas – liabilities MMBTUs 5,593 (1,715) 6,462 (2,499) Customer counterparties: Oil – assets Barrels 6,382 29,855 4,618 18,722 Oil – liabilities Barrels 3,468 (11,656) 5,564 (36,877) Natural gas – assets MMBTUs 5,593 1,717 6,462 2,499 Natural gas – liabilities MMBTUs 15,537 (9,956) 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. March 31, 2024 December 31, 2023 Notional Notional Estimated Notional Estimated Financial institution counterparties: Forward and option contracts – assets CAD 125 $ — 250 $ 1 Forward and option contracts – liabilities EUR — — 3,000 (14) Forward and option contracts – liabilities CAD 125 — 250 (5) Customer counterparties: Forward and option contracts – assets EUR — — 3,000 16 Forward and option contracts – assets CAD 250 1 250 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 2024 2023 Commercial loan/lease interest rate swaps: Amount of gain (loss) included in interest income on loans $ — $ 12
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 2024 2023 Non-hedging interest rate derivatives: Other non-interest income $ 1,125 $ 710 Other non-interest expense — (1) Non-hedging commodity derivatives: Other non-interest income 379 422 Non-hedging foreign currency derivatives: Other non-interest income 11 25

Balance Sheet Offsetting (Table

Balance Sheet Offsetting (Tables)	3 Months Ended	12 Months Ended
	Mar. 31, 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 March 31, 2024 is presented in the following tables. Gross Amount Gross Amount Net Amount March 31, 2024 Financial assets: Derivatives: Interest rate contracts $ 80,817 $ — $ 80,817 Commodity contracts 22,074 — 22,074 Total derivatives 102,891 — 102,891 Resell agreements 84,650 — 84,650 Total $ 187,541 $ — $ 187,541 Financial liabilities: Derivatives: Interest rate contracts $ 9,899 $ — $ 9,899 Commodity contracts 30,911 — 30,911 Total derivatives 40,810 — 40,810 Repurchase agreements 3,943,207 — 3,943,207 Total $ 3,984,017 $ — $ 3,984,017	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 March 31, 2024 Financial assets: Derivatives: Counterparty H $ 31,738 $ (12,183) $ (19,555) $ — Counterparty F 17,484 (15,966) (1,136) 382 Counterparty B 22,234 (2,775) (19,459) — Counterparty E 15,519 (2,228) (13,080) 211 Other counterparties 15,916 (7,323) (8,270) 323 Total derivatives 102,891 (40,475) (61,500) 916 Resell agreements 84,650 — (84,650) — Total $ 187,541 $ (40,475) $ (146,150) $ 916 Financial liabilities: Derivatives: Counterparty H $ 12,183 $ (12,183) $ — $ — Counterparty F 15,966 (15,966) — — Counterparty B 2,775 (2,775) — — Counterparty E 2,228 (2,228) — — Other counterparties 7,658 (7,323) (335) — Total derivatives 40,810 (40,475) (335) — Repurchase agreements 3,943,207 — (3,943,207) — Total $ 3,984,017 $ (40,475) $ (3,943,542) $ —	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 March 31, 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 March 31, 2024 Repurchase agreements: U.S. Treasury $ 2,575,020 $ — $ — $ — $ 2,575,020 Residential mortgage-backed securities 1,368,187 — — — 1,368,187 Total borrowings $ 3,943,207 $ — $ — $ — $ 3,943,207 Gross amount of recognized liabilities for repurchase agreements $ 3,943,207 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)	3 Months Ended
	Mar. 31, 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. As of March 31, 2024, there were 226,288 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 — — 2,142 107.41 — — — — Exercised/vested — — (458) 65.43 (45,818) 57.89 (37,900) 76.92 Forfeited/expired — — (427) 105.40 (22,913) 57.89 — — Balance, March 31, 2024 54,164 89.71 568,063 99.82 198,323 101.12 448,041 70.77
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 2024 2023 New shares issued from available authorized shares — 49,887 Shares issued from available treasury stock 84,176 500 Proceeds from stock option exercises $ 2,915 $ 1,500
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 2024 2023 Non-vested stock units $ 3,379 $ 3,307 Performance stock units 359 1,435 Total $ 3,738 $ 4,742 Income tax benefit $ 1,145 $ 1,068
Unrecognized Stock-Based Compensation Expense	Unrecognized stock-based compensation expense at March 31, 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 $ 19,470 Performance stock units 8,072 Total $ 27,542

Earnings Per Common Share (Tabl

Earnings Per Common Share (Tables)	3 Months Ended
	Mar. 31, 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 2024 2023 Net income $ 135,690 $ 177,653 Less: Preferred stock dividends 1,669 1,669 Net income available to common shareholders 134,021 175,984 Less: Earnings allocated to participating securities 1,639 1,807 Net earnings allocated to common stock $ 132,382 $ 174,177 Distributed earnings allocated to common stock $ 59,080 $ 56,006 Undistributed earnings allocated to common stock 73,302 118,171 Net earnings allocated to common stock $ 132,382 $ 174,177 Weighted-average shares outstanding for basic earnings per common share 64,216,323 64,373,563 Dilutive effect of stock compensation 155,408 258,513 Weighted-average shares outstanding for diluted earnings per common share 64,371,731 64,632,076

Defined Benefit Plans (Tables)

Defined Benefit Plans (Tables)	3 Months Ended
	Mar. 31, 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 2024 2023 Expected return on plan assets, net of expenses $ (2,411) $ (2,740) Interest cost on projected benefit obligation 1,662 1,746 Net amortization and deferral 418 870 Net periodic expense (benefit) $ (331) $ (124)

Income Taxes (Tables)

Income Taxes (Tables)	3 Months Ended
	Mar. 31, 2024
Income Tax Disclosure [Abstract]
Income Tax Expense	Income tax expense was as follows: Three Months Ended 2024 2023 Current income tax expense $ 30,317 $ 34,995 Deferred income tax expense (benefit) (4,446) (1,809) Income tax expense, as reported $ 25,871 $ 33,186 Effective tax rate 16.0 % 15.7 %

Other Comprehensive Income (L_2

Other Comprehensive Income (Loss) (Tables)	3 Months Ended
	Mar. 31, 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 $ (199,075) $ (41,806) $ (157,269) $ 260,269 $ 54,656 $ 205,613 Change in net unrealized gain on securities transferred to held to maturity (159) (34) (125) (160) (33) (127) Reclassification adjustment for net (gains) losses included in net income — — — (21) (4) (17) Total securities available for sale and transferred securities (199,234) (41,840) (157,394) 260,088 54,619 205,469 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) 418 88 330 870 183 687 Total defined-benefit post-retirement benefit plans 418 88 330 870 183 687 Total other comprehensive income (loss) $ (198,816) $ (41,752) $ (157,064) $ 260,958 $ 54,802 $ 206,156
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 (157,394) — (157,394) Reclassification of amounts included in net income — 330 330 Net other comprehensive income (loss) during period (157,394) 330 (157,064) Balance at March 31, 2024 $ (1,252,188) $ (24,095) $ (1,276,283) Balance at January 1, 2023 $ (1,313,791) $ (34,503) $ (1,348,294) Other comprehensive income (loss) before reclassifications 205,486 — 205,486 Reclassification of amounts included in net income (17) 687 670 Net other comprehensive income (loss) during period 205,469 687 206,156 Balance at March 31, 2023 $ (1,108,322) $ (33,816) $ (1,142,138)

Operating Segments (Tables)

Operating Segments (Tables)	3 Months Ended
	Mar. 31, 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: March 31, 2024 Net interest income (expense) $ 391,805 $ 1,669 $ (3,423) $ 390,051 Credit loss expense (benefit) 13,650 — — 13,650 Non-interest income 66,380 45,426 (429) 111,377 Non-interest expense 286,830 37,973 1,414 326,217 Income (loss) before income taxes 157,705 9,122 (5,266) 161,561 Income tax expense (benefit) 25,635 1,916 (1,680) 25,871 Net income (loss) 132,070 7,206 (3,586) 135,690 Preferred stock dividends — — 1,669 1,669 Net income (loss) available to common shareholders $ 132,070 $ 7,206 $ (5,255) $ 134,021 Revenues from (expenses to) external customers $ 458,185 $ 47,095 $ (3,852) $ 501,428 March 31, 2023 Net interest income (expense) $ 401,318 $ 1,654 $ (3,152) $ 399,820 Non-interest income 63,643 42,038 (416) 105,265 Non-interest expense 249,865 33,949 1,328 285,142 Income (loss) before income taxes 205,992 9,743 (4,896) 210,839 Income tax expense (benefit) 32,366 2,046 (1,226) 33,186 Net income (loss) 173,626 7,697 (3,670) 177,653 Preferred stock dividends — — 1,669 1,669 Net income (loss) available to common shareholders $ 173,626 $ 7,697 $ (5,339) $ 175,984 Revenues from (expenses to) external customers $ 464,961 $ 43,692 $ (3,568) $ 505,085

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	3 Months Ended
	Mar. 31, 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 March 31, 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 March 31, 2024 Securities available for sale: U.S. Treasury $ 3,872,572 $ — $ — $ 3,872,572 Residential mortgage-backed securities — 6,472,625 — 6,472,625 States and political subdivisions — 4,793,516 — 4,793,516 Other — 42,870 — 42,870 Trading account securities: U.S. Treasury 29,608 — — 29,608 States and political subdivisions — 10,037 — 10,037 Derivative assets: Interest rate swaps, caps, and floors — 90,716 — 90,716 Commodity swaps and options — 53,646 — 53,646 Foreign currency forward contracts 1 — — 1 Derivative liabilities: Interest rate swaps, caps, and floors — 90,715 — 90,715 Commodity swaps and options — 52,523 — 52,523 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. Three Months Ended Three Months Ended Level 2 Level 3 Level 2 Level 3 Carrying value before allocations $ 16,332 $ 16,182 $ 368 $ 6,242 Specific (allocations) reversals of prior allocations (1,589) (1,172) — (900) Fair value $ 14,743 $ 15,010 $ 368 $ 5,342
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: March 31, 2024 December 31, 2023 Carrying Estimated Carrying Estimated Financial assets: Level 2 inputs: Cash and cash equivalents $ 8,464,517 $ 8,464,517 $ 8,687,276 $ 8,687,276 Securities held to maturity 3,600,729 3,451,316 3,619,428 3,532,044 Accrued interest receivable 206,090 206,090 251,385 251,385 Level 3 inputs: Loans, net 19,137,909 18,637,078 18,578,255 18,117,369 Financial liabilities: Level 2 inputs: Deposits 40,806,486 40,792,337 41,920,568 41,903,580 Federal funds purchased 41,200 41,200 14,200 14,200 Repurchase agreements 3,943,207 3,943,207 4,127,188 4,127,188 Junior subordinated deferrable interest debentures 123,141 123,712 123,127 123,712 Subordinated notes 99,530 96,513 99,491 96,071 Accrued interest payable 65,102 65,102 61,222 61,222

Significant Accounting Polici_4

Significant Accounting Policies - Additional Cash Flow Information (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Accounting Policies [Abstract]
Cash paid for interest	$ 191,569	$ 129,207
Cash paid for income taxes	0	0
Unsettled securities transactions	26,255	303,242
Right-of-use lease assets obtained in exchange for lessee operating lease liabilities	$ 4,097	$ 2,879

Securities - Additional Informa

Securities - Additional Information (Detail) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Schedule Of Marketable Securities [Line Items]
AOCI, Debt Securities, Available-for-sale, Adjustment, Pre Tax	$ 992	$ 1,200
Net unamortized unrealized gain on transferred securities included in accumulated other comprehensive income, net of tax	$ 784	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	72.40%
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	820,100	1,000,000
Accrued interest receivable	20,300	40,900
Available-for-sale Securities [Member]
Schedule Of Marketable Securities [Line Items]
Carry Value of Securities Pledged	5,900,000	6,100,000
Accrued interest receivable	$ 78,500	$ 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	Mar. 31, 2024	Dec. 31, 2023
Schedule of Investments [Line Items]
Held to Maturity, Amortized Cost	$ 3,601,039	$ 3,619,738
Debt Securities, Held-to-maturity, Accumulated Unrecognized Gain	20,197	43,066
Debt Securities, Held-to-maturity, Accumulated Unrecognized Loss	169,920	130,760
Debt Securities, Held-to-maturity, Fair Value	3,451,316	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 March 31, 2024 and December 31, 2023	3,600,729	3,619,428
Residential Mortgage Backed Securities [Member]
Schedule of Investments [Line Items]
Held to Maturity, Amortized Cost	1,239,420	1,250,431
Debt Securities, Held-to-maturity, Accumulated Unrecognized Gain	0	76
Debt Securities, Held-to-maturity, Accumulated Unrecognized Loss	69,069	54,175
Debt Securities, Held-to-maturity, Fair Value	1,170,351	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 March 31, 2024 and December 31, 2023	1,239,420	1,250,431
US States and Political Subdivisions Debt Securities [Member]
Schedule of Investments [Line Items]
Held to Maturity, Amortized Cost	2,360,119	2,367,807
Debt Securities, Held-to-maturity, Accumulated Unrecognized Gain	20,197	42,990
Debt Securities, Held-to-maturity, Accumulated Unrecognized Loss	100,817	76,540
Debt Securities, Held-to-maturity, Fair Value	2,279,499	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 March 31, 2024 and December 31, 2023	2,359,809	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	34	45
Debt Securities, Held-to-maturity, Fair Value	1,466	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 March 31, 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	Mar. 31, 2024	Dec. 31, 2023
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-maturity	$ 3,601,039	$ 3,619,738
US States and Political Subdivisions Debt Securities [Member]
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-maturity	2,360,119	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	1,855,277	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	504,842	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	800,354	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	301,620	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	498,734	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	1,538,918	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	1,538,918	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	19,756	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	13,648	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	6,108	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	1,091	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	1,091	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
	Mar. 31, 2024	Mar. 31, 2023	Dec. 31, 2023	Dec. 31, 2022
Schedule of Held-to-maturity Securities [Line Items]
Securities, held-to-maturity, allowance for credit loss	$ 310		$ 310
Debt Securities [Member]
Schedule of Held-to-maturity Securities [Line Items]
Securities, held-to-maturity, allowance for credit loss	310	$ 262	$ 310	$ 158
Credit loss expense (benefit)	$ 0	$ 104

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	Mar. 31, 2024	Dec. 31, 2023
Schedule of Investments [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	$ 16,767,625	$ 17,965,338
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	7,109	14,828
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	1,593,151	1,401,795
Debt Securities, Available-for-sale, Allowance for Credit Loss	0	0
Securities available for sale, at estimated fair value	15,181,583	16,578,371
US Treasury Securities [Member]
Schedule of Investments [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	4,181,301	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	308,729	285,305
Debt Securities, Available-for-sale, Allowance for Credit Loss	0	0
Securities available for sale, at estimated fair value	3,872,572	4,927,589
Residential Mortgage Backed Securities [Member]
Schedule of Investments [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	7,472,195	7,463,954
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	4,796	9,066
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	1,004,366	876,338
Debt Securities, Available-for-sale, Allowance for Credit Loss	0	0
Securities available for sale, at estimated fair value	6,472,625	6,596,682
US States and Political Subdivisions Debt Securities [Member]
Schedule of Investments [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	5,071,259	5,245,721
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	2,313	5,762
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	280,056	240,152
Debt Securities, Available-for-sale, Allowance for Credit Loss	0	0
Securities available for sale, at estimated fair value	4,793,516	5,011,331
Other Investments [Member]
Schedule of Investments [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	42,870	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	$ 42,870	$ 42,769

Securities - Securities Availab

Securities - Securities Available for Sale, with Unrealized Losses Segregated by Length of Impairment (Detail) - USD ($) $ in Thousands	Mar. 31, 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	$ 1,156,655
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	10,509
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	13,246,908
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	1,582,642
Debt Securities, Available-for-sale, Unrealized Loss Position	14,403,563
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	1,593,151	$ 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	3,872,572
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	308,729
Debt Securities, Available-for-sale, Unrealized Loss Position	3,872,572
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	308,729	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	376,347
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	3,974
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	5,633,391
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	1,000,392
Debt Securities, Available-for-sale, Unrealized Loss Position	6,009,738
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	1,004,366	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	780,308
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	6,535
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	3,740,945
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	273,521
Debt Securities, Available-for-sale, Unrealized Loss Position	4,521,253
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	$ 280,056	$ 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	Mar. 31, 2024	Dec. 31, 2023
Schedule of Investments [Line Items]
Held to Maturity, Due in one year or less, Amortized Cost	$ 10,631
Held to Maturity, Due after one year through five years, Amortized Cost	4,281
Held to Maturity, Due after five years through ten years, Amortized Cost	563,809
Held to Maturity, Due after ten years, Amortized Cost	3,022,318
Held to Maturity, Amortized Cost	3,601,039	$ 3,619,738
Held to Maturity, Due in one year or less, Estimated Fair Value	10,558
Held to Maturity, Due after one year through five years, Estimated Fair Value	4,268
Held to Maturity, Due after five years through ten years, Estimated Fair Value	506,223
Held to Maturity, Due after ten years, Estimated Fair Value	2,930,267
Held to Maturity, Estimated Fair Value	3,451,316	3,532,044
Available-for-sale Securities, Due in one year or less, Amortized Cost	729,453
Available for Sale, Due after one year through five years, Amortized Cost	3,527,430
Available for Sale, Due after five years through ten years, Amortized Cost	1,059,756
Available for Sale, Due after ten years, Amortized Cost	11,408,116
Debt Securities, Available-for-sale, Amortized Cost	16,767,625	17,965,338
Available for Sale, Due in one year or less, Estimated Fair Value	715,897
Available for Sale, Due after one year through five years, Estimated Fair Value	3,315,269
Available for Sale, Due after five years through ten years, Estimated Fair Value	995,014
Available for Sale, Due after ten years, Estimated Fair Value	10,112,533
Securities available for sale, at estimated fair value	15,181,583	16,578,371
US Treasury Securities [Member]
Schedule of Investments [Line Items]
Available-for-sale Securities, Due in one year or less, Amortized Cost	499,348
Available for Sale, Due after one year through five years, Amortized Cost	3,291,567
Available for Sale, Due after five years through ten years, Amortized Cost	197,882
Available for Sale, Due after ten years, Amortized Cost	192,504
Debt Securities, Available-for-sale, Amortized Cost	4,181,301	5,212,894
Available for Sale, Due in one year or less, Estimated Fair Value	486,430
Available for Sale, Due after one year through five years, Estimated Fair Value	3,082,345
Available for Sale, Due after five years through ten years, Estimated Fair Value	164,133
Available for Sale, Due after ten years, Estimated Fair Value	139,664
Securities available for sale, at estimated fair value	3,872,572	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	0
Held to Maturity, Due after five years through ten years, Amortized Cost	511,806
Held to Maturity, Due after ten years, Amortized Cost	727,614
Held to Maturity, Amortized Cost	1,239,420	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	0
Held to Maturity, Due after five years through ten years, Estimated Fair Value	455,963
Held to Maturity, Due after ten years, Estimated Fair Value	714,388
Held to Maturity, Estimated Fair Value	1,170,351	1,196,332
Available-for-sale Securities, Due in one year or less, Amortized Cost	1,348
Available for Sale, Due after one year through five years, Amortized Cost	1,272
Available for Sale, Due after five years through ten years, Amortized Cost	13,807
Available for Sale, Due after ten years, Amortized Cost	7,455,768
Debt Securities, Available-for-sale, Amortized Cost	7,472,195	7,463,954
Available for Sale, Due in one year or less, Estimated Fair Value	1,333
Available for Sale, Due after one year through five years, Estimated Fair Value	1,275
Available for Sale, Due after five years through ten years, Estimated Fair Value	13,793
Available for Sale, Due after ten years, Estimated Fair Value	6,456,224
Securities available for sale, at estimated fair value	6,472,625	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	9,131
Held to Maturity, Due after one year through five years, Amortized Cost	4,281
Held to Maturity, Due after five years through ten years, Amortized Cost	52,003
Held to Maturity, Due after ten years, Amortized Cost	2,294,704
Held to Maturity, Amortized Cost	2,360,119	2,367,807
Held to Maturity, Due in one year or less, Estimated Fair Value	9,092
Held to Maturity, Due after one year through five years, Estimated Fair Value	4,268
Held to Maturity, Due after five years through ten years, Estimated Fair Value	50,260
Held to Maturity, Due after ten years, Estimated Fair Value	2,215,879
Held to Maturity, Estimated Fair Value	2,279,499	2,334,257
Available-for-sale Securities, Due in one year or less, Amortized Cost	228,757
Available for Sale, Due after one year through five years, Amortized Cost	234,591
Available for Sale, Due after five years through ten years, Amortized Cost	848,067
Available for Sale, Due after ten years, Amortized Cost	3,759,844
Debt Securities, Available-for-sale, Amortized Cost	5,071,259	5,245,721
Available for Sale, Due in one year or less, Estimated Fair Value	228,134
Available for Sale, Due after one year through five years, Estimated Fair Value	231,649
Available for Sale, Due after five years through ten years, Estimated Fair Value	817,088
Available for Sale, Due after ten years, Estimated Fair Value	3,516,645
Securities available for sale, at estimated fair value	4,793,516	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	1,466
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	1,466	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	42,870	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	$ 42,870	$ 42,769

Securities - Sales of Available

Securities - Sales of Available for Sale Securities (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Investments, Debt and Equity Securities [Abstract]
Proceeds from sales	$ 0	$ 884,273
Gross realized gains	0	4,856
Gross realized losses	0	(4,835)
Tax (expense) benefit of securities gains/losses	$ 0	$ (4)

Securities Securities - Premium

Securities Securities - Premium Amortization and Discount Accretion Included in Income on Securities (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Investments, Debt and Equity Securities [Abstract]
Premium amortization	$ (17,953)	$ (25,925)
Discount accretion	4,705	5,405
Net (premium amortization) discount accretion	$ (13,248)	$ (20,520)

Securities - Trading Account Se

Securities - Trading Account Securities, at Estimated Fair Value (Detail) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Debt and Equity Securities, FV-NI [Line Items]
Trading account securities	$ 39,645	$ 31,717
U.S. Treasury [Member]
Debt and Equity Securities, FV-NI [Line Items]
Trading account securities	29,608	30,265
States and political subdivisions [Member]
Debt and Equity Securities, FV-NI [Line Items]
Trading account securities	$ 10,037	$ 1,452

Securities - Net Gains and Loss

Securities - Net Gains and Losses on Trading Account Securities (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Investments, Debt and Equity Securities [Abstract]
Net gain on sales transactions	$ 1,159	$ 968
Net mark-to-market gains (losses)	(19)	(17)
Net gain (loss) on trading account securities	$ 1,140	$ 951

Loans - Additional Information

Loans - Additional Information (Detail) $ in Thousands	3 Months Ended
	Mar. 31, 2024 USD ($)	Mar. 31, 2023 USD ($)	Dec. 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%
Maximum percentage loan related to single industry	10%
U.S. dollar denominated loans and commitments to borrowers in Mexico	$ 0		$ 0
Loans and Leases Receivable, Related Parties	$ 425,900		$ 416,100
Texas Leading Index economic condition indicator	128.2		127.1
Financing Receivable, Change in Method, Credit Loss Expense (Reversal)	$ 7,200
Financing Receivable, Allowance for Credit Loss	250,297		$ 245,996
Loans, net of unearned discounts	19,388,206		18,824,251
Nonperforming Financial Instruments [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	5,279
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	21,871
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	1,958
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	$ 5,639
Automobile Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Percentage of total loans	5.80%
Commercial and Industrial Total Energy Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Percentage of total loans	4.80%
Financing Receivable, Allowance for Credit Loss	$ 14,218	$ 19,191	17,814	$ 18,062
Financing Receivable, Allowance for Credit Loss, Writeoff	0	0
Loans, net of unearned discounts	937,880		936,737
Financing Receivable, Year One, Originated, Current Fiscal Year	227,603
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	35,251
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	5,268
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	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
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	0
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	1,200	600
Total consumer real estate loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Allowance for Credit Loss	13,857	9,708	13,538	8,004
Financing Receivable, Allowance for Credit Loss, Writeoff	1,669	250
Loans, net of unearned discounts	2,558,670		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
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	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
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	0
Commercial Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Allowance for Credit Loss	75,596	78,465	74,006	104,237
Financing Receivable, Allowance for Credit Loss, Writeoff	2,144	6,180
Loans, net of unearned discounts	6,108,136		5,967,182
Financing Receivable, Year One, Originated, Current Fiscal Year	878,780
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	873,069
Commercial Portfolio Segment [Member] | Nonperforming Financial Instruments [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	11
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	2,059
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
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	96
Commercial Portfolio Segment [Member] | Additional Funding Agreement Terms
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	0
Commercial Portfolio Segment [Member] | Combination: Payment Delay and Term Extention
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	28,900	0
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	8,402	8,457	10,040	$ 7,017
Financing Receivable, Allowance for Credit Loss, Writeoff	8,257	$ 6,942
Loans, net of unearned discounts	462,882		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
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	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	1,958
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	5,543
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	2,000
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	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	6,980,116		6,746,709
Commitments to Extend Credit [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financial instruments with off- balance-sheet risk	12,027,630		12,195,073
Commitments to Extend Credit [Member] | Automobile Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unfunded balances	490,900
Commitments to Extend Credit [Member] | Commercial and Industrial Total Energy Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unfunded balances	1,100,000
Standby Letters of Credit [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financial instruments with off- balance-sheet risk	416,084		438,635
Standby Letters of Credit [Member] | Automobile Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unfunded balances	20,300
Standby Letters of Credit [Member] | Commercial and Industrial Total Energy Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unfunded balances	91,700
Loans Receivable [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Interest Receivable	$ 94,000		$ 90,800

Loans - Loans (Detail)

Loans - Loans (Detail) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	$ 19,388,206	$ 18,824,251
Commercial Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	6,108,136	5,967,182
Energy Production [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	663,436	681,568
Energy Service [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	195,227	194,126
Energy Other [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	79,217	61,043
Commercial and Industrial Total Energy Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	937,880	936,737
Commercial mortgage [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	6,980,116	6,746,709
Construction Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	1,772,416	1,680,724
Commercial land loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	568,106	555,211
Commercial Real Estate Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	9,320,638	8,982,644
Home Equity Line of Credit [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	810,053	792,876
Home Equity Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	731,736	694,966
Home Improvement Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	786,681	765,887
Other consumer real estate loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	230,200	206,997
Total consumer real estate loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	2,558,670	2,460,726
Real Estate Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	11,879,308	11,443,370
Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	$ 462,882	$ 476,962

Loans - Non-Accrual Loans, Segr

Loans - Non-Accrual Loans, Segregated by Class of Loans (Detail) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Non Accrual Loans Segregated By Class Of Loans [Line Items]
Non-accrual loans	$ 71,515	$ 60,907
Non-accrual with no credit loss allowance	28,962	22,932
Commercial Portfolio Segment [Member]
Non Accrual Loans Segregated By Class Of Loans [Line Items]
Non-accrual loans	25,446	19,545
Non-accrual with no credit loss allowance	6,119	5,391
Commercial and Industrial Total Energy Loans [Member]
Non Accrual Loans Segregated By Class Of Loans [Line Items]
Non-accrual loans	10,293	11,500
Non-accrual with no credit loss allowance	6,791	7,398
Commercial Real Estate Buildings Land And Other Loans [Member]
Non Accrual Loans Segregated By Class Of Loans [Line Items]
Non-accrual loans	30,012	22,420
Non-accrual with no credit loss allowance	12,519	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	5,764	7,442
Non-accrual with no credit loss allowance	3,533	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	Mar. 31, 2024	Dec. 31, 2023
Loans and Leases Receivable Disclosure [Line Items]
Non-accrual loans	$ 71,515	$ 60,907
Nonperforming Financial Instruments [Member]
Loans and Leases Receivable Disclosure [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	5,279
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	21,871
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	3,754
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	6,597
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	1,029
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	9,936
Financing Receivable, Revolving	5,680
Financing Receivable, Revolving, Converted to Term Loan	17,369
Commercial Portfolio Segment [Member]
Loans and Leases Receivable Disclosure [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	878,780
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	873,069
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	710,133
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	462,165
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	346,689
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	372,114
Financing Receivable, Revolving	2,386,818
Non-accrual loans	25,446	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	11
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	2,059
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	394
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	2,941
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	935
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	2,719
Financing Receivable, Revolving	2,178
Financing Receivable, Revolving, Converted to Term Loan	14,209
Commercial and Industrial Total Energy Loans [Member]
Loans and Leases Receivable Disclosure [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	227,603
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	35,251
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	58,965
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	70,932
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	4,612
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	10,951
Financing Receivable, Revolving	521,034
Non-accrual loans	10,293	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	5,268
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	3,502
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	408,729
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	1,560,879
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	1,745,471
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	1,302,714
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	798,561
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	1,390,645
Financing Receivable, Revolving	243,671
Non-accrual loans	30,012	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	0
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	19,812
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	3,360
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	3,656
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	0
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	3,184
Financing Receivable, Revolving	0
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	242,949
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	440,037
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	598,799
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	289,714
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	28,028
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	1,353
Financing Receivable, Revolving	171,536
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	5,764	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	38
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	2,712
Financing Receivable, Revolving	0
Financing Receivable, Revolving, Converted to Term Loan	3,014
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	Mar. 31, 2024	Dec. 31, 2023
Financing Receivable, Past Due [Line Items]
Total loans	$ 19,388,206	$ 18,824,251
Accruing Loans 90 or More Days Past Due	38,100
Commercial Portfolio Segment [Member]
Financing Receivable, Past Due [Line Items]
Total loans	6,108,136	5,967,182
Accruing Loans 90 or More Days Past Due	7,319
Commercial and Industrial Total Energy Loans [Member]
Financing Receivable, Past Due [Line Items]
Total loans	937,880	936,737
Accruing Loans 90 or More Days Past Due	19,351
Commercial Real Estate Buildings Land And Other Loans [Member]
Financing Receivable, Past Due [Line Items]
Total loans	7,548,222	7,301,920
Accruing Loans 90 or More Days Past Due	8,223
Construction Loans [Member]
Financing Receivable, Past Due [Line Items]
Total loans	1,772,416	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	2,558,670	2,460,726
Accruing Loans 90 or More Days Past Due	2,954
Consumer Loan [Member]
Financing Receivable, Past Due [Line Items]
Total loans	462,882	$ 476,962
Accruing Loans 90 or More Days Past Due	253
Financing Receivables, 30 to 89 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	101,206
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	34,328
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	2,349
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	43,836
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	891
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	13,913
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	5,889
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	67,989
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	25,713
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	24,375
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	11,206
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	6,442
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	253
Financial Asset, Past Due
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	169,195
Financial Asset, Past Due | Commercial Portfolio Segment [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	60,041
Financial Asset, Past Due | Commercial and Industrial Total Energy Loans [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	26,724
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	55,042
Financial Asset, Past Due | Construction Loans [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	891
Financial Asset, Past Due | Total consumer real estate loans [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	20,355
Financial Asset, Past Due | Consumer Loan [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	6,142
Financial Asset, Not Past Due
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	19,219,011
Financial Asset, Not Past Due | Commercial Portfolio Segment [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	6,048,095
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	911,156
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	7,493,180
Financial Asset, Not Past Due | Construction Loans [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	1,771,525
Financial Asset, Not Past Due | Total consumer real estate loans [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	2,538,315
Financial Asset, Not Past Due | Consumer Loan [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	$ 456,740

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	Mar. 31, 2024	Dec. 31, 2023	Mar. 31, 2023
Financing Receivable, Troubled Debt Restructuring [Line Items]
Loans, net of unearned discounts	$ 19,388,206	$ 18,824,251
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	32,781		$ 0
Commercial Portfolio Segment [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Loans, net of unearned discounts	6,108,136	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	28,900		0
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	13,644		0
Commercial Real Estate Buildings Land And Other Loans [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Loans, net of unearned discounts	7,548,222	$ 7,301,920
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	$ 19,137		$ 0

Loans Loans - Weighted Average

Loans Loans - Weighted Average Risk Grade for All Commercial Loans by Class and Year of Origination (Details) $ in Thousands	Mar. 31, 2024 USD ($) Grade	Dec. 31, 2023 USD ($) Grade
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Net of Deferred Income	$ 19,388,206	$ 18,824,251
Commercial Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	878,780
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	873,069
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	710,133
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	462,165
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	346,689
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	372,114
Financing Receivable, Revolving	2,386,818
Loans and Leases Receivable, Net of Deferred Income	$ 6,108,136	$ 5,967,182
Weighted Average Risk Grade For Loans | Grade	6.67	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	$ 227,603
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	35,251
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	58,965
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	70,932
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	4,612
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	10,951
Financing Receivable, Revolving	521,034
Loans and Leases Receivable, Net of Deferred Income	$ 937,880	$ 936,737
Weighted Average Risk Grade For Loans | Grade	6	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	$ 408,729
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	1,560,879
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	1,745,471
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	1,302,714
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	798,561
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	1,390,645
Financing Receivable, Revolving	243,671
Loans and Leases Receivable, Net of Deferred Income	$ 7,548,222	$ 7,301,920
Weighted Average Risk Grade For Loans | Grade	7.26	7.20
Construction Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	$ 242,949
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	440,037
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	598,799
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	289,714
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	28,028
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	1,353
Financing Receivable, Revolving	171,536
Loans and Leases Receivable, Net of Deferred Income	$ 1,772,416	$ 1,680,724
Weighted Average Risk Grade For Loans | Grade	7.56	7.45
Commercial Real Estate Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	$ 651,678
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	2,000,916
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	2,344,270
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	1,592,428
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	826,589
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	1,391,998
Financing Receivable, Revolving	415,207
Loans and Leases Receivable, Net of Deferred Income	$ 9,320,638	$ 8,982,644
Weighted Average Risk Grade For Loans | Grade	7.32	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	$ 788,259
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	799,207
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	640,565
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	413,197
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	331,143
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	343,646
Financing Receivable, Revolving	2,103,487
Loans and Leases Receivable, Net of Deferred Income	$ 5,469,589	$ 5,507,878
Weighted Average Risk Grade For Loans | Grade	6.28	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	$ 222,335
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	32,898
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	53,057
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	69,990
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	4,467
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	5,496
Financing Receivable, Revolving	480,392
Loans and Leases Receivable, Net of Deferred Income	$ 876,532	$ 871,221
Weighted Average Risk Grade For Loans | Grade	5.69	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	$ 408,058
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	1,515,706
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	1,569,318
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	1,195,050
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	726,365
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	1,285,229
Financing Receivable, Revolving	128,573
Loans and Leases Receivable, Net of Deferred Income	$ 6,925,310	$ 6,895,358
Weighted Average Risk Grade For Loans | Grade	7.04	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	$ 227,895
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	433,679
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	520,522
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	187,481
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	28,028
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	1,353
Financing Receivable, Revolving	166,140
Loans and Leases Receivable, Net of Deferred Income	$ 1,565,098	$ 1,526,086
Weighted Average Risk Grade For Loans | Grade	7.29	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	$ 41,562
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	43,457
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	43,429
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	6,436
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	5,063
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	17,960
Financing Receivable, Revolving	89,123
Loans and Leases Receivable, Net of Deferred Income	$ 252,038	$ 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	2,353
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	3,814
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	897
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	0
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	437
Financing Receivable, Revolving	17,700
Loans and Leases Receivable, Net of Deferred Income	$ 25,255	$ 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	$ 613
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	7,036
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	108,049
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	68,104
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	9,145
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	37,054
Financing Receivable, Revolving	110,533
Loans and Leases Receivable, Net of Deferred Income	$ 341,075	$ 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	$ 1,499
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	6,358
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	30,611
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	76,103
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	5,396
Loans and Leases Receivable, Net of Deferred Income	$ 119,967	$ 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	$ 25,688
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	5,250
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	5,278
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	15,136
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	2,927
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	4,848
Financing Receivable, Revolving	100,864
Loans and Leases Receivable, Net of Deferred Income	$ 160,698	$ 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	27
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	0
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	734
Financing Receivable, Revolving	1,129
Loans and Leases Receivable, Net of Deferred Income	$ 1,890	$ 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	$ 0
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	6,048
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	35,944
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	15,690
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	48,851
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	15,918
Financing Receivable, Revolving	3,709
Loans and Leases Receivable, Net of Deferred Income	$ 126,160	$ 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	$ 13,555
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	0
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	12,299
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	15,000
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	$ 40,854	$ 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	$ 23,260
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	23,096
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	20,467
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	24,455
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	6,621
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	2,941
Financing Receivable, Revolving	91,166
Loans and Leases Receivable, Net of Deferred Income	$ 200,365	$ 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	2,094
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	18
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	89
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	2,963
Financing Receivable, Revolving	18,311
Loans and Leases Receivable, Net of Deferred Income	$ 23,910	$ 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	$ 58
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	12,277
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	28,800
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	20,214
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	14,200
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	49,260
Financing Receivable, Revolving	856
Loans and Leases Receivable, Net of Deferred Income	$ 125,665	$ 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	35,367
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	$ 46,497	$ 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	$ 11
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	1,257
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	250
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	2,937
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	924
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	2,719
Financing Receivable, Revolving	450
Loans and Leases Receivable, Net of Deferred Income	$ 20,327	$ 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	$ 5,268
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	802
Loans and Leases Receivable, Net of Deferred Income	$ 7,593	$ 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	$ 0
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	15,663
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	3,237
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	3,656
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	0
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	3,184
Financing Receivable, Revolving	0
Loans and Leases Receivable, Net of Deferred Income	$ 25,740	$ 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	802
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	1,728
Loans and Leases Receivable, Net of Deferred Income	$ 5,119	$ 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	4,149
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	123
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	$ 4,272	$ 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	6.54
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	5.76
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	8.24
Revolving Credit Facility [Member] | Construction Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade For Loans | Grade	7.27
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	7.84
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	$ 78,368
Weighted Average Risk Grade For Loans | Grade	8.53
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	$ 8,532
Weighted Average Risk Grade For Loans | Grade	7.27
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	$ 97,552
Weighted Average Risk Grade For Loans | Grade	6.71
Revolving Loans Converted to Term [Member] | Construction Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Revolving, Converted to Term Loan	$ 0
Weighted Average Risk Grade For Loans | Grade	0
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	$ 97,552
Weighted Average Risk Grade For Loans | Grade	6.71
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	$ 50,085
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	7,897
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	97,011
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	0
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	5,008
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	54
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	541
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	707
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	8,359
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	435
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	11,779
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	2,430
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	6.52
2024 [Member] | Commercial and Industrial Total Energy Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade For Loans | Grade	5.89
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
2024 [Member] | Construction Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade For Loans | Grade	7.46
2024 [Member] | Commercial Real Estate Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade For Loans | Grade	7.17
2023 [Member] | Commercial Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade For Loans | Grade	6.91
2023 [Member] | Commercial and Industrial Total Energy Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade For Loans | Grade	6.95
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	7.27
2023 [Member] | Construction Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade For Loans | Grade	7.39
2023 [Member] | Commercial Real Estate Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade For Loans | Grade	7.30
2022 [Member] | Commercial Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade For Loans | Grade	7.13
2022 [Member] | Commercial and Industrial Total Energy Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade For Loans | Grade	7.17
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	7.30
2022 [Member] | Construction Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade For Loans | Grade	7.70
2022 [Member] | Commercial Real Estate Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade For Loans | Grade	7.40
2021 [Member] | Commercial Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade For Loans | Grade	7.30
2021 [Member] | Commercial and Industrial Total Energy Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade For Loans | Grade	5.98
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	7.35
2021 [Member] | Construction Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade For Loans | Grade	8.28
2021 [Member] | Commercial Real Estate Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade For Loans | Grade	7.52
2020 [Member] | Commercial Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade For Loans | Grade	5.82
2020 [Member] | Commercial and Industrial Total Energy Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade For Loans | Grade	6.37
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	7.24
2020 [Member] | Construction Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade For Loans | Grade	2.54
2020 [Member] | Commercial Real Estate Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade For Loans | Grade	7.08
Prior Years [Member] | Commercial Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade For Loans | Grade	6.09
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	8.90
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	7.09
Prior Years [Member] | Construction Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade For Loans | Grade	6.82
Prior Years [Member] | Commercial Real Estate Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade For Loans | Grade	7.09

Loans - Weighted Average Risk G

Loans - Weighted Average Risk Grades for All Commercial Loans by Class (Detail) $ in Thousands	Mar. 31, 2024 USD ($) Grade	Dec. 31, 2023 USD ($) Grade
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Net of Deferred Income	$ 19,388,206	$ 18,824,251
Commercial Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade | Grade	6.67	6.60
Loans and Leases Receivable, Net of Deferred Income	$ 6,108,136	$ 5,967,182
Commercial and Industrial Total Energy Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade | Grade	6	6.05
Loans and Leases Receivable, Net of Deferred Income	$ 937,880	$ 936,737
Commercial Real Estate Buildings Land And Other Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade | Grade	7.26	7.20
Loans and Leases Receivable, Net of Deferred Income	$ 7,548,222	$ 7,301,920
Construction Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade | Grade	7.56	7.45
Loans and Leases Receivable, Net of Deferred Income	$ 1,772,416	$ 1,680,724
Commercial Real Estate Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade | Grade	7.32	7.24
Loans and Leases Receivable, Net of Deferred Income	$ 9,320,638	$ 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	6.28	6.32
Loans and Leases Receivable, Net of Deferred Income	$ 5,469,589	$ 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	5.69	5.73
Loans and Leases Receivable, Net of Deferred Income	$ 876,532	$ 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	7.04	7.03
Loans and Leases Receivable, Net of Deferred Income	$ 6,925,310	$ 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	7.29	7.27
Loans and Leases Receivable, Net of Deferred Income	$ 1,565,098	$ 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	$ 252,038	$ 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	$ 25,255	$ 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	$ 341,075	$ 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	$ 119,967	$ 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	$ 160,698	$ 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	$ 1,890	$ 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	$ 126,160	$ 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	$ 40,854	$ 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	$ 200,365	$ 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	$ 23,910	$ 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	$ 125,665	$ 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	$ 46,497	$ 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	$ 20,327	$ 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	$ 7,593	$ 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	$ 25,740	$ 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	$ 5,119	$ 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	$ 4,272	$ 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	Mar. 31, 2024	Dec. 31, 2023
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Net of Deferred Income	$ 19,388,206	$ 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	2,558,670	2,460,726
Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Net of Deferred Income	462,882	$ 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	101,206
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	13,913
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	5,889
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	67,989
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	6,442
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	253
Financial Asset, Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	169,195
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	20,355
Financial Asset, Past Due | Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	6,142
Financial Asset, Not Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	19,219,011
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	2,538,315
Financial Asset, Not Past Due | Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	456,740
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	798,935
Revolving Credit Facility [Member] | Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Net of Deferred Income	325,342
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	5,159
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	2,835
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	805
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	101
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	5,964
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	2,936
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	792,971
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	322,406
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	11,180
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	22,680
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	969
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	64
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	3,018
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	13
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	3,987
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	77
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	7,193
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	22,603
2024 [Member] | Total consumer real estate loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Net of Deferred Income	111,517
2024 [Member] | Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Net of Deferred Income	32,191
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	0
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	2,013
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	72
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	0
2024 [Member] | Financial Asset, Past Due | Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	2,085
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	111,517
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	30,106
2023 [Member] | Total consumer real estate loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Net of Deferred Income	582,420
2023 [Member] | Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Net of Deferred Income	47,379
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	1,216
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	600
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	366
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	1,582
2023 [Member] | Financial Asset, Past Due | Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	600
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	580,838
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	46,779
2022 [Member] | Total consumer real estate loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Net of Deferred Income	426,295
2022 [Member] | Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Net of Deferred Income	25,369
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	1,811
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	200
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	606
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	55
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	2,417
2022 [Member] | Financial Asset, Past Due | Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	255
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	423,878
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	25,114
2021 [Member] | Total consumer real estate loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Net of Deferred Income	274,406
2021 [Member] | Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Net of Deferred Income	4,784
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	1,601
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	75
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	390
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	0
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	1,991
2021 [Member] | Financial Asset, Past Due | Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	75
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	272,415
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	4,709
2020 [Member] | Total consumer real estate loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Net of Deferred Income	165,510
2020 [Member] | Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Net of Deferred Income	3,130
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	767
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	68
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	207
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	974
2020 [Member] | Financial Asset, Past Due | Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	68
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	164,536
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	3,062
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	188,407
Prior Years [Member] | Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Net of Deferred Income	2,007
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	2,390
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	34
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	1,050
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	12
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	3,440
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	46
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	184,967
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	$ 1,961

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
	Mar. 31, 2024	Mar. 31, 2023
Accounts, Notes, Loans and Financing Receivable [Line Items]
Remaining Revolving Loans Converted to Term During Period	$ 27,909	$ 25,974
Commercial Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Remaining Revolving Loans Converted to Term During Period	20,972	15,490
Commercial and Industrial Total Energy Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Remaining Revolving Loans Converted to Term During Period	44	3,435
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	3,081	0
Construction Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Remaining Revolving Loans Converted to Term During Period	0	0
Total consumer real estate loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Remaining Revolving Loans Converted to Term During Period	792	707
Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Remaining Revolving Loans Converted to Term During Period	$ 3,020	$ 6,342

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	Mar. 31, 2024	Dec. 31, 2023	Mar. 31, 2023	Dec. 31, 2022
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, Allowance for Credit Loss	$ 250,297	$ 245,996
Commercial Portfolio Segment [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, Allowance for Credit Loss	75,596	74,006	$ 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	14,218	17,814	19,191	18,062
Commercial Real Estate Portfolio Segment [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, Allowance for Credit Loss	138,224	130,598	115,693	90,301
Total consumer real estate loans [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, Allowance for Credit Loss	13,857	13,538	9,708	8,004
Consumer Loan [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, Allowance for Credit Loss	8,402	10,040	8,457	7,017
Loans Receivable [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, Allowance for Credit Loss	250,297	245,996	$ 231,514	$ 227,621
Modeled Expected Credit Losses [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, Allowance for Credit Loss	97,503	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	52,835	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	5,471	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	20,199	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	12,705	12,364
Modeled Expected Credit Losses [Member] | Consumer Loan [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, Allowance for Credit Loss	6,293	5,969
Q-factor adjustments [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, Allowance for Credit Loss	139,995	144,897
Q-factor adjustments [Member] | Commercial Portfolio Segment [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, Allowance for Credit Loss	17,642	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	6,047	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	113,753	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	444	433
Q-factor adjustments [Member] | Consumer Loan [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, Allowance for Credit Loss	2,109	4,071
Specific Valuation Allowances [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, Allowance for Credit Loss	12,799	8,526
Specific Valuation Allowances [Member] | Commercial Portfolio Segment [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, Allowance for Credit Loss	5,119	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	4,272	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	708	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
	Mar. 31, 2024	Mar. 31, 2023
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning balance	$ 245,996
Ending balance	250,297
Commercial Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning balance	74,006	$ 104,237
Credit loss, expense (reversal)	1,992	(20,684)
Charge-offs	(2,144)	(6,180)
Recoveries	1,742	1,092
Net charge-offs	(402)	(5,088)
Ending balance	75,596	78,465
Commercial and Industrial Total Energy Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning balance	17,814	18,062
Credit loss, expense (reversal)	(3,776)	966
Charge-offs	0	0
Recoveries	180	163
Net charge-offs	180	163
Ending balance	14,218	19,191
Commercial Real Estate Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning balance	130,598	90,301
Credit loss, expense (reversal)	7,610	25,361
Charge-offs	0	0
Recoveries	16	31
Net charge-offs	16	31
Ending balance	138,224	115,693
Total consumer real estate loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning balance	13,538	8,004
Credit loss, expense (reversal)	1,806	1,283
Charge-offs	(1,669)	(250)
Recoveries	182	671
Net charge-offs	(1,487)	421
Ending balance	13,857	9,708
Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning balance	10,040	7,017
Credit loss, expense (reversal)	4,018	5,749
Charge-offs	(8,257)	(6,942)
Recoveries	2,601	2,633
Net charge-offs	(5,656)	(4,309)
Ending balance	8,402	8,457
Loans Receivable [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning balance	245,996	227,621
Credit loss, expense (reversal)	11,650	12,675
Charge-offs	(12,070)	(13,372)
Recoveries	4,721	4,590
Net charge-offs	(7,349)	(8,782)
Ending balance	$ 250,297	$ 231,514

Loans - Financing Receivable, G

Loans - Financing Receivable, Gross Charge-Offs By Year of Origination (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Commercial Portfolio Segment [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	$ 878,780
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	873,069
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	710,133
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	462,165
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	346,689
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	372,114
Financing Receivable, Revolving	2,386,818
Financing Receivable, Allowance for Credit Loss, Writeoff	2,144	$ 6,180
Commercial and Industrial Total Energy Loans [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	227,603
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	35,251
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	58,965
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	70,932
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	4,612
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	10,951
Financing Receivable, Revolving	521,034
Financing Receivable, Allowance for Credit Loss, Writeoff	0	0
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	408,729
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	1,560,879
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	1,745,471
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	1,302,714
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	798,561
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	1,390,645
Financing Receivable, Revolving	243,671
Financing Receivable, Allowance for Credit Loss, Writeoff	0
Construction Loans [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	242,949
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	440,037
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	598,799
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	289,714
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	28,028
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	1,353
Financing Receivable, Revolving	171,536
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	1,669	250
Consumer Loan [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, Allowance for Credit Loss, Writeoff	8,257	6,942
Loans Receivable [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, Allowance for Credit Loss, Writeoff	12,070	$ 13,372
Nonperforming Financial Instruments [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	5,279
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	21,871
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	3,754
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	6,597
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	1,029
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	9,936
Financing Receivable, Revolving	5,680
Financing Receivable, Revolving, Converted to Term Loan	17,369
Nonperforming Financial Instruments [Member] | Commercial Portfolio Segment [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	11
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	2,059
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	394
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	2,941
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	935
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	2,719
Financing Receivable, Revolving	2,178
Financing Receivable, Revolving, Converted to Term Loan	14,209
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	5,268
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	3,502
Financing Receivable, Revolving, Converted to Term Loan	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	0
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	19,812
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	3,360
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	3,656
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	0
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	3,184
Financing Receivable, Revolving	0
Financing Receivable, Revolving, Converted to Term Loan	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
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
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
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	38
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	2,712
Financing Receivable, Revolving	0
Financing Receivable, Revolving, Converted to Term Loan	3,014
Nonperforming Financial Instruments [Member] | Consumer Loan [Member]
Financing Receivable, Allowance for Credit Loss [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
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	1,958
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	5,639
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	784
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	696
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	10
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	327
Financing Receivable, Revolving	2,365
Financing Receivable, Revolving, Converted to Term Loan	291
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
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	96
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	572
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	439
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	6
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	13
Financing Receivable, Revolving	794
Financing Receivable, Revolving, Converted to Term Loan	224
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
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
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
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
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
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
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
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	0
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	148
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	253
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	0
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	280
Financing Receivable, Revolving	921
Financing Receivable, Revolving, Converted to Term Loan	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	1,958
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	5,543
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	64
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	4
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	4
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	34
Financing Receivable, Revolving	650
Financing Receivable, Revolving, Converted to Term Loan	$ 0

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	Mar. 31, 2024	Dec. 31, 2023
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Net of Deferred Income	$ 19,388,206	$ 18,824,251
Commercial Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Net of Deferred Income	6,108,136	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	937,880	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	7,548,222	7,301,920
Construction Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Net of Deferred Income	1,772,416	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	2,558,670	2,460,726
Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Net of Deferred Income	462,882	476,962
Specific Valuation Allowances [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Specific Allocations	12,799	8,526
Specific Valuation Allowances [Member] | Commercial Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Specific Allocations	5,119	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	4,272	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	708	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	69,685	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	24,743	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	10,147	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	29,211	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	5,584	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	Mar. 31, 2024	Dec. 31, 2023
Deposit [Line Items]
Non-interest-bearing demand deposits	$ 13,754,985	$ 14,926,094
Interest-bearing Domestic Deposit, Savings	9,994,133	10,512,637
Interest-bearing Domestic Deposit, Money Market	11,072,561	10,997,279
Interest-bearing Domestic Deposit, Time Deposits	5,984,807	5,484,558
Total interest-bearing deposit	27,051,501	26,994,474
Total deposits	$ 40,806,486	$ 41,920,568

Deposits - Additional Informati

Deposits - Additional Information About Corporation's Deposits (Detail) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Deposit Liability [Line Items]
Deposits from foreign sources (primarily Mexico)	$ 1,087,494	$ 1,061,701
Non-interest-bearing public funds deposits	13,754,985	14,926,094
Interest-bearing public funds deposits	27,051,501	26,994,474
Total deposits not covered by deposit insurance	21,378,776	22,393,786
Time deposits not covered by deposit insurance	2,606,127	2,339,716
Public Funds [Member]
Deposit Liability [Line Items]
Non-interest-bearing public funds deposits	442,355	675,016
Interest-bearing public funds deposits	$ 697,824	$ 630,455

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 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	8,100	$ 8,300
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	278,400		$ 280,500
Other Liabilities [Member]
Operating Lease, Liability	$ 315,000		$ 316,400

Commitments and Contingencies_2

Commitments and Contingencies - Financial Instruments with Off-Balance-Sheet Risk (Detail) - USD ($) $ in Thousands	Mar. 31, 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	$ 416,084	$ 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	2,750	2,912
Commitments to Extend Credit [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Financial instruments with off- balance-sheet risk	$ 12,027,630	$ 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
	Mar. 31, 2024	Mar. 31, 2023
Commitments and Contingencies Disclosure [Abstract]
Off-Balance Sheet, Credit Loss, Liability	$ 51,751	$ 58,593
Credit loss expense (benefit)	2,000	(3,675)
Off-Balance Sheet, Credit Loss, Liability	$ 53,751	$ 54,918

Commitments and Contingencies_3

Commitments and Contingencies Commitments and Contingencies - Components of Lease Commitments Expense (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Commitments and Contingencies Disclosure [Abstract]
Operating Lease, Right-of-Use Asset, Amortization Expense	$ 8,790	$ 8,765
Short-term lease expense	325	409
Non-lease components (including taxes, insurance, common maintenance, etc.)	3,549	3,381
Total operating lease expense, excluding rent	$ 12,664	$ 12,555

Capital and Regulatory Matter_2

Capital and Regulatory Matters - Additional Information (Detail) $ / shares in Units, $ in Thousands			3 Months Ended		12 Months Ended
	Jan. 24, 2024 USD ($)	Nov. 19, 2020 USD ($)	Mar. 31, 2024 USD ($) quarter $ / shares shares	Mar. 31, 2023 USD ($) shares	Dec. 31, 2023 USD ($) $ / shares shares
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
CECL Transition Amount			$ 15,400		$ 30,800
Treasury Stock, Shares, Acquired | shares			18,193	9,183
Purchase of treasury stock (289,149 shares QTD and 298,332 shares YTD in 2023 and 7,459 shares YTD in 2022)			$ 2,073	$ 1,173
Maximum dividends available without prior regulatory approval			$ 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
Preferred Stock, Aggregate Liquidation Preference, Value			$ 150,000
Preferred stock, par value | $ / shares			$ 0.01		$ 0.01
Preferred Stock, Liquidation Preference Per Share | $ / shares			$ 1,000		$ 1,000
Number of Preferred Stock equivalent depositary shares | shares			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
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
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
prior stock repurchase plans | Treasury Stock, Common
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Treasury Stock, Shares, Acquired | shares			0
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			0
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		$ 60,000

Capital and Regulatory Matter_3

Capital and Regulatory Matters - Actual and Required Capital Ratios (Detail) - USD ($) $ in Thousands	Mar. 31, 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	$ 4,102,330	$ 4,036,945
Common Equity Tier 1 to Risk-Weighted Assets, Actual , Ratio	13.41%	13.25%
Common Equity Tier 1 to Risk-Weighted Assets, Minimum Capital Required Plus Capital Conservation Buffer, Capital Amount	$ 2,140,804	$ 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	$ 4,247,782	$ 4,182,397
Tier 1 Capital to Risk-Weighted Assets, Actual, Ratio	13.89%	13.73%
Tier 1 Capital to Risk-Weighted Assets, Minimum Capital Required Plus Capital Conservation Buffer, Capital Amount	$ 2,599,548	$ 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	$ 1,834,975	$ 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	$ 4,694,792	$ 4,625,760
Total Capital to Risk-Weighted Assets, Actual, Ratio	15.35%	15.18%
Total Capital to Risk-Weighted Assets, Minimum Capital Required Plus Capital Conservation Buffer, Capital Amount	$ 3,211,206	$ 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	$ 3,058,292	$ 3,046,452
Total Capital to Risk-Weighted Assets, Required to be Considered Well Capitalized, Ratio	10%	10%
Leverage Ratio, Actual, Capital Amount	$ 4,247,782	$ 4,182,397
Leverage Ratio, Actual, Ratio	8.44%	8.35%
Leverage Ratio, Minimum Capital Required Plus Capital Conservation Buffer, Capital Amount	$ 2,012,280	$ 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	$ 4,146,611	$ 4,057,111
Common Equity Tier 1 to Risk-Weighted Assets, Actual , Ratio	13.57%	13.33%
Common Equity Tier 1 to Risk-Weighted Assets, Minimum Capital Required Plus Capital Conservation Buffer, Capital Amount	$ 2,138,279	$ 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	$ 1,985,545	$ 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	$ 4,146,611	$ 4,057,111
Tier 1 Capital to Risk-Weighted Assets, Actual, Ratio	13.57%	13.33%
Tier 1 Capital to Risk-Weighted Assets, Minimum Capital Required Plus Capital Conservation Buffer, Capital Amount	$ 2,596,482	$ 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	$ 2,443,748	$ 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	$ 4,433,621	$ 4,320,474
Total Capital to Risk-Weighted Assets, Actual, Ratio	14.51%	14.20%
Total Capital to Risk-Weighted Assets, Minimum Capital Required Plus Capital Conservation Buffer, Capital Amount	$ 3,207,419	$ 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	$ 3,054,685	$ 3,042,548
Total Capital to Risk-Weighted Assets, Required to be Considered Well Capitalized, Ratio	10%	10%
Leverage Ratio, Actual, Capital Amount	$ 4,146,611	$ 4,057,111
Leverage Ratio, Actual, Ratio	8.24%	8.10%
Leverage Ratio, Minimum Capital Required Plus Capital Conservation Buffer, Capital Amount	$ 2,011,864	$ 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	$ 2,514,830	$ 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	Mar. 31, 2024	Dec. 31, 2023
Derivative [Line Items]
Weighted-average strike rate for outstanding interest rate caps	3.56%
Approximate credit exposure related to swaps with bank customers	$ 23,500
Cash collateral for borrowed securities deposited with other financial institutions	420
Interest rate swaps with upstream financial institution counterparties [Member]
Derivative [Line Items]
Approximate credit exposure related to swaps with bank customers	1,000
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	Mar. 31, 2024	Dec. 31, 2023
Financial institution counterparties Loan/lease interest rate swaps assets [Member]
Derivatives, Fair Value [Line Items]
Forward Contracts – Assets Notional Amount	$ 1,224,589	$ 1,040,659
Estimated Fair Value	69,640	58,486
Financial institution counterparties Loan/lease interest rate swaps liabilities [Member]
Derivatives, Fair Value [Line Items]
Forward Contracts – Liability Notional Amount	538,648	617,266
Estimated Fair Value	(9,899)	(20,293)
Financial institution counterparties Loan/lease interest-rate caps assets [Member]
Derivatives, Fair Value [Line Items]
Forward Contracts – Assets Notional Amount	243,648	275,000
Estimated Fair Value	11,177	11,747
Customer counterparties Loan/lease interest rate swaps assets [Member]
Derivatives, Fair Value [Line Items]
Forward Contracts – Assets Notional Amount	538,648	617,266
Estimated Fair Value	9,899	20,482
Customer counterparties Loan/lease interest rate swaps liabilities [Member]
Derivatives, Fair Value [Line Items]
Forward Contracts – Liability Notional Amount	1,224,589	1,040,659
Estimated Fair Value	(69,639)	(58,485)
Customer counterparties Loan/lease interest rate caps liabilities [Member]
Derivatives, Fair Value [Line Items]
Forward Contracts – Liability Notional Amount	243,648	275,000
Estimated Fair Value	$ (11,177)	$ (11,747)

Derivative Financial Instrume_5

Derivative Financial Instruments - Schedule of Weighted-Average Rates Paid and Received for Interest Rate Swaps Outstanding (Detail)	Mar. 31, 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	4.91%
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	5.01%
Customer Counterparties [Member] | Weighted Average Interest Rate Paid [Member]
Short-duration insurance contracts, discounted liabilities [Line Items]
Non-hedging interest rate swaps – customer counterparties	5.01%
Customer Counterparties [Member] | Weighted-Average Interest Rate Received [Member]
Short-duration insurance contracts, discounted liabilities [Line Items]
Non-hedging interest rate swaps – customer counterparties	4.91%

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	Mar. 31, 2024 USD ($) bbl MMBTU	Dec. 31, 2023 USD ($) bbl MMBTU
Financial Institution Counterparties [Member] | Oil Commodity Derivative [Member]
Derivative Instruments [Line Items]
Oil/Natural Gas Derivative Assets, Notional Amount | bbl	3,666	5,601
Oil/Natural Gas Derivative Liabilities, Notional Amount | bbl	6,183	4,581
Oil/Natural Gas Derivative Assets, Estimated Fair Value	$ 11,866	$ 37,667
Oil/Natural Gas Derivative Liabilities, Estimated Fair Value	$ (29,196)	$ (18,500)
Financial Institution Counterparties [Member] | Natural Gas Commodity Derivative [Member]
Derivative Instruments [Line Items]
Oil/Natural Gas Derivative Assets, Notional Amount | MMBTU	15,537	17,363
Oil/Natural Gas Derivative Liabilities, Notional Amount | MMBTU	5,593	6,462
Oil/Natural Gas Derivative Assets, Estimated Fair Value	$ 10,208	$ 11,822
Oil/Natural Gas Derivative Liabilities, Estimated Fair Value	$ (1,715)	$ (2,499)
Customer Counterparties [Member] | Oil Commodity Derivative [Member]
Derivative Instruments [Line Items]
Oil/Natural Gas Derivative Assets, Notional Amount | bbl	6,382	4,618
Oil/Natural Gas Derivative Liabilities, Notional Amount | bbl	3,468	5,564
Oil/Natural Gas Derivative Assets, Estimated Fair Value	$ 29,855	$ 18,722
Oil/Natural Gas Derivative Liabilities, Estimated Fair Value	$ (11,656)	$ (36,877)
Customer Counterparties [Member] | Natural Gas Commodity Derivative [Member]
Derivative Instruments [Line Items]
Oil/Natural Gas Derivative Assets, Notional Amount | MMBTU	5,593	6,462
Oil/Natural Gas Derivative Liabilities, Notional Amount | MMBTU	15,537	17,363
Oil/Natural Gas Derivative Assets, Estimated Fair Value	$ 1,717	$ 2,499
Oil/Natural Gas Derivative Liabilities, Estimated Fair Value	$ (9,956)	$ (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	Mar. 31, 2024 USD ($)	Mar. 31, 2024 CAD ($)	Mar. 31, 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		$ 125			$ 250
Financial Institution Counterparties [Member] | Other Liabilities [Member] | Non Designated as Hedging Instrument [Member]
Derivative Instruments [Line Items]
Forward Contracts – Liability Notional Amount		125	€ 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	1			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		250	€ 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) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Interest Income on Loans [Member] | Designated as Hedging Instrument [Member] | Commercial Loan/Lease Interest Rate Swaps [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of gain (loss) included in income	$ 0	$ 12

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
	Mar. 31, 2024	Mar. 31, 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)	$ 1,125	$ 710
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)	0	(1)
Commodity Contract [Member]
Other Non Interest Income Non Hedging Interest Rate Derivatives [Line Items]
Amount of gain (loss) included in income (expense)	379	422
Foreign Currency Derivative Contracts [Member]
Other Non Interest Income Non Hedging Interest Rate Derivatives [Line Items]
Amount of gain (loss) included in income (expense)	$ 11	$ 25

Balance Sheet Offsetting - Fina

Balance Sheet Offsetting - Financial Instruments Eligible for Offset Consolidated Balance Sheet (Detail) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Gross Amount Recognized, Derivatives, Financial Assets	$ 102,891	$ 119,723
Gross Amount Offset, Derivatives, Financial assets	0	0
Net Amount Recognized, Derivatives, Financial assets	102,891	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	187,541	204,373
Gross Amount Offset, Financial assets	0	0
Net Amount Recognized, Financial assets	187,541	204,373
Gross Amount Recognized, Derivatives, Financial Liabilities	40,810	41,311
Gross Amount Offset, Derivatives, Financial liabilities	0	0
Net Amount Recognized, Derivatives, Financial liabilities	40,810	41,311
Gross Amount Recognized, Repurchase agreements, Financial liabilities	3,943,207	4,127,188
Gross Amount Offset, Repurchase agreements, Financial liabilities	0	0
Net Amount Recognized, Repurchase agreements, Financial liabilities	3,943,207	4,127,188
Gross Amount Recognized, Financial liabilities	3,984,017	4,168,499
Gross Amount Offset, Financial liabilities	0	0
Net Amount Recognized, Financial Liabilities	3,984,017	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	80,817	70,233
Gross Amount Offset, Derivatives, Financial assets	0	0
Net Amount Recognized, Derivatives, Financial assets	80,817	70,233
Gross Amount Recognized, Derivatives, Financial Liabilities	9,899	20,293
Gross Amount Offset, Derivatives, Financial liabilities	0	0
Net Amount Recognized, Derivatives, Financial liabilities	9,899	20,293
Commodity swaps and options [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Gross Amount Recognized, Derivatives, Financial Assets	22,074	49,489
Gross Amount Offset, Derivatives, Financial assets	0	0
Net Amount Recognized, Derivatives, Financial assets	22,074	49,489
Gross Amount Recognized, Derivatives, Financial Liabilities	30,911	20,999
Gross Amount Offset, Derivatives, Financial liabilities	0	0
Net Amount Recognized, Derivatives, Financial liabilities	$ 30,911	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	Mar. 31, 2024	Dec. 31, 2023
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Net Amount Recognized, Derivatives, Financial Assets	$ 102,891	$ 119,723
Gross Amounts Not Offset, Financial Instruments, Total Derivatives, Financial Assets	(40,475)	(32,431)
Gross Amount Not Offset Collateral, Derivatives, Financial Assets	(61,500)	(84,839)
Net Amount, Derivatives, Financial Assets	916	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	187,541	204,373
Gross Amounts Not Offset Collateral, Financial Assets	(146,150)	(169,489)
Net Amount, Financial Assets	916	2,453
Net Amount Recognized, Derivatives, Financial Liabilities	40,810	41,311
Gross Amounts Not Offset Financial Instruments, Total Derivatives, Financial Liabilities	(40,475)	(32,431)
Gross Amounts Not Offset Collateral, Derivatives, Financial Liabilities	(335)	(8,580)
Net Amount, Derivatives, Financial Liabilities	0	300
Net Amount Recognized, Repurchase Agreements, Financial Liabilities	3,943,207	4,127,188
Gross Amounts Not Offset Financial Instruments, Repurchase Agreements, Financial Liabilities	0	0
Gross Amounts Not Offset Collateral, Repurchase Agreements, Financial Liabilities	(3,943,207)	(4,127,188)
Net Amount, Repurchase Agreements, Financial Liabilities	0	0
Net Amount Recognized, Total Financial Liabilities	3,984,017	4,168,499
Gross Amounts Not Offset Collateral, Financial Liabilities	(3,943,542)	(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	31,738	36,551
Gross Amounts Not Offset, Financial Instruments, Total Derivatives, Financial Assets	(12,183)	(8,870)
Gross Amount Not Offset Collateral, Derivatives, Financial Assets	(19,555)	(27,170)
Net Amount, Derivatives, Financial Assets	0	511
Net Amount Recognized, Derivatives, Financial Liabilities	12,183	8,870
Gross Amounts Not Offset Financial Instruments, Total Derivatives, Financial Liabilities	(12,183)	(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	17,484	31,202
Gross Amounts Not Offset, Financial Instruments, Total Derivatives, Financial Assets	(15,966)	(7,444)
Gross Amount Not Offset Collateral, Derivatives, Financial Assets	(1,136)	(22,954)
Net Amount, Derivatives, Financial Assets	382	804
Net Amount Recognized, Derivatives, Financial Liabilities	15,966	7,444
Gross Amounts Not Offset Financial Instruments, Total Derivatives, Financial Liabilities	(15,966)	(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	22,234	23,829
Gross Amounts Not Offset, Financial Instruments, Total Derivatives, Financial Assets	(2,775)	(5,151)
Gross Amount Not Offset Collateral, Derivatives, Financial Assets	(19,459)	(18,472)
Net Amount, Derivatives, Financial Assets	0	206
Net Amount Recognized, Derivatives, Financial Liabilities	2,775	5,151
Gross Amounts Not Offset Financial Instruments, Total Derivatives, Financial Liabilities	(2,775)	(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	15,519	13,271
Gross Amounts Not Offset, Financial Instruments, Total Derivatives, Financial Assets	(2,228)	(4,548)
Gross Amount Not Offset Collateral, Derivatives, Financial Assets	(13,080)	(8,723)
Net Amount, Derivatives, Financial Assets	211	0
Net Amount Recognized, Derivatives, Financial Liabilities	2,228	4,548
Gross Amounts Not Offset Financial Instruments, Total Derivatives, Financial Liabilities	(2,228)	(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	15,916	14,870
Gross Amounts Not Offset, Financial Instruments, Total Derivatives, Financial Assets	(7,323)	(6,418)
Gross Amount Not Offset Collateral, Derivatives, Financial Assets	(8,270)	(7,520)
Net Amount, Derivatives, Financial Assets	323	932
Net Amount Recognized, Derivatives, Financial Liabilities	7,658	15,298
Gross Amounts Not Offset Financial Instruments, Total Derivatives, Financial Liabilities	(7,323)	(6,418)
Gross Amounts Not Offset Collateral, Derivatives, Financial Liabilities	(335)	(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	Mar. 31, 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	$ 3,943,207	$ 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	3,943,207	4,127,188
Securities Sold under Agreements to Repurchase, Gross	3,943,207	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	2,575,020	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	2,575,020	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	1,368,187	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	$ 1,368,187	$ 826,526

Stock-Based Compensation Stock-

Stock-Based Compensation Stock-Based Compensation - Narrative (Details)	Mar. 31, 2024 shares
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	226,288

Stock-Based Compensation - Summ

Stock-Based Compensation - Summary of Activity in Corporation's Active Stock Plans (Detail) - $ / shares	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock options exercised, Number of Shares	(84,176)	(50,387)
Deferred Stock Units Outstanding
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Beginning Balance, Number of Shares/Units	54,164
Ending Balance, Number of Shares/Units	54,164
Beginning Balance, Weighted-Average Grant-Date Fair Value	$ 89.71
Ending Balance, Weighted-Average Grant-Date Fair Value	$ 89.71
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	2,142
Stock Awards exercised/vested, Number of Shares	(458)
Forfeited/expired, Number of Shares/Units	(427)
Ending Balance, Number of Shares/Units	568,063
Beginning Balance, Weighted-Average Grant-Date Fair Value	$ 99.77
Granted Weighted-Average Grant-Date Fair Value	107.41
Stock Award Exercised/Vested, Weighted Average Grant Date Fair Value	65.43
Forfeited/Expired, Weighted-Average Price	105.40
Ending Balance, Weighted-Average Grant-Date Fair Value	$ 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	(37,900)
Ending Balance, Number of Shares	448,041
Beginning Balance, Weighted-Average Exercise Price	$ 71.25
Stock options exercised, Weighted-Average Exercise Price	76.92
Ending Balance, Weighted-Average Exercise Price	$ 70.77
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
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

Stock-Based Compensation - Shar

Stock-Based Compensation - Shares Issued in Connection with Stock Compensation Awards (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Share-Based Payment Arrangement [Abstract]
New shares issued from available authorized shares	0	49,887
Shares issued from available treasury stock	84,176	500
Proceeds from stock option exercises	$ 2,915	$ 1,500

Stock-Based Compensation - Stoc

Stock-Based Compensation - Stock-Based Compensation Expense (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Payment Arrangement, Expense	$ 3,738	$ 4,742
Income tax benefit	1,145	1,068
Non-Vested Stock Awards/Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted Stock or Unit Expense	3,379	3,307
Performance Stock Units Outstanding
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted Stock or Unit Expense	$ 359	$ 1,435

Stock-Based Compensation - Unre

Stock-Based Compensation - Unrecognized Stock-Based Compensation Expense (Detail) $ in Thousands	Mar. 31, 2024 USD ($)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Non-vested stock units	$ 19,470
Performance stock units	8,072
Total	$ 27,542

Earnings Per Common Share - Bas

Earnings Per Common Share - Basic and Diluted Earnings Per Common Share (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Earnings Per Share [Abstract]
Net income	$ 135,690	$ 177,653
Less: Preferred stock dividends	1,669	1,669
Net income available to common shareholders	134,021	175,984
Less: Earnings allocated to participating securities	1,639	1,807
Distributed earnings allocated to common stock	59,080	56,006
Undistributed earnings allocated to common stock	73,302	118,171
Net earnings allocated to common stock	$ 132,382	$ 174,177
Weighted-average shares outstanding for basic earnings per common share	64,216,323	64,373,563
Dilutive effect of stock compensation	155,408	258,513
Weighted-average shares outstanding for diluted earnings per common share	64,371,731	64,632,076

Defined Benefit Plans Additiona

Defined Benefit Plans Additional Information (Details) $ in Thousands	3 Months Ended
	Mar. 31, 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
	Mar. 31, 2024	Mar. 31, 2023
Retirement Benefits [Abstract]
Expected return on plan assets, net of expenses	$ (2,411)	$ (2,740)
Interest cost on projected benefit obligation	1,662	1,746
Net amortization and deferral	418	870
Net periodic expense (benefit)	$ (331)	$ (124)

Income Taxes - Additional Infor

Income Taxes - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023	Dec. 31, 2023
Income Tax Disclosure [Abstract]
Deferred Tax Assets, Net	$ 374.5		$ 328.3
Valuation allowance	$ 0
U.S. federal statutory income tax rate, percent	21%	21%
Unrecognized tax benefits	$ 0	$ 0

Income Taxes - Income Tax Expen

Income Taxes - Income Tax Expense (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Income Tax Disclosure [Abstract]
Current income tax expense	$ 30,317	$ 34,995
Deferred income tax expense (benefit)	(4,446)	(1,809)
Income tax expense, as reported	$ 25,871	$ 33,186
Effective tax rate	16%	15.70%

Other Comprehensive Income (L_3

Other Comprehensive Income (Loss) - Component of Other Comprehensive Income (Loss) (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Equity [Abstract]
Securities available for sale and transferred securities, Change in net unrealized gain/loss during the period, Before Tax Amount	$ (199,075)	$ 260,269
Securities available for sale and transferred securities, Change in net unrealized gain on securities transferred to held to maturity, Before Tax Amount	(159)	(160)
Securities available for sale and transferred securities, Reclassification adjustment for net (gains) losses included in net income, Before Tax Amount	0	(21)
Total securities available for sale and transferred securities, before tax amount	(199,234)	260,088
Reclassification adjustment for net amortization of actuarial gain/loss included in net income as a component of net periodic cost (benefit), before tax amount	418	870
Total defined-benefit post-retirement benefit plans	418	870
Total other comprehensive income (loss), before tax	(198,816)	260,958
Securities available for sale and transferred securities, Change in net unrealized gain/loss during the period, Tax Expense (Benefit)	(41,806)	54,656
Securities available for sale and transferred securities, Change in net unrealized gain on securities transferred to held to maturity, Tax Expense (Benefit)	(34)	(33)
Securities available for sale and transferred securities, Reclassification adjustment for net (gains) losses included in net income, Tax Expense (Benefit)	0	(4)
Total securities available for sale and transferred securities, Tax Expense (Benefit)	(41,840)	54,619
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
Total defined-benefit post-retirement benefit plans, Tax Expense (Benefit)	88	183
Total other comprehensive income (loss), Tax Expense (Benefit)	(41,752)	54,802
Securities available for sale and transferred securities, Change in net unrealized gain/loss during the period, Net of Tax	(157,269)	205,613
Securities available for sale and transferred securities, Change in net unrealized gain on securities transferred to held to maturity, Net of Tax	(125)	(127)
Securities available for sale and transferred securities, Reclassification adjustment for net (gains) losses included in net income, Net of Tax	0	(17)
Total securities available for sale and transferred securities, Net of Tax	(157,394)	205,469
Reclassification adjustment for net amortization of actuarial gain/lloss included in net income as a component of net periodic cost (benefit), Net of Tax	330	687
Total defined-benefit post-retirement benefit plans, Net of Tax Amount	330	687
Other comprehensive income (loss), net of tax	$ (157,064)	$ 206,156

Other Comprehensive Income - Sc

Other Comprehensive Income - Schedule of Accumulated Other Comprehensive Income, Net of Tax (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning Balance	$ (1,119,219)
Other comprehensive income (loss), net of tax	(157,064)	$ 206,156
Ending Balance	(1,276,283)
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	(157,394)	205,486
Reclassification of amounts included in net income	0	(17)
Other comprehensive income (loss), net of tax	(157,394)	205,469
Ending Balance	(1,252,188)	(1,108,322)
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	330	687
Other comprehensive income (loss), net of tax	330	687
Ending Balance	(24,095)	(33,816)
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	(157,394)	205,486
Reclassification of amounts included in net income	330	670
Other comprehensive income (loss), net of tax	(157,064)	206,156
Ending Balance	$ (1,276,283)	$ (1,142,138)

Operating Segments - Additional

Operating Segments - Additional Information (Detail) - Segment	3 Months Ended
	Mar. 31, 2024	Mar. 31, 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
	Mar. 31, 2024	Mar. 31, 2023
Segment Reporting Information [Line Items]
Interest Income (Expense), Net	$ 390,051	$ 399,820
Credit loss expense	13,650	9,104
Total non-interest income	111,377	105,265
Total non-interest expense	326,217	285,142
Income (loss) before income taxes	161,561	210,839
Income tax expense (benefit)	25,871	33,186
Net income (loss)	135,690	177,653
Preferred stock dividends	1,669	1,669
Net income (loss) available to common shareholders	134,021	175,984
Revenues from (expenses to) external customers	501,428	505,085
Bank
Segment Reporting Information [Line Items]
Interest Income (Expense), Net	391,805	401,318
Credit loss expense	13,650
Total non-interest income	66,380	63,643
Total non-interest expense	286,830	249,865
Income (loss) before income taxes	157,705	205,992
Income tax expense (benefit)	25,635	32,366
Net income (loss)	132,070	173,626
Preferred stock dividends	0	0
Net income (loss) available to common shareholders	132,070	173,626
Revenues from (expenses to) external customers	458,185	464,961
Frost Wealth Advisors [Member]
Segment Reporting Information [Line Items]
Interest Income (Expense), Net	1,669	1,654
Credit loss expense	0
Total non-interest income	45,426	42,038
Total non-interest expense	37,973	33,949
Income (loss) before income taxes	9,122	9,743
Income tax expense (benefit)	1,916	2,046
Net income (loss)	7,206	7,697
Preferred stock dividends	0	0
Net income (loss) available to common shareholders	7,206	7,697
Revenues from (expenses to) external customers	47,095	43,692
Non-Banks [Member]
Segment Reporting Information [Line Items]
Interest Income (Expense), Net	(3,423)	(3,152)
Credit loss expense	0
Total non-interest income	(429)	(416)
Total non-interest expense	1,414	1,328
Income (loss) before income taxes	(5,266)	(4,896)
Income tax expense (benefit)	(1,680)	(1,226)
Net income (loss)	(3,586)	(3,670)
Preferred stock dividends	1,669	1,669
Net income (loss) available to common shareholders	(5,255)	(5,339)
Revenues from (expenses to) external customers	$ (3,852)	$ (3,568)

Fair Value Measurements - Addit

Fair Value Measurements - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 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	Mar. 31, 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	$ 15,181,583	$ 16,578,371
Trading account securities	39,645	31,717
Derivative assets	102,891	119,723
Derivative liabilities	40,810	41,311
Interest rate swaps, caps and floors [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	90,716	90,715
Derivative liabilities	90,715	90,525
Commodity swaps and options [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	53,646	70,710
Derivative liabilities	52,523	69,447
Foreign Exchange Forward [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	1	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	3,872,572	4,927,589
Trading account securities	29,608	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	6,472,625	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	4,793,516	5,011,331
Trading account securities	10,037	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	42,870	42,769
Level 1 [Member] | Foreign Exchange Forward [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	1	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	3,872,572	4,927,589
Trading account securities	29,608	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	90,716	90,715
Derivative liabilities	90,715	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	53,646	70,710
Derivative liabilities	52,523	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	6,472,625	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	4,793,516	5,011,331
Trading account securities	10,037	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	$ 42,870	$ 42,769

Fair Value Measurements - Impai

Fair Value Measurements - Impaired Loans Remeasured and Reported at Fair Value of Underlying Collateral (Detail) - USD ($) $ in Thousands	Mar. 31, 2024	Mar. 31, 2023
Level 2 [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Carrying value of impaired loans before allocations	$ 16,332	$ 368
Impaired Financing Receivable, Related Allowance	(1,589)	0
Loans receivable, fair value disclosure	14,743	368
Level 3 [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Carrying value of impaired loans before allocations	16,182	6,242
Impaired Financing Receivable, Related Allowance	(1,172)	(900)
Loans receivable, fair value disclosure	$ 15,010	$ 5,342

Fair Value Measurements - Estim

Fair Value Measurements - Estimated Fair Values of Financial Instruments (Detail) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023	Mar. 31, 2023	Dec. 31, 2022
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	$ 8,464,517	$ 8,687,276	$ 9,301,774	$ 12,028,132
Securities held to maturity, net of allowance for credit losses of $310 at both March 31, 2024 and December 31, 2023	3,600,729	3,619,428
Loans, net	19,137,909	18,578,255
Deposits	40,806,486	41,920,568
Federal funds purchased	41,200	14,200
Repurchase agreements	3,943,207	4,127,188
Junior subordinated deferrable interest debentures	123,141	123,127
Subordinated notes	99,530	99,491
Carrying Amount [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	8,464,517	8,687,276
Securities held to maturity, net of allowance for credit losses of $310 at both March 31, 2024 and December 31, 2023	3,600,729	3,619,428
Accrued interest receivable	206,090	251,385
Deposits	40,806,486	41,920,568
Federal funds purchased	41,200	14,200
Repurchase agreements	3,943,207	4,127,188
Junior subordinated deferrable interest debentures	123,141	123,127
Subordinated notes	99,530	99,491
Accrued interest payable	65,102	61,222
Carrying Amount [Member] | Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans, net	19,137,909	18,578,255
Estimated Fair Value [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	8,464,517	8,687,276
Securities held to maturity, net of allowance for credit losses of $310 at both March 31, 2024 and December 31, 2023	3,451,316	3,532,044
Accrued interest receivable	206,090	251,385
Deposits	40,792,337	41,903,580
Federal funds purchased	41,200	14,200
Repurchase agreements	3,943,207	4,127,188
Junior subordinated deferrable interest debentures	123,712	123,712
Subordinated notes	96,513	96,071
Accrued interest payable	65,102	61,222
Estimated Fair Value [Member] | Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans, net	$ 18,637,078	$ 18,117,369