Cullen/Frost Bankers (CFR) 10-K 6 Feb 24 2023 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($) $ / shares in Units, $ in Billions	12 Months Ended
	Dec. 31, 2023	Feb. 02, 2024	Jun. 30, 2023	Dec. 31, 2022
Entity Information [Line Items]
Document Type	10-K
Document Annual Report	true
Document Period End Date	Dec. 31, 2023
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2023
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 Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
ICFR Auditor Attestation Flag	true
Document Financial Statement Error Correction [Flag]	false
Entity Shell Company	false
Entity Public Float			$ 6.7
Entity Common Stock, Shares Outstanding		64,202,891
Common Stock, Par or Stated Value Per Share	$ 0.01			$ 0.01
Entity Central Index Key	0000039263
Amendment Flag	false
Document Fiscal Period Focus	FY
Auditor Name	Ernst & Young LLP
Auditor Location	San Antonio, Texas
Auditor Firm ID	42
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	Dec. 31, 2023	Dec. 31, 2022
Assets:
Cash and due from banks	$ 617,569	$ 691,553
Interest-bearing deposits	7,985,057	11,128,902
Federal funds sold	0	120,527
Resell agreements	84,650	87,150
Total cash and cash equivalents	8,687,276	12,028,132
Securities held to maturity, net of allowance for credit losses of $310 in 2023 and $158 in 2022	3,619,428	2,639,083
Securities available for sale, at estimated fair value	16,578,371	18,243,605
Trading account securities	31,717	28,045
Loans, net of unearned discounts	18,824,251	17,154,969
Less: Allowance for credit losses on loans	(245,996)	(227,621)
Net loans	18,578,255	16,927,348
Premises and equipment, net	1,190,033	1,102,695
Accrued interest receivable and other assets	2,159,958	1,923,468
Total assets	50,845,038	52,892,376
Liabilities:
Non-interest-bearing demand deposits	14,926,094	17,598,234
Interest-bearing deposit	26,994,474	26,355,962
Total deposits	41,920,568	43,954,196
Federal funds purchased	14,200	51,650
Repurchase agreements	4,127,188	4,660,641
Junior subordinated deferrable interest debentures, net of unamortized issuance costs	123,127	123,069
Subordinated notes, net of unamortized issuance costs	99,491	99,335
Accrued interest payable and other liabilities	844,017	866,257
Total liabilities	47,128,591	49,755,148
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 in 2023 and 2022	145,452	145,452
Common stock, par value $0.01 per share; 210,000,000 shares authorized; 64,404,582 shares issued in 2023 and 64,354,695 shares issued in 2022	644	643
Additional paid-in capital	1,055,809	1,029,756
Retained earnings	3,657,688	3,309,671
Accumulated other comprehensive income, net of tax	(1,119,219)	(1,348,294)
Treasury stock, at cost; 219,295 shares in 2023	(23,927)	0
Total shareholders’ equity	3,716,447	3,137,228
Total liabilities and shareholders’ equity	$ 50,845,038	$ 52,892,376

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - USD ($)	Dec. 31, 2023	Dec. 31, 2022
Debt Securities, Held-to-maturity, Allowance for Credit Loss	$ (310,000)	$ (158,000)
Common Stock, Par or Stated Value Per Share	$ 0.01	$ 0.01
Common Stock, Shares Authorized	210,000,000	210,000,000
Common Stock, Shares, Issued	64,404,582	64,354,695
Treasury Stock, Common Shares	219,295
Series B Preferred Stock [Member]
Preferred Stock, Par or Stated Value Per Share	$ 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	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Interest income:
Loans, including fees	$ 1,189,377	$ 770,391	$ 674,611
Securities:
Taxable	406,289	249,797	89,550
Tax-exempt	240,131	237,626	226,683
Interest-bearing deposits	376,010	216,367	17,878
Federal funds sold	1,288	948	31
Resell agreements	4,621	592	16
Total interest income	2,217,716	1,475,721	1,008,769
Interest expense:
Deposits	508,255	140,476	14,520
Federal funds purchased	1,524	690	32
Repurchase agreements	135,969	34,443	2,209
Junior subordinated deferrable interest debentures	8,647	4,172	2,484
Subordinated notes	4,657	4,657	4,657
Total interest expense	659,052	184,438	23,902
Net interest income	1,558,664	1,291,283	984,867
Credit loss expense	46,171	3,000	63
Net interest income after credit loss expense	1,512,493	1,288,283	984,804
Non-interest income:
Trust and investment management fees	153,315	154,679	148,994
Service charges on deposit accounts	93,504	91,891	83,292
Insurance commissions and fees	58,271	53,210	51,548
Interchange and card transaction fees	19,419	18,231	17,461
Other charges, commissions and fees	49,026	41,590	36,836
Net gain (loss) on securities transactions	66	0	69
Other	54,941	45,217	48,528
Total non-interest income	428,542	404,818	386,728
Non-interest expense:
Salaries and wages	547,718	492,096	395,497
Employee benefits	115,306	88,608	82,029
Net occupancy	124,396	112,495	107,344
Technology, furniture and equipment	135,286	120,771	112,738
Deposit insurance	76,589	15,603	12,232
Other	229,367	194,701	172,154
Total non-interest expense	1,228,662	1,024,274	881,994
Income before income taxes	712,373	668,827	489,538
Income taxes	114,400	89,677	46,459
Net income	597,973	579,150	443,079
Preferred stock dividends	6,675	6,675	7,157
Net income available to common shareholders	$ 591,298	$ 572,475	$ 435,922
Earnings per common share:
Basic (in dollars per share)	$ 9.11	$ 8.84	$ 6.79
Diluted (in dollars per share)	$ 9.10	$ 8.81	$ 6.76

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Net income	$ 597,973	$ 579,150	$ 443,079
Other comprehensive income (loss), before tax:
Change in net unrealized gain/loss on securities available for sale during the period	277,926	(2,143,567)	(231,355)
Change in net unrealized gain on securities transferred to held-to-maturity	(649)	(737)	(971)
Reclassification adjustment for net (gains) losses included in net income	(66)	0	(69)
Total securities available for sale and transferred securities before tax amount	277,211	(2,144,304)	(232,395)
Defined-benefit post-retirement benefit plans:
Change in the net actuarial gain/loss before tax amount	9,278	(5,005)	16,593
Reclassification adjustment for net amortization of actuarial gain/loss included in net income as a component of net periodic cost (benefit) before tax amount	3,479	2,964	6,116
Total defined-benefit post-retirement benefit plans	12,757	(2,041)	22,709
Reclassification adjustments for (gains) losses included in net income:
Other comprehensive income (loss), before tax	289,968	(2,146,345)	(209,686)
Deferred tax expense (benefit)	60,893	(450,733)	(44,034)
Other comprehensive income (loss), net of tax	229,075	(1,695,612)	(165,652)
Comprehensive income	$ 827,048	$ (1,116,462)	$ 277,427

Consolidated Statement of Chang

Consolidated Statement of Changes in Shareholders' Equity - USD ($) $ in Thousands	Total	Share awards vesting Treasury Stock, Common	Preferred Stock [Member]	Common Stock [Member]	Additional Paid-In Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income (Loss), Net of Tax [Member]	Treasury Stock, Common
Balance at Dec. 31, 2020	$ 4,293,016		$ 145,452	$ 642	$ 997,168	$ 2,750,723	$ 512,970	$ (113,939)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	443,079					443,079
Other comprehensive income, net of tax	(165,652)						(165,652)
Proceeds from stock option exercises/stock unit conversions (267,357 shares, 399,810 shares, and 987,758 shares during 2022, 2021, and 2020, respectively)	54,417					(40,836)		95,253
Stock-based compensation expense recognized in earnings	12,753				12,753
Purchase of treasury stock (436,765 shares, 31,351 shares, and 31,317 shares during 2022, 2021, and 2020, respectively)	(3,864)	$ (3,900)						(3,864)
Treasury Stock issued to the 401(k) stock purchase plan (18,555 shares in 2021)	1,749					(57)		1,806
Cash dividends paid on preferred stock (approximately $44.50 per share which is equivalent to approximately $1.11 per depositary share in 2023 and 2022 and approximately $47.71 per share which is equivalent to approximately $1.19 per share in 2021)	(7,157)					(7,157)
Cash dividends – common stock ($3.58 per share, $3.24 per share, and $2.94 per share in 2022, 2021, and 2020, respectively)	(188,786)					(188,786)
Balance at Dec. 31, 2021	$ 4,439,555		145,452	642	1,009,921	2,956,966	347,318	(20,744)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Treasury Stock, Shares, Acquired	0	31,317
Net income	$ 579,150					579,150
Other comprehensive income, net of tax	(1,695,612)						(1,695,612)
Proceeds from stock option exercises/stock unit conversions (267,357 shares, 399,810 shares, and 987,758 shares during 2022, 2021, and 2020, respectively)	16,659			1	1,513	(9,990)		25,135
Stock-based compensation expense recognized in earnings	18,322				18,322
Purchase of treasury stock (436,765 shares, 31,351 shares, and 31,317 shares during 2022, 2021, and 2020, respectively)	(4,391)	$ (4,400)						(4,391)
Treasury Stock issued to the 401(k) stock purchase plan (18,555 shares in 2021)	0
Cash dividends paid on preferred stock (approximately $44.50 per share which is equivalent to approximately $1.11 per depositary share in 2023 and 2022 and approximately $47.71 per share which is equivalent to approximately $1.19 per share in 2021)	(6,675)					(6,675)
Cash dividends – common stock ($3.58 per share, $3.24 per share, and $2.94 per share in 2022, 2021, and 2020, respectively)	(209,780)					(209,780)
Balance at Dec. 31, 2022	$ 3,137,228		145,452	643	1,029,756	3,309,671	(1,348,294)	0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Treasury Stock, Shares, Acquired	0	31,351
Net income	$ 597,973					597,973
Other comprehensive income, net of tax	229,075						229,075
Proceeds from stock option exercises/stock unit conversions (267,357 shares, 399,810 shares, and 987,758 shares during 2022, 2021, and 2020, respectively)	9,299			1	1,463	(10,958)		18,793
Stock-based compensation expense recognized in earnings	24,590				24,590
Purchase of treasury stock (436,765 shares, 31,351 shares, and 31,317 shares during 2022, 2021, and 2020, respectively)	(42,720)	$ (3,500)						(42,720)
Treasury Stock issued to the 401(k) stock purchase plan (18,555 shares in 2021)	0
Cash dividends paid on preferred stock (approximately $44.50 per share which is equivalent to approximately $1.11 per depositary share in 2023 and 2022 and approximately $47.71 per share which is equivalent to approximately $1.19 per share in 2021)	(6,675)					(6,675)
Cash dividends – common stock ($3.58 per share, $3.24 per share, and $2.94 per share in 2022, 2021, and 2020, respectively)	(232,323)					(232,323)
Balance at Dec. 31, 2023	$ 3,716,447		$ 145,452	$ 644	$ 1,055,809	$ 3,657,688	$ (1,119,219)	$ (23,927)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Treasury Stock, Shares, Acquired	436,765	35,897

Consolidated Statement of Cha_2

Consolidated Statement of Changes in Shareholders' Equity (Parenthetical) - $ / shares	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Stock option exercises/deferred stock unit conversions, shares	267,357	399,810	987,758
Treasury Stock, Shares, Acquired	436,765	0	0
Stock Issued During Period, Shares, Treasury Stock Reissued			18,555
Preferred Stock, Dividends Per Share, Declared	$ 44.50	$ 44.50	$ 47.71
Preferred stock, Dividends equivalent per depositary share, Declared	1.11	1.11	1.19
Common Stock, Dividends, Per Share, Cash Paid	$ 3.58	$ 3.24	$ 2.94
Share awards vesting | Treasury Stock, Common
Treasury Stock, Shares, Acquired	35,897	31,351	31,317

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Operating Activities:
Net income	$ 597,973	$ 579,150	$ 443,079
Adjustments to reconcile net income to net cash from operating activities:
Credit loss expense	46,171	3,000	63
Deferred tax expense (benefit)	(14,829)	(4,918)	7,784
Accretion of loan discounts	(17,724)	(12,921)	(12,890)
Securities premium amortization (discount accretion), net	63,893	97,400	119,242
Net (gain) loss on securities transactions	(66)	0	(69)
Depreciation and amortization	76,442	71,344	69,289
Net (gain) loss on sale/exchange/write-down of assets/foreclosed assets	750	109	(11,578)
Stock-based compensation	24,590	18,322	12,753
Net tax benefit from stock-based compensation	894	4,602	7,877
Earnings on life insurance policies	(2,944)	(2,096)	(2,462)
Net change in:
Trading account securities	(2,220)	(716)	(560)
Lease right-of-use assets	23,573	24,409	23,504
Accrued interest receivable and other assets	(232,665)	(116,243)	(46,560)
Accrued interest payable and other liabilities	(84,993)	61,140	38,821
Net cash provided by (used in) operating activities	478,845	722,582	648,293
Investing Activities:
Securities held to maturity: Purchases	(1,147,624)	(1,424,105)	0
Securities held to maturity: Maturities, calls and principal repayments	162,142	561,388	177,593
Securities available for sale:
Purchases	(19,124,336)	(22,178,248)	(24,217,841)
Sales	1,904,067	0	1,999,891
Maturities, calls and principal repayments	19,103,872	15,683,097	18,425,108
Proceeds from sale of loans	15,851	2,365	0
Net change in loans	(1,701,895)	(824,021)	1,145,924
Benefits received on life insurance policies	1,937	2,047	2,307
Proceeds from sales of premises and equipment	1,282	63	7,044
Purchases of premises and equipment	(158,630)	(102,501)	(65,850)
Proceeds from sales of repossessed properties	583	2,585	809
Net cash provided by (used in) investing activities	(942,751)	(8,277,330)	(2,525,015)
Financing Activities:
Net change in deposits	(2,033,628)	1,258,500	7,679,935
Net change in short-term borrowings	(570,903)	1,945,567	649,727
Principal payments on long-term borrowings	0	0	(13,403)
Proceeds from stock option exercises	9,299	16,659	54,417
Purchase of treasury stock	(42,720)	(4,391)	(3,864)
Cash dividends paid on preferred stock	(6,675)	(6,675)	(7,157)
Cash dividends paid on common stock	(232,323)	(209,780)	(188,786)
Net cash provided by (used in) financing activities	(2,876,950)	2,999,880	8,170,869
Net change in cash and cash equivalents	(3,340,856)	(4,554,868)	6,294,147
Cash and cash equivalents at beginning of year	12,028,132	16,583,000	10,288,853
Cash and cash equivalents at end of year	$ 8,687,276	$ 12,028,132	$ 16,583,000

Summary of Significant Accounti

Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2023
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	Summary of 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 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. We determine whether we have a controlling financial interest in an entity by first evaluating whether the entity is a voting interest entity or a variable interest entity (“VIE”) under accounting principles generally accepted in the United States. Voting interest entities are entities in which the total equity investment at risk is sufficient to enable the entity to finance itself independently and provides the equity holders with the obligation to absorb losses, the right to receive residual returns and the right to make decisions about the entity’s activities. We consolidate voting interest entities in which we have all, or at least a majority of, the voting interest. As defined in applicable accounting standards, VIEs are entities that lack one or more of the characteristics of a voting interest entity. A controlling financial interest in a VIE is present when an enterprise has both the power to direct the activities of the VIE that most significantly impact the VIE’s economic performance and an obligation to absorb losses or the right to receive benefits that could potentially be significant to the VIE. The enterprise with a controlling financial interest, known as the primary beneficiary, consolidates the VIE. Our wholly-owned subsidiary, Cullen/Frost Capital Trust II, is a VIE for which we are not the primary beneficiary and, as such, its accounts are not included in our consolidated financial statements. Acquisitions are accounted for using the purchase method with the operating results of the acquired companies included with our results of operations since their respective dates of acquisition. We have evaluated subsequent events for potential recognition and/or disclosure through the date these consolidated financial statements were issued. 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 credit losses on loans and off-balance-sheet credit exposures, the fair values of financial instruments and the status of contingencies are particularly subject to change. Concentrations and Restrictions on Cash and Cash Equivalents . We maintain deposits with other financial institutions in amounts that exceed federal deposit insurance coverage. Furthermore, federal funds sold are essentially uncollateralized loans to other financial institutions. Management regularly evaluates the credit risk associated with the counterparties to these transactions and believes that we are not exposed to any significant credit risks on cash and cash equivalents. As of December 31, 2023 and 2022, we had $8.6 million and $3.2 million in cash collateral on deposit with other financial institution counterparties to interest rate swap transactions. Cash Flow Reporting . Cash and cash equivalents include cash, deposits with other financial institutions that have an initial maturity of less than 90 days when acquired by us, federal funds sold and resell agreements. Net cash flows are reported for loans, deposit transactions and short-term borrowings. Additional cash flow information was as follows: Year Ended December 31, 2023 2022 2021 Cash paid for interest $ 616,274 $ 169,020 $ 29,003 Cash paid for income tax 118,000 100,000 39,852 Significant non-cash transactions: Exchange of real estate — — 11,036 Unsettled securities transactions 1,452 94,884 27,032 Loans foreclosed and transferred to other real estate owned and foreclosed assets — 239 3,464 Right-of-use lease assets obtained in exchange for lessee operating lease liabilities 15,259 31,787 12,854 Treasury stock issued to 401(k) stock purchase plan — — 1,749 Repurchase/Resell Agreements. We purchase certain securities under agreements to resell. The amounts advanced under these agreements represent short-term loans and are reflected as assets in the accompanying consolidated balance sheets. The securities underlying these agreements are book-entry securities. We also sell certain securities under agreements to repurchase. The agreements are treated as collateralized financing transactions and the obligations to repurchase securities sold are reflected as a liability in the accompanying consolidated balance sheets. The dollar amount of the securities underlying the agreements remains in the asset accounts. Securities. Securities are classified as held to maturity and carried at amortized cost when management has the positive intent and ability to hold them until maturity. Securities to be held for indefinite periods of time are classified as available for sale and carried at fair value, with the unrealized holding gains and losses (those for which no allowance for credit losses are recorded) reported as a component of other comprehensive income, net of tax. Securities held for resale in anticipation of short-term market movements are classified as trading and are carried at fair value, with changes in unrealized holding gains and losses included in income. Management determines the appropriate classification of securities at the time of purchase. Securities with limited marketability, such as stock in the Federal Reserve Bank and the Federal Home Loan Bank, are carried at cost. Interest income on securities includes amortization of purchase premiums and discounts. Premiums and discounts on securities are generally amortized using the interest method with a constant effective yield without anticipating prepayments, except for mortgage-backed securities where prepayments are anticipated. Premiums on callable securities are amortized to their earliest call date. A security is placed on non-accrual status if (i) principal or interest has been in default for a period of 90 days or more or (ii) full payment of principal and interest is not expected. Interest accrued but not received for a security placed on non-accrual status is reversed against interest income. Gains and losses on sales are recorded on the trade date and are derived from the amortized cost of the security sold. Loans . Loans are reported at the principal balance outstanding net of unearned discounts. Interest income on loans is reported on the level-yield method and includes amortization of deferred loan fees and costs over the terms of the individual loans to which they relate, or, in certain cases, over the average expected term for loans where deferred fees and costs are accounted for on a pooled basis. Net loan commitment fees or costs for commitment periods greater than one year are deferred and amortized into fee income or other expense on a straight-line basis over the commitment period. Income on direct financing leases is recognized on a basis that achieves a constant periodic rate of return on the outstanding investment. Further information regarding our accounting policies related to past due loans, non-accrual loans, impaired loans and troubled-debt restructurings is presented in Note 3 - Loans. Allowance For Credit Losses - Held-to-Maturity Securities. The allowance for credit losses on held-to-maturity securities is a contra-asset valuation account, calculated in accordance with Accounting Standards Codification (“ASC”) Topic 326 (“ASC 326”), that is deducted from the amortized cost basis of held-to-maturity securities to present management's best estimate of the net amount expected to be collected. Held-to-maturity securities are charged-off against the allowance when deemed uncollectible by management. Adjustments to the allowance are reported in our income statement as a component of credit loss expense. Management measures expected credit losses on held-to-maturity securities on a collective basis by major security type with each type sharing similar risk characteristics and considers historical credit loss information that is adjusted for current conditions and reasonable and supportable forecasts. Management has made the accounting policy election to exclude accrued interest receivable on held-to-maturity securities from the estimate of credit losses. Further information regarding our policies and methodology used to estimate the allowance for credit losses on held-to-maturity securities is presented in Note 2 - Securities. Allowance For Credit Losses - Available-for-Sale Securities. For available-for-sale securities in an unrealized loss position, we first assess whether (i) we intend to sell or (ii) it is more likely than not that we will be required to sell the security before recovery of its amortized cost basis. If either case is affirmative, any previously recognized allowances are charged-off and the security's amortized cost is written down to fair value through income. If neither case is affirmative, the security is evaluated to determine whether the decline in fair value has resulted from credit losses or other factors. In making this assessment, management considers the extent to which fair value is less than amortized cost, any changes to the rating of the security by a rating agency and any adverse conditions specifically related to the security, among other factors. If this assessment indicates that a credit loss exists, the present value of cash flows expected to be collected from the security are compared to the amortized cost basis of the security. If the present value of cash flows expected to be collected is less than the amortized cost basis, a credit loss exists and an allowance for credit losses is recorded for the credit loss, limited by the amount that the fair value is less than the amortized cost basis. Any impairment that has not been recorded through an allowance for credit losses is recognized in other comprehensive income. Adjustments to the allowance are reported in our income statement as a component of credit loss expense. Management has made the accounting policy election to exclude accrued interest receivable on available-for-sale securities from the estimate of credit losses. Available-for-sale securities are charged-off against the allowance or, in the absence of any allowance, written down through income when deemed uncollectible by management or when either of the aforementioned criteria regarding intent or requirement to sell is met. 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 management's best estimate of the net amount expected to be collected. Loans are charged-off against the allowance when deemed uncollectible by management. Expected recoveries do not exceed the aggregate of amounts previously charged-off and expected to be charged-off. Adjustments to the allowance are reported in our income statement as a component of credit loss expense. Management has made the accounting policy election to exclude accrued interest receivable on loans from the estimate of credit losses. Further information regarding our policies and methodology used to estimate the allowance for credit losses on loans is presented in Note 3 - Loans. 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. The allowance is reported as a component of accrued interest payable and other liabilities in our consolidated balance sheets. Adjustments to the allowance are reported in our income statement as a component of credit loss expense. Further information regarding our policies and methodology used to estimate the allowance for credit losses on off-balance-sheet credit exposures is presented in Note 7 - Off-Balance-Sheet Arrangements, Commitments, Guarantees and Contingencies. Premises and Equipment. Land is carried at cost. Building and improvements, and furniture and equipment are carried at cost, less accumulated depreciation, computed principally by the straight-line method based on the estimated useful lives of the related property. Leasehold improvements are generally depreciated over the lesser of the term of the respective leases or the estimated useful lives of the improvements. We lease certain office facilities and office equipment under operating leases. We also own certain office facilities which we lease to outside parties under operating lessor leases; however, such leases are not significant. For operating leases other than those considered to be short-term, we recognize lease right-of-use assets and related lease liabilities. Such amounts are reported as components of premises and equipment and accrued interest payable and other liabilities, respectively, on our accompanying consolidated balance sheet. We do not recognize short-term operating leases on our balance sheet. A short-term operating lease has an original term of 12 months or less and does not have a purchase option that is likely to be exercised. In recognizing lease right-of-use assets and related lease liabilities, we account for lease and non-lease components (such as taxes, insurance, and common area maintenance costs) separately as such amounts are generally readily determinable under our lease contracts. Lease payments over the expected term are discounted using our incremental borrowing rate referenced to the Federal Home Loan Bank Secure Connect advance rates for borrowings of similar term. We also consider renewal and termination options in the determination of the term of the lease. If it is reasonably certain that a renewal or termination option will be exercised, the effects of such options are included in the determination of the expected lease term. Generally, we cannot be reasonably certain about whether or not we will renew a lease until such time the lease is within the last two years of the existing lease term. However, renewal options related to our regional headquarters facilities or operations centers are evaluated on a case-by-case basis, typically in advance of such time frame. When we are reasonably certain that a renewal option will be exercised, we measure/remeasure the right-of-use asset and related lease liability using the lease payments specified for the renewal period or, if such amounts are unspecified, we generally assume an increase (evaluated on a case-by-case basis in light of prevailing market conditions) in the lease payment over the final period of the existing lease term. Foreclosed Assets . Assets acquired through or instead of loan foreclosure are held for sale and are initially recorded at fair value less estimated selling costs when acquired, establishing a new cost basis. Write-downs occurring at acquisition are charged against the allowance for credit losses on loans. Foreclosed assets are included in other assets in the accompanying consolidated balance sheets and totaled $725 thousand and $1.0 million at December 31, 2023 and 2022. Regulatory guidelines require us to reevaluate the fair value of foreclosed assets on at least an annual basis. Our policy is to comply with the regulatory guidelines. If the fair value of the asset declines, a write-down is recorded through other non-interest expense along with other expenses related to maintaining the properties. The valuation of foreclosed assets is subjective in nature and may be adjusted in the future because of changes in economic conditions. There were no write-downs of foreclosed assets in 2023 or 2022, while write-downs of foreclosed assets totaled $14 thousand in 2021. There were no significant concentrations of any properties, to which the aforementioned write-downs relate, in any single geographic region. Revenue Recognition . In general, for revenue not associated with financial instruments, guarantees and lease contracts, we apply the following steps when recognizing revenue from contracts with customers: (i) identify the contract, (ii) identify the performance obligations, (iii) determine the transaction price, (iv) allocate the transaction price to the performance obligations and (v) recognize revenue when a performance obligation is satisfied. Our contracts with customers are generally short term in nature, typically due within one year or less or cancellable by us or our customer upon a short notice period. Performance obligations for our customer contracts are generally satisfied at a single point in time, typically when the transaction is complete, or over time. For performance obligations satisfied over time, we primarily use the output method, directly measuring the value of the products/services transferred to the customer, to determine when performance obligations have been satisfied. We typically receive payment from customers and recognize revenue concurrent with the satisfaction of our performance obligations. In most cases, this occurs within a single financial reporting period. For payments received in advance of the satisfaction of performance obligations, revenue recognition is deferred until such time as the performance obligations have been satisfied. In cases where we have not received payment despite satisfaction of our performance obligations, we accrue an estimate of the amount due in the period our performance obligations have been satisfied. For contracts with variable components, only amounts for which collection is probable are accrued. We generally act in a principal capacity, on our own behalf, in most of our contracts with customers. In such transactions, we recognize revenue and the related costs to provide our services on a gross basis in our financial statements. In some cases, we act in an agent capacity, deriving revenue through assisting other entities in transactions with our customers. In such transactions, we recognize revenue and the related costs to provide our services on a net basis in our financial statements. These transactions recognized on a net basis primarily relate to insurance and brokerage commissions and fees derived from our customers' use of various interchange and ATM/debit card networks. Share-Based Payments . Compensation expense for stock options, non-vested stock awards/stock units and deferred stock units is based on the fair value of the award on the measurement date, which, for us, is the date of the grant and is recognized ratably over the service period of the award. Compensation expense for performance stock units is based on the fair value of the award on the measurement date, which, for us, is the date of the grant and is recognized over the service period of the award based upon the probable number of units expected to vest. The fair value of stock options is estimated using a binomial lattice-based valuation model. The fair value of non-vested stock awards/stock units and deferred stock units is generally the market price of our stock on the date of grant. The fair value of performance stock units is generally the market price of our stock on the date of grant discounted by the present value of the dividends expected to be paid on our common stock during the service period of the award because dividend equivalent payments on performance stock units are deferred until such time that the units vest and shares are issued. The impact of forfeitures of share-based payment awards on compensation expense is recognized as forfeitures occur. Advertising Costs. Advertising costs are expensed as incurred. Income Taxes . Income tax expense is the total of the current year income tax due or refundable and the change in deferred tax assets and liabilities (excluding deferred tax assets and liabilities related to business combinations or components of other comprehensive income). Deferred tax assets and liabilities are the expected future tax amounts for the temporary differences between carrying amounts and tax bases of assets and liabilities, computed using enacted tax rates. A valuation allowance, if needed, reduces deferred tax assets to the expected amount most likely to be realized. Realization of deferred tax assets is dependent upon the generation of a sufficient level of future taxable income. Although realization is not assured, management believes it is more likely than not that all of the deferred tax assets will be realized. Interest and/or penalties related to income taxes are reported as a component of income tax expense. The income tax effects related to settlements of share-based payment awards are reported in earnings as an increase (or decrease) to income tax expense. See Note 12 - Income Taxes. We file a consolidated income tax return with our subsidiaries. Federal income tax expense or benefit has been allocated to subsidiaries on a separate return basis. Basic and Diluted Earnings Per Common Share. Earnings per common share is computed using the two-class method prescribed under ASC Topic 260, “Earnings Per Share.” ASC 260 provides that unvested share-based payment awards that contain nonforfeitable rights to dividends or dividend equivalents (whether paid or unpaid) are participating securities and shall be included in the computation of earnings per share pursuant to the two-class method. We have determined that our outstanding non-vested stock awards/stock units and deferred stock units are participating securities. Under the two-class method, basic earnings per common share is computed by dividing net earnings allocated to common stock by the weighted-average number of common shares outstanding during the applicable period, excluding outstanding participating securities. Diluted earnings per common share is computed using the weighted-average number of shares determined for the basic earnings per common share computation plus the dilutive effect of stock compensation using the treasury stock method. A reconciliation of the weighted-average shares used in calculating basic earnings per common share and the weighted average common shares used in calculating diluted earnings per common share for the reported periods is provided in Note 9 - Earnings Per Common Share. Comprehensive Income. Comprehensive income includes all changes in shareholders’ equity during a period, except those resulting from transactions with shareholders. Besides net income, other components of our comprehensive income include the after tax effect of changes in the net unrealized gain/loss on securities available for sale, changes in the net unrealized gain on securities transferred to held to maturity and changes in the net actuarial gain/loss on defined benefit post-retirement benefit plans. See Note 13 - Other Comprehensive Income (Loss). Derivative Financial Instruments . Our hedging policies permit the use of various derivative financial instruments to manage interest rate risk or to hedge specified assets and liabilities. All derivatives are recorded at fair value on our balance sheet. Derivatives executed with the same counterparty are generally subject to master netting arrangements, however, fair value amounts recognized for derivatives and fair value amounts recognized for the right/obligation to reclaim/return cash collateral are not offset for financial reporting purposes. We may be required to recognize certain contracts and commitments as derivatives when the characteristics of those contracts and commitments meet the definition of a derivative. To qualify for hedge accounting, derivatives must be highly effective at reducing the risk associated with the exposure being hedged and must be designated as a hedge at the inception of the derivative contract. We consider a hedge to be highly effective if the change in fair value of the derivative hedging instrument is within 80% to 125% of the opposite change in the fair value of the hedged item attributable to the hedged risk. If derivative instruments are designated as hedges of fair values, and such hedges are highly effective, both the change in the fair value of the hedge and the hedged item are included in current earnings. Fair value adjustments related to cash flow hedges are recorded in other comprehensive income and are reclassified to earnings when the hedged transaction is reflected in earnings. Ineffective portions of hedges are reflected in earnings as they occur. Actual cash receipts and/or payments and related accruals on derivatives related to hedges are recorded as adjustments to the interest income or interest expense associated with the hedged item. During the life of the hedge, we formally assess whether derivatives designated as hedging instruments continue to be highly effective in offsetting changes in the fair value or cash flows of hedged items. If it is determined that a hedge has ceased to be highly effective, we will discontinue hedge accounting prospectively. At such time, previous adjustments to the carrying value of the hedged item are reversed into current earnings and the derivative instrument is reclassified to a trading position recorded at fair value. Fair Value Measurements . In general, fair values of financial instruments are based upon quoted market prices, where available. If such quoted market prices are not available, fair value is based upon internally developed models that primarily use, as inputs, observable market-based parameters. Valuation adjustments may be made to ensure that financial instruments are recorded at fair value. These adjustments may include amounts to reflect counterparty credit quality and our creditworthiness, among other things, as well as unobservable parameters. Any such valuation adjustments are applied consistently over time. See Note 16 - Fair Value Measurements. Transfers of Financial Assets . Transfers of financial assets are accounted for as sales when control over the assets has been surrendered. Control over transferred assets is deemed to be surrendered when (i) the assets have been isolated from us, (ii) the transferee obtains the right (free of conditions that constrain it from taking advantage of that right) to pledge or exchange the transferred assets, and (iii) we do not maintain effective control over the transferred assets through an agreement to repurchase them before their maturity. Loss Contingencies . Loss contingencies, including claims and legal actions arising in the ordinary course of business are recorded as liabilities when the likelihood of loss is probable and an amount or range of loss can be reasonably estimated. Trust Assets. Assets of our trust department, other than cash on deposit at Frost Bank, are not included in the accompanying financial statements because they are not our assets. Accounting Changes, Reclassifications and Restatements.

Securities

Securities	12 Months Ended
	Dec. 31, 2023
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 December 31, 2023 and 2022 is presented below. Amortized Gross Gross Estimated Allowance Net 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 December 31, 2022 Residential mortgage-backed securities $ 526,122 $ — $ 65,322 $ 460,800 $ — $ 526,122 States and political subdivisions 2,111,619 13,048 119,033 2,005,634 (158) 2,111,461 Other 1,500 — 69 1,431 — 1,500 Total $ 2,639,241 $ 13,048 $ 184,424 $ 2,467,865 $ (158) $ 2,639,083 All mortgage-backed securities included in the above table were issued by U.S. government agencies and corporations. The carrying value of held-to-maturity securities pledged to secure public funds, trust deposits, repurchase agreements and for other purposes, as required or permitted by law was $1.0 billion and $256.3 million at December 31, 2023 and 2022, respectively. Accrued interest receivable on held-to-maturity securities totaled $40.9 million and $30.2 million at December 31, 2023 and 2022, 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 securities transferred in years prior to 2020 included in accumulated other comprehensive income in the accompanying balance sheet totaled $1.2 million ($909 thousand, net of tax) at December 31, 2023 and $1.8 million ($1.4 million, net of tax) at December 31, 2022. 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 allowance for credit losses on held-to-maturity securities is a contra-asset valuation account that is deducted from the amortized cost basis of held-to-maturity securities to present the net amount expected to be collected. Management measures expected credit losses on held-to-maturity securities on a collective basis by major security type with each type sharing similar risk characteristics, and considers historical credit loss information that is adjusted for current conditions and reasonable and supportable forecasts. With regard to U.S. Treasury and residential mortgage-backed securities issued by the U.S. government, or agencies thereof, it is expected that the securities will not be settled at prices less than the amortized cost bases of the securities as such securities are backed by the full faith and credit of and/or guaranteed by the U.S. government. Accordingly, no allowance for credit losses has been recorded for these securities. With regard to securities issued by States and political subdivisions and other held-to-maturity securities, management considers (i) issuer bond ratings, (ii) historical loss rates for given bond ratings, (iii) whether issuers continue to make timely principal and interest payments under the contractual terms of the securities, (iv) internal forecasts and (v) whether or not such securities are guaranteed by the Texas Permanent School Fund (“PSF”) or pre-refunded by the issuers. 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 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 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 Historical loss rates associated with securities having similar grades as those in our portfolio have generally not been significant. Furthermore, as of December 31, 2023, there were no past due principal or interest payments associated with these securities. The PSF is a sovereign wealth fund which serves to provide revenues for funding of public primary and secondary education in the State of Texas. Based upon (i) the PSF's AAA insurer financial strength rating, (ii) the PSF's substantial capitalization and excess guarantee capacity and (iii) a zero historical loss rate, no allowance for credit losses has been recorded for securities guaranteed by the PSF as there is no current expectation of credit losses related to these securities. Pre-refunded securities have been defeased by the issuer and are fully secured by cash and/or U.S. Treasury securities held in escrow for payment to holders when the underlying call dates of the securities are reached. Accordingly, no allowance for credit losses has been recorded for securities that have been defeased as there is no current expectation of credit losses related to these securities. The following table details activity in the allowance for credit losses on held-to-maturity securities. 2023 2022 2021 Beginning balance $ 158 $ 158 $ 160 Credit loss expense (benefit) 152 — (2) Ending balance $ 310 $ 158 $ 158 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 December 31, 2023 and 2022 is presented below. Amortized Gross Gross Allowance Estimated 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 December 31, 2022 U.S. Treasury $ 5,450,546 $ — $ 398,959 $ — $ 5,051,587 Residential mortgage-backed securities 7,316,824 8,050 948,638 — 6,376,236 States and political subdivisions 7,098,635 9,108 334,388 — 6,773,355 Other 42,427 — — — 42,427 Total $ 19,908,432 $ 17,158 $ 1,681,985 $ — $ 18,243,605 All mortgage-backed securities included in the above table were issued by U.S. government agencies and corporations. At December 31, 2023 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 73.5% are either guaranteed by the 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 $6.1 billion and $8.0 billion at December 31, 2023 and 2022, respectively. Accrued interest receivable on available-for-sale securities totaled $114.9 million and $140.6 million at December 31, 2023 and 2022, respectively, and is included in accrued interest receivable and other assets in the accompanying consolidated balance sheets. The table below summarizes, as of December 31, 2023, 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 $ — $ — $ 4,927,590 $ 285,305 $ 4,927,590 $ 285,305 Residential mortgage-backed securities 879,380 6,883 5,062,456 869,455 5,941,836 876,338 States and political subdivisions 1,810,373 10,035 2,652,951 230,117 4,463,324 240,152 Total $ 2,689,753 $ 16,918 $ 12,642,997 $ 1,384,877 $ 15,332,750 $ 1,401,795 As of December 31, 2023, 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 December 31, 2023. 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 $ — $ — $ 512,995 $ 737,436 $ 1,250,431 States and political subdivisions 8,170 12,008 52,106 2,295,523 2,367,807 Other — 1,500 — — 1,500 Total $ 8,170 $ 13,508 $ 565,101 $ 3,032,959 $ 3,619,738 Estimated Fair Value Residential mortgage-backed securities $ — $ — $ 461,253 $ 735,079 $ 1,196,332 States and political subdivisions 8,175 11,999 50,728 2,263,355 2,334,257 Other — 1,455 — — 1,455 Total $ 8,175 $ 13,454 $ 511,981 $ 2,998,434 $ 3,532,044 Available For Sale Amortized Cost U. S. Treasury $ 1,534,307 $ 3,288,365 $ 197,809 $ 192,413 $ 5,212,894 Residential mortgage-backed securities 1,740 1,827 13,985 7,446,402 7,463,954 States and political subdivisions 370,259 183,228 880,659 3,811,575 5,245,721 Other — — — — 42,769 Total $ 1,906,306 $ 3,473,420 $ 1,092,453 $ 11,450,390 $ 17,965,338 Estimated Fair Value U. S. Treasury $ 1,514,227 $ 3,101,776 $ 167,219 $ 144,367 $ 4,927,589 Residential mortgage-backed securities 1,718 1,826 13,963 6,579,175 6,596,682 States and political subdivisions 370,111 182,786 859,675 3,598,759 5,011,331 Other — — — — 42,769 Total $ 1,886,056 $ 3,286,388 $ 1,040,857 $ 10,322,301 $ 16,578,371 Sales of Securities. Sales of securities available for sale were as follows: 2023 2022 2021 Proceeds from sales $ 1,904,067 $ — $ 1,999,891 Gross realized gains 5,758 — 69 Gross realized losses (5,692) — — Tax benefit (expense) related to securities gains/losses (14) — (14) Premiums and Discounts. Premium amortization and discount accretion included in interest income on securities was as follows: 2023 2022 2021 Premium amortization $ (85,506) $ (110,997) $ (121,994) Discount accretion 21,613 13,597 2,752 Net (premium amortization) discount accretion $ (63,893) $ (97,400) $ (119,242) Trading Account Securities. Year-end trading account securities, at estimated fair value, were as follows: 2023 2022 U.S. Treasury $ 30,265 $ 25,879 States and political subdivisions 1,452 2,166 Total $ 31,717 $ 28,045 Net gains and losses on trading account securities were as follows: 2023 2022 2021 Net gain on sales transactions $ 3,843 $ 3,129 $ 1,014 Net mark-to-market gains (losses) (33) (230) (75) Net gain on trading account securities $ 3,810 $ 2,899 $ 939

Loans

Loans	12 Months Ended
	Dec. 31, 2023
Receivables [Abstract]
Loans	Loans Year-end loans, including leases net of unearned discounts, consisted of the following: 2023 2022 Commercial and industrial $ 5,959,133 $ 5,674,798 Energy: Production 681,568 696,570 Service 192,654 133,542 Other 61,043 95,617 Total energy 935,265 925,729 Paycheck Protection Program (“PPP”) 9,521 34,852 Commercial real estate: Commercial mortgages 6,746,709 6,168,910 Construction 1,680,724 1,477,247 Land 555,211 537,168 Total commercial real estate 8,982,644 8,183,325 Consumer real estate: Home equity lines of credit 792,876 691,841 Home equity loans 694,966 449,507 Home improvement loans 765,887 577,377 Other 206,997 124,814 Total consumer real estate 2,460,726 1,843,539 Total real estate 11,443,370 10,026,864 Consumer and other 476,962 492,726 Total loans $ 18,824,251 $ 17,154,969 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 December 31, 2023, the largest industry concentrations were related to the automobile dealerships industry, which totaled 5.9% of total loans and the energy industry, which totaled 5.0% of total loans. Unfunded commitments to extend credit and standby letters of credit issued to customers in the automobile dealership industry totaled $522.8 million and $19.3 million, respectively, as of December 31, 2023, while unfunded commitments to extend credit and standby letters of credit issued to customers in the energy industry totaled $1.1 billion and $86.9 million, respectively, as of December 31, 2023. 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 December 31, 2023 or 2022. Overdrafts . Deposit account overdrafts reported as loans totaled $13.4 million and $10.3 million at December 31, 2023 and 2022. 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”). Activity in related party loans during 2023 is presented in the following table. Other changes were primarily related to changes in related-party status. Balance outstanding at December 31, 2022 $ 391,255 Principal additions 322,183 Principal payments (299,338) Other changes 2,007 Balance outstanding at December 31, 2023 $ 416,107 Accrued Interest Receivable. Accrued interest receivable on loans totaled $90.8 million and $68.7 million at December 31, 2023 and 2022, respectively and is included in accrued interest receivable and other assets in the accompany 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. In determining whether or not a borrower may be unable to meet payment obligations for each class of loans, we consider the borrower’s debt service capacity through the analysis of current financial information, if available, and/or current information with regards to our collateral position. Regulatory provisions would typically require the placement of a loan on non-accrual status if (i) principal or interest has been in default for a period of 90 days or more unless the loan is both well secured and in the process of collection or (ii) full payment of principal and interest is not expected. Loans may be placed on non-accrual status regardless of whether or not such loans are considered past due. When interest accrual is discontinued, all unpaid accrued interest is reversed. Interest income on non-accrual loans is recognized only to the extent that cash payments are received in excess of principal due. A loan may be returned to accrual status when all the principal and interest amounts contractually due are brought current and future principal and interest amounts contractually due are reasonably assured, which is typically evidenced by a sustained period (at least six months) of repayment performance by the borrower. Year-end non-accrual loans, segregated by class of loans, were as follows: December 31, 2023 December 31, 2022 Total Non-Accrual Non-Accrual with No Credit Loss Allowance Total Non-Accrual Non-Accrual with No Credit Loss Allowance Commercial and industrial $ 19,545 $ 5,391 $ 18,130 $ 8,514 Energy 11,500 7,398 15,224 7,139 Commercial real estate: Buildings, land and other 22,420 4,983 3,552 1,991 Construction — — — — Consumer real estate 7,442 5,160 927 927 Consumer and other — — — — Total $ 60,907 $ 22,932 $ 37,833 $ 18,571 The following tables present non-accrual loans as of December 31, 2023 and December 31, 2022 by class and year of origination. December 31, 2023 2023 2022 2021 2020 2019 Prior Revolving Loans Revolving Loans Converted to Term Total Commercial and industrial $ — $ 359 $ 1,635 $ 985 $ 1,257 $ 1,006 $ 9 $ 14,294 $ 19,545 Energy 5,875 — — 56 1,321 — 4,102 146 11,500 Commercial real estate: Buildings, land and other 20,099 — 150 — 1,451 720 — — 22,420 Construction — — — — — — — — — Consumer real estate — — — 38 2,281 483 1,600 3,040 7,442 Consumer and other — — — — — — — — — Total $ 25,974 $ 359 $ 1,785 $ 1,079 $ 6,310 $ 2,209 $ 5,711 $ 17,480 $ 60,907 December 31, 2022 2022 2021 2020 2019 2018 Prior Revolving Loans Revolving Loans Converted to Term Total Commercial and industrial $ — $ 1,252 $ 1,089 $ 3,242 $ 1,197 $ 191 $ 2,973 $ 8,186 $ 18,130 Energy 4,657 — 72 1,386 10 — 7,631 1,468 15,224 Commercial real estate: Buildings, land and other 1,644 — — 217 266 1,425 — — 3,552 Construction — — — — — — — — — Consumer real estate — 258 — — — 84 — 585 927 Consumer and other — — — — — — — — — Total $ 6,301 $ 1,510 $ 1,161 $ 4,845 $ 1,473 $ 1,700 $ 10,604 $ 10,239 $ 37,833 In the tables above, loans reported as 2023 originations as of December 31, 2023 and loans reported as 2022 originations as of December 31, 2022 were, for the most part, first originated in various years prior to 2023 and 2022, respectively, but were renewed in the respective 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 $4.0 million in 2023, $1.7 million in 2022 and $1.8 million in 2021. An age analysis of past due loans (including both accruing and non-accruing loans), segregated by class of loans, as of December 31, 2023 is presented in the following table. Despite their past due status, PPP loans are fully guaranteed by the Small Business Administration (“SBA”). Loans Loans Total Past Current Total Loans Accruing Commercial and industrial $ 27,551 $ 21,705 $ 49,256 $ 5,909,877 $ 5,959,133 $ 5,503 Energy 6,387 6,771 13,158 922,107 935,265 1,146 Paycheck Protection Program 61 1,954 2,015 7,506 9,521 1,954 Commercial real estate: Buildings, land and other 20,224 1,610 21,834 7,280,086 7,301,920 92 Construction 4,878 3,498 8,376 1,672,348 1,680,724 3,498 Consumer real estate 12,504 7,716 20,220 2,440,506 2,460,726 2,589 Consumer and other 6,495 251 6,746 470,216 476,962 251 Total $ 78,100 $ 43,505 $ 121,605 $ 18,702,646 $ 18,824,251 $ 15,033 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, a term extension, or a combination thereof, among other things. The period-end balance of loan modifications, segregated by type of modification, to borrowers experiencing financial difficulty during 2023 and 2022 are set forth in the table below, regardless of whether such modifications resulted in a new loan. There were no commitments to lend additional funds to these borrowers at December 31, 2023. Payment Percent of Combination: Payment Delay and Term Extension Percent of Combination: Interest Rate Reduction and Term Extension Percent of December 31, 2023 Commercial and industrial $ — — % $ 13,813 0.2 % $ — — % Commercial real estate: Buildings, land, and other — — 19,438 0.3 2,092 — $ — — $ 33,251 0.2 $ 2,092 — December 31, 2022 Commercial real estate: Buildings, land, and other $ 1,051 — $ — — $ — — $ 1,051 — $ — — $ — — During 2023, we modified the interest rate on one loan from a variable rate of prime plus a spread of 1.75% (10.25% as of the modification date) to a fixed rate of 6.74% in addition to extending the term of the loan. The financial effects of the other loan modifications made to borrowers experiencing financial difficulty during 2023 were not significant. The loan modifications reported in the table above did not significantly impact our determination of the allowance for credit losses on loans during 2023. Information as of or for the years ended December 31, 2023, 2022, or 2021 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. Payment Combination: Payment Delay and Term Extension Combination: Interest Rate Reduction and Term Extension 2023 Past due in excess of 90 days or on non-accrual status at period-end: Commercial and industrial $ — $ 13,813 $ — Commercial real estate: Buildings, land, and other — 19,438 — $ — $ 33,251 $ — 2022 Past due in excess of 90 days or on non-accrual status at period-end: Commercial real estate: Buildings, land, and other $ 1,051 $ — $ — $ 1,051 $ — $ — Charge-offs during the period: Commercial real estate: Buildings, land, and other $ 371 $ 352 $ — $ 371 $ 352 $ — Proceeds from sales: Commercial real estate: Buildings, land, and other $ — $ 1,070 $ — $ — $ 1,070 $ — 2021 Past due in excess of 90 days or on non-accrual status at period-end: Commercial and industrial $ 1,162 $ — $ — Energy 721 — — Commercial real estate: Buildings, land, and other 306 1,556 — $ 2,189 $ 1,556 $ — Charge-offs during the period: Energy $ 4,278 $ — $ — $ 4,278 $ — $ — 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 (vi) 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 as follows: • Grades 1, 2 and 3 - These grades include loans to very high credit quality borrowers of investment or near investment grade. These borrowers are generally publicly traded (grades 1 and 2), have significant capital strength, moderate leverage, stable earnings and growth, and readily available financing alternatives. Smaller entities, regardless of strength, would generally not fit in these grades. • Grades 4 and 5 - These grades include loans to borrowers of solid credit quality with moderate risk. Borrowers in these grades are differentiated from higher grades on the basis of size (capital and/or revenue), leverage, asset quality and the stability of the industry or market area. • Grades 6, 7 and 8 - These grades include “pass grade” loans to borrowers of acceptable credit quality and risk. Such borrowers are differentiated from Grades 4 and 5 in terms of size, secondary sources of repayment or they are of lesser stature in other key credit metrics in that they may be over-leveraged, under capitalized, inconsistent in performance or in an industry or an economic area that is known to have a higher level of risk, volatility, or susceptibility to weaknesses in the economy. • Grade 9 - This grade includes loans on management’s “watch list” and is intended to be utilized on a temporary basis for pass grade borrowers where a significant risk-modifying action is anticipated in the near term. • Grade 10 - This grade is for “Other Assets Especially Mentioned” in accordance with regulatory guidelines. This grade is intended to be temporary and includes loans to borrowers whose credit quality has clearly deteriorated and are at risk of further decline unless active measures are taken to correct the situation. • Grade 11 - This grade includes “Substandard” loans, in accordance with regulatory guidelines, for which the accrual of interest has not been stopped. By definition under regulatory guidelines, a “Substandard” loan has defined weaknesses which make payment default or principal exposure likely, but not yet certain. Such loans are apt to be dependent upon collateral liquidation, a secondary source of repayment or an event outside of the normal course of business. • Grade 12 - This grade includes “Substandard” loans, in accordance with regulatory guidelines, for which the accrual of interest has been stopped. This grade includes loans where interest is more than 120 days past due and not fully secured and loans where a specific valuation allowance may be necessary, but generally does not exceed 30% of the principal balance. • Grade 13 - This grade includes “Doubtful” loans in accordance with regulatory guidelines. Such loans are placed on non-accrual status and may be dependent upon collateral having a value that is difficult to determine or upon some near-term event which lacks certainty. Additionally, these loans generally have a specific valuation allowance in excess of 30% of the principal balance. • Grade 14 - This grade includes “Loss” loans in accordance with regulatory guidelines. Such loans are to be charged-off or charged-down when payment is acknowledged to be uncertain or when the timing or value of payments cannot be determined. “Loss” is not intended to imply that the loan or some portion of it will never be paid, nor does it in any way imply that there has been a forgiveness of debt. In monitoring credit quality trends in the context of assessing the appropriate level of the allowance for credit losses on loans, 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 tables present weighted-average risk grades for all commercial loans, by class and year of origination/renewal as of December 31, 2023 and 2022. PPP loans are excluded as such loans are fully guaranteed by the SBA. December 31, 2023 2023 2022 2021 2020 2019 Prior Revolving Loans Revolving Loans Converted to Term Total Commercial and industrial Risk grades 1-8 $ 1,489,026 $ 706,210 $ 450,806 $ 349,744 $ 172,656 $ 206,643 $ 2,083,490 $ 41,254 $ 5,499,829 Risk grade 9 57,625 42,618 12,258 4,952 1,641 10,383 70,142 5,625 205,244 Risk grade 10 63,205 2,222 1,307 911 4,005 581 35,977 1,046 109,254 Risk grade 11 9,450 16,837 25,932 7,854 2,530 1,153 58,134 3,371 125,261 Risk grade 12 — 359 1,635 950 1,257 1,006 1 11,894 17,102 Risk grade 13 — — — 35 — — 8 2,400 2,443 $ 1,619,306 $ 768,246 $ 491,938 $ 364,446 $ 182,089 $ 219,766 $ 2,247,752 $ 65,590 $ 5,959,133 W/A risk grade 6.53 7.05 7.26 5.87 6.01 6.04 6.50 8.48 6.60 Energy Risk grades 1-8 $ 270,710 $ 54,185 $ 73,532 $ 3,673 $ 1,819 $ 4,047 $ 451,897 $ 9,886 $ 869,749 Risk grade 9 1,137 7,315 1,041 — 456 — 17,680 14 27,643 Risk grade 10 — — 33 — 291 494 — — 818 Risk grade 11 — — 25 106 2,989 — 21,650 785 25,555 Risk grade 12 5,875 — — 56 1,321 — 1,402 146 8,800 Risk grade 13 — — — — — — 2,700 — 2,700 $ 277,722 $ 61,500 $ 74,631 $ 3,835 $ 6,876 $ 4,541 $ 495,329 $ 10,831 $ 935,265 W/A risk grade 6.19 7.07 6.00 6.99 10.02 7.07 5.75 7.33 6.05 Commercial real estate: Buildings, land, other Risk grades 1-8 $ 1,601,175 $ 1,667,750 $ 1,186,559 $ 747,289 $ 503,303 $ 874,942 $ 214,874 $ 99,466 $ 6,895,358 Risk grade 9 12,173 68,007 28,870 13,250 16,272 23,214 11,143 541 173,470 Risk grade 10 7,671 29,278 17,364 34,672 747 3,153 3,716 — 96,601 Risk grade 11 4,105 20,589 20,119 16,363 793 51,739 — 363 114,071 Risk grade 12 17,449 — 150 — 1,451 720 — — 19,770 Risk grade 13 2,650 — — — — — — — 2,650 $ 1,645,223 $ 1,785,624 $ 1,253,062 $ 811,574 $ 522,566 $ 953,768 $ 229,733 $ 100,370 $ 7,301,920 W/A risk grade 7.23 7.18 7.29 7.22 6.90 7.16 7.49 6.77 7.20 Construction Risk grades 1-8 $ 538,072 $ 537,705 $ 264,770 $ 28,063 $ 296 $ 1,613 $ 155,567 $ — $ 1,526,086 Risk grade 9 3,414 35,565 79,871 — — — 8,252 — 127,102 Risk grade 10 13,322 — — — — — 3,713 — 17,035 Risk grade 11 5,912 3,104 — — — — 1,485 — 10,501 Risk grade 12 — — — — — — — — — Risk grade 13 — — — — — — — — — $ 560,720 $ 576,374 $ 344,641 $ 28,063 $ 296 $ 1,613 $ 169,017 $ — $ 1,680,724 W/A risk grade 7.44 7.44 7.93 2.55 7.22 6.78 7.34 — 7.45 Total commercial real estate $ 2,205,943 $ 2,361,998 $ 1,597,703 $ 839,637 $ 522,862 $ 955,381 $ 398,750 $ 100,370 $ 8,982,644 W/A risk grade 7.28 7.24 7.43 7.07 6.90 7.15 7.43 6.77 7.24 December 31, 2022 2022 2021 2020 2019 2018 Prior Revolving Loans Revolving Loans Converted to Term Total Commercial and industrial Risk grades 1-8 $ 1,667,274 $ 618,756 $ 485,908 $ 226,835 $ 123,768 $ 192,791 $ 2,068,891 $ 51,694 $ 5,435,917 Risk grade 9 31,275 34,950 3,651 5,400 11,006 1,014 54,856 4,040 146,192 Risk grade 10 2,294 724 845 4,713 1,341 114 23,880 3,685 37,596 Risk grade 11 2,342 1,357 6,720 1,807 1,229 1,644 19,582 2,282 36,963 Risk grade 12 — 1,052 866 2,972 1,177 191 673 5,590 12,521 Risk grade 13 — 200 223 270 20 — 2,300 2,596 5,609 $ 1,703,185 $ 657,039 $ 498,213 $ 241,997 $ 138,541 $ 195,754 $ 2,170,182 $ 69,887 $ 5,674,798 W/A risk grade 6.37 7.05 6.01 6.59 6.87 5.55 6.26 7.68 6.39 Energy Risk grades 1-8 $ 338,050 $ 99,089 $ 4,917 $ 3,138 $ 2,020 $ 2,850 $ 393,957 $ 43,161 $ 887,182 Risk grade 9 1,561 1,611 166 562 748 — 6,434 30 11,112 Risk grade 10 — — — 428 214 — — — 642 Risk grade 11 7,956 162 157 3,145 86 63 — — 11,569 Risk grade 12 3,995 — 72 1,386 10 — 4,571 806 10,840 Risk grade 13 662 — — — — — 3,060 662 4,384 $ 352,224 $ 100,862 $ 5,312 $ 8,659 $ 3,078 $ 2,913 $ 408,022 $ 44,659 $ 925,729 W/A risk grade 6.09 5.65 7.65 9.64 8.02 6.59 5.18 5.69 5.67 Commercial real estate: Buildings, land, other Risk grades 1-8 $ 1,811,069 $ 1,484,811 $ 956,567 $ 708,942 $ 360,154 $ 800,944 $ 111,778 $ 105,763 $ 6,340,028 Risk grade 9 52,288 13,139 36,264 22,086 17,699 45,590 652 2,210 189,928 Risk grade 10 26,688 11,150 3,735 9,008 29,683 5,221 5,535 — 91,020 Risk grade 11 10,199 19,073 12,631 4,778 2,525 28,841 2,993 510 81,550 Risk grade 12 1,049 — — 217 266 1,425 — — 2,957 Risk grade 13 595 — — — — — — — 595 $ 1,901,888 $ 1,528,173 $ 1,009,197 $ 745,031 $ 410,327 $ 882,021 $ 120,958 $ 108,483 $ 6,706,078 W/A risk grade 7.01 7.26 7.14 7.01 7.33 6.94 7.38 6.43 7.09 Construction Risk grades 1-8 $ 640,948 $ 489,391 $ 128,788 $ 2,236 $ 486 $ 1,726 $ 163,293 $ 3,144 $ 1,430,012 Risk grade 9 12,865 2,100 2,100 — — — 17,887 — 34,952 Risk grade 10 859 72 — — — — — — 931 Risk grade 11 11,352 — — — — — — — 11,352 Risk grade 12 — — — — — — — — — Risk grade 13 — — — — — — — — — $ 666,024 $ 491,563 $ 130,888 $ 2,236 $ 486 $ 1,726 $ 181,180 $ 3,144 $ 1,477,247 W/A risk grade 7.29 7.03 6.43 7.04 6.00 6.76 7.23 5.03 7.12 Total commercial real estate $ 2,567,912 $ 2,019,736 $ 1,140,085 $ 747,267 $ 410,813 $ 883,747 $ 302,138 $ 111,627 $ 8,183,325 W/A risk grade 7.08 7.20 7.06 7.01 7.33 6.94 7.29 6.39 7.10 At December 31, 2023 and 2022, the weighted-average risk grades for “pass grade” (risk grades 1-8) loans were 6.32 and 6.24, respectively, for commercial and industrial; 5.73 and 5.44, respectively, for energy; 7.03 and 6.94, respectively, for commercial real estate - buildings, land and other; and 7.27 and 7.04, respectively, for commercial real estate - construction. Furthermore, in the tables above, there are loans reported as 2023 originations as of December 31, 2023 and 2022 originations as of December 31, 2022 that have risk grades of 11 or higher. These loans were, for the most part, first originated in various years prior to 2023 and 2022, respectively, but were renewed in the respective year. Information about the payment status of consumer loans, segregated by portfolio segment and year of origination, as of December 31, 2023 and December 31, 2022 was as follows: December 31, 2023 2023 2022 2021 2020 2019 Prior Revolving Loans Revolving Loans Converted to Term Total Consumer real estate: Past due 30-89 days $ 874 $ 2,066 $ 1,318 $ 959 $ 537 $ 2,641 $ 3,570 $ 539 $ 12,504 Past due 90 or more days — 512 626 38 — 887 2,566 3,087 7,716 Total past due 874 2,578 1,944 997 537 3,528 6,136 3,626 20,220 Current loans 579,505 432,719 281,820 170,225 58,744 134,319 775,465 7,709 2,440,506 Total $ 580,379 $ 435,297 $ 283,764 $ 171,222 $ 59,281 $ 137,847 $ 781,601 $ 11,335 $ 2,460,726 Consumer and other: Past due 30-89 days $ 3,014 $ 488 $ 148 $ 66 $ 28 $ 40 $ 2,553 $ 158 $ 6,495 Past due 90 or more days 153 — 27 — 20 — 51 — 251 Total past due 3,167 488 175 66 48 40 2,604 158 6,746 Current loans 67,272 28,885 6,290 3,581 1,199 1,230 339,789 21,970 470,216 Total $ 70,439 $ 29,373 $ 6,465 $ 3,647 $ 1,247 $ 1,270 $ 342,393 $ 22,128 $ 476,962 December 31, 2022 2022 2021 2020 2019 2018 Prior Revolving Loans Revolving Loans Converted to Term Total Consumer real estate: Past due 30-89 days $ 793 $ 1,125 $ 645 $ 936 $ 503 $ 2,087 $ 565 $ 1,202 $ 7,856 Past due 90 or more days 95 258 28 — 129 919 347 914 2,690 Total past due 888 1,383 673 936 632 3,006 912 2,116 10,546 Current loans 403,587 313,222 194,900 70,723 38,904 122,585 678,418 10,654 1,832,993 Total $ 404,475 $ 314,605 $ 195,573 $ 71,659 $ 39,536 $ 125,591 $ 679,330 $ 12,770 $ 1,843,539 Consumer and other: Past due 30-89 days $ 2,673 $ 511 $ 128 $ 51 $ 4 $ 31 $ 314 $ 1,443 $ 5,155 Past due 90 or more days 77 2 — 13 — — 25 194 311 Total past due 2,750 513 128 64 4 31 339 1,637 5,466 Current loans 59,886 20,887 6,475 2,897 1,271 1,632 372,117 22,095 487,260 Total $ 62,636 $ 21,400 $ 6,603 $ 2,961 $ 1,275 $ 1,663 $ 372,456 $ 23,732 $ 492,726 Revolving loans that converted to term during 2023 and 2022 were as follows: 2023 2022 Commercial and industrial $ 28,713 $ 34,247 Energy 6,409 3,295 Commercial real estate: Buildings, land and other 4,780 12,174 Construction — 3,144 Consumer real estate 2,467 5,381 Consumer and other 7,482 9,200 Total $ 49,851 $ 67,441 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 is a single summary statistic that is designed to signal the likelihood of the Texas economy’s transition from expansion to recession and vice versa. Management believes this index provides a reliable indication of the direction of overall credit quality. The TLI is a composite of the following eight leading indicators: (i) Texas Value of the Dollar, (ii) U.S. Leading Index, (iii) real oil prices (iv) well permits, (v) initial claims for unemployment insurance, (vi) Texas Stock Index, (vii) Help-Wanted Index and (viii) average weekly hours worked in manufacturing. The TLI totaled 126.8 at December 31, 2023 and 130.4 at December 31, 2022. A lower TLI value implies less favorable economic conditions. Allowance For Credit Losses - Loans. The allowance for credit losses on loans is a contra-asset valuation account, calculated in accordance with ASC 326, that is deducted from the amortized cost basis of loans to present the net amount expected to be collected. The amount of the allowance represents management's best estimate of current expected credit losses on loans considering available information, from internal and external sources, relevant to assessing collectibility over the loans' contractual terms, adjusted for expected prepayments when appropriate. The contractual term excludes expected extensions, renewals and modifications unless (i) management has a reasonable expectation that a loan to an individual borrower that is experiencing financial difficulty will be modified or (ii) such extension or renewal options are not unconditionally cancellable by us and, in such cases, the borrower is likely to meet applicable conditions and likely to request extension or renewal. Relevant available information includes historical credit loss experience, current conditions and reasonable and supportable forecasts. While historical credit loss experience provides the basis for the estimation of expected credit losses, adjustments to historical loss information may be made for differences in current portfolio-specific risk characteristics, environmental conditions or other relevant factors. The allowance for credit losses is measured on a collective basis for portfolios of loans when similar risk characteristics exist. Loans that do not share risk characteristics are evaluated for expected credit losses on an individual basis and excluded from the collective evaluation. Expected credit losses for collateral dependent loans, including loans where the borrower is experiencing financial difficulty but foreclosure is not probable, are based on the fair value of the collateral at the reporting date, adjusted for selling costs as 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. In calculating the allowance for credit losses, most loans are segmented into pools based upon similar characteristics and risk profiles. Common characteristics and risk profiles include the type/purpose of loan, underlying collateral, geographical similarity and historical/expected credit loss patterns. In developing these loan pools for the purposes of modeling expected credit losses, we also analyzed the degree of correlation in how loans within each portfolio respond when subjected to varying economic conditions and scenarios as well as other portfolio stress factors. For modeling purposes, our loan pools include (i) commercial and industrial non-revolving, (ii) commercial and industrial revolving, (iii) energy, (iv) commercial real estate - owner occupied, (v) commercial real estate - non-owner occupied, (vi) commercial real estate - construction/land development, (vii) consumer real estate and (viii) consumer and other. Prior to 2023, energy loans were included within the commercial and industrial loan pools. See discussion of the 2023 model updates below. We periodically reassess each pool to ensure the loans within the pool continue to share similar characteristics and risk profiles and to determine whether further segmentation is necessary. For each loan pool, we measure expected credit losses over the life of each loan utilizing a combination of models which measure (i) probability of default (“PD”), which is the likelihood that loan will stop performing/default, (ii) probability of attrition (“PA”), which is the likelihood that a loan will pay-off prior to maturity, (iii) loss given default (“LGD”), which is the expected loss rate for loans in default and (iv) exposure at default (“EAD”), which is the estimated outstanding principal balance of the loans upon default, including the expected funding of unfunded commitments outstanding as of the measurement date. For certain commercial loan portfolios, the PD is calculated using a transition matrix to determine the likelihood of a customer’s risk grade migrating from one specified range of risk grades to a different specified range. Expected credit losses are calculated as the product of PD (adjusted for attrition), LGD and EAD. This methodology builds on default probabilities already incorporated into our risk grading process by utilizing pool-specific historical loss rates to calculate expected credit losses. These pool-specific historical loss rates may be adjusted for current macroeconomic assumptions, as further discussed below, and other factors such as differences in underwriting standards, portfolio mix, or when historical asset terms do not reflect the contractual terms of the financial assets being evaluated as of the measurement date. Each time we measure expected credit losses, we assess the relevancy of historical loss information and consider any necessary adjustments to address any differences in asset-specific characteristics. Due to their short-term nature, expected credit losses for overdrafts included in consumer and other loans are based solely upon a weighting of recent historical charge-offs over a period of three years. The measurement of expected credit losses is impacted by loan/borrower attributes and certain macroeconomic variables. Significant loan/borrower attributes utilized in our modeling processes include, among other things, (i) origination date, (ii) maturity date, (iii) payment type, (iv) collateral type and amount, (v) current risk grade, (vi) current unpaid balance and commitment utilization rate, (vii) payment status/delinquency history and (viii) expected recoveries of previously charged-off amounts. Significant macroeconomic variables utilized in our modeling processes include, among other things, (i) Gross State Product for Texas and U.S. Gross Domestic Product, (ii) selected market interest rates including U.S. Treasury rates, bank prime rate, 30-year fixed mortgage rate, BBB corporate bond rate, among others, (iii) unemployment rates, (iv) commercial and residential property prices in Texas and the U.S. as a whole, (v) West Texas Intermediate crude oil price and (vi) total stock market index. PD and PA were estimated by analyzing internally-sourced data related to historical performance of each loan pool over a complete economic cycle. PD and PA are adjusted to reflect the current impact of certain macroeconomic variables as well as their expected changes over a reasonable and supportable forecast period. We have determined that we are reasonably able to forecast the macroeconomic variables used in our modeling processes with an acceptable degree of confidence for a total of two years with the last twelve months of the forecast period encompassing a reversion process whereby the forecasted macroeconomic variables are reverted to their historical mean utilizing a rational, systematic basis. The macroeconomic variables utilized as inputs in our modeling processes were subjected to a variety of analysis procedures and were selected primarily based on statistical relevancy and correlation to our historical credit losses. By reverting these modeling inputs to their historical mean and considering loan/borrower specific attributes, our models are intended to yield a measurement of expected credit losses that reflects our average historical loss rates for periods subsequent to the twelve-month reversion period. The LGD is based on historical recovery averages for each loan pool, adjusted to reflect the current impact of certain macroeconomic variables as well as their expected changes over a two-year forecast period, with the final t

Premises and Equipment

Premises and Equipment	12 Months Ended
	Dec. 31, 2023
Property, Plant and Equipment [Abstract]
Premises and Equipment	Premises and Equipment and Lease Commitments Year-end premises and equipment were as follows: 2023 2022 Land $ 191,594 $ 170,938 Buildings 581,745 521,280 Technology, furniture and equipment 262,666 236,440 Leasehold improvements 230,642 209,398 Construction and projects in progress 36,910 39,506 Lease right-of-use assets 280,502 288,816 1,584,059 1,466,378 Less accumulated depreciation and amortization (394,026) (363,683) Total premises and equipment, net $ 1,190,033 $ 1,102,695 Depreciation of premises and equipment totaled $60.6 million in 2023, $57.4 million 2022 and $55.1 million in 2021. Lease Commitments . We lease certain office facilities and office equipment under operating leases. Rent expense for all operating leases totaled $50.5 million in 2023, $47.7 million in 2022 and $45.6 million in 2021. The components of total lease expense in 2023 and 2022 were as follows: 2023 2022 Amortization of lease right-of-use assets $ 34,137 $ 33,285 Short-term lease expense 2,576 2,208 Non-lease components (including taxes, insurance, common maintenance, etc.) 13,811 12,172 Total $ 50,524 $ 47,665 Right-of-use lease assets totaled $280.5 million and $288.8 million at December 31, 2023 and 2022, respectively, and are reported as a component of premises and equipment on our accompanying consolidated balance sheets. The related lease liabilities totaled $316.4 million and $321.9 million at December 31, 2023 and 2022, respectively, 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 $32.1 million during 2023 and $32.9 million during 2022. The following table reconciles future undiscounted lease payments due under non-cancelable operating leases (those amounts subject to recognition) to the aggregate operating lessee lease liability as of December 31, 2023: Future lease payments 2024 $ 34,712 2025 36,030 2026 35,891 2027 34,359 2028 32,319 Thereafter 218,152 Total undiscounted operating lease liability 391,463 Imputed interest 75,071 Total operating lease liability included in the accompanying balance sheet $ 316,392 Weighted-average lease term in years 12.88 Weighted-average discount rate 3.32%

Deposits

Deposits	12 Months Ended
	Dec. 31, 2023
Deposits [Abstract]
Deposits	Deposits Year-end deposits were as follows: 2023 2022 Non-interest-bearing demand deposits $ 14,926,094 $ 17,598,234 Interest-bearing deposits: Savings and interest checking 10,512,637 12,333,675 Money market accounts 10,997,279 12,227,247 Time accounts 5,484,558 1,795,040 Total interest-bearing deposits 26,994,474 26,355,962 Total deposits $ 41,920,568 $ 43,954,196 The following table presents additional information about our year-end deposits: 2023 2022 Deposits from foreign sources (primarily Mexico) $ 1,061,701 $ 1,048,943 Non-interest-bearing public funds deposits 675,016 788,040 Interest-bearing public funds deposits 630,455 758,761 Total deposits not covered by deposit insurance 22,393,786 23,839,797 Time deposits not covered by deposit insurance 2,339,716 430,128 Deposits from certain directors, executive officers and their affiliates 115,798 153,083 Scheduled maturities of time deposits at December 31, 2023 were as follows: 2024 $ 5,286,064 2025 28,829 2026 169,665 $ 5,484,558 Scheduled maturities of time deposits not covered by deposit insurance at December 31, 2023, were as follows: Due within 3 months or less $ 1,991,080 Due after 3 months and within 6 months 139,435 Due after 6 months and within 12 months 167,732 Due after 12 months 41,469 $ 2,339,716

Borrowed Funds

Borrowed Funds	12 Months Ended
	Dec. 31, 2023
Debt Disclosure [Abstract]
Borrowed Funds	Borrowed Funds Federal Funds Purchased and Securities Sold Under Agreements to Repurchase. Federal funds purchased are short-term borrowings that typically mature within one ninety thirty ninety Subordinated Notes. In March 2017, we issued $100 million of 4.50% subordinated notes that mature on March 17, 2027. The notes, which qualify as Tier 2 capital for Cullen/Frost, bear interest at the rate of 4.50% per annum, payable semi-annually on each March 17 and September 17. The notes are unsecured and subordinated in right of payment to the payment of our existing and future senior indebtedness and structurally subordinated to all existing and future indebtedness of our subsidiaries. Unamortized debt issuance costs related to these notes, totaled approximately $509 thousand and $665 thousand December 31, 2023 and 2022. Proceeds from sale of the notes were used for general corporate purposes. Junior Subordinated Deferrable Interest Debentures. At December 31, 2023 and 2022, we had $123.7 million of junior subordinated deferrable interest debentures issued to Cullen/Frost Capital Trust II (“Trust II”), a wholly owned Delaware statutory business trust. Unamortized debt issuance costs related to Trust II totaled $585 thousand and $643 thousand at December 31, 2023 and 2022. In October 2021, we redeemed $13.4 million of junior subordinated deferrable interest debentures issued to WNB Capital Trust I (“WNB Trust”), a wholly owned Delaware statutory business trust acquired in connection with the acquisition of WNB Bancshares, Inc. (“WNB”) in 2014. Trust II is a variable interest entity for which we are not the primary beneficiary and, as such, its accounts are not included in our consolidated financial statements. This was also the case with WNB Trust prior to its dissolution in 2021. See Note 1 - Summary of Significant Accounting Policies for additional information about our consolidation policy. Details of our transactions with the capital trust are presented below. Trust II was formed in 2004 for the purpose of issuing $120.0 million of floating rate (three-month term Secured Overnight Funding Rate “SOFR” plus a margin of approximately 1.81%) trust preferred securities, which represent beneficial interests in the assets of the trust. As of December 31, 2022, prior to the cessation of LIBOR in 2023, the trust preferred securities were indexed to three-month LIBOR plus a margin of 1.55%. The trust preferred securities will mature on March 1, 2034 and are currently redeemable with the approval of the Federal Reserve Board in whole or in part at our option. Distributions on the trust preferred securities are payable quarterly in arrears on March 1, June 1, September 1 and December 1 of each year. Trust II also issued $3.7 million of common equity securities to Cullen/Frost. The proceeds of the offering of the trust preferred securities and common equity securities were used to purchase $123.7 million of floating rate (three-month term SOFR plus a margin of approximately 1.81%, which was equal to 7.22% at December 31, 2023 and three-month LIBOR plus a margin of 1.55%, which was equal to 6.31%, at December 31, 2022) junior subordinated deferrable interest debentures issued by us, which have terms substantially similar to the trust preferred securities. We have the right at any time during the term of the debentures issued to Trust II to defer payments 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. Under the terms of the debentures, in the event that under certain circumstances there is an event of default under the debentures or 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. Payments of distributions on the trust preferred securities and payments on redemption of the trust preferred securities are guaranteed by us on a limited basis. We are obligated by agreement to pay any costs, expenses or liabilities of Trust II other than those arising under the trust preferred securities. Our obligations under the junior subordinated debentures, the related indenture, the trust agreement establishing the trust, the guarantee and the agreement as to expenses and liabilities, in the aggregate, constitute a full and unconditional guarantee by us of Trust II’s obligations under the trust preferred securities. Although the accounts of Trust II are not included in our consolidated financial statements, the trust preferred securities issued by Trust II are included in the capital of Cullen/Frost for regulatory capital purposes. See Note 8 - Capital and Regulatory Matters.

Off-Balance-Sheet Arrangements,

Off-Balance-Sheet Arrangements, Commitments, Guarantees and Contingencies	12 Months Ended
	Dec. 31, 2023
Commitments and Contingencies Disclosure [Abstract]
Off-Balance-Sheet Arrangements, Commitments, Guarantees and Contingencies	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 in the United States, are not included in our consolidated balance sheets. We enter into these transactions to meet the financing needs of our customers. 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. We enter into contractual commitments to extend credit, normally with fixed expiration dates or termination clauses, at specified rates and for specific purposes. Substantially all of our commitments to extend credit are contingent upon customers maintaining specific credit standards at the time of loan funding. Standby letters of credit are written conditional commitments issued by us to guarantee the performance of a customer to a third party. In the event the customer does not perform in accordance with the terms of the agreement with the third party, we would be required to fund the commitment. The maximum potential amount of future payments we could be required to make is represented by the contractual amount of the commitment. If the commitment were funded, we would be entitled to seek recovery from the customer. Our policies generally require that standby letter of credit arrangements contain security and debt covenants similar to those contained in loan agreements. We consider the fees collected in connection with the issuance of standby letters of credit to be representative of the fair value of our obligation undertaken in issuing the guarantee. In accordance with applicable accounting standards related to guarantees, we defer fees collected in connection with the issuance of standby letters of credit. The fees are then recognized in income proportionately over the life of the standby letter of credit agreement. The deferred standby letter of credit fees represent the fair value of our potential obligations under the standby letter of credit guarantees. Year-end financial instruments with off-balance-sheet risk are presented in the following table. Commitments and standby letters of credit are presented at contractual amounts; however, since many of these commitments are expected to expire unused or only partially used, the total amounts of these commitments do not necessarily reflect future cash requirements. 2023 2022 Commitments to extend credit $ 12,195,073 $ 12,137,957 Standby letters of credit 438,635 383,851 Deferred standby letter of credit fees 2,912 2,236 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. For the period of exposure, the estimate of expected credit losses considers both the likelihood that funding will occur and the amount expected to be funded over the estimated remaining life of the commitment or other off-balance-sheet exposure. The likelihood and expected amount of funding are based on historical utilization rates. 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. Estimating credit losses on amounts expected to be funded uses the same methodology as described for loans in Note 3 - Loans as if such commitments were funded. This methodology was also impacted by the model updates during the first quarter of 2023 as described in Note 3 - Loans. The overall approximate impact of the model updates was a $19.0 million decrease in modeled expected credit losses for off-balance-sheet credit exposures, though the impact of this decrease was largely offset with discretionary qualitative adjustments. The following table details activity in the allowance for credit losses on off-balance-sheet credit exposures. 2023 2022 2021 Beginning balance $ 58,593 $ 50,314 $ 44,152 Credit loss expense (benefit) (6,842) 8,279 6,162 Ending balance $ 51,751 $ 58,593 $ 50,314 Credit Card Guarantees . We guarantee the credit card debt of certain customers to the merchant bank that issues the cards. At December 31, 2023 and 2022, the guarantees totaled approximately $5.5 million and $8.0 million, of which amounts, $762 thousand and $897 thousand were fully collateralized. Trust Accounts . We hold certain assets which are not included in our consolidated balance sheets including assets held in fiduciary or custodial capacity on behalf of our trust customers. The estimated fair value of trust assets was approximately $47.2 billion and $42.9 billion at December 31, 2023 and 2022, respectively. These assets are primarily composed of equity securities, fixed income securities, alternative investments and cash equivalents, among other things. Executive Change-In-Control Severance Plan . We maintain a change-in-control severance plan for the benefit of certain executive officers. Under this plan, each covered person could receive, upon the effectiveness of a change-in-control, two to three times (depending on the person) their base compensation plus the target bonus established for the year, and any unpaid base salary and pro rata target bonus for the year in which the termination occurs, including vacation pay. Additionally, the executive’s insurance benefits will continue for two to three full years after the termination and all long-term incentive awards will immediately vest. Litigation . We are subject to various claims and legal actions that have arisen in the course of conducting business. Management does not expect the ultimate disposition of these matters to have a material adverse impact on our financial statements.

Capital and Regulatory Matters

Capital and Regulatory Matters	12 Months Ended
	Dec. 31, 2023
Broker-Dealer, Net Capital Requirement, SEC Regulation [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 and Frost Bank are each required to comply with applicable capital adequacy standards established by the Federal Reserve Board (the “Basel III Capital Rules”). Quantitative measures established by the Basel III Capital Rules designed to ensure capital adequacy require the maintenance of minimum amounts and ratios (set forth below) of Common Equity Tier 1 capital, Tier 1 capital and Total capital (as defined in the regulations) to risk-weighted assets (as defined), and of Tier 1 capital to adjusted quarterly average assets (as defined). Cullen/Frost’s and Frost Bank’s Common Equity Tier 1 capital 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 Common Equity Tier 1. We also elected to exclude the effects of credit loss accounting under CECL from Common Equity Tier 1 capital for a five Tier 1 capital includes Common Equity Tier 1 capital and additional Tier 1 capital. For Cullen/Frost, additional Tier 1 capital at December 31, 2023 and 2022 included $145.5 million of 4.450% non-cumulative perpetual preferred stock, the details of which is are further discussed below. Frost Bank did not have any additional Tier 1 capital beyond Common Equity Tier 1 at December 31, 2023 or 2022. 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 allowance for credit losses on securities, loans and off-balance sheet exposures. Tier 2 capital for Cullen/Frost also includes trust preferred securities that were excluded from Tier 1 capital and qualified subordinated debt. Cullen/Frost's Tier 2 capital included $120.0 million of trust preferred securities at both December 31, 2023 and 2022. Cullen/Frost's Tier 2 Capital also included $60.0 million at December 31, 2023 and $80.0 million at December 31, 2022 related to the permissible portion of our aggregate $100 million of 4.50% subordinated notes. The permissible portion of qualified subordinated notes decreases 20% per year during the final five The Common Equity Tier 1, Tier 1 and Total capital ratios are calculated by dividing the respective capital amounts by risk-weighted assets. Risk-weighted assets are calculated based on regulatory requirements and include total assets, with certain exclusions, allocated by risk weight category, and certain off-balance-sheet items, among other things. The leverage ratio is calculated by dividing Tier 1 capital by adjusted quarterly average total assets, which exclude goodwill and other intangible assets, among other things. The Basel III Capital Rules require Cullen/Frost and Frost Bank to maintain (i) a minimum ratio of Common Equity Tier 1 capital to risk-weighted assets of at least 4.5%, plus a 2.5% “capital conservation buffer” (which is added to the 4.5% Common Equity Tier 1 capital ratio, effectively resulting in a minimum ratio of Common Equity Tier 1 capital to risk-weighted assets of at least 7.0%), (ii) a minimum ratio of Tier 1 capital to risk-weighted assets of at least 6.0%, plus the capital conservation buffer (which is added to the 6.0% Tier 1 capital ratio, effectively resulting in a minimum Tier 1 capital ratio of 8.5%), (iii) a minimum ratio of Total capital (that is, Tier 1 plus Tier 2) to risk-weighted assets of at least 8.0%, plus the capital conservation buffer (which is added to the 8.0% total capital ratio, effectively resulting in a minimum total capital ratio of 10.5%) and (iv) a minimum leverage ratio of 4.0%, calculated as the ratio of Tier 1 capital to average quarterly assets. The capital conservation buffer is designed to absorb losses during periods of economic stress and, as detailed above, effectively increases the minimum required risk-weighted capital ratios. Banking institutions with a ratio of Common Equity Tier 1 capital to risk-weighted assets below the effective minimum (4.5% plus the capital conservation buffer and, if applicable, the “countercyclical capital buffer,” which is discussed below) will face constraints on dividends, equity repurchases and compensation based on the amount of the shortfall and the institution's “eligible retained income” (that is, four quarter trailing net income, net of distributions and tax effects not reflected in net income). The countercyclical capital buffer is applicable to only certain covered institutions and does not have any current applicability to Cullen/Frost or Frost Bank. The following table presents actual and required capital ratios as of December 31, 2023 and December 31, 2022 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. Actual Minimum Capital Required to be Considered Well Capitalized (1) Capital Ratio Capital Ratio Capital Ratio 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 2022 Common Equity Tier 1 to Risk-Weighted Assets Cullen/Frost $ 3,751,200 12.85 % $ 2,042,876 7.00 % N/A N/A Frost Bank 3,789,056 13.00 2,040,388 7.00 $ 1,894,646 6.50 % Tier 1 Capital to Risk-Weighted Assets Cullen/Frost 3,896,652 13.35 2,480,635 8.50 1,751,036 6.00 Frost Bank 3,789,056 13.00 2,477,614 8.50 2,331,872 8.00 Total Capital to Risk-Weighted Assets Cullen/Frost 4,330,982 14.84 3,064,313 10.50 2,918,394 10.00 Frost Bank 4,023,386 13.80 3,060,583 10.50 2,914,841 10.00 Leverage Ratio Cullen/Frost 3,896,652 7.29 2,136,680 4.00 N/A N/A Frost Bank 3,789,056 7.09 2,136,316 4.00 2,670,395 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 December 31, 2023, capital levels for 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 December 31, 2023 for 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 December 31, 2023, that Cullen/Frost and Frost Bank meet all capital adequacy requirements to which they are subject. Series B Preferred Stock. In November 2020, we issued 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). Each holder of depositary shares will be entitled, in proportion to the applicable fraction of a share of Series B Preferred Stock represented by such depositary shares, to all rights and preferences of the Series B Preferred Stock represented thereby (including dividend, voting, redemption, and liquidation rights). Such rights must be exercised through the depositary. Dividends on the Series B Preferred Stock will be non-cumulative and, if declared, accrue and are payable quarterly, in arrears, at a rate of 4.450% per annum. 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. The Series B Preferred Stock is perpetual and has no maturity date. We may redeem the Series B Preferred Stock at our option (i) in whole or in part, from time to time, on any dividend payment date on or after December 15, 2025 or (ii) in whole but not in part, within 90 days following certain changes in laws or regulations impacting the regulatory capital treatment of the Series B Preferred Stock, in either case, at a redemption price equal to $1,000 per share of Series B Preferred Stock (equivalent to $25 per depositary share), plus any declared and unpaid dividends for prior dividend periods and accrued but unpaid dividends (whether or not declared) for the then-current dividend period prior to but excluding the redemption date. If we redeem the Series B Preferred Stock, the depositary is expected redeem a proportionate number of depositary shares. Neither the holders of Series B Preferred Stock nor holders of depositary shares will have the right to require the redemption or repurchase of the Series B Preferred Stock or the depositary shares. Purchases of Equity Securities. From time to time, our board of directors has authorized stock repurchase plans. On January 25, 2023, our board of directors authorized a $100.0 million stock repurchase plan (the “2023 Repurchase Plan”), allowing us to repurchase shares of our common stock over a one No shares were repurchased under a publicly announced stock repurchase plan during 2022 or 2021. Shares repurchased in connection with the vesting of certain share awards totaled 31,351 at a total cost of $4.4 million in 2022 and 31,317 at a total cost of $3.9 million in 2021. On January 24, 2024, our board of directors authorized a $150.0 million stock repurchase plan (the “2024 Repurchase Plan”), allowing us to repurchase shares of our common stock over a one In July 2019, the federal bank regulators adopted final rules (the “Capital Simplifications Rules”) that, among other things, eliminated the standalone prior approval requirement in the Basel III Capital Rules for any repurchase of common stock. In certain circumstances, Cullen/Frost’s repurchases of its common stock may be subject to a prior approval or notice requirement under other regulations, policies or supervisory expectations of the Federal Reserve Board. Any redemption or repurchase of preferred stock or subordinated debt remains subject to the prior approval of the Federal Reserve Board. In August 2022, the Inflation Reduction Act of 2022 (the “IRA”) was enacted. Among other things, the IRA imposes a new 1% excise tax on the fair market value of stock repurchased after December 31, 2022 by publicly traded U.S. corporations. With certain exceptions, the value of stock repurchased is determined net of stock issued in the year, including shares issued pursuant to compensatory arrangements. 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 December 31, 2023, Frost Bank could pay aggregate dividends of up to $1.1 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. Insider Trading Policies and Procedures. Our board of directors has adopted insider trading policies and procedures governing the purchase, sale, and/or other dispositions of our securities by directors, officers and employees, or by Cullen/Frost itself. These policies have been reasonably designed to promote compliance with insider trading laws, rules and regulations, and applicable New York Stock Exchange listing standards.

Earnings Per Common Share

Earnings Per Common Share	12 Months Ended
	Dec. 31, 2023
Earnings Per Share [Abstract]
Earnings Per Common Share	Earnings Per Common Share Earnings Per Common Share . Earnings per common share is computed using the two-class method. Basic earnings per common share is computed by dividing net earnings allocated to common stock by the weighted-average number of common shares outstanding during the applicable period, excluding outstanding participating securities. Participating securities include non-vested stock awards/stock units, deferred stock units and performance stock units (during the performance period), though no actual shares of common stock related to any type of stock unit have been issued. Non-vested stock awards/stock units and deferred stock units are considered participating securities because holders of these securities receive non-forfeitable dividends at the same rate as holders of our common stock. Holders of performance stock units receive dividend equivalent payments for dividends paid during the performance period at the vesting date of the award based upon the number of units that ultimately vest. Diluted earnings per common share is computed using the weighted-average number of shares determined for the basic earnings per common share computation plus the dilutive effect of stock compensation using the treasury stock method. 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. 2023 2022 2021 Net Income $ 597,973 $ 579,150 $ 443,079 Less: Preferred stock dividends 6,675 6,675 7,157 Net income available to common shareholders 591,298 572,475 435,922 Less: Earnings allocated to participating securities 6,283 5,210 3,881 Net earnings allocated to common stock $ 585,015 $ 567,265 $ 432,041 Distributed earnings allocated to common stock $ 229,749 $ 207,924 $ 187,202 Undistributed earnings allocated to common stock 355,266 359,341 244,839 Net earnings allocated to common stock $ 585,015 $ 567,265 $ 432,041 Weighted-average shares outstanding for basic earnings per common share 64,204,239 64,156,870 63,612,658 Dilutive effect of stock compensation 200,594 363,648 489,462 Weighted-average shares outstanding for diluted earnings per common share 64,404,833 64,520,518 64,102,120

Employee Benefit Plans

Employee Benefit Plans	12 Months Ended
	Dec. 31, 2023
Retirement Benefits [Abstract]
Employee Benefit Plans	Employee Benefit Plans Retirement Plans Retirement Plan and Restoration Plan. We maintain a non-contributory defined benefit plan (the “Retirement Plan”) that was frozen as of December 31, 2001. The plan provides pension and death benefits to substantially all employees who were at least 21 years of age and had completed at least one year of service prior to December 31, 2001. Defined benefits are provided based on an employee’s final average compensation and years of service at the time the plan was frozen and age at retirement. The freezing of the plan provides that future salary increases will not be considered. Our funding policy is to contribute yearly, at least the amount necessary to satisfy the funding standards of the Employee Retirement Income Security Act (“ERISA”). Our Restoration of Retirement Income Plan (the “Restoration Plan”) provides benefits for eligible employees that are in excess of the limits under Section 415 of the Internal Revenue Code of 1986, as amended, that apply to the Retirement Plan. The Restoration Plan is designed to comply with the requirements of ERISA. The entire cost of the plan, which was also frozen as of December 31, 2001, is supported by our contributions. We use a December 31 measurement date for our defined benefit plans. Combined activity in our defined benefit pension plans was as follows: 2023 2022 2021 Change in plan assets: Fair value of plan assets at beginning of year $ 161,823 $ 197,747 $ 182,088 Actual return on plan assets 22,477 (26,108) 24,908 Employer contributions 1,105 1,114 1,236 Benefits paid (10,794) (10,930) (10,485) Fair value of plan assets at end of year 174,611 161,823 197,747 Change in benefit obligation: Benefit obligation at beginning of year 143,944 185,925 197,593 Interest cost 6,983 4,017 3,341 Actuarial (gain) loss 2,239 (35,068) (4,524) Benefits paid (10,794) (10,930) (10,485) Benefit obligation at end of year 142,372 143,944 185,925 Funded status of the plan at end of year and accrued benefit (liability) recognized $ 32,239 $ 17,879 $ 11,822 Accumulated benefit obligation at end of year $ 142,372 $ 143,944 $ 185,925 Certain disaggregated information related to our defined benefit pension plans as of year-end was as follows: Retirement Plan Restoration Plan 2023 2022 2023 2022 Projected benefit obligation $ 130,750 $ 131,648 $ 11,622 $ 12,296 Accumulated benefit obligation 130,750 131,648 11,622 12,296 Fair value of plan assets 174,611 161,823 — — Funded status of the plan at end of year and accrued benefit (liability) recognized 43,861 30,175 (11,622) (12,296) The components of the combined net periodic cost (benefit) for our defined benefit pension plans are presented in the table below. 2023 2022 2021 Expected return on plan assets, net of expenses $ (10,959) $ (13,966) $ (12,839) Interest cost on projected benefit obligation 6,983 4,017 3,341 Net amortization and deferral 3,479 2,964 6,116 Net periodic expense (benefit) $ (497) $ (6,985) $ (3,382) Amounts related to our defined benefit pension plans recognized as a component of other comprehensive income were as follows: 2023 2022 2021 Net actuarial gain (loss) $ 12,757 $ (2,041) $ 22,709 Deferred tax (expense) benefit (2,679) 429 (4,769) Other comprehensive income (loss), net of tax $ 10,078 $ (1,612) $ 17,940 Amounts recognized as a component of accumulated other comprehensive loss as of year-end that have not been recognized as a component of the combined net periodic benefit cost of our defined benefit pension plans are presented in the following table. 2023 2022 Net actuarial loss $ (30,918) $ (43,675) Deferred tax benefit 6,493 9,172 Amounts included in accumulated other comprehensive income/loss, net of tax (24,425) (34,503) The weighted-average assumptions used to determine the benefit obligations as of the end of the years indicated and the net periodic benefit cost for the years indicated are presented in the table below. Because the plans were frozen, increases in compensation are not considered after 2001. 2023 2022 2021 Benefit obligations: Discount rate 4.95 % 5.14 % 2.79 % Net periodic benefit cost: Discount rate 5.14 % 2.79 % 2.43 % Expected return on plan assets 7.00 7.25 7.25 Management uses an asset allocation optimization model to analyze the potential risks and rewards associated with various asset allocation strategies on a quarterly basis. As of December 31, 2023, management’s investment objective for our defined benefit plans is to achieve current income with growth through price appreciation. This strategy provides for a target asset allocation of approximately 31% invested in equity securities, approximately 63% invested in fixed income debt securities with any remainder invested in cash or short-term cash equivalents. The asset allocation optimization process provides portfolio allocations which best represent the potential risk associated with a given asset allocation over a full market cycle. This is used to help management determine an appropriate mix of assets in order to achieve the plan's long term investment goals. The plan assets are reviewed annually to determine if the obligations can be met with the current investment mix and funding strategy. The major categories of assets in our Retirement Plan as of year-end are presented in the following table. Assets are segregated by the level of the valuation inputs within the fair value hierarchy established by ASC Topic 820 “Fair Value Measurements and Disclosures,” utilized to measure fair value (see Note 16 - Fair Value Measurements). Our Restoration Plan is unfunded. 2023 2022 Level 1: Mutual funds and ETFs $ 38,793 $ 154,391 U.S. Treasury 26,633 — Common stock 13,001 — Cash and cash equivalents 1,241 7,432 Level 2: Corporate bonds and notes 58,669 — U.S. government agency securities 7,041 — States and political subdivisions 29,233 — Total fair value of plan assets $ 174,611 $ 161,823 Mutual funds and exchange traded funds (“ETFs”) include various equity, fixed-income and blended funds with varying investment strategies. Approximately 85% of mutual fund investments consist of equity investments as of December 31, 2023. The investment objective of equity funds and other equity investments is long-term capital appreciation with current income. The remaining mutual fund investments consist of U.S. fixed-income securities, including investment-grade U.S. Treasury securities, U.S. government agency securities and mortgage-backed securities, corporate bonds and notes and collateralized mortgage obligations. The investment objective of fixed-income funds and other fixed-income investments is to maximize investment return while preserving investment principal. Our investment strategies prohibit selling assets short and the use of derivatives. Additionally, our defined benefit plans do not directly invest in real estate, commodities, or private investments. The asset allocation optimization model is used to estimate the expected long-term rate of return for a given asset allocation strategy. Expectations of returns for each asset class are based on comprehensive reviews of historical data and economic/financial market theory. During periods with volatile interest rates and equity security prices, the model may call for changes in the allocation of plan investments to achieve desired returns. Management assumed a long-term rate of return of 7.00% in the determination of the net periodic benefit cost for 2023. The expected long-term rate of return on assets was selected from within the reasonable range of rates determined by historical real returns, net of inflation, for the asset classes covered by the plan’s investment policy and projections of inflation over the long-term period during which benefits are payable to plan participants. As of December 31, 2023, expected future benefit payments related to our defined benefit plans were as follows: 2024 $ 12,022 2025 11,966 2026 11,967 2027 11,874 2028 11,511 2029 through 2033 50,461 $ 109,801 We expect to contribute $1.1 million to the defined benefit plans during 2024. Savings Plans 401(k) Stock Purchase Plan and Other Plans. We maintain a 401(k) stock purchase plan that permits each participant to make before-tax contributions in an amount not less than 2% and not exceeding 50% of eligible compensation and subject to dollar limits from Internal Revenue Service regulations. We match 100% of the employee’s contributions to the plan based on the amount of each participant’s contributions up to a maximum of 6% of eligible compensation. Eligible employees must complete 30 days of service in order to enroll and vest in our matching contributions immediately. Our matching contribution is initially invested in the common stock of Cullen/Frost. Employees may immediately reallocate our matching portion, as well as invest their individual contribution, to any of a variety of investment alternatives offered under the 401(k) Plan. We may also make discretionary profit sharing contributions to eligible participants. All profit sharing contributions to the plan are made at our discretion and may be made without regard to current or accumulated profits. Contributions are generally allocated to eligible participants uniformly, based upon compensation, age and/or other factors. Plan participants self-direct the investment of allocated contributions by choosing from a menu of investment options. Profit sharing contributions are subject to withdrawal restrictions and participants vest in their allocated contributions after three years of service. Expense related to the plan, including both 401(k) and profit sharing contributions, totaled $32.3 million in 2023, $28.0 million in 2022 and $23.8 million in 2021. We maintain a thrift incentive stock purchase plan and a separate non-qualified profit sharing plan to offer certain employees, whose participation in the 401(k) plan is limited, an alternative means of receiving comparable benefits. Expense related to these plans was not significant during 2023, 2022 and 2021. Stock Compensation Plans We have three active stock compensation plans (the 2005 Omnibus Incentive Plan, the 2007 Outside Directors Incentive Plan and the 2015 Omnibus Incentive Plan). All of the plans have been approved by our shareholders. During 2015, the 2015 Omnibus Incentive Plan (“2015 Plan”) was established to replace both the 2005 Omnibus Incentive Plan (“2005 Plan”) and the 2007 Outside Directors Incentive Plan (the “2007 Directors Plan”). All remaining shares authorized for grant under the superseded 2005 Plan and 2007 Directors Plan were transferred to the 2015 Plan. Our stock compensation plans were established to (i) motivate superior performance by means of performance-related incentives, (ii) encourage and provide for the acquisition of an ownership interest in our company by employees and non-employee directors and (iii) enable us to attract and retain qualified and competent persons as employees and to serve as members of our board of directors. Under the 2015 Plan, we may grant, among other things, nonqualified stock options, incentive stock options, stock awards, stock appreciation rights, restricted stock units, performance share units or any combination thereof to certain employees and non-employee directors. Any of the authorized shares may be used for any type of award allowable under the Plan. The Compensation and Benefits Committee (“Committee”) of our Board of Directors has sole authority to (i) establish the awards to be issued, (ii) select the employees and non-employee directors to receive awards, and (iii) approve the terms and conditions of each award contract. Each award under the stock plans is evidenced by an award agreement that specifies the award price, the duration of the award, the number of shares to which the award pertains, and such other provisions as the Committee determines. For stock options, the option price for each grant is at least equal to the fair market value of a share of Cullen/Frost’s common stock on the date of grant. Options granted expire at such time as the Committee determines at the date of grant and in no event does the exercise period exceed a maximum of ten years. As defined in the plans, outstanding awards may immediately vest upon a change-in-control of Cullen/Frost and, in the case of awards granted under the 2015 Plan, subsequent termination resulting from the change in control. A combined summary of activity in our active stock plans is presented in the table. Performance stock units outstanding are presented assuming attainment of the maximum payout rate as set forth by the performance criteria. The target award level for performance stock units granted in 2023, 2022 and 2021 was 66,471, 35,015 and 30,723, respectively. As of December 31, 2023, there were 205,090 shares remaining available for grant for future awards. Director Deferred Non-Vested Performance Stock Units Outstanding Stock Options Number of Units Weighted- Number Weighted- Number of Units Weighted- Number Weighted- January 1, 2020 52,860 $ 75.47 470,359 $ 86.24 201,257 $ 77.18 1,739,559 $ 66.11 Granted 5,940 117.90 95,258 130.36 46,086 121.46 — — Exercised/vested (2,499) 92.03 (88,250) 98.90 (35,131) 92.27 (861,878) 63.14 Forfeited/expired — — (28,030) 87.08 (9,752) 75.70 — — December 31, 2021 56,301 79.21 449,337 93.05 202,460 84.71 877,681 69.02 Granted 5,382 133.67 119,176 142.56 52,527 133.40 — — Exercised/vested (16,022) 74.89 (97,154) 94.81 (25,180) 87.18 (261,454) 63.72 Forfeited/expired — — (6,040) 93.28 (16,058) 87.18 — — December 31, 2022 45,661 87.15 465,319 105.36 213,749 96.20 616,227 71.27 Granted 8,503 103.47 217,561 85.39 99,710 74.71 — — Exercised/vested — — (108,920) 94.00 (28,151) 85.74 (130,286) 71.37 Forfeited/expired — — (7,154) 114.53 (18,254) 85.74 — — December 31, 2023 54,164 89.71 566,806 99.77 267,054 89.99 485,941 71.25 Options awarded to employees generally have a ten four three four Performance stock units represent shares potentially issuable in the future. For performance stock units granted in 2023, 2022 and 2021, issuance is based upon the measure of our achievement of growth in adjusted net revenue, averaged over the three-year performance period, compared to the 2023, 2022 and 2021 base-year amounts, respectively. For performance stock units granted prior to 2021, issuance is based upon the measure of our achievement of relative return on assets over a three-year performance period compared to an identified peer group's achievement of relative return on assets over the same three-year performance period. Performance stock units are eligible to receive equivalent dividend payments as such dividends are declared on our common stock during the performance period. Equivalent dividend payments are based upon the ultimate number of shares issued under each performance award and are deferred until such time that the units vest and shares are issued. Other information regarding options outstanding and exercisable as of December 31, 2023 is as follows: Options Outstanding Options Exercisable Range of Number Weighted- Weighted- Number Weighted- $ 65.01 to $ 70.00 270,031 $ 65.11 1.80 270,031 $ 65.11 75.01 to 80.00 215,910 78.92 0.82 215,910 78.92 Total 485,941 71.25 1.37 485,941 71.25 Total intrinsic value $ 18,098 $ 18,098 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: 2023 2022 2021 New shares issued from available authorized shares 49,887 118,389 — Shares issued from available treasury stock 217,470 281,421 987,758 Total 267,357 399,810 987,758 Proceeds from stock option exercises $ 9,299 $ 16,659 $ 54,417 Intrinsic value of stock options exercised 3,614 19,616 43,904 Fair value of restricted/director deferred stock units vested 13,445 19,308 15,751 Stock-based Compensation Expense. 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 restricted stock units granted to all participants, the service period does not extend past the date the participant reaches 65 years of age. Director 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 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. 2023 2022 2021 Non-vested restricted stock units $ 16,734 $ 13,162 $ 9,977 Director deferred stock units 880 720 700 Performance stock units 6,976 4,440 2,076 Total $ 24,590 $ 18,322 $ 12,753 Income tax benefit $ 4,120 $ 2,969 $ 1,713 Unrecognized stock-based compensation expense and the weighted-average period over which the expense is expected to be recognized at December 31, 2023 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. Unrecognized Expense Weighted-Average Number of Years for Expense Recognition Non-vested restricted stock units $ 22,665 2.13 Performance stock units 9,784 2.25 Total $ 32,449 Valuation of Stock-Based Compensation . For the purposes of recognizing stock-based compensation expense, the fair value of non-vested restricted stock units and director deferred stock units is generally the market price of the stock on the measurement date, which, for us, is the date of the award. The fair value of performance stock units is determined in a similar manner except that the market price of the stock on the measurement date is discounted by the present value of the dividends expected to be paid on our common stock during the service period of the award because dividend equivalent payments on performance stock units are deferred until such time that the units vest and shares are issued. In applying this discount to the market price of our stock on the measurement date, we assumed we would pay a flat quarterly dividend during the service period equal to our most recent dividend payment, which was $0.92, $0.87 and $0.75 in 2023, 2022 and 2021, respectively, discounted at a weighted-average risk-free rate of 5.01%, 4.45% and 0.77% in 2023, 2022 and 2021, respectively.

Other Non-Interest Income and E

Other Non-Interest Income and Expense	12 Months Ended
	Dec. 31, 2023
Other Income and Expenses [Abstract]
Other Non-Interest Income and Expense	Other Non-Interest Income and Expense Other non-interest income and expense totals are presented in the following table. Components of these totals exceeding 1% of the aggregate of total net interest income and total non-interest income for any of the years presented are stated separately. 2023 2022 2021 Other non-interest income: Other $ 54,941 $ 45,217 $ 48,528 Total $ 54,941 $ 45,217 $ 48,528 Other non-interest expense: Professional services $ 53,932 $ 40,908 $ 34,747 Advertising, promotions and public relations 48,608 39,994 34,539 Other 126,827 113,799 102,868 Total $ 229,367 $ 194,701 $ 172,154 In the ordinary course of business, we transact with certain directors and/or their affiliates. Payments for services provided totaled $1.3 million in 2023, $545 thousand in 2022 and $257 thousand in 2021.

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2023
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes Income tax expense was as follows: 2023 2022 2021 Current income tax expense $ 129,229 $ 94,595 $ 38,675 Deferred income tax expense (benefit) (14,829) (4,918) 7,784 Income tax expense, as reported $ 114,400 $ 89,677 $ 46,459 Effective tax rate 16.1 % 13.4 % 9.5 % A reconciliation between reported income tax expense and the amounts computed by applying the U.S. federal statutory income tax rate of 21% to income before income taxes is presented in the following table. 2023 2022 2021 Income tax expense computed at the statutory rate $ 149,598 $ 140,454 $ 102,803 Effect of tax-exempt interest (43,114) (50,602) (50,740) Tax benefit on dividends paid in our 401k plan (2,135) (1,854) (1,764) Net tax benefit from stock-based compensation (894) (4,602) (7,877) Non-deductible FDIC premiums 5,263 3,277 2,629 Non-deductible compensation 2,591 2,250 1,773 Non-deductible meals and entertainment 1,692 683 625 Tax basis adjustment of premises and equipment — — (1,026) Other 1,399 71 36 Income tax expense, as reported $ 114,400 $ 89,677 $ 46,459 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. Year-end deferred taxes are presented in the table below. Deferred taxes are based on the U.S. statutory federal income tax rate of 21%. 2023 2022 Deferred tax assets: Net unrealized loss on securities available for sale and transferred securities $ 291,023 $ 349,237 Lease liabilities under operating leases 66,442 67,608 Allowance for credit losses 62,592 60,137 Bonus accrual 9,680 11,204 FDIC deposit insurance special assessment 9,468 — Stock-based compensation 7,712 6,622 Net actuarial loss on defined benefit post-retirement benefit plans 6,493 9,172 Deferred loan and lease origination fees 4,129 3,675 Other 5,892 6,109 Total gross deferred tax assets 463,431 513,764 Deferred tax liabilities: Right-of-use assets under operating leases (58,905) (60,651) Premises and equipment (42,640) (45,647) Intangible assets (18,106) (17,732) Defined benefit post-retirement benefit plans (13,073) (12,730) Other (2,368) (2,601) Total gross deferred tax liabilities (135,092) (139,361) Net deferred tax asset (liability) $ 328,339 $ 374,403 No valuation allowance for deferred tax assets was recorded at December 31, 2023 and 2022 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. There were no unrecognized tax benefits during any of 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)	12 Months Ended
	Dec. 31, 2023
Equity [Abstract]
Other Comprehensive Income (Loss)	Other Comprehensive Income (Loss) The tax effects allocated to each component of other comprehensive income (loss) were as follows: Before Tax Tax Expense, Net of Tax 2023 Securities available for sale and transferred securities: Change in net unrealized gain/loss during the period $ 277,926 $ 58,364 $ 219,562 Change in net unrealized gain on securities transferred to held to maturity (649) (136) (513) Reclassification adjustment for net (gains) losses included in net income (66) (14) (52) Total securities available for sale and transferred securities 277,211 58,214 218,997 Defined-benefit post-retirement benefit plans: Change in the net actuarial gain/loss 9,278 1,948 7,330 Reclassification adjustment for net amortization of actuarial gain/loss included in net income as a component of net periodic cost (benefit) 3,479 731 2,748 Total defined-benefit post-retirement benefit plans 12,757 2,679 10,078 Total other comprehensive income (loss) $ 289,968 $ 60,893 $ 229,075 Before Tax Tax Expense, Net of Tax 2022 Securities available for sale and transferred securities: Change in net unrealized gain/loss during the period $ (2,143,567) $ (450,149) $ (1,693,418) Change in net unrealized gain on securities transferred to held to maturity (737) (155) (582) Total securities available for sale and transferred securities (2,144,304) (450,304) (1,694,000) Defined-benefit post-retirement benefit plans: Change in the net actuarial gain/loss (5,005) (1,051) (3,954) Reclassification adjustment for net amortization of actuarial gain/loss included in net income as a component of net periodic cost (benefit) 2,964 622 2,342 Total defined-benefit post-retirement benefit plans (2,041) (429) (1,612) Total other comprehensive income (loss) $ (2,146,345) $ (450,733) $ (1,695,612) 2021 Securities available for sale and transferred securities: Change in net unrealized gain/loss during the period $ (231,355) $ (48,585) $ (182,770) Change in net unrealized gain on securities transferred to held to maturity (971) (204) (767) Reclassification adjustment for net (gains) losses included in net income (69) (14) (55) Total securities available for sale and transferred securities (232,395) (48,803) (183,592) Defined-benefit post-retirement benefit plans: Change in the net actuarial gain/loss 16,593 3,485 13,108 Reclassification adjustment for net amortization of actuarial gain/loss included in net income as a component of net periodic cost (benefit) 6,116 1,284 4,832 Total defined-benefit post-retirement benefit plans 22,709 4,769 17,940 Total other comprehensive income (loss) $ (209,686) $ (44,034) $ (165,652) Activity in accumulated other comprehensive income, net of tax, was as follows: Securities Defined Accumulated Balance January 1, 2023 $ (1,313,791) $ (34,503) $ (1,348,294) Other comprehensive income (loss) before reclassification 219,049 7,330 226,379 Reclassification of amounts included in net income (52) 2,748 2,696 Net other comprehensive income (loss) during period 218,997 10,078 229,075 Balance December 31, 2023 $ (1,094,794) $ (24,425) $ (1,119,219) Balance January 1, 2022 $ 380,209 $ (32,891) $ 347,318 Other comprehensive income (loss) before reclassification (1,694,000) (3,954) (1,697,954) Reclassification of amounts included in net income — 2,342 2,342 Net other comprehensive income (loss) during period (1,694,000) (1,612) (1,695,612) Balance December 31, 2022 $ (1,313,791) $ (34,503) $ (1,348,294) Balance January 1, 2021 $ 563,801 $ (50,831) $ 512,970 Other comprehensive income (loss) before reclassification (183,537) 13,108 (170,429) Reclassification of amounts included in net income (55) 4,832 4,777 Net other comprehensive income (loss) during period (183,592) 17,940 (165,652) Balance December 31, 2021 $ 380,209 $ (32,891) $ 347,318

Derivative Financial Instrument

Derivative Financial Instruments	12 Months Ended
	Dec. 31, 2023
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 interest rate swaps, caps and floors to mitigate exposure to interest rate risk and to facilitate the needs of our customers. Our objectives for utilizing these derivative instruments are described below: We have entered into certain interest rate swap contracts that are matched to specific fixed-rate commercial loans or leases that we have entered into with our customers. These contracts have been designated as hedging instruments to hedge the risk of changes in the fair value of the underlying commercial loan/lease due to changes in interest rates. The related contracts are structured so that the notional amounts reduce over time to generally match the expected amortization of the underlying loan/lease. We have entered into certain interest rate swap, cap and floor contracts that are not designated as hedging instruments. These derivative contracts relate to transactions in which we enter into an interest rate swap, cap and/or floor with a customer while at the same time entering into an offsetting interest rate swap, cap and/or floor with a third-party financial institution. In connection with each swap transaction, we agree to pay interest to the customer on a notional amount at a variable interest rate and receive interest from the customer on a similar notional amount at a fixed interest rate. At the same time, we agree to pay a third-party financial institution the same fixed interest rate on the same notional amount and receive the same variable interest rate on the same notional amount. The transaction allows our customer to effectively convert a variable rate loan to a fixed rate. Because we act as an intermediary for our customer, 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. The notional amounts and estimated fair values of interest rate derivative contracts outstanding at December 31, 2023 and 2022 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 December 31, 2023 and 2022. December 31, 2023 December 31, 2022 Notional Estimated Notional Estimated Derivatives designated as hedges of fair value: Financial institution counterparties: Loan/lease interest rate swaps - assets $ — $ — $ 1,614 $ 19 Non-hedging interest rate derivatives: Financial institution counterparties: Loan/lease interest rate swaps - assets 1,040,659 58,486 1,165,812 70,416 Loan/lease interest rate swaps - liabilities 617,266 (20,293) 78,798 (1,102) Loan/lease interest rate caps - assets 275,000 11,747 246,442 15,256 Customer counterparties: Loan/lease interest rate swaps - assets 617,266 20,482 53,570 1,102 Loan/lease interest rate swaps - liabilities 1,040,659 (58,485) 1,175,563 (79,175) Loan/lease interest rate caps - liabilities 275,000 (11,747) 246,442 (15,256) The weighted-average rates paid and received for interest rate swaps outstanding at December 31, 2023 were as follows: Weighted-Average Interest Interest Interest rate swaps: Non-hedging interest rate swaps - financial institution counterparties 4.72 % 5.22 % Non-hedging interest rate swaps - customer counterparties 5.22 4.72 The weighted-average strike rate for outstanding interest rate caps was 3.69% at December 31, 2023. 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. December 31, 2023 December 31, 2022 Notional Notional Estimated Notional Estimated Financial institution counterparties: Oil - assets Barrels 5,601 $ 37,667 4,024 $ 27,082 Oil - liabilities Barrels 4,581 (18,500) 6,068 (53,579) Natural gas - assets MMBTUs 17,363 11,822 16,539 6,220 Natural gas - liabilities MMBTUs 6,462 (2,499) 15,682 (19,138) Customer counterparties: Oil - assets Barrels 4,618 $ 18,722 6,068 $ 54,219 Oil - liabilities Barrels 5,564 (36,877) 4,024 (26,551) Natural gas - assets MMBTUs 6,462 2,499 15,682 19,164 Natural gas - liabilities MMBTUs 17,363 (11,571) 16,539 (6,124) 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 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 contracts were as follows: December 31, 2023 December 31, 2022 Notional Notional Estimated Notional Estimated Financial institution counterparties: Forward/option contracts - assets EUR — $ — 875 $ 1 Forward/option contracts - assets CAD 250 1 — — Forward/option contracts - liabilities EUR 3,000 (14) 875 (10) Forward contracts - liabilities CAD 250 (5) — — Customer counterparties: Forward/option contracts - assets EUR 3,000 16 875 10 Forward/option contracts - assets CAD 250 5 — — Forward contracts - liabilities EUR — — 875 (1) Forward 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: 2023 2022 2021 Commercial loan/lease interest rate swaps: Amount of gain (loss) included in interest income on loans $ 16 $ (7) $ (91) Amount of (gain) loss included in other non-interest expense — 6 10 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-hedging interest rate, commodity, foreign currency and other derivative instruments are presented in the table below. 2023 2022 2021 Non-hedging interest rate derivatives: Other non-interest income $ 6,982 $ 1,742 $ 4,285 Other non-interest expense — — (1) Non-hedging commodity derivatives: Other non-interest income 1,889 2,297 4,052 Non-hedging foreign currency derivatives: Other non-interest income 30 63 39 Counterparty Credit Risk. Derivative contracts involve the risk of dealing with both bank customers and institutional derivative counterparties and their ability to meet contractual terms. Institutional counterparties must have an investment grade credit rating and be approved by our Asset/Liability Management Committee. Our credit exposure on derivative contracts is limited to the net favorable value of all contracts by each counterparty. Credit exposure may be reduced by the amount of collateral pledged by the counterparty. There are no credit-risk-related contingent features associated with any of our derivative contracts. Certain derivative contracts with upstream financial institution counterparties may be terminated with respect to a party in the transaction, if such party does not have at least a minimum level rating assigned to either its senior unsecured long-term debt or its deposit obligations by certain third-party rating agencies.

Balance Sheet Offsetting

Balance Sheet Offsetting	12 Months Ended
	Dec. 31, 2023
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 December 31, 2023 is presented in the following tables. Gross Amount Gross Amount Net Amount December 31, 2023 Financial assets: Derivatives: Loan/lease interest rate swaps and caps $ 70,233 $ — $ 70,233 Commodity swaps and options 49,489 — 49,489 Foreign currency forward/option contracts 1 — 1 Total derivatives 119,723 — 119,723 Resell agreements 84,650 — 84,650 Total $ 204,373 $ — $ 204,373 Financial liabilities: Derivatives: Loan/lease interest rate swaps $ 20,293 $ — $ 20,293 Commodity swaps and options 20,999 — 20,999 Foreign currency forward/option 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 Information about financial instruments that are eligible for offset in the consolidated balance sheet as of December 31, 2022 is presented in the following tables. Gross Amount Gross Amount Net Amount December 31, 2022 Financial assets: Derivatives: Loan/lease interest rate swaps and caps $ 85,691 $ — $ 85,691 Commodity swaps and options 33,302 — 33,302 Foreign currency forward/option contracts 1 — 1 Total derivatives 118,994 — 118,994 Resell agreements 87,150 — 87,150 Total $ 206,144 $ — $ 206,144 Financial liabilities: Derivatives: Loan/lease interest rate swaps $ 1,102 $ — $ 1,102 Commodity swaps and options 72,717 — 72,717 Foreign currency forward contracts 10 — 10 Total derivatives 73,829 — 73,829 Repurchase agreements 4,660,641 — 4,660,641 Total $ 4,734,470 $ — $ 4,734,470 Gross Amounts Not Offset Net Amount Financial Collateral Net December 31, 2022 Financial assets: Derivatives: Counterparty H $ 27,031 $ (20,564) $ (6,467) $ — Counterparty F 17,297 (17,297) — — Counterparty B 39,370 (24,500) (14,870) — Counterparty E 14,430 (47) (14,131) 252 Other counterparties 20,866 (120) (20,500) 246 Total derivatives 118,994 (62,528) (55,968) 498 Resell agreements 87,150 — (87,150) — Total $ 206,144 $ (62,528) $ (143,118) $ 498 Financial liabilities: Derivatives: Counterparty H $ 20,564 $ (20,564) $ — $ — Counterparty F 27,747 (17,297) (8,479) 1,971 Counterparty B 24,500 (24,500) — — Counterparty E 47 (47) — — Other counterparties 971 (120) (851) — Total derivatives 73,829 (62,528) (9,330) 1,971 Repurchase agreements 4,660,641 — (4,660,641) — Total $ 4,734,470 $ (62,528) $ (4,669,971) $ 1,971 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 December 31, 2023 and December 31, 2022 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 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 $ — December 31, 2022 Repurchase agreements: U.S. Treasury $ 3,735,061 $ — $ — $ — $ 3,735,061 Residential mortgage-backed securities 925,580 — — — 925,580 Total borrowings $ 4,660,641 $ — $ — $ — $ 4,660,641 Gross amount of recognized liabilities for repurchase agreements $ 4,660,641 Amounts related to agreements not included in offsetting disclosures above $ —

Fair Value Measurements

Fair Value Measurements	12 Months Ended
	Dec. 31, 2023
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 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. The fair value hierarchy is as follows: • Level 1 Inputs - Unadjusted quoted prices in active markets for identical assets or liabilities that the reporting entity has the ability to access at the measurement date. • Level 2 Inputs - Inputs other than quoted prices included in Level 1 that are observable for the asset or liability, either directly or indirectly. These might include quoted prices for similar assets or liabilities in active markets, quoted prices for identical or similar assets or liabilities in markets that are not active, inputs other than quoted prices that are observable for the asset or liability (such as interest rates, volatilities, prepayment speeds, credit risks, etc.) or inputs that are derived principally from or corroborated by market data by correlation or other means. • Level 3 Inputs - Unobservable inputs for determining the fair values of assets or liabilities that reflect an entity’s own assumptions about the assumptions that market participants would use in pricing the assets or liabilities. In general, fair value is based upon quoted market prices, where available. If such quoted market prices are not available, fair value is based upon internally developed models that primarily use, as inputs, observable market-based parameters. Valuation adjustments may be made to ensure that financial instruments are recorded at fair value. These adjustments may include amounts to reflect counterparty credit quality and our creditworthiness, among other things, as well as unobservable parameters. Any such valuation adjustments are applied consistently over time. Our valuation methodologies may produce a fair value calculation that may not be indicative of net realizable value or reflective of future fair values. While management believes our valuation methodologies are appropriate and consistent with other market participants, the use of different methodologies or assumptions to determine the fair value of certain financial instruments could result in a different estimate of fair value at the reporting date. Furthermore, the reported fair value amounts have not been comprehensively revalued since the presentation dates, and therefore, estimates of fair value after the balance sheet date may differ significantly from the amounts presented herein. A more detailed description of the valuation methodologies used for assets and liabilities measured at fair value is set forth below. Transfers between levels of the fair value hierarchy are recognized on the actual date of the event or circumstances that caused the transfer, which generally coincides with our monthly and/or quarterly valuation process. Financial Assets and Financial Liabilities: Financial assets and financial liabilities measured at fair value on a recurring basis include the following: Securities Available for Sale . U.S. Treasury securities are reported at fair value utilizing Level 1 inputs. Other securities classified as available for sale are reported at fair value utilizing Level 2 inputs. For these securities, we obtain fair value measurements from an independent pricing service. The fair value measurements consider observable data that may include dealer quotes, market spreads, cash flows, the U.S. Treasury yield curve, live trading levels, trade execution data, market consensus prepayment speeds, credit information and the bond’s terms and conditions, among other things. We review the prices supplied by the independent pricing service, as well as their underlying pricing methodologies, for reasonableness and to ensure such prices are aligned with traditional pricing matrices. In general, we do not purchase investment portfolio securities that are esoteric or that have a complicated structure. Our entire portfolio consists of traditional investments, nearly all of which are U.S. Treasury obligations, federal agency bullet or mortgage pass-through securities, or general obligation or revenue based municipal bonds. Pricing for such instruments is fairly generic and is easily obtained. From time to time, we will validate prices supplied by the independent pricing service by comparison to prices obtained from third-party sources or derived using internal models. Trading Securities . U.S. Treasury securities and exchange-listed common stock are reported at fair value utilizing Level 1 inputs. Other securities classified as trading are reported at fair value utilizing Level 2 inputs in the same manner as described above for securities available for sale. Derivatives . Derivatives are generally reported at fair value utilizing Level 2 inputs, except for foreign currency contracts, which are reported at fair value utilizing Level 1 inputs. We obtain dealer quotations and utilize internally developed valuation models to value commodity swaps/options. We utilize internally developed valuation models and/or third-party models with observable market data inputs to validate the valuations provided by the dealers. Though there has never been a significant discrepancy in the valuations, should such a significant discrepancy arise, we would obtain price verification from a third-party dealer. We utilize internal valuation methods with observable market data inputs to estimate fair values of customer interest rate swaps, caps and floors. We also obtain dealer quotations for these derivatives for comparative purposes to assess the reasonableness of the model valuations. In cases where significant credit valuation adjustments are incorporated into the estimation of fair value, reported amounts are considered to have been derived utilizing Level 3 inputs. For purposes of potential valuation adjustments to our derivative positions, we evaluate the credit risk of our counterparties as well as ours. Accordingly, we have considered factors such as the likelihood of our default and the default of our counterparties, our net exposures and remaining contractual life, among other things, in determining if any fair value adjustments related to credit risk are required. Counterparty exposure is evaluated by netting positions that are subject to master netting arrangements, as well as considering the amount of collateral securing the position. We review our counterparty exposure on a regular basis, and, when necessary, appropriate business actions are taken to adjust the exposure. We also utilize this approach to estimate our own credit risk on derivative liability positions. To date, we have not realized any significant losses due to a counterparty’s inability to pay any net uncollateralized position. The change in value of derivative assets and derivative liabilities attributable to credit risk was not significant during the reported periods. The following tables summarize financial assets and financial liabilities measured at fair value on a recurring basis as of December 31, 2023 and 2022, segregated by the level of the valuation inputs within the fair value hierarchy utilized to measure fair value: Level 1 Level 2 Level 3 Total 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/option 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/option contracts 19 — — 19 Level 1 Level 2 Level 3 Total 2022 Securities available for sale: U.S. Treasury $ 5,051,587 $ — $ — $ 5,051,587 Residential mortgage-backed securities — 6,376,236 — 6,376,236 States and political subdivisions — 6,773,355 — 6,773,355 Other — 42,427 — 42,427 Trading account securities: U.S. Treasury 25,879 — — 25,879 States and political subdivisions — 2,166 — 2,166 Derivative assets: Interest rate swaps, caps and floors — 86,793 — 86,793 Commodity swaps and options — 106,685 — 106,685 Foreign currency forward contracts 11 — — 11 Derivative liabilities: Interest rate swaps, caps and floors — 95,533 — 95,533 Commodity swaps and options — 105,392 — 105,392 Foreign currency forward contracts 11 — — 11 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 (for example, when there is evidence of impairment). Financial assets measured at fair value on a non-recurring basis during the reported periods include certain impaired loans reported at the fair value of the underlying collateral if repayment is expected solely from the collateral. Collateral values are estimated using Level 2 inputs based on observable market data, typically in the case of real estate collateral, or Level 3 inputs based on customized discounting criteria, typically in the case of non-real estate collateral such as inventory, oil and gas reserves, accounts receivable, equipment or other business assets. 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: 2023 2022 2021 Level 2 Carrying value before allocations $ 19,719 $ 6,237 $ 1,333 Specific (allocations) reversals of prior allocations (3,391) (1,480) 214 Fair value $ 16,328 $ 4,757 $ 1,547 Level 3 Carrying value before allocations $ 15,465 $ 8,156 $ 16,074 Specific (allocations) reversals of prior allocations (2,344) 625 (5,178) Fair value $ 13,121 $ 8,781 $ 10,896 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. Such fair value measurements were not significant during the reported periods. Charge-offs recognized upon loan foreclosures are generally offset by general or specific allocations of the allowance for credit losses on loans and generally do not, and did not during the reported periods, significantly impact our credit loss expense. Regulatory guidelines require us to reevaluate the fair value of other real estate owned on at least an annual basis. While our policy is to comply with the regulatory guidelines, our general practice is to reevaluate the fair value of collateral supporting impaired collateral dependent loans on a quarterly basis. Thus, appraisals are generally not considered to be outdated, and we typically do not make any adjustments to the appraised values. ASC Topic 825, “Financial Instruments,” requires disclosure of the fair value of financial assets and financial liabilities, including those financial assets and financial liabilities that are not measured and reported at fair value on a recurring basis or non-recurring basis. The estimated fair value approximates carrying value for cash and cash equivalents, accrued interest and the cash surrender value of life insurance policies. The methodologies for other financial assets and financial liabilities that are not measured and reported at fair value on a recurring basis or non-recurring basis are discussed below: Loans . The estimated fair value approximates carrying value for variable-rate loans that reprice frequently and with no significant change in credit risk. The fair value of fixed-rate loans and variable-rate loans which reprice on an infrequent basis is estimated by discounting future cash flows using the current interest rates at which similar loans with similar terms would be made to borrowers of similar credit quality. An overall valuation adjustment is made for specific credit risks as well as general portfolio credit risk. Deposits . The estimated fair value approximates carrying value for demand deposits. The fair value of fixed-rate deposit liabilities with defined maturities is estimated by discounting future cash flows using the interest rates currently offered for deposits of similar remaining maturities. The estimated fair value of deposits does not take into account the value of our long-term relationships with depositors, commonly known as core deposit intangibles, which are separate intangible assets, and not considered financial instruments. Nonetheless, we would likely realize a core deposit premium if our deposit portfolio were sold in the principal market for such deposits. Borrowed Funds . The estimated fair value approximates carrying value for short-term borrowings. The fair value of long-term fixed-rate borrowings is estimated using quoted market prices, if available, or by discounting future cash flows using current interest rates for similar financial instruments. The estimated fair value approximates carrying value for variable-rate junior subordinated deferrable interest debentures that reprice quarterly. Loan Commitments, Standby and Commercial Letters of Credit . Our lending commitments have variable interest rates and “escape” clauses if the customer’s credit quality deteriorates. Therefore, the fair values of these items are not significant and are not included in the following table. The estimated fair values of financial instruments that are reported at amortized cost in our consolidated balance sheets, segregated by the level of valuation inputs within the fair value hierarchy utilized to measure fair value, were as follows: December 31, 2023 December 31, 2022 Carrying Estimated Carrying Estimated Financial assets: Level 2 inputs: Cash and cash equivalents $ 8,687,276 $ 8,687,276 $ 12,028,132 $ 12,028,132 Securities held to maturity 3,619,428 3,532,044 2,639,083 2,467,865 Accrued interest receivable 251,385 251,385 243,682 243,682 Level 3 inputs: Loans, net 18,578,255 18,117,369 16,927,348 16,343,417 Financial liabilities: Level 2 inputs: Deposits 41,920,568 41,903,580 43,954,196 43,920,741 Federal funds purchased 14,200 14,200 51,650 51,650 Repurchase agreements 4,127,188 4,127,188 4,660,641 4,660,641 Junior subordinated deferrable interest debentures 123,127 123,712 123,069 123,712 Subordinated notes 99,491 96,071 99,335 97,014 Accrued interest payable 61,222 61,222 18,444 18,444 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.

Operating Segments

Operating Segments	12 Months Ended
	Dec. 31, 2023
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. The regions are primarily based upon geographic location and include Austin, Corpus Christi, Dallas, Fort Worth, Houston, Permian Basin, Rio Grande Valley, San Antonio and Statewide. We are primarily managed based on the line of business structure. In that regard, all regions have the same lines of business, which have the same product and service offerings, have similar types and classes of customers and utilize similar service delivery methods. Pricing guidelines for products and services are the same across all regions. The regional reporting structure is primarily a means to scale the lines of business to provide a local, community focus for customer relations and business development. Banking and Frost Wealth Advisors are delineated by the products and services that each segment offers. The Banking operating segment includes both commercial and consumer banking services and Frost Insurance Agency. Commercial banking services are provided to corporations and other business clients and include a wide array of lending and cash management products. Consumer banking services include direct lending and depository services. Frost Insurance Agency provides insurance brokerage services to individuals and businesses covering corporate and personal property and casualty products, as well as group health and life insurance products. The Frost Wealth Advisors operating segment includes fee-based services within private trust, retirement services, and financial management services, including personal wealth management and securities brokerage services. A third operating segment, Non-Banks, is for the most part the parent holding company, as well as certain other insignificant non-bank subsidiaries of the parent that, for the most part, have little or no activity. The parent company’s principal activities include the direct and indirect ownership of our banking and non-banking subsidiaries and the issuance of debt and equity. Our principal source of revenue is dividends from our subsidiaries. The accounting policies of each reportable segment are the same as those of our consolidated entity except for the following items, which impact the Banking and Frost Wealth Advisors segments: (i) expenses for consolidated back-office operations and general overhead-type expenses such as executive administration, accounting and internal audit are allocated to operating segments based on estimated uses of those services, (ii) income tax expense for the individual segments is calculated essentially at the statutory rate, and (iii) the parent company records the tax expense or benefit necessary to reconcile to the consolidated total. We use a match-funded transfer pricing process to assess operating segment performance. The process helps us to (i) identify the cost or opportunity value of funds within each business segment, (ii) measure the profitability of a particular business segment by relating appropriate costs to revenues, (iii) evaluate each business segment in a manner consistent with its economic impact on consolidated earnings, and (iv) enhance asset and liability pricing decisions. Financial results by operating segment are detailed below. Certain prior period amounts have been reclassified to conform to the current presentation. Frost Wealth Advisors excludes off-balance-sheet managed and custody assets with a total fair value of $47.2 billion, $42.9 billion and $43.3 billion at December 31, 2023, 2022 and 2021. Banking Frost Non-Banks Consolidated 2023 Net interest income (expense) $ 1,562,441 $ 7,620 $ (11,397) $ 1,558,664 Credit loss expense 46,171 — — 46,171 Non-interest income 251,319 178,906 (1,683) 428,542 Non-interest expense 1,077,824 144,478 6,360 1,228,662 Income (loss) before income taxes 689,765 42,048 (19,440) 712,373 Income tax expense (benefit) 111,145 8,830 (5,575) 114,400 Net income (loss) 578,620 33,218 (13,865) 597,973 Preferred stock dividends — — 6,675 6,675 Net income (loss) available to common shareholders $ 578,620 $ 33,218 $ (20,540) $ 591,298 Revenues from (expenses to) external customers $ 1,813,760 $ 186,526 $ (13,080) $ 1,987,206 Average assets (in millions) $ 49,536 $ 59 $ 9 $ 49,604 Banking Frost Non-Banks Consolidated 2022 Net interest income (expense) $ 1,295,467 $ 4,645 $ (8,829) $ 1,291,283 Credit loss expense 3,000 — — 3,000 Non-interest income 230,876 175,874 (1,932) 404,818 Non-interest expense 886,421 132,009 5,844 1,024,274 Income (loss) before income taxes 636,922 48,510 (16,605) 668,827 Income tax expense (benefit) 85,127 10,187 (5,637) 89,677 Net income (loss) 551,795 38,323 (10,968) 579,150 Preferred stock dividends — — 6,675 6,675 Net income (loss) available to common shareholders $ 551,795 $ 38,323 $ (17,643) $ 572,475 Revenues from (expenses to) external customers $ 1,526,343 $ 180,519 $ (10,761) $ 1,696,101 Average assets (in millions) $ 51,448 $ 57 $ 8 $ 51,513 2021 Net interest income (expense) $ 989,870 $ 2,138 $ (7,141) $ 984,867 Credit loss expense 54 9 — 63 Non-interest income 220,662 167,442 (1,376) 386,728 Non-interest expense 753,719 122,972 5,303 881,994 Income (loss) before income taxes 456,759 46,599 (13,820) 489,538 Income tax expense (benefit) 41,483 9,786 (4,810) 46,459 Net income (loss) 415,276 36,813 (9,010) 443,079 Preferred stock dividends — — 7,157 7,157 Net income (loss) available to common shareholders $ 415,276 $ 36,813 $ (16,167) $ 435,922 Revenues from (expenses to) external customers $ 1,210,532 $ 169,580 $ (8,517) $ 1,371,595 Average assets (in millions) $ 45,903 $ 70 $ 10 $ 45,983

Condensed Financial Statements

Condensed Financial Statements of Parent Company	12 Months Ended
	Dec. 31, 2023
Condensed Financial Information Disclosure [Abstract]
Condensed Financial Statements of Parent Company	Condensed Financial Statements of Parent Company Condensed financial statements pertaining only to Cullen/Frost Bankers, Inc. are presented below. Investments in subsidiaries are stated using the equity method of accounting. Condensed Balance Sheets December 31, 2023 2022 Assets: Cash $ 350,525 $ 311,944 Total cash and cash equivalents 350,525 311,944 Investment in subsidiaries 3,625,951 3,065,114 Accrued interest receivable and other assets 1,233 1,142 Total assets $ 3,977,709 $ 3,378,200 Liabilities: Junior subordinated deferrable interest debentures, net of unamortized issuance costs $ 123,127 $ 123,069 Subordinated notes, net of unamortized issuance costs 99,491 99,335 Accrued interest payable and other liabilities 38,644 18,568 Total liabilities 261,262 240,972 Shareholders’ Equity 3,716,447 3,137,228 Total liabilities and shareholders’ equity $ 3,977,709 $ 3,378,200 Condensed Statements of Income Year Ended December 31, 2023 2022 2021 Income: Dividend income paid by Frost Bank $ 279,679 $ 51,711 $ 219,386 Dividend income paid by non-banks 255 109 473 Interest and other income 1,929 — 101 Total income 281,863 51,820 219,960 Expenses: Interest expense 13,304 8,829 7,141 Salaries and employee benefits 1,668 1,605 1,499 Other 6,653 6,316 5,867 Total expenses 21,625 16,750 14,507 Income before income taxes and equity in undistributed earnings of subsidiaries 260,238 35,070 205,453 Income tax benefit 5,974 5,641 4,899 Equity in undistributed earnings of subsidiaries 331,761 538,439 232,727 Net income 597,973 579,150 443,079 Preferred stock dividends 6,675 6,675 7,157 Net income available to common shareholders $ 591,298 $ 572,475 $ 435,922 Condensed Statements of Cash Flows Year Ended December 31, 2023 2022 2021 Operating Activities: Net income $ 597,973 $ 579,150 $ 443,079 Adjustments to reconcile net income to net cash provided by operating activities: Equity in undistributed earnings of subsidiaries (331,761) (538,439) (232,727) Stock-based compensation 880 720 700 Net tax benefit from stock-based compensation 331 472 278 Net change in other assets and other liabilities 19,867 (15,249) 23,890 Net cash from operating activities 287,290 26,654 235,220 Investing Activities: Redemption of investment in non-bank subsidiary — — 406 Net cash from investing activities — — 406 Financing Activities: Principal payments on long-term borrowings — — (13,403) Proceeds from stock option exercises 9,299 16,659 54,417 Proceeds from stock-based compensation activities of subsidiaries 23,710 17,602 12,053 Purchase of treasury stock (42,720) (4,391) (3,864) Treasury stock issued to 401(k) stock purchase plan — — 1,749 Cash dividends paid on preferred stock (6,675) (6,675) (7,157) Cash dividends paid on common stock (232,323) (209,780) (188,786) Net cash from financing activities (248,709) (186,585) (144,991) Net change in cash and cash equivalents 38,581 (159,931) 90,635 Cash and cash equivalents at beginning of year 311,944 471,875 381,240 Cash and cash equivalents at end of year $ 350,525 $ 311,944 $ 471,875

Accounting Standards Updates

Accounting Standards Updates	12 Months Ended
	Dec. 31, 2023
Accounting Standards Update and Change in Accounting Principle [Abstract]
Accounting Standards Updates	Accounting Standards Updates ASU 2019-12, “Income Taxes (Topic 740) - Simplifying the Accounting for Income Taxes.” The guidance issued in this update simplifies the accounting for income taxes by eliminating certain exceptions to the guidance in ASC 740 related to the approach for intraperiod tax allocation, the methodology for calculating income taxes in an interim period and the recognition for deferred tax liabilities for outside basis differences. ASU 2019-12 also simplifies aspects of the accounting for franchise taxes and enacted changes in tax laws or rates and clarifies the accounting for transactions that result in a step-up in the tax basis of goodwill. ASU 2019-12 became effective for us on January 1, 2021 and did not have a significant impact on our financial statements. ASU 2020-08, “Codification Improvements to Subtopic 310-20, Receivables - Nonrefundable Fees and Other Costs.” ASU 2020-08 clarifies the accounting for the amortization of purchase premiums for callable debt securities with multiple call dates. ASU 2020-8 became effective for us on January 1, 2021 and did not have a significant impact on our financial statements. ASU 2020-09, “Debt (Topic 470): Amendments to SEC Paragraphs Pursuant to SEC Release No. 33-10762.” ASU 2020-9 amends the ASC to reflect the issuance of an SEC rule related to financial disclosure requirements for subsidiary issuers and guarantors of registered debt securities and affiliates whose securities are pledged as collateral for registered securities. ASU 2020-09 became effective for us on January 4, 2021, concurrent with the effective date of the SEC release, and did not have a significant impact on our financial statements. ASU 2022-01, “Derivatives and Hedging (Topic 815): Fair Value Hedging - Portfolio Layer Method.” Under prior guidance, entities can apply the last-of-layer hedging method to hedge the exposure of a closed portfolio of prepayable financial assets to fair value changes due to changes in interest rates for a portion of the portfolio that is not expected to be affected by prepayments, defaults, and other events affecting the timing and amount of cash flows. ASU 2022-01 expands the last-of-layer method, which permits only one hedge layer, to allow multiple hedged layers of a single closed portfolio. To reflect that expansion, the last-of-layer method is renamed the portfolio layer method. ASU 2022-01 also (i) expands the scope of the portfolio layer method to include non-prepayable financial assets, (ii) specifies eligible hedging instruments in a single-layer hedge, (iii) provides additional guidance on the accounting for and disclosure of hedge basis adjustments under the portfolio layer method and (iv) specifies how hedge basis adjustments should be considered when determining credit losses for the assets included in the closed portfolio. ASU 2022-01 became effective for us on January 1, 2023. The adoption of ASU 2022-01 did not have a significant impact on our financial statements. ASU 2022-02, “Financial Instruments - Credit Losses (Topic 326): Troubled Debt Restructurings and Vintage Disclosures.” ASU 2022-02 eliminates the accounting guidance for troubled debt restructurings in Accounting Standards Codification (“ASC”) Subtopic 310-40, Receivables - Troubled Debt Restructurings by Creditors, while enhancing disclosure requirements for certain loan refinancings and restructurings by creditors when a borrower is experiencing financial difficulty. Additionally, ASU 2022-02 requires entities to disclose current-period gross write-offs by year of origination for financing receivables and net investments in leases within the scope of ASC Subtopic 3126-20, Financial Instruments - Credit Losses - Measured at Amortized Cost. ASU 2022-02 became effective for us on January 1, 2023. The adoption of ASU 2022-02 did not have a significant impact on our financial statements. ASU 2022-03, “Fair Value Measurement (Topic 820): Fair Value Measurement of Equity Securities Subject to Contractual Sale Restrictions.” ASU 2022-03 clarifies that a contractual restriction on the sale of an equity security is not considered part of the unit of account of the equity security and, therefore, is not considered in measuring fair value. ASU 2022-03 also clarifies that an entity cannot, as a separate unit of account, recognize and measure a contractual sale restriction and requires certain new disclosures for equity securities subject to contractual sale restrictions. ASU 2022-03 will be effective for us on January 1, 2024. The adoption of ASU 2022-03 is not expected to have a significant impact on our financial statements. ASU 2023-01, “Leases (Topic 842): Common Control Arrangements.” ASU 2023-01 requires entities to amortize leasehold improvements associated with common control leases over the useful life to the common control group. ASU 2023-01 also provides certain practical expedients applicable to private companies and not-for-profit organizations. ASU 2023-01 will be effective for us on January 1, 2024 and its adoption is not expected to 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 will be effective for us on January 1, 2024 and its adoption is not expected to have a significant effect on our financial statements. ASU No. 2023-03, “Presentation of Financial Statements (Topic 205), Income Statement - Reporting Comprehensive Income (Topic 220), Distinguishing Liabilities from Equity (Topic 480), Equity (Topic 505), and Compensation - Stock Compensation (Topic 718): Amendments to SEC Paragraphs Pursuant to SEC Staff Accounting Bulletin No. 120, SEC Staff Announcement at the March 24, 2022 EITF Meeting, and Staff Accounting Bulletin Topic 6.B, Accounting Series Release 280 - General Revision of Regulation S-X: Income or Loss Applicable to Common Stock.” ASU 2023-03 amends the ASC for SEC updates pursuant to SEC Staff Accounting Bulletin No. 120; SEC Staff Announcement at the March 24, 2022 Emerging Issues Task Force (“EITF”) Meeting; and Staff Accounting Bulletin Topic 6.B, Accounting Series Release 280 - General Revision of Regulation S-X: Income or Loss Applicable to Common Stock. These updates were immediately effective and did not have a significant impact on our financial statements. ASU 2023-06, “Disclosure Improvements - Codification Amendments in Response to the SEC’s Disclosure Update and Simplification Initiative.” ASU 2023-06 amends the ASC to incorporate certain disclosure requirements from SEC Release No. 33-10532 - Disclosure Update and Simplification that was issued in 2018. The effective date for each amendment will be the date on which the SEC’s removal of that related disclosure from Regulation S-X or Regulation S-K becomes effective, with early adoption prohibited. ASU 2023-06 is not expected to have a significant impact on our financial statements. ASU No. 2023-07, “Segment Reporting (Topic 280): Improvements to Reportable Segment Disclosures.” ASU 2023-07 expands segment disclosure requirements for public entities to require disclosure of significant segment expenses and other segment items on an annual and interim basis and to provide in interim periods all disclosures about a reportable segment’s profit or loss and assets that are currently required annually. ASU 2023-07 is effective for fiscal years beginning after December 15, 2023, and interim periods within fiscal years beginning after December 15, 2024. Early adoption is permitted. ASU 2023-07 is not expected to have a significant impact on our financial statements. ASU No. 2023-09, “Income Taxes (Topic 740): Improvements to Income Tax Disclosures.”

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2023
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 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. We determine whether we have a controlling financial interest in an entity by first evaluating whether the entity is a voting interest entity or a variable interest entity (“VIE”) under accounting principles generally accepted in the United States. Voting interest entities are entities in which the total equity investment at risk is sufficient to enable the entity to finance itself independently and provides the equity holders with the obligation to absorb losses, the right to receive residual returns and the right to make decisions about the entity’s activities. We consolidate voting interest entities in which we have all, or at least a majority of, the voting interest. As defined in applicable accounting standards, VIEs are entities that lack one or more of the characteristics of a voting interest entity. A controlling financial interest in a VIE is present when an enterprise has both the power to direct the activities of the VIE that most significantly impact the VIE’s economic performance and an obligation to absorb losses or the right to receive benefits that could potentially be significant to the VIE. The enterprise with a controlling financial interest, known as the primary beneficiary, consolidates the VIE. Our wholly-owned subsidiary, Cullen/Frost Capital Trust II, is a VIE for which we are not the primary beneficiary and, as such, its accounts are not included in our consolidated financial statements. Acquisitions are accounted for using the purchase method with the operating results of the acquired companies included with our results of operations since their respective dates of acquisition.
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 credit losses on loans and off-balance-sheet credit exposures, the fair values of financial instruments and the status of contingencies are particularly subject to change.
Concentrations and Restrictions on Cash and Cash Equivalents	Concentrations and Restrictions on Cash and Cash Equivalents . We maintain deposits with other financial institutions in amounts that exceed federal deposit insurance coverage. Furthermore, federal funds sold are essentially uncollateralized loans to other financial institutions. Management regularly evaluates the credit risk associated with the counterparties to these transactions and believes that we are not exposed to any significant credit risks on cash and cash equivalents. As of December 31, 2023 and 2022, we had $8.6 million and $3.2 million in cash collateral on deposit with other financial institution counterparties to interest rate swap transactions.
Cash Flow Reporting	Cash Flow Reporting . Cash and cash equivalents include cash, deposits with other financial institutions that have an initial maturity of less than 90 days when acquired by us, federal funds sold and resell agreements. Net cash flows are reported for loans, deposit transactions and short-term borrowings. Additional cash flow information was as follows: Year Ended December 31, 2023 2022 2021 Cash paid for interest $ 616,274 $ 169,020 $ 29,003 Cash paid for income tax 118,000 100,000 39,852 Significant non-cash transactions: Exchange of real estate — — 11,036 Unsettled securities transactions 1,452 94,884 27,032 Loans foreclosed and transferred to other real estate owned and foreclosed assets — 239 3,464 Right-of-use lease assets obtained in exchange for lessee operating lease liabilities 15,259 31,787 12,854 Treasury stock issued to 401(k) stock purchase plan — — 1,749
Repurchase/Resell Agreements	Repurchase/Resell Agreements. We purchase certain securities under agreements to resell. The amounts advanced under these agreements represent short-term loans and are reflected as assets in the accompanying consolidated balance sheets. The securities underlying these agreements are book-entry securities. We also sell certain securities under agreements to repurchase. The agreements are treated as collateralized financing transactions and the obligations to repurchase securities sold are reflected as a liability in the accompanying consolidated balance sheets. The dollar amount of the securities underlying the agreements remains in the asset accounts.
Securities	Securities. Securities are classified as held to maturity and carried at amortized cost when management has the positive intent and ability to hold them until maturity. Securities to be held for indefinite periods of time are classified as available for sale and carried at fair value, with the unrealized holding gains and losses (those for which no allowance for credit losses are recorded) reported as a component of other comprehensive income, net of tax. Securities held for resale in anticipation of short-term market movements are classified as trading and are carried at fair value, with changes in unrealized holding gains and losses included in income. Management determines the appropriate classification of securities at the time of purchase. Securities with limited marketability, such as stock in the Federal Reserve Bank and the Federal Home Loan Bank, are carried at cost. Interest income on securities includes amortization of purchase premiums and discounts. Premiums and discounts on securities are generally amortized using the interest method with a constant effective yield without anticipating prepayments, except for mortgage-backed securities where prepayments are anticipated. Premiums on callable securities are amortized to their earliest call date. A security is placed on non-accrual status if (i) principal or interest has been in default for a period of 90 days or more or (ii) full payment of principal and interest is not expected. Interest accrued but not received for a security placed on non-accrual status is reversed against interest income. Gains and losses on sales are recorded on the trade date and are derived from the amortized cost of the security sold.
Loans	Loans . Loans are reported at the principal balance outstanding net of unearned discounts. Interest income on loans is reported on the level-yield method and includes amortization of deferred loan fees and costs over the terms of the individual loans to which they relate, or, in certain cases, over the average expected term for loans where deferred fees and costs are accounted for on a pooled basis. Net loan commitment fees or costs for commitment periods greater than one year are deferred and amortized into fee income or other expense on a straight-line basis over the commitment period. Income on direct financing leases is recognized on a basis that achieves a constant periodic rate of return on the outstanding investment. Further information regarding our accounting policies related to past due loans, non-accrual loans, impaired loans and troubled-debt restructurings is presented in Note 3 - Loans.
Credit Loss, Financial Instrument	Allowance For Credit Losses - Held-to-Maturity Securities. The allowance for credit losses on held-to-maturity securities is a contra-asset valuation account, calculated in accordance with Accounting Standards Codification (“ASC”) Topic 326 (“ASC 326”), that is deducted from the amortized cost basis of held-to-maturity securities to present management's best estimate of the net amount expected to be collected. Held-to-maturity securities are charged-off against the allowance when deemed uncollectible by management. Adjustments to the allowance are reported in our income statement as a component of credit loss expense. Management measures expected credit losses on held-to-maturity securities on a collective basis by major security type with each type sharing similar risk characteristics and considers historical credit loss information that is adjusted for current conditions and reasonable and supportable forecasts. Management has made the accounting policy election to exclude accrued interest receivable on held-to-maturity securities from the estimate of credit losses. Further information regarding our policies and methodology used to estimate the allowance for credit losses on held-to-maturity securities is presented in Note 2 - Securities. Allowance For Credit Losses - Available-for-Sale Securities. For available-for-sale securities in an unrealized loss position, we first assess whether (i) we intend to sell or (ii) it is more likely than not that we will be required to sell the security before recovery of its amortized cost basis. If either case is affirmative, any previously recognized allowances are charged-off and the security's amortized cost is written down to fair value through income. If neither case is affirmative, the security is evaluated to determine whether the decline in fair value has resulted from credit losses or other factors. In making this assessment, management considers the extent to which fair value is less than amortized cost, any changes to the rating of the security by a rating agency and any adverse conditions specifically related to the security, among other factors. If this assessment indicates that a credit loss exists, the present value of cash flows expected to be collected from the security are compared to the amortized cost basis of the security. If the present value of cash flows expected to be collected is less than the amortized cost basis, a credit loss exists and an allowance for credit losses is recorded for the credit loss, limited by the amount that the fair value is less than the amortized cost basis. Any impairment that has not been recorded through an allowance for credit losses is recognized in other comprehensive income. Adjustments to the allowance are reported in our income statement as a component of credit loss expense. Management has made the accounting policy election to exclude accrued interest receivable on available-for-sale securities from the estimate of credit losses. Available-for-sale securities are charged-off against the allowance or, in the absence of any allowance, written down through income when deemed uncollectible by management or when either of the aforementioned criteria regarding intent or requirement to sell is met.
Allowance for Credit Losses Loans	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 management's best estimate of the net amount expected to be collected. Loans are charged-off against the allowance when deemed uncollectible by management. Expected recoveries do not exceed the aggregate of amounts previously charged-off and expected to be charged-off. Adjustments to the allowance are reported in our income statement as a component of credit loss expense. Management has made the accounting policy election to exclude accrued interest receivable on loans from the estimate of credit losses. Further information regarding our policies and methodology used to estimate the allowance for credit losses on loans is presented in Note 3 - Loans. 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. The contractual term excludes expected extensions, renewals and modifications unless (i) management has a reasonable expectation that a loan to an individual borrower that is experiencing financial difficulty will be modified or (ii) such extension or renewal options are not unconditionally cancellable by us and, in such cases, the borrower is likely to meet applicable conditions and likely to request extension or renewal. Relevant available information includes historical credit loss experience, current conditions and reasonable and supportable forecasts. While historical credit loss experience provides the basis for the estimation of expected credit losses, adjustments to historical loss information may be made for differences in current portfolio-specific risk characteristics, environmental conditions or other relevant factors. The allowance for credit losses is measured on a collective basis for portfolios of loans when similar risk characteristics exist. Loans that do not share risk characteristics are evaluated for expected credit losses on an individual basis and excluded from the collective evaluation. Expected credit losses for collateral dependent loans, including loans where the borrower is experiencing financial difficulty but foreclosure is not probable, are based on the fair value of the collateral at the reporting date, adjusted for selling costs as 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. In calculating the allowance for credit losses, most loans are segmented into pools based upon similar characteristics and risk profiles. Common characteristics and risk profiles include the type/purpose of loan, underlying collateral, geographical similarity and historical/expected credit loss patterns. In developing these loan pools for the purposes of modeling expected credit losses, we also analyzed the degree of correlation in how loans within each portfolio respond when subjected to varying economic conditions and scenarios as well as other portfolio stress factors. For modeling purposes, our loan pools include (i) commercial and industrial non-revolving, (ii) commercial and industrial revolving, (iii) energy, (iv) commercial real estate - owner occupied, (v) commercial real estate - non-owner occupied, (vi) commercial real estate - construction/land development, (vii) consumer real estate and (viii) consumer and other. Prior to 2023, energy loans were included within the commercial and industrial loan pools. See discussion of the 2023 model updates below. We periodically reassess each pool to ensure the loans within the pool continue to share similar characteristics and risk profiles and to determine whether further segmentation is necessary. For each loan pool, we measure expected credit losses over the life of each loan utilizing a combination of models which measure (i) probability of default (“PD”), which is the likelihood that loan will stop performing/default, (ii) probability of attrition (“PA”), which is the likelihood that a loan will pay-off prior to maturity, (iii) loss given default (“LGD”), which is the expected loss rate for loans in default and (iv) exposure at default (“EAD”), which is the estimated outstanding principal balance of the loans upon default, including the expected funding of unfunded commitments outstanding as of the measurement date. For certain commercial loan portfolios, the PD is calculated using a transition matrix to determine the likelihood of a customer’s risk grade migrating from one specified range of risk grades to a different specified range. Expected credit losses are calculated as the product of PD (adjusted for attrition), LGD and EAD. This methodology builds on default probabilities already incorporated into our risk grading process by utilizing pool-specific historical loss rates to calculate expected credit losses. These pool-specific historical loss rates may be adjusted for current macroeconomic assumptions, as further discussed below, and other factors such as differences in underwriting standards, portfolio mix, or when historical asset terms do not reflect the contractual terms of the financial assets being evaluated as of the measurement date. Each time we measure expected credit losses, we assess the relevancy of historical loss information and consider any necessary adjustments to address any differences in asset-specific characteristics. Due to their short-term nature, expected credit losses for overdrafts included in consumer and other loans are based solely upon a weighting of recent historical charge-offs over a period of three years. The measurement of expected credit losses is impacted by loan/borrower attributes and certain macroeconomic variables. Significant loan/borrower attributes utilized in our modeling processes include, among other things, (i) origination date, (ii) maturity date, (iii) payment type, (iv) collateral type and amount, (v) current risk grade, (vi) current unpaid balance and commitment utilization rate, (vii) payment status/delinquency history and (viii) expected recoveries of previously charged-off amounts. Significant macroeconomic variables utilized in our modeling processes include, among other things, (i) Gross State Product for Texas and U.S. Gross Domestic Product, (ii) selected market interest rates including U.S. Treasury rates, bank prime rate, 30-year fixed mortgage rate, BBB corporate bond rate, among others, (iii) unemployment rates, (iv) commercial and residential property prices in Texas and the U.S. as a whole, (v) West Texas Intermediate crude oil price and (vi) total stock market index. PD and PA were estimated by analyzing internally-sourced data related to historical performance of each loan pool over a complete economic cycle. PD and PA are adjusted to reflect the current impact of certain macroeconomic variables as well as their expected changes over a reasonable and supportable forecast period. We have determined that we are reasonably able to forecast the macroeconomic variables used in our modeling processes with an acceptable degree of confidence for a total of two years with the last twelve months of the forecast period encompassing a reversion process whereby the forecasted macroeconomic variables are reverted to their historical mean utilizing a rational, systematic basis. The macroeconomic variables utilized as inputs in our modeling processes were subjected to a variety of analysis procedures and were selected primarily based on statistical relevancy and correlation to our historical credit losses. By reverting these modeling inputs to their historical mean and considering loan/borrower specific attributes, our models are intended to yield a measurement of expected credit losses that reflects our average historical loss rates for periods subsequent to the twelve-month reversion period. The LGD is based on historical recovery averages for each loan pool, adjusted to reflect the current impact of certain macroeconomic variables as well as their expected changes over a two-year forecast period, with the final twelve months of the forecast period encompassing a reversion process, which management considers to be both reasonable and supportable. This same forecast/reversion period is used for all macroeconomic variables used in all of our models. EAD is estimated using a linear regression model that estimates the average percentage of the loan balance that remains at the time of a default event. Management qualitatively adjusts model results for risk factors that are not considered within our modeling processes but are nonetheless relevant in assessing the expected credit losses within our loan pools. These qualitative factor (“Q-Factor”) and other qualitative adjustments may increase or decrease management's estimate of expected credit losses by a calculated percentage or amount based upon the estimated level of risk. The various risks that may be considered in making Q-Factor and other qualitative adjustments include, among other things, the impact of (i) changes in lending policies and procedures, including changes in underwriting standards and practices for collections, write-offs, and recoveries, (ii) actual and expected changes in international, national, regional, and local economic and business conditions and developments that affect the collectibility of the loan pools, (iii) changes in the nature and volume of the loan pools and in the terms of the underlying loans, (iv) changes in the experience, ability, and depth of our lending management and staff, (v) changes in volume and severity of past due financial assets, the volume of non-accrual assets, and the volume and severity of adversely classified or graded assets, (vi) changes in the quality of our credit review function, (vii) changes in the value of the underlying collateral for loans that are non-collateral dependent, (viii) the existence, growth, and effect of any concentrations of credit and (ix) other factors such as the regulatory, legal and technological environments; competition; and events such as natural disasters or health pandemics. In some cases, management may determine that an individual loan exhibits unique risk characteristics which differentiate the loan from other loans within our loan pools. In such cases, the loans are evaluated for expected credit losses on an individual basis and excluded from the collective evaluation. Specific allocations of the allowance for credit losses are determined by analyzing the borrower’s ability to repay amounts owed, collateral deficiencies, the relative risk grade of the loan and economic conditions affecting the borrower’s industry, among other things. A loan is considered to be collateral dependent when, based upon management's assessment, the borrower is experiencing financial difficulty and repayment is expected to be provided substantially through the operation or sale of the collateral. In such cases, expected credit losses are based on the fair value of the collateral at the measurement date, adjusted for estimated selling costs if satisfaction of the loan depends on the sale of the collateral. We reevaluate the fair value of collateral supporting collateral dependent loans on a quarterly basis. The fair value of real estate collateral supporting collateral dependent loans is evaluated by our internal appraisal services using a methodology that is consistent with the Uniform Standards of Professional Appraisal Practice. The fair value of collateral supporting collateral dependent construction loans is based on an “as is” valuation. During the first quarter of 2023, we recalibrated and updated all of our commercial loan models, with the exception of the models related to commercial real estate - non-owner-occupied loans, as well as our consumer real estate loan models. While the fundamental modeling methodologies remain unchanged, the updates included (i) separating the energy loan pool from the commercial and industrial pool as a result of differences in loss characteristics observed in recent history and (ii) changing the modeling approach related to loan renewals whereby each renewal is treated as a separate loan which impacted loan life assumptions. The overall approximate impact of the model updates during the first quarter was a $45.0 million decrease in modeled expected credit losses on loans though the impact of this decrease was largely offset with discretionary qualitative adjustments. The decrease in modeled expected credit losses on loans was largely driven by lower measurements for PD and LGD based on the historical data series (2008 through 2018) used for the recalibration. This period was one of relatively low losses and included higher levels of government stimulus. The lower PD and LGD measurements were also impacted by shorter loan life assumptions due to the aforementioned change in the modeling approach related to loan renewals. Generally, a commercial loan, or a portion thereof, is charged-off immediately when it is determined, through the analysis of any available current financial information with regards to the borrower, that the borrower is incapable of servicing unsecured debt, there is little or no prospect for near term improvement and no realistic strengthening action of significance is pending or, in the case of secured debt, when it is determined, through analysis of current information with regards to our collateral position, that amounts due from the borrower are in excess of the calculated current fair value of the collateral. Notwithstanding the foregoing, generally, commercial loans that become past due 180 cumulative days are charged-off. Generally, a consumer loan, or a portion thereof, is charged-off in accordance with regulatory guidelines which provide that such loans be charged-off when we become aware of the loss, such as from a triggering event that may include new information about a borrower’s intent/ability to repay the loan, bankruptcy, fraud or death, among other things, but in any event the charge-off must be taken within specified delinquency time frames. Such delinquency time frames state that closed-end retail loans (loans with pre-defined maturity dates, such as real estate mortgages, home equity loans and consumer installment loans) that become past due 120 cumulative days and open-end retail loans (loans that roll-over at the end of each term, such as home equity lines of credit) that become past due 180 cumulative days should be classified as a loss and charged-off. The following table presents year-to-date gross charge-offs by year of origination as of December 31, 2023. 2023 2022 2021 2020 2019 Prior Revolving Loans Revolving Loans Converted to Term Total Commercial and industrial $ 124 $ 1,704 $ 754 $ 157 $ 183 $ 38 $ 9,511 $ 5,844 $ 18,315 Energy — — — — — — — 518 518 Commercial real estate: Buildings, land and other — 6 146 — — 64 — — 216 Construction 739 — — — — — — — 739 Consumer real estate 118 281 348 — — 329 1,807 — 2,883 Consumer and other 23,321 4,546 74 13 1 29 2,766 510 31,260 Total $ 24,302 $ 6,537 $ 1,322 $ 170 $ 184 $ 460 $ 14,084 $ 6,872 $ 53,931 In the table above, $23.1 million of the consumer and other loan charge-offs reported as 2023 originations and $4.2 million of the total reported as 2022 originations were related to deposit overdrafts.
Off-Balance-Sheet Credit Exposure	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. The allowance is reported as a component of accrued interest payable and other liabilities in our consolidated balance sheets. Adjustments to the allowance are reported in our income statement as a component of credit loss expense. Further information regarding our policies and methodology used to estimate the allowance for credit losses on off-balance-sheet credit exposures is presented in Note 7 - Off-Balance-Sheet Arrangements, Commitments, Guarantees and Contingencies. 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. For the period of exposure, the estimate of expected credit losses considers both the likelihood that funding will occur and the amount expected to be funded over the estimated remaining life of the commitment or other off-balance-sheet exposure. The likelihood and expected amount of funding are based on historical utilization rates. 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. Estimating credit losses on amounts expected to be funded uses the same methodology as described for loans in Note 3 - Loans as if such commitments were funded. This methodology was also impacted by the model updates during the first quarter of 2023 as described in Note 3 - Loans. The overall approximate impact of the model updates was a $19.0 million decrease in modeled expected credit losses for off-balance-sheet credit exposures, though the impact of this decrease was largely offset with discretionary qualitative adjustments.
Premises and Equipment	Premises and Equipment. Land is carried at cost. Building and improvements, and furniture and equipment are carried at cost, less accumulated depreciation, computed principally by the straight-line method based on the estimated useful lives of the related property. Leasehold improvements are generally depreciated over the lesser of the term of the respective leases or the estimated useful lives of the improvements. We lease certain office facilities and office equipment under operating leases. We also own certain office facilities which we lease to outside parties under operating lessor leases; however, such leases are not significant. For operating leases other than those considered to be short-term, we recognize lease right-of-use assets and related lease liabilities. Such amounts are reported as components of premises and equipment and accrued interest payable and other liabilities, respectively, on our accompanying consolidated balance sheet. We do not recognize short-term operating leases on our balance sheet. A short-term operating lease has an original term of 12 months or less and does not have a purchase option that is likely to be exercised. In recognizing lease right-of-use assets and related lease liabilities, we account for lease and non-lease components (such as taxes, insurance, and common area maintenance costs) separately as such amounts are generally readily determinable under our lease contracts. Lease payments over the expected term are discounted using our incremental borrowing rate referenced to the Federal Home Loan Bank Secure Connect advance rates for borrowings of similar term. We also consider renewal and termination options in the determination of the term of the lease. If it is reasonably certain that a renewal or termination option will be exercised, the effects of such options are included in the determination of the expected lease term. Generally, we cannot be reasonably certain about whether or not we will renew a lease until such time the lease is within the last two years of the existing lease term. However, renewal options related to our regional headquarters facilities or operations centers are evaluated on a case-by-case basis, typically in advance of such time frame. When we are reasonably certain that a renewal option will be exercised, we measure/remeasure the right-of-use asset and related lease liability using the lease payments specified for the renewal period or, if such amounts are unspecified, we generally assume an increase (evaluated on a case-by-case basis in light of prevailing market conditions) in the lease payment over the final period of the existing lease term.
Foreclosed Assets	Foreclosed Assets . Assets acquired through or instead of loan foreclosure are held for sale and are initially recorded at fair value less estimated selling costs when acquired, establishing a new cost basis. Write-downs occurring at acquisition are charged against the allowance for credit losses on loans. Foreclosed assets are included in other assets in the accompanying consolidated balance sheets and totaled $725 thousand and $1.0 million at December 31, 2023 and 2022. Regulatory guidelines require us to reevaluate the fair value of foreclosed assets on at least an annual basis. Our policy is to comply with the regulatory guidelines. If the fair value of the asset declines, a write-down is recorded through other non-interest expense along with other expenses related to maintaining the properties. The valuation of foreclosed assets is subjective in nature and may be adjusted in the future because of changes in economic conditions. There were no write-downs of foreclosed assets in 2023 or 2022, while write-downs of foreclosed assets totaled $14 thousand in 2021. There were no significant concentrations of any properties, to which the aforementioned write-downs relate, in any single geographic region.
Revenue Recognition	Revenue Recognition . In general, for revenue not associated with financial instruments, guarantees and lease contracts, we apply the following steps when recognizing revenue from contracts with customers: (i) identify the contract, (ii) identify the performance obligations, (iii) determine the transaction price, (iv) allocate the transaction price to the performance obligations and (v) recognize revenue when a performance obligation is satisfied. Our contracts with customers are generally short term in nature, typically due within one year or less or cancellable by us or our customer upon a short notice period. Performance obligations for our customer contracts are generally satisfied at a single point in time, typically when the transaction is complete, or over time. For performance obligations satisfied over time, we primarily use the output method, directly measuring the value of the products/services transferred to the customer, to determine when performance obligations have been satisfied. We typically receive payment from customers and recognize revenue concurrent with the satisfaction of our performance obligations. In most cases, this occurs within a single financial reporting period. For payments received in advance of the satisfaction of performance obligations, revenue recognition is deferred until such time as the performance obligations have been satisfied. In cases where we have not received payment despite satisfaction of our performance obligations, we accrue an estimate of the amount due in the period our performance obligations have been satisfied. For contracts with variable components, only amounts for which collection is probable are accrued. We generally act in a principal capacity, on our own behalf, in most of our contracts with customers. In such transactions, we recognize revenue and the related costs to provide our services on a gross basis in our financial statements. In some cases, we act in an agent capacity, deriving revenue through assisting other entities in transactions with our customers. In such transactions, we recognize revenue and the related costs to provide our services on a net basis in our financial statements. These transactions recognized on a net basis primarily relate to insurance and brokerage commissions and fees derived from our customers' use of various interchange and ATM/debit card networks.
Stock Based Compensation	Share-Based Payments . Compensation expense for stock options, non-vested stock awards/stock units and deferred stock units is based on the fair value of the award on the measurement date, which, for us, is the date of the grant and is recognized ratably over the service period of the award. Compensation expense for performance stock units is based on the fair value of the award on the measurement date, which, for us, is the date of the grant and is recognized over the service period of the award based upon the probable number of units expected to vest. The fair value of stock options is estimated using a binomial lattice-based valuation model. The fair value of non-vested stock awards/stock units and deferred stock units is generally the market price of our stock on the date of grant. The fair value of performance stock units is generally the market price of our stock on the date of grant discounted by the present value of the dividends expected to be paid on our common stock during the service period of the award because dividend equivalent payments on performance stock units are deferred until such time that the units vest and shares are issued. The impact of forfeitures of share-based payment awards on compensation expense is recognized as forfeitures occur. We have three active stock compensation plans (the 2005 Omnibus Incentive Plan, the 2007 Outside Directors Incentive Plan and the 2015 Omnibus Incentive Plan). All of the plans have been approved by our shareholders. During 2015, the 2015 Omnibus Incentive Plan (“2015 Plan”) was established to replace both the 2005 Omnibus Incentive Plan (“2005 Plan”) and the 2007 Outside Directors Incentive Plan (the “2007 Directors Plan”). All remaining shares authorized for grant under the superseded 2005 Plan and 2007 Directors Plan were transferred to the 2015 Plan. Our stock compensation plans were established to (i) motivate superior performance by means of performance-related incentives, (ii) encourage and provide for the acquisition of an ownership interest in our company by employees and non-employee directors and (iii) enable us to attract and retain qualified and competent persons as employees and to serve as members of our board of directors. Under the 2015 Plan, we may grant, among other things, nonqualified stock options, incentive stock options, stock awards, stock appreciation rights, restricted stock units, performance share units or any combination thereof to certain employees and non-employee directors. Any of the authorized shares may be used for any type of award allowable under the Plan. The Compensation and Benefits Committee (“Committee”) of our Board of Directors has sole authority to (i) establish the awards to be issued, (ii) select the employees and non-employee directors to receive awards, and (iii) approve the terms and conditions of each award contract. Each award under the stock plans is evidenced by an award agreement that specifies the award price, the duration of the award, the number of shares to which the award pertains, and such other provisions as the Committee determines. For stock options, the option price for each grant is at least equal to the fair market value of a share of Cullen/Frost’s common stock on the date of grant. Options granted expire at such time as the Committee determines at the date of grant and in no event does the exercise period exceed a maximum of ten years. As defined in the plans, outstanding awards may immediately vest upon a change-in-control of Cullen/Frost and, in the case of awards granted under the 2015 Plan, subsequent termination resulting from the change in control. Options awarded to employees generally have a ten four three four Performance stock units represent shares potentially issuable in the future. For performance stock units granted in 2023, 2022 and 2021, issuance is based upon the measure of our achievement of growth in adjusted net revenue, averaged over the three-year performance period, compared to the 2023, 2022 and 2021 base-year amounts, respectively. For performance stock units granted prior to 2021, issuance is based upon the measure of our achievement of relative return on assets over a three-year performance period compared to an identified peer group's achievement of relative return on assets over the same three-year performance period. Performance stock units are eligible to receive equivalent dividend payments as such dividends are declared on our common stock during the performance period. Equivalent dividend payments are based upon the ultimate number of shares issued under each performance award and are deferred until such time that the units vest and shares are issued. Stock-based Compensation Expense. Valuation of Stock-Based Compensation . For the purposes of recognizing stock-based compensation expense, the fair value of non-vested restricted stock units and director deferred stock units is generally the market price of the stock on the measurement date, which, for us, is the date of the award. The fair value of performance stock units is determined in a similar manner except that the market price of the stock on the measurement date is discounted by the present value of the dividends expected to be paid on our common stock during the service period of the award because dividend equivalent payments on performance stock units are deferred until such time that the units vest and shares are issued. In applying this discount to the market price of our stock on the measurement date, we assumed we would pay a flat quarterly dividend during the service period equal to our most recent dividend payment, which was $0.92, $0.87 and $0.75 in 2023, 2022 and 2021, respectively, discounted at a weighted-average risk-free rate of 5.01%, 4.45% and 0.77% in 2023, 2022 and 2021, respectively.
Advertising Costs	Advertising Costs. Advertising costs are expensed as incurred.
Income Taxes	Income Taxes . Income tax expense is the total of the current year income tax due or refundable and the change in deferred tax assets and liabilities (excluding deferred tax assets and liabilities related to business combinations or components of other comprehensive income). Deferred tax assets and liabilities are the expected future tax amounts for the temporary differences between carrying amounts and tax bases of assets and liabilities, computed using enacted tax rates. A valuation allowance, if needed, reduces deferred tax assets to the expected amount most likely to be realized. Realization of deferred tax assets is dependent upon the generation of a sufficient level of future taxable income. Although realization is not assured, management believes it is more likely than not that all of the deferred tax assets will be realized. Interest and/or penalties related to income taxes are reported as a component of income tax expense. The income tax effects related to settlements of share-based payment awards are reported in earnings as an increase (or decrease) to income tax expense. See Note 12 - Income Taxes. We file a consolidated income tax return with our subsidiaries. Federal income tax expense or benefit has been allocated to subsidiaries on a separate return basis.
Basic and Diluted Earnings Per Common Share	Basic and Diluted Earnings Per Common Share. Earnings per common share is computed using the two-class method prescribed under ASC Topic 260, “Earnings Per Share.” ASC 260 provides that unvested share-based payment awards that contain nonforfeitable rights to dividends or dividend equivalents (whether paid or unpaid) are participating securities and shall be included in the computation of earnings per share pursuant to the two-class method. We have determined that our outstanding non-vested stock awards/stock units and deferred stock units are participating securities. Under the two-class method, basic earnings per common share is computed by dividing net earnings allocated to common stock by the weighted-average number of common shares outstanding during the applicable period, excluding outstanding participating securities. Diluted earnings per common share is computed using the weighted-average number of shares determined for the basic earnings per common share computation plus the dilutive effect of stock compensation using the treasury stock method. A reconciliation of the weighted-average shares used in calculating basic earnings per common share and the weighted average common shares used in calculating diluted earnings per common share for the reported periods is provided in Note 9 - Earnings Per Common Share. Earnings Per Common Share . Earnings per common share is computed using the two-class method. Basic earnings per common share is computed by dividing net earnings allocated to common stock by the weighted-average number of common shares outstanding during the applicable period, excluding outstanding participating securities. Participating securities include non-vested stock awards/stock units, deferred stock units and performance stock units (during the performance period), though no actual shares of common stock related to any type of stock unit have been issued. Non-vested stock awards/stock units and deferred stock units are considered participating securities because holders of these securities receive non-forfeitable dividends at the same rate as holders of our common stock. Holders of performance stock units receive dividend equivalent payments for dividends paid during the performance period at the vesting date of the award based upon the number of units that ultimately vest. Diluted earnings per common share is computed using the weighted-average number of shares determined for the basic earnings per common share computation plus the dilutive effect of stock compensation using the treasury stock method.
Comprehensive Income	Comprehensive Income. Comprehensive income includes all changes in shareholders’ equity during a period, except those resulting from transactions with shareholders. Besides net income, other components of our comprehensive income include the after tax effect of changes in the net unrealized gain/loss on securities available for sale, changes in the net unrealized gain on securities transferred to held to maturity and changes in the net actuarial gain/loss on defined benefit post-retirement benefit plans. See Note 13 - Other Comprehensive Income (Loss).
Derivative Financial Instruments	Derivative Financial Instruments . Our hedging policies permit the use of various derivative financial instruments to manage interest rate risk or to hedge specified assets and liabilities. All derivatives are recorded at fair value on our balance sheet. Derivatives executed with the same counterparty are generally subject to master netting arrangements, however, fair value amounts recognized for derivatives and fair value amounts recognized for the right/obligation to reclaim/return cash collateral are not offset for financial reporting purposes. We may be required to recognize certain contracts and commitments as derivatives when the characteristics of those contracts and commitments meet the definition of a derivative. To qualify for hedge accounting, derivatives must be highly effective at reducing the risk associated with the exposure being hedged and must be designated as a hedge at the inception of the derivative contract. We consider a hedge to be highly effective if the change in fair value of the derivative hedging instrument is within 80% to 125% of the opposite change in the fair value of the hedged item attributable to the hedged risk. If derivative instruments are designated as hedges of fair values, and such hedges are highly effective, both the change in the fair value of the hedge and the hedged item are included in current earnings. Fair value adjustments related to cash flow hedges are recorded in other comprehensive income and are reclassified to earnings when the hedged transaction is reflected in earnings. Ineffective portions of hedges are reflected in earnings as they occur. Actual cash receipts and/or payments and related accruals on derivatives related to hedges are recorded as adjustments to the interest income or interest expense associated with the hedged item. During the life of the hedge, we formally assess whether derivatives designated as hedging instruments continue to be highly effective in offsetting changes in the fair value or cash flows of hedged items. If it is determined that a hedge has ceased to be highly effective, we will discontinue hedge accounting prospectively. At such time, previous adjustments to the carrying value of the hedged item are reversed into current earnings and the derivative instrument is reclassified to a trading position recorded at fair value.
Fair Value Measurements	Fair Value Measurements . In general, fair values of financial instruments are based upon quoted market prices, where available. If such quoted market prices are not available, fair value is based upon internally developed models that primarily use, as inputs, observable market-based parameters. Valuation adjustments may be made to ensure that financial instruments are recorded at fair value. These adjustments may include amounts to reflect counterparty credit quality and our creditworthiness, among other things, as well as unobservable parameters. Any such valuation adjustments are applied consistently over time. See Note 16 - 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 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. The fair value hierarchy is as follows: • Level 1 Inputs - Unadjusted quoted prices in active markets for identical assets or liabilities that the reporting entity has the ability to access at the measurement date. • Level 2 Inputs - Inputs other than quoted prices included in Level 1 that are observable for the asset or liability, either directly or indirectly. These might include quoted prices for similar assets or liabilities in active markets, quoted prices for identical or similar assets or liabilities in markets that are not active, inputs other than quoted prices that are observable for the asset or liability (such as interest rates, volatilities, prepayment speeds, credit risks, etc.) or inputs that are derived principally from or corroborated by market data by correlation or other means. • Level 3 Inputs - Unobservable inputs for determining the fair values of assets or liabilities that reflect an entity’s own assumptions about the assumptions that market participants would use in pricing the assets or liabilities. In general, fair value is based upon quoted market prices, where available. If such quoted market prices are not available, fair value is based upon internally developed models that primarily use, as inputs, observable market-based parameters. Valuation adjustments may be made to ensure that financial instruments are recorded at fair value. These adjustments may include amounts to reflect counterparty credit quality and our creditworthiness, among other things, as well as unobservable parameters. Any such valuation adjustments are applied consistently over time. Our valuation methodologies may produce a fair value calculation that may not be indicative of net realizable value or reflective of future fair values. While management believes our valuation methodologies are appropriate and consistent with other market participants, the use of different methodologies or assumptions to determine the fair value of certain financial instruments could result in a different estimate of fair value at the reporting date. Furthermore, the reported fair value amounts have not been comprehensively revalued since the presentation dates, and therefore, estimates of fair value after the balance sheet date may differ significantly from the amounts presented herein. A more detailed description of the valuation methodologies used for assets and liabilities measured at fair value is set forth below. Transfers between levels of the fair value hierarchy are recognized on the actual date of the event or circumstances that caused the transfer, which generally coincides with our monthly and/or quarterly valuation process. Financial Assets and Financial Liabilities: Financial assets and financial liabilities measured at fair value on a recurring basis include the following: Securities Available for Sale . U.S. Treasury securities are reported at fair value utilizing Level 1 inputs. Other securities classified as available for sale are reported at fair value utilizing Level 2 inputs. For these securities, we obtain fair value measurements from an independent pricing service. The fair value measurements consider observable data that may include dealer quotes, market spreads, cash flows, the U.S. Treasury yield curve, live trading levels, trade execution data, market consensus prepayment speeds, credit information and the bond’s terms and conditions, among other things. We review the prices supplied by the independent pricing service, as well as their underlying pricing methodologies, for reasonableness and to ensure such prices are aligned with traditional pricing matrices. In general, we do not purchase investment portfolio securities that are esoteric or that have a complicated structure. Our entire portfolio consists of traditional investments, nearly all of which are U.S. Treasury obligations, federal agency bullet or mortgage pass-through securities, or general obligation or revenue based municipal bonds. Pricing for such instruments is fairly generic and is easily obtained. From time to time, we will validate prices supplied by the independent pricing service by comparison to prices obtained from third-party sources or derived using internal models. Trading Securities . U.S. Treasury securities and exchange-listed common stock are reported at fair value utilizing Level 1 inputs. Other securities classified as trading are reported at fair value utilizing Level 2 inputs in the same manner as described above for securities available for sale. Derivatives . Derivatives are generally reported at fair value utilizing Level 2 inputs, except for foreign currency contracts, which are reported at fair value utilizing Level 1 inputs. We obtain dealer quotations and utilize internally developed valuation models to value commodity swaps/options. We utilize internally developed valuation models and/or third-party models with observable market data inputs to validate the valuations provided by the dealers. Though there has never been a significant discrepancy in the valuations, should such a significant discrepancy arise, we would obtain price verification from a third-party dealer. We utilize internal valuation methods with observable market data inputs to estimate fair values of customer interest rate swaps, caps and floors. We also obtain dealer quotations for these derivatives for comparative purposes to assess the reasonableness of the model valuations. In cases where significant credit valuation adjustments are incorporated into the estimation of fair value, reported amounts are considered to have been derived utilizing Level 3 inputs. For purposes of potential valuation adjustments to our derivative positions, we evaluate the credit risk of our counterparties as well as ours. Accordingly, we have considered factors such as the likelihood of our default and the default of our counterparties, our net exposures and remaining contractual life, among other things, in determining if any fair value adjustments related to credit risk are required. Counterparty exposure is evaluated by netting positions that are subject to master netting arrangements, as well as considering the amount of collateral securing the position. We review our counterparty exposure on a regular basis, and, when necessary, appropriate business actions are taken to adjust the exposure. We also utilize this approach to estimate our own credit risk on derivative liability positions. To date, we have not realized any significant losses due to a counterparty’s inability to pay any net uncollateralized position. The change in value of derivative assets and derivative liabilities attributable to credit risk was not significant during the reported periods. 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 (for example, when there is evidence of impairment). Financial assets measured at fair value on a non-recurring basis during the reported periods include certain impaired loans reported at the fair value of the underlying collateral if repayment is expected solely from the collateral. Collateral values are estimated using Level 2 inputs based on observable market data, typically in the case of real estate collateral, or Level 3 inputs based on customized discounting criteria, typically in the case of non-real estate collateral such as inventory, oil and gas reserves, accounts receivable, equipment or other business assets. 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. Such fair value measurements were not significant during the reported periods. Charge-offs recognized upon loan foreclosures are generally offset by general or specific allocations of the allowance for credit losses on loans and generally do not, and did not during the reported periods, significantly impact our credit loss expense. Regulatory guidelines require us to reevaluate the fair value of other real estate owned on at least an annual basis. While our policy is to comply with the regulatory guidelines, our general practice is to reevaluate the fair value of collateral supporting impaired collateral dependent loans on a quarterly basis. Thus, appraisals are generally not considered to be outdated, and we typically do not make any adjustments to the appraised values. ASC Topic 825, “Financial Instruments,” requires disclosure of the fair value of financial assets and financial liabilities, including those financial assets and financial liabilities that are not measured and reported at fair value on a recurring basis or non-recurring basis. The estimated fair value approximates carrying value for cash and cash equivalents, accrued interest and the cash surrender value of life insurance policies. The methodologies for other financial assets and financial liabilities that are not measured and reported at fair value on a recurring basis or non-recurring basis are discussed below: Loans . The estimated fair value approximates carrying value for variable-rate loans that reprice frequently and with no significant change in credit risk. The fair value of fixed-rate loans and variable-rate loans which reprice on an infrequent basis is estimated by discounting future cash flows using the current interest rates at which similar loans with similar terms would be made to borrowers of similar credit quality. An overall valuation adjustment is made for specific credit risks as well as general portfolio credit risk. Deposits . The estimated fair value approximates carrying value for demand deposits. The fair value of fixed-rate deposit liabilities with defined maturities is estimated by discounting future cash flows using the interest rates currently offered for deposits of similar remaining maturities. The estimated fair value of deposits does not take into account the value of our long-term relationships with depositors, commonly known as core deposit intangibles, which are separate intangible assets, and not considered financial instruments. Nonetheless, we would likely realize a core deposit premium if our deposit portfolio were sold in the principal market for such deposits. Borrowed Funds . The estimated fair value approximates carrying value for short-term borrowings. The fair value of long-term fixed-rate borrowings is estimated using quoted market prices, if available, or by discounting future cash flows using current interest rates for similar financial instruments. The estimated fair value approximates carrying value for variable-rate junior subordinated deferrable interest debentures that reprice quarterly. Loan Commitments, Standby and Commercial Letters of Credit . Our lending commitments have variable interest rates and “escape” clauses if the customer’s credit quality deteriorates. Therefore, the fair values of these items are not significant and are not included in the following table.
Transfers of Financial Assets	Transfers of Financial Assets . Transfers of financial assets are accounted for as sales when control over the assets has been surrendered. Control over transferred assets is deemed to be surrendered when (i) the assets have been isolated from us, (ii) the transferee obtains the right (free of conditions that constrain it from taking advantage of that right) to pledge or exchange the transferred assets, and (iii) we do not maintain effective control over the transferred assets through an agreement to repurchase them before their maturity.
Loss Contingencies	Loss Contingencies . Loss contingencies, including claims and legal actions arising in the ordinary course of business are recorded as liabilities when the likelihood of loss is probable and an amount or range of loss can be reasonably estimated.
Trust Assets	Trust Assets. Assets of our trust department, other than cash on deposit at Frost Bank, are not included in the accompanying financial statements because they are not our assets.
Accounting Changes, Reclassifications and Restatement	Accounting Changes, Reclassifications and Restatements.
Reclassification, Comparability Adjustment	Certain items in prior financial statements have been reclassified to conform to the current presentation.

Receivables, Loans, Notes Recei

Receivables, Loans, Notes Receivable, and Others (Policies)	12 Months Ended
	Dec. 31, 2023
Receivables [Abstract]
Allowance for Credit Losses Loans	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 management's best estimate of the net amount expected to be collected. Loans are charged-off against the allowance when deemed uncollectible by management. Expected recoveries do not exceed the aggregate of amounts previously charged-off and expected to be charged-off. Adjustments to the allowance are reported in our income statement as a component of credit loss expense. Management has made the accounting policy election to exclude accrued interest receivable on loans from the estimate of credit losses. Further information regarding our policies and methodology used to estimate the allowance for credit losses on loans is presented in Note 3 - Loans. 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. The contractual term excludes expected extensions, renewals and modifications unless (i) management has a reasonable expectation that a loan to an individual borrower that is experiencing financial difficulty will be modified or (ii) such extension or renewal options are not unconditionally cancellable by us and, in such cases, the borrower is likely to meet applicable conditions and likely to request extension or renewal. Relevant available information includes historical credit loss experience, current conditions and reasonable and supportable forecasts. While historical credit loss experience provides the basis for the estimation of expected credit losses, adjustments to historical loss information may be made for differences in current portfolio-specific risk characteristics, environmental conditions or other relevant factors. The allowance for credit losses is measured on a collective basis for portfolios of loans when similar risk characteristics exist. Loans that do not share risk characteristics are evaluated for expected credit losses on an individual basis and excluded from the collective evaluation. Expected credit losses for collateral dependent loans, including loans where the borrower is experiencing financial difficulty but foreclosure is not probable, are based on the fair value of the collateral at the reporting date, adjusted for selling costs as 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. In calculating the allowance for credit losses, most loans are segmented into pools based upon similar characteristics and risk profiles. Common characteristics and risk profiles include the type/purpose of loan, underlying collateral, geographical similarity and historical/expected credit loss patterns. In developing these loan pools for the purposes of modeling expected credit losses, we also analyzed the degree of correlation in how loans within each portfolio respond when subjected to varying economic conditions and scenarios as well as other portfolio stress factors. For modeling purposes, our loan pools include (i) commercial and industrial non-revolving, (ii) commercial and industrial revolving, (iii) energy, (iv) commercial real estate - owner occupied, (v) commercial real estate - non-owner occupied, (vi) commercial real estate - construction/land development, (vii) consumer real estate and (viii) consumer and other. Prior to 2023, energy loans were included within the commercial and industrial loan pools. See discussion of the 2023 model updates below. We periodically reassess each pool to ensure the loans within the pool continue to share similar characteristics and risk profiles and to determine whether further segmentation is necessary. For each loan pool, we measure expected credit losses over the life of each loan utilizing a combination of models which measure (i) probability of default (“PD”), which is the likelihood that loan will stop performing/default, (ii) probability of attrition (“PA”), which is the likelihood that a loan will pay-off prior to maturity, (iii) loss given default (“LGD”), which is the expected loss rate for loans in default and (iv) exposure at default (“EAD”), which is the estimated outstanding principal balance of the loans upon default, including the expected funding of unfunded commitments outstanding as of the measurement date. For certain commercial loan portfolios, the PD is calculated using a transition matrix to determine the likelihood of a customer’s risk grade migrating from one specified range of risk grades to a different specified range. Expected credit losses are calculated as the product of PD (adjusted for attrition), LGD and EAD. This methodology builds on default probabilities already incorporated into our risk grading process by utilizing pool-specific historical loss rates to calculate expected credit losses. These pool-specific historical loss rates may be adjusted for current macroeconomic assumptions, as further discussed below, and other factors such as differences in underwriting standards, portfolio mix, or when historical asset terms do not reflect the contractual terms of the financial assets being evaluated as of the measurement date. Each time we measure expected credit losses, we assess the relevancy of historical loss information and consider any necessary adjustments to address any differences in asset-specific characteristics. Due to their short-term nature, expected credit losses for overdrafts included in consumer and other loans are based solely upon a weighting of recent historical charge-offs over a period of three years. The measurement of expected credit losses is impacted by loan/borrower attributes and certain macroeconomic variables. Significant loan/borrower attributes utilized in our modeling processes include, among other things, (i) origination date, (ii) maturity date, (iii) payment type, (iv) collateral type and amount, (v) current risk grade, (vi) current unpaid balance and commitment utilization rate, (vii) payment status/delinquency history and (viii) expected recoveries of previously charged-off amounts. Significant macroeconomic variables utilized in our modeling processes include, among other things, (i) Gross State Product for Texas and U.S. Gross Domestic Product, (ii) selected market interest rates including U.S. Treasury rates, bank prime rate, 30-year fixed mortgage rate, BBB corporate bond rate, among others, (iii) unemployment rates, (iv) commercial and residential property prices in Texas and the U.S. as a whole, (v) West Texas Intermediate crude oil price and (vi) total stock market index. PD and PA were estimated by analyzing internally-sourced data related to historical performance of each loan pool over a complete economic cycle. PD and PA are adjusted to reflect the current impact of certain macroeconomic variables as well as their expected changes over a reasonable and supportable forecast period. We have determined that we are reasonably able to forecast the macroeconomic variables used in our modeling processes with an acceptable degree of confidence for a total of two years with the last twelve months of the forecast period encompassing a reversion process whereby the forecasted macroeconomic variables are reverted to their historical mean utilizing a rational, systematic basis. The macroeconomic variables utilized as inputs in our modeling processes were subjected to a variety of analysis procedures and were selected primarily based on statistical relevancy and correlation to our historical credit losses. By reverting these modeling inputs to their historical mean and considering loan/borrower specific attributes, our models are intended to yield a measurement of expected credit losses that reflects our average historical loss rates for periods subsequent to the twelve-month reversion period. The LGD is based on historical recovery averages for each loan pool, adjusted to reflect the current impact of certain macroeconomic variables as well as their expected changes over a two-year forecast period, with the final twelve months of the forecast period encompassing a reversion process, which management considers to be both reasonable and supportable. This same forecast/reversion period is used for all macroeconomic variables used in all of our models. EAD is estimated using a linear regression model that estimates the average percentage of the loan balance that remains at the time of a default event. Management qualitatively adjusts model results for risk factors that are not considered within our modeling processes but are nonetheless relevant in assessing the expected credit losses within our loan pools. These qualitative factor (“Q-Factor”) and other qualitative adjustments may increase or decrease management's estimate of expected credit losses by a calculated percentage or amount based upon the estimated level of risk. The various risks that may be considered in making Q-Factor and other qualitative adjustments include, among other things, the impact of (i) changes in lending policies and procedures, including changes in underwriting standards and practices for collections, write-offs, and recoveries, (ii) actual and expected changes in international, national, regional, and local economic and business conditions and developments that affect the collectibility of the loan pools, (iii) changes in the nature and volume of the loan pools and in the terms of the underlying loans, (iv) changes in the experience, ability, and depth of our lending management and staff, (v) changes in volume and severity of past due financial assets, the volume of non-accrual assets, and the volume and severity of adversely classified or graded assets, (vi) changes in the quality of our credit review function, (vii) changes in the value of the underlying collateral for loans that are non-collateral dependent, (viii) the existence, growth, and effect of any concentrations of credit and (ix) other factors such as the regulatory, legal and technological environments; competition; and events such as natural disasters or health pandemics. In some cases, management may determine that an individual loan exhibits unique risk characteristics which differentiate the loan from other loans within our loan pools. In such cases, the loans are evaluated for expected credit losses on an individual basis and excluded from the collective evaluation. Specific allocations of the allowance for credit losses are determined by analyzing the borrower’s ability to repay amounts owed, collateral deficiencies, the relative risk grade of the loan and economic conditions affecting the borrower’s industry, among other things. A loan is considered to be collateral dependent when, based upon management's assessment, the borrower is experiencing financial difficulty and repayment is expected to be provided substantially through the operation or sale of the collateral. In such cases, expected credit losses are based on the fair value of the collateral at the measurement date, adjusted for estimated selling costs if satisfaction of the loan depends on the sale of the collateral. We reevaluate the fair value of collateral supporting collateral dependent loans on a quarterly basis. The fair value of real estate collateral supporting collateral dependent loans is evaluated by our internal appraisal services using a methodology that is consistent with the Uniform Standards of Professional Appraisal Practice. The fair value of collateral supporting collateral dependent construction loans is based on an “as is” valuation. During the first quarter of 2023, we recalibrated and updated all of our commercial loan models, with the exception of the models related to commercial real estate - non-owner-occupied loans, as well as our consumer real estate loan models. While the fundamental modeling methodologies remain unchanged, the updates included (i) separating the energy loan pool from the commercial and industrial pool as a result of differences in loss characteristics observed in recent history and (ii) changing the modeling approach related to loan renewals whereby each renewal is treated as a separate loan which impacted loan life assumptions. The overall approximate impact of the model updates during the first quarter was a $45.0 million decrease in modeled expected credit losses on loans though the impact of this decrease was largely offset with discretionary qualitative adjustments. The decrease in modeled expected credit losses on loans was largely driven by lower measurements for PD and LGD based on the historical data series (2008 through 2018) used for the recalibration. This period was one of relatively low losses and included higher levels of government stimulus. The lower PD and LGD measurements were also impacted by shorter loan life assumptions due to the aforementioned change in the modeling approach related to loan renewals. Generally, a commercial loan, or a portion thereof, is charged-off immediately when it is determined, through the analysis of any available current financial information with regards to the borrower, that the borrower is incapable of servicing unsecured debt, there is little or no prospect for near term improvement and no realistic strengthening action of significance is pending or, in the case of secured debt, when it is determined, through analysis of current information with regards to our collateral position, that amounts due from the borrower are in excess of the calculated current fair value of the collateral. Notwithstanding the foregoing, generally, commercial loans that become past due 180 cumulative days are charged-off. Generally, a consumer loan, or a portion thereof, is charged-off in accordance with regulatory guidelines which provide that such loans be charged-off when we become aware of the loss, such as from a triggering event that may include new information about a borrower’s intent/ability to repay the loan, bankruptcy, fraud or death, among other things, but in any event the charge-off must be taken within specified delinquency time frames. Such delinquency time frames state that closed-end retail loans (loans with pre-defined maturity dates, such as real estate mortgages, home equity loans and consumer installment loans) that become past due 120 cumulative days and open-end retail loans (loans that roll-over at the end of each term, such as home equity lines of credit) that become past due 180 cumulative days should be classified as a loss and charged-off. The following table presents year-to-date gross charge-offs by year of origination as of December 31, 2023. 2023 2022 2021 2020 2019 Prior Revolving Loans Revolving Loans Converted to Term Total Commercial and industrial $ 124 $ 1,704 $ 754 $ 157 $ 183 $ 38 $ 9,511 $ 5,844 $ 18,315 Energy — — — — — — — 518 518 Commercial real estate: Buildings, land and other — 6 146 — — 64 — — 216 Construction 739 — — — — — — — 739 Consumer real estate 118 281 348 — — 329 1,807 — 2,883 Consumer and other 23,321 4,546 74 13 1 29 2,766 510 31,260 Total $ 24,302 $ 6,537 $ 1,322 $ 170 $ 184 $ 460 $ 14,084 $ 6,872 $ 53,931 In the table above, $23.1 million of the consumer and other loan charge-offs reported as 2023 originations and $4.2 million of the total reported as 2022 originations were related to deposit overdrafts.

Fair Value Measures and Disclos

Fair Value Measures and Disclosures (Policies)	12 Months Ended
	Dec. 31, 2023
Fair Value Disclosures [Abstract]
Off-Balance-Sheet Credit Exposure	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. The allowance is reported as a component of accrued interest payable and other liabilities in our consolidated balance sheets. Adjustments to the allowance are reported in our income statement as a component of credit loss expense. Further information regarding our policies and methodology used to estimate the allowance for credit losses on off-balance-sheet credit exposures is presented in Note 7 - Off-Balance-Sheet Arrangements, Commitments, Guarantees and Contingencies. 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. For the period of exposure, the estimate of expected credit losses considers both the likelihood that funding will occur and the amount expected to be funded over the estimated remaining life of the commitment or other off-balance-sheet exposure. The likelihood and expected amount of funding are based on historical utilization rates. 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. Estimating credit losses on amounts expected to be funded uses the same methodology as described for loans in Note 3 - Loans as if such commitments were funded. This methodology was also impacted by the model updates during the first quarter of 2023 as described in Note 3 - Loans. The overall approximate impact of the model updates was a $19.0 million decrease in modeled expected credit losses for off-balance-sheet credit exposures, though the impact of this decrease was largely offset with discretionary qualitative adjustments.

Regulated Operations (Policies)

Regulated Operations (Policies)	12 Months Ended
	Dec. 31, 2023
Regulated Operations [Abstract]
Insider Trading Policies and Procedures	Insider Trading Policies and Procedures. Our board of directors has adopted insider trading policies and procedures governing the purchase, sale, and/or other dispositions of our securities by directors, officers and employees, or by Cullen/Frost itself. These policies have been reasonably designed to promote compliance with insider trading laws, rules and regulations, and applicable New York Stock Exchange listing standards.

Earnings Per Share (Policies)

Earnings Per Share (Policies)	12 Months Ended
	Dec. 31, 2023
Earnings Per Share [Abstract]
Basic and Diluted Earnings Per Common Share	Basic and Diluted Earnings Per Common Share. Earnings per common share is computed using the two-class method prescribed under ASC Topic 260, “Earnings Per Share.” ASC 260 provides that unvested share-based payment awards that contain nonforfeitable rights to dividends or dividend equivalents (whether paid or unpaid) are participating securities and shall be included in the computation of earnings per share pursuant to the two-class method. We have determined that our outstanding non-vested stock awards/stock units and deferred stock units are participating securities. Under the two-class method, basic earnings per common share is computed by dividing net earnings allocated to common stock by the weighted-average number of common shares outstanding during the applicable period, excluding outstanding participating securities. Diluted earnings per common share is computed using the weighted-average number of shares determined for the basic earnings per common share computation plus the dilutive effect of stock compensation using the treasury stock method. A reconciliation of the weighted-average shares used in calculating basic earnings per common share and the weighted average common shares used in calculating diluted earnings per common share for the reported periods is provided in Note 9 - Earnings Per Common Share. Earnings Per Common Share . Earnings per common share is computed using the two-class method. Basic earnings per common share is computed by dividing net earnings allocated to common stock by the weighted-average number of common shares outstanding during the applicable period, excluding outstanding participating securities. Participating securities include non-vested stock awards/stock units, deferred stock units and performance stock units (during the performance period), though no actual shares of common stock related to any type of stock unit have been issued. Non-vested stock awards/stock units and deferred stock units are considered participating securities because holders of these securities receive non-forfeitable dividends at the same rate as holders of our common stock. Holders of performance stock units receive dividend equivalent payments for dividends paid during the performance period at the vesting date of the award based upon the number of units that ultimately vest. Diluted earnings per common share is computed using the weighted-average number of shares determined for the basic earnings per common share computation plus the dilutive effect of stock compensation using the treasury stock method.

Compensation Related Costs, Pos

Compensation Related Costs, Postemployment Benefits (Policies)	12 Months Ended
	Dec. 31, 2023
Postemployment Benefits [Abstract]
Stock Based Compensation	Share-Based Payments . Compensation expense for stock options, non-vested stock awards/stock units and deferred stock units is based on the fair value of the award on the measurement date, which, for us, is the date of the grant and is recognized ratably over the service period of the award. Compensation expense for performance stock units is based on the fair value of the award on the measurement date, which, for us, is the date of the grant and is recognized over the service period of the award based upon the probable number of units expected to vest. The fair value of stock options is estimated using a binomial lattice-based valuation model. The fair value of non-vested stock awards/stock units and deferred stock units is generally the market price of our stock on the date of grant. The fair value of performance stock units is generally the market price of our stock on the date of grant discounted by the present value of the dividends expected to be paid on our common stock during the service period of the award because dividend equivalent payments on performance stock units are deferred until such time that the units vest and shares are issued. The impact of forfeitures of share-based payment awards on compensation expense is recognized as forfeitures occur. We have three active stock compensation plans (the 2005 Omnibus Incentive Plan, the 2007 Outside Directors Incentive Plan and the 2015 Omnibus Incentive Plan). All of the plans have been approved by our shareholders. During 2015, the 2015 Omnibus Incentive Plan (“2015 Plan”) was established to replace both the 2005 Omnibus Incentive Plan (“2005 Plan”) and the 2007 Outside Directors Incentive Plan (the “2007 Directors Plan”). All remaining shares authorized for grant under the superseded 2005 Plan and 2007 Directors Plan were transferred to the 2015 Plan. Our stock compensation plans were established to (i) motivate superior performance by means of performance-related incentives, (ii) encourage and provide for the acquisition of an ownership interest in our company by employees and non-employee directors and (iii) enable us to attract and retain qualified and competent persons as employees and to serve as members of our board of directors. Under the 2015 Plan, we may grant, among other things, nonqualified stock options, incentive stock options, stock awards, stock appreciation rights, restricted stock units, performance share units or any combination thereof to certain employees and non-employee directors. Any of the authorized shares may be used for any type of award allowable under the Plan. The Compensation and Benefits Committee (“Committee”) of our Board of Directors has sole authority to (i) establish the awards to be issued, (ii) select the employees and non-employee directors to receive awards, and (iii) approve the terms and conditions of each award contract. Each award under the stock plans is evidenced by an award agreement that specifies the award price, the duration of the award, the number of shares to which the award pertains, and such other provisions as the Committee determines. For stock options, the option price for each grant is at least equal to the fair market value of a share of Cullen/Frost’s common stock on the date of grant. Options granted expire at such time as the Committee determines at the date of grant and in no event does the exercise period exceed a maximum of ten years. As defined in the plans, outstanding awards may immediately vest upon a change-in-control of Cullen/Frost and, in the case of awards granted under the 2015 Plan, subsequent termination resulting from the change in control. Options awarded to employees generally have a ten four three four Performance stock units represent shares potentially issuable in the future. For performance stock units granted in 2023, 2022 and 2021, issuance is based upon the measure of our achievement of growth in adjusted net revenue, averaged over the three-year performance period, compared to the 2023, 2022 and 2021 base-year amounts, respectively. For performance stock units granted prior to 2021, issuance is based upon the measure of our achievement of relative return on assets over a three-year performance period compared to an identified peer group's achievement of relative return on assets over the same three-year performance period. Performance stock units are eligible to receive equivalent dividend payments as such dividends are declared on our common stock during the performance period. Equivalent dividend payments are based upon the ultimate number of shares issued under each performance award and are deferred until such time that the units vest and shares are issued. Stock-based Compensation Expense. Valuation of Stock-Based Compensation . For the purposes of recognizing stock-based compensation expense, the fair value of non-vested restricted stock units and director deferred stock units is generally the market price of the stock on the measurement date, which, for us, is the date of the award. The fair value of performance stock units is determined in a similar manner except that the market price of the stock on the measurement date is discounted by the present value of the dividends expected to be paid on our common stock during the service period of the award because dividend equivalent payments on performance stock units are deferred until such time that the units vest and shares are issued. In applying this discount to the market price of our stock on the measurement date, we assumed we would pay a flat quarterly dividend during the service period equal to our most recent dividend payment, which was $0.92, $0.87 and $0.75 in 2023, 2022 and 2021, respectively, discounted at a weighted-average risk-free rate of 5.01%, 4.45% and 0.77% in 2023, 2022 and 2021, respectively.

Fair Value Measures and Discl_2

Fair Value Measures and Disclosures (Policies)	12 Months Ended
	Dec. 31, 2023
Fair Value Disclosures [Abstract]
Fair Value Measurements	Fair Value Measurements . In general, fair values of financial instruments are based upon quoted market prices, where available. If such quoted market prices are not available, fair value is based upon internally developed models that primarily use, as inputs, observable market-based parameters. Valuation adjustments may be made to ensure that financial instruments are recorded at fair value. These adjustments may include amounts to reflect counterparty credit quality and our creditworthiness, among other things, as well as unobservable parameters. Any such valuation adjustments are applied consistently over time. See Note 16 - 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 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. The fair value hierarchy is as follows: • Level 1 Inputs - Unadjusted quoted prices in active markets for identical assets or liabilities that the reporting entity has the ability to access at the measurement date. • Level 2 Inputs - Inputs other than quoted prices included in Level 1 that are observable for the asset or liability, either directly or indirectly. These might include quoted prices for similar assets or liabilities in active markets, quoted prices for identical or similar assets or liabilities in markets that are not active, inputs other than quoted prices that are observable for the asset or liability (such as interest rates, volatilities, prepayment speeds, credit risks, etc.) or inputs that are derived principally from or corroborated by market data by correlation or other means. • Level 3 Inputs - Unobservable inputs for determining the fair values of assets or liabilities that reflect an entity’s own assumptions about the assumptions that market participants would use in pricing the assets or liabilities. In general, fair value is based upon quoted market prices, where available. If such quoted market prices are not available, fair value is based upon internally developed models that primarily use, as inputs, observable market-based parameters. Valuation adjustments may be made to ensure that financial instruments are recorded at fair value. These adjustments may include amounts to reflect counterparty credit quality and our creditworthiness, among other things, as well as unobservable parameters. Any such valuation adjustments are applied consistently over time. Our valuation methodologies may produce a fair value calculation that may not be indicative of net realizable value or reflective of future fair values. While management believes our valuation methodologies are appropriate and consistent with other market participants, the use of different methodologies or assumptions to determine the fair value of certain financial instruments could result in a different estimate of fair value at the reporting date. Furthermore, the reported fair value amounts have not been comprehensively revalued since the presentation dates, and therefore, estimates of fair value after the balance sheet date may differ significantly from the amounts presented herein. A more detailed description of the valuation methodologies used for assets and liabilities measured at fair value is set forth below. Transfers between levels of the fair value hierarchy are recognized on the actual date of the event or circumstances that caused the transfer, which generally coincides with our monthly and/or quarterly valuation process. Financial Assets and Financial Liabilities: Financial assets and financial liabilities measured at fair value on a recurring basis include the following: Securities Available for Sale . U.S. Treasury securities are reported at fair value utilizing Level 1 inputs. Other securities classified as available for sale are reported at fair value utilizing Level 2 inputs. For these securities, we obtain fair value measurements from an independent pricing service. The fair value measurements consider observable data that may include dealer quotes, market spreads, cash flows, the U.S. Treasury yield curve, live trading levels, trade execution data, market consensus prepayment speeds, credit information and the bond’s terms and conditions, among other things. We review the prices supplied by the independent pricing service, as well as their underlying pricing methodologies, for reasonableness and to ensure such prices are aligned with traditional pricing matrices. In general, we do not purchase investment portfolio securities that are esoteric or that have a complicated structure. Our entire portfolio consists of traditional investments, nearly all of which are U.S. Treasury obligations, federal agency bullet or mortgage pass-through securities, or general obligation or revenue based municipal bonds. Pricing for such instruments is fairly generic and is easily obtained. From time to time, we will validate prices supplied by the independent pricing service by comparison to prices obtained from third-party sources or derived using internal models. Trading Securities . U.S. Treasury securities and exchange-listed common stock are reported at fair value utilizing Level 1 inputs. Other securities classified as trading are reported at fair value utilizing Level 2 inputs in the same manner as described above for securities available for sale. Derivatives . Derivatives are generally reported at fair value utilizing Level 2 inputs, except for foreign currency contracts, which are reported at fair value utilizing Level 1 inputs. We obtain dealer quotations and utilize internally developed valuation models to value commodity swaps/options. We utilize internally developed valuation models and/or third-party models with observable market data inputs to validate the valuations provided by the dealers. Though there has never been a significant discrepancy in the valuations, should such a significant discrepancy arise, we would obtain price verification from a third-party dealer. We utilize internal valuation methods with observable market data inputs to estimate fair values of customer interest rate swaps, caps and floors. We also obtain dealer quotations for these derivatives for comparative purposes to assess the reasonableness of the model valuations. In cases where significant credit valuation adjustments are incorporated into the estimation of fair value, reported amounts are considered to have been derived utilizing Level 3 inputs. For purposes of potential valuation adjustments to our derivative positions, we evaluate the credit risk of our counterparties as well as ours. Accordingly, we have considered factors such as the likelihood of our default and the default of our counterparties, our net exposures and remaining contractual life, among other things, in determining if any fair value adjustments related to credit risk are required. Counterparty exposure is evaluated by netting positions that are subject to master netting arrangements, as well as considering the amount of collateral securing the position. We review our counterparty exposure on a regular basis, and, when necessary, appropriate business actions are taken to adjust the exposure. We also utilize this approach to estimate our own credit risk on derivative liability positions. To date, we have not realized any significant losses due to a counterparty’s inability to pay any net uncollateralized position. The change in value of derivative assets and derivative liabilities attributable to credit risk was not significant during the reported periods. 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 (for example, when there is evidence of impairment). Financial assets measured at fair value on a non-recurring basis during the reported periods include certain impaired loans reported at the fair value of the underlying collateral if repayment is expected solely from the collateral. Collateral values are estimated using Level 2 inputs based on observable market data, typically in the case of real estate collateral, or Level 3 inputs based on customized discounting criteria, typically in the case of non-real estate collateral such as inventory, oil and gas reserves, accounts receivable, equipment or other business assets. 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. Such fair value measurements were not significant during the reported periods. Charge-offs recognized upon loan foreclosures are generally offset by general or specific allocations of the allowance for credit losses on loans and generally do not, and did not during the reported periods, significantly impact our credit loss expense. Regulatory guidelines require us to reevaluate the fair value of other real estate owned on at least an annual basis. While our policy is to comply with the regulatory guidelines, our general practice is to reevaluate the fair value of collateral supporting impaired collateral dependent loans on a quarterly basis. Thus, appraisals are generally not considered to be outdated, and we typically do not make any adjustments to the appraised values. ASC Topic 825, “Financial Instruments,” requires disclosure of the fair value of financial assets and financial liabilities, including those financial assets and financial liabilities that are not measured and reported at fair value on a recurring basis or non-recurring basis. The estimated fair value approximates carrying value for cash and cash equivalents, accrued interest and the cash surrender value of life insurance policies. The methodologies for other financial assets and financial liabilities that are not measured and reported at fair value on a recurring basis or non-recurring basis are discussed below: Loans . The estimated fair value approximates carrying value for variable-rate loans that reprice frequently and with no significant change in credit risk. The fair value of fixed-rate loans and variable-rate loans which reprice on an infrequent basis is estimated by discounting future cash flows using the current interest rates at which similar loans with similar terms would be made to borrowers of similar credit quality. An overall valuation adjustment is made for specific credit risks as well as general portfolio credit risk. Deposits . The estimated fair value approximates carrying value for demand deposits. The fair value of fixed-rate deposit liabilities with defined maturities is estimated by discounting future cash flows using the interest rates currently offered for deposits of similar remaining maturities. The estimated fair value of deposits does not take into account the value of our long-term relationships with depositors, commonly known as core deposit intangibles, which are separate intangible assets, and not considered financial instruments. Nonetheless, we would likely realize a core deposit premium if our deposit portfolio were sold in the principal market for such deposits. Borrowed Funds . The estimated fair value approximates carrying value for short-term borrowings. The fair value of long-term fixed-rate borrowings is estimated using quoted market prices, if available, or by discounting future cash flows using current interest rates for similar financial instruments. The estimated fair value approximates carrying value for variable-rate junior subordinated deferrable interest debentures that reprice quarterly. Loan Commitments, Standby and Commercial Letters of Credit . Our lending commitments have variable interest rates and “escape” clauses if the customer’s credit quality deteriorates. Therefore, the fair values of these items are not significant and are not included in the following table.

Summary of Significant Accoun_3

Summary of Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2023
Accounting Policies [Abstract]
Additional Cash Flow Information	Additional cash flow information was as follows: Year Ended December 31, 2023 2022 2021 Cash paid for interest $ 616,274 $ 169,020 $ 29,003 Cash paid for income tax 118,000 100,000 39,852 Significant non-cash transactions: Exchange of real estate — — 11,036 Unsettled securities transactions 1,452 94,884 27,032 Loans foreclosed and transferred to other real estate owned and foreclosed assets — 239 3,464 Right-of-use lease assets obtained in exchange for lessee operating lease liabilities 15,259 31,787 12,854 Treasury stock issued to 401(k) stock purchase plan — — 1,749

Securities (Tables)

Securities (Tables)	12 Months Ended
	Dec. 31, 2023
Investments, Debt and Equity Securities [Abstract]
Debt 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 December 31, 2023 and 2022 is presented below. Amortized Gross Gross Estimated Allowance Net 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 December 31, 2022 Residential mortgage-backed securities $ 526,122 $ — $ 65,322 $ 460,800 $ — $ 526,122 States and political subdivisions 2,111,619 13,048 119,033 2,005,634 (158) 2,111,461 Other 1,500 — 69 1,431 — 1,500 Total $ 2,639,241 $ 13,048 $ 184,424 $ 2,467,865 $ (158) $ 2,639,083
Moody's and Standard & Poor's Bond Ratings	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 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 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	The following table details activity in the allowance for credit losses on held-to-maturity securities. 2023 2022 2021 Beginning balance $ 158 $ 158 $ 160 Credit loss expense (benefit) 152 — (2) Ending balance $ 310 $ 158 $ 158
Debt 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 December 31, 2023 and 2022 is presented below. Amortized Gross Gross Allowance Estimated 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 December 31, 2022 U.S. Treasury $ 5,450,546 $ — $ 398,959 $ — $ 5,051,587 Residential mortgage-backed securities 7,316,824 8,050 948,638 — 6,376,236 States and political subdivisions 7,098,635 9,108 334,388 — 6,773,355 Other 42,427 — — — 42,427 Total $ 19,908,432 $ 17,158 $ 1,681,985 $ — $ 18,243,605
Year End Securities with Unrealized Losses, Segregated by Length of Impairment	The table below summarizes, as of December 31, 2023, 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 $ — $ — $ 4,927,590 $ 285,305 $ 4,927,590 $ 285,305 Residential mortgage-backed securities 879,380 6,883 5,062,456 869,455 5,941,836 876,338 States and political subdivisions 1,810,373 10,035 2,652,951 230,117 4,463,324 240,152 Total $ 2,689,753 $ 16,918 $ 12,642,997 $ 1,384,877 $ 15,332,750 $ 1,401,795
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 December 31, 2023. 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 $ — $ — $ 512,995 $ 737,436 $ 1,250,431 States and political subdivisions 8,170 12,008 52,106 2,295,523 2,367,807 Other — 1,500 — — 1,500 Total $ 8,170 $ 13,508 $ 565,101 $ 3,032,959 $ 3,619,738 Estimated Fair Value Residential mortgage-backed securities $ — $ — $ 461,253 $ 735,079 $ 1,196,332 States and political subdivisions 8,175 11,999 50,728 2,263,355 2,334,257 Other — 1,455 — — 1,455 Total $ 8,175 $ 13,454 $ 511,981 $ 2,998,434 $ 3,532,044 Available For Sale Amortized Cost U. S. Treasury $ 1,534,307 $ 3,288,365 $ 197,809 $ 192,413 $ 5,212,894 Residential mortgage-backed securities 1,740 1,827 13,985 7,446,402 7,463,954 States and political subdivisions 370,259 183,228 880,659 3,811,575 5,245,721 Other — — — — 42,769 Total $ 1,906,306 $ 3,473,420 $ 1,092,453 $ 11,450,390 $ 17,965,338 Estimated Fair Value U. S. Treasury $ 1,514,227 $ 3,101,776 $ 167,219 $ 144,367 $ 4,927,589 Residential mortgage-backed securities 1,718 1,826 13,963 6,579,175 6,596,682 States and political subdivisions 370,111 182,786 859,675 3,598,759 5,011,331 Other — — — — 42,769 Total $ 1,886,056 $ 3,286,388 $ 1,040,857 $ 10,322,301 $ 16,578,371
Schedule of Realized Gain (Loss)	Sales of securities available for sale were as follows: 2023 2022 2021 Proceeds from sales $ 1,904,067 $ — $ 1,999,891 Gross realized gains 5,758 — 69 Gross realized losses (5,692) — — Tax benefit (expense) related to securities gains/losses (14) — (14)
Investment Income	Premium amortization and discount accretion included in interest income on securities was as follows: 2023 2022 2021 Premium amortization $ (85,506) $ (110,997) $ (121,994) Discount accretion 21,613 13,597 2,752 Net (premium amortization) discount accretion $ (63,893) $ (97,400) $ (119,242)
Year End Trading Account Securities, at Estimated Fair Value	Year-end trading account securities, at estimated fair value, were as follows: 2023 2022 U.S. Treasury $ 30,265 $ 25,879 States and political subdivisions 1,452 2,166 Total $ 31,717 $ 28,045
Net Gains and Losses on Trading Account Securities	Net gains and losses on trading account securities were as follows: 2023 2022 2021 Net gain on sales transactions $ 3,843 $ 3,129 $ 1,014 Net mark-to-market gains (losses) (33) (230) (75) Net gain on trading account securities $ 3,810 $ 2,899 $ 939

Loans (Tables)

Loans (Tables)	12 Months Ended
	Dec. 31, 2023
Receivables [Abstract]
Loans	Year-end loans, including leases net of unearned discounts, consisted of the following: 2023 2022 Commercial and industrial $ 5,959,133 $ 5,674,798 Energy: Production 681,568 696,570 Service 192,654 133,542 Other 61,043 95,617 Total energy 935,265 925,729 Paycheck Protection Program (“PPP”) 9,521 34,852 Commercial real estate: Commercial mortgages 6,746,709 6,168,910 Construction 1,680,724 1,477,247 Land 555,211 537,168 Total commercial real estate 8,982,644 8,183,325 Consumer real estate: Home equity lines of credit 792,876 691,841 Home equity loans 694,966 449,507 Home improvement loans 765,887 577,377 Other 206,997 124,814 Total consumer real estate 2,460,726 1,843,539 Total real estate 11,443,370 10,026,864 Consumer and other 476,962 492,726 Total loans $ 18,824,251 $ 17,154,969
Activities in Related Party Loans	Activity in related party loans during 2023 is presented in the following table. Other changes were primarily related to changes in related-party status. Balance outstanding at December 31, 2022 $ 391,255 Principal additions 322,183 Principal payments (299,338) Other changes 2,007 Balance outstanding at December 31, 2023 $ 416,107
Non-Accrual Loans, Segregated by Class of Loans	Year-end non-accrual loans, segregated by class of loans, were as follows: December 31, 2023 December 31, 2022 Total Non-Accrual Non-Accrual with No Credit Loss Allowance Total Non-Accrual Non-Accrual with No Credit Loss Allowance Commercial and industrial $ 19,545 $ 5,391 $ 18,130 $ 8,514 Energy 11,500 7,398 15,224 7,139 Commercial real estate: Buildings, land and other 22,420 4,983 3,552 1,991 Construction — — — — Consumer real estate 7,442 5,160 927 927 Consumer and other — — — — Total $ 60,907 $ 22,932 $ 37,833 $ 18,571
Financing Receivable, Non-Accrual Loans, Segregated by Class of Loan and Year of Origination	The following tables present non-accrual loans as of December 31, 2023 and December 31, 2022 by class and year of origination. December 31, 2023 2023 2022 2021 2020 2019 Prior Revolving Loans Revolving Loans Converted to Term Total Commercial and industrial $ — $ 359 $ 1,635 $ 985 $ 1,257 $ 1,006 $ 9 $ 14,294 $ 19,545 Energy 5,875 — — 56 1,321 — 4,102 146 11,500 Commercial real estate: Buildings, land and other 20,099 — 150 — 1,451 720 — — 22,420 Construction — — — — — — — — — Consumer real estate — — — 38 2,281 483 1,600 3,040 7,442 Consumer and other — — — — — — — — — Total $ 25,974 $ 359 $ 1,785 $ 1,079 $ 6,310 $ 2,209 $ 5,711 $ 17,480 $ 60,907 December 31, 2022 2022 2021 2020 2019 2018 Prior Revolving Loans Revolving Loans Converted to Term Total Commercial and industrial $ — $ 1,252 $ 1,089 $ 3,242 $ 1,197 $ 191 $ 2,973 $ 8,186 $ 18,130 Energy 4,657 — 72 1,386 10 — 7,631 1,468 15,224 Commercial real estate: Buildings, land and other 1,644 — — 217 266 1,425 — — 3,552 Construction — — — — — — — — — Consumer real estate — 258 — — — 84 — 585 927 Consumer and other — — — — — — — — — Total $ 6,301 $ 1,510 $ 1,161 $ 4,845 $ 1,473 $ 1,700 $ 10,604 $ 10,239 $ 37,833
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 December 31, 2023 is presented in the following table. Despite their past due status, PPP loans are fully guaranteed by the Small Business Administration (“SBA”). Loans Loans Total Past Current Total Loans Accruing Commercial and industrial $ 27,551 $ 21,705 $ 49,256 $ 5,909,877 $ 5,959,133 $ 5,503 Energy 6,387 6,771 13,158 922,107 935,265 1,146 Paycheck Protection Program 61 1,954 2,015 7,506 9,521 1,954 Commercial real estate: Buildings, land and other 20,224 1,610 21,834 7,280,086 7,301,920 92 Construction 4,878 3,498 8,376 1,672,348 1,680,724 3,498 Consumer real estate 12,504 7,716 20,220 2,440,506 2,460,726 2,589 Consumer and other 6,495 251 6,746 470,216 476,962 251 Total $ 78,100 $ 43,505 $ 121,605 $ 18,702,646 $ 18,824,251 $ 15,033
Modification to Borrowers Experiencing Financial Difficulty	The period-end balance of loan modifications, segregated by type of modification, to borrowers experiencing financial difficulty during 2023 and 2022 are set forth in the table below, regardless of whether such modifications resulted in a new loan. There were no commitments to lend additional funds to these borrowers at December 31, 2023. Payment Percent of Combination: Payment Delay and Term Extension Percent of Combination: Interest Rate Reduction and Term Extension Percent of December 31, 2023 Commercial and industrial $ — — % $ 13,813 0.2 % $ — — % Commercial real estate: Buildings, land, and other — — 19,438 0.3 2,092 — $ — — $ 33,251 0.2 $ 2,092 — December 31, 2022 Commercial real estate: Buildings, land, and other $ 1,051 — $ — — $ — — $ 1,051 — $ — — $ — —
Financing Receivables, Modified Loans by Type of Modification	Information as of or for the years ended December 31, 2023, 2022, or 2021 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. Payment Combination: Payment Delay and Term Extension Combination: Interest Rate Reduction and Term Extension 2023 Past due in excess of 90 days or on non-accrual status at period-end: Commercial and industrial $ — $ 13,813 $ — Commercial real estate: Buildings, land, and other — 19,438 — $ — $ 33,251 $ — 2022 Past due in excess of 90 days or on non-accrual status at period-end: Commercial real estate: Buildings, land, and other $ 1,051 $ — $ — $ 1,051 $ — $ — Charge-offs during the period: Commercial real estate: Buildings, land, and other $ 371 $ 352 $ — $ 371 $ 352 $ — Proceeds from sales: Commercial real estate: Buildings, land, and other $ — $ 1,070 $ — $ — $ 1,070 $ — 2021 Past due in excess of 90 days or on non-accrual status at period-end: Commercial and industrial $ 1,162 $ — $ — Energy 721 — — Commercial real estate: Buildings, land, and other 306 1,556 — $ 2,189 $ 1,556 $ — Charge-offs during the period: Energy $ 4,278 $ — $ — $ 4,278 $ — $ —
Weighted Average Risk Grades for All Commercial Loans by Class and Year of Origination	The following tables present weighted-average risk grades for all commercial loans, by class and year of origination/renewal as of December 31, 2023 and 2022. PPP loans are excluded as such loans are fully guaranteed by the SBA. December 31, 2023 2023 2022 2021 2020 2019 Prior Revolving Loans Revolving Loans Converted to Term Total Commercial and industrial Risk grades 1-8 $ 1,489,026 $ 706,210 $ 450,806 $ 349,744 $ 172,656 $ 206,643 $ 2,083,490 $ 41,254 $ 5,499,829 Risk grade 9 57,625 42,618 12,258 4,952 1,641 10,383 70,142 5,625 205,244 Risk grade 10 63,205 2,222 1,307 911 4,005 581 35,977 1,046 109,254 Risk grade 11 9,450 16,837 25,932 7,854 2,530 1,153 58,134 3,371 125,261 Risk grade 12 — 359 1,635 950 1,257 1,006 1 11,894 17,102 Risk grade 13 — — — 35 — — 8 2,400 2,443 $ 1,619,306 $ 768,246 $ 491,938 $ 364,446 $ 182,089 $ 219,766 $ 2,247,752 $ 65,590 $ 5,959,133 W/A risk grade 6.53 7.05 7.26 5.87 6.01 6.04 6.50 8.48 6.60 Energy Risk grades 1-8 $ 270,710 $ 54,185 $ 73,532 $ 3,673 $ 1,819 $ 4,047 $ 451,897 $ 9,886 $ 869,749 Risk grade 9 1,137 7,315 1,041 — 456 — 17,680 14 27,643 Risk grade 10 — — 33 — 291 494 — — 818 Risk grade 11 — — 25 106 2,989 — 21,650 785 25,555 Risk grade 12 5,875 — — 56 1,321 — 1,402 146 8,800 Risk grade 13 — — — — — — 2,700 — 2,700 $ 277,722 $ 61,500 $ 74,631 $ 3,835 $ 6,876 $ 4,541 $ 495,329 $ 10,831 $ 935,265 W/A risk grade 6.19 7.07 6.00 6.99 10.02 7.07 5.75 7.33 6.05 Commercial real estate: Buildings, land, other Risk grades 1-8 $ 1,601,175 $ 1,667,750 $ 1,186,559 $ 747,289 $ 503,303 $ 874,942 $ 214,874 $ 99,466 $ 6,895,358 Risk grade 9 12,173 68,007 28,870 13,250 16,272 23,214 11,143 541 173,470 Risk grade 10 7,671 29,278 17,364 34,672 747 3,153 3,716 — 96,601 Risk grade 11 4,105 20,589 20,119 16,363 793 51,739 — 363 114,071 Risk grade 12 17,449 — 150 — 1,451 720 — — 19,770 Risk grade 13 2,650 — — — — — — — 2,650 $ 1,645,223 $ 1,785,624 $ 1,253,062 $ 811,574 $ 522,566 $ 953,768 $ 229,733 $ 100,370 $ 7,301,920 W/A risk grade 7.23 7.18 7.29 7.22 6.90 7.16 7.49 6.77 7.20 Construction Risk grades 1-8 $ 538,072 $ 537,705 $ 264,770 $ 28,063 $ 296 $ 1,613 $ 155,567 $ — $ 1,526,086 Risk grade 9 3,414 35,565 79,871 — — — 8,252 — 127,102 Risk grade 10 13,322 — — — — — 3,713 — 17,035 Risk grade 11 5,912 3,104 — — — — 1,485 — 10,501 Risk grade 12 — — — — — — — — — Risk grade 13 — — — — — — — — — $ 560,720 $ 576,374 $ 344,641 $ 28,063 $ 296 $ 1,613 $ 169,017 $ — $ 1,680,724 W/A risk grade 7.44 7.44 7.93 2.55 7.22 6.78 7.34 — 7.45 Total commercial real estate $ 2,205,943 $ 2,361,998 $ 1,597,703 $ 839,637 $ 522,862 $ 955,381 $ 398,750 $ 100,370 $ 8,982,644 W/A risk grade 7.28 7.24 7.43 7.07 6.90 7.15 7.43 6.77 7.24 December 31, 2022 2022 2021 2020 2019 2018 Prior Revolving Loans Revolving Loans Converted to Term Total Commercial and industrial Risk grades 1-8 $ 1,667,274 $ 618,756 $ 485,908 $ 226,835 $ 123,768 $ 192,791 $ 2,068,891 $ 51,694 $ 5,435,917 Risk grade 9 31,275 34,950 3,651 5,400 11,006 1,014 54,856 4,040 146,192 Risk grade 10 2,294 724 845 4,713 1,341 114 23,880 3,685 37,596 Risk grade 11 2,342 1,357 6,720 1,807 1,229 1,644 19,582 2,282 36,963 Risk grade 12 — 1,052 866 2,972 1,177 191 673 5,590 12,521 Risk grade 13 — 200 223 270 20 — 2,300 2,596 5,609 $ 1,703,185 $ 657,039 $ 498,213 $ 241,997 $ 138,541 $ 195,754 $ 2,170,182 $ 69,887 $ 5,674,798 W/A risk grade 6.37 7.05 6.01 6.59 6.87 5.55 6.26 7.68 6.39 Energy Risk grades 1-8 $ 338,050 $ 99,089 $ 4,917 $ 3,138 $ 2,020 $ 2,850 $ 393,957 $ 43,161 $ 887,182 Risk grade 9 1,561 1,611 166 562 748 — 6,434 30 11,112 Risk grade 10 — — — 428 214 — — — 642 Risk grade 11 7,956 162 157 3,145 86 63 — — 11,569 Risk grade 12 3,995 — 72 1,386 10 — 4,571 806 10,840 Risk grade 13 662 — — — — — 3,060 662 4,384 $ 352,224 $ 100,862 $ 5,312 $ 8,659 $ 3,078 $ 2,913 $ 408,022 $ 44,659 $ 925,729 W/A risk grade 6.09 5.65 7.65 9.64 8.02 6.59 5.18 5.69 5.67 Commercial real estate: Buildings, land, other Risk grades 1-8 $ 1,811,069 $ 1,484,811 $ 956,567 $ 708,942 $ 360,154 $ 800,944 $ 111,778 $ 105,763 $ 6,340,028 Risk grade 9 52,288 13,139 36,264 22,086 17,699 45,590 652 2,210 189,928 Risk grade 10 26,688 11,150 3,735 9,008 29,683 5,221 5,535 — 91,020 Risk grade 11 10,199 19,073 12,631 4,778 2,525 28,841 2,993 510 81,550 Risk grade 12 1,049 — — 217 266 1,425 — — 2,957 Risk grade 13 595 — — — — — — — 595 $ 1,901,888 $ 1,528,173 $ 1,009,197 $ 745,031 $ 410,327 $ 882,021 $ 120,958 $ 108,483 $ 6,706,078 W/A risk grade 7.01 7.26 7.14 7.01 7.33 6.94 7.38 6.43 7.09 Construction Risk grades 1-8 $ 640,948 $ 489,391 $ 128,788 $ 2,236 $ 486 $ 1,726 $ 163,293 $ 3,144 $ 1,430,012 Risk grade 9 12,865 2,100 2,100 — — — 17,887 — 34,952 Risk grade 10 859 72 — — — — — — 931 Risk grade 11 11,352 — — — — — — — 11,352 Risk grade 12 — — — — — — — — — Risk grade 13 — — — — — — — — — $ 666,024 $ 491,563 $ 130,888 $ 2,236 $ 486 $ 1,726 $ 181,180 $ 3,144 $ 1,477,247 W/A risk grade 7.29 7.03 6.43 7.04 6.00 6.76 7.23 5.03 7.12 Total commercial real estate $ 2,567,912 $ 2,019,736 $ 1,140,085 $ 747,267 $ 410,813 $ 883,747 $ 302,138 $ 111,627 $ 8,183,325 W/A risk grade 7.08 7.20 7.06 7.01 7.33 6.94 7.29 6.39 7.10
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 December 31, 2023 and December 31, 2022 was as follows: December 31, 2023 2023 2022 2021 2020 2019 Prior Revolving Loans Revolving Loans Converted to Term Total Consumer real estate: Past due 30-89 days $ 874 $ 2,066 $ 1,318 $ 959 $ 537 $ 2,641 $ 3,570 $ 539 $ 12,504 Past due 90 or more days — 512 626 38 — 887 2,566 3,087 7,716 Total past due 874 2,578 1,944 997 537 3,528 6,136 3,626 20,220 Current loans 579,505 432,719 281,820 170,225 58,744 134,319 775,465 7,709 2,440,506 Total $ 580,379 $ 435,297 $ 283,764 $ 171,222 $ 59,281 $ 137,847 $ 781,601 $ 11,335 $ 2,460,726 Consumer and other: Past due 30-89 days $ 3,014 $ 488 $ 148 $ 66 $ 28 $ 40 $ 2,553 $ 158 $ 6,495 Past due 90 or more days 153 — 27 — 20 — 51 — 251 Total past due 3,167 488 175 66 48 40 2,604 158 6,746 Current loans 67,272 28,885 6,290 3,581 1,199 1,230 339,789 21,970 470,216 Total $ 70,439 $ 29,373 $ 6,465 $ 3,647 $ 1,247 $ 1,270 $ 342,393 $ 22,128 $ 476,962 December 31, 2022 2022 2021 2020 2019 2018 Prior Revolving Loans Revolving Loans Converted to Term Total Consumer real estate: Past due 30-89 days $ 793 $ 1,125 $ 645 $ 936 $ 503 $ 2,087 $ 565 $ 1,202 $ 7,856 Past due 90 or more days 95 258 28 — 129 919 347 914 2,690 Total past due 888 1,383 673 936 632 3,006 912 2,116 10,546 Current loans 403,587 313,222 194,900 70,723 38,904 122,585 678,418 10,654 1,832,993 Total $ 404,475 $ 314,605 $ 195,573 $ 71,659 $ 39,536 $ 125,591 $ 679,330 $ 12,770 $ 1,843,539 Consumer and other: Past due 30-89 days $ 2,673 $ 511 $ 128 $ 51 $ 4 $ 31 $ 314 $ 1,443 $ 5,155 Past due 90 or more days 77 2 — 13 — — 25 194 311 Total past due 2,750 513 128 64 4 31 339 1,637 5,466 Current loans 59,886 20,887 6,475 2,897 1,271 1,632 372,117 22,095 487,260 Total $ 62,636 $ 21,400 $ 6,603 $ 2,961 $ 1,275 $ 1,663 $ 372,456 $ 23,732 $ 492,726
Financing Receivable Revolving Loans Converted to Term	Revolving loans that converted to term during 2023 and 2022 were as follows: 2023 2022 Commercial and industrial $ 28,713 $ 34,247 Energy 6,409 3,295 Commercial real estate: Buildings, land and other 4,780 12,174 Construction — 3,144 Consumer real estate 2,467 5,381 Consumer and other 7,482 9,200 Total $ 49,851 $ 67,441
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 December 31, 2023 and 2022, calculated in accordance with the CECL methodology described above. No allowance for credit losses has been recognized for PPP loans as such loans are fully guaranteed by the SBA. Commercial Energy Commercial Consumer Consumer Total 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 December 31, 2022 Modeled expected credit losses $ 61,918 $ 8,531 $ 27,013 $ 7,847 $ 4,983 $ 110,292 Q-Factor and other qualitative adjustments 36,237 5,148 61,572 157 2,034 105,148 Specific allocations 6,082 4,383 1,716 — — 12,181 Total $ 104,237 $ 18,062 $ 90,301 $ 8,004 $ 7,017 $ 227,621
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 2023, 2022 and 2021. Allocation of a portion of the allowance to one category of loans does not preclude its availability to absorb losses in other categories. No allowance for credit losses has been recognized for PPP loans as such loans are fully guaranteed by the SBA. Commercial Energy Commercial Consumer Consumer Total 2023 Beginning balance $ 104,237 $ 18,062 $ 90,301 $ 8,004 $ 7,017 $ 227,621 Credit loss expense (benefit) (16,709) (1,067) 40,889 6,736 23,012 52,861 Charge-offs (18,315) (518) (955) (2,883) (31,260) (53,931) Recoveries 4,793 1,337 363 1,681 11,271 19,445 Net (charge-offs) recoveries (13,522) 819 (592) (1,202) (19,989) (34,486) Ending balance $ 74,006 $ 17,814 $ 130,598 $ 13,538 $ 10,040 $ 245,996 2022 Beginning balance $ 72,091 $ 17,217 $ 144,936 $ 6,585 $ 7,837 $ 248,666 Credit loss expense (benefit) 34,479 (313) (54,775) 1,813 13,517 (5,279) Charge-offs (6,575) (371) (702) (912) (24,388) (32,948) Recoveries 4,242 1,529 842 518 10,051 17,182 Net (charge-offs) recoveries (2,333) 1,158 140 (394) (14,337) (15,766) Ending balance $ 104,237 $ 18,062 $ 90,301 $ 8,004 $ 7,017 $ 227,621 2021 Beginning balance $ 73,843 $ 39,553 $ 134,892 $ 7,926 $ 6,963 $ 263,177 Credit loss expense (benefit) (2,160) (19,207) 8,101 (3,061) 10,230 (6,097) Charge-offs (5,513) (5,331) (399) (829) (18,614) (30,686) Recoveries 5,921 2,202 2,342 2,549 9,258 22,272 Net (charge-offs) recoveries 408 (3,129) 1,943 1,720 (9,356) (8,414) Ending balance $ 72,091 $ 17,217 $ 144,936 $ 6,585 $ 7,837 $ 248,666
Gross Charge-Offs By Year of Origination [Table]	The following table presents year-to-date gross charge-offs by year of origination as of December 31, 2023. 2023 2022 2021 2020 2019 Prior Revolving Loans Revolving Loans Converted to Term Total Commercial and industrial $ 124 $ 1,704 $ 754 $ 157 $ 183 $ 38 $ 9,511 $ 5,844 $ 18,315 Energy — — — — — — — 518 518 Commercial real estate: Buildings, land and other — 6 146 — — 64 — — 216 Construction 739 — — — — — — — 739 Consumer real estate 118 281 348 — — 329 1,807 — 2,883 Consumer and other 23,321 4,546 74 13 1 29 2,766 510 31,260 Total $ 24,302 $ 6,537 $ 1,322 $ 170 $ 184 $ 460 $ 14,084 $ 6,872 $ 53,931 In the table above, $23.1 million of the consumer and other loan charge-offs reported as 2023 originations and $4.2 million of the total reported as 2022 originations were related to deposit overdrafts.
Investment in Loans Related to the 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 December 31, 2023 and December 31, 2022. December 31, 2023 December 31, 2022 Loan Specific Allocations Loan Specific Allocations Commercial and industrial $ 18,670 $ 2,435 $ 18,980 $ 6,082 Energy 11,353 2,700 15,058 4,383 Paycheck Protection Program — — — — Commercial real estate: Buildings, land and other 21,373 2,650 17,711 1,716 Construction — — — — Consumer real estate 7,235 741 827 — Consumer and other — — — — Total $ 58,631 $ 8,526 $ 52,576 $ 12,181

Premises and Equipment (Tables)

Premises and Equipment (Tables)	12 Months Ended
	Dec. 31, 2023
Property, Plant and Equipment [Abstract]
Premises and Equipment	Year-end premises and equipment were as follows: 2023 2022 Land $ 191,594 $ 170,938 Buildings 581,745 521,280 Technology, furniture and equipment 262,666 236,440 Leasehold improvements 230,642 209,398 Construction and projects in progress 36,910 39,506 Lease right-of-use assets 280,502 288,816 1,584,059 1,466,378 Less accumulated depreciation and amortization (394,026) (363,683) Total premises and equipment, net $ 1,190,033 $ 1,102,695
Lease Commitments, Components of Lease Expense	The components of total lease expense in 2023 and 2022 were as follows: 2023 2022 Amortization of lease right-of-use assets $ 34,137 $ 33,285 Short-term lease expense 2,576 2,208 Non-lease components (including taxes, insurance, common maintenance, etc.) 13,811 12,172 Total $ 50,524 $ 47,665
Lessee, Operating Lease, Liability, Maturity	The following table reconciles future undiscounted lease payments due under non-cancelable operating leases (those amounts subject to recognition) to the aggregate operating lessee lease liability as of December 31, 2023: Future lease payments 2024 $ 34,712 2025 36,030 2026 35,891 2027 34,359 2028 32,319 Thereafter 218,152 Total undiscounted operating lease liability 391,463 Imputed interest 75,071 Total operating lease liability included in the accompanying balance sheet $ 316,392 Weighted-average lease term in years 12.88 Weighted-average discount rate 3.32%

Deposits (Tables)

Deposits (Tables)	12 Months Ended
	Dec. 31, 2023
Deposits [Abstract]
Deposit Liabilities, Type	Year-end deposits were as follows: 2023 2022 Non-interest-bearing demand deposits $ 14,926,094 $ 17,598,234 Interest-bearing deposits: Savings and interest checking 10,512,637 12,333,675 Money market accounts 10,997,279 12,227,247 Time accounts 5,484,558 1,795,040 Total interest-bearing deposits 26,994,474 26,355,962 Total deposits $ 41,920,568 $ 43,954,196
Additional Information About Corporation's Deposits	The following table presents additional information about our year-end deposits: 2023 2022 Deposits from foreign sources (primarily Mexico) $ 1,061,701 $ 1,048,943 Non-interest-bearing public funds deposits 675,016 788,040 Interest-bearing public funds deposits 630,455 758,761 Total deposits not covered by deposit insurance 22,393,786 23,839,797 Time deposits not covered by deposit insurance 2,339,716 430,128 Deposits from certain directors, executive officers and their affiliates 115,798 153,083
Scheduled Maturities of Time Deposits	Scheduled maturities of time deposits at December 31, 2023 were as follows: 2024 $ 5,286,064 2025 28,829 2026 169,665 $ 5,484,558
Time Deposit Maturities	Scheduled maturities of time deposits not covered by deposit insurance at December 31, 2023, were as follows: Due within 3 months or less $ 1,991,080 Due after 3 months and within 6 months 139,435 Due after 6 months and within 12 months 167,732 Due after 12 months 41,469 $ 2,339,716

Off-Balance-Sheet Arrangement_2

Off-Balance-Sheet Arrangements, Commitments, Guarantees and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2023
Commitments and Contingencies Disclosure [Abstract]
Financial Instruments With Off-Balance-Sheet Risk	Year-end financial instruments with off-balance-sheet risk are presented in the following table. Commitments and standby letters of credit are presented at contractual amounts; however, since many of these commitments are expected to expire unused or only partially used, the total amounts of these commitments do not necessarily reflect future cash requirements. 2023 2022 Commitments to extend credit $ 12,195,073 $ 12,137,957 Standby letters of credit 438,635 383,851 Deferred standby letter of credit fees 2,912 2,236
Commitments, Off-Balance-Sheet, Allowance for Credit Losses	The following table details activity in the allowance for credit losses on off-balance-sheet credit exposures. 2023 2022 2021 Beginning balance $ 58,593 $ 50,314 $ 44,152 Credit loss expense (benefit) (6,842) 8,279 6,162 Ending balance $ 51,751 $ 58,593 $ 50,314

Capital and Regulatory Matters

Capital and Regulatory Matters (Tables)	12 Months Ended
	Dec. 31, 2023
Broker-Dealer, Net Capital Requirement, SEC Regulation [Abstract]
Actual and Required Capital Ratios	The following table presents actual and required capital ratios as of December 31, 2023 and December 31, 2022 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. Actual Minimum Capital Required to be Considered Well Capitalized (1) Capital Ratio Capital Ratio Capital Ratio 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 2022 Common Equity Tier 1 to Risk-Weighted Assets Cullen/Frost $ 3,751,200 12.85 % $ 2,042,876 7.00 % N/A N/A Frost Bank 3,789,056 13.00 2,040,388 7.00 $ 1,894,646 6.50 % Tier 1 Capital to Risk-Weighted Assets Cullen/Frost 3,896,652 13.35 2,480,635 8.50 1,751,036 6.00 Frost Bank 3,789,056 13.00 2,477,614 8.50 2,331,872 8.00 Total Capital to Risk-Weighted Assets Cullen/Frost 4,330,982 14.84 3,064,313 10.50 2,918,394 10.00 Frost Bank 4,023,386 13.80 3,060,583 10.50 2,914,841 10.00 Leverage Ratio Cullen/Frost 3,896,652 7.29 2,136,680 4.00 N/A N/A Frost Bank 3,789,056 7.09 2,136,316 4.00 2,670,395 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.

Earnings Per Common Share (Tabl

Earnings Per Common Share (Tables)	12 Months Ended
	Dec. 31, 2023
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. 2023 2022 2021 Net Income $ 597,973 $ 579,150 $ 443,079 Less: Preferred stock dividends 6,675 6,675 7,157 Net income available to common shareholders 591,298 572,475 435,922 Less: Earnings allocated to participating securities 6,283 5,210 3,881 Net earnings allocated to common stock $ 585,015 $ 567,265 $ 432,041 Distributed earnings allocated to common stock $ 229,749 $ 207,924 $ 187,202 Undistributed earnings allocated to common stock 355,266 359,341 244,839 Net earnings allocated to common stock $ 585,015 $ 567,265 $ 432,041 Weighted-average shares outstanding for basic earnings per common share 64,204,239 64,156,870 63,612,658 Dilutive effect of stock compensation 200,594 363,648 489,462 Weighted-average shares outstanding for diluted earnings per common share 64,404,833 64,520,518 64,102,120

Employee Benefit Plans (Tables)

Employee Benefit Plans (Tables)	12 Months Ended
	Dec. 31, 2023
Retirement Benefits [Abstract]
Combined Activity in Corporations Defined Benefit Pension Plans	We use a December 31 measurement date for our defined benefit plans. Combined activity in our defined benefit pension plans was as follows: 2023 2022 2021 Change in plan assets: Fair value of plan assets at beginning of year $ 161,823 $ 197,747 $ 182,088 Actual return on plan assets 22,477 (26,108) 24,908 Employer contributions 1,105 1,114 1,236 Benefits paid (10,794) (10,930) (10,485) Fair value of plan assets at end of year 174,611 161,823 197,747 Change in benefit obligation: Benefit obligation at beginning of year 143,944 185,925 197,593 Interest cost 6,983 4,017 3,341 Actuarial (gain) loss 2,239 (35,068) (4,524) Benefits paid (10,794) (10,930) (10,485) Benefit obligation at end of year 142,372 143,944 185,925 Funded status of the plan at end of year and accrued benefit (liability) recognized $ 32,239 $ 17,879 $ 11,822 Accumulated benefit obligation at end of year $ 142,372 $ 143,944 $ 185,925
Disaggregated Information Related to Corporations Defined Benefit Pension Plans	Certain disaggregated information related to our defined benefit pension plans as of year-end was as follows: Retirement Plan Restoration Plan 2023 2022 2023 2022 Projected benefit obligation $ 130,750 $ 131,648 $ 11,622 $ 12,296 Accumulated benefit obligation 130,750 131,648 11,622 12,296 Fair value of plan assets 174,611 161,823 — — Funded status of the plan at end of year and accrued benefit (liability) recognized 43,861 30,175 (11,622) (12,296)
Net Periodic Benefit Cost (Benefit)	The components of the combined net periodic cost (benefit) for our defined benefit pension plans are presented in the table below. 2023 2022 2021 Expected return on plan assets, net of expenses $ (10,959) $ (13,966) $ (12,839) Interest cost on projected benefit obligation 6,983 4,017 3,341 Net amortization and deferral 3,479 2,964 6,116 Net periodic expense (benefit) $ (497) $ (6,985) $ (3,382)
Defined Benefit Pension Plans Recognized as Component of Other Comprehensive Income	Amounts related to our defined benefit pension plans recognized as a component of other comprehensive income were as follows: 2023 2022 2021 Net actuarial gain (loss) $ 12,757 $ (2,041) $ 22,709 Deferred tax (expense) benefit (2,679) 429 (4,769) Other comprehensive income (loss), net of tax $ 10,078 $ (1,612) $ 17,940
Defined Benefit Pension Plans Not Recognized as Component of Combined Net Period Benefit Cost	Amounts recognized as a component of accumulated other comprehensive loss as of year-end that have not been recognized as a component of the combined net periodic benefit cost of our defined benefit pension plans are presented in the following table. 2023 2022 Net actuarial loss $ (30,918) $ (43,675) Deferred tax benefit 6,493 9,172 Amounts included in accumulated other comprehensive income/loss, net of tax (24,425) (34,503)
Weighted-Average Assumptions Used to Determine Benefit Obligations	The weighted-average assumptions used to determine the benefit obligations as of the end of the years indicated and the net periodic benefit cost for the years indicated are presented in the table below. Because the plans were frozen, increases in compensation are not considered after 2001. 2023 2022 2021 Benefit obligations: Discount rate 4.95 % 5.14 % 2.79 % Net periodic benefit cost: Discount rate 5.14 % 2.79 % 2.43 % Expected return on plan assets 7.00 7.25 7.25
Fair Value of Plan Assets	The major categories of assets in our Retirement Plan as of year-end are presented in the following table. Assets are segregated by the level of the valuation inputs within the fair value hierarchy established by ASC Topic 820 “Fair Value Measurements and Disclosures,” utilized to measure fair value (see Note 16 - Fair Value Measurements). Our Restoration Plan is unfunded. 2023 2022 Level 1: Mutual funds and ETFs $ 38,793 $ 154,391 U.S. Treasury 26,633 — Common stock 13,001 — Cash and cash equivalents 1,241 7,432 Level 2: Corporate bonds and notes 58,669 — U.S. government agency securities 7,041 — States and political subdivisions 29,233 — Total fair value of plan assets $ 174,611 $ 161,823
Expected Future Benefit Payments Related to Defined Benefit Plans	As of December 31, 2023, expected future benefit payments related to our defined benefit plans were as follows: 2024 $ 12,022 2025 11,966 2026 11,967 2027 11,874 2028 11,511 2029 through 2033 50,461 $ 109,801
Disclosure of Share-based Compensation Arrangements by Share-based Payment Award [Table Text Block]	A combined summary of activity in our active stock plans is presented in the table. Performance stock units outstanding are presented assuming attainment of the maximum payout rate as set forth by the performance criteria. The target award level for performance stock units granted in 2023, 2022 and 2021 was 66,471, 35,015 and 30,723, respectively. As of December 31, 2023, there were 205,090 shares remaining available for grant for future awards. Director Deferred Non-Vested Performance Stock Units Outstanding Stock Options Number of Units Weighted- Number Weighted- Number of Units Weighted- Number Weighted- January 1, 2020 52,860 $ 75.47 470,359 $ 86.24 201,257 $ 77.18 1,739,559 $ 66.11 Granted 5,940 117.90 95,258 130.36 46,086 121.46 — — Exercised/vested (2,499) 92.03 (88,250) 98.90 (35,131) 92.27 (861,878) 63.14 Forfeited/expired — — (28,030) 87.08 (9,752) 75.70 — — December 31, 2021 56,301 79.21 449,337 93.05 202,460 84.71 877,681 69.02 Granted 5,382 133.67 119,176 142.56 52,527 133.40 — — Exercised/vested (16,022) 74.89 (97,154) 94.81 (25,180) 87.18 (261,454) 63.72 Forfeited/expired — — (6,040) 93.28 (16,058) 87.18 — — December 31, 2022 45,661 87.15 465,319 105.36 213,749 96.20 616,227 71.27 Granted 8,503 103.47 217,561 85.39 99,710 74.71 — — Exercised/vested — — (108,920) 94.00 (28,151) 85.74 (130,286) 71.37 Forfeited/expired — — (7,154) 114.53 (18,254) 85.74 — — December 31, 2023 54,164 89.71 566,806 99.77 267,054 89.99 485,941 71.25
Options Outstanding and Exercisable	Other information regarding options outstanding and exercisable as of December 31, 2023 is as follows: Options Outstanding Options Exercisable Range of Number Weighted- Weighted- Number Weighted- $ 65.01 to $ 70.00 270,031 $ 65.11 1.80 270,031 $ 65.11 75.01 to 80.00 215,910 78.92 0.82 215,910 78.92 Total 485,941 71.25 1.37 485,941 71.25 Total intrinsic value $ 18,098 $ 18,098
Shares Issued in Connection With Stock Compensation Awards	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: 2023 2022 2021 New shares issued from available authorized shares 49,887 118,389 — Shares issued from available treasury stock 217,470 281,421 987,758 Total 267,357 399,810 987,758 Proceeds from stock option exercises $ 9,299 $ 16,659 $ 54,417 Intrinsic value of stock options exercised 3,614 19,616 43,904 Fair value of restricted/director deferred stock units vested 13,445 19,308 15,751
Stock-Based Compensation Expense	Stock-based compensation expense 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. 2023 2022 2021 Non-vested restricted stock units $ 16,734 $ 13,162 $ 9,977 Director deferred stock units 880 720 700 Performance stock units 6,976 4,440 2,076 Total $ 24,590 $ 18,322 $ 12,753 Income tax benefit $ 4,120 $ 2,969 $ 1,713
Unrecognized Stock-Based Compensation Expense	Unrecognized stock-based compensation expense and the weighted-average period over which the expense is expected to be recognized at December 31, 2023 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. Unrecognized Expense Weighted-Average Number of Years for Expense Recognition Non-vested restricted stock units $ 22,665 2.13 Performance stock units 9,784 2.25 Total $ 32,449

Other Non-Interest Income and_2

Other Non-Interest Income and Expense (Tables)	12 Months Ended
	Dec. 31, 2023
Other Income and Expenses [Abstract]
Other Non-Interest Income and Expense	Other non-interest income and expense totals are presented in the following table. Components of these totals exceeding 1% of the aggregate of total net interest income and total non-interest income for any of the years presented are stated separately. 2023 2022 2021 Other non-interest income: Other $ 54,941 $ 45,217 $ 48,528 Total $ 54,941 $ 45,217 $ 48,528 Other non-interest expense: Professional services $ 53,932 $ 40,908 $ 34,747 Advertising, promotions and public relations 48,608 39,994 34,539 Other 126,827 113,799 102,868 Total $ 229,367 $ 194,701 $ 172,154

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2023
Income Tax Disclosure [Abstract]
Income Tax Expense	Income tax expense was as follows: 2023 2022 2021 Current income tax expense $ 129,229 $ 94,595 $ 38,675 Deferred income tax expense (benefit) (14,829) (4,918) 7,784 Income tax expense, as reported $ 114,400 $ 89,677 $ 46,459 Effective tax rate 16.1 % 13.4 % 9.5 %
Income Tax Computed by Applying U.S. Federal Statutory Income Tax Rate	A reconciliation between reported income tax expense and the amounts computed by applying the U.S. federal statutory income tax rate of 21% to income before income taxes is presented in the following table. 2023 2022 2021 Income tax expense computed at the statutory rate $ 149,598 $ 140,454 $ 102,803 Effect of tax-exempt interest (43,114) (50,602) (50,740) Tax benefit on dividends paid in our 401k plan (2,135) (1,854) (1,764) Net tax benefit from stock-based compensation (894) (4,602) (7,877) Non-deductible FDIC premiums 5,263 3,277 2,629 Non-deductible compensation 2,591 2,250 1,773 Non-deductible meals and entertainment 1,692 683 625 Tax basis adjustment of premises and equipment — — (1,026) Other 1,399 71 36 Income tax expense, as reported $ 114,400 $ 89,677 $ 46,459
Schedule of Deferred Tax Assets and Liabilities	Year-end deferred taxes are presented in the table below. Deferred taxes are based on the U.S. statutory federal income tax rate of 21%. 2023 2022 Deferred tax assets: Net unrealized loss on securities available for sale and transferred securities $ 291,023 $ 349,237 Lease liabilities under operating leases 66,442 67,608 Allowance for credit losses 62,592 60,137 Bonus accrual 9,680 11,204 FDIC deposit insurance special assessment 9,468 — Stock-based compensation 7,712 6,622 Net actuarial loss on defined benefit post-retirement benefit plans 6,493 9,172 Deferred loan and lease origination fees 4,129 3,675 Other 5,892 6,109 Total gross deferred tax assets 463,431 513,764 Deferred tax liabilities: Right-of-use assets under operating leases (58,905) (60,651) Premises and equipment (42,640) (45,647) Intangible assets (18,106) (17,732) Defined benefit post-retirement benefit plans (13,073) (12,730) Other (2,368) (2,601) Total gross deferred tax liabilities (135,092) (139,361) Net deferred tax asset (liability) $ 328,339 $ 374,403

Other Comprehensive Income (L_2

Other Comprehensive Income (Loss) (Tables)	12 Months Ended
	Dec. 31, 2023
Equity [Abstract]
Component of Other Comprehensive Income (Loss)	The tax effects allocated to each component of other comprehensive income (loss) were as follows: Before Tax Tax Expense, Net of Tax 2023 Securities available for sale and transferred securities: Change in net unrealized gain/loss during the period $ 277,926 $ 58,364 $ 219,562 Change in net unrealized gain on securities transferred to held to maturity (649) (136) (513) Reclassification adjustment for net (gains) losses included in net income (66) (14) (52) Total securities available for sale and transferred securities 277,211 58,214 218,997 Defined-benefit post-retirement benefit plans: Change in the net actuarial gain/loss 9,278 1,948 7,330 Reclassification adjustment for net amortization of actuarial gain/loss included in net income as a component of net periodic cost (benefit) 3,479 731 2,748 Total defined-benefit post-retirement benefit plans 12,757 2,679 10,078 Total other comprehensive income (loss) $ 289,968 $ 60,893 $ 229,075 Before Tax Tax Expense, Net of Tax 2022 Securities available for sale and transferred securities: Change in net unrealized gain/loss during the period $ (2,143,567) $ (450,149) $ (1,693,418) Change in net unrealized gain on securities transferred to held to maturity (737) (155) (582) Total securities available for sale and transferred securities (2,144,304) (450,304) (1,694,000) Defined-benefit post-retirement benefit plans: Change in the net actuarial gain/loss (5,005) (1,051) (3,954) Reclassification adjustment for net amortization of actuarial gain/loss included in net income as a component of net periodic cost (benefit) 2,964 622 2,342 Total defined-benefit post-retirement benefit plans (2,041) (429) (1,612) Total other comprehensive income (loss) $ (2,146,345) $ (450,733) $ (1,695,612) 2021 Securities available for sale and transferred securities: Change in net unrealized gain/loss during the period $ (231,355) $ (48,585) $ (182,770) Change in net unrealized gain on securities transferred to held to maturity (971) (204) (767) Reclassification adjustment for net (gains) losses included in net income (69) (14) (55) Total securities available for sale and transferred securities (232,395) (48,803) (183,592) Defined-benefit post-retirement benefit plans: Change in the net actuarial gain/loss 16,593 3,485 13,108 Reclassification adjustment for net amortization of actuarial gain/loss included in net income as a component of net periodic cost (benefit) 6,116 1,284 4,832 Total defined-benefit post-retirement benefit plans 22,709 4,769 17,940 Total other comprehensive income (loss) $ (209,686) $ (44,034) $ (165,652)
Schedule of Accumulated Other Comprehensive Income, Net of Tax	Activity in accumulated other comprehensive income, net of tax, was as follows: Securities Defined Accumulated Balance January 1, 2023 $ (1,313,791) $ (34,503) $ (1,348,294) Other comprehensive income (loss) before reclassification 219,049 7,330 226,379 Reclassification of amounts included in net income (52) 2,748 2,696 Net other comprehensive income (loss) during period 218,997 10,078 229,075 Balance December 31, 2023 $ (1,094,794) $ (24,425) $ (1,119,219) Balance January 1, 2022 $ 380,209 $ (32,891) $ 347,318 Other comprehensive income (loss) before reclassification (1,694,000) (3,954) (1,697,954) Reclassification of amounts included in net income — 2,342 2,342 Net other comprehensive income (loss) during period (1,694,000) (1,612) (1,695,612) Balance December 31, 2022 $ (1,313,791) $ (34,503) $ (1,348,294) Balance January 1, 2021 $ 563,801 $ (50,831) $ 512,970 Other comprehensive income (loss) before reclassification (183,537) 13,108 (170,429) Reclassification of amounts included in net income (55) 4,832 4,777 Net other comprehensive income (loss) during period (183,592) 17,940 (165,652) Balance December 31, 2021 $ 380,209 $ (32,891) $ 347,318

Derivative Financial Instrume_2

Derivative Financial Instruments (Tables)	12 Months Ended
	Dec. 31, 2023
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 outstanding at December 31, 2023 and 2022 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 December 31, 2023 and 2022. December 31, 2023 December 31, 2022 Notional Estimated Notional Estimated Derivatives designated as hedges of fair value: Financial institution counterparties: Loan/lease interest rate swaps - assets $ — $ — $ 1,614 $ 19 Non-hedging interest rate derivatives: Financial institution counterparties: Loan/lease interest rate swaps - assets 1,040,659 58,486 1,165,812 70,416 Loan/lease interest rate swaps - liabilities 617,266 (20,293) 78,798 (1,102) Loan/lease interest rate caps - assets 275,000 11,747 246,442 15,256 Customer counterparties: Loan/lease interest rate swaps - assets 617,266 20,482 53,570 1,102 Loan/lease interest rate swaps - liabilities 1,040,659 (58,485) 1,175,563 (79,175) Loan/lease interest rate caps - liabilities 275,000 (11,747) 246,442 (15,256)
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 December 31, 2023 were as follows: Weighted-Average Interest Interest Interest rate swaps: Non-hedging interest rate swaps - financial institution counterparties 4.72 % 5.22 % Non-hedging interest rate swaps - customer counterparties 5.22 4.72
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. December 31, 2023 December 31, 2022 Notional Notional Estimated Notional Estimated Financial institution counterparties: Oil - assets Barrels 5,601 $ 37,667 4,024 $ 27,082 Oil - liabilities Barrels 4,581 (18,500) 6,068 (53,579) Natural gas - assets MMBTUs 17,363 11,822 16,539 6,220 Natural gas - liabilities MMBTUs 6,462 (2,499) 15,682 (19,138) Customer counterparties: Oil - assets Barrels 4,618 $ 18,722 6,068 $ 54,219 Oil - liabilities Barrels 5,564 (36,877) 4,024 (26,551) Natural gas - assets MMBTUs 6,462 2,499 15,682 19,164 Natural gas - liabilities MMBTUs 17,363 (11,571) 16,539 (6,124)
Schedule of Foreign Exchange Contracts, Statement of Financial Position	The notional amounts and fair values of open foreign currency forward contracts were as follows: December 31, 2023 December 31, 2022 Notional Notional Estimated Notional Estimated Financial institution counterparties: Forward/option contracts - assets EUR — $ — 875 $ 1 Forward/option contracts - assets CAD 250 1 — — Forward/option contracts - liabilities EUR 3,000 (14) 875 (10) Forward contracts - liabilities CAD 250 (5) — — Customer counterparties: Forward/option contracts - assets EUR 3,000 16 875 10 Forward/option contracts - assets CAD 250 5 — — Forward contracts - liabilities EUR — — 875 (1) Forward contracts - liabilities CAD 250 — — —
Schedule of Amounts Included in Income 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: 2023 2022 2021 Commercial loan/lease interest rate swaps: Amount of gain (loss) included in interest income on loans $ 16 $ (7) $ (91) Amount of (gain) loss included in other non-interest expense — 6 10
Schedule of Amounts Related to Non-Hedging Interest Rate and Commodity Derivatives	Amounts included in the consolidated statements of income related to non-hedging interest rate, commodity, foreign currency and other derivative instruments are presented in the table below. 2023 2022 2021 Non-hedging interest rate derivatives: Other non-interest income $ 6,982 $ 1,742 $ 4,285 Other non-interest expense — — (1) Non-hedging commodity derivatives: Other non-interest income 1,889 2,297 4,052 Non-hedging foreign currency derivatives: Other non-interest income 30 63 39

Balance Sheet Offsetting Balanc

Balance Sheet Offsetting Balance Sheet Offsetting (Tables)	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
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 December 31, 2023 is presented in the following tables. Gross Amount Gross Amount Net Amount December 31, 2023 Financial assets: Derivatives: Loan/lease interest rate swaps and caps $ 70,233 $ — $ 70,233 Commodity swaps and options 49,489 — 49,489 Foreign currency forward/option contracts 1 — 1 Total derivatives 119,723 — 119,723 Resell agreements 84,650 — 84,650 Total $ 204,373 $ — $ 204,373 Financial liabilities: Derivatives: Loan/lease interest rate swaps $ 20,293 $ — $ 20,293 Commodity swaps and options 20,999 — 20,999 Foreign currency forward/option contracts 19 — 19 Total derivatives 41,311 — 41,311 Repurchase agreements 4,127,188 — 4,127,188 Total $ 4,168,499 $ — $ 4,168,499	Information about financial instruments that are eligible for offset in the consolidated balance sheet as of December 31, 2022 is presented in the following tables. Gross Amount Gross Amount Net Amount December 31, 2022 Financial assets: Derivatives: Loan/lease interest rate swaps and caps $ 85,691 $ — $ 85,691 Commodity swaps and options 33,302 — 33,302 Foreign currency forward/option contracts 1 — 1 Total derivatives 118,994 — 118,994 Resell agreements 87,150 — 87,150 Total $ 206,144 $ — $ 206,144 Financial liabilities: Derivatives: Loan/lease interest rate swaps $ 1,102 $ — $ 1,102 Commodity swaps and options 72,717 — 72,717 Foreign currency forward contracts 10 — 10 Total derivatives 73,829 — 73,829 Repurchase agreements 4,660,641 — 4,660,641 Total $ 4,734,470 $ — $ 4,734,470
Financial Instruments Derivative Assets Liabilities And Resell Agreements Net Of Amount Not Offset	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	Gross Amounts Not Offset Net Amount Financial Collateral Net December 31, 2022 Financial assets: Derivatives: Counterparty H $ 27,031 $ (20,564) $ (6,467) $ — Counterparty F 17,297 (17,297) — — Counterparty B 39,370 (24,500) (14,870) — Counterparty E 14,430 (47) (14,131) 252 Other counterparties 20,866 (120) (20,500) 246 Total derivatives 118,994 (62,528) (55,968) 498 Resell agreements 87,150 — (87,150) — Total $ 206,144 $ (62,528) $ (143,118) $ 498 Financial liabilities: Derivatives: Counterparty H $ 20,564 $ (20,564) $ — $ — Counterparty F 27,747 (17,297) (8,479) 1,971 Counterparty B 24,500 (24,500) — — Counterparty E 47 (47) — — Other counterparties 971 (120) (851) — Total derivatives 73,829 (62,528) (9,330) 1,971 Repurchase agreements 4,660,641 — (4,660,641) — Total $ 4,734,470 $ (62,528) $ (4,669,971) $ 1,971
Remaining Contractual Maturity of the Securities Sold Under Agreement	The remaining contractual maturity of repurchase agreements in the consolidated balance sheets as of December 31, 2023 and December 31, 2022 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 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 $ — December 31, 2022 Repurchase agreements: U.S. Treasury $ 3,735,061 $ — $ — $ — $ 3,735,061 Residential mortgage-backed securities 925,580 — — — 925,580 Total borrowings $ 4,660,641 $ — $ — $ — $ 4,660,641 Gross amount of recognized liabilities for repurchase agreements $ 4,660,641 Amounts related to agreements not included in offsetting disclosures above $ —

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	12 Months Ended
	Dec. 31, 2023
Fair Value Disclosures [Abstract]
Financial Assets and Financial Liabilities Measured at Fair Value on a Recurring Basis	The following tables summarize financial assets and financial liabilities measured at fair value on a recurring basis as of December 31, 2023 and 2022, segregated by the level of the valuation inputs within the fair value hierarchy utilized to measure fair value: Level 1 Level 2 Level 3 Total 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/option 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/option contracts 19 — — 19 Level 1 Level 2 Level 3 Total 2022 Securities available for sale: U.S. Treasury $ 5,051,587 $ — $ — $ 5,051,587 Residential mortgage-backed securities — 6,376,236 — 6,376,236 States and political subdivisions — 6,773,355 — 6,773,355 Other — 42,427 — 42,427 Trading account securities: U.S. Treasury 25,879 — — 25,879 States and political subdivisions — 2,166 — 2,166 Derivative assets: Interest rate swaps, caps and floors — 86,793 — 86,793 Commodity swaps and options — 106,685 — 106,685 Foreign currency forward contracts 11 — — 11 Derivative liabilities: Interest rate swaps, caps and floors — 95,533 — 95,533 Commodity swaps and options — 105,392 — 105,392 Foreign currency forward contracts 11 — — 11
Impaired Loans Remeasured and Reported at Fair Value of Underlying 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: 2023 2022 2021 Level 2 Carrying value before allocations $ 19,719 $ 6,237 $ 1,333 Specific (allocations) reversals of prior allocations (3,391) (1,480) 214 Fair value $ 16,328 $ 4,757 $ 1,547 Level 3 Carrying value before allocations $ 15,465 $ 8,156 $ 16,074 Specific (allocations) reversals of prior allocations (2,344) 625 (5,178) Fair value $ 13,121 $ 8,781 $ 10,896
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 valuation inputs within the fair value hierarchy utilized to measure fair value, were as follows: December 31, 2023 December 31, 2022 Carrying Estimated Carrying Estimated Financial assets: Level 2 inputs: Cash and cash equivalents $ 8,687,276 $ 8,687,276 $ 12,028,132 $ 12,028,132 Securities held to maturity 3,619,428 3,532,044 2,639,083 2,467,865 Accrued interest receivable 251,385 251,385 243,682 243,682 Level 3 inputs: Loans, net 18,578,255 18,117,369 16,927,348 16,343,417 Financial liabilities: Level 2 inputs: Deposits 41,920,568 41,903,580 43,954,196 43,920,741 Federal funds purchased 14,200 14,200 51,650 51,650 Repurchase agreements 4,127,188 4,127,188 4,660,641 4,660,641 Junior subordinated deferrable interest debentures 123,127 123,712 123,069 123,712 Subordinated notes 99,491 96,071 99,335 97,014 Accrued interest payable 61,222 61,222 18,444 18,444

Operating Segments (Tables)

Operating Segments (Tables)	12 Months Ended
	Dec. 31, 2023
Segment Reporting [Abstract]
Summary of Operating Results by Segment	Financial results by operating segment are detailed below. Certain prior period amounts have been reclassified to conform to the current presentation. Frost Wealth Advisors excludes off-balance-sheet managed and custody assets with a total fair value of $47.2 billion, $42.9 billion and $43.3 billion at December 31, 2023, 2022 and 2021. Banking Frost Non-Banks Consolidated 2023 Net interest income (expense) $ 1,562,441 $ 7,620 $ (11,397) $ 1,558,664 Credit loss expense 46,171 — — 46,171 Non-interest income 251,319 178,906 (1,683) 428,542 Non-interest expense 1,077,824 144,478 6,360 1,228,662 Income (loss) before income taxes 689,765 42,048 (19,440) 712,373 Income tax expense (benefit) 111,145 8,830 (5,575) 114,400 Net income (loss) 578,620 33,218 (13,865) 597,973 Preferred stock dividends — — 6,675 6,675 Net income (loss) available to common shareholders $ 578,620 $ 33,218 $ (20,540) $ 591,298 Revenues from (expenses to) external customers $ 1,813,760 $ 186,526 $ (13,080) $ 1,987,206 Average assets (in millions) $ 49,536 $ 59 $ 9 $ 49,604 Banking Frost Non-Banks Consolidated 2022 Net interest income (expense) $ 1,295,467 $ 4,645 $ (8,829) $ 1,291,283 Credit loss expense 3,000 — — 3,000 Non-interest income 230,876 175,874 (1,932) 404,818 Non-interest expense 886,421 132,009 5,844 1,024,274 Income (loss) before income taxes 636,922 48,510 (16,605) 668,827 Income tax expense (benefit) 85,127 10,187 (5,637) 89,677 Net income (loss) 551,795 38,323 (10,968) 579,150 Preferred stock dividends — — 6,675 6,675 Net income (loss) available to common shareholders $ 551,795 $ 38,323 $ (17,643) $ 572,475 Revenues from (expenses to) external customers $ 1,526,343 $ 180,519 $ (10,761) $ 1,696,101 Average assets (in millions) $ 51,448 $ 57 $ 8 $ 51,513 2021 Net interest income (expense) $ 989,870 $ 2,138 $ (7,141) $ 984,867 Credit loss expense 54 9 — 63 Non-interest income 220,662 167,442 (1,376) 386,728 Non-interest expense 753,719 122,972 5,303 881,994 Income (loss) before income taxes 456,759 46,599 (13,820) 489,538 Income tax expense (benefit) 41,483 9,786 (4,810) 46,459 Net income (loss) 415,276 36,813 (9,010) 443,079 Preferred stock dividends — — 7,157 7,157 Net income (loss) available to common shareholders $ 415,276 $ 36,813 $ (16,167) $ 435,922 Revenues from (expenses to) external customers $ 1,210,532 $ 169,580 $ (8,517) $ 1,371,595 Average assets (in millions) $ 45,903 $ 70 $ 10 $ 45,983

Condensed Financial Statement_2

Condensed Financial Statements of Parent Company (Tables)	12 Months Ended
	Dec. 31, 2023
Condensed Financial Information Disclosure [Abstract]
Schedule of Condensed Balance Sheets	Condensed Balance Sheets December 31, 2023 2022 Assets: Cash $ 350,525 $ 311,944 Total cash and cash equivalents 350,525 311,944 Investment in subsidiaries 3,625,951 3,065,114 Accrued interest receivable and other assets 1,233 1,142 Total assets $ 3,977,709 $ 3,378,200 Liabilities: Junior subordinated deferrable interest debentures, net of unamortized issuance costs $ 123,127 $ 123,069 Subordinated notes, net of unamortized issuance costs 99,491 99,335 Accrued interest payable and other liabilities 38,644 18,568 Total liabilities 261,262 240,972 Shareholders’ Equity 3,716,447 3,137,228 Total liabilities and shareholders’ equity $ 3,977,709 $ 3,378,200
Schedule of Condensed Statements of Income	Condensed Statements of Income Year Ended December 31, 2023 2022 2021 Income: Dividend income paid by Frost Bank $ 279,679 $ 51,711 $ 219,386 Dividend income paid by non-banks 255 109 473 Interest and other income 1,929 — 101 Total income 281,863 51,820 219,960 Expenses: Interest expense 13,304 8,829 7,141 Salaries and employee benefits 1,668 1,605 1,499 Other 6,653 6,316 5,867 Total expenses 21,625 16,750 14,507 Income before income taxes and equity in undistributed earnings of subsidiaries 260,238 35,070 205,453 Income tax benefit 5,974 5,641 4,899 Equity in undistributed earnings of subsidiaries 331,761 538,439 232,727 Net income 597,973 579,150 443,079 Preferred stock dividends 6,675 6,675 7,157 Net income available to common shareholders $ 591,298 $ 572,475 $ 435,922
Schedule of Condensed Statements of Cash Flows	Condensed Statements of Cash Flows Year Ended December 31, 2023 2022 2021 Operating Activities: Net income $ 597,973 $ 579,150 $ 443,079 Adjustments to reconcile net income to net cash provided by operating activities: Equity in undistributed earnings of subsidiaries (331,761) (538,439) (232,727) Stock-based compensation 880 720 700 Net tax benefit from stock-based compensation 331 472 278 Net change in other assets and other liabilities 19,867 (15,249) 23,890 Net cash from operating activities 287,290 26,654 235,220 Investing Activities: Redemption of investment in non-bank subsidiary — — 406 Net cash from investing activities — — 406 Financing Activities: Principal payments on long-term borrowings — — (13,403) Proceeds from stock option exercises 9,299 16,659 54,417 Proceeds from stock-based compensation activities of subsidiaries 23,710 17,602 12,053 Purchase of treasury stock (42,720) (4,391) (3,864) Treasury stock issued to 401(k) stock purchase plan — — 1,749 Cash dividends paid on preferred stock (6,675) (6,675) (7,157) Cash dividends paid on common stock (232,323) (209,780) (188,786) Net cash from financing activities (248,709) (186,585) (144,991) Net change in cash and cash equivalents 38,581 (159,931) 90,635 Cash and cash equivalents at beginning of year 311,944 471,875 381,240 Cash and cash equivalents at end of year $ 350,525 $ 311,944 $ 471,875

Summary of Significant Accoun_4

Summary of Significant Accounting Policies (Narrative) (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cash collateral on deposit	$ 8,600	$ 3,200
Foreclosed assets	725	1,000
Real Estate Owned, Valuation Allowance, Provision	$ 0	$ 0	$ 14
Amount of significant concentrations of any properties with write downs from any single geographic region	0%	0%	0%
Minimum [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Range of change in fair value of derivative hedging instrument to be considered highly effective	80%
Maximum [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Range of change in fair value of derivative hedging instrument to be considered highly effective	125%

Summary of Significant Accoun_5

Summary of Significant Accounting Policies (Additional Cash Flow Information) (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Accounting Policies [Abstract]
Cash paid for interest	$ 616,274	$ 169,020	$ 29,003
Cash paid for income tax	118,000	100,000	39,852
Exchange of real estate	0	0	11,036
Unsettled securities transactions	1,452	94,884	27,032
Loans foreclosed and transferred to other real estate owned and foreclosed assets	0	239	3,464
Right-of-use lease assets obtained in exchange for lessee operating lease liabilities	15,259	31,787	12,854
Treasury stock issued to 401(k) stock purchase plan	$ 0	$ 0	$ 1,749

Securities (Narrative) (Detail)

Securities (Narrative) (Detail) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Schedule Of Marketable Securities [Line Items]
Net unamortized, unrealized gain on transferred securities included in accumulated other comprehensive income, pre tax	$ 1,200	$ 1,800
Net unamortized, unrealized gain on transferred securities included in accumulated other comprehensive income, net of tax	909	1,400
Debt Securities, Held-to-maturity, 90 Days or More Past Due, Still Accruing	0
Securities held to maturity, net of allowance for credit losses of $310 in 2023 and $158 in 2022	$ 310	158
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	73.50%
Debt Securities, Available-for-sale, Allowance for Credit Loss	$ 0	0
Debt Securities [Member]
Schedule Of Marketable Securities [Line Items]
Securities held to maturity, net of allowance for credit losses of $310 in 2023 and $158 in 2022	310	158	$ 158	$ 160
Held-to-maturity Securities [Member]
Schedule Of Marketable Securities [Line Items]
Carry value of securities pledged	1,000,000	256,300
Accrued interest receivable	40,900	30,200
Guaranteed by the Texas PSF [Member] | Debt Securities [Member]
Schedule Of Marketable Securities [Line Items]
Securities held to maturity, net of allowance for credit losses of $310 in 2023 and $158 in 2022	0
Pre-Refunded [Member] | Debt Securities [Member]
Schedule Of Marketable Securities [Line Items]
Securities held to maturity, net of allowance for credit losses of $310 in 2023 and $158 in 2022	0
Available-for-sale Securities [Member]
Schedule Of Marketable Securities [Line Items]
Carry value of securities pledged	6,100,000	8,000,000
Accrued interest receivable	$ 114,900	$ 140,600

Securities (Year End Securities

Securities (Year End Securities Held to Maturity) (Detail) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Schedule of Investments [Line Items]
Held to Maturity, Amortized Cost	$ 3,619,738	$ 2,639,241
Debt Securities, Held-to-maturity, Accumulated Unrecognized Gain	43,066	13,048
Debt Securities, Held-to-maturity, Accumulated Unrecognized Loss	130,760	184,424
Debt Securities, Held to Maturity, Estimated Fair Value	3,532,044	2,467,865
Debt Securities, Held-to-maturity, Allowance for Credit Loss	(310)	(158)
Securities held to maturity, net of allowance for credit losses of $310 in 2023 and $158 in 2022	3,619,428	2,639,083
Residential Mortgage Backed Securities [Member]
Schedule of Investments [Line Items]
Held to Maturity, Amortized Cost	1,250,431	526,122
Debt Securities, Held-to-maturity, Accumulated Unrecognized Gain	76	0
Debt Securities, Held-to-maturity, Accumulated Unrecognized Loss	54,175	65,322
Debt Securities, Held to Maturity, Estimated Fair Value	1,196,332	460,800
Debt Securities, Held-to-maturity, Allowance for Credit Loss	0	0
Securities held to maturity, net of allowance for credit losses of $310 in 2023 and $158 in 2022	1,250,431	526,122
States and Political Subdivisions [Member]
Schedule of Investments [Line Items]
Held to Maturity, Amortized Cost	2,367,807	2,111,619
Debt Securities, Held-to-maturity, Accumulated Unrecognized Gain	42,990	13,048
Debt Securities, Held-to-maturity, Accumulated Unrecognized Loss	76,540	119,033
Debt Securities, Held to Maturity, Estimated Fair Value	2,334,257	2,005,634
Debt Securities, Held-to-maturity, Allowance for Credit Loss	(310)	(158)
Securities held to maturity, net of allowance for credit losses of $310 in 2023 and $158 in 2022	2,367,497	2,111,461
Other [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	45	69
Debt Securities, Held to Maturity, Estimated Fair Value	1,455	1,431
Debt Securities, Held-to-maturity, Allowance for Credit Loss	0	0
Securities held to maturity, net of allowance for credit losses of $310 in 2023 and $158 in 2022	$ 1,500	$ 1,500

Securities (Securities Moody's

Securities (Securities Moody's and Standard & Poor's Bond Rating) (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Schedule of Held-to-maturity Securities [Line Items]
Held to Maturity, Amortized Cost	$ 3,619,738	$ 2,639,241
States and Political Subdivisions [Member]
Schedule of Held-to-maturity Securities [Line Items]
Held to Maturity, Amortized Cost	2,367,807	2,111,619
States and Political Subdivisions [Member] | Not Guaranteed or Pre-Refunded [Member]
Schedule of Held-to-maturity Securities [Line Items]
Held to Maturity, Amortized Cost	804,737
States and Political Subdivisions [Member] | Guaranteed by the Texas PSF [Member]
Schedule of Held-to-maturity Securities [Line Items]
Held to Maturity, Amortized Cost	1,541,913
States and Political Subdivisions [Member] | Guaranteed by Third Party
Schedule of Held-to-maturity Securities [Line Items]
Held to Maturity, Amortized Cost	19,756
States and Political Subdivisions [Member] | Pre-Refunded [Member]
Schedule of Held-to-maturity Securities [Line Items]
Held to Maturity, Amortized Cost	1,401
Other [Member]
Schedule of Held-to-maturity Securities [Line Items]
Held to Maturity, Amortized Cost	1,500	$ 1,500
Aaa/AAA [Member] | States and Political Subdivisions [Member]
Schedule of Held-to-maturity Securities [Line Items]
Held to Maturity, Amortized Cost	1,858,686
Aaa/AAA [Member] | States and Political Subdivisions [Member] | Not Guaranteed or Pre-Refunded [Member]
Schedule of Held-to-maturity Securities [Line Items]
Held to Maturity, Amortized Cost	301,721
Aaa/AAA [Member] | States and Political Subdivisions [Member] | Guaranteed by the Texas PSF [Member]
Schedule of Held-to-maturity Securities [Line Items]
Held to Maturity, Amortized Cost	1,541,913
Aaa/AAA [Member] | States and Political Subdivisions [Member] | Guaranteed by Third Party
Schedule of Held-to-maturity Securities [Line Items]
Held to Maturity, Amortized Cost	13,651
Aaa/AAA [Member] | States and Political Subdivisions [Member] | Pre-Refunded [Member]
Schedule of Held-to-maturity Securities [Line Items]
Held to Maturity, Amortized Cost	1,401
Aaa/AAA [Member] | Other [Member]
Schedule of Held-to-maturity Securities [Line Items]
Held to Maturity, Amortized Cost	0
Aa/AA [Member] | States and Political Subdivisions [Member]
Schedule of Held-to-maturity Securities [Line Items]
Held to Maturity, Amortized Cost	509,121
Aa/AA [Member] | States and Political Subdivisions [Member] | Not Guaranteed or Pre-Refunded [Member]
Schedule of Held-to-maturity Securities [Line Items]
Held to Maturity, Amortized Cost	503,016
Aa/AA [Member] | States and Political Subdivisions [Member] | Guaranteed by the Texas PSF [Member]
Schedule of Held-to-maturity Securities [Line Items]
Held to Maturity, Amortized Cost	0
Aa/AA [Member] | States and Political Subdivisions [Member] | Guaranteed by Third Party
Schedule of Held-to-maturity Securities [Line Items]
Held to Maturity, Amortized Cost	6,105
Aa/AA [Member] | States and Political Subdivisions [Member] | Pre-Refunded [Member]
Schedule of Held-to-maturity Securities [Line Items]
Held to Maturity, Amortized Cost	0
Aa/AA [Member] | Other [Member]
Schedule of Held-to-maturity Securities [Line Items]
Held to Maturity, Amortized Cost	0
Not rated [Member] | States and Political Subdivisions [Member]
Schedule of Held-to-maturity Securities [Line Items]
Held to Maturity, Amortized Cost	0
Not rated [Member] | States and Political Subdivisions [Member] | Not Guaranteed or Pre-Refunded [Member]
Schedule of Held-to-maturity Securities [Line Items]
Held to Maturity, Amortized Cost	0
Not rated [Member] | States and Political Subdivisions [Member] | Guaranteed by the Texas PSF [Member]
Schedule of Held-to-maturity Securities [Line Items]
Held to Maturity, Amortized Cost	0
Not rated [Member] | States and Political Subdivisions [Member] | Guaranteed by Third Party
Schedule of Held-to-maturity Securities [Line Items]
Held to Maturity, Amortized Cost	0
Not rated [Member] | States and Political Subdivisions [Member] | Pre-Refunded [Member]
Schedule of Held-to-maturity Securities [Line Items]
Held to Maturity, Amortized Cost	0
Not rated [Member] | Other [Member]
Schedule of Held-to-maturity Securities [Line Items]
Held to Maturity, Amortized Cost	$ 1,500

Securities (Securities Held to

Securities (Securities Held to Maturity Allowance for Credit Loss) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Schedule of Held-to-maturity Securities [Line Items]
Securities held to maturity, net of allowance for credit losses of $310 in 2023 and $158 in 2022	$ 310	$ 158
Debt Securities [Member]
Schedule of Held-to-maturity Securities [Line Items]
Securities held to maturity, net of allowance for credit losses of $310 in 2023 and $158 in 2022	310	158	$ 158	$ 160
Debt Securities, Held-to-maturity, Allowance for Credit Loss, Period Increase (Decrease)	$ 152	$ 0	$ (2)

Securities (Securities Availabl

Securities (Securities Available for Sale) (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Schedule of Investments [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	$ 17,965,338	$ 19,908,432
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	14,828	17,158
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	1,401,795	1,681,985
Debt Securities, Available-for-sale, Allowance for Credit Loss	0	0
Debt Securities, Available-for-sale	16,578,371	18,243,605
US Treasury [Member]
Schedule of Investments [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	5,212,894	5,450,546
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	0	0
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	285,305	398,959
Debt Securities, Available-for-sale, Allowance for Credit Loss	0	0
Debt Securities, Available-for-sale	4,927,589	5,051,587
Residential Mortgage Backed Securities [Member]
Schedule of Investments [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	7,463,954	7,316,824
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	9,066	8,050
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	876,338	948,638
Debt Securities, Available-for-sale, Allowance for Credit Loss	0	0
Debt Securities, Available-for-sale	6,596,682	6,376,236
States and Political Subdivisions [Member]
Schedule of Investments [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	5,245,721	7,098,635
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	5,762	9,108
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	240,152	334,388
Debt Securities, Available-for-sale, Allowance for Credit Loss	0	0
Debt Securities, Available-for-sale	5,011,331	6,773,355
Other [Member]
Schedule of Investments [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	42,769	42,427
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	0	0
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	0	0
Debt Securities, Available-for-sale, Allowance for Credit Loss	0	0
Debt Securities, Available-for-sale	$ 42,769	$ 42,427

Securities (Year End Securiti_2

Securities (Year End Securities with Unrealized Losses Segregated by Length of Impairment) (Detail) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Schedule of Available-for-Sale Securities [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	$ 2,689,753
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	16,918
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	12,642,997
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	1,384,877
Available for Sale, Total Estimated Fair Value	15,332,750
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	1,401,795	$ 1,681,985
US 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	4,927,590
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	285,305
Available for Sale, Total Estimated Fair Value	4,927,590
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	285,305	398,959
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	879,380
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	6,883
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	5,062,456
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	869,455
Available for Sale, Total Estimated Fair Value	5,941,836
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	876,338	948,638
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	1,810,373
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	10,035
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	2,652,951
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	230,117
Available for Sale, Total Estimated Fair Value	4,463,324
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	$ 240,152	$ 334,388

Securities (Amortized Cost and

Securities (Amortized Cost and Estimated Fair Value of Securities Excluding Trading Securities Presented by Contractual Maturity) (Detail) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Schedule of Available-for-Sale Securities [Line Items]
Held to Maturity, Due in one year or less, Amortized Cost	$ 8,170
Held to Maturity, Due after one year through five years, Amortized Cost	13,508
Held to Maturity, Due after five years through ten years, Amortized Cost	565,101
Held to Maturity, Due after ten years, Amortized Cost	3,032,959
Held to Maturity, Amortized Cost	3,619,738	$ 2,639,241
Held to Maturity, Due in one year or less, Estimated Fair Value	8,175
Held to Maturity, Due after one year through five years, Estimated Fair Value	13,454
Held to Maturity, Due after five years through ten years, Estimated Fair Value	511,981
Held to Maturity, Due after ten years, Estimated Fair Value	2,998,434
Held to Maturity, Estimated Fair Value	3,532,044	2,467,865
Available for Sale, Due in one year or less, Amortized Cost	1,906,306
Available for Sale, Due after one year through five years, Amortized Cost	3,473,420
Available for Sale, Due after five years through ten years, Amortized Cost	1,092,453
Available for Sale, Due after ten years, Amortized Cost	11,450,390
Debt Securities, Available-for-sale, Amortized Cost	17,965,338	19,908,432
Available for Sale, Due in one year or less, Estimated Fair Value	1,886,056
Available for Sale, Due after one year through five years, Estimated Fair Value	3,286,388
Available for Sale, Due after five years through ten years, Estimated Fair Value	1,040,857
Available for Sale, Due after ten years, Estimated Fair Value	10,322,301
Debt Securities, Available-for-sale	16,578,371	18,243,605
US Treasury [Member]
Schedule of Available-for-Sale Securities [Line Items]
Available for Sale, Due in one year or less, Amortized Cost	1,534,307
Available for Sale, Due after one year through five years, Amortized Cost	3,288,365
Available for Sale, Due after five years through ten years, Amortized Cost	197,809
Available for Sale, Due after ten years, Amortized Cost	192,413
Debt Securities, Available-for-sale, Amortized Cost	5,212,894	5,450,546
Available for Sale, Due in one year or less, Estimated Fair Value	1,514,227
Available for Sale, Due after one year through five years, Estimated Fair Value	3,101,776
Available for Sale, Due after five years through ten years, Estimated Fair Value	167,219
Available for Sale, Due after ten years, Estimated Fair Value	144,367
Debt Securities, Available-for-sale	4,927,589	5,051,587
Residential Mortgage Backed Securities [Member]
Schedule of Available-for-Sale Securities [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	512,995
Held to Maturity, Due after ten years, Amortized Cost	737,436
Held to Maturity, Amortized Cost	1,250,431	526,122
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	461,253
Held to Maturity, Due after ten years, Estimated Fair Value	735,079
Held to Maturity, Estimated Fair Value	1,196,332	460,800
Available for Sale, Due in one year or less, Amortized Cost	1,740
Available for Sale, Due after one year through five years, Amortized Cost	1,827
Available for Sale, Due after five years through ten years, Amortized Cost	13,985
Available for Sale, Due after ten years, Amortized Cost	7,446,402
Debt Securities, Available-for-sale, Amortized Cost	7,463,954	7,316,824
Available for Sale, Due in one year or less, Estimated Fair Value	1,718
Available for Sale, Due after one year through five years, Estimated Fair Value	1,826
Available for Sale, Due after five years through ten years, Estimated Fair Value	13,963
Available for Sale, Due after ten years, Estimated Fair Value	6,579,175
Debt Securities, Available-for-sale	6,596,682	6,376,236
States and Political Subdivisions [Member]
Schedule of Available-for-Sale Securities [Line Items]
Held to Maturity, Due in one year or less, Amortized Cost	8,170
Held to Maturity, Due after one year through five years, Amortized Cost	12,008
Held to Maturity, Due after five years through ten years, Amortized Cost	52,106
Held to Maturity, Due after ten years, Amortized Cost	2,295,523
Held to Maturity, Amortized Cost	2,367,807	2,111,619
Held to Maturity, Due in one year or less, Estimated Fair Value	8,175
Held to Maturity, Due after one year through five years, Estimated Fair Value	11,999
Held to Maturity, Due after five years through ten years, Estimated Fair Value	50,728
Held to Maturity, Due after ten years, Estimated Fair Value	2,263,355
Held to Maturity, Estimated Fair Value	2,334,257	2,005,634
Available for Sale, Due in one year or less, Amortized Cost	370,259
Available for Sale, Due after one year through five years, Amortized Cost	183,228
Available for Sale, Due after five years through ten years, Amortized Cost	880,659
Available for Sale, Due after ten years, Amortized Cost	3,811,575
Debt Securities, Available-for-sale, Amortized Cost	5,245,721	7,098,635
Available for Sale, Due in one year or less, Estimated Fair Value	370,111
Available for Sale, Due after one year through five years, Estimated Fair Value	182,786
Available for Sale, Due after five years through ten years, Estimated Fair Value	859,675
Available for Sale, Due after ten years, Estimated Fair Value	3,598,759
Debt Securities, Available-for-sale	5,011,331	6,773,355
Other [Member]
Schedule of Available-for-Sale Securities [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	1,500
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	0
Held to Maturity, Due after one year through five years, Estimated Fair Value	1,455
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	1,455	1,431
Available for Sale, 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	42,769	42,427
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
Debt Securities, Available-for-sale	$ 42,769	$ 42,427

Securities (Sales of Securities

Securities (Sales of Securities Available for Sale) (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Investments, Debt and Equity Securities [Abstract]
Proceeds from sales	$ 1,904,067	$ 0	$ 1,999,891
Gross realized gains	5,758	0	69
Gross realized losses	(5,692)	0	0
Tax benefit (expense) related to securities gains/losses	$ (14)	$ 0	$ (14)

Securities Securities - (Premiu

Securities Securities - (Premium Amortization and Discount Accretion Included in Income on Securities) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Investments, Debt and Equity Securities [Abstract]
Premium amortization	$ (85,506)	$ (110,997)	$ (121,994)
Discount accretion	21,613	13,597	2,752
Net (premium amortization) discount accretion	$ (63,893)	$ (97,400)	$ (119,242)

Securities (Year End Trading Ac

Securities (Year End Trading Account Securities at Estimated Fair Value) (Detail) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Debt and Equity Securities, FV-NI [Line Items]
Trading account securities	$ 31,717	$ 28,045
US Treasury [Member]
Debt and Equity Securities, FV-NI [Line Items]
Trading account securities	30,265	25,879
States and Political Subdivisions [Member]
Debt and Equity Securities, FV-NI [Line Items]
Trading account securities	$ 1,452	$ 2,166

Securities (Net Gains and Losse

Securities (Net Gains and Losses on Trading Account Securities) (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Investments, Debt and Equity Securities [Abstract]
Net gain on sales transactions	$ 3,843	$ 3,129	$ 1,014
Net mark-to-market gains (losses)	(33)	(230)	(75)
Net gain on trading account securities	$ 3,810	$ 2,899	$ 939

Loans (Narrative) (Detail)

Loans (Narrative) (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2023 USD ($) Grade Rate	Dec. 31, 2022 USD ($) Grade	Dec. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)
Accounts, Notes, Loans and Financing Receivable [Line Items]
U.S. dollar denominated loans and commitments to borrowers in Mexico	$ 0	$ 0
Commercial and industrial loans related to overdraft for correspondent bank customer	$ 13,400	10,300
Financing Receivable, Threshold Period Past Due	90 days
Loans, net of unearned discounts	$ 18,824,251	$ 17,154,969
Loans Receivable, Basis Spread on Variable Rate | Rate	1.75%
Loan Receivable Variable Rate | Rate	10.25%
Loan Receivable Fixed Rate | Rate	6.74%
Number of days past due for payment of interest on loans, minimum	120 days
Texas Leading Index economic condition indicator	126.8	130.4
Financing Receivable, Change in Method, Credit Loss Expense (Reversal)	$ (45,000)
Financing Receivable, Allowance for Credit Loss	245,996	$ 227,621
Additional Funding Agreement Terms
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	0
Nonperforming Financial Instruments [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	25,974	6,301
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	359	1,510
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	24,302
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	6,537
Loans Receivable [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accrued interest receivable	$ 90,800	68,700
Commercial and Industrial Total Energy Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Percentage of total loans	5%
Loans, net of unearned discounts	$ 935,265	$ 925,729
Weighted Average Risk Grade | Grade	6.05	5.67
Financing Receivable, Allowance for Credit Loss	$ 17,814	$ 18,062	$ 17,217	$ 39,553
Financing Receivable, Year One, Originated, Current Fiscal Year	277,722	352,224
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	61,500	100,862
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	5,875	4,657
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	0	0
Commercial and Industrial Total Energy Loans [Member] | Financial Asset, Other than Financial Asset Acquired with Credit Deterioration | Nonperforming Financial Instruments [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	0
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	0
Commercial and Industrial Total Energy Loans [Member] | Risk Grade One To Eight [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	$ 869,749	$ 887,182
Weighted Average Risk Grade | Grade	5.73	5.44
Financing Receivable, Year One, Originated, Current Fiscal Year	$ 270,710	$ 338,050
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	54,185	99,089
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	$ 4,000	1,700	1,800
Grade 12 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
General percentage of valuation allowance in excess of principal balance, maximum	30%
Grade 13 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
General percentage of valuation allowance in excess of principal balance, minimum	30%
Commercial Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	$ 5,959,133	$ 5,674,798
Weighted Average Risk Grade | Grade	6.60	6.39
Financing Receivable, Allowance for Credit Loss	$ 74,006	$ 104,237	72,091	73,843
Financing Receivable, Year One, Originated, Current Fiscal Year	1,619,306	1,703,185
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	768,246	657,039
Commercial Portfolio Segment [Member] | Nonperforming Financial Instruments [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	0	0
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	359	1,252
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	124
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	1,704
Commercial Portfolio Segment [Member] | Risk Grade One To Eight [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	$ 5,499,829	$ 5,435,917
Weighted Average Risk Grade | Grade	6.32	6.24
Financing Receivable, Year One, Originated, Current Fiscal Year	$ 1,489,026	$ 1,667,274
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	$ 706,210	618,756
Commercial and Industrial, Other Commercial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of days past due for payment of interest on loans, minimum	180 days
Commercial Real Estate Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	$ 8,982,644	$ 8,183,325
Weighted Average Risk Grade | Grade	7.24	7.10
Financing Receivable, Allowance for Credit Loss	$ 130,598	$ 90,301	144,936	134,892
Financing Receivable, Year One, Originated, Current Fiscal Year	2,205,943	2,567,912
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	2,361,998	2,019,736
Commercial Real Estate Buildings Land And Other Financing Receivable [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	$ 7,301,920	$ 6,706,078
Weighted Average Risk Grade | Grade	7.20	7.09
Financing Receivable, Year One, Originated, Current Fiscal Year	$ 1,645,223	$ 1,901,888
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	1,785,624	1,528,173
Commercial Real Estate Buildings Land And Other Financing Receivable [Member] | Nonperforming Financial Instruments [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	20,099	1,644
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	0	0
Commercial Real Estate Buildings Land And Other Financing Receivable [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	6
Commercial Real Estate Buildings Land And Other Financing Receivable [Member] | Risk Grade One To Eight [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	$ 6,895,358	$ 6,340,028
Weighted Average Risk Grade | Grade	7.03	6.94
Financing Receivable, Year One, Originated, Current Fiscal Year	$ 1,601,175	$ 1,811,069
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	1,667,750	1,484,811
Construction Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	$ 1,680,724	$ 1,477,247
Weighted Average Risk Grade | Grade	7.45	7.12
Financing Receivable, Year One, Originated, Current Fiscal Year	$ 560,720	$ 666,024
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	576,374	491,563
Construction Loans [Member] | Nonperforming Financial Instruments [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	0	0
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	0	0
Construction 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	739
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	0
Construction Loans [Member] | Risk Grade One To Eight [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	$ 1,526,086	$ 1,430,012
Weighted Average Risk Grade | Grade	7.27	7.04
Financing Receivable, Year One, Originated, Current Fiscal Year	$ 538,072	$ 640,948
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	537,705	489,391
Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	476,962	492,726
Financing Receivable, Allowance for Credit Loss	10,040	7,017	7,837	$ 6,963
Consumer Loan [Member] | Nonperforming Financial Instruments [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	0	0
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	0	0
Consumer Loan [Member] | Financial Asset, Other than Financial Asset Acquired with Credit Deterioration | Nonperforming Financial Instruments [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	23,321
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	4,546
Paycheck Protection Program [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	9,521	34,852
Financing Receivable, Allowance for Credit Loss	0	$ 0	$ 0
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	23,100
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	$ 4,200
Automobile Loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Percentage of total loans	5.90%
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
Commitments to Extend Credit [Member] | Automobile Loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unfunded balances	522,800
Standby Letters of Credit [Member] | Commercial and Industrial Total Energy Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unfunded balances	86,900
Standby Letters of Credit [Member] | Automobile Loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unfunded balances	$ 19,300

Loans (Loans) (Detail)

Loans (Loans) (Detail) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	$ 18,824,251	$ 17,154,969
Commercial Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	5,959,133	5,674,798
Energy Production [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	681,568	696,570
Energy Service [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	192,654	133,542
Energy Other [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	61,043	95,617
Commercial and Industrial Total Energy Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	935,265	925,729
Paycheck Protection Program [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	9,521	34,852
Commercial mortgage [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	6,746,709	6,168,910
Construction Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	1,680,724	1,477,247
Commercial land loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	555,211	537,168
Commercial Real Estate Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	8,982,644	8,183,325
Home Equity Line of Credit [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	792,876	691,841
Home Equity Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	694,966	449,507
Home Improvement Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	765,887	577,377
Other consumer real estate loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	206,997	124,814
Total consumer real estate loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	2,460,726	1,843,539
Real Estate Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	11,443,370	10,026,864
Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	$ 476,962	$ 492,726

Loans (Activities in Related Pa

Loans (Activities in Related Party Loans) (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2023 USD ($)
Receivables [Abstract]
Balance outstanding at December 31, 2022	$ 391,255
Principal additions	322,183
Principal payments	(299,338)
Other changes	2,007
Balance outstanding at December 31, 2023	$ 416,107

Loans (Non-Accrual Loans, Segre

Loans (Non-Accrual Loans, Segregated by Class of Loans) (Detail) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Non Accrual Loans Segregated By Class Of Loans [Line Items]
Non-accrual loans	$ 60,907	$ 37,833
Financing Receivable, Nonaccrual, No Allowance	22,932	18,571
Commercial Portfolio Segment [Member]
Non Accrual Loans Segregated By Class Of Loans [Line Items]
Non-accrual loans	19,545	18,130
Financing Receivable, Nonaccrual, No Allowance	5,391	8,514
Commercial and Industrial Total Energy Loans [Member]
Non Accrual Loans Segregated By Class Of Loans [Line Items]
Non-accrual loans	11,500	15,224
Financing Receivable, Nonaccrual, No Allowance	7,398	7,139
Commercial Real Estate, Buildings, Land and Other [Member]
Non Accrual Loans Segregated By Class Of Loans [Line Items]
Non-accrual loans	22,420	3,552
Financing Receivable, Nonaccrual, No Allowance	4,983	1,991
Construction Loans [Member]
Non Accrual Loans Segregated By Class Of Loans [Line Items]
Non-accrual loans	0	0
Financing Receivable, Nonaccrual, No Allowance	0	0
Total consumer real estate loans [Member]
Non Accrual Loans Segregated By Class Of Loans [Line Items]
Non-accrual loans	7,442	927
Financing Receivable, Nonaccrual, No Allowance	5,160	927
Consumer Loan [Member]
Non Accrual Loans Segregated By Class Of Loans [Line Items]
Non-accrual loans	0	0
Financing Receivable, Nonaccrual, No Allowance	$ 0	$ 0

Loans (Non-Accrual Loans, Seg_2

Loans (Non-Accrual Loans, Segregated by Class of Loan and Year of Origination) (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Loans and Leases Receivable Disclosure [Line Items]
Non-accrual loans	$ 60,907	$ 37,833
Commercial Portfolio Segment [Member]
Loans and Leases Receivable Disclosure [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	1,619,306	1,703,185
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	768,246	657,039
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	491,938	498,213
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	364,446	241,997
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	182,089	138,541
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	219,766	195,754
Financing Receivable, Revolving	2,247,752	2,170,182
Non-accrual loans	19,545	18,130
Commercial and Industrial Total Energy Loans [Member]
Loans and Leases Receivable Disclosure [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	277,722	352,224
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	61,500	100,862
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	74,631	5,312
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	3,835	8,659
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	6,876	3,078
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	4,541	2,913
Financing Receivable, Revolving	495,329	408,022
Non-accrual loans	11,500	15,224
Commercial Real Estate, Buildings, Land and Other [Member]
Loans and Leases Receivable Disclosure [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	1,645,223	1,901,888
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	1,785,624	1,528,173
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	1,253,062	1,009,197
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	811,574	745,031
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	522,566	410,327
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	953,768	882,021
Financing Receivable, Revolving	229,733	120,958
Non-accrual loans	22,420	3,552
Construction Loans [Member]
Loans and Leases Receivable Disclosure [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	560,720	666,024
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	576,374	491,563
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	344,641	130,888
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	28,063	2,236
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	296	486
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	1,613	1,726
Financing Receivable, Revolving	169,017	181,180
Non-accrual loans	0	0
Total consumer real estate loans [Member]
Loans and Leases Receivable Disclosure [Line Items]
Non-accrual loans	7,442	927
Consumer Loan [Member]
Loans and Leases Receivable Disclosure [Line Items]
Non-accrual loans	0	0
Nonperforming Financial Instruments [Member]
Loans and Leases Receivable Disclosure [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	25,974	6,301
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	359	1,510
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	1,785	1,161
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	1,079	4,845
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	6,310	1,473
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	2,209	1,700
Financing Receivable, Revolving	5,711	10,604
Financing Receivable, Revolving, Converted to Term Loan	17,480	10,239
Nonperforming Financial Instruments [Member] | Commercial Portfolio Segment [Member]
Loans and Leases Receivable Disclosure [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	0	0
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	359	1,252
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	1,635	1,089
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	985	3,242
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	1,257	1,197
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	1,006	191
Financing Receivable, Revolving	9	2,973
Financing Receivable, Revolving, Converted to Term Loan	14,294	8,186
Nonperforming Financial Instruments [Member] | Commercial and Industrial Total Energy Loans [Member]
Loans and Leases Receivable Disclosure [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	5,875	4,657
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	0	0
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	0	72
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	56	1,386
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	1,321	10
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	0	0
Financing Receivable, Revolving	4,102	7,631
Financing Receivable, Revolving, Converted to Term Loan	146	1,468
Nonperforming Financial Instruments [Member] | Commercial Real Estate, Buildings, Land and Other [Member]
Loans and Leases Receivable Disclosure [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	20,099	1,644
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	0	0
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	150	0
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	0	217
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	1,451	266
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	720	1,425
Financing Receivable, Revolving	0	0
Financing Receivable, Revolving, Converted to Term Loan	0	0
Nonperforming Financial Instruments [Member] | Construction Loans [Member]
Loans and Leases Receivable Disclosure [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	0	0
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	0	0
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	0	0
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	0	0
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	0	0
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	0	0
Financing Receivable, Revolving	0	0
Financing Receivable, Revolving, Converted to Term Loan	0	0
Nonperforming Financial Instruments [Member] | Total consumer real estate loans [Member]
Loans and Leases Receivable Disclosure [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	0	0
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	0	258
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	0	0
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	38	0
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	2,281	0
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	483	84
Financing Receivable, Revolving	1,600	0
Financing Receivable, Revolving, Converted to Term Loan	3,040	585
Nonperforming Financial Instruments [Member] | Consumer Loan [Member]
Loans and Leases Receivable Disclosure [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	0	0
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	0	0
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	0	0
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	0	0
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	0	0
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	0	0
Financing Receivable, Revolving	0	0
Financing Receivable, Revolving, Converted to Term Loan	$ 0	$ 0

Loans (Age Analysis of Past Due

Loans (Age Analysis of Past Due Loans, Segregated by Class of Loans) (Detail) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Financing Receivable, Past Due [Line Items]
Total loans	$ 18,824,251	$ 17,154,969
Accruing Loans 90 or More Days Past Due	15,033
Commercial Portfolio Segment [Member]
Financing Receivable, Past Due [Line Items]
Total loans	5,959,133	5,674,798
Accruing Loans 90 or More Days Past Due	5,503
Commercial and Industrial Total Energy Loans [Member]
Financing Receivable, Past Due [Line Items]
Total loans	935,265	925,729
Accruing Loans 90 or More Days Past Due	1,146
Paycheck Protection Program [Member]
Financing Receivable, Past Due [Line Items]
Total loans	9,521	34,852
Accruing Loans 90 or More Days Past Due	1,954
Commercial Real Estate, Buildings, Land and Other [Member]
Financing Receivable, Past Due [Line Items]
Total loans	7,301,920	6,706,078
Accruing Loans 90 or More Days Past Due	92
Construction Loans [Member]
Financing Receivable, Past Due [Line Items]
Total loans	1,680,724	1,477,247
Accruing Loans 90 or More Days Past Due	3,498
Total consumer real estate loans [Member]
Financing Receivable, Past Due [Line Items]
Total loans	2,460,726	1,843,539
Accruing Loans 90 or More Days Past Due	2,589
Consumer Loan [Member]
Financing Receivable, Past Due [Line Items]
Total loans	476,962	492,726
Accruing Loans 90 or More Days Past Due	251
Financing Receivables, 30 to 89 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	78,100
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	27,551
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	6,387
Financing Receivables, 30 to 89 Days Past Due [Member] | Paycheck Protection Program [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	61
Financing Receivables, 30 to 89 Days Past Due [Member] | Commercial Real Estate, Buildings, Land and Other [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	20,224
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	4,878
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	12,504	7,856
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	6,495	5,155
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	43,505
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	21,705
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	6,771
Financial Asset, Equal to or Greater than 90 Days Past Due [Member] | Paycheck Protection Program [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	1,954
Financial Asset, Equal to or Greater than 90 Days Past Due [Member] | Commercial Real Estate, Buildings, Land and Other [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	1,610
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	3,498
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	7,716	2,690
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	251	311
Financial Asset, Past Due
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	121,605
Financial Asset, Past Due | Commercial Portfolio Segment [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	49,256
Financial Asset, Past Due | Commercial and Industrial Total Energy Loans [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	13,158
Financial Asset, Past Due | Paycheck Protection Program [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	2,015
Financial Asset, Past Due | Commercial Real Estate, Buildings, Land and Other [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	21,834
Financial Asset, Past Due | Construction Loans [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	8,376
Financial Asset, Past Due | Total consumer real estate loans [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	20,220	10,546
Financial Asset, Past Due | Consumer Loan [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	6,746	5,466
Financial Asset, Not Past Due
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	18,702,646
Financial Asset, Not Past Due | Commercial Portfolio Segment [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	5,909,877
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	922,107
Financial Asset, Not Past Due | Paycheck Protection Program [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	7,506
Financial Asset, Not Past Due | Commercial Real Estate, Buildings, Land and Other [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	7,280,086
Financial Asset, Not Past Due | Construction Loans [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	1,672,348
Financial Asset, Not Past Due | Total consumer real estate loans [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	2,440,506	1,832,993
Financial Asset, Not Past Due | Consumer Loan [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	$ 470,216	$ 487,260

Loans (Modification to Borrower

Loans (Modification to Borrowers Experiencing Financial Difficulty) (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Financing Receivable, Troubled Debt Restructuring [Line Items]
Loans, net of unearned discounts	$ 18,824,251	$ 17,154,969
Payment Deferral
Financing Receivable, Troubled Debt Restructuring [Line Items]
Loans, net of unearned discounts	$ 0	$ 1,051
Financing Receivable, Modified in Period, to Total Financing Receivables, Percentage	0%	0%
Combination: Payment Delay and Term Extention
Financing Receivable, Troubled Debt Restructuring [Line Items]
Loans, net of unearned discounts	$ 33,251	$ 0
Financing Receivable, Modified in Period, to Total Financing Receivables, Percentage	0.20%	0%
Extended Maturity and Interest Rate Reduction
Financing Receivable, Troubled Debt Restructuring [Line Items]
Loans, net of unearned discounts	$ 2,092	$ 0
Financing Receivable, Modified in Period, to Total Financing Receivables, Percentage	0%	0%
Commercial Portfolio Segment [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Loans, net of unearned discounts	$ 5,959,133	$ 5,674,798
Commercial Portfolio Segment [Member] | Payment Deferral
Financing Receivable, Troubled Debt Restructuring [Line Items]
Loans, net of unearned discounts	$ 0
Financing Receivable, Modified in Period, to Total Financing Receivables, Percentage	0%
Commercial Portfolio Segment [Member] | Combination: Payment Delay and Term Extention
Financing Receivable, Troubled Debt Restructuring [Line Items]
Loans, net of unearned discounts	$ 13,813
Financing Receivable, Modified in Period, to Total Financing Receivables, Percentage	0.20%
Commercial Portfolio Segment [Member] | Extended Maturity and Interest Rate Reduction
Financing Receivable, Troubled Debt Restructuring [Line Items]
Loans, net of unearned discounts	$ 0
Financing Receivable, Modified in Period, to Total Financing Receivables, Percentage	0%
Commercial Real Estate, Buildings, Land and Other [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Loans, net of unearned discounts	$ 7,301,920	6,706,078
Commercial Real Estate, Buildings, Land and Other [Member] | Payment Deferral
Financing Receivable, Troubled Debt Restructuring [Line Items]
Loans, net of unearned discounts	$ 0	$ 1,051
Financing Receivable, Modified in Period, to Total Financing Receivables, Percentage	0%	0%
Commercial Real Estate, Buildings, Land and Other [Member] | Combination: Payment Delay and Term Extention
Financing Receivable, Troubled Debt Restructuring [Line Items]
Loans, net of unearned discounts	$ 19,438	$ 0
Financing Receivable, Modified in Period, to Total Financing Receivables, Percentage	0.30%	0%
Commercial Real Estate, Buildings, Land and Other [Member] | Extended Maturity and Interest Rate Reduction
Financing Receivable, Troubled Debt Restructuring [Line Items]
Loans, net of unearned discounts	$ 2,092	$ 0
Financing Receivable, Modified in Period, to Total Financing Receivables, Percentage	0%	0%

Loans (Modified Loans by Type o

Loans (Modified Loans by Type of Modification) (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	$ 18,824,251	$ 17,154,969
Payment Deferral
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	0	1,051
Combination: Payment Delay and Term Extention
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	33,251	0
Extended Maturity and Interest Rate Reduction
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	2,092	0
Financial Asset, Equal to or Greater than 90 Days Past Due [Member] | Payment Deferral
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	0	1,051	$ 2,189
Financial Asset, Equal to or Greater than 90 Days Past Due [Member] | Combination: Payment Delay and Term Extention
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	33,251	0	1,556
Financial Asset, Equal to or Greater than 90 Days Past Due [Member] | Extended Maturity and Interest Rate Reduction
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	0	0	0
Charge-offs | Payment Deferral
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts		371	4,278
Charge-offs | Combination: Payment Delay and Term Extention
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts		352	0
Charge-offs | Extended Maturity and Interest Rate Reduction
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts		0	0
Proceeds from sales | Payment Deferral
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts		0
Proceeds from sales | Combination: Payment Delay and Term Extention
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts		1,070
Proceeds from sales | Extended Maturity and Interest Rate Reduction
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts		0
Commercial Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	5,959,133	5,674,798
Commercial Portfolio Segment [Member] | Payment Deferral
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	13,813
Commercial Portfolio Segment [Member] | Extended Maturity and Interest Rate Reduction
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	0
Commercial Portfolio Segment [Member] | Financial Asset, Equal to or Greater than 90 Days Past Due [Member] | Payment Deferral
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	0		1,162
Commercial Portfolio Segment [Member] | Financial Asset, Equal to or Greater than 90 Days Past Due [Member] | Combination: Payment Delay and Term Extention
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	13,813		0
Commercial Portfolio Segment [Member] | Financial Asset, Equal to or Greater than 90 Days Past Due [Member] | Extended Maturity and Interest Rate Reduction
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	0		0
Commercial Real Estate, Buildings, Land and Other [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	7,301,920	6,706,078
Commercial Real Estate, Buildings, Land and Other [Member] | Payment Deferral
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	0	1,051
Commercial Real Estate, Buildings, Land and Other [Member] | Combination: Payment Delay and Term Extention
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	19,438	0
Commercial Real Estate, Buildings, Land and Other [Member] | Extended Maturity and Interest Rate Reduction
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	2,092	0
Commercial Real Estate, Buildings, Land and Other [Member] | Financial Asset, Equal to or Greater than 90 Days Past Due [Member] | Payment Deferral
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	0	1,051	306
Commercial Real Estate, Buildings, Land and Other [Member] | Financial Asset, Equal to or Greater than 90 Days Past Due [Member] | Combination: Payment Delay and Term Extention
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	19,438	0	1,556
Commercial Real Estate, Buildings, Land and Other [Member] | Financial Asset, Equal to or Greater than 90 Days Past Due [Member] | Extended Maturity and Interest Rate Reduction
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	0	0	0
Commercial Real Estate, Buildings, Land and Other [Member] | Charge-offs | Payment Deferral
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts		371
Commercial Real Estate, Buildings, Land and Other [Member] | Charge-offs | Combination: Payment Delay and Term Extention
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts		352
Commercial Real Estate, Buildings, Land and Other [Member] | Charge-offs | Extended Maturity and Interest Rate Reduction
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts		0
Commercial Real Estate, Buildings, Land and Other [Member] | Proceeds from sales | Payment Deferral
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts		0
Commercial Real Estate, Buildings, Land and Other [Member] | Proceeds from sales | Combination: Payment Delay and Term Extention
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts		1,070
Commercial Real Estate, Buildings, Land and Other [Member] | Proceeds from sales | Extended Maturity and Interest Rate Reduction
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts		0
Commercial and Industrial Total Energy Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	$ 935,265	$ 925,729
Commercial and Industrial Total Energy Loans [Member] | Financial Asset, Equal to or Greater than 90 Days Past Due [Member] | Payment Deferral
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts			721
Commercial and Industrial Total Energy Loans [Member] | Financial Asset, Equal to or Greater than 90 Days Past Due [Member] | Combination: Payment Delay and Term Extention
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts			0
Commercial and Industrial Total Energy Loans [Member] | Financial Asset, Equal to or Greater than 90 Days Past Due [Member] | Extended Maturity and Interest Rate Reduction
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts			0
Commercial and Industrial Total Energy Loans [Member] | Charge-offs | Payment Deferral
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts			4,278
Commercial and Industrial Total Energy Loans [Member] | Charge-offs | Combination: Payment Delay and Term Extention
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts			0
Commercial and Industrial Total Energy Loans [Member] | Charge-offs | Extended Maturity and Interest Rate Reduction
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts			$ 0

Loans (Weighted Average Risk Gr

Loans (Weighted Average Risk Grades for All Commercial Loans by Class) (Detail) $ in Thousands	Dec. 31, 2023 USD ($) Grade	Dec. 31, 2022 USD ($) Grade
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	$ 18,824,251	$ 17,154,969
Commercial Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	1,619,306	1,703,185
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	768,246	657,039
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	491,938	498,213
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	364,446	241,997
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	182,089	138,541
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	219,766	195,754
Financing Receivable, Revolving	2,247,752	2,170,182
Loans, net of unearned discounts	$ 5,959,133	$ 5,674,798
Weighted Average Risk Grade | Grade	6.60	6.39
Commercial Portfolio Segment [Member] | Revolving Credit Facility
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade | Grade	6.50	6.26
Commercial Portfolio Segment [Member] | Revolving Loans Converted to Term
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Revolving, Converted to Term Loan	$ 65,590	$ 69,887
Weighted Average Risk Grade | Grade	8.48	7.68
Commercial Portfolio Segment [Member] | 2023
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade | Grade	6.53
Commercial Portfolio Segment [Member] | 2022
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade | Grade	7.05	6.37
Commercial Portfolio Segment [Member] | 2021
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade | Grade	7.26	7.05
Commercial Portfolio Segment [Member] | 2020
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade | Grade	5.87	6.01
Commercial Portfolio Segment [Member] | 2019
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade | Grade	6.01	6.59
Commercial Portfolio Segment [Member] | 2018
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade | Grade		6.87
Commercial Portfolio Segment [Member] | Prior Years
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade | Grade	6.04	5.55
Commercial and Industrial Total Energy Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	$ 277,722	$ 352,224
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	61,500	100,862
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	74,631	5,312
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	3,835	8,659
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	6,876	3,078
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	4,541	2,913
Financing Receivable, Revolving	495,329	408,022
Loans, net of unearned discounts	$ 935,265	$ 925,729
Weighted Average Risk Grade | Grade	6.05	5.67
Commercial and Industrial Total Energy Loans [Member] | Revolving Credit Facility
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade | Grade	5.75	5.18
Commercial and Industrial Total Energy Loans [Member] | Revolving Loans Converted to Term
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Revolving, Converted to Term Loan	$ 10,831	$ 44,659
Weighted Average Risk Grade | Grade	7.33	5.69
Commercial and Industrial Total Energy Loans [Member] | 2023
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade | Grade	6.19
Commercial and Industrial Total Energy Loans [Member] | 2022
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade | Grade	7.07	6.09
Commercial and Industrial Total Energy Loans [Member] | 2021
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade | Grade	6	5.65
Commercial and Industrial Total Energy Loans [Member] | 2020
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade | Grade	6.99	7.65
Commercial and Industrial Total Energy Loans [Member] | 2019
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade | Grade	10.02	9.64
Commercial and Industrial Total Energy Loans [Member] | 2018
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade | Grade		8.02
Commercial and Industrial Total Energy Loans [Member] | Prior Years
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade | Grade	7.07	6.59
Commercial Real Estate, Buildings, Land and Other [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	$ 1,645,223	$ 1,901,888
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	1,785,624	1,528,173
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	1,253,062	1,009,197
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	811,574	745,031
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	522,566	410,327
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	953,768	882,021
Financing Receivable, Revolving	229,733	120,958
Loans, net of unearned discounts	$ 7,301,920	$ 6,706,078
Weighted Average Risk Grade | Grade	7.20	7.09
Commercial Real Estate, Buildings, Land and Other [Member] | Revolving Credit Facility
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade | Grade	7.49	7.38
Commercial Real Estate, Buildings, Land and Other [Member] | Revolving Loans Converted to Term
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Revolving, Converted to Term Loan	$ 100,370	$ 108,483
Weighted Average Risk Grade | Grade	6.77	6.43
Commercial Real Estate, Buildings, Land and Other [Member] | 2023
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade | Grade	7.23
Commercial Real Estate, Buildings, Land and Other [Member] | 2022
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade | Grade	7.18	7.01
Commercial Real Estate, Buildings, Land and Other [Member] | 2021
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade | Grade	7.29	7.26
Commercial Real Estate, Buildings, Land and Other [Member] | 2020
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade | Grade	7.22	7.14
Commercial Real Estate, Buildings, Land and Other [Member] | 2019
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade | Grade	6.90	7.01
Commercial Real Estate, Buildings, Land and Other [Member] | 2018
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade | Grade		7.33
Commercial Real Estate, Buildings, Land and Other [Member] | Prior Years
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade | Grade	7.16	6.94
Construction Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	$ 560,720	$ 666,024
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	576,374	491,563
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	344,641	130,888
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	28,063	2,236
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	296	486
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	1,613	1,726
Financing Receivable, Revolving	169,017	181,180
Loans, net of unearned discounts	$ 1,680,724	$ 1,477,247
Weighted Average Risk Grade | Grade	7.45	7.12
Construction Loans [Member] | Revolving Credit Facility
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade | Grade	7.34	7.23
Construction Loans [Member] | Revolving Loans Converted to Term
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Revolving, Converted to Term Loan	$ 0	$ 3,144
Weighted Average Risk Grade | Grade	0	5.03
Construction Loans [Member] | 2023
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade | Grade	7.44
Construction Loans [Member] | 2022
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade | Grade	7.44	7.29
Construction Loans [Member] | 2021
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade | Grade	7.93	7.03
Construction Loans [Member] | 2020
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade | Grade	2.55	6.43
Construction Loans [Member] | 2019
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade | Grade	7.22	7.04
Construction Loans [Member] | 2018
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade | Grade		6
Construction Loans [Member] | Prior Years
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade | Grade	6.78	6.76
Commercial Real Estate Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	$ 2,205,943	$ 2,567,912
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	2,361,998	2,019,736
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	1,597,703	1,140,085
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	839,637	747,267
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	522,862	410,813
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	955,381	883,747
Financing Receivable, Revolving	398,750	302,138
Loans, net of unearned discounts	$ 8,982,644	$ 8,183,325
Weighted Average Risk Grade | Grade	7.24	7.10
Commercial Real Estate Portfolio Segment [Member] | Revolving Credit Facility
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade | Grade	7.43	7.29
Commercial Real Estate Portfolio Segment [Member] | Revolving Loans Converted to Term
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Revolving, Converted to Term Loan	$ 100,370	$ 111,627
Weighted Average Risk Grade | Grade	6.77	6.39
Commercial Real Estate Portfolio Segment [Member] | 2023
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade | Grade	7.28
Commercial Real Estate Portfolio Segment [Member] | 2022
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade | Grade	7.24	7.08
Commercial Real Estate Portfolio Segment [Member] | 2021
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade | Grade	7.43	7.20
Commercial Real Estate Portfolio Segment [Member] | 2020
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade | Grade	7.07	7.06
Commercial Real Estate Portfolio Segment [Member] | 2019
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade | Grade	6.90	7.01
Commercial Real Estate Portfolio Segment [Member] | 2018
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade | Grade		7.33
Commercial Real Estate Portfolio Segment [Member] | Prior Years
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade | Grade	7.15	6.94
Risk Grade One To Eight [Member] | Commercial Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	$ 1,489,026	$ 1,667,274
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	706,210	618,756
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	450,806	485,908
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	349,744	226,835
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	172,656	123,768
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	206,643	192,791
Financing Receivable, Revolving	2,083,490	2,068,891
Loans, net of unearned discounts	$ 5,499,829	$ 5,435,917
Weighted Average Risk Grade | Grade	6.32	6.24
Risk Grade One To Eight [Member] | Commercial Portfolio Segment [Member] | Revolving Loans Converted to Term
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Revolving, Converted to Term Loan	$ 41,254	$ 51,694
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	270,710	338,050
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	54,185	99,089
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	73,532	4,917
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	3,673	3,138
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	1,819	2,020
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	4,047	2,850
Financing Receivable, Revolving	451,897	393,957
Loans, net of unearned discounts	$ 869,749	$ 887,182
Weighted Average Risk Grade | Grade	5.73	5.44
Risk Grade One To Eight [Member] | Commercial and Industrial Total Energy Loans [Member] | Revolving Loans Converted to Term
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Revolving, Converted to Term Loan	$ 9,886	$ 43,161
Risk Grade One To Eight [Member] | Commercial Real Estate, Buildings, Land and Other [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	1,601,175	1,811,069
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	1,667,750	1,484,811
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	1,186,559	956,567
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	747,289	708,942
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	503,303	360,154
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	874,942	800,944
Financing Receivable, Revolving	214,874	111,778
Loans, net of unearned discounts	$ 6,895,358	$ 6,340,028
Weighted Average Risk Grade | Grade	7.03	6.94
Risk Grade One To Eight [Member] | Commercial Real Estate, Buildings, Land and Other [Member] | Revolving Loans Converted to Term
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Revolving, Converted to Term Loan	$ 99,466	$ 105,763
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	538,072	640,948
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	537,705	489,391
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	264,770	128,788
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	28,063	2,236
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	296	486
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	1,613	1,726
Financing Receivable, Revolving	155,567	163,293
Loans, net of unearned discounts	$ 1,526,086	$ 1,430,012
Weighted Average Risk Grade | Grade	7.27	7.04
Risk Grade One To Eight [Member] | Construction Loans [Member] | Revolving Loans Converted to Term
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Revolving, Converted to Term Loan	$ 0	$ 3,144
Risk Grade Nine [Member] | Commercial Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	57,625	31,275
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	42,618	34,950
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	12,258	3,651
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	4,952	5,400
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	1,641	11,006
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	10,383	1,014
Financing Receivable, Revolving	70,142	54,856
Loans, net of unearned discounts	205,244	146,192
Risk Grade Nine [Member] | Commercial Portfolio Segment [Member] | Revolving Loans Converted to Term
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Revolving, Converted to Term Loan	5,625	4,040
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	1,137	1,561
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	7,315	1,611
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	1,041	166
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	0	562
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	456	748
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	0	0
Financing Receivable, Revolving	17,680	6,434
Loans, net of unearned discounts	27,643	11,112
Risk Grade Nine [Member] | Commercial and Industrial Total Energy Loans [Member] | Revolving Loans Converted to Term
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Revolving, Converted to Term Loan	14	30
Risk Grade Nine [Member] | Commercial Real Estate, Buildings, Land and Other [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	12,173	52,288
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	68,007	13,139
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	28,870	36,264
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	13,250	22,086
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	16,272	17,699
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	23,214	45,590
Financing Receivable, Revolving	11,143	652
Loans, net of unearned discounts	173,470	189,928
Risk Grade Nine [Member] | Commercial Real Estate, Buildings, Land and Other [Member] | Revolving Loans Converted to Term
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Revolving, Converted to Term Loan	541	2,210
Risk Grade Nine [Member] | Construction Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	3,414	12,865
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	35,565	2,100
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	79,871	2,100
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	0	0
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	0	0
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	0	0
Financing Receivable, Revolving	8,252	17,887
Loans, net of unearned discounts	127,102	34,952
Risk Grade Nine [Member] | Construction Loans [Member] | Revolving Loans Converted to Term
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Revolving, Converted to Term Loan	0	0
Risk Grade Ten [Member] | Commercial Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	63,205	2,294
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	2,222	724
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	1,307	845
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	911	4,713
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	4,005	1,341
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	581	114
Financing Receivable, Revolving	35,977	23,880
Loans, net of unearned discounts	109,254	37,596
Risk Grade Ten [Member] | Commercial Portfolio Segment [Member] | Revolving Loans Converted to Term
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Revolving, Converted to Term Loan	1,046	3,685
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	0
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	0	0
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	33	0
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	0	428
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	291	214
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	494	0
Financing Receivable, Revolving	0	0
Loans, net of unearned discounts	818	642
Risk Grade Ten [Member] | Commercial and Industrial Total Energy Loans [Member] | Revolving Loans Converted to Term
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Revolving, Converted to Term Loan	0	0
Risk Grade Ten [Member] | Commercial Real Estate, Buildings, Land and Other [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	7,671	26,688
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	29,278	11,150
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	17,364	3,735
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	34,672	9,008
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	747	29,683
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	3,153	5,221
Financing Receivable, Revolving	3,716	5,535
Loans, net of unearned discounts	96,601	91,020
Risk Grade Ten [Member] | Commercial Real Estate, Buildings, Land and Other [Member] | Revolving Loans Converted to Term
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Revolving, Converted to Term Loan	0	0
Risk Grade Ten [Member] | Construction Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	13,322	859
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	0	72
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	0	0
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	0	0
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	0	0
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	0	0
Financing Receivable, Revolving	3,713	0
Loans, net of unearned discounts	17,035	931
Risk Grade Ten [Member] | Construction Loans [Member] | Revolving Loans Converted to Term
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Revolving, Converted to Term Loan	0	0
Risk Grade Eleven [Member] | Commercial Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	9,450	2,342
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	16,837	1,357
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	25,932	6,720
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	7,854	1,807
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	2,530	1,229
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	1,153	1,644
Financing Receivable, Revolving	58,134	19,582
Loans, net of unearned discounts	125,261	36,963
Risk Grade Eleven [Member] | Commercial Portfolio Segment [Member] | Revolving Loans Converted to Term
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Revolving, Converted to Term Loan	3,371	2,282
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	7,956
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	0	162
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	25	157
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	106	3,145
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	2,989	86
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	0	63
Financing Receivable, Revolving	21,650	0
Loans, net of unearned discounts	25,555	11,569
Risk Grade Eleven [Member] | Commercial and Industrial Total Energy Loans [Member] | Revolving Loans Converted to Term
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Revolving, Converted to Term Loan	785	0
Risk Grade Eleven [Member] | Commercial Real Estate, Buildings, Land and Other [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	4,105	10,199
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	20,589	19,073
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	20,119	12,631
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	16,363	4,778
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	793	2,525
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	51,739	28,841
Financing Receivable, Revolving	0	2,993
Loans, net of unearned discounts	114,071	81,550
Risk Grade Eleven [Member] | Commercial Real Estate, Buildings, Land and Other [Member] | Revolving Loans Converted to Term
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Revolving, Converted to Term Loan	363	510
Risk Grade Eleven [Member] | Construction Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	5,912	11,352
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	3,104	0
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	0	0
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	0	0
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	0	0
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	0	0
Financing Receivable, Revolving	1,485	0
Loans, net of unearned discounts	10,501	11,352
Risk Grade Eleven [Member] | Construction Loans [Member] | Revolving Loans Converted to Term
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Revolving, Converted to Term Loan	0	0
Risk Grade Twelve [Member] | Commercial Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	0	0
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	359	1,052
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	1,635	866
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	950	2,972
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	1,257	1,177
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	1,006	191
Financing Receivable, Revolving	1	673
Loans, net of unearned discounts	17,102	12,521
Risk Grade Twelve [Member] | Commercial Portfolio Segment [Member] | Revolving Loans Converted to Term
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Revolving, Converted to Term Loan	11,894	5,590
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	5,875	3,995
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	0	0
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	0	72
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	56	1,386
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	1,321	10
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	0	0
Financing Receivable, Revolving	1,402	4,571
Loans, net of unearned discounts	8,800	10,840
Risk Grade Twelve [Member] | Commercial and Industrial Total Energy Loans [Member] | Revolving Loans Converted to Term
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Revolving, Converted to Term Loan	146	806
Risk Grade Twelve [Member] | Commercial Real Estate, Buildings, Land and Other [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	17,449	1,049
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	0	0
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	150	0
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	0	217
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	1,451	266
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	720	1,425
Financing Receivable, Revolving	0	0
Loans, net of unearned discounts	19,770	2,957
Risk Grade Twelve [Member] | Commercial Real Estate, Buildings, Land and Other [Member] | Revolving Loans Converted to Term
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Revolving, Converted to Term Loan	0	0
Risk Grade Twelve [Member] | Construction Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	0	0
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	0	0
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	0	0
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	0	0
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	0	0
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	0	0
Financing Receivable, Revolving	0	0
Loans, net of unearned discounts	0	0
Risk Grade Twelve [Member] | Construction Loans [Member] | Revolving Loans Converted to Term
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Revolving, Converted to Term Loan	0	0
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	0
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	0	200
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	0	223
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	35	270
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	0	20
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	0	0
Financing Receivable, Revolving	8	2,300
Loans, net of unearned discounts	2,443	5,609
Risk Grade Thirteen [Member] | Commercial Portfolio Segment [Member] | Revolving Loans Converted to Term
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Revolving, Converted to Term Loan	2,400	2,596
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	662
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	0	0
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	0	0
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	0	0
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	0	0
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	0	0
Financing Receivable, Revolving	2,700	3,060
Loans, net of unearned discounts	2,700	4,384
Risk Grade Thirteen [Member] | Commercial and Industrial Total Energy Loans [Member] | Revolving Loans Converted to Term
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Revolving, Converted to Term Loan	0	662
Risk Grade Thirteen [Member] | Commercial Real Estate, Buildings, Land and Other [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	2,650	595
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	0	0
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	0	0
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	0	0
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	0	0
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	0	0
Financing Receivable, Revolving	0	0
Loans, net of unearned discounts	2,650	595
Risk Grade Thirteen [Member] | Commercial Real Estate, Buildings, Land and Other [Member] | Revolving Loans Converted to Term
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Revolving, Converted to Term Loan	0	0
Risk Grade Thirteen [Member] | Construction Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	0	0
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	0	0
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	0	0
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	0	0
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	0	0
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	0	0
Financing Receivable, Revolving	0	0
Loans, net of unearned discounts	0	0
Risk Grade Thirteen [Member] | Construction Loans [Member] | Revolving Loans Converted to Term
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Revolving, Converted to Term Loan	$ 0	$ 0

Loans (Age Analysis of Past D_2

Loans (Age Analysis of Past Due Consumer Loans, Segregated By Class and Year of Origination) (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	$ 18,824,251	$ 17,154,969
Financing Receivables, 30 to 89 Days Past Due [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	78,100
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	43,505
Financial Asset, Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	121,605
Financial Asset, Not Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	18,702,646
Total consumer real estate loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	2,460,726	1,843,539
Total consumer real estate loans [Member] | Revolving Credit Facility
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	781,601	679,330
Total consumer real estate loans [Member] | Revolving Loans Converted to Term
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	11,335	12,770
Total consumer real estate loans [Member] | Financing Receivables, 30 to 89 Days Past Due [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	12,504	7,856
Total consumer real estate loans [Member] | Financing Receivables, 30 to 89 Days Past Due [Member] | Revolving Credit Facility
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	3,570	565
Total consumer real estate loans [Member] | Financing Receivables, 30 to 89 Days Past Due [Member] | Revolving Loans Converted to Term
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	539	1,202
Total consumer real estate loans [Member] | 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	7,716	2,690
Total consumer real estate loans [Member] | Financial Asset, Equal to or Greater than 90 Days Past Due [Member] | Revolving Credit Facility
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	2,566	347
Total consumer real estate loans [Member] | Financial Asset, Equal to or Greater than 90 Days Past Due [Member] | Revolving Loans Converted to Term
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	3,087	914
Total consumer real estate loans [Member] | Financial Asset, Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	20,220	10,546
Total consumer real estate loans [Member] | Financial Asset, Past Due | Revolving Credit Facility
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	6,136	912
Total consumer real estate loans [Member] | Financial Asset, Past Due | Revolving Loans Converted to Term
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	3,626	2,116
Total consumer real estate loans [Member] | Financial Asset, Not Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	2,440,506	1,832,993
Total consumer real estate loans [Member] | Financial Asset, Not Past Due | Revolving Credit Facility
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	775,465	678,418
Total consumer real estate loans [Member] | Financial Asset, Not Past Due | Revolving Loans Converted to Term
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	7,709	10,654
Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	476,962	492,726
Consumer Loan [Member] | Revolving Credit Facility
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	342,393	372,456
Consumer Loan [Member] | Revolving Loans Converted to Term
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	22,128	23,732
Consumer Loan [Member] | Financing Receivables, 30 to 89 Days Past Due [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	6,495	5,155
Consumer Loan [Member] | Financing Receivables, 30 to 89 Days Past Due [Member] | Revolving Credit Facility
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	2,553	314
Consumer Loan [Member] | Financing Receivables, 30 to 89 Days Past Due [Member] | Revolving Loans Converted to Term
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	158	1,443
Consumer Loan [Member] | 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	251	311
Consumer Loan [Member] | Financial Asset, Equal to or Greater than 90 Days Past Due [Member] | Revolving Credit Facility
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	51	25
Consumer Loan [Member] | Financial Asset, Equal to or Greater than 90 Days Past Due [Member] | Revolving Loans Converted to Term
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	0	194
Consumer Loan [Member] | Financial Asset, Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	6,746	5,466
Consumer Loan [Member] | Financial Asset, Past Due | Revolving Credit Facility
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	2,604	339
Consumer Loan [Member] | Financial Asset, Past Due | Revolving Loans Converted to Term
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	158	1,637
Consumer Loan [Member] | Financial Asset, Not Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	470,216	487,260
Consumer Loan [Member] | Financial Asset, Not Past Due | Revolving Credit Facility
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	339,789	372,117
Consumer Loan [Member] | Financial Asset, Not Past Due | Revolving Loans Converted to Term
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	21,970	22,095
2023 | Total consumer real estate loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	580,379
2023 | Total consumer real estate loans [Member] | Financing Receivables, 30 to 89 Days Past Due [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	874
2023 | Total consumer real estate loans [Member] | 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	0
2023 | Total consumer real estate loans [Member] | Financial Asset, Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	874
2023 | Total consumer real estate loans [Member] | Financial Asset, Not Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	579,505
2023 | Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	70,439
2023 | Consumer Loan [Member] | Financing Receivables, 30 to 89 Days Past Due [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	3,014
2023 | Consumer Loan [Member] | 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	153
2023 | Consumer Loan [Member] | Financial Asset, Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	3,167
2023 | Consumer Loan [Member] | Financial Asset, Not Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	67,272
2022 | Total consumer real estate loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	435,297	404,475
2022 | Total consumer real estate loans [Member] | Financing Receivables, 30 to 89 Days Past Due [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	2,066	793
2022 | Total consumer real estate loans [Member] | 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	512	95
2022 | Total consumer real estate loans [Member] | Financial Asset, Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	2,578	888
2022 | Total consumer real estate loans [Member] | Financial Asset, Not Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	432,719	403,587
2022 | Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	29,373	62,636
2022 | Consumer Loan [Member] | Financing Receivables, 30 to 89 Days Past Due [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	488	2,673
2022 | Consumer Loan [Member] | 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	0	77
2022 | Consumer Loan [Member] | Financial Asset, Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	488	2,750
2022 | Consumer Loan [Member] | Financial Asset, Not Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	28,885	59,886
2021 | Total consumer real estate loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	283,764	314,605
2021 | Total consumer real estate loans [Member] | Financing Receivables, 30 to 89 Days Past Due [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	1,318	1,125
2021 | Total consumer real estate loans [Member] | 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	626	258
2021 | Total consumer real estate loans [Member] | Financial Asset, Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	1,944	1,383
2021 | Total consumer real estate loans [Member] | Financial Asset, Not Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	281,820	313,222
2021 | Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	6,465	21,400
2021 | Consumer Loan [Member] | Financing Receivables, 30 to 89 Days Past Due [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	148	511
2021 | Consumer Loan [Member] | 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	27	2
2021 | Consumer Loan [Member] | Financial Asset, Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	175	513
2021 | Consumer Loan [Member] | Financial Asset, Not Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	6,290	20,887
2020 | Total consumer real estate loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	171,222	195,573
2020 | Total consumer real estate loans [Member] | Financing Receivables, 30 to 89 Days Past Due [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	959	645
2020 | Total consumer real estate loans [Member] | 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	38	28
2020 | Total consumer real estate loans [Member] | Financial Asset, Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	997	673
2020 | Total consumer real estate loans [Member] | Financial Asset, Not Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	170,225	194,900
2020 | Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	3,647	6,603
2020 | Consumer Loan [Member] | Financing Receivables, 30 to 89 Days Past Due [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	66	128
2020 | Consumer Loan [Member] | 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	0	0
2020 | Consumer Loan [Member] | Financial Asset, Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	66	128
2020 | Consumer Loan [Member] | Financial Asset, Not Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	3,581	6,475
2019 | Total consumer real estate loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	59,281	71,659
2019 | Total consumer real estate loans [Member] | Financing Receivables, 30 to 89 Days Past Due [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	537	936
2019 | Total consumer real estate loans [Member] | 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	0	0
2019 | Total consumer real estate loans [Member] | Financial Asset, Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	537	936
2019 | Total consumer real estate loans [Member] | Financial Asset, Not Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	58,744	70,723
2019 | Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	1,247	2,961
2019 | Consumer Loan [Member] | Financing Receivables, 30 to 89 Days Past Due [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	28	51
2019 | Consumer Loan [Member] | 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	20	13
2019 | Consumer Loan [Member] | Financial Asset, Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	48	64
2019 | Consumer Loan [Member] | Financial Asset, Not Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	1,199	2,897
2018 | Total consumer real estate loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts		39,536
2018 | Total consumer real estate loans [Member] | Financing Receivables, 30 to 89 Days Past Due [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss		503
2018 | Total consumer real estate loans [Member] | 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		129
2018 | Total consumer real estate loans [Member] | Financial Asset, Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss		632
2018 | Total consumer real estate loans [Member] | Financial Asset, Not Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss		38,904
2018 | Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts		1,275
2018 | Consumer Loan [Member] | Financing Receivables, 30 to 89 Days Past Due [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss		4
2018 | Consumer Loan [Member] | 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		0
2018 | Consumer Loan [Member] | Financial Asset, Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss		4
2018 | Consumer Loan [Member] | Financial Asset, Not Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss		1,271
Prior Years | Total consumer real estate loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	137,847	125,591
Prior Years | Total consumer real estate loans [Member] | Financing Receivables, 30 to 89 Days Past Due [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	2,641	2,087
Prior Years | Total consumer real estate loans [Member] | 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	887	919
Prior Years | Total consumer real estate loans [Member] | Financial Asset, Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	3,528	3,006
Prior Years | Total consumer real estate loans [Member] | Financial Asset, Not Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	134,319	122,585
Prior Years | Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	1,270	1,663
Prior Years | Consumer Loan [Member] | Financing Receivables, 30 to 89 Days Past Due [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	40	31
Prior Years | Consumer Loan [Member] | 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	0	0
Prior Years | Consumer Loan [Member] | Financial Asset, Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	40	31
Prior Years | Consumer Loan [Member] | Financial Asset, Not Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	$ 1,230	$ 1,632

Loans (Revolving Loans Converte

Loans (Revolving Loans Converted to Term) (Details) - Revolving Loans Converted to Term - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Accounts, Notes, Loans and Financing Receivable [Line Items]
Remaining Revolving Loans Converted to Term During Period	$ 49,851	$ 67,441
Commercial Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Remaining Revolving Loans Converted to Term During Period	28,713	34,247
Commercial and Industrial Total Energy Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Remaining Revolving Loans Converted to Term During Period	6,409	3,295
Commercial Real Estate, Buildings, Land and Other [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Remaining Revolving Loans Converted to Term During Period	4,780	12,174
Construction Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Remaining Revolving Loans Converted to Term During Period	0	3,144
Total consumer real estate loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Remaining Revolving Loans Converted to Term During Period	2,467	5,381
Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Remaining Revolving Loans Converted to Term During Period	$ 7,482	$ 9,200

Loans (Allowance for Credit Los

Loans (Allowance for Credit Loss By Loan Class Calculated in Accordance With CECL Methodology) (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, Allowance for Credit Loss	$ 245,996	$ 227,621
Commercial Portfolio Segment [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, Allowance for Credit Loss	74,006	104,237	$ 72,091	$ 73,843
Commercial and Industrial Total Energy Loans [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, Allowance for Credit Loss	17,814	18,062	17,217	39,553
Commercial Real Estate Portfolio Segment [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, Allowance for Credit Loss	130,598	90,301	144,936	134,892
Total consumer real estate loans [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, Allowance for Credit Loss	13,538	8,004	6,585	7,926
Consumer Loan [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, Allowance for Credit Loss	10,040	7,017	7,837	6,963
Loans Receivable [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, Allowance for Credit Loss	245,996	227,621	$ 248,666	$ 263,177
Modeled Expected Credit Losses [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, Allowance for Credit Loss	92,573	110,292
Modeled Expected Credit Losses [Member] | Commercial Portfolio Segment [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, Allowance for Credit Loss	50,959	61,918
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	7,838	8,531
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	15,443	27,013
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	12,364	7,847
Modeled Expected Credit Losses [Member] | Consumer Loan [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, Allowance for Credit Loss	5,969	4,983
Q-factor adjustments [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, Allowance for Credit Loss	144,897	105,148
Q-factor adjustments [Member] | Commercial Portfolio Segment [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, Allowance for Credit Loss	20,612	36,237
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	7,276	5,148
Q-factor adjustments [Member] | Commercial Real Estate Portfolio Segment [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, Allowance for Credit Loss	112,505	61,572
Q-factor adjustments [Member] | Total consumer real estate loans [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, Allowance for Credit Loss	433	157
Q-factor adjustments [Member] | Consumer Loan [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, Allowance for Credit Loss	4,071	2,034
Specific Valuation Allowances [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, Allowance for Credit Loss	8,526	12,181
Specific Valuation Allowances [Member] | Commercial Portfolio Segment [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, Allowance for Credit Loss	2,435	6,082
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	4,383
Specific Valuation Allowances [Member] | Commercial Real Estate Portfolio Segment [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, Allowance for Credit Loss	2,650	1,716
Specific Valuation Allowances [Member] | Total consumer real estate loans [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, Allowance for Credit Loss	741	0
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 Allowance fo

Loans (Activity in Allowance for Loan Losses by Portfolio Segment) (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Allowance for Credit Loss, Beginning Balance	$ 227,621
Financing Receivable, Allowance for Credit Loss, Ending Balance	245,996	$ 227,621
Commercial Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Allowance for Credit Loss, Beginning Balance	104,237	72,091	$ 73,843
Financing Receivable, Credit Loss, Expense (Reversal)	(16,709)	34,479	(2,160)
Financing Receivable, Allowance for Credit Loss, Writeoff	(18,315)	(6,575)	(5,513)
Financing Receivable, Allowance for Credit Loss, Recovery	4,793	4,242	5,921
Allowance for Loan and Lease Losses Write-offs, Net	(13,522)	(2,333)	408
Financing Receivable, Allowance for Credit Loss, Ending Balance	74,006	104,237	72,091
Commercial And Industrial Energy Financing Receivable [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Allowance for Credit Loss, Beginning Balance	18,062	17,217	39,553
Financing Receivable, Credit Loss, Expense (Reversal)	(1,067)	(313)	(19,207)
Financing Receivable, Allowance for Credit Loss, Writeoff	(518)	(371)	(5,331)
Financing Receivable, Allowance for Credit Loss, Recovery	1,337	1,529	2,202
Allowance for Loan and Lease Losses Write-offs, Net	819	1,158	(3,129)
Financing Receivable, Allowance for Credit Loss, Ending Balance	17,814	18,062	17,217
Commercial Real Estate Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Allowance for Credit Loss, Beginning Balance	90,301	144,936	134,892
Financing Receivable, Credit Loss, Expense (Reversal)	40,889	(54,775)	8,101
Financing Receivable, Allowance for Credit Loss, Writeoff	(955)	(702)	(399)
Financing Receivable, Allowance for Credit Loss, Recovery	363	842	2,342
Allowance for Loan and Lease Losses Write-offs, Net	(592)	140	1,943
Financing Receivable, Allowance for Credit Loss, Ending Balance	130,598	90,301	144,936
Total consumer real estate loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Allowance for Credit Loss, Beginning Balance	8,004	6,585	7,926
Financing Receivable, Credit Loss, Expense (Reversal)	6,736	1,813	(3,061)
Financing Receivable, Allowance for Credit Loss, Writeoff	(2,883)	(912)	(829)
Financing Receivable, Allowance for Credit Loss, Recovery	1,681	518	2,549
Allowance for Loan and Lease Losses Write-offs, Net	(1,202)	(394)	1,720
Financing Receivable, Allowance for Credit Loss, Ending Balance	13,538	8,004	6,585
Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Allowance for Credit Loss, Beginning Balance	7,017	7,837	6,963
Financing Receivable, Credit Loss, Expense (Reversal)	23,012	13,517	10,230
Financing Receivable, Allowance for Credit Loss, Writeoff	(31,260)	(24,388)	(18,614)
Financing Receivable, Allowance for Credit Loss, Recovery	11,271	10,051	9,258
Allowance for Loan and Lease Losses Write-offs, Net	(19,989)	(14,337)	(9,356)
Financing Receivable, Allowance for Credit Loss, Ending Balance	10,040	7,017	7,837
Loans Receivable [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Allowance for Credit Loss, Beginning Balance	227,621	248,666	263,177
Financing Receivable, Credit Loss, Expense (Reversal)	52,861	(5,279)	(6,097)
Financing Receivable, Allowance for Credit Loss, Writeoff	(53,931)	(32,948)	(30,686)
Financing Receivable, Allowance for Credit Loss, Recovery	19,445	17,182	22,272
Allowance for Loan and Lease Losses Write-offs, Net	(34,486)	(15,766)	(8,414)
Financing Receivable, Allowance for Credit Loss, Ending Balance	$ 245,996	$ 227,621	$ 248,666

Loans (Gross Charge-Offs By Yea

Loans (Gross Charge-Offs By Year of Origination) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Nonperforming Financial Instruments [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	$ 25,974	$ 6,301
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	359	1,510
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	1,785	1,161
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	1,079	4,845
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	6,310	1,473
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	2,209	1,700
Financing Receivable, Revolving	5,711	10,604
Financing Receivable, Revolving, Converted to Term Loan	17,480	10,239
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	24,302
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	6,537
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	1,322
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	170
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	184
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	460
Financing Receivable, Revolving	14,084
Financing Receivable, Revolving, Converted to Term Loan	6,872
Commercial Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	1,619,306	1,703,185
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	768,246	657,039
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	491,938	498,213
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	364,446	241,997
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	182,089	138,541
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	219,766	195,754
Financing Receivable, Revolving	2,247,752	2,170,182
Financing Receivable, Allowance for Credit Loss, Writeoff	18,315	6,575	$ 5,513
Commercial Portfolio Segment [Member] | Nonperforming Financial Instruments [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	0	0
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	359	1,252
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	1,635	1,089
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	985	3,242
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	1,257	1,197
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	1,006	191
Financing Receivable, Revolving	9	2,973
Financing Receivable, Revolving, Converted to Term Loan	14,294	8,186
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	124
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	1,704
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	754
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	157
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	183
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	38
Financing Receivable, Revolving	9,511
Financing Receivable, Revolving, Converted to Term Loan	5,844
Commercial and Industrial Total Energy Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	277,722	352,224
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	61,500	100,862
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	74,631	5,312
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	3,835	8,659
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	6,876	3,078
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	4,541	2,913
Financing Receivable, Revolving	495,329	408,022
Financing Receivable, Allowance for Credit Loss, Writeoff	518	371	5,331
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	5,875	4,657
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	0	0
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	0	72
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	56	1,386
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	1,321	10
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	0	0
Financing Receivable, Revolving	4,102	7,631
Financing Receivable, Revolving, Converted to Term Loan	146	1,468
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
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	518
Commercial Real Estate, Buildings, Land and Other [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	1,645,223	1,901,888
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	1,785,624	1,528,173
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	1,253,062	1,009,197
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	811,574	745,031
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	522,566	410,327
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	953,768	882,021
Financing Receivable, Revolving	229,733	120,958
Financing Receivable, Allowance for Credit Loss, Writeoff	216
Commercial Real Estate, Buildings, Land and Other [Member] | Nonperforming Financial Instruments [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	20,099	1,644
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	0	0
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	150	0
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	0	217
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	1,451	266
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	720	1,425
Financing Receivable, Revolving	0	0
Financing Receivable, Revolving, Converted to Term Loan	0	0
Commercial Real Estate, Buildings, Land and Other [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	6
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	146
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	64
Financing Receivable, Revolving	0
Financing Receivable, Revolving, Converted to Term Loan	0
Construction Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	560,720	666,024
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	576,374	491,563
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	344,641	130,888
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	28,063	2,236
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	296	486
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	1,613	1,726
Financing Receivable, Revolving	169,017	181,180
Financing Receivable, Allowance for Credit Loss, Writeoff	739
Construction Loans [Member] | Nonperforming Financial Instruments [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	0	0
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	0	0
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	0	0
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	0	0
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	0	0
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	0	0
Financing Receivable, Revolving	0	0
Financing Receivable, Revolving, Converted to Term Loan	0	0
Construction 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	739
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]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Allowance for Credit Loss, Writeoff	2,883	912	829
Total consumer real estate loans [Member] | Nonperforming Financial Instruments [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	0	0
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	0	258
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	0	0
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	38	0
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	2,281	0
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	483	84
Financing Receivable, Revolving	1,600	0
Financing Receivable, Revolving, Converted to Term Loan	3,040	585
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	118
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	281
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	348
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	329
Financing Receivable, Revolving	1,807
Financing Receivable, Revolving, Converted to Term Loan	0
Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Allowance for Credit Loss, Writeoff	31,260	24,388	18,614
Consumer Loan [Member] | Nonperforming Financial Instruments [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	0	0
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	0	0
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	0	0
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	0	0
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	0	0
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	0	0
Financing Receivable, Revolving	0	0
Financing Receivable, Revolving, Converted to Term Loan	0	0
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	23,321
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	4,546
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	74
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	13
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	1
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	29
Financing Receivable, Revolving	2,766
Financing Receivable, Revolving, Converted to Term Loan	510
Loans Receivable [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Allowance for Credit Loss, Writeoff	$ 53,931	$ 32,948	$ 30,686

Loans (Investment in Loans Rela

Loans (Investment in Loans Related to Allowance for Loan Loss by Portfolio Segment Disaggregated Based on Impairment Methodology) (Detail) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	$ 18,824,251	$ 17,154,969
Commercial Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	5,959,133	5,674,798
Commercial and Industrial Total Energy Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	935,265	925,729
Paycheck Protection Program [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	9,521	34,852
Commercial Real Estate, Buildings, Land and Other [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	7,301,920	6,706,078
Construction Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	1,680,724	1,477,247
Total consumer real estate loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	2,460,726	1,843,539
Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	476,962	492,726
Specific Valuation Allowances [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Portion of allowance for loan losses	8,526	12,181
Specific Valuation Allowances [Member] | Commercial Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Portion of allowance for loan losses	2,435	6,082
Specific Valuation Allowances [Member] | Commercial and Industrial Total Energy Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Portion of allowance for loan losses	2,700	4,383
Specific Valuation Allowances [Member] | Paycheck Protection Program [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Portion of allowance for loan losses	0	0
Specific Valuation Allowances [Member] | Commercial Real Estate, Buildings, Land and Other [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Portion of allowance for loan losses	2,650	1,716
Specific Valuation Allowances [Member] | Construction Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Portion of allowance for loan losses	0	0
Specific Valuation Allowances [Member] | Total consumer real estate loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Portion of allowance for loan losses	741	0
Specific Valuation Allowances [Member] | Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Portion of allowance for loan losses	0	0
Loans Individually Evaluated for Impairment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	58,631	52,576
Loans Individually Evaluated for Impairment [Member] | Commercial Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	18,670	18,980
Loans Individually Evaluated for Impairment [Member] | Commercial and Industrial Total Energy Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	11,353	15,058
Loans Individually Evaluated for Impairment [Member] | Paycheck Protection Program [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	0	0
Loans Individually Evaluated for Impairment [Member] | Commercial Real Estate, Buildings, Land and Other [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	21,373	17,711
Loans Individually Evaluated for Impairment [Member] | Construction Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	0	0
Loans Individually Evaluated for Impairment [Member] | Total consumer real estate loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	7,235	827
Loans Individually Evaluated for Impairment [Member] | Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	$ 0	$ 0

Premises and Equipment (Narrati

Premises and Equipment (Narrative) (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Property, Plant and Equipment [Line Items]
Depreciation	$ 60,600	$ 57,400	$ 55,100
Operating Lease, Rent Expense	50,500	47,700	45,600
Operating Lease, Right-of-Use Asset	280,502	288,816
Operating lease, payments	32,100	32,900
Premises and Equipment
Property, Plant and Equipment [Line Items]
Operating Lease, Right-of-Use Asset	280,500	288,800
Other Liabilities [Member]
Property, Plant and Equipment [Line Items]
Operating lease, liability	316,392	321,900
Partnership Interest [Member]
Property, Plant and Equipment [Line Items]
Operating Lease, Rent Expense	$ 337	$ 327	$ 322

Premises and Equipment (Premise

Premises and Equipment (Premises and Equipment) (Detail) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Property, Plant and Equipment [Abstract]
Land	$ 191,594	$ 170,938
Buildings	581,745	521,280
Technology, furniture and equipment	262,666	236,440
Leasehold improvements	230,642	209,398
Construction and projects in progress	36,910	39,506
Operating lease, right-of-use asset	280,502	288,816
Premises and equipment, Gross	1,584,059	1,466,378
Less accumulated depreciation and amortization	(394,026)	(363,683)
Total premises and equipment, net	$ 1,190,033	$ 1,102,695

Premises and Equipment (Lease C

Premises and Equipment (Lease Commitments, Components of Lease Expense) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Property, Plant and Equipment [Line Items]
Amortization of lease right-of-use assets	$ 34,137	$ 33,285
Short-term lease expense	2,576	2,208
Non-lease components (including taxes, insurance, common maintenance, etc.)	13,811	12,172
Total operating lease expense, excluding rent	$ 50,524	$ 47,665

Premises and Equipment Future M

Premises and Equipment Future Minimum Lease Payments Due Under non-Cancelable Operating Leases (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Property, Plant and Equipment [Line Items]
2024	$ 34,712
2025	36,030
2026	35,891
2027	34,359
2028	32,319
Thereafter	218,152
Total undiscounted operating lease liability	391,463
Imputed interest	$ 75,071
Weighted-average lease term in years	12 years 10 months 17 days
Weighted-average discount rate	3.32%
Other Liabilities [Member]
Property, Plant and Equipment [Line Items]
Operating lease, liability	$ 316,392	$ 321,900

Deposits (Schedule of Deposits)

Deposits (Schedule of Deposits) (Detail) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Deposit Liability [Line Items]
Non-interest-bearing demand deposits	$ 14,926,094	$ 17,598,234
Savings and interest checking	10,512,637	12,333,675
Money market accounts	10,997,279	12,227,247
Time accounts	5,484,558	1,795,040
Total Interest-bearing deposits	26,994,474	26,355,962
Total deposits	$ 41,920,568	$ 43,954,196

Deposits (Additional Informatio

Deposits (Additional Information About Corporation's Deposits) (Detail) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Deposit Liability [Line Items]
Deposits from foreign sources (primarily Mexico)	$ 1,061,701	$ 1,048,943
Non-interest-bearing public funds deposits	14,926,094	17,598,234
Interest-bearing public funds deposits	26,994,474	26,355,962
Total deposits not covered by deposit insurance	22,393,786	23,839,797
Time deposits not covered by deposit insurance	2,339,716	430,128
Deposits from certain directors, executive officers and their affiliates	115,798	153,083
Public Funds [Member]
Deposit Liability [Line Items]
Non-interest-bearing public funds deposits	675,016	788,040
Interest-bearing public funds deposits	$ 630,455	$ 758,761

Deposits (Scheduled Maturities

Deposits (Scheduled Maturities of Time Deposits) (Detail) $ in Thousands	Dec. 31, 2023 USD ($)
Deposits [Abstract]
2024	$ 5,286,064
2025	28,829
2026	169,665
Time deposits, Total	$ 5,484,558

Deposits (Scheduled Maturitie_2

Deposits (Scheduled Maturities of Time Deposits Not Covered By Deposit Insurance) (Detail) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Deposits [Abstract]
Due within 3 months or less	$ 1,991,080
Due after 3 months and within 6 months	139,435
Due after 6 months and within 12 months	167,732
Due after 12 months	41,469
Time deposits liability, above US Insurance Limit Total	$ 2,339,716	$ 430,128

Borrowed Funds (Narrative) (Det

Borrowed Funds (Narrative) (Detail) $ in Thousands		3 Months Ended	12 Months Ended
	Mar. 17, 2017 USD ($)	Dec. 31, 2022 USD ($)	Dec. 31, 2023 USD ($) quarter	Dec. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)	Dec. 31, 2004 USD ($)
Borrowed Funds [Line Items]
Federal funds purchased		$ 51,650	$ 14,200	$ 51,650
Repurchase agreements		4,660,641	4,127,188	4,660,641
Subordinated notes		99,335	99,491	99,335
Junior subordinated deferrable interest debentures		123,069	123,127	123,069
Principal payments on long-term borrowings			$ 0	0	$ 13,403
Maximum number of quarterly periods by which the corporation has the right to defer interest payments on junior subordinated deferrable interest debentures | quarter			20
Cullen Frost Capital Trust II [Member]
Borrowed Funds [Line Items]
Maturity date						Mar. 01, 2034
Proceeds from Issuance of Trust Preferred Securities						$ 120,000
Proceeds from issuance of Common Equity Securities						$ 3,700
Cullen Frost Capital Trust II [Member] | SOFR
Borrowed Funds [Line Items]
Floating rate 3 month Libor plus margin						1.81%
Cullen Frost Capital Trust II [Member] | LIBOR [Member]
Borrowed Funds [Line Items]
Floating rate 3 month Libor plus margin						1.55%
Federal Funds Purchased [Member] | Minimum [Member]
Borrowed Funds [Line Items]
Short term debt maturity period			1 day
Federal Funds Purchased [Member] | Maximum [Member]
Borrowed Funds [Line Items]
Short term debt maturity period			90 days
Securities Loaned or Sold under Agreements to Repurchase [Member] | Minimum [Member]
Borrowed Funds [Line Items]
Short term debt maturity period			30 days
Securities Loaned or Sold under Agreements to Repurchase [Member] | Maximum [Member]
Borrowed Funds [Line Items]
Short term debt maturity period			90 days
Subordinated Debt [Member]
Borrowed Funds [Line Items]
Subordinated notes	$ 100,000
Subordinated notes interest rate	4.50%
Maturity date	Mar. 17, 2027
Unamortized debt issuance cost related to note		665	$ 509	665
Junior Subordinated Deferrable Interest Debenture [Member] | Cullen Frost Capital Trust II [Member]
Borrowed Funds [Line Items]
Unamortized debt issuance cost related to note		643	585	643
Junior subordinated deferrable interest debentures		123,700	$ 123,700	$ 123,700		$ 123,700
Junior Subordinated Deferrable Interest Debenture [Member] | Cullen Frost Capital Trust II [Member] | SOFR
Borrowed Funds [Line Items]
Floating rate 3 month Libor plus margin			7.22%
Junior Subordinated Deferrable Interest Debenture [Member] | Cullen Frost Capital Trust II [Member] | LIBOR [Member]
Borrowed Funds [Line Items]
Floating rate 3 month Libor plus margin				6.31%
Junior Subordinated Deferrable Interest Debenture [Member] | WNB Capital Trust I [Member]
Borrowed Funds [Line Items]
Principal payments on long-term borrowings		$ 13,400

Off-Balance Sheet Arrangements

Off-Balance Sheet Arrangements Commitments Guarantees and Contingencies (Narrative) (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Commitments And Guarantees [Line Items]
Off-Balance-Sheet, Credit Loss, Liability, Change in Method, Credit Loss Expense (Reversal)	$ (19,000)
Credit card guarantees	5,500	$ 8,000
Fully collateralized credit card guarantees	762	897
Frost Wealth Advisors [Member]
Commitments And Guarantees [Line Items]
Fair value of off-balance sheet managed and custody assets	$ 47,200,000	$ 42,900,000	$ 43,300,000

Off-Balance-Sheet Arrangement_3

Off-Balance-Sheet Arrangements, Commitments, Guarantees and Contingencies (Financial Instruments With Off-Balance-Sheet Risk) (Detail) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Standby Letters of Credit [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Financial instruments with off- balance-sheet risk	$ 438,635	$ 383,851
Deferred Standby Letter of Credit Fees [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Financial instruments with off- balance-sheet risk	2,912	2,236
Commitments to Extend Credit [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Financial instruments with off- balance-sheet risk	$ 12,195,073	$ 12,137,957

Off-Balance-Sheet Arrangement_4

Off-Balance-Sheet Arrangements, Commitments, Guarantees and Contingencies - Credit Losses on Off-Balance-Sheet Commitments (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Fair Value Disclosures [Abstract]
Off-Balance Sheet, Credit Loss, Liability, Beginning Balance	$ 58,593	$ 50,314	$ 44,152
Off-Balance Sheet, Credit Loss, Liability, Credit Loss Expense (Reversal)	(6,842)	8,279	6,162
Off-Balance Sheet, Credit Loss, Liability, Ending Balance	$ 51,751	$ 58,593	$ 50,314

Capital and Regulatory Matter_2

Capital and Regulatory Matters (Narrative) (Detail)					12 Months Ended
	Jan. 24, 2024 USD ($)	Jan. 25, 2023 USD ($)	Nov. 19, 2020 USD ($) $ / shares shares	Mar. 17, 2017 USD ($)	Dec. 31, 2023 USD ($) quarter $ / shares Rate shares	Dec. 31, 2022 USD ($) $ / shares Rate shares	Dec. 31, 2021 USD ($) shares	Jan. 01, 2019 Rate
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Credit loss optional transitional period under CECL					5 years
CECL Transition Amount					$ 30,800,000	$ 46,200,000
Subordinated notes					$ 99,491,000	$ 99,335,000
Treasury stock, shares, acquired | shares					436,765	0	0
Treasury Stock, Value, Acquired, Cost Method					$ (42,720,000)	$ (4,391,000)	$ (3,864,000)
Excise Tax Percentage | Rate					1%
Aggregate dividends available for payment without prior regulatory approval					$ 1,100,000,000
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]
Non-cumulative perpetual preferred stock, dividend rate percentage			4.45%
Preferred Stock, Shares Issued | shares			150,000		150,000	150,000
Preferred Stock, Aggregate Liquidation Preference, Value			$ 150,000,000		$ 1,000	$ 1,000
Preferred Stock, Par or Stated Value Per Share | $ / shares			$ 0.01		$ 0.01	$ 0.01
Liquidation preference per share | $ / shares			$ 1,000
Number of Preferred Stock equivalent depositary shares | shares			40
Payments of Stock Issuance Costs			$ 4,500,000
Proceeds from issuance of preferred stock			$ 145,500,000
Series B Preferred Stock Equivalent Depositary Shares Member [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Liquidation preference per share | $ / shares			$ 25
Subordinated Debt [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Subordinated notes				$ 100,000,000
Subordinated notes interest rate				4.50%
Per year percentage of decreases in permissible portion of Subordinate Note included in Total Capital					20%
Final years of the term of the notes					5 years
Cullen/Frost [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Additional Tier 1 Capital beyond Common Equity Tier 1					$ 145,500,000	$ 145,500,000
Non-cumulative perpetual preferred stock, dividend rate percentage			4.45%
Common Equity Tier One Risk Based Capital To Risk Weighted Assets Minimum Capital Required Basel III Phase In Schedule, Ratio								4.50%
Capital Conservation Buffer								2.50%
Effective common equity tier one capital to risk weighted assets, ratio upon full implementation					7%	7%		7%
Tier One Risk Based Capital Required for Capital Adequacy to Risk Weighted Assets | Rate								6%
Effective tier one capital ratio, upon full implementation					8.50%	8.50%		8.50%
Minimum ratio of Total capital to risk weighted assets | Rate					15.18%	14.84%		8%
Tier one risk based capital to risk weighted assets, ratio upon full implementation					10.50%	10.50%		10.50%
Minimum leverage ratio					4%	4%		4%
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					$ 120,000,000	$ 120,000,000
Cullen/Frost [Member] | Subordinated Debt [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Permissible Portion Of Subordinated Note Included In Capital					60,000,000	80,000,000
Frost Bank [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Additional Tier 1 Capital beyond Common Equity Tier 1					$ 0	$ 0
Common Equity Tier One Risk Based Capital To Risk Weighted Assets Minimum Capital Required Basel III Phase In Schedule, Ratio								4.50%
Capital Conservation Buffer								2.50%
Effective common equity tier one capital to risk weighted assets, ratio upon full implementation					7%	7%		7%
Tier One Risk Based Capital Required for Capital Adequacy to Risk Weighted Assets | Rate								6%
Effective tier one capital ratio, upon full implementation					8.50%	8.50%		8.50%
Minimum ratio of Total capital to risk weighted assets | Rate					14.20%	13.80%		8%
Tier one risk based capital to risk weighted assets, ratio upon full implementation					10.50%	10.50%		10.50%
Minimum leverage ratio					4%	4%		4%
stock repurchase 2024 plan | Subsequent Event
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Share repurchase authorized amount	$ 150,000,000
Stock repurchase program, period in force	1 year
stock repurchase 2023 plan
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Share repurchase authorized amount		$ 100,000,000
Stock repurchase program, period in force		1 year
stock repurchase 2023 plan | Treasury Stock, Common
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Treasury stock, shares, acquired | shares					400,868
Treasury Stock, Value, Acquired, Cost Method					$ (39,000,000)
Share awards vesting | Treasury Stock, Common
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Treasury stock, shares, acquired | shares					35,897	31,351	31,317
Treasury Stock, Value, Acquired, Cost Method					$ (3,500,000)	$ (4,400,000)	$ (3,900,000)

Regulatory Matters (Actual and

Regulatory Matters (Actual and Required Capital Ratios) (Detail) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022	Jan. 01, 2019
Cullen/Frost [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Common Equity Tier One to Risk-Weighted Assets, Actual, Capital Amount	$ 4,036,945	$ 3,751,200
Common Equity Tier One Risk-Based Capital Ratio, Actual	13.25%	12.85%
Common Equity Tier One Capital Required For Capital Adequacy Minimum Capital Required Plus Capital Conservation Buffer, Capital Amount	$ 2,132,516	$ 2,042,876
Common Equity Tier One Risk Based Capital To Risk Weighted Assets Minimum Capital Required Plus Capital Conservation Buffer, Ratio	7%	7%	7%
Tier 1 Capital to Risk-Weighted Assets, Actual, Capital Amount	$ 4,182,397	$ 3,896,652
Tier 1 Capital to Risk-Weighted Assets, Actual, Ratio	13.73%	13.35%
Tier One Risk Based Capital Required For Capital Adequacy Minimum Capital Required Plus Capital Conservation Buffer, Capital Amount	$ 2,589,484	$ 2,480,635
Tier One Risk Based Capital Required for Capital Adequacy to Risk Weighted Assets Minimum Capital Required Plus Capital Conservation Buffer, Ratio	8.50%	8.50%	8.50%
Tier 1 Capital to Risk-Weighted Assets, Required to be Considered Well Capitalized, Capital Amount	$ 1,827,871	$ 1,751,036
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	$ 4,625,760	$ 4,330,982
Total Capital to Risk-Weighted Assets, Actual, Ratio	15.18%	14.84%	8%
Capital Required for Capital Adequacy Minimum Capital Required Plus Capital Conservation Buffer, Capital Amount	$ 3,198,774	$ 3,064,313
Capital Required for Capital Adequacy to Risk Weighted Assets Minimum Capital Required Plus Capital Conservation Buffer, Ratio	10.50%	10.50%	10.50%
Total Capital to Risk-Weighted Assets, Required to be Considered Well Capitalized, Capital Amount	$ 3,046,452	$ 2,918,394
Total Capital to Risk-Weighted Assets, Required to be Considered Well Capitalized, Ratio	10%	10%
Leverage Ratio, Actual, Capital Amount	$ 4,182,397	$ 3,896,652
Leverage Ratio, Actual, Ratio	8.35%	7.29%
Tier One Leverage Capital Required for Capital Adequacy Minimum Capital Required Plus Capital Conservation Buffer, Capital Amount	$ 2,003,020	$ 2,136,680
Tier One Leverage Capital Required for Capital Adequacy to Average Assets Minimum Capital Required Plus Capital Conservation Buffer, Ratio	4%	4%	4%
Frost Bank [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Common Equity Tier One to Risk-Weighted Assets, Actual, Capital Amount	$ 4,057,111	$ 3,789,056
Common Equity Tier One Risk-Based Capital Ratio, Actual	13.33%	13%
Common Equity Tier One Capital Required For Capital Adequacy Minimum Capital Required Plus Capital Conservation Buffer, Capital Amount	$ 2,129,784	$ 2,040,388
Common Equity Tier One Risk Based Capital To Risk Weighted Assets Minimum Capital Required Plus Capital Conservation Buffer, Ratio	7%	7%	7%
Common Equity Tier One Capital Required To Be Well Capitalized, Capital Amount	$ 1,977,656	$ 1,894,646
Common Equity Tier One Risk-Based Capital Ratio, Well Capitalized, Minimum	6.50%	6.50%
Tier 1 Capital to Risk-Weighted Assets, Actual, Capital Amount	$ 4,057,111	$ 3,789,056
Tier 1 Capital to Risk-Weighted Assets, Actual, Ratio	13.33%	13%
Tier One Risk Based Capital Required For Capital Adequacy Minimum Capital Required Plus Capital Conservation Buffer, Capital Amount	$ 2,586,166	$ 2,477,614
Tier One Risk Based Capital Required for Capital Adequacy to Risk Weighted Assets Minimum Capital Required Plus Capital Conservation Buffer, Ratio	8.50%	8.50%	8.50%
Tier 1 Capital to Risk-Weighted Assets, Required to be Considered Well Capitalized, Capital Amount	$ 2,434,038	$ 2,331,872
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	$ 4,320,474	$ 4,023,386
Total Capital to Risk-Weighted Assets, Actual, Ratio	14.20%	13.80%	8%
Capital Required for Capital Adequacy Minimum Capital Required Plus Capital Conservation Buffer, Capital Amount	$ 3,194,676	$ 3,060,583
Capital Required for Capital Adequacy to Risk Weighted Assets Minimum Capital Required Plus Capital Conservation Buffer, Ratio	10.50%	10.50%	10.50%
Total Capital to Risk-Weighted Assets, Required to be Considered Well Capitalized, Capital Amount	$ 3,042,548	$ 2,914,841
Total Capital to Risk-Weighted Assets, Required to be Considered Well Capitalized, Ratio	10%	10%
Leverage Ratio, Actual, Capital Amount	$ 4,057,111	$ 3,789,056
Leverage Ratio, Actual, Ratio	8.10%	7.09%
Tier One Leverage Capital Required for Capital Adequacy Minimum Capital Required Plus Capital Conservation Buffer, Capital Amount	$ 2,003,152	$ 2,136,316
Tier One Leverage Capital Required for Capital Adequacy to Average Assets Minimum Capital Required Plus Capital Conservation Buffer, Ratio	4%	4%	4%
Leverage Ratio, Required to be Considered Well Capitalized, Capital Amount	$ 2,503,940	$ 2,670,395
Leverage Ratio, Required to be Considered Well Capitalized, Ratio	5%	5%

Earnings Per Common Share (Basi

Earnings Per Common Share (Basic and Diluted Earnings Per Common Share) (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Earnings Per Share [Abstract]
Net income	$ 597,973	$ 579,150	$ 443,079
Less: Preferred stock dividends	6,675	6,675	7,157
Net income available to common shareholders	591,298	572,475	435,922
Less: Earnings allocated to participating securities	6,283	5,210	3,881
Net earnings allocated to common stock	585,015	567,265	432,041
Distributed earnings allocated to common stock	229,749	207,924	187,202
Undistributed earnings allocated to common stock	$ 355,266	$ 359,341	$ 244,839
Weighted-average shares outstanding for basic earnings per common share	64,204,239	64,156,870	63,612,658
Dilutive effect of stock compensation	200,594	363,648	489,462
Weighted-average shares outstanding for diluted earnings per common share	64,404,833	64,520,518	64,102,120

Employee Benefit Plans (Narrati

Employee Benefit Plans (Narrative) (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Percentage of equity investments in mutual fund	85%
Net periodic benefit cost, Expected return on plan assets	7%	7.25%	7.25%
Expected defined benefit plans contribution within a year	$ 1,100,000
Participants contribution eligible for match	100%
Defined contribution plan, cost	$ 32,300,000	$ 28,000,000	$ 23,800,000
Number of stock plans	3
Dividends, share-based compensation	$ 0.92	$ 0.87	$ 0.75
Weighted-average risk-free interest rate	5.01%	4.45%	0.77%
Options awarded during period	0	0	0
Performance Shares [Member]
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Share-based compensation arrangement by share-based payment award, number of shares available for grant	205,090
Performance Shares [Member] | Pro Forma [Member]
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Granted in period, number of shares/units	66,471	35,015	30,723
Equity Securities [Member]
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Target asset allocation percentage	31%
Fixed Income Securities [Member]
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Target asset allocation percentage	63%
Two Thousand Fifteen Plan [Member] | Stock Options [Member]
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Expiration Period	10 years
Vesting period of options awarded, years	4 years
Two Thousand Fifteen Plan [Member] | Non Vested Stock Awards and Stock Units [Member]
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Expiration Period	10 years
Two Thousand Fifteen Plan [Member] | Non Vested Stock Awards and Stock Units [Member] | 2021
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Vesting period of options awarded, years	3 years
Two Thousand Fifteen Plan [Member] | Non Vested Stock Awards and Stock Units [Member] | Prior to 2021
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Vesting period of options awarded, years	4 years
Two Thousand Fifteen Plan [Member] | Non Vested Stock Awards and Stock Units [Member] | 2023
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Vesting period of options awarded, years	3 years
Two Thousand Fifteen Plan [Member] | Non Vested Stock Awards and Stock Units [Member] | 2022
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Vesting period of options awarded, years	3 years
Minimum [Member]
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Maximum annual contributions per employee, percent	2%
Maximum [Member]
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Maximum annual contributions per employee, percent	50%
Employer matching contribution, percent of employees' gross pay	6%
Maximum [Member] | Performance Shares [Member]
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Granted in period, number of shares/units	99,710	52,527	46,086

Employee Benefit Plans (Combine

Employee Benefit Plans (Combined Activity in Corporations Defined Benefit Pension Plans) (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Retirement Benefits [Abstract]
Fair value of plan assets at beginning of year	$ 161,823	$ 197,747	$ 182,088
Actual return on plan assets	22,477	(26,108)	24,908
Employer contributions	1,105	1,114	1,236
Benefits paid	(10,794)	(10,930)	(10,485)
Fair value of plan assets at end of year	174,611	161,823	197,747
Benefit obligation at beginning of year	143,944	185,925	197,593
Interest cost	6,983	4,017	3,341
Actuarial (gain) loss	2,239	(35,068)	(4,524)
Benefits paid	(10,794)	(10,930)	(10,485)
Benefit obligation at end of year	142,372	143,944	185,925
Funded status of the plan at end of year and accrued benefit (liability) recognized	32,239	17,879	11,822
Accumulated benefit obligation at end of year	$ 142,372	$ 143,944	$ 185,925

Employee Benefit Plans (Disaggr

Employee Benefit Plans (Disaggregated Information Related to Corporations Defined Benefit Pension Plans) (Detail) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Defined Benefit Plan Disclosure [Line Items]
Projected benefit obligation	$ 142,372	$ 143,944	$ 185,925	$ 197,593
Accumulated benefit obligation	142,372	143,944	185,925
Fair value of plan assets	174,611	161,823	197,747	$ 182,088
Funded status of the plan at end of year and accrued benefit (liability) recognized	32,239	17,879	$ 11,822
Retirement Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Projected benefit obligation	130,750	131,648
Accumulated benefit obligation	130,750	131,648
Fair value of plan assets	174,611	161,823
Funded status of the plan at end of year and accrued benefit (liability) recognized	43,861	30,175
Restoration Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Projected benefit obligation	11,622	12,296
Accumulated benefit obligation	11,622	12,296
Fair value of plan assets	0	0
Funded status of the plan at end of year and accrued benefit (liability) recognized	$ (11,622)	$ (12,296)

Employee Benefit Plans (Net Per

Employee Benefit Plans (Net Periodic Benefit Cost (Benefit)) (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Retirement Benefits [Abstract]
Expected return on plan assets, net of expenses	$ (10,959)	$ (13,966)	$ (12,839)
Interest cost on projected benefit obligation	6,983	4,017	3,341
Net amortization and deferral	3,479	2,964	6,116
Net periodic expense (benefit)	$ (497)	$ (6,985)	$ (3,382)

Employee Benefit Plans (Defined

Employee Benefit Plans (Defined Benefit Pension Plans Recognized as Component of Other Comprehensive Income) (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Defined Benefit Plan Disclosure [Line Items]
Net actuarial gain (loss)	$ 12,757	$ (2,041)	$ 22,709
Deferred tax (expense) benefit	(2,679)	429	(4,769)
Other comprehensive income (loss), net of tax	$ 10,078	$ (1,612)	$ 17,940

Employee Benefit Plans (Defin_2

Employee Benefit Plans (Defined Benefit Pension Plans not Recognized as Component of Combined Net Period Benefit Cost) (Detail) - Accumulated Defined Benefit Plans Adjustment Attributable to Parent [Member] - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Defined Benefit Plan Disclosure [Line Items]
Net actuarial loss	$ (30,918)	$ (43,675)
Deferred tax benefit	6,493	9,172
Amounts included in accumulated other comprehensive loss, net of tax	$ (24,425)	$ (34,503)

Employee Benefit Plans (Weighte

Employee Benefit Plans (Weighted-Average Assumptions Used to Determine Benefit Obligations) (Detail)	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Retirement Benefits [Abstract]
Benefit obligations, Discount rate	4.95%	5.14%	2.79%
Net periodic benefit cost, Discount rate	5.14%	2.79%	2.43%
Net periodic benefit cost, Expected return on plan assets	7%	7.25%	7.25%

Employee Benefit Plans (Fair Va

Employee Benefit Plans (Fair Value of Plan Assets) (Detail) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 174,611	$ 161,823	$ 197,747	$ 182,088
Mutual Fund [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	38,793	154,391
US Treasury [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	26,633	0
Common Stock [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	13,001	0
Cash and Cash Equivalents [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	1,241	7,432
Corporate Bond Securities [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	58,669	0
US Government Agencies Debt Securities [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	7,041	0
States and Political Subdivisions [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 29,233	$ 0

Employee Benefit Plans (Expecte

Employee Benefit Plans (Expected Future Benefit Payments Related to Defined Benefit Plans) (Detail) $ in Thousands	Dec. 31, 2023 USD ($)
Retirement Benefits [Abstract]
2024	$ 12,022
2025	11,966
2026	11,967
2027	11,874
2028	11,511
2029 through 2033	50,461
Total defined benefit plan expected future benefit payments	$ 109,801

Employee Benefit Plans (Summary

Employee Benefit Plans (Summary of Activity in Corporation's Active Stock Plans) (Detail) - $ / shares	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock options exercised, number of shares	(267,357)	(399,810)	(987,758)
Director deferred stock units outstanding [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Ending balance, number of shares/units	54,164	45,661	56,301
Beginning balance, number of shares/units	45,661	56,301	52,860
Ending balance, weighted-average grant-date fair value	$ 89.71	$ 87.15	$ 79.21
Beginning balance, weighted-average grant-date fair value	$ 87.15	$ 79.21	$ 75.47
Granted in period, number of shares/units	8,503	5,382	5,940
Granted in period, weighted-average grant-date fair value	$ 103.47	$ 133.67	$ 117.90
Stock awards exercised/vested in period, number of shares	0	(16,022)	(2,499)
Stock awards exercised/vested in period, weighted-average grant date fair value	$ 0	$ 74.89	$ 92.03
Non-Vested Stock Awards/ Stock Units Outstanding [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Ending balance, number of shares/units	566,806	465,319	449,337
Beginning balance, number of shares/units	465,319	449,337	470,359
Ending balance, weighted-average grant-date fair value	$ 99.77	$ 105.36	$ 93.05
Beginning balance, weighted-average grant-date fair value	$ 105.36	$ 93.05	$ 86.24
Granted in period, number of shares/units	217,561	119,176	95,258
Granted in period, weighted-average grant-date fair value	$ 85.39	$ 142.56	$ 130.36
Stock awards exercised/vested in period, number of shares	(108,920)	(97,154)	(88,250)
Stock awards exercised/vested in period, weighted-average grant date fair value	$ 94	$ 94.81	$ 98.90
Forfeited/expired in period, number of shares/units	(7,154)	(6,040)	(28,030)
Forfeited/expired in period, weighted-average grant date fair value	$ 114.53	$ 93.28	$ 87.08
Share-based Payment Arrangement, Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Ending balance, number of shares	485,941	616,227	877,681
Beginning balance, number of shares	616,227	877,681	1,739,559
Ending balance, weighted-average exercise price	$ 71.25	$ 71.27	$ 69.02
Beginning balance, weighted-average exercise price	$ 71.27	$ 69.02	$ 66.11
Stock options exercised, number of shares	(130,286)	(261,454)	(861,878)
Stock options exercised, weighted-average exercise price	$ 71.37	$ 63.72	$ 63.14
Maximum [Member] | Performance Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Ending balance, number of shares/units	267,054	213,749	202,460
Beginning balance, number of shares/units	213,749	202,460	201,257
Ending balance, weighted-average grant-date fair value	$ 89.99	$ 96.20	$ 84.71
Beginning balance, weighted-average grant-date fair value	$ 96.20	$ 84.71	$ 77.18
Granted in period, number of shares/units	99,710	52,527	46,086
Granted in period, weighted-average grant-date fair value	$ 74.71	$ 133.40	$ 121.46
Stock awards exercised/vested in period, number of shares	(28,151)	(25,180)	(35,131)
Stock awards exercised/vested in period, weighted-average grant date fair value	$ 85.74	$ 87.18	$ 92.27
Forfeited/expired in period, number of shares/units	(18,254)	(16,058)	(9,752)
Forfeited/expired in period, weighted-average grant date fair value	$ 85.74	$ 87.18	$ 75.70

Employee Benefit Plans (Options

Employee Benefit Plans (Options Outstanding and Exercisable) (Detail) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2023 USD ($) $ / shares shares
65.01 - 70.00 [Member]
Share-based Payment Arrangement, Option, Exercise Price Range [Line Items]
Range of Exercise Prices, Minimum	$ 65.01
Range of Exercise Prices, Maximum	70
75.01 - 80.00 [Member]
Share-based Payment Arrangement, Option, Exercise Price Range [Line Items]
Range of Exercise Prices, Minimum	75.01
Range of Exercise Prices, Maximum	$ 80
Options Outstanding [Member]
Share-based Payment Arrangement, Option, Exercise Price Range [Line Items]
Number of Shares, Options Outstanding | shares	485,941
Weighted-Average Exercise Price, Options Outstanding	$ 71.25
Weighted- Average Remaining Contractual Life in Years	1 year 4 months 13 days
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Intrinsic Value | $	$ 18,098
Options Outstanding [Member] | 65.01 - 70.00 [Member]
Share-based Payment Arrangement, Option, Exercise Price Range [Line Items]
Number of Shares, Options Outstanding | shares	270,031
Weighted-Average Exercise Price, Options Outstanding	$ 65.11
Weighted- Average Remaining Contractual Life in Years	1 year 9 months 18 days
Options Outstanding [Member] | 75.01 - 80.00 [Member]
Share-based Payment Arrangement, Option, Exercise Price Range [Line Items]
Number of Shares, Options Outstanding | shares	215,910
Weighted-Average Exercise Price, Options Outstanding	$ 78.92
Weighted- Average Remaining Contractual Life in Years	9 months 25 days
Options Exercisable [Member]
Share-based Payment Arrangement, Option, Exercise Price Range [Line Items]
Number of Shares, Options Exercisable | shares	485,941
Weighted-Average Exercise Price, Options Exercisable	$ 71.25
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Intrinsic Value | $	$ 18,098
Options Exercisable [Member] | 65.01 - 70.00 [Member]
Share-based Payment Arrangement, Option, Exercise Price Range [Line Items]
Number of Shares, Options Exercisable | shares	270,031
Weighted-Average Exercise Price, Options Exercisable	$ 65.11
Options Exercisable [Member] | 75.01 - 80.00 [Member]
Share-based Payment Arrangement, Option, Exercise Price Range [Line Items]
Number of Shares, Options Exercisable | shares	215,910
Weighted-Average Exercise Price, Options Exercisable	$ 78.92

Employee Benefit Plans (Shares

Employee Benefit Plans (Shares Issued in Connection with Stock Compensation Awards) (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Retirement Benefits [Abstract]
New shares issued from available authorized shares	49,887	118,389	0
Shares issued from available treasury stock	217,470	281,421	987,758
Total	267,357	399,810	987,758
Proceeds from stock option exercises	$ 9,299	$ 16,659	$ 54,417
Intrinsic value of stock options exercised	3,614	19,616	43,904
Fair value of restricted/director deferred stock units vested	$ 13,445	$ 19,308	$ 15,751

Employee Benefit Plans (Stock-B

Employee Benefit Plans (Stock-Based Compensation Expense) (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Share-Based Payment Arrangement, Expense	$ 24,590	$ 18,322	$ 12,753
Income tax benefit	4,120	2,969	1,713
Non-Vested Stock Awards/ Stock Units Outstanding [Member]
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Non-vested restricted stock units	16,734	13,162	9,977
Director deferred stock units outstanding [Member]
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Non-vested restricted stock units	880	720	700
Performance Shares [Member]
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Non-vested restricted stock units	$ 6,976	$ 4,440	$ 2,076

Employee Benefit Plans (Unrecog

Employee Benefit Plans (Unrecognized Stock-Based Compensation Expense) (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2023 USD ($)
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Non-vested stock awards/stock units	$ 22,665
Performance stock units	9,784
Total	$ 32,449
Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Period for Recognition	2 years 1 month 17 days
Employee service share-based compensation, Performance stock units,compensation cost not yet recognized,period for recognition	2 years 3 months

Other Non-Interest Income and_3

Other Non-Interest Income and Expense (Narrative) (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Other Income and Expenses [Abstract]
Minimum percentage of the aggregate total net interest income and total non interest income required for amounts to be stated separately	1%	1%	1%
Payment for services provided by related party	$ 1,300	$ 545	$ 257

Other Non-Interest Income and_4

Other Non-Interest Income and Expense (Other Non-Interest Income and Expense) (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Other Income and Expenses [Abstract]
Other	$ 54,941	$ 45,217	$ 48,528
Total other non-interest income	54,941	45,217	48,528
Professional services	53,932	40,908	34,747
Advertising, promotions and public relations	48,608	39,994	34,539
Other	126,827	113,799	102,868
Total other non-interest expense	$ 229,367	$ 194,701	$ 172,154

Income Taxes (Narrative) (Detai

Income Taxes (Narrative) (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Income Tax Disclosure [Abstract]
U.S. federal statutory income tax rate	21%	21%	21%
Unrecognized tax benefits	$ 0	$ 0	$ 0
Valuation allowance	$ 0	$ 0

Income Taxes (Income Tax Expens

Income Taxes (Income Tax Expense) (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Income Tax Disclosure [Abstract]
Current income tax expense	$ 129,229	$ 94,595	$ 38,675
Deferred income tax expense (benefit)	(14,829)	(4,918)	7,784
Income tax expense, as reported	$ 114,400	$ 89,677	$ 46,459
Effective tax rate	16.10%	13.40%	9.50%

Income Taxes (Income Tax Comput

Income Taxes (Income Tax Computed by Applying U.S. Federal Statutory Income Tax Rate) (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Income Tax Disclosure [Abstract]
Income tax expense computed at the statutory rate	$ 149,598	$ 140,454	$ 102,803
Effect of tax-exempt interest	(43,114)	(50,602)	(50,740)
Tax benefit on dividends paid in our 401k plan	(2,135)	(1,854)	(1,764)
Net tax benefit from stock-based compensation	(894)	(4,602)	(7,877)
Non-deductible FDIC premiums	5,263	3,277	2,629
Non-deductible compensation	2,591	2,250	1,773
Non-deductible meals and entertainment	1,692	683	625
Tax basis adjustment of premises and equipment	0	0	(1,026)
Other	1,399	71	36
Income tax expense, as reported	$ 114,400	$ 89,677	$ 46,459

Income Taxes (Schedule of Defer

Income Taxes (Schedule of Deferred Tax Assets and Liabilities) (Detail) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Income Tax Disclosure [Abstract]
Net unrealized loss on securities available for sale and transferred securities	$ 291,023	$ 349,237
Lease liabilities under operating leases	66,442	67,608
Allowance for credit losses	62,592	60,137
Bonus accrual	9,680	11,204
FDIC deposit insurance special assessment	9,468	0
Stock-based compensation	7,712	6,622
Net actuarial loss on defined benefit post-retirement benefit plans	6,493	9,172
Deferred loan and lease origination fees	4,129	3,675
Other	5,892	6,109
Total gross deferred tax assets	463,431	513,764
Right-of-use assets under operating leases	(58,905)	(60,651)
Premises and equipment	(42,640)	(45,647)
Intangible assets	(18,106)	(17,732)
Defined benefit post-retirement benefit plans	(13,073)	(12,730)
Other	(2,368)	(2,601)
Total gross deferred tax liabilities	(135,092)	(139,361)
Deferred Tax Assets, Net	$ 328,339	$ 374,403

Other Comprehensive Income (L_3

Other Comprehensive Income (Loss) (Component of Other Comprehensive Income (Loss)) (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Equity [Abstract]
Securities available for sale and transferred securities, Change in net unrealized gain/loss during the period, before tax amount	$ 277,926	$ (2,143,567)	$ (231,355)
Securities available for sale and transferred securities, Change in net unrealized gain on securities transferred to held to maturity, before tax amount	(649)	(737)	(971)
Securities available for sale and transferred securities, Reclassification adjustment for net (gains) losses included in net income, before tax amount	(66)	0	(69)
Total securities available for sale and transferred securities before tax amount	277,211	(2,144,304)	(232,395)
Change in the net actuarial gain/loss before tax amount	9,278	(5,005)	16,593
Reclassification adjustment for net amortization of actuarial gain/loss included in net income as a component of net periodic cost (benefit) before tax amount	3,479	2,964	6,116
Total defined-benefit post-retirement benefit plans	12,757	(2,041)	22,709
Other comprehensive income (loss), before tax	289,968	(2,146,345)	(209,686)
Securities available for sale and transferred securities, Change in net unrealized gain/loss during the period, tax expense (benefit)	58,364	(450,149)	(48,585)
Securities available for sale and transferred securities, change in net unrealized gain on securities transfers to held-to-maturity, tax expense benefit	(136)	(155)	(204)
Securities available for sale and transferred securities, Reclassification adjustment for net (gains) losses included in net income, tax expense (benefit)	(14)		(14)
Total securities available for sale and transferred securities, tax expense (benefit)	58,214	(450,304)	(48,803)
Change in the net actuarial gain/loss, tax expense (benefit)	1,948	(1,051)	3,485
Reclassification adjustment for net amortization of actuarial gain/loss included in net income as a componet of net periodic cost (benefit) , tax expense (benefit)	731	622	1,284
Total defined-benefit post-retirement benefit plans, tax expense (benefit)	2,679	(429)	4,769
Total other comprehensive income, tax expense (benefit)	60,893	(450,733)	(44,034)
Securities available for sale and transferred securities, change in net unrealized gain/loss during the period, net of tax amount	219,562	(1,693,418)	(182,770)
Securities available for sale and transferred securities. change in net unrealized gain on securities transfers to held-to-maturity, net of tax amount	(513)	(582)	(767)
Securities available for sale and securities transferred, reclassification adjustment for net (gains) losses included in net income, net of tax amount	(52)		(55)
Total securities available for sale and transferred securities, net of tax amount	218,997	(1,694,000)	(183,592)
Change in the net actuarial gain/loss, net of tax amount	7,330	(3,954)	13,108
Reclassification adjustment for net amortization of actuarial gain/loss included in net income as a componet of net periodic cost (benefit), net of tax amount	2,748	2,342	4,832
Total defined-benefit post-retirement benefit plans, net of tax amount	10,078	(1,612)	17,940
Other comprehensive income (loss), net of tax	$ 229,075	$ (1,695,612)	$ (165,652)

Other Comprehensive Income (Sch

Other Comprehensive Income (Schedule of Accumulated Other Comprehensive Income, Net of Tax) (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance	$ (1,348,294)
Net other comprehensive income (loss) during period	229,075	$ (1,695,612)	$ (165,652)
Ending Balance	(1,119,219)	(1,348,294)
Available-for-sale Securities [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance	(1,313,791)	380,209	563,801
Other comprehensive income (loss) before reclassification	219,049	(1,694,000)	(183,537)
Reclassification of amounts included in net income	(52)	0	(55)
Net other comprehensive income (loss) during period	218,997	(1,694,000)	(183,592)
Ending Balance	(1,094,794)	(1,313,791)	380,209
Defined Benefit Plans [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance	(34,503)	(32,891)	(50,831)
Other comprehensive income (loss) before reclassification	7,330	(3,954)	13,108
Reclassification of amounts included in net income	2,748	2,342	4,832
Net other comprehensive income (loss) during period	10,078	(1,612)	17,940
Ending Balance	(24,425)	(34,503)	(32,891)
AOCI Attributable to Parent [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance	(1,348,294)	347,318	512,970
Other comprehensive income (loss) before reclassification	226,379	(1,697,954)	(170,429)
Reclassification of amounts included in net income	2,696	2,342	4,777
Net other comprehensive income (loss) during period	229,075	(1,695,612)	(165,652)
Ending Balance	$ (1,119,219)	$ (1,348,294)	$ 347,318

Derivative Financial Instrume_3

Derivative Financial Instruments (Narrative) (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Derivative [Line Items]
Weighted-average strike rate for outstanding interest rate caps	3.69%
Approximate credit exposure related to swaps with bank customers	$ 21,400
Cash collateral on deposit with other financial institutions	8,600	$ 3,200
Interest Rate Swaps With Upstream Financial Institution Counterparties [Member]
Derivative [Line Items]
Approximate credit exposure related to swaps with bank customers	2,500
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) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Designated as Hedging Instrument [Member] | Financial Institution Counterparties Loan Lease Interest Rate Swaps Assets [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Notional Amount	$ 0	$ 1,614
Estimated Fair Value	0	19
Not Designated as Hedging Instrument [Member] | Financial Institution Counterparties Loan Lease Interest Rate Swaps Assets [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Notional Amount	1,040,659	1,165,812
Estimated Fair Value	58,486	70,416
Not Designated as Hedging Instrument [Member] | Financial Institution Counterparties Loan Lease Interest Rate Swaps Liabilities [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability, Notional Amount	617,266	78,798
Estimated Fair Value	(20,293)	(1,102)
Not Designated as Hedging Instrument [Member] | Financial Institution Counterparties Loan Lease Interest Rate Caps Assets [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Notional Amount	275,000	246,442
Estimated Fair Value	11,747	15,256
Not Designated as Hedging Instrument [Member] | Customer Counterparties Loan Lease Interest Rate Swaps Assets [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Notional Amount	617,266	53,570
Estimated Fair Value	20,482	1,102
Not Designated as Hedging Instrument [Member] | Customer Counterparties Loan Lease Interest Rate Swaps Liabilities [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability, Notional Amount	1,040,659	1,175,563
Estimated Fair Value	(58,485)	(79,175)
Not Designated as Hedging Instrument [Member] | Customer Counterparties Loan Lease Interest Rate Caps Liabilities [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability, Notional Amount	275,000	246,442
Estimated Fair Value	$ (11,747)	$ (15,256)

Derivative Financial Instrume_5

Derivative Financial Instruments (Schedule of Weighted-Average Rates Paid and Received for Interest Rate Swaps Outstanding) (Detail)	Dec. 31, 2023
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	4.72%
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	5.22%
Customer Counterparties [Member] | Weighted Average Interest Rate Paid [Member]
Short-duration Insurance Contracts, Discounted Liabilities [Line Items]
Non-hedging interest rate swaps - customer counterparties	5.22%
Customer Counterparties [Member] | Weighted-Average Interest Rate Received [Member]
Short-duration Insurance Contracts, Discounted Liabilities [Line Items]
Non-hedging interest rate swaps - customer counterparties	4.72%

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	Dec. 31, 2023 USD ($) MMBTU bbl	Dec. 31, 2022 USD ($) bbl MMBTU
Financial Institution Counterparties [Member] | Oil Commodity Derivative [Member]
Derivative Instruments [Line Items]
Oil/Natural Gas Derivative Assets Notional Amount | bbl	5,601	4,024
Oil/Natural Gas Derivative Assets, Estimated Fair Value	$ 37,667	$ 27,082
Oil/Natural Gas Derivative Liabilities Notional Amount | bbl	4,581	6,068
Oil/Natural Gas Derivative Liabilities, Estimated Fair Value	$ (18,500)	$ (53,579)
Financial Institution Counterparties [Member] | Natural Gas Commodity Derivative [Member]
Derivative Instruments [Line Items]
Oil/Natural Gas Derivative Assets Notional Amount | MMBTU	17,363	16,539
Oil/Natural Gas Derivative Assets, Estimated Fair Value	$ 11,822	$ 6,220
Oil/Natural Gas Derivative Liabilities Notional Amount | MMBTU	6,462	15,682
Oil/Natural Gas Derivative Liabilities, Estimated Fair Value	$ (2,499)	$ (19,138)
Customer Counterparties [Member] | Oil Commodity Derivative [Member]
Derivative Instruments [Line Items]
Oil/Natural Gas Derivative Assets Notional Amount | bbl	4,618	6,068
Oil/Natural Gas Derivative Assets, Estimated Fair Value	$ 18,722	$ 54,219
Oil/Natural Gas Derivative Liabilities Notional Amount | bbl	5,564	4,024
Oil/Natural Gas Derivative Liabilities, Estimated Fair Value	$ (36,877)	$ (26,551)
Customer Counterparties [Member] | Natural Gas Commodity Derivative [Member]
Derivative Instruments [Line Items]
Oil/Natural Gas Derivative Assets Notional Amount | MMBTU	6,462	15,682
Oil/Natural Gas Derivative Assets, Estimated Fair Value	$ 2,499	$ 19,164
Oil/Natural Gas Derivative Liabilities Notional Amount | MMBTU	17,363	16,539
Oil/Natural Gas Derivative Liabilities, Estimated Fair Value	$ (11,571)	$ (6,124)

Derivative Financial Instrume_7

Derivative Financial Instruments Derivative Financial Instruments (Schedule of Notional Amount and Fair Value of Open Foreign Currency Forward Contract) (Details) € in Thousands, $ in Thousands, $ in Thousands	Dec. 31, 2023 USD ($)	Dec. 31, 2023 EUR (€)	Dec. 31, 2023 CAD ($)	Dec. 31, 2022 USD ($)	Dec. 31, 2022 EUR (€)	Dec. 31, 2022 CAD ($)
Financial Institution Counterparties [Member] | Other Assets [Member] | Not Designated as Hedging Instrument [Member]
Derivative Counter Party [Line Items]
Forward Contracts - Assets, Notional Amount		€ 0	$ 250		€ 875	$ 0
Financial Institution Counterparties [Member] | Other Liabilities [Member] | Not Designated as Hedging Instrument [Member]
Derivative Counter Party [Line Items]
Forward Contracts Liability, Notional Amount		3,000	250		875	0
Customer Counterparties [Member] | Other Assets [Member] | Not Designated as Hedging Instrument [Member]
Derivative Counter Party [Line Items]
Forward Contracts - Assets, Notional Amount		3,000	250		875	0
Customer Counterparties [Member] | Other Liabilities [Member] | Not Designated as Hedging Instrument [Member]
Derivative Counter Party [Line Items]
Forward Contracts Liability, Notional Amount		€ 0	$ 250		€ 875	$ 0
GBP Foreign Exchange Forward [Member] | Financial Institution Counterparties [Member]
Derivative Counter Party [Line Items]
Forward Contracts - Assets Estimated Fair Value	$ 0			$ 1
Forward Contracts, Liability Estimated Fair Value	(14)			(10)
GBP Foreign Exchange Forward [Member] | Customer Counterparties [Member]
Derivative Counter Party [Line Items]
Forward Contracts - Assets Estimated Fair Value	16			10
Forward Contracts, Liability Estimated Fair Value	0			(1)
Foreign Exchange Forward [Member] | Financial Institution Counterparties [Member]
Derivative Counter Party [Line Items]
Forward Contracts - Assets Estimated Fair Value	1			0
Forward Contracts, Liability Estimated Fair Value	(5)			0
Foreign Exchange Forward [Member] | Customer Counterparties [Member]
Derivative Counter Party [Line Items]
Forward Contracts - Assets Estimated Fair Value	5			0
Forward Contracts, Liability Estimated Fair Value	$ 0			$ 0

Derivative Financial Instrume_8

Derivative Financial Instruments (Schedule of Amounts Related to Interest Rate Derivatives Designated as Hedges of Fair Value) (Detail) - Designated as Hedging Instrument [Member] - Commercial Loan/Lease Interest Rate Swaps [Member] - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Interest Income on Loans [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount included in income or expense	$ 16	$ (7)	$ (91)
Other Non-Interest Expense [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount included in income or expense	$ 0	$ 6	$ 10

Derivative Financial Instrume_9

Derivative Financial Instruments (Schedule of Amounts Related to Non-Hedging Interest Rate and Commodity Derivatives) (Detail) - Not Designated as Hedging Instrument [Member] - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Interest Rate Contract [Member] | Other Non-Interest Income [Member]
Other Non Interest Income Non Hedging Interest Rate Derivatives [Line Items]
Amount included in income or expense	$ 6,982	$ 1,742	$ 4,285
Interest Rate Contract [Member] | Other Non-Interest Expense [Member]
Other Non Interest Income Non Hedging Interest Rate Derivatives [Line Items]
Amount included in income or expense	0	0	(1)
Commodity Contract [Member]
Other Non Interest Income Non Hedging Interest Rate Derivatives [Line Items]
Amount included in income or expense	1,889	2,297	4,052
Foreign Exchange Contract [Member]
Other Non Interest Income Non Hedging Interest Rate Derivatives [Line Items]
Amount included in income or expense	$ 30	$ 63	$ 39

Balance Sheet Offsetting - Fina

Balance Sheet Offsetting - Financial Instruments Eligible for Offset Consolidated Balance Sheet (Detail) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Gross Amount Recognized, Derivative, Financial Assets	$ 119,723	$ 118,994
Gross Amount Offset, Derivatives, Financial Assets	0	0
Net Amount Recognized, Derivative, Financial Assets	119,723	118,994
Gross Amount Recognized, Resell Agreements, Financial Assets	84,650	87,150
Gross Amount Offset, Resell Agreements, Financial Assets	0	0
Net Amount Recognized, Resell Agreements, Financial Assets	84,650	87,150
Gross Amount Recognized, Financial Assets	204,373	206,144
Gross Amount Offset, Financial Assets	0	0
Net Amount Recognized, Financial Assets	204,373	206,144
Gross Amount Recognized, Derivative, Financial Liabilities	41,311	73,829
Gross Amount Offset, Derivative, Financial Liabilities	0	0
Net Amount Recognized, Derivative, Financial Liabilities	41,311	73,829
Gross Amount Recognized, Repurchase Agreements, Financial Liabilities	4,127,188	4,660,641
Gross Amount Offset, Repurchase Agreements, Financial Liabilities	0	0
Net Amount Recognized, Repurchase Agreements, Financial Liabilities	4,127,188	4,660,641
Gross Amount Recognized, Financial Liabilities	4,168,499	4,734,470
Gross Amount Offset, Financial Liabilities	0	0
Net Amount Recognized, Financial Liabilities	4,168,499	4,734,470
Loan Lease Interest Rate Swaps And Caps [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Gross Amount Recognized, Derivative, Financial Assets	70,233	85,691
Gross Amount Offset, Derivatives, Financial Assets	0	0
Net Amount Recognized, Derivative, Financial Assets	70,233	85,691
Commodity Swaps And Options [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Gross Amount Recognized, Derivative, Financial Assets	49,489	33,302
Gross Amount Offset, Derivatives, Financial Assets	0	0
Net Amount Recognized, Derivative, Financial Assets	49,489	33,302
Gross Amount Recognized, Derivative, Financial Liabilities	20,999	72,717
Gross Amount Offset, Derivative, Financial Liabilities	0	0
Net Amount Recognized, Derivative, Financial Liabilities	20,999	72,717
Foreign Currency Forward Contracts [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Gross Amount Recognized, Derivative, Financial Assets	1	1
Gross Amount Offset, Derivatives, Financial Assets	0	0
Net Amount Recognized, Derivative, Financial Assets	1	1
Gross Amount Recognized, Derivative, Financial Liabilities	19	10
Gross Amount Offset, Derivative, Financial Liabilities	0	0
Net Amount Recognized, Derivative, Financial Liabilities	19	10
Loan Lease Interest Rate Swaps [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Gross Amount Recognized, Derivative, Financial Liabilities	20,293	1,102
Gross Amount Offset, Derivative, Financial Liabilities	0	0
Net Amount Recognized, Derivative, Financial Liabilities	$ 20,293	$ 1,102

Balance Sheet Offsetting - Fi_2

Balance Sheet Offsetting - Financial Instruments Derivative Assets Liabilities and Resell Agreements Net of Amount Not Offset (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Net Amount Recognized, Derivatives, Financial Assets	$ 119,723	$ 118,994
Gross Amounts Not Offset, Financial Instruments, Total Derivatives, Financial Assets	(32,431)	(62,528)
Gross Amounts Not Offset, Collateral, Derivatives, Financial Assets	(84,839)	(55,968)
Net Amount, Derivatives, Financial Assets	2,453	498
Net Amount Recognized, Resell Agreements, Financial Assets	84,650	87,150
Gross Amounts Not Offset, Financial Instruments, Resell Agreements, Financial Assets	0	0
Gross Amounts Not Offset, Collateral, Resell Agreements, Financial Assets	(84,650)	(87,150)
Net Amount, Resell Agreements, Financial Assets	0	0
Net Amount Recognized, Total Financial Assets	204,373	206,144
Gross Amounts Not Offset, Collateral, Financial Assets	(169,489)	(143,118)
Net Amount, Financial Assets	2,453	498
Net Amount Recognized, Derivatives, Financial Liabilities	41,311	73,829
Gross Amounts Not Offset, Financial Instruments, Total Derivatives, Financial Liabilities	(32,431)	(62,528)
Gross Amounts Not offset, Collateral, Derivatives, Financial Liabilities	(8,580)	(9,330)
Net Amount, Derivatives, Financial Liabilities	300	1,971
Net Amount Recognized, Repurchase Agreements, Financial Liabilities	4,127,188	4,660,641
Gross Amounts Not Offset, Financial Instruments, Repurchase Agreements, Financial Liabilities	0	0
Gross Amounts Not Offset, Collateral, Repurchase Agreements, Financial Liabilities	(4,127,188)	(4,660,641)
Net Amount, Repurchase Agreements, Financial Liabilities	0	0
Net Amount Recognized, Financial Liabilities	4,168,499	4,734,470
Gross Amounts Not Offset, Collateral, Financial Liabilities	(4,135,768)	(4,669,971)
Net Amount, Financial Liabilities	300	1,971
Counterparty H
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Net Amount Recognized, Derivatives, Financial Assets	36,551	27,031
Gross Amounts Not Offset, Financial Instruments, Total Derivatives, Financial Assets	(8,870)	(20,564)
Gross Amounts Not Offset, Collateral, Derivatives, Financial Assets	(27,170)	(6,467)
Net Amount, Derivatives, Financial Assets	511	0
Net Amount Recognized, Derivatives, Financial Liabilities	8,870	20,564
Gross Amounts Not Offset, Financial Instruments, Total Derivatives, Financial Liabilities	(8,870)	(20,564)
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	31,202	17,297
Gross Amounts Not Offset, Financial Instruments, Total Derivatives, Financial Assets	(7,444)	(17,297)
Gross Amounts Not Offset, Collateral, Derivatives, Financial Assets	(22,954)	0
Net Amount, Derivatives, Financial Assets	804	0
Net Amount Recognized, Derivatives, Financial Liabilities	7,444	27,747
Gross Amounts Not Offset, Financial Instruments, Total Derivatives, Financial Liabilities	(7,444)	(17,297)
Gross Amounts Not offset, Collateral, Derivatives, Financial Liabilities	0	(8,479)
Net Amount, Derivatives, Financial Liabilities	0	1,971
Counterparty B
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Net Amount Recognized, Derivatives, Financial Assets	23,829	39,370
Gross Amounts Not Offset, Financial Instruments, Total Derivatives, Financial Assets	(5,151)	(24,500)
Gross Amounts Not Offset, Collateral, Derivatives, Financial Assets	(18,472)	(14,870)
Net Amount, Derivatives, Financial Assets	206	0
Net Amount Recognized, Derivatives, Financial Liabilities	5,151	24,500
Gross Amounts Not Offset, Financial Instruments, Total Derivatives, Financial Liabilities	(5,151)	(24,500)
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	13,271	14,430
Gross Amounts Not Offset, Financial Instruments, Total Derivatives, Financial Assets	(4,548)	(47)
Gross Amounts Not Offset, Collateral, Derivatives, Financial Assets	(8,723)	(14,131)
Net Amount, Derivatives, Financial Assets	0	252
Net Amount Recognized, Derivatives, Financial Liabilities	4,548	47
Gross Amounts Not Offset, Financial Instruments, Total Derivatives, Financial Liabilities	(4,548)	(47)
Gross Amounts Not offset, Collateral, Derivatives, Financial Liabilities	0	0
Net Amount, Derivatives, Financial Liabilities	0	0
Other Counterparties [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Net Amount Recognized, Derivatives, Financial Assets	14,870	20,866
Gross Amounts Not Offset, Financial Instruments, Total Derivatives, Financial Assets	(6,418)	(120)
Gross Amounts Not Offset, Collateral, Derivatives, Financial Assets	(7,520)	(20,500)
Net Amount, Derivatives, Financial Assets	932	246
Net Amount Recognized, Derivatives, Financial Liabilities	15,298	971
Gross Amounts Not Offset, Financial Instruments, Total Derivatives, Financial Liabilities	(6,418)	(120)
Gross Amounts Not offset, Collateral, Derivatives, Financial Liabilities	(8,580)	(851)
Net Amount, Derivatives, Financial Liabilities	$ 300	$ 0

Balance Sheet Offsetting Bala_2

Balance Sheet Offsetting Balance Sheet Offsetting - Remaining Contractual Maturity of the Securities Sold Under Agreement to Repurchase (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Remaining Contractual Maturity of the Securities Sold Under Agreement to Repurchase [Line Items]
Remaining contractual maturity of the agreements overnight and continuous	$ 4,127,188	$ 4,660,641
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	4,127,188	4,660,641
Securities Sold under Agreements to Repurchase, Gross	4,127,188	4,660,641
Securities Sold under Agreements to Repurchase, Collateral, Right to Reclaim Securities	0	0
US Treasury [Member]
Remaining Contractual Maturity of the Securities Sold Under Agreement to Repurchase [Line Items]
Remaining contractual maturity of the agreements overnight and continuous	3,300,662	3,735,061
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	3,300,662	3,735,061
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	826,526	925,580
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	$ 826,526	$ 925,580

Fair Value Measurements (Narrat

Fair Value Measurements (Narrative) (Detail) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments using fair value measurement option	$ 0	$ 0

Fair Value Measurements (Financ

Fair Value Measurements (Financial Assets and Financial Liabilities Measured at Fair Value on Recurring Basis) (Detail) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale, at estimated fair value	$ 16,578,371	$ 18,243,605
Trading account securities	31,717	28,045
Derivative assets:	119,723	118,994
Derivative liabilities:	41,311	73,829
Interest Rate Swaps Caps And Floors [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets:	90,715	86,793
Derivative liabilities:	90,525	95,533
Commodity Swaps And Options [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets:	70,710	106,685
Derivative liabilities:	69,447	105,392
Foreign Exchange Forward [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets:	22	11
Derivative liabilities:	19	11
US Treasury Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale, at estimated fair value	4,927,589	5,051,587
Trading account securities	30,265	25,879
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	6,596,682	6,376,236
US States and Political Subdivisions Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale, at estimated fair value	5,011,331	6,773,355
Trading account securities	1,452	2,166
Other Investments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale, at estimated fair value	42,769	42,427
Level 1 [Member] | Foreign Exchange Forward [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets:	22	11
Derivative liabilities:	19	11
Level 1 [Member] | US Treasury Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale, at estimated fair value	4,927,589	5,051,587
Trading account securities	30,265	25,879
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:	90,715	86,793
Derivative liabilities:	90,525	95,533
Level 2 [Member] | Commodity Swaps And Options [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets:	70,710	106,685
Derivative liabilities:	69,447	105,392
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	6,596,682	6,376,236
Level 2 [Member] | US States and Political Subdivisions Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale, at estimated fair value	5,011,331	6,773,355
Trading account securities	1,452	2,166
Level 2 [Member] | Other Investments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale, at estimated fair value	42,769	42,427
US Treasury Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale, at estimated fair value	4,927,589	5,051,587
Trading account securities	30,265	25,879
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	6,596,682	6,376,236
US States and Political Subdivisions Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale, at estimated fair value	5,011,331	6,773,355
Trading account securities	1,452	2,166
Other Investments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale, at estimated fair value	$ 42,769	$ 42,427

Fair Value Measurements (Impair

Fair Value Measurements (Impaired Loans Remeasured and Reported at Fair Value of Underlying Collateral) (Detail) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying value before allocations	$ 19,719	$ 6,237	$ 1,333
Specific valuation allowance allocations	(3,391)	(1,480)
Reversal of specific valuation allowance allocations			214
Fair value	16,328	4,757	1,547
Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying value before allocations	15,465	8,156	16,074
Specific valuation allowance allocations	(2,344)		(5,178)
Reversal of specific valuation allowance allocations		625
Fair value	$ 13,121	$ 8,781	$ 10,896

Fair Value Measurements (Estima

Fair Value Measurements (Estimated Fair Values of Financial Instruments) (Detail) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total cash and cash equivalents	$ 8,687,276	$ 12,028,132	$ 16,583,000	$ 10,288,853
Securities held to maturity	3,619,428	2,639,083
Loans, net	18,578,255	16,927,348
Deposits	41,920,568	43,954,196
Federal funds purchased	14,200	51,650
Repurchase agreements	4,127,188	4,660,641
Junior subordinated deferrable interest debentures	123,127	123,069
Subordinated notes	99,491	99,335
Carrying Amount [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total cash and cash equivalents	8,687,276	12,028,132
Securities held to maturity	3,619,428	2,639,083
Accrued interest receivable	251,385	243,682
Deposits	41,920,568	43,954,196
Federal funds purchased	14,200	51,650
Repurchase agreements	4,127,188	4,660,641
Junior subordinated deferrable interest debentures	123,127	123,069
Subordinated notes	99,491	99,335
Accrued interest payable	61,222	18,444
Carrying Amount [Member] | Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans, net	18,578,255	16,927,348
Estimated Fair Value [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total cash and cash equivalents	8,687,276	12,028,132
Securities held to maturity	3,532,044	2,467,865
Accrued interest receivable	251,385	243,682
Deposits	41,903,580	43,920,741
Federal funds purchased	14,200	51,650
Repurchase agreements	4,127,188	4,660,641
Junior subordinated deferrable interest debentures	123,712	123,712
Subordinated notes	96,071	97,014
Accrued interest payable	61,222	18,444
Estimated Fair Value [Member] | Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans, net	$ 18,117,369	$ 16,343,417

Operating Segments Operating Se

Operating Segments Operating Segments - Additional Information (Details) $ in Billions	12 Months Ended
	Dec. 31, 2023 USD ($) Segment	Dec. 31, 2022 USD ($) Segment	Dec. 31, 2021 USD ($) Segment
Segment Reporting Information [Line Items]
Number of operating segments | Segment	2	2	2
Frost Wealth Advisors [Member]
Segment Reporting Information [Line Items]
Fair value of off-balance sheet managed and custody assets | $	$ 47.2	$ 42.9	$ 43.3

Operating Segments (Summary of

Operating Segments (Summary of Operating Results by Segment) (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Segment Reporting Information [Line Items]
Net interest income (expense)	$ 1,558,664	$ 1,291,283	$ 984,867
Credit loss expense	46,171	3,000	63
Non-interest income	428,542	404,818	386,728
Non-interest expense	1,228,662	1,024,274	881,994
Income before income taxes	712,373	668,827	489,538
Income tax expense (benefit)	114,400	89,677	46,459
Net income	597,973	579,150	443,079
Preferred stock dividends	6,675	6,675	7,157
Net income available to common shareholders	591,298	572,475	435,922
Revenues from (expenses to) external customers	1,987,206	1,696,101	1,371,595
Average assets	49,604,000	51,513,000	45,983,000
Banking [Member]
Segment Reporting Information [Line Items]
Net interest income (expense)	1,562,441	1,295,467	989,870
Credit loss expense	46,171	3,000	54
Non-interest income	251,319	230,876	220,662
Non-interest expense	1,077,824	886,421	753,719
Income before income taxes	689,765	636,922	456,759
Income tax expense (benefit)	111,145	85,127	41,483
Net income	578,620	551,795	415,276
Preferred stock dividends	0	0	0
Net income available to common shareholders	578,620	551,795	415,276
Revenues from (expenses to) external customers	1,813,760	1,526,343	1,210,532
Average assets	49,536,000	51,448,000	45,903,000
Frost Wealth Advisors [Member]
Segment Reporting Information [Line Items]
Net interest income (expense)	7,620	4,645	2,138
Credit loss expense	0	0	9
Non-interest income	178,906	175,874	167,442
Non-interest expense	144,478	132,009	122,972
Income before income taxes	42,048	48,510	46,599
Income tax expense (benefit)	8,830	10,187	9,786
Net income	33,218	38,323	36,813
Preferred stock dividends	0	0	0
Net income available to common shareholders	33,218	38,323	36,813
Revenues from (expenses to) external customers	186,526	180,519	169,580
Average assets	59,000	57,000	70,000
Non-Banks [Member]
Segment Reporting Information [Line Items]
Net interest income (expense)	(11,397)	(8,829)	(7,141)
Credit loss expense	0	0	0
Non-interest income	(1,683)	(1,932)	(1,376)
Non-interest expense	6,360	5,844	5,303
Income before income taxes	(19,440)	(16,605)	(13,820)
Income tax expense (benefit)	(5,575)	(5,637)	(4,810)
Net income	(13,865)	(10,968)	(9,010)
Preferred stock dividends	6,675	6,675	7,157
Net income available to common shareholders	(20,540)	(17,643)	(16,167)
Revenues from (expenses to) external customers	(13,080)	(10,761)	(8,517)
Average assets	$ 9,000	$ 8,000	$ 10,000

Condensed Financial Statement_3

Condensed Financial Statements of Parent Company (Schedule of Condensed Balance Sheets) (Detail) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Condensed Financial Statements, Captions [Line Items]
Cash	$ 617,569	$ 691,553
Total cash and cash equivalents	8,687,276	12,028,132	$ 16,583,000	$ 10,288,853
Total assets	50,845,038	52,892,376
Junior subordinated deferrable interest debentures, net of unamortized issuance costs	123,127	123,069
Subordinated notes, net of unamortized issuance costs	99,491	99,335
Accrued interest payable and other liabilities	844,017	866,257
Total liabilities	47,128,591	49,755,148
Shareholders’ Equity	3,716,447	3,137,228	4,439,555	4,293,016
Total liabilities and shareholders’ equity	50,845,038	52,892,376
Parent Company [Member]
Condensed Financial Statements, Captions [Line Items]
Cash	350,525	311,944
Total cash and cash equivalents	350,525	311,944	$ 471,875	$ 381,240
Investment in subsidiaries	3,625,951	3,065,114
Accrued interest receivable and other assets	1,233	1,142
Total assets	3,977,709	3,378,200
Junior subordinated deferrable interest debentures, net of unamortized issuance costs	123,127	123,069
Subordinated notes, net of unamortized issuance costs	99,491	99,335
Accrued interest payable and other liabilities	38,644	18,568
Total liabilities	261,262	240,972
Shareholders’ Equity	3,716,447	3,137,228
Total liabilities and shareholders’ equity	$ 3,977,709	$ 3,378,200

Condensed Financial Statement_4

Condensed Financial Statements of Parent Company (Schedule of Condensed Statements of Income) (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Condensed Financial Statements, Captions [Line Items]
Total income	$ 2,217,716	$ 1,475,721	$ 1,008,769
Interest expense	659,052	184,438	23,902
Other	229,367	194,701	172,154
Income before income taxes and equity in undistributed earnings of subsidiaries	712,373	668,827	489,538
Income tax benefit	(114,400)	(89,677)	(46,459)
Net income	597,973	579,150	443,079
Preferred stock dividends	6,675	6,675	7,157
Net income available to common shareholders	591,298	572,475	435,922
Parent Company [Member]
Condensed Financial Statements, Captions [Line Items]
Dividend income paid by Frost Bank	279,679	51,711	219,386
Dividend income paid by non-banks	255	109	473
Interest and other income	1,929	0	101
Total income	281,863	51,820	219,960
Interest expense	13,304	8,829	7,141
Salaries and employee benefits	1,668	1,605	1,499
Other	6,653	6,316	5,867
Total expenses	21,625	16,750	14,507
Income before income taxes and equity in undistributed earnings of subsidiaries	260,238	35,070	205,453
Income tax benefit	5,974	5,641	4,899
Equity in undistributed earnings of subsidiaries	331,761	538,439	232,727
Net income	597,973	579,150	443,079
Preferred stock dividends	6,675	6,675	7,157
Net income available to common shareholders	$ 591,298	$ 572,475	$ 435,922

Condensed Financial Statement_5

Condensed Financial Statements of Parent Company (Schedule of Condensed Statements of Cash Flows) (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Condensed Financial Statements, Captions [Line Items]
Net income	$ 597,973	$ 579,150	$ 443,079
Stock-based compensation	24,590	18,322	12,753
Net tax benefit from stock-based compensation	894	4,602	7,877
Net cash provided by (used in) operating activities	478,845	722,582	648,293
Net cash provided by (used in) investing activities	(942,751)	(8,277,330)	(2,525,015)
Principal payments on long-term borrowings	0	0	(13,403)
Proceeds from stock option exercises	9,299	16,659	54,417
Purchase of treasury stock	(42,720)	(4,391)	(3,864)
Treasury stock issued to 401(k) stock purchase plan	0	0	1,749
Cash dividends paid on preferred stock	(6,675)	(6,675)	(7,157)
Cash dividends paid on common stock	(232,323)	(209,780)	(188,786)
Net cash provided by (used in) financing activities	(2,876,950)	2,999,880	8,170,869
Net change in cash and cash equivalents	(3,340,856)	(4,554,868)	6,294,147
Cash and cash equivalents at beginning of year	12,028,132	16,583,000	10,288,853
Cash and cash equivalents at end of year	8,687,276	12,028,132	16,583,000
Parent Company [Member]
Condensed Financial Statements, Captions [Line Items]
Net income	597,973	579,150	443,079
Equity in undistributed earnings of subsidiaries	(331,761)	(538,439)	(232,727)
Stock-based compensation	880	720	700
Net tax benefit from stock-based compensation	331	472	278
Net change in other assets and other liabilities	19,867	(15,249)	23,890
Net cash provided by (used in) operating activities	287,290	26,654	235,220
Redemption of investment in non-bank subsidiary	0	0	406
Net cash provided by (used in) investing activities	0	0	406
Principal payments on long-term borrowings	0	0	(13,403)
Proceeds from stock option exercises	9,299	16,659	54,417
Proceeds from stock-based compensation activities of subsidiaries	23,710	17,602	12,053
Purchase of treasury stock	(42,720)	(4,391)	(3,864)
Treasury stock issued to 401(k) stock purchase plan	0	0	1,749
Cash dividends paid on preferred stock	(6,675)	(6,675)	(7,157)
Cash dividends paid on common stock	(232,323)	(209,780)	(188,786)
Net cash provided by (used in) financing activities	(248,709)	(186,585)	(144,991)
Net change in cash and cash equivalents	38,581	(159,931)	90,635
Cash and cash equivalents at beginning of year	311,944	471,875	381,240
Cash and cash equivalents at end of year	$ 350,525	$ 311,944	$ 471,875