Cullen/Frost Bankers (CFR) 10-K 4 Feb 22 2021 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2021	Jan. 26, 2022	Jun. 30, 2021	Dec. 31, 2020
Entity Information [Line Items]
Document Type	10-K
Document Annual Report	true
Document Period End Date	Dec. 31, 2021
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2021
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
Entity Shell Company	false
Entity Public Float			$ 6,800
Entity Common Stock, Shares Outstanding		64,023,571
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, 2021	Dec. 31, 2020
Assets:
Cash and due from banks	$ 555,778	$ 529,454
Interest-bearing deposits	15,985,244	9,758,624
Federal funds sold	34,075	775
Resell agreements	7,903	0
Total cash and cash equivalents	16,583,000	10,288,853
Securities held to maturity, net of allowance for credit losses of $158 in 2021 and $160 in 2020	1,749,179	1,945,673
Securities available for sale, at estimated fair value	13,924,628	10,437,565
Trading account securities	25,162	24,456
Loans, net of unearned discounts	16,336,397	17,481,309
Less: Allowance for credit losses on loans	(248,666)	(263,177)
Net loans	16,087,731	17,218,132
Premises and equipment, net	1,050,331	1,045,578
Goodwill	654,952	654,952
Other intangible assets, net	866	1,563
Cash surrender value of life insurance policies	190,139	189,984
Accrued interest receivable and other assets	612,502	584,561
Total assets	50,878,490	42,391,317
Liabilities:
Non-interest-bearing public funds deposits	18,423,018	15,117,051
Interest-bearing public funds deposits	24,272,678	19,898,710
Total deposits	42,695,696	35,015,761
Federal funds purchased	25,925	48,850
Repurchase agreements	2,740,799	2,068,147
Junior subordinated deferrable interest debentures, net of unamortized issuance costs	123,011	136,357
Subordinated notes, net of unamortized issuance costs	99,178	99,021
Accrued interest payable and other liabilities	754,326	730,165
Total liabilities	46,438,935	38,098,301
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 2021 and 2020	145,452	145,452
Common stock, par value $0.01 per share; 210,000,000 shares authorized; 64,236,306 shares issued in both 2021 and 2020	642	642
Additional paid-in capital	1,009,921	997,168
Retained earnings	2,956,966	2,750,723
Accumulated other comprehensive income, net of tax	347,318	512,970
Treasury stock, at cost; 250,070 shares in 2021 and 1,225,066 in 2020	(20,744)	(113,939)
Total shareholders’ equity	4,439,555	4,293,016
Total liabilities and shareholders’ equity	$ 50,878,490	$ 42,391,317

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - USD ($)	Dec. 31, 2021	Dec. 31, 2020
Debt Securities, Held-to-maturity, Allowance for Credit Loss	$ (158,000)	$ (160,000)
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	64,236,306	64,236,306
Treasury Stock, Shares	250,070	1,225,066
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, 2021	Dec. 31, 2020	Dec. 31, 2019
Interest income:
Loans, including fees	$ 674,611	$ 680,064	$ 741,747
Securities:
Taxable	89,550	93,569	117,082
Tax-exempt	226,683	233,614	233,842
Interest-bearing deposits	17,878	12,893	35,590
Federal funds sold	31	723	5,260
Resell agreements	16	172	264
Total interest income	1,008,769	1,021,035	1,133,785
Interest expense:
Deposits	14,520	32,018	99,742
Federal funds purchased	32	100	347
Repurchase agreements	2,209	4,382	19,328
Junior subordinated deferrable interest debentures	2,484	3,560	5,706
Subordinated notes	4,657	4,656	4,657
Federal Home Loan Bank advances	0	318	0
Total interest expense	23,902	45,034	129,780
Net interest income	984,867	976,001	1,004,005
Credit loss expense	63	241,230	33,759
Net interest income after credit loss expense	984,804	734,771	970,246
Non-interest income:
Trust and investment management fees	148,994	129,272	126,722
Service charges on deposit accounts	83,292	80,873	88,983
Insurance commissions and fees	51,548	50,313	52,345
Interchange and card transaction fees	17,461	13,470	14,873
Other charges, commissions and fees	36,836	34,825	37,123
Net gain (loss) on securities transactions	69	108,989	293
Other	48,528	47,712	43,563
Total non-interest income	386,728	465,454	363,902
Non-interest expense:
Salaries and wages	395,497	387,328	375,029
Employee benefits	82,029	75,676	86,230
Net occupancy	107,344	102,938	89,466
Technology, furniture and equipment	112,738	105,232	91,995
Deposit insurance	12,232	10,502	10,126
Intangible amortization	697	918	1,168
Other	171,457	166,310	180,665
Total non-interest expense	881,994	848,904	834,679
Income before income taxes	489,538	351,321	499,469
Income taxes	46,459	20,170	55,870
Net income	443,079	331,151	443,599
Preferred stock dividends	7,157	2,016	8,063
Redemption of preferred stock	0	5,514	0
Net income available to common shareholders	$ 435,922	$ 323,621	$ 435,536
Earnings per common share:
Basic (in dollars per share)	$ 6.79	$ 5.11	$ 6.89
Diluted (in dollars per share)	$ 6.76	$ 5.10	$ 6.84

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Net income	$ 443,079	$ 331,151	$ 443,599
Other comprehensive income (loss), before tax:
Change in net unrealized gain/loss on securities available for sale during the period	(231,355)	427,331	418,556
Change in net unrealized gain on securities transferred to held-to-maturity	(971)	(1,256)	(1,292)
Reclassification adjustment for net (gains) losses included in net income	(69)	(108,989)	(293)
Total securities available for sale and transferred securities before tax amount	(232,395)	317,086	416,971
Defined-benefit post-retirement benefit plans:
Change in the net actuarial gain/loss before tax amount	16,593	(11,518)	(3,644)
Reclassification adjustment for net amortization of actuarial gain/loss included in net income as a component of net periodic cost (benefit) before tax amount	6,116	5,319	5,623
Total defined-benefit post-retirement benefit plans	22,709	(6,199)	1,979
Reclassification adjustments for (gains) losses included in net income:
Other comprehensive income (loss), before tax	(209,686)	310,887	418,950
Deferred tax expense (benefit)	(44,034)	65,287	87,980
Other comprehensive income (loss), net of tax	(165,652)	245,600	330,970
Comprehensive income	$ 277,427	$ 576,751	$ 774,569

Consolidated Statement of Chang

Consolidated Statement of Changes in Shareholders' Equity - USD ($) $ in Thousands	Total	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 [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative effect of accounting change	$ (14,672)				$ (14,672)
Adjusted beginning balance	3,354,245	$ 144,486	$ 642	$ 967,304	2,425,330	$ (63,600)	$ (119,917)
Balance at Dec. 31, 2018	3,368,917	144,486	642	967,304	2,440,002	(63,600)	(119,917)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	443,599				443,599
Other comprehensive income, net of tax	330,970					330,970
Proceeds from stock option exercises/stock unit conversions (987,758 shares, 408,563 shares, and 399,224 shares during 2021, 2020, and 2019, respectively)	20,770				(16,326)		37,096
Stock-based compensation expense recognized in earnings	15,946			15,946
Purchase of treasury stock (31,317 shares, 206,951 shares, and 716,062 shares during 2021, 2020, and 2019, respectively)	(68,793)						(68,793)
Treasury Stock issued to the 401(k) stock purchase plan (18,555 shares in 2021 and 140,264 shares in 2020)	0
Cash dividends paid on preferred stock (approximately $47.71 per share which is equivalent to approximately $1.19 per depositary share in 2021 and approximately $0.34 per share in 2020 and $1.34 per share in 2019)	(8,063)				(8,063)
Cash dividends – common stock ($2.94 per share, $2.85 per share, and $2.80 per share in 2021, 2020, and 2019, respectively)	(177,006)				(177,006)
Balance at Dec. 31, 2019	3,911,668	144,486	642	983,250	2,667,534	267,370	(151,614)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative effect of accounting change	(29,252)				(29,252)
Adjusted beginning balance	3,882,416	144,486	642	983,250	2,638,282	267,370	(151,614)
Net income	331,151				331,151
Other comprehensive income, net of tax	245,600					245,600
Proceeds from stock option exercises/stock unit conversions (987,758 shares, 408,563 shares, and 399,224 shares during 2021, 2020, and 2019, respectively)	12,557				(27,214)		39,771
Stock-based compensation expense recognized in earnings	13,918			13,918
Redemption of series A preferred stock (6,000,000 shares)	(150,000)	(144,486)			(5,514)
Issuance of series B preferred stock (150,000 shares)	145,452	145,452
Purchase of treasury stock (31,317 shares, 206,951 shares, and 716,062 shares during 2021, 2020, and 2019, respectively)	(15,785)						(15,785)
Treasury Stock issued to the 401(k) stock purchase plan (18,555 shares in 2021 and 140,264 shares in 2020)	10,307				(3,382)		13,689
Cash dividends paid on preferred stock (approximately $47.71 per share which is equivalent to approximately $1.19 per depositary share in 2021 and approximately $0.34 per share in 2020 and $1.34 per share in 2019)	(2,016)				(2,016)
Cash dividends – common stock ($2.94 per share, $2.85 per share, and $2.80 per share in 2021, 2020, and 2019, respectively)	(180,584)				(180,584)
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 (987,758 shares, 408,563 shares, and 399,224 shares during 2021, 2020, and 2019, respectively)	54,417				(40,836)		95,253
Stock-based compensation expense recognized in earnings	12,753			12,753
Purchase of treasury stock (31,317 shares, 206,951 shares, and 716,062 shares during 2021, 2020, and 2019, respectively)	(3,864)						(3,864)
Treasury Stock issued to the 401(k) stock purchase plan (18,555 shares in 2021 and 140,264 shares in 2020)	1,749				(57)		1,806
Cash dividends paid on preferred stock (approximately $47.71 per share which is equivalent to approximately $1.19 per depositary share in 2021 and approximately $0.34 per share in 2020 and $1.34 per share in 2019)	(7,157)				(7,157)
Cash dividends – common stock ($2.94 per share, $2.85 per share, and $2.80 per share in 2021, 2020, and 2019, 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)

Consolidated Statement of Cha_2

Consolidated Statement of Changes in Shareholders' Equity (Parenthetical) - $ / shares	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Stock option exercises/deferred stock unit conversions, shares	987,758	408,563	399,224
Stock Redeemed or Called During Period, Shares		6,000,000
Stock Issued During Period, Shares, New Issues		150,000
Treasury Stock, Shares, Acquired	31,317	206,951	716,062
Stock Issued During Period, Shares, Treasury Stock Reissued	18,555	140,264
Preferred Stock, Dividends Per Share, Declared	$ 47.71	$ 0.34	$ 1.34
Preferred stock, Dividends equivalent per depositary share, Declared	1.19
Common Stock, Dividends, Per Share, Cash Paid	$ 2.94	$ 2.85	$ 2.80

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Operating Activities:
Net income	$ 443,079	$ 331,151	$ 443,599
Adjustments to reconcile net income to net cash from operating activities:
Credit loss expense	63	241,230	33,759
Deferred tax expense (benefit)	7,784	(15,832)	7,614
Accretion of loan discounts	(12,890)	(15,692)	(15,197)
Securities premium amortization (discount accretion), net	119,242	123,785	115,558
Net (gain) loss on securities transactions	(69)	(108,989)	(293)
Depreciation and amortization	69,289	64,370	54,091
Net (gain) loss on sale/exchange/write-down of assets/foreclosed assets	(11,578)	524	(5,712)
Stock-based compensation	12,753	13,918	15,946
Net tax benefit from stock-based compensation	7,877	852	2,447
Earnings on life insurance policies	(2,462)	(3,731)	(3,683)
Net change in:
Trading account securities	(560)	(158)	(212)
Lease right-of-use assets	23,504	23,933	20,124
Accrued interest receivable and other assets	(46,560)	(158,264)	(15,570)
Accrued interest payable and other liabilities	38,821	27,146	(18,381)
Net cash provided by (used in) operating activities	648,293	524,243	634,090
Investing Activities:
Securities held to maturity: Purchases	0	(1,500)	(649,326)
Securities held to maturity: Maturities, calls and principal repayments	177,593	63,577	81,762
Securities available for sale:
Purchases	(24,217,841)	(20,841,622)	(23,306,694)
Sales	1,999,891	1,162,352	18,660,147
Maturities, calls and principal repayments	18,425,108	20,893,464	4,694,927
Proceeds from sale of loans	0	37,535	24,036
Net change in loans	1,145,924	(2,856,395)	(693,587)
Benefits received on life insurance policies	2,307	903	0
Proceeds from sales of premises and equipment	7,044	5,988	8,038
Purchases of premises and equipment	(65,850)	(95,422)	(206,716)
Proceeds from sales of repossessed properties	809	73	663
Net cash provided by (used in) investing activities	(2,525,015)	(1,631,047)	(1,386,750)
Financing Activities:
Net change in deposits	7,679,935	7,376,197	490,360
Net change in short-term borrowings	649,727	421,655	327,794
Proceeds from Federal Home Loan Bank advances	0	1,250,000	0
Principal payments on Federal Home Loan Bank advances	0	(1,250,000)	0
Principal payments on long-term borrowings	(13,403)
Redemption of Series A preferred stock	0	(150,000)	0
Proceeds from issuance of Series B preferred stock	0	145,452	0
Proceeds from stock option exercises	54,417	12,557	20,770
Purchase of treasury stock	(3,864)	(15,785)	(68,793)
Cash dividends paid on preferred stock	(7,157)	(2,016)	(8,063)
Cash dividends paid on common stock	(188,786)	(180,584)	(177,006)
Net cash provided by (used in) financing activities	8,170,869	7,607,476	585,062
Net change in cash and cash equivalents	6,294,147	6,500,672	(167,598)
Cash and cash equivalents at beginning of year	10,288,853	3,788,181	3,955,779
Cash and cash equivalents at end of year	$ 16,583,000	$ 10,288,853	$ 3,788,181

Summary of Significant Accounti

Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2021
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, 2021 and 2020, we had $110.3 million and $74.0 million in cash collateral on deposit with other financial institution counterparties to interest rate swap transactions. Additionally, prior to 2021 we were required to maintain a minimum amount cash on hand or on deposit with the Federal Reserve Bank to meet regulatory reserve and clearing requirements. This amount totaled $42.0 million at December 31, 2020. 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, 2021 2020 2019 Cash paid for interest $ 29,003 $ 49,300 $ 124,781 Cash paid for income tax 39,852 44,140 45,352 Significant non-cash transactions: Transfer of securities from available for sale to held to maturity — — 377,812 Exchange of real estate 11,036 — — Unsettled securities transactions 27,032 57,783 — Loans foreclosed and transferred to other real estate owned and foreclosed assets 3,464 140 1,348 Loans to facilitate the sale of other real estate owned — — 847 Right-of-use lease assets obtained in exchange for lessee operating lease liabilities 12,854 18,284 319,286 Treasury stock issued to 401(k) stock purchase plan 1,749 10,307 — 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. As further discussed below, we adopted Accounting Standards Update (“ASU”) 2016-13, “Financial Instruments - Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments,” on January 1, 2020. Accounting Standards Codification (“ASC”) Topic 326 (“ASC 326”) replaced the previous “incurred loss” model for measuring credit losses, which encompassed allowances for current known and inherent losses within the portfolio, with an “expected loss” model, which encompasses allowances for losses expected to be incurred over the life of the portfolio. The new current expected credit loss (“CECL”) model requires the measurement of all expected credit losses for financial assets measured at amortized cost and certain off-balance-sheet credit exposures based on historical experience, current conditions, and reasonable and supportable forecasts. In connection with the adoption of ASC 326, we revised certain accounting policies and implemented certain accounting policy elections. The revised accounting policies are described below. 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 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. Prior to the adoption of ASU 2016-13, declines in the fair value of held-to-maturity and available-for-sale securities below their cost that were deemed to be other than temporary were reflected in earnings as realized losses. In estimating other-than-temporary impairment losses prior to January 1, 2020, management considered, among other things, (i) the length of time and the extent to which the fair value had been less than cost, (ii) the financial condition and near-term prospects of the issuer and (iii) the intent and our ability to retain our investment in the issuer for a period of time sufficient to allow for any anticipated recovery in fair value. 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. Prior to the adoption of ASU 2016-13, the allowance for credit losses on loans was a contra-asset valuation account established through a provision for loan losses charged to expense, which represented management’s best estimate of inherent losses that had been incurred within the existing portfolio of loans. The allowance for credit losses on loans included allowance allocations calculated in accordance with ASC Topic 310, “Receivables” and allowance allocations calculated in accordance with ASC Topic 450, “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. 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 8 - 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. In 2019, we adopted certain accounting standard updates related to accounting for leases as further discussed below. Under the new standards, 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 $3.4 million and $850 thousand at December 31, 2021 and 2020. 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. Write-downs of foreclosed assets totaled $14 thousand during 2021 and $231 thousand in 2020 while there were no write-downs during 2019. There were no significant concentrations of any properties, to which the aforementioned write-downs relate, in any single geographic region. Goodwill. Goodwill represents the excess of the cost of businesses acquired over the fair value of the net assets acquired. Goodwill is assigned to reporting units and tested for impairment at least annually on October 1st, or on an interim basis if an event occurs or circumstances change that would more likely than not reduce the fair value of the reporting unit below its carrying value. See Note 5 - Goodwill and Other Intangible Assets. Intangibles and Other Long-Lived Assets . Intangible assets are acquired assets that lack physical substance but can be distinguished from goodwill because of contractual or other legal rights or because the asset is capable of being sold or exchanged either on its own or in combination with a related contract, asset, or liability. Our intangible assets relate to core deposits, non-compete agreements and customer relationships. Intangible assets with definite useful lives are amortized on an accelerated basis over their estimated life. Intangible assets with indefinite useful lives are not amortized until their lives are determined to be definite. Intangible assets, premises and equipment and other long-lived assets are tested for impairment whenever events or changes in circumstances indicate the carrying amount of the assets may not be recoverable from future undiscounted cash flows. If impaired, the assets are recorded at fair value. See Note 5 - Goodwill and Other Intangible Assets. 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 13 - 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 10 - 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 14 - 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 17 - 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. Certain items in prior financial statements have been reclassified to conform to the current presentation. As discussed above, on January 1, 2020 we adopted the provisions of ASC 326 using the modified retrospective method for all financial assets measured at amortized cost

Securities

Securities	12 Months Ended
	Dec. 31, 2021
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, 2021 and 2020 is presented below. Amortized Gross Gross Estimated Allowance Net December 31, 2021 Residential mortgage-backed securities $ 527,264 $ 18,766 $ — $ 546,030 $ — $ 527,264 States and political subdivisions 1,220,573 41,141 101 1,261,613 (158) 1,220,415 Other 1,500 — — 1,500 — 1,500 Total $ 1,749,337 $ 59,907 $ 101 $ 1,809,143 $ (158) $ 1,749,179 December 31, 2020 Residential mortgage-backed securities $ 528,784 $ 41,742 $ — $ 570,526 $ — $ 528,784 States and political subdivisions 1,415,549 65,321 — 1,480,870 (160) 1,415,389 Other 1,500 — — 1,500 — 1,500 Total $ 1,945,833 $ 107,063 $ — $ 2,052,896 $ (160) $ 1,945,673 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 $642.3 million and $659.2 million at December 31, 2021 and 2020, respectively. Accrued interest receivable on held-to-maturity securities totaled $18.4 million and $21.7 million at December 31, 2021 and 2020, 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. During 2019, we reclassified securities with an aggregate fair value of $377.8 million and an aggregate net unrealized gain of $3.3 million ($2.6 million, net of tax) on the date of the transfer. The net unamortized, unrealized gain remaining on transferred securities, including those transferred in 2019 and in years prior, included in accumulated other comprehensive income in the accompanying balance sheet totaled $2.5 million ($2.0 million, net of tax) at December 31, 2021 and $3.5 million ($2.8 million, net of tax) at December 31, 2020. 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, 2021: States and Political Subdivisions Not Guaranteed or Pre-Refunded Guaranteed by the Texas PSF Pre-Refunded Total Other Aaa/AAA $ 92,379 $ 460,648 $ 563,251 $ 1,116,278 $ — Aa/AA 104,295 — — 104,295 — Not rated — — — — 1,500 Total $ 196,674 $ 460,648 $ 563,251 $ 1,220,573 $ 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, 2021, 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. 2021 2020 Beginning balance $ 160 $ — Impact of adopting ASC 326 — 215 Credit loss expense (benefit) (2) (55) Ending balance $ 158 $ 160 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, 2021 and 2020 is presented below. Amortized Gross Gross Allowance Estimated December 31, 2021 U.S. Treasury $ 2,165,702 $ 23,333 $ 9,602 $ — $ 2,179,433 Residential mortgage-backed securities 4,059,692 31,662 25,089 — 4,066,265 States and political subdivisions 7,178,135 463,810 5,374 — 7,636,571 Other 42,359 — — — 42,359 Total $ 13,445,888 $ 518,805 $ 40,065 $ — $ 13,924,628 December 31, 2020 U.S. Treasury $ 1,084,542 $ 35,091 $ — $ — $ 1,119,633 Residential mortgage-backed securities 1,916,581 71,102 4 — 1,987,679 States and political subdivisions 6,683,927 603,975 — — 7,287,902 Other 42,351 — — — 42,351 Total $ 9,727,401 $ 710,168 $ 4 $ — $ 10,437,565 All mortgage-backed securities included in the above table were issued by U.S. government agencies and corporations. At December 31, 2021 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 76.6% 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 $5.8 billion and $4.4 billion at December 31, 2021 and 2020, respectively. Accrued interest receivable on available-for-sale securities totaled $120.5 million and $111.0 million at December 31, 2021 and 2020, 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, 2021, 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 $ 684,242 $ 9,602 $ — $ — $ 684,242 $ 9,602 Residential mortgage-backed securities 2,219,261 23,625 45,963 1,464 2,265,224 25,089 States and political subdivisions 364,056 5,074 5,675 300 369,731 5,374 Total $ 3,267,559 $ 38,301 $ 51,638 $ 1,764 $ 3,319,197 $ 40,065 As of December 31, 2021, 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, 2021. 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 $ 37 $ — $ 515,100 $ 12,127 $ 527,264 States and political subdivisions 464,112 180,373 73,808 502,280 1,220,573 Other 1,500 — — — 1,500 Total $ 465,649 $ 180,373 $ 588,908 $ 514,407 $ 1,749,337 Estimated Fair Value Residential mortgage-backed securities $ 37 $ — $ 533,454 $ 12,539 $ 546,030 States and political subdivisions 468,685 185,458 74,729 532,741 1,261,613 Other 1,500 — — — 1,500 Total $ 470,222 $ 185,458 $ 608,183 $ 545,280 $ 1,809,143 Available For Sale Amortized Cost U. S. Treasury $ — $ 1,030,591 $ 943,417 $ 191,694 $ 2,165,702 Residential mortgage-backed securities 63 15,278 19,175 4,025,176 4,059,692 States and political subdivisions 86,485 1,611,040 808,323 4,672,287 7,178,135 Other — — — — 42,359 Total $ 86,548 $ 2,656,909 $ 1,770,915 $ 8,889,157 $ 13,445,888 Estimated Fair Value U. S. Treasury $ — $ 1,038,734 $ 942,113 $ 198,586 $ 2,179,433 Residential mortgage-backed securities 64 15,954 19,624 4,030,623 4,066,265 States and political subdivisions 87,493 1,715,065 858,485 4,975,528 7,636,571 Other — — — — 42,359 Total $ 87,557 $ 2,769,753 $ 1,820,222 $ 9,204,737 $ 13,924,628 Sales of Securities. Sales of securities available for sale were as follows: 2021 2020 2019 Proceeds from sales $ 1,999,891 $ 1,162,352 $ 18,660,147 Gross realized gains 69 108,989 930 Gross realized losses — — (637) Tax benefit (expense) related to securities gains/losses (14) (22,888) (62) Premiums and Discounts. Premium amortization and discount accretion included in interest income on securities was as follows: 2021 2020 2019 Premium amortization $ (121,994) $ (126,210) $ (120,785) Discount accretion 2,752 2,425 5,227 Net (premium amortization) discount accretion $ (119,242) $ (123,785) $ (115,558) Trading Account Securities. Year-end trading account securities, at estimated fair value, were as follows: 2021 2020 U.S. Treasury $ 24,237 $ 23,996 States and political subdivisions 925 460 Total $ 25,162 $ 24,456 Net gains and losses on trading account securities were as follows: 2021 2020 2019 Net gain on sales transactions $ 1,014 $ 1,102 $ 2,173 Net mark-to-market gains (losses) (75) 85 (176) Net gain on trading account securities $ 939 $ 1,187 $ 1,997

Loans

Loans	12 Months Ended
	Dec. 31, 2021
Receivables [Abstract]
Loans	Loans Year-end loans, including leases net of unearned discounts, consisted of the following: 2021 2020 Commercial and industrial $ 5,364,954 $ 4,955,341 Energy: Production 878,436 976,473 Service 105,901 116,825 Other 93,455 141,900 Total energy 1,077,792 1,235,198 Paycheck Protection Program 428,882 2,433,849 Commercial real estate: Commercial mortgages 5,867,062 5,478,806 Construction 1,304,271 1,223,814 Land 405,277 317,847 Total commercial real estate 7,576,610 7,020,467 Consumer real estate: Home equity loans 324,157 329,390 Home equity lines of credit 519,098 452,854 Other 567,535 548,530 Total consumer real estate 1,410,790 1,330,774 Total real estate 8,987,400 8,351,241 Consumer and other 477,369 505,680 Total loans $ 16,336,397 $ 17,481,309 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, 2021 and 2020, there were no concentrations of loans related to any single industry in excess of 10% of total loans. At such dates, the largest industry concentration was related to the energy industry, which totaled 6.6% of total loans, or 6.8% excluding PPP Loans at December 31, 2021 and 7.1% of total loans, or 8.2% excluding PPP Loans at December 31, 2020. Unfunded commitments to extend credit and standby letters of credit issued to customers in the energy industry totaled $891.4 million and $68.9 million, respectively, as of December 31, 2021. 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, 2021 or 2020. Overdrafts . Deposit account overdrafts reported as loans totaled $7.8 million and $5.6 million at December 31, 2021 and 2020. 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 2021 is presented in the following table. Other changes were primarily related to changes in related-party status. Balance outstanding at December 31, 2020 $ 353,105 Principal additions 262,761 Principal payments (196,634) Other changes (68,694) Balance outstanding at December 31, 2021 $ 350,538 Accrued Interest Receivable. Accrued interest receivable on loans totaled $40.0 million and $48.7 million at December 31, 2021 and 2020, 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, 2021 December 31, 2020 Total Non-Accrual Non-Accrual with No Credit Loss Allowance Total Non-Accrual Non-Accrual with No Credit Loss Allowance Commercial and industrial $ 22,582 $ 4,701 $ 19,849 $ 4,479 Energy 14,433 8,533 23,168 639 Paycheck Protection Program — — — — Commercial real estate: Buildings, land and other 15,297 13,817 15,737 14,116 Construction 948 — 1,684 1,684 Consumer real estate 440 138 993 993 Consumer and other 13 13 18 — Total $ 53,713 $ 27,202 $ 61,449 $ 21,911 The following tables present non-accrual loans as of December 31, 2021 and December 31, 2020 by class and year of origination. December 31, 2021 2021 2020 2019 2018 2017 Prior Revolving Loans Revolving Loans Converted to Term Total Commercial and industrial $ 636 $ 3,856 $ 5,047 $ 1,820 $ 765 $ 353 $ 4,635 $ 5,470 $ 22,582 Energy — — 5,358 1,325 — — 6,931 819 14,433 Paycheck Protection Program — — — — — — — — — Commercial real estate: Buildings, land and other 6,038 307 3,446 814 2,030 2,662 — — 15,297 Construction — 948 — — — — — — 948 Consumer real estate — — — — — 408 — 32 440 Consumer and other 13 — — — — — — — 13 Total $ 6,687 $ 5,111 $ 13,851 $ 3,959 $ 2,795 $ 3,423 $ 11,566 $ 6,321 $ 53,713 December 31, 2020 2020 2019 2018 2017 2016 Prior Revolving Loans Revolving Loans Converted to Term Total Commercial and industrial $ 9,479 $ 3,351 $ 1,846 $ 1,489 $ 105 $ 29 $ 839 $ 2,711 $ 19,849 Energy 2,421 6,772 2,144 — — 359 11,193 279 23,168 Paycheck Protection Program — — — — — — — — — Commercial real estate: Buildings, land and other 2,914 5,031 999 2,019 1,933 2,736 105 — 15,737 Construction 1,684 — — — — — — — 1,684 Consumer real estate — — — 211 — 408 259 115 993 Consumer and other — — — — — — 18 — 18 Total $ 16,498 $ 15,154 $ 4,989 $ 3,719 $ 2,038 $ 3,532 $ 12,414 $ 3,105 $ 61,449 In the tables above, loans reported as 2021 originations as of December 31, 2021 and loans reported as 2020 originations as of December 31, 2020 were, for the most part, first originated in various years prior to 2021 and 2020, 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 $1.8 million in 2021, $2.9 million in 2020 and $3.9 million in 2019. An age analysis of past due loans (including both accruing and non-accruing loans), segregated by class of loans, as of December 31, 2021 is presented in the following table. Despite their past due status, Paycheck Protection Plan loans are fully guaranteed by the SBA. Loans Loans Total Past Current Total Loans Accruing Commercial and industrial $ 34,096 $ 12,364 $ 46,460 $ 5,318,494 $ 5,364,954 $ 7,802 Energy 1,451 7,867 9,318 1,068,474 1,077,792 215 Paycheck Protection Program 4,979 18,766 23,745 405,137 428,882 18,766 Commercial real estate: Buildings, land and other 37,899 14,136 52,035 6,220,304 6,272,339 8,687 Construction 188 — 188 1,304,083 1,304,271 — Consumer real estate 4,877 2,513 7,390 1,403,400 1,410,790 2,177 Consumer and other 4,185 1,076 5,261 472,108 477,369 1,076 Total $ 87,675 $ 56,722 $ 144,397 $ 16,192,000 $ 16,336,397 $ 38,723 Troubled Debt Restructurings . The restructuring of a loan is considered a “troubled debt restructuring” if both (i) the borrower is experiencing financial difficulties and (ii) the creditor has granted a concession. Concessions may include interest rate reductions or below market interest rates, principal forgiveness, restructuring amortization schedules, reductions in collateral and other actions intended to minimize potential losses. Troubled debt restructurings that occurred during 2021, 2020 and 2019 are set forth in the following table. 2021 2020 2019 Balance at Balance at Balance at Balance at Balance at Balance at Commercial and industrial $ 1,312 $ 1,162 $ 3,661 $ 192 $ 3,845 $ 2,161 Energy 3,817 721 2,432 2,421 — — Commercial real estate: Buildings, land and other 1,888 1,862 9,310 4,922 9,457 9,393 Construction — — 1,017 1,017 — — Consumer real estate — — — — 124 120 Consumer and other — — 1,104 — — — $ 7,017 $ 3,745 $ 17,524 $ 8,552 $ 13,426 $ 11,674 Loan modifications are typically related to extending amortization periods, converting loans to interest only for a limited period of time, deferral of interest payments, waiver of certain covenants, consolidating notes and/or reducing collateral or interest rates. The modifications during the reported periods did not significantly impact our determination of the allowance for credit losses on loans. Additional information related to restructured loans was as follows: 2021 2020 2019 Restructured loans past due in excess of 90 days at period-end: Number of loans 2 1 4 Dollar amount of loans $ 1,027 $ 2,008 $ 3,340 Restructured loans on non-accrual status at period end 3,439 8,552 5,576 Charge-offs of restructured loans: Recognized in connection with restructuring — 337 — Recognized on previously restructured loans 4,278 3,894 1,500 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, 2021 and 2020. Paycheck Protection Program (“PPP”) loans are excluded as such loans are fully guaranteed by the Small Business Administration (“SBA”). December 31, 2021 2021 2020 2019 2018 2017 Prior Revolving Loans Revolving Loans Converted to Term Total Commercial and industrial Risk grades 1-8 $ 1,567,883 $ 657,529 $ 350,563 $ 179,209 $ 146,064 $ 131,201 $ 1,987,061 $ 44,337 $ 5,063,847 Risk grade 9 32,866 21,094 24,683 26,327 612 11,419 65,131 5,738 187,870 Risk grade 10 27,961 6,273 4,047 4,357 1,021 98 14,091 1,289 59,137 Risk grade 11 1,178 4,572 8,068 2,450 2,460 221 4,714 7,855 31,518 Risk grade 12 456 2,495 3,828 1,756 347 353 613 2,687 12,535 Risk grade 13 180 1,361 1,219 64 418 — 4,022 2,783 10,047 $ 1,630,524 $ 693,324 $ 392,408 $ 214,163 $ 150,922 $ 143,292 $ 2,075,632 $ 64,689 $ 5,364,954 W/A risk grade 5.91 6.30 6.89 7.06 5.91 5.80 6.21 8.04 6.22 Energy Risk grades 1-8 $ 445,489 $ 8,075 $ 9,259 $ 6,441 $ 3,110 $ 4,368 $ 464,454 $ 67,174 $ 1,008,370 Risk grade 9 19,274 611 1,775 187 — 724 11,635 2,416 36,622 Risk grade 10 — 101 631 511 — — — 530 1,773 Risk grade 11 10,260 752 3,968 1,016 — 546 — 52 16,594 Risk grade 12 — — 3,888 246 — — 4,000 819 8,953 Risk grade 13 — — 1,470 1,079 — — 2,931 — 5,480 $ 475,023 $ 9,539 $ 20,991 $ 9,480 $ 3,110 $ 5,638 $ 483,020 $ 70,991 $ 1,077,792 W/A risk grade 6.21 7.81 9.34 8.60 7.12 7.63 5.61 6.46 6.06 Commercial real estate: Buildings, land, other Risk grades 1-8 $ 1,707,550 $ 1,096,274 $ 874,130 $ 533,362 $ 492,492 $ 713,268 $ 52,150 $ 105,696 $ 5,574,922 Risk grade 9 16,302 145,340 52,427 43,806 27,188 27,767 4,445 4,258 321,533 Risk grade 10 28,209 13,813 69,643 46,250 64,950 46,582 — — 269,447 Risk grade 11 3,455 1,321 8,720 7,788 26,107 34,970 3,000 5,779 91,140 Risk grade 12 5,838 307 3,446 814 2,030 2,662 — — 15,097 Risk grade 13 200 — — — — — — — 200 $ 1,761,554 $ 1,257,055 $ 1,008,366 $ 632,020 $ 612,767 $ 825,249 $ 59,595 $ 115,733 $ 6,272,339 W/A risk grade 7.19 7.18 7.35 7.39 7.34 7.01 7.06 7.02 7.22 Construction Risk grades 1-8 $ 657,471 $ 262,176 $ 178,226 $ 2,339 $ 38 $ 1,930 $ 160,020 $ — $ 1,262,200 Risk grade 9 35,721 4,956 — — 446 — — — 41,123 Risk grade 10 — — — — — — — — — Risk grade 11 — — — — — — — — — Risk grade 12 — 748 — — — — — — 748 Risk grade 13 — 200 — — — — — — 200 $ 693,192 $ 268,080 $ 178,226 $ 2,339 $ 484 $ 1,930 $ 160,020 $ — $ 1,304,271 W/A risk grade 7.17 6.56 7.60 7.51 8.92 6.73 6.79 — 7.06 Total commercial real estate $ 2,454,746 $ 1,525,135 $ 1,186,592 $ 634,359 $ 613,251 $ 827,179 $ 219,615 $ 115,733 $ 7,576,610 W/A risk grade 7.18 7.07 7.39 7.39 7.34 7.00 6.86 7.02 7.19 December 31, 2020 2020 2019 2018 2017 2016 Prior Revolving Loans Revolving Loans Converted to Term Total Commercial and industrial Risk grades 1-8 $ 1,300,844 $ 552,885 $ 290,088 $ 226,232 $ 107,063 $ 113,458 $ 1,852,341 $ 63,210 $ 4,506,121 Risk grade 9 50,785 37,865 33,961 20,851 12,348 5,510 85,756 9,122 256,198 Risk grade 10 31,333 7,361 11,379 6,749 710 113 65,180 3,152 125,977 Risk grade 11 4,700 7,002 6,551 3,416 1,426 140 15,005 8,956 47,196 Risk grade 12 6,899 2,399 1,195 1,005 105 29 480 2,416 14,528 Risk grade 13 2,580 952 651 484 — — 359 295 5,321 $ 1,397,141 $ 608,464 $ 343,825 $ 258,737 $ 121,652 $ 119,250 $ 2,019,121 $ 87,151 $ 4,955,341 W/A risk grade 6.19 6.88 7.22 6.39 6.32 5.84 6.38 7.51 6.45 Energy Risk grades 1-8 $ 403,156 $ 18,911 $ 9,759 $ 8,083 $ 1,415 $ 4,326 $ 494,946 $ 27,548 $ 968,144 Risk grade 9 105,772 2,272 1,743 — — — 18,194 5,566 133,547 Risk grade 10 703 4,049 1,339 — 759 — 37,637 1,940 46,427 Risk grade 11 12,218 16,849 1,325 — — 661 30,124 2,735 63,912 Risk grade 12 1,101 4,580 654 — — 359 6,768 279 13,741 Risk grade 13 1,320 2,192 1,490 — — — 4,425 — 9,427 $ 524,270 $ 48,853 $ 16,310 $ 8,083 $ 2,174 $ 5,346 $ 592,094 $ 38,068 $ 1,235,198 W/A risk grade 6.86 9.57 8.68 7.40 7.85 8.06 6.45 8.20 6.85 Commercial real estate: Buildings, land, other Risk grades 1-8 $ 1,544,558 $ 947,102 $ 749,879 $ 605,152 $ 432,941 $ 661,301 $ 56,600 $ 50,340 $ 5,047,873 Risk grade 9 45,527 81,224 75,893 45,485 26,745 37,728 10,521 2,104 325,227 Risk grade 10 14,183 36,414 45,014 71,814 25,343 60,225 200 5,261 258,454 Risk grade 11 22,633 16,302 11,916 39,727 8,655 42,904 6,977 248 149,362 Risk grade 12 2,714 5,031 999 2,019 1,683 2,736 42 — 15,224 Risk grade 13 200 — — — 250 — 63 — 513 $ 1,629,815 $ 1,086,073 $ 883,701 $ 764,197 $ 495,617 $ 804,894 $ 74,403 $ 57,953 $ 5,796,653 W/A risk grade 7.13 7.36 7.54 7.55 7.54 7.20 7.54 7.12 7.34 Construction Risk grades 1-8 $ 374,661 $ 436,077 $ 168,517 $ 67 $ 1,144 $ 1,758 $ 127,801 $ — $ 1,110,025 Risk grade 9 37,430 16,567 — 2,848 — — 14,311 1,131 72,287 Risk grade 10 5,846 — 27,653 — — — 5,463 — 38,962 Risk grade 11 856 — — — — — — — 856 Risk grade 12 1,684 — — — — — — — 1,684 Risk grade 13 — — — — — — — — — $ 420,477 $ 452,644 $ 196,170 $ 2,915 $ 1,144 $ 1,758 $ 147,575 $ 1,131 $ 1,223,814 W/A risk grade 6.82 7.18 8.08 8.95 7.30 6.44 7.29 9.00 7.22 Total commercial real estate $ 2,050,292 $ 1,538,717 $ 1,079,871 $ 767,112 $ 496,761 $ 806,652 $ 221,978 $ 59,084 $ 7,020,467 W/A risk grade 7.06 7.31 7.64 7.56 7.54 7.20 7.37 7.15 7.32 At December 31, 2021 and 2020, the weighted-average risk grades for “pass grade” (risk grades 1-8) loans were 6.01 and 6.13, respectively, for commercial and industrial; 5.78 and 5.99, respectively, for energy; 6.91 and 6.97, respectively, for commercial real estate - buildings, land and other; and 6.99 and 6.99, respectively, for commercial real estate - construction. Furthermore, in the tables above, there are loans reported as 2021 originations as of December 31, 2021 and 2020 originations as of December 31, 2020 that have risk grades of 11 or higher. These loans were, for the most part, first originated in various years prior to 2021 and 2020, 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, 2021 and December 31, 2020 was as follows: December 31, 2021 2021 2020 2019 2018 2017 Prior Revolving Loans Revolving Loans Converted to Term Total Consumer real estate: Past due 30-89 days $ 280 $ 204 $ 406 $ 489 $ 296 $ 1,344 $ 126 $ 1,732 $ 4,877 Past due 90 or more days — — — 154 355 828 991 185 2,513 Total past due 280 204 406 643 651 2,172 1,117 1,917 7,390 Current loans 319,042 251,160 95,900 55,893 48,841 116,423 505,333 10,808 1,403,400 Total $ 319,322 $ 251,364 $ 96,306 $ 56,536 $ 49,492 $ 118,595 $ 506,450 $ 12,725 $ 1,410,790 Consumer and other: Past due 30-89 days $ 1,600 $ 91 $ 120 $ 38 $ 51 $ 17 $ 325 $ 1,943 $ 4,185 Past due 90 or more days 548 — 45 — — — 34 449 1,076 Total past due 2,148 91 165 38 51 17 359 2,392 5,261 Current loans 46,708 17,843 6,215 2,684 1,708 1,158 371,866 23,926 472,108 Total $ 48,856 $ 17,934 $ 6,380 $ 2,722 $ 1,759 $ 1,175 $ 372,225 $ 26,318 $ 477,369 December 31, 2020 2020 2019 2018 2017 2016 Prior Revolving Loans Revolving Loans Converted to Term Total Consumer real estate: Past due 30-89 days $ 225 $ 1,038 $ 1,556 $ 553 $ 628 $ 2,907 $ 652 $ 531 $ 8,090 Past due 90 or more days 15 139 109 706 25 1,287 615 151 3,047 Total past due 240 1,177 1,665 1,259 653 4,194 1,267 682 11,137 Current loans 336,441 166,323 94,374 80,625 66,241 124,590 434,939 16,104 1,319,637 Total $ 336,681 $ 167,500 $ 96,039 $ 81,884 $ 66,894 $ 128,784 $ 436,206 $ 16,786 $ 1,330,774 Consumer and other: Past due 30-89 days $ 1,750 $ 300 $ 453 $ 52 $ 17 $ — $ 2,238 $ 727 $ 5,537 Past due 90 or more days 71 10 118 — — — 1,031 21 1,251 Total past due 1,821 310 571 52 17 — 3,269 748 6,788 Current loans 45,286 27,813 5,397 2,799 1,705 572 386,791 28,529 498,892 Total $ 47,107 $ 28,123 $ 5,968 $ 2,851 $ 1,722 $ 572 $ 390,060 $ 29,277 $ 505,680 Revolving loans that converted to term during 2021 and 2020 were as follows: 2021 2020 Commercial and industrial $ 40,099 $ 47,562 Energy 54,996 33,150 Commercial real estate: Buildings, land and other 68,337 10,505 Construction — 1,131 Consumer real estate 1,156 2,264 Consumer and other 8,367 16,395 Total $ 172,955 $ 111,007 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 134.7 at December 31, 2021 and 118.1 at December 31, 2020. A higher TLI value implies more favorable economic conditions. Allowance For Credit Losses - Loans. The allowance for credit losses on loans is a contra-asset valuation account, calculated in accordance with ASC 326, that is deducted from the amortized cost basis of loans to present the net amount expected to be collected. The amount of the allowance represents management's best estimate of current expected credit losses on loans considering available information, from internal and external sources, relevant to assessing collectibility over the loans' contractual terms, adjusted for expected prepayments when appropriate. The contractual term excludes expected extensions, renewals and modifications unless (i) management has a reasonable expectation that a trouble debt restructuring will be executed with an individual borrower 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 and energy - non-revolving, (ii) commercial and industrial and energy - revolving, (iii) commercial real estate - owner occupied, (iv) commercial real estate - non-owner occupied, (v) commercial real estate - construction/land development, (vi) consumer real estate and (vii) consumer and other. 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 rec

Premises and Equipment

Premises and Equipment	12 Months Ended
	Dec. 31, 2021
Property, Plant and Equipment [Abstract]
Premises and Equipment	Premises and Equipment and Lease Commitments Year-end premises and equipment were as follows: 2021 2020 Land $ 152,219 $ 128,739 Buildings 495,903 458,693 Technology, furniture and equipment 256,323 243,395 Leasehold improvements 192,207 183,827 Construction and projects in progress 14,513 41,202 Lease right-of-use assets 281,438 292,087 1,392,603 1,347,943 Less accumulated depreciation and amortization (342,272) (302,365) Total premises and equipment, net $ 1,050,331 $ 1,045,578 Depreciation of premises and equipment totaled $55.1 million in 2021, $49.9 million 2020 and $41.0 million in 2019. Lease Commitments . We lease certain office facilities and office equipment under operating leases. Rent expense for all operating leases totaled $45.6 million in 2021, $46.0 million in 2020 and $42.1 million in 2019. On January 1, 2019, we adopted a new accounting standard which required the recognition of certain operating leases on our balance sheet as lease right-of-use assets (reported as component of premises and equipment) and related lease liabilities (reported as a component of accrued interest payable and other liabilities). See Note 1 - Summary of Significant Accounting Policies. The components of total lease expense in 2021 and 2020 were as follows: 2021 2020 Amortization of lease right-of-use assets $ 32,811 $ 32,772 Short-term lease expense 1,595 1,799 Non-lease components (including taxes, insurance, common maintenance, etc.) 11,203 11,396 Total $ 45,609 $ 45,967 Right-of-use lease assets totaled $281.4 million and $292.1 million at December 31, 2021 and 2020, respectively, and are reported as a component of premises and equipment on our accompanying consolidated balance sheets. The related lease liabilities totaled $313.4 million and $323.0 million at December 31, 2021 and 2020, 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 2021 and $31.6 million during 2020. 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, 2021: Future lease payments 2022 $ 32,222 2023 31,458 2024 29,398 2025 28,253 2026 27,833 Thereafter 245,819 Total undiscounted operating lease liability 394,983 Imputed interest 81,579 Total operating lease liability included in the accompanying balance sheet $ 313,404 Weighted-average lease term in years 14.73 Weighted-average discount rate 3.05% We lease certain buildings and branch facilities from various entities which are controlled by or affiliated with certain directors. Payments related to these leases totaled $322 thousand in 2021, $9.8 million in 2020 and $5.9 million in 2019. The decrease in these lease payments during 2021 was the result of a director who did not stand for re-election and who has a controlling interest in the entity from which we lease our headquarters building. This lease originally commenced during the second quarter of 2019 and we recognized a right-of-use asset totaling $121.7 million and a related lease liability totaling $121.7 million in connection with this lease. The lease was a separate agreement under a comprehensive development agreement between us, the City of San Antonio and a third party controlled by the aforementioned director.

Goodwill and Other Intangible A

Goodwill and Other Intangible Assets	12 Months Ended
	Dec. 31, 2021
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill and Other Intangible Assets	Goodwill and Other Intangible Assets Goodwill . Year-end goodwill was as follows: 2021 2020 Goodwill $ 654,952 $ 654,952 Other Intangible Assets. Year-end other intangible assets were as follows: Gross Accumulated Net 2021 Core deposits $ 9,300 $ (8,582) $ 718 Customer relationships 2,385 (2,237) 148 $ 11,685 $ (10,819) $ 866 2020 Core deposits $ 9,300 $ (8,004) $ 1,296 Customer relationships 2,886 (2,619) 267 $ 12,186 $ (10,623) $ 1,563 Other intangible assets are amortized on an accelerated basis over their estimated lives, which range from 5 to 10 years. Amortization expense related to intangible assets totaled $697 thousand in 2021, $918 thousand in 2020, and $1.2 million in 2019. The estimated aggregate future amortization expense for intangible assets remaining as of December 31, 2021 is as follows: 2022 $ 481 2023 282 2024 87 2025 11 2026 5 Thereafter — $ 866

Deposits

Deposits	12 Months Ended
	Dec. 31, 2021
Deposits [Abstract]
Deposits	Deposits Year-end deposits were as follows: 2021 2020 Non-interest-bearing demand deposits $ 18,423,018 $ 15,117,051 Interest-bearing deposits: Savings and interest checking 11,930,959 9,730,292 Money market accounts 11,228,815 9,027,655 Time accounts 1,112,904 1,140,763 Total interest-bearing deposits 24,272,678 19,898,710 Total deposits $ 42,695,696 $ 35,015,761 The following table presents additional information about our year-end deposits: 2021 2020 Deposits from the Certificate of Deposit Account Registry Service (CDARS) $ — $ 372 Deposits from foreign sources (primarily Mexico) 993,479 884,169 Non-interest-bearing public funds deposits 1,235,026 960,072 Interest-bearing public funds deposits 810,863 652,761 Total deposits not covered by deposit insurance 24,125,359 18,694,320 Time deposits not covered by deposit insurance 238,608 237,298 Deposits from certain directors, executive officers and their affiliates 276,556 210,389 Scheduled maturities of time deposits at December 31, 2021 were as follows: 2022 $ 891,392 2023 221,512 $ 1,112,904 Scheduled maturities of time deposits not covered by deposit insurance at December 31, 2021, were as follows: Due within 3 months or less $ 92,403 Due after 3 months and within 6 months 34,038 Due after 6 months and within 12 months 58,357 Due after 12 months 53,810 $ 238,608

Borrowed Funds

Borrowed Funds	12 Months Ended
	Dec. 31, 2021
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 $822 thousand and $1.0 million December 31, 2021 and 2020. Proceeds from sale of the notes were used for general corporate purposes. Junior Subordinated Deferrable Interest Debentures. At December 31, 2021 and 2020, 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 $701 thousand and $758 thousand at December 31, 2021 and 2020. At December 31, 2020, we also had $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. The junior subordinated deferrable interest debentures issued to WNB Trust and the trust preferred securities issued by WNB Trust were redeemed in October 2021. 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 LIBOR plus a margin of 1.55%) trust preferred securities, which represent beneficial interests in the assets of the trust. 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 LIBOR plus a margin of 1.55%, which was equal to 1.72% and 1.78% at December 31, 2021 and 2020) 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. WNB Trust was formed in 2004 by WNB for the purpose of issuing $13.0 million of floating rate trust preferred securities, which represented beneficial interests in the assets of the trust. The proceeds of the offering of the trust preferred securities along with $403 thousand in proceeds from the issuance of common equity securities were used to purchase $13.4 million of floating rate (three-month LIBOR plus a margin of 2.35%, which was equal to 2.56% at December 31, 2020) junior subordinated deferrable interest debentures issued by WNB, which had terms substantially similar to the trust preferred securities. As noted above, the junior subordinated deferrable interest debentures issued to WNB Trust and the trust preferred securities issued by WNB Trust were redeemed in October 2021. Although the accounts of Trust II and WNB Trust are not included in our consolidated financial statements, the trust preferred securities issued by these are included in the capital of Cullen/Frost for regulatory capital purposes. See Note 9 - Capital and Regulatory Matters.

Off-Balance-Sheet Arrangements,

Off-Balance-Sheet Arrangements, Commitments, Guarantees and Contingencies	12 Months Ended
	Dec. 31, 2021
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. 2021 2020 Commitments to extend credit $ 10,420,142 $ 9,814,475 Standby letters of credit 238,690 241,345 Deferred standby letter of credit fees 2,072 1,723 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. The following table details activity in the allowance for credit losses on off-balance-sheet credit exposures. 2021 2020 2019 Beginning balance $ 44,152 $ 500 $ 500 Impact of adopting ASC 326 — 39,377 — Credit loss expense 6,162 4,275 — Ending balance $ 50,314 $ 44,152 $ 500 Credit Card Guarantees . We guarantee the credit card debt of certain customers to the merchant bank that issues the cards. At December 31, 2021 and 2020, the guarantees totaled approximately $8.6 million and $9.1 million, of which amounts, $962 thousand and $8.2 million 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 $43.3 billion and $38.6 billion at December 31, 2021 and 2020, 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, 2021
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 delay, 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, 2021 and 2020 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, 2021 or 2020. 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. At December 31, 2021 and 2020, Cullen/Frost's Tier 2 capital included $120.0 million and $133.0 million of trust preferred securities, respectively. The $13.0 million of trust preferred securities issued by WNB Capital Trust I were redeemed in October 2021. At both December 31, 2021 and 2020, Tier 2 Capital for Cullen/Frost also included $100.0 million 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. As discussed in Note 1 - Significant Accounting Policies, in connection with the adoption of ASC 326, we recognized an after-tax cumulative effect reduction to retained earnings totaling $29.3 million on January 1, 2020. In February 2019, the federal bank regulatory agencies issued a final rule (the “2019 CECL Rule”) that revised certain capital regulations to account for changes to credit loss accounting under U.S. GAAP. The 2019 CECL Rule included a transition option that allows banking organizations to phase in, over a three-year period, the day-one adverse effects of CECL on their regulatory capital ratios (three-year transition option). In March 2020, the federal bank regulatory agencies issued an interim final rule that maintains the three-year transition option of the 2019 CECL Rule and also provides banking organizations that were required under U.S. GAAP (as of January 2020) to implement CECL before the end of 2020 the option to delay for two years an estimate of the effect of CECL on regulatory capital, relative to the incurred loss methodology’s effect on regulatory capital, followed by a three five five In April 2020, we began originating loans to qualified small businesses under the PPP administered by the SBA. Federal bank regulatory agencies have issued an interim final rule that permits banks to neutralize the regulatory capital effects of participating in the Paycheck Protection Program Lending Facility (the “PPP Facility”) and clarify that PPP loans have a zero percent risk weight under applicable risk-based capital rules. Specifically, a bank may exclude all PPP loans pledged as collateral to the PPP Facility from its average total consolidated assets for the purposes of calculating its leverage ratio, while PPP loans that are not pledged as collateral to the PPP Facility will be included. Our PPP loans are included in the calculation of our leverage ratio as of December 31, 2021 as we did not utilize the PPP Facility for funding purposes. The following table presents actual and required capital ratios as of December 31, 2021 and December 31, 2020 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 - Basel III Fully Phased-In Required to be Capital Ratio Capital Ratio Capital Ratio 2021 Common Equity Tier 1 to Risk-Weighted Assets Cullen/Frost $ 3,371,043 13.13 % $ 1,796,549 7.00 % $ 1,668,224 6.50 % Frost Bank 3,261,532 12.72 1,795,221 7.00 1,666,991 6.50 Tier 1 Capital to Risk-Weighted Assets Cullen/Frost 3,516,495 13.70 2,181,523 8.50 2,053,198 8.00 Frost Bank 3,261,532 12.72 2,179,911 8.50 2,051,681 8.00 Total Capital to Risk-Weighted Assets Cullen/Frost 3,966,244 15.45 2,694,823 10.50 2,566,498 10.00 Frost Bank 3,491,281 13.61 2,692,831 10.50 2,564,601 10.00 Leverage Ratio Cullen/Frost 3,516,495 7.34 1,917,533 4.00 2,396,917 5.00 Frost Bank 3,261,532 6.80 1,917,679 4.00 2,397,099 5.00 2020 Common Equity Tier 1 to Risk-Weighted Assets Cullen/Frost $ 3,058,447 12.86 % $ 1,664,867 7.00 % $ 1,545,948 6.50 % Frost Bank 3,030,093 12.77 1,661,620 7.00 1,542,933 6.50 Tier 1 Capital to Risk-Weighted Assets Cullen/Frost 3,203,899 13.47 2,021,624 8.50 1,902,705 8.00 Frost Bank 3,030,093 12.77 2,017,682 8.50 1,898,995 8.00 Total Capital to Risk-Weighted Assets Cullen/Frost 3,672,912 15.44 2,497,300 10.50 2,378,381 10.00 Frost Bank 3,266,106 13.76 2,492,430 10.50 2,373,743 10.00 Leverage Ratio Cullen/Frost 3,203,899 8.07 1,589,004 4.00 1,986,255 5.00 Frost Bank 3,030,093 7.63 1,588,200 4.00 1,985,250 5.00 As of December 31, 2021, 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, 2021 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, 2021, that Cullen/Frost and Frost Bank meet all capital adequacy requirements to which they are subject. Series B Preferred Stock. On November 19, 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. Series A Preferred Stock. On February 15, 2013, we issued and sold 6,000,000 shares, or $150.0 million in aggregate liquidation preference, of our 5.375% Non-Cumulative Perpetual Preferred Stock, Series A, par value $0.01 and liquidation preference $25 per share (“Series A Preferred Stock”). On March 16, 2020, we redeemed all of the outstanding shares of our Series A Preferred Stock at a redemption price of $25 per share, or an aggregate redemption of $150.0 million. When issued, the net proceeds of the Series A Preferred Stock totaled $144.5 million after deducting $5.5 million of issuance costs including the underwriting discount and professional service fees, among other things. Upon redemption, these issuance costs were reclassified to retained earnings and reported as a reduction of net income available to common shareholders. Prior to redemption, dividends on the Series A Preferred Stock were paid quarterly, in arrears, at a rate of 5.375% per annum and the Series A Preferred Stock qualified as Tier 1 capital for the purposes of regulatory capital calculations. Stock Repurchase Plans. From time to time, our board of directors has authorized stock repurchase plans. In general, stock repurchase plans allow us to proactively manage our capital position and return excess capital to shareholders. Shares purchased under such plans also provide us with shares of common stock necessary to satisfy obligations related to stock compensation awards. On January 26, 2022, our board of directors authorized a $100.0 million stock repurchase plan, allowing us to repurchase shares of our common stock over a one Dividend Restrictions . In the ordinary course of business, Cullen/Frost is dependent upon dividends from Frost Bank to provide funds for the payment of dividends to shareholders and to provide for other cash requirements, including to repurchase its common stock. Banking regulations may limit the amount of dividends that may be paid. Approval by regulatory authorities is required if the effect of dividends declared would cause the regulatory capital of Frost Bank to fall below specified minimum levels. Approval is also required if dividends declared exceed the net profits for that year combined with the retained net profits for the preceding two years. Under the foregoing dividend restrictions and while maintaining its “well capitalized” status, at December 31, 2021, Frost Bank could pay aggregate dividends of up to $494.1 million 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.

Earnings Per Common Share

Earnings Per Common Share	12 Months Ended
	Dec. 31, 2021
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. 2021 2020 2019 Net Income $ 443,079 $ 331,151 $ 443,599 Less: Preferred stock dividends 7,157 2,016 8,063 Redemption of preferred stock — 5,514 — Net income available to common shareholders 435,922 323,621 435,536 Less: Earnings allocated to participating securities 3,881 3,136 3,687 Net earnings allocated to common stock $ 432,041 $ 320,485 $ 431,849 Distributed earnings allocated to common stock $ 187,202 $ 178,863 $ 175,540 Undistributed earnings allocated to common stock 244,839 141,622 256,309 Net earnings allocated to common stock $ 432,041 $ 320,485 $ 431,849 Weighted-average shares outstanding for basic earnings per common share 63,612,658 62,727,053 62,741,769 Dilutive effect of stock compensation 489,462 276,784 700,101 Weighted-average shares outstanding for diluted earnings per common share 64,102,120 63,003,837 63,441,870

Employee Benefit Plans

Employee Benefit Plans	12 Months Ended
	Dec. 31, 2021
Retirement Benefits [Abstract]
Employee Benefit Plans	Employee Benefit Plans Retirement Plans Profit Sharing Plan. Prior to 2019, we maintained a qualified defined contribution profit sharing plan that covered employees who had completed at least one year of service and were age 21 or older. The Plan was merged with and into our 401(k) plan effective January 1, 2019. We continue to maintain a separate non-qualified profit sharing plan for certain employees whose participation in the qualified profit sharing plan was limited. The plan offers such employees an alternative means of receiving comparable benefits. Expense related to this plan was not significant during 2021, 2020 and 2019. 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: 2021 2020 2019 Change in plan assets: Fair value of plan assets at beginning of year $ 182,088 $ 174,173 $ 152,820 Actual return on plan assets 24,908 16,599 29,945 Employer contributions 1,236 1,201 1,163 Benefits paid (10,485) (9,885) (9,755) Fair value of plan assets at end of year 197,747 182,088 174,173 Change in benefit obligation: Benefit obligation at beginning of year 197,593 186,641 167,107 Interest cost 3,341 5,010 6,472 Actuarial (gain) loss (4,524) 15,827 22,817 Benefits paid (10,485) (9,885) (9,755) Benefit obligation at end of year 185,925 197,593 186,641 Funded status of the plan at end of year and accrued benefit (liability) recognized $ 11,822 $ (15,505) $ (12,468) Accumulated benefit obligation at end of year $ 185,925 $ 197,593 $ 186,641 Certain disaggregated information related to our defined benefit pension plans as of year-end was as follows: Retirement Plan Restoration Plan 2021 2020 2021 2020 Projected benefit obligation $ 170,389 $ 180,986 $ 15,536 $ 16,607 Accumulated benefit obligation 170,389 180,986 15,536 16,607 Fair value of plan assets 197,747 182,088 — — Funded status of the plan at end of year and accrued benefit (liability) recognized 27,358 1,102 (15,536) (16,607) The components of the combined net periodic cost (benefit) for our defined benefit pension plans are presented in the table below. 2021 2020 2019 Expected return on plan assets, net of expenses $ (12,839) $ (12,289) $ (10,772) Interest cost on projected benefit obligation 3,341 5,010 6,472 Net amortization and deferral 6,116 5,319 5,623 Net periodic expense (benefit) $ (3,382) $ (1,960) $ 1,323 Amounts related to our defined benefit pension plans recognized as a component of other comprehensive income were as follows: 2021 2020 2019 Net actuarial gain (loss) $ 22,709 $ (6,199) $ 1,979 Deferred tax (expense) benefit (4,769) 1,302 (416) Other comprehensive income (loss), net of tax $ 17,940 $ (4,897) $ 1,563 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. 2021 2020 Net actuarial loss $ (41,634) $ (64,343) Deferred tax benefit 8,743 13,512 Amounts included in accumulated other comprehensive income/loss, net of tax (32,891) (50,831) 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. 2021 2020 2019 Benefit obligations: Discount rate 2.79 % 2.43 % 3.20 % Net periodic benefit cost: Discount rate 2.43 % 3.20 % 4.36 % Expected return on plan assets 7.25 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, 2021, management’s investment objective for our defined benefit plans is to achieve long-term growth. This strategy provides for a target asset allocation of approximately 62% invested in equity securities, approximately 36% 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 17 - Fair Value Measurements). Our Restoration Plan is unfunded. 2021 2020 Level 1: Mutual funds $ 195,452 $ 180,693 Cash and cash equivalents 2,295 1,395 Total fair value of plan assets $ 197,747 $ 182,088 Mutual funds include various equity, fixed-income and blended funds with varying investment strategies. Approximately 68% of mutual fund investments consist of equity investments as of December 31, 2021. The investment objective of equity funds 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 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 7.25% in the determination of the net periodic benefit cost for 2021. 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, 2021, expected future benefit payments related to our defined benefit plans were as follows: 2022 $ 11,592 2023 11,805 2024 11,975 2025 11,982 2026 12,018 2027 through 2031 56,494 $ 115,866 We expect to contribute $1.2 million to the defined benefit plans during 2022. Savings Plans 401(k) Plan and Thrift Incentive Plan. 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 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 totaled $23.8 million in 2021, $17.9 million in 2020 and $28.9 million in 2019. We maintain a thrift incentive stock purchase plan to offer certain employees whose participation in the 401(k) plan is limited an alternative means of receiving comparable benefits. Expense related to this plan was not significant during 2021, 2020 and 2019. 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 2021, 2020 and 2019 was 30,723, 48,409 and 34,317, respectively. As of December 31, 2021, there were 777,687 shares remaining available for grant for future awards. Director Deferred Non-Vested Stock Performance Stock Units Outstanding Stock Options Number of Units Weighted- Number Weighted- Number of Units Weighted- Number Weighted- January 1, 2019 48,910 $ 71.14 383,797 $ 85.59 125,809 $ 82.55 2,352,008 $ 63.55 Granted 7,592 102.70 127,091 93.46 51,479 85.74 — — Exercised/vested (1,132) 106.03 (53,990) 65.11 — — (359,892) 57.71 Forfeited/expired — — (16,251) 89.71 — — (11,250) 65.11 December 31, 2019 55,370 74.76 440,647 90.22 177,288 83.48 1,980,866 64.60 Granted 10,428 73.84 151,038 66.79 72,618 57.89 — — Exercised/vested (12,938) 71.09 (117,990) 76.07 (41,755) 69.70 (235,880) 53.23 Forfeited/expired — — (3,336) 91.07 (6,894) 81.33 (5,427) 75.74 December 31, 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 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 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 2021 base-year amount. Adjusted net revenue for the three-year performance period is calculated as the sum of taxable-equivalent net interest income (excluding the effects of PPP lending) and non-interest income, reduced by non-interest expense (excluding the effects of PPP lending) and net charge-offs. The 2021 base-year adjusted net revenue amount of approximately $426.6 million was calculated as the sum of taxable-equivalent net interest income (excluding the effects of PPP lending) and non-interest income, reduced by non-interest expense (excluding the effects of PPP lending) and the product of average total loans (excluding PPP loans) and 0.30%. The ultimate number of shares issuable under each performance award is the product of the award target and the award payout percentage for the given level of achievement. The level of achievement is measured as the amount by which adjusted net revenue, averaged over a three-year performance period, exceeds the 2021 base-year amount, stated as an average growth percentage. The award payout percentages by level of achievement are as follows: (i) less than 13% average growth pays out at 0% of target, (ii) 13% average growth pays out at 50% of target, (iii) 19% average growth pays out at 100% of target and (iv) 25% average growth or more pays out at 150% of target. Achievement between the aforementioned average growth percentages will result in an award payout percentage determined based on straight-line interpolation between the percentages. 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. The ultimate number of shares issuable under each performance award is the product of the award target and the award payout percentage for the given level of achievement. The level of achievement is measured as the percentile rank of relative return on assets among the peer group. The award payout percentages by level of achievement are as follows: (i) less than 25th percentile pays out at 0% of target, (ii) 25th percentile pays out at 50% of target, (iii) 50th percentile pays out at 100% of target and (iv) 75th percentile or more pays out at 150% of target. Achievement between the aforementioned percentiles will result in an award payout percentage determined based on straight-line interpolation between the percentiles. 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, 2021 is as follows: Options Outstanding Options Exercisable Range of Number Weighted- Weighted- Number Weighted- $ 50.01 to $ 55.00 123,314 $ 54.56 0.81 123,314 $ 54.56 65.01 to 70.00 319,081 65.11 3.72 319,081 65.11 70.01 to 75.00 169,726 71.39 1.78 169,726 71.39 75.01 to 80.00 265,560 78.92 2.75 265,560 78.92 Total 877,681 69.02 2.64 877,681 69.02 Total intrinsic value $ 50,070 $ 50,070 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: 2021 2020 2019 Shares issued from available treasury stock 987,758 408,563 399,224 Proceeds from stock option exercises $ 54,417 $ 12,557 $ 20,770 Intrinsic value of stock options exercised 43,904 5,365 13,713 Fair value of stock awards/units vested 15,751 12,773 5,192 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 stock units granted to all participants, the service period does not extend past the date the participant reaches 65 years of age. Deferred stock units granted to non-employee directors generally have immediate vesting and the related expense is fully recognized on the date of grant. For performance stock units, the service period generally matches the three-year performance period specified by the award, however, the service period does not extend past the date the participant reaches 65 years of age. Expense recognized each period is dependent upon our estimate of the number of shares that will ultimately be issued. Stock-based compensation expense 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. 2021 2020 2019 Stock options $ — $ — $ 1,185 Non-vested stock awards/stock units 9,977 10,240 9,339 Deferred stock-units 700 770 780 Performance stock units 2,076 2,908 4,642 Total $ 12,753 $ 13,918 $ 15,946 Income tax benefit $ 1,713 $ 2,142 $ 2,359 Unrecognized stock-based compensation expense and the weighted-average period over which the expense is expected to be recognized at December 31, 2021 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 stock awards/stock units $ 18,431 2.07 Performance stock units 9,818 2.16 Total $ 28,249 Valuation of Stock-Based Compensation . For the purposes of recognizing stock-based compensation expense, the fair value of non-vested stock awards/stock units and 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 $0.75, $0.72 and $0.71 in 2021, 2020, and 2019, respectively, discounted at a weighted-average risk-free rate of 0.77%, 0.19% and 1.65% in 2021, 2020, and 2019, respectively.

Other Non-Interest Income and E

Other Non-Interest Income and Expense	12 Months Ended
	Dec. 31, 2021
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. 2021 2020 2019 Other non-interest income: Other $ 48,528 $ 47,712 $ 43,563 Total $ 48,528 $ 47,712 $ 43,563 Other non-interest expense: Professional services $ 34,747 $ 37,253 $ 39,238 Advertising, promotions and public relations 34,539 34,390 38,001 Travel/meals and entertainment 4,946 7,109 16,459 Other 97,225 87,558 86,967 Total $ 171,457 $ 166,310 $ 180,665 In the ordinary course of business, we transact with certain directors and/or their affiliates. Payments for services provided totaled $257 thousand in 2021, $551 thousand in 2020 and $567 thousand in 2019.

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2021
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes Income tax expense was as follows: 2021 2020 2019 Current income tax expense $ 38,675 $ 36,002 $ 48,256 Deferred income tax expense (benefit) 7,784 (15,832) 7,614 Income tax expense, as reported $ 46,459 $ 20,170 $ 55,870 Effective tax rate 9.5 % 5.7 % 11.2 % 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. 2021 2020 2019 Income tax expense computed at the statutory rate $ 102,803 $ 73,777 $ 104,888 Effect of tax-exempt interest (50,740) (51,624) (49,166) Tax benefit on dividends paid in our 401k plan (1,764) (1,851) (1,743) Bank owned life insurance income (517) (783) (774) Non-deductible FDIC premiums 2,629 1,790 1,267 Non-deductible compensation 1,773 1,123 1,708 Non-deductible meals and entertainment 625 786 1,299 Net tax benefit from stock-based compensation (7,877) (852) (2,447) Asset contribution to a charitable trust — (2,556) — Tax basis adjustment of premises and equipment (1,026) — — Other 553 360 838 Income tax expense, as reported $ 46,459 $ 20,170 $ 55,870 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%. 2021 2020 Deferred tax assets: Lease liabilities under operating leases $ 65,815 $ 67,839 Allowance for credit losses 62,819 64,573 Net actuarial loss on defined benefit post-retirement benefit plans 8,743 13,512 Stock-based compensation 6,989 10,033 Bonus accrual 7,506 3,961 Deferred loan and lease origination fees 3,118 10,252 Other 3,834 3,834 Total gross deferred tax assets 158,824 174,004 Deferred tax liabilities: Net unrealized gain on securities available for sale and transferred securities (101,067) (149,870) Right-of-use assets under operating leases (59,415) (61,963) Premises and equipment (49,645) (49,602) Intangible assets (16,595) (14,596) Defined benefit post-retirement benefit plans (11,027) (10,081) Partnership interests — (2,913) Leases (712) (1,090) Other (1,611) (1,387) Total gross deferred tax liabilities (240,072) (291,502) Net deferred tax asset (liability) $ (81,248) $ (117,498) No valuation allowance for deferred tax assets was recorded at December 31, 2021 and 2020 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 2018.

Other Comprehensive Income (Los

Other Comprehensive Income (Loss)	12 Months Ended
	Dec. 31, 2021
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 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) 2020 Securities available for sale and transferred securities: Change in net unrealized gain/loss during the period $ 427,331 $ 89,741 $ 337,590 Change in net unrealized gain on securities transferred to held to maturity (1,256) (264) (992) Reclassification adjustment for net (gains) losses included in net income (108,989) (22,888) (86,101) Total securities available for sale and transferred securities 317,086 66,589 250,497 Defined-benefit post-retirement benefit plans: Change in the net actuarial gain/loss (11,518) (2,419) (9,099) Reclassification adjustment for net amortization of actuarial gain/loss included in net income as a component of net periodic cost (benefit) 5,319 1,117 4,202 Total defined-benefit post-retirement benefit plans (6,199) (1,302) (4,897) Total other comprehensive income (loss) $ 310,887 $ 65,287 $ 245,600 2019 Securities available for sale and transferred securities: Change in net unrealized gain/loss during the period $ 418,556 $ 87,897 $ 330,659 Change in net unrealized gain on securities transferred to held to maturity (1,292) (271) (1,021) Reclassification adjustment for net (gains) losses included in net income (293) (62) (231) Total securities available for sale and transferred securities 416,971 87,564 329,407 Defined-benefit post-retirement benefit plans: Change in the net actuarial gain/loss (3,644) (765) (2,879) Reclassification adjustment for net amortization of actuarial gain/loss included in net income as a component of net periodic cost (benefit) 5,623 1,181 4,442 Total defined-benefit post-retirement benefit plans 1,979 416 1,563 Total other comprehensive income (loss) $ 418,950 $ 87,980 $ 330,970 Activity in accumulated other comprehensive income, net of tax, was as follows: Securities Defined Accumulated 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 Balance January 1, 2020 $ 313,304 $ (45,934) $ 267,370 Other comprehensive income (loss) before reclassification 336,598 (9,099) 327,499 Reclassification of amounts included in net income (86,101) 4,202 (81,899) Net other comprehensive income (loss) during period 250,497 (4,897) 245,600 Balance December 31, 2020 $ 563,801 $ (50,831) $ 512,970 Balance January 1, 2019 $ (16,103) $ (47,497) $ (63,600) Other comprehensive income (loss) before reclassification 329,638 (2,879) 326,759 Reclassification of amounts included in net income (231) 4,442 4,211 Net other comprehensive income (loss) during period 329,407 1,563 330,970 Balance December 31, 2019 $ 313,304 $ (45,934) $ 267,370

Derivative Financial Instrument

Derivative Financial Instruments	12 Months Ended
	Dec. 31, 2021
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, 2021 and 2020 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, 2021 and 2020. December 31, 2021 December 31, 2020 Notional Estimated Notional Estimated Derivatives designated as hedges of fair value: Financial institution counterparties: Loan/lease interest rate swaps - liabilities $ 2,426 $ (34) $ 3,724 $ (134) Non-hedging interest rate derivatives: Financial institution counterparties: Loan/lease interest rate swaps - assets 247,592 1,207 — — Loan/lease interest rate swaps - liabilities 928,756 (19,142) 1,173,173 (33,812) Loan/lease interest rate caps - assets 270,431 3,239 356,601 1,241 Customer counterparties: Loan/lease interest rate swaps - assets 928,756 39,864 1,173,173 84,424 Loan/lease interest rate swaps - liabilities 247,592 (2,846) — — Loan/lease interest rate caps - liabilities 270,431 (3,239) 356,601 (1,241) The weighted-average rates paid and received for interest rate swaps outstanding at December 31, 2021 were as follows: Weighted-Average Interest Interest Interest rate swaps: Fair value hedge loan/lease interest rate swaps 2.48 % 0.10 % Non-hedging interest rate swaps - financial institution counterparties 3.73 1.90 Non-hedging interest rate swaps - customer counterparties 1.90 3.73 The weighted-average strike rate for outstanding interest rate caps was 3.26% at December 31, 2021. 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, 2021 December 31, 2020 Notional Notional Estimated Notional Estimated Financial institution counterparties: Oil - assets Barrels 4,809 $ 14,721 3,056 $ 8,341 Oil - liabilities Barrels 7,032 (73,594) 6,391 (32,112) Natural gas - assets MMBTUs 15,947 4,143 9,281 1,529 Natural gas - liabilities MMBTUs 29,446 (21,249) 15,079 (3,265) Customer counterparties: Oil - assets Barrels 7,046 74,437 6,391 32,670 Oil - liabilities Barrels 4,796 (14,294) 3,056 (8,264) Natural gas - assets MMBTUs 29,446 21,456 17,636 3,451 Natural gas - liabilities MMBTUs 15,947 (4,124) 6,724 (1,458) Foreign Currency Derivatives . We enter into foreign currency forward 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, 2021 December 31, 2020 Notional Notional Estimated Notional Estimated Financial institution counterparties: Forward contracts - assets EUR 1,900 $ 29 — $ — Forward contracts - assets CAD 658 — — — Customer counterparties: Forward contracts - assets EUR — — — — Forward contracts - assets CAD 658 4 — — Forward contracts - liabilities EUR 1,900 (55) — — 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: 2021 2020 2019 Commercial loan/lease interest rate swaps: Amount of gain (loss) included in interest income on loans $ (91) $ (111) $ 86 Amount of (gain) loss included in other non-interest expense 10 9 — 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. 2021 2020 2019 Non-hedging interest rate derivatives: Other non-interest income $ 4,285 $ 3,413 $ 2,005 Other non-interest expense (1) 1 (1) Non-hedging commodity derivatives: Other non-interest income 4,052 1,768 503 Non-hedging foreign currency derivatives: Other non-interest income 39 28 51 Non-hedging other derivatives: Other non-interest income — 5,992 750 During 2020, we sold certain non-hedge related, short-term put options on U.S. Treasury securities and realized gains totaling approximately $6.0 million in connection with the sales. The put options expired without being exercised. Gains realized from similar transactions totaled $750 thousand in 2019. These gains are included in the table above as a component of non-hedging other derivatives. 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 interest rate swaps is limited to the net favorable value and interest payments of all swaps by each counterparty, while our credit exposure on commodity swaps/options and foreign currency forward 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. Our credit exposure relating to interest rate swaps, commodity swaps/options and foreign currency forward contracts with bank customers was approximately $118.3 million at December 31, 2021. This credit exposure is partly mitigated as transactions with customers are generally secured by the collateral, if any, securing the underlying transaction being hedged. Our credit exposure, net of collateral pledged, relating to interest rate swaps, commodity swaps/options and foreign currency forward contracts with upstream financial institution counterparties was approximately $19.7 million at December 31, 2021. This amount was primarily related to excess collateral we posted to counterparties. Collateral levels for upstream financial institution counterparties are monitored and adjusted as necessary. See Note 16 – Balance Sheet Offsetting and Repurchase Agreements for additional information regarding our credit exposure with upstream financial institution counterparties. At December 31, 2021 we had $110.3 million in cash collateral related to derivative contracts on deposit with other financial institution counterparties.

Balance Sheet Offsetting

Balance Sheet Offsetting	12 Months Ended
	Dec. 31, 2021
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, 2021 is presented in the following tables. Gross Amount Gross Amount Net Amount December 31, 2021 Financial assets: Derivatives: Loan/lease interest rate swaps and caps $ 4,446 $ — $ 4,446 Commodity swaps and options 18,864 — 18,864 Foreign currency forward contracts 29 — 29 Total derivatives 23,339 — 23,339 Resell agreements 7,903 — 7,903 Total $ 31,242 $ — $ 31,242 Financial liabilities: Derivatives: Loan/lease interest rate swaps $ 19,176 $ — $ 19,176 Commodity swaps and options 94,843 — 94,843 Total derivatives 114,019 — 114,019 Repurchase agreements 2,740,799 — 2,740,799 Total $ 2,854,818 $ — $ 2,854,818 Gross Amounts Not Offset Net Amount Financial Collateral Net December 31, 2021 Financial assets: Derivatives: Counterparty A $ 6 $ (6) $ — $ — Counterparty B 7,655 (7,655) — — Other counterparties 15,678 (15,678) — — Total derivatives 23,339 (23,339) — — Resell agreements 7,903 — (7,903) — Total $ 31,242 $ (23,339) $ (7,903) $ — Financial liabilities: Derivatives: Counterparty A $ 3,870 $ (6) $ (3,864) $ — Counterparty B 28,130 (7,655) (20,475) — Counterparty C 9 — (9) — Other counterparties 82,010 (15,678) (66,225) 107 Total derivatives 114,019 (23,339) (90,573) 107 Repurchase agreements 2,740,799 — (2,740,799) — Total $ 2,854,818 $ (23,339) $ (2,831,372) $ 107 Information about financial instruments that are eligible for offset in the consolidated balance sheet as of December 31, 2020 is presented in the following tables. Gross Amount Gross Amount Net Amount December 31, 2020 Financial assets: Derivatives: Loan/lease interest rate swaps and caps $ 1,241 $ — $ 1,241 Commodity swaps and options 9,870 — 9,870 Total derivatives 11,111 — 11,111 Resell agreements — — — Total $ 11,111 $ — $ 11,111 Financial liabilities: Derivatives: Loan/lease interest rate swaps $ 33,946 $ — $ 33,946 Commodity swaps and options 35,377 — 35,377 Foreign currency forward contracts — — — Total derivatives 69,323 — 69,323 Repurchase agreements 2,068,147 — 2,068,147 Total $ 2,137,470 $ — $ 2,137,470 Gross Amounts Not Offset Net Amount Financial Collateral Net December 31, 2020 Financial assets: Derivatives: Counterparty A $ 2 $ (2) $ — $ — Counterparty B 5,838 (5,838) — — Other counterparties 5,271 (5,271) — — Total derivatives 11,111 (11,111) — — Resell agreements — — — — Total $ 11,111 $ (11,111) $ — $ — Financial liabilities: Derivatives: Counterparty A $ 6,430 $ (2) $ (6,428) $ — Counterparty B 20,722 (5,838) (14,700) 184 Counterparty C 71 — (71) — Other counterparties 42,100 (5,271) (35,832) 997 Total derivatives 69,323 (11,111) (57,031) 1,181 Repurchase agreements 2,068,147 — (2,068,147) — Total $ 2,137,470 $ (11,111) $ (2,125,178) $ 1,181 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, 2021 and December 31, 2020 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, 2021 Repurchase agreements: U.S. Treasury $ 1,342,591 $ — $ — $ — $ 1,342,591 Residential mortgage-backed securities 1,398,208 — — — 1,398,208 Total borrowings $ 2,740,799 $ — $ — $ — $ 2,740,799 Gross amount of recognized liabilities for repurchase agreements $ 2,740,799 Amounts related to agreements not included in offsetting disclosures above $ — December 31, 2020 Repurchase agreements: U.S. Treasury $ 692,860 $ — $ — $ — $ 692,860 Residential mortgage-backed securities 1,375,287 — — — 1,375,287 Total borrowings $ 2,068,147 $ — $ — $ — $ 2,068,147 Gross amount of recognized liabilities for repurchase agreements $ 2,068,147 Amounts related to agreements not included in offsetting disclosures above $ —

Fair Value Measurements

Fair Value Measurements	12 Months Ended
	Dec. 31, 2021
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, 2021 and 2020, 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 2021 Securities available for sale: U.S. Treasury $ 2,179,433 $ — $ — $ 2,179,433 Residential mortgage-backed securities — 4,066,265 — 4,066,265 States and political subdivisions — 7,636,571 — 7,636,571 Other — 42,359 — 42,359 Trading account securities: U.S. Treasury 24,237 — — 24,237 States and political subdivisions — 925 — 925 Derivative assets: Interest rate swaps, caps and floors — 44,310 — 44,310 Commodity swaps and options — 114,757 — 114,757 Foreign currency forward contracts 33 — — 33 Derivative liabilities: Interest rate swaps, caps and floors — 25,261 — 25,261 Commodity swaps and options — 113,261 — 113,261 Foreign currency forward contracts 55 — — 55 2020 Securities available for sale: U.S. Treasury $ 1,119,633 $ — $ — $ 1,119,633 Residential mortgage-backed securities — 1,987,679 — 1,987,679 States and political subdivisions — 7,287,902 — 7,287,902 Other — 42,351 — 42,351 Trading account securities: U.S. Treasury 23,996 — — 23,996 States and political subdivisions — 460 — 460 Derivative assets: Interest rate swaps, caps and floors — 85,665 — 85,665 Commodity swaps and options — 45,535 456 45,991 Derivative liabilities: Interest rate swaps, caps and floors — 35,187 — 35,187 Commodity swaps and options — 45,099 — 45,099 Derivative assets, measured at fair value on a recurring basis using significant unobservable (Level 3) inputs during the reported periods consist of commodity swaps sold to loan customers. The significant unobservable (Level 3) inputs used in the fair value measurement of these commodity swaps sold to loan customers primarily relate to the probability of default and loss severity in the event of default. The probability of default is determined by the underlying risk grade of the loan (see Note 3 – Loans) underlying the commodity swap in that the probability of default increases as a loan’s risk grade deteriorates, while the loss severity is estimated through an analysis of the collateral supporting both the underlying loan and commodity swap. Generally, a change in the assumption used for the probability of default is accompanied by a directionally similar change in the assumption used for the loss severity. As of December 31, 2020, the weighted-average risk grade of loans underlying commodity swaps measured at fair value using significant unobservable (Level 3) inputs was 14.0. The weighted-average loss severity in the event of default on the commodity swaps was 10%. A reconciliation of the beginning and ending balances of derivative assets measured at fair value on a recurring basis using significant unobservable (Level 3) inputs is not presented as such amounts were 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. 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: 2021 2020 2019 Level 2 Carrying value before allocations $ 1,333 $ 1,559 $ 2,354 Specific (allocations) reversals of prior allocations 214 (450) (383) Fair value $ 1,547 $ 1,109 $ 1,971 Level 3 Carrying value before allocations $ 16,074 $ 34,302 $ 65,176 Specific (allocations) reversals of prior allocations (5,178) (11,151) (18,019) Fair value $ 10,896 $ 23,151 $ 47,157 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. Certain non-financial assets measured at fair value on a non-recurring basis include foreclosed assets (upon initial recognition or subsequent impairment), non-financial assets and non-financial liabilities measured at fair value in the second step of a goodwill impairment test, and intangible assets and other non-financial long-lived assets measured at fair value for impairment assessment. Non-financial assets measured at fair value on a non-recurring basis during the reported periods include certain foreclosed assets which, upon initial recognition, were remeasured and reported at fair value through a charge-off to the allowance for credit losses on loans 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. The fair value of a foreclosed asset is estimated using Level 2 inputs based on observable market data or Level 3 inputs based on customized discounting criteria. During the reported periods, all fair value measurements for foreclosed assets utilized Level 2 inputs. The following table presents foreclosed assets that were remeasured and reported at fair value: 2021 2020 2019 Foreclosed assets remeasured at initial recognition: Carrying value of foreclosed assets prior to remeasurement $ — $ — $ 1,348 Charge-offs recognized in the allowance for credit losses on loans — — (76) Fair value $ — $ — $ 1,272 Foreclosed assets remeasured subsequent to initial recognition: Carrying value of foreclosed assets prior to remeasurement $ 14 $ 328 $ — Write-downs included in other non-interest expense (14) (231) — Fair value $ — $ 97 $ — 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, 2021 December 31, 2020 Carrying Estimated Carrying Estimated Financial assets: Level 2 inputs: Cash and cash equivalents $ 16,583,000 $ 16,583,000 $ 10,288,853 $ 10,288,853 Securities held to maturity 1,749,179 1,809,143 1,945,673 2,052,896 Cash surrender value of life insurance policies 190,139 190,139 189,984 189,984 Accrued interest receivable 179,111 179,111 181,432 181,432 Level 3 inputs: Loans, net 16,087,731 16,079,454 17,218,132 17,390,683 Financial liabilities: Level 2 inputs: Deposits 42,695,696 41,343,426 35,015,761 35,018,185 Federal funds purchased 25,925 25,925 48,850 48,850 Repurchase agreements 2,740,799 2,740,799 2,068,147 2,068,147 Junior subordinated deferrable interest debentures 123,011 123,712 136,357 137,115 Subordinated notes 99,178 111,430 99,021 115,717 Accrued interest payable 3,026 3,026 8,127 8,127 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, 2021
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 $43.3 billion, $38.6 billion and $37.8 billion at December 31, 2021, 2020 and 2019. Banking Frost Non-Banks Consolidated 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 Banking Frost Non-Banks Consolidated 2020 Net interest income (expense) $ 981,441 $ 2,776 $ (8,216) $ 976,001 Credit loss expense 241,230 — — 241,230 Non-interest income 321,136 145,268 (950) 465,454 Non-interest expense 718,519 123,630 6,755 848,904 Income (loss) before income taxes 342,828 24,414 (15,921) 351,321 Income tax expense (benefit) 20,347 5,127 (5,304) 20,170 Net income (loss) 322,481 19,287 (10,617) 331,151 Preferred stock dividends — — 2,016 2,016 Redemption of preferred stock — — 5,514 5,514 Net income (loss) available to common shareholders $ 322,481 $ 19,287 $ (18,147) $ 323,621 Revenues from (expenses to) external customers $ 1,302,577 $ 148,044 $ (9,166) $ 1,441,455 Average assets (in millions) $ 37,892 $ 59 $ 10 $ 37,961 2019 Net interest income (expense) $ 1,010,368 $ 4,001 $ (10,364) $ 1,004,005 Credit loss expense 33,758 1 — 33,759 Non-interest income 218,447 145,905 (450) 363,902 Non-interest expense 703,121 124,622 6,936 834,679 Income (loss) before income taxes 491,936 25,283 (17,750) 499,469 Income tax expense (benefit) 55,520 5,308 (4,958) 55,870 Net income (loss) 436,416 19,975 (12,792) 443,599 Preferred stock dividends — — 8,063 8,063 Net income (loss) available to common shareholders $ 436,416 $ 19,975 $ (20,855) $ 435,536 Revenues from (expenses to) external customers $ 1,228,815 $ 149,906 $ (10,814) $ 1,367,907 Average assets (in millions) $ 32,019 $ 56 $ 11 $ 32,086

Condensed Financial Statements

Condensed Financial Statements of Parent Company	12 Months Ended
	Dec. 31, 2021
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, 2021 2020 Assets: Cash $ 471,875 $ 381,240 Resell agreements — — Total cash and cash equivalents 471,875 381,240 Investment in subsidiaries 4,222,288 4,155,619 Accrued interest receivable and other assets 2,228 2,164 Total assets $ 4,696,391 $ 4,539,023 Liabilities: Junior subordinated deferrable interest debentures, net of unamortized issuance costs $ 123,011 $ 136,357 Subordinated notes, net of unamortized issuance costs 99,178 99,021 Accrued interest payable and other liabilities 34,647 10,629 Total liabilities 256,836 246,007 Shareholders’ Equity 4,439,555 4,293,016 Total liabilities and shareholders’ equity $ 4,696,391 $ 4,539,023 Condensed Statements of Income Year Ended December 31, 2021 2020 2019 Income: Dividend income paid by Frost Bank $ 219,386 $ 298,884 $ 234,531 Dividend income paid by non-banks 473 736 1,822 Interest and other income 101 446 2,868 Total income 219,960 300,066 239,221 Expenses: Interest expense 7,141 8,216 10,363 Salaries and employee benefits 1,499 1,581 1,551 Other 5,867 6,833 7,033 Total expenses 14,507 16,630 18,947 Income before income taxes and equity in undistributed earnings of subsidiaries 205,453 283,436 220,274 Income tax benefit 4,899 5,406 5,135 Equity in undistributed earnings of subsidiaries 232,727 42,309 218,190 Net income 443,079 331,151 443,599 Preferred stock dividends 7,157 2,016 8,063 Redemption of preferred stock — 5,514 — Net income available to common shareholders $ 435,922 $ 323,621 $ 435,536 Condensed Statements of Cash Flows Year Ended December 31, 2021 2020 2019 Operating Activities: Net income $ 443,079 $ 331,151 $ 443,599 Adjustments to reconcile net income to net cash provided by operating activities: Equity in undistributed earnings of subsidiaries (232,727) (42,309) (218,190) Stock-based compensation 700 770 780 Net tax benefit from stock-based compensation 278 370 240 Net change in other assets and other liabilities 23,890 (8,937) 22,216 Net cash from operating activities 235,220 281,045 248,645 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) — — Redemption of Series A preferred stock — (150,000) — Proceeds from issuance of Series B preferred stock — 145,452 — Proceeds from stock option exercises 54,417 12,557 20,770 Proceeds from stock-based compensation activities of subsidiaries 12,053 13,148 15,166 Purchase of treasury stock (3,864) (15,785) (68,793) Treasury stock issued to 401(k) stock purchase plan 1,749 10,307 — Cash dividends paid on preferred stock (7,157) (2,016) (8,063) Cash dividends paid on common stock (188,786) (180,584) (177,006) Net cash from financing activities (144,991) (166,921) (217,926) Net change in cash and cash equivalents 90,635 114,124 30,719 Cash and cash equivalents at beginning of year 381,240 267,116 236,397 Cash and cash equivalents at end of year $ 471,875 $ 381,240 $ 267,116

Accounting Standards Updates

Accounting Standards Updates	12 Months Ended
	Dec. 31, 2021
Accounting Standards Update and Change in Accounting Principle [Abstract]
Accounting Standards Updates	Accounting Standards Updates ASU 2016-02, “Leases (Topic 842).” ASU 2016-02 among other things, requires lessees to recognize a lease liability, which is a lessee's obligation to make lease payments arising from a lease, measured on a discounted basis; and a right-of-use asset, which is an asset that represents the lessee’s right to use, or control the use of, a specified asset for the lease term. We adopted ASU 2016-02, along with several other subsequent codification updates related to lease accounting, as of January 1, 2019. See Note 1 - Summary of Significant Accounting Policies for additional information. ASU 2016-13, “Financial Instruments - Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments.” ASU 2016-13 requires the measurement of all expected credit losses for financial assets held at the reporting date based on historical experience, current conditions, and reasonable and supportable forecasts and requires enhanced disclosures related to the significant estimates and judgments used in estimating credit losses, as well as the credit quality and underwriting standards of an organization’s portfolio. We adopted ASU 2016-13, as subsequently updated for certain clarifications, targeted relief and codification improvements, as of January 1, 2020 and recognized a cumulative effect adjustment reducing retained earnings by $29.3 million. See Note 1 - Summary of Significant Accounting Policies for additional information. ASU 2017-04, “Intangibles - Goodwill and Other (Topic 350) - Simplifying the Test for Goodwill Impairment.” ASU 2017-04 eliminates Step 2 from the goodwill impairment test which required entities to compute the implied fair value of goodwill. Under ASU 2017-04, an entity should perform its annual, or interim, goodwill impairment test by comparing the fair value of a reporting unit with its carrying amount. An entity should recognize an impairment charge for the amount by which the carrying amount exceeds the reporting unit’s fair value; however, the loss recognized should not exceed the total amount of goodwill allocated to that reporting unit. ASU 2017-04 became effective for us on January 1, 2020 and did not have a significant impact on our financial statements. ASU 2017-08, “Receivables - Nonrefundable Fees and Other Costs (Subtopic 310-20) - Premium Amortization on Purchased Callable Debt Securities.” ASU 2017-08 shortens the amortization period for certain callable debt securities held at a premium to require such premiums to be amortized to the earliest call date unless applicable guidance related to certain pools of securities is applied to consider estimated prepayments. Under prior guidance, entities were generally required to amortize premiums on individual, non-pooled callable debt securities as a yield adjustment over the contractual life of the security. ASU 2017-08 does not change the accounting for callable debt securities held at a discount. We adopted ASU 2017-08 effective January 1, 2019 and recognized a cumulative effect adjustment reducing retained earnings by $14.7 million. See Note 1 - Summary of Significant Accounting Policies for additional information. ASU 2017-12, “Derivatives and Hedging (Topic 815) - Targeted Improvements to Accounting for Hedging Activities.” ASU 2017-12 amends the hedge accounting recognition and presentation requirements in ASC 815 to improve the transparency and understandability of information conveyed to financial statement users about an entity’s risk management activities to better align the entity’s financial reporting for hedging relationships with those risk management activities and to reduce the complexity of and simplify the application of hedge accounting. ASU 2017-12 became effective for us on January 1, 2019 and did not have a significant impact on our financial statements. ASU 2018-13, “Fair Value Measurement (Topic 820) - Disclosure Framework-Changes to the Disclosure Requirements for Fair Value Measurement.” ASU 2018-13 modifies the disclosure requirements on fair value measurements in Topic 820. The amendments in this update remove disclosures that no longer are considered cost beneficial, modify/clarify the specific requirements of certain disclosures, and add disclosure requirements identified as relevant. ASU 2018-13 became effective for us on January 1, 2020 and did not have a significant impact on our financial statements. ASU 2018-14, “Compensation - Retirement Benefits-Defined Benefit Plans-General (Subtopic 715-20).” ASU 2018-14 amends and modifies the disclosure requirements for employers that sponsor defined benefit pension or other post-retirement plans. The amendments in this update remove disclosures that no longer are considered cost beneficial, clarify the specific requirements of disclosures, and add disclosure requirements identified as relevant. ASU 2018-14 became effective for the year ended December 31, 2020 and did not have a significant impact on our financial statements. ASU 2018-15, “Intangibles - Goodwill and Other - Internal-Use Software (Subtopic 350-40) - Customer’s Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement That Is a Service Contract.” ASU 2018-15 clarifies certain aspects of ASU 2015-05, “Customer’s Accounting for Fees Paid in a Cloud Computing Arrangement,” which was issued in April 2015. Specifically, ASU 2018-15 aligns the requirements for capitalizing implementation costs incurred in a hosting arrangement that is a service contract with the requirements for capitalizing implementation costs incurred to develop or obtain internal-use software (and hosting arrangements that include an internal-use software license). ASU 2018-15 does not affect the accounting for the service element of a hosting arrangement that is a service contract. ASU 2018-15 became effective for us on January 1, 2020 and did not have a significant impact on our financial statements. ASU 2018-16, “Derivatives and Hedging (Topic 815) - Inclusion of the Secured Overnight Financing Rate (“SOFR”) Overnight Index Swap (“OIS”) Rate as a Benchmark Interest Rate for Hedge Accounting Purposes.” The amendments in this update permit use of the OIS rate based on SOFR as a U.S. benchmark interest rate for hedge accounting purposes under Topic 815 in addition to the interest rates on direct U.S. Treasury obligations, the LIBOR swap rate, the OIS rate based on the Fed Funds Effective Rate and the Securities Industry and Financial Markets Association (“SIFMA”) Municipal Swap Rate. ASU 2018-16 became effective for us on January 1, 2019 and did not have a significant impact on our financial statements. 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 2020-04, “Reference Rate Reform (Topic 848): Facilitation of the Effects of Reference Rate Reform on Financial Reporting.” ASU 2020-04 provides optional expedients and exceptions for accounting related to contracts, hedging relationships and other transactions affected by reference rate reform if certain criteria are met. ASU 2020-04 applies only to contracts, hedging relationships, and other transactions that reference LIBOR or another reference rate expected to be discontinued because of reference rate reform and do not apply to contract modifications made and hedging relationships entered into or evaluated after December 31, 2022, except for hedging relationships existing as of December 31, 2022, that an entity has elected certain optional expedients for and that are retained through the end of the hedging relationship. ASU 2020-04 was effective upon issuance and generally can be applied through December 31, 2022. The adoption of ASU 2020-04 did not significantly impact 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 2021-01, “Reference Rate Reform (Topic 848): Scope.” ASU 2021-01 clarifies that certain optional expedients and exceptions in ASC 848 for contract modifications and hedge accounting apply to derivatives that are affected by the discounting transition. ASU 2021-01 also amends the expedients and exceptions in ASC 848 to capture the incremental consequences of the scope clarification and to tailor the existing guidance to derivative instruments affected by the discounting transition. ASU 2021-01 was effective upon issuance and generally can be applied through December 31, 2022. The adoption of ASU 2021-01 did not significantly impact our financial statements.

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2021
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.
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, 2021 2020 2019 Cash paid for interest $ 29,003 $ 49,300 $ 124,781 Cash paid for income tax 39,852 44,140 45,352 Significant non-cash transactions: Transfer of securities from available for sale to held to maturity — — 377,812 Exchange of real estate 11,036 — — Unsettled securities transactions 27,032 57,783 — Loans foreclosed and transferred to other real estate owned and foreclosed assets 3,464 140 1,348 Loans to facilitate the sale of other real estate owned — — 847 Right-of-use lease assets obtained in exchange for lessee operating lease liabilities 12,854 18,284 319,286 Treasury stock issued to 401(k) stock purchase plan 1,749 10,307 —
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. As further discussed below, we adopted Accounting Standards Update (“ASU”) 2016-13, “Financial Instruments - Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments,” on January 1, 2020. Accounting Standards Codification (“ASC”) Topic 326 (“ASC 326”) replaced the previous “incurred loss” model for measuring credit losses, which encompassed allowances for current known and inherent losses within the portfolio, with an “expected loss” model, which encompasses allowances for losses 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 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. Prior to the adoption of ASU 2016-13, declines in the fair value of held-to-maturity and available-for-sale securities below their cost that were deemed to be other than temporary were reflected in earnings as realized losses. In estimating other-than-temporary impairment losses prior to January 1, 2020, management considered, among other things, (i) the length of time and the extent to which the fair value had been less than cost, (ii) the financial condition and near-term prospects of the issuer and (iii) the intent and our ability to retain our investment in the issuer for a period of time sufficient to allow for any anticipated recovery in fair value.
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 trouble debt restructuring will be executed with an individual borrower 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 and energy - non-revolving, (ii) commercial and industrial and energy - revolving, (iii) commercial real estate - owner occupied, (iv) commercial real estate - non-owner occupied, (v) commercial real estate - construction/land development, (vi) consumer real estate and (vii) consumer and other. 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
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 8 - 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.
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. In 2019, we adopted certain accounting standard updates related to accounting for leases as further discussed below. Under the new standards, 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 $3.4 million and $850 thousand at December 31, 2021 and 2020. 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. Write-downs of foreclosed assets totaled $14 thousand during 2021 and $231 thousand in 2020 while there were no write-downs during 2019. There were no significant concentrations of any properties, to which the aforementioned write-downs relate, in any single geographic region.
Goodwill	Goodwill. Goodwill represents the excess of the cost of businesses acquired over the fair value of the net assets acquired. Goodwill is assigned to reporting units and tested for impairment at least annually on October 1st, or on an interim basis if an event occurs or circumstances change that would more likely than not reduce the fair value of the reporting unit below its carrying value. See Note 5 - Goodwill and Other Intangible Assets.
Intangibles and Other Long Lived Assets	Intangibles and Other Long-Lived Assets . Intangible assets are acquired assets that lack physical substance but can be distinguished from goodwill because of contractual or other legal rights or because the asset is capable of being sold or exchanged either on its own or in combination with a related contract, asset, or liability. Our intangible assets relate to core deposits, non-compete agreements and customer relationships. Intangible assets with definite useful lives are amortized on an accelerated basis over their estimated life. Intangible assets with indefinite useful lives are not amortized until their lives are determined to be definite. Intangible assets, premises and equipment and other long-lived assets are tested for impairment whenever events or changes in circumstances indicate the carrying amount of the assets may not be recoverable from future undiscounted cash flows. If impaired, the assets are recorded at fair value. See Note 5 - Goodwill and Other Intangible Assets.
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 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 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 2021 base-year amount. Adjusted net revenue for the three-year performance period is calculated as the sum of taxable-equivalent net interest income (excluding the effects of PPP lending) and non-interest income, reduced by non-interest expense (excluding the effects of PPP lending) and net charge-offs. The 2021 base-year adjusted net revenue amount of approximately $426.6 million was calculated as the sum of taxable-equivalent net interest income (excluding the effects of PPP lending) and non-interest income, reduced by non-interest expense (excluding the effects of PPP lending) and the product of average total loans (excluding PPP loans) and 0.30%. The ultimate number of shares issuable under each performance award is the product of the award target and the award payout percentage for the given level of achievement. The level of achievement is measured as the amount by which adjusted net revenue, averaged over a three-year performance period, exceeds the 2021 base-year amount, stated as an average growth percentage. The award payout percentages by level of achievement are as follows: (i) less than 13% average growth pays out at 0% of target, (ii) 13% average growth pays out at 50% of target, (iii) 19% average growth pays out at 100% of target and (iv) 25% average growth or more pays out at 150% of target. Achievement between the aforementioned average growth percentages will result in an award payout percentage determined based on straight-line interpolation between the percentages. 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. The ultimate number of shares issuable under each performance award is the product of the award target and the award payout percentage for the given level of achievement. The level of achievement is measured as the percentile rank of relative return on assets among the peer group. The award payout percentages by level of achievement are as follows: (i) less than 25th percentile pays out at 0% of target, (ii) 25th percentile pays out at 50% of target, (iii) 50th percentile pays out at 100% of target and (iv) 75th percentile or more pays out at 150% of target. Achievement between the aforementioned percentiles will result in an award payout percentage determined based on straight-line interpolation between the percentiles. 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. Valuation of Stock-Based Compensation . For the purposes of recognizing stock-based compensation expense, the fair value of non-vested stock awards/stock units and 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 $0.75, $0.72 and $0.71 in 2021, 2020, and 2019, respectively, discounted at a weighted-average risk-free rate of 0.77%, 0.19% and 1.65% in 2021, 2020, and 2019, 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 13 - Income Taxes.
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 10 - 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 14 - 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 17 - 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 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. Certain non-financial assets measured at fair value on a non-recurring basis include foreclosed assets (upon initial recognition or subsequent impairment), non-financial assets and non-financial liabilities measured at fair value in the second step of a goodwill impairment test, and intangible assets and other non-financial long-lived assets measured at fair value for impairment assessment. Non-financial assets measured at fair value on a non-recurring basis during the reported periods include certain foreclosed assets which, upon initial recognition, were remeasured and reported at fair value through a charge-off to the allowance for credit losses on loans 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. The fair value of a foreclosed asset is estimated using Level 2 inputs based on observable market data or Level 3 inputs based on customized discounting criteria. During the reported periods, all fair value measurements for foreclosed assets utilized Level 2 inputs. 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.
Reclassification, Comparability Adjustment	Certain items in prior financial statements have been reclassified to conform to the current presentation.
Accounting Changes, Reclassifications and Restatement	Accounting Changes, Reclassifications and Restatements. Certain items in prior financial statements have been reclassified to conform to the current presentation. As discussed above, on January 1, 2020 we adopted the provisions of ASC 326 using the modified retrospective method for all financial assets measured at amortized cost and off-balance-sheet credit exposures. Upon adoption, we recognized an after-tax cumulative effect reduction to retained earnings totaling $29.3 million, as detailed in the table below. Operating results for periods after January 1, 2020 are presented in accordance with ASC 326 while prior period amounts continue to be reported in accordance with previously applicable standards and the accounting policies as described above. The following table details the impact of the adoption of ASC 326 on the allowance for credit losses as of January 1, 2020. January 1, 2020 Pre-Adoption Allowance Impact of Adoption Post-Adoption Allowance Cumulative Effect on Retained Earnings Securities held to maturity: U.S. Treasury $ — $ — $ — $ — Residential mortgage-backed securities — — — — States and political subdivisions — 215 215 (170) Other — — — — Total $ — $ 215 $ 215 $ (170) Loans: Commercial and industrial $ 51,593 $ 21,263 $ 72,856 $ (16,798) Energy 37,382 (10,453) 26,929 8,258 Commercial real estate 31,037 (13,519) 17,518 10,680 Consumer real estate 4,113 2,392 6,505 (1,890) Consumer and other 8,042 (2,248) 5,794 1,776 Total $ 132,167 $ (2,565) $ 129,602 $ 2,026 Off-balance-sheet credit exposures $ 500 $ 39,377 $ 39,877 $ (31,108) On January 1, 2019, we adopted certain accounting standard updates related to accounting for leases, primarily ASU 2016-02 “Leases (Topic 842)” and subsequent updates. Among other things, these updates require lessees to recognize a lease liability, measured on a discounted basis, related to the lessee's obligation to make lease payments arising under a lease contract; and a right-of-use asset related to the lessee’s right to use, or control the use of, a specified asset for the lease term. The updates did not significantly change lease accounting requirements applicable to lessors and did not significantly impact our financial statements in relation to contracts whereby we act as a lessor. We adopted the updates using a modified-retrospective transition approach and recognized right-of-use lease assets and related lease liabilities totaling $170.5 million and $174.4 million, respectively, as of January 1, 2019. We elected to apply certain practical adoption expedients provided under the updates whereby we did not reassess (i) whether any expired or existing contracts are or contain leases, (ii) the lease classification for any expired or existing leases and (iii) initial direct costs for any existing leases. We did not elect to apply the recognition requirements of the updates to short-term leases. See Note 4 - Premises and Equipment and Lease Commitments.

Receivables, Loans, Notes Recei

Receivables, Loans, Notes Receivable, and Others (Policies)	12 Months Ended
	Dec. 31, 2021
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 trouble debt restructuring will be executed with an individual borrower 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 and energy - non-revolving, (ii) commercial and industrial and energy - revolving, (iii) commercial real estate - owner occupied, (iv) commercial real estate - non-owner occupied, (v) commercial real estate - construction/land development, (vi) consumer real estate and (vii) consumer and other. 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

Fair Value Measures and Disclos

Fair Value Measures and Disclosures (Policies)	12 Months Ended
	Dec. 31, 2021
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 8 - 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.

Earnings Per Share (Policies)

Earnings Per Share (Policies)	12 Months Ended
	Dec. 31, 2021
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 10 - 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, 2021
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 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 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 2021 base-year amount. Adjusted net revenue for the three-year performance period is calculated as the sum of taxable-equivalent net interest income (excluding the effects of PPP lending) and non-interest income, reduced by non-interest expense (excluding the effects of PPP lending) and net charge-offs. The 2021 base-year adjusted net revenue amount of approximately $426.6 million was calculated as the sum of taxable-equivalent net interest income (excluding the effects of PPP lending) and non-interest income, reduced by non-interest expense (excluding the effects of PPP lending) and the product of average total loans (excluding PPP loans) and 0.30%. The ultimate number of shares issuable under each performance award is the product of the award target and the award payout percentage for the given level of achievement. The level of achievement is measured as the amount by which adjusted net revenue, averaged over a three-year performance period, exceeds the 2021 base-year amount, stated as an average growth percentage. The award payout percentages by level of achievement are as follows: (i) less than 13% average growth pays out at 0% of target, (ii) 13% average growth pays out at 50% of target, (iii) 19% average growth pays out at 100% of target and (iv) 25% average growth or more pays out at 150% of target. Achievement between the aforementioned average growth percentages will result in an award payout percentage determined based on straight-line interpolation between the percentages. 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. The ultimate number of shares issuable under each performance award is the product of the award target and the award payout percentage for the given level of achievement. The level of achievement is measured as the percentile rank of relative return on assets among the peer group. The award payout percentages by level of achievement are as follows: (i) less than 25th percentile pays out at 0% of target, (ii) 25th percentile pays out at 50% of target, (iii) 50th percentile pays out at 100% of target and (iv) 75th percentile or more pays out at 150% of target. Achievement between the aforementioned percentiles will result in an award payout percentage determined based on straight-line interpolation between the percentiles. 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. Valuation of Stock-Based Compensation . For the purposes of recognizing stock-based compensation expense, the fair value of non-vested stock awards/stock units and 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 $0.75, $0.72 and $0.71 in 2021, 2020, and 2019, respectively, discounted at a weighted-average risk-free rate of 0.77%, 0.19% and 1.65% in 2021, 2020, and 2019, respectively.

Fair Value Measures and Discl_2

Fair Value Measures and Disclosures (Policies)	12 Months Ended
	Dec. 31, 2021
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 17 - 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 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. Certain non-financial assets measured at fair value on a non-recurring basis include foreclosed assets (upon initial recognition or subsequent impairment), non-financial assets and non-financial liabilities measured at fair value in the second step of a goodwill impairment test, and intangible assets and other non-financial long-lived assets measured at fair value for impairment assessment. Non-financial assets measured at fair value on a non-recurring basis during the reported periods include certain foreclosed assets which, upon initial recognition, were remeasured and reported at fair value through a charge-off to the allowance for credit losses on loans 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. The fair value of a foreclosed asset is estimated using Level 2 inputs based on observable market data or Level 3 inputs based on customized discounting criteria. During the reported periods, all fair value measurements for foreclosed assets utilized Level 2 inputs. 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, 2021
Accounting Policies [Abstract]
Additional Cash Flow Information	Additional cash flow information was as follows: Year Ended December 31, 2021 2020 2019 Cash paid for interest $ 29,003 $ 49,300 $ 124,781 Cash paid for income tax 39,852 44,140 45,352 Significant non-cash transactions: Transfer of securities from available for sale to held to maturity — — 377,812 Exchange of real estate 11,036 — — Unsettled securities transactions 27,032 57,783 — Loans foreclosed and transferred to other real estate owned and foreclosed assets 3,464 140 1,348 Loans to facilitate the sale of other real estate owned — — 847 Right-of-use lease assets obtained in exchange for lessee operating lease liabilities 12,854 18,284 319,286 Treasury stock issued to 401(k) stock purchase plan 1,749 10,307 —
Accounting Standards Update and Change in Accounting Principle	The following table details the impact of the adoption of ASC 326 on the allowance for credit losses as of January 1, 2020. January 1, 2020 Pre-Adoption Allowance Impact of Adoption Post-Adoption Allowance Cumulative Effect on Retained Earnings Securities held to maturity: U.S. Treasury $ — $ — $ — $ — Residential mortgage-backed securities — — — — States and political subdivisions — 215 215 (170) Other — — — — Total $ — $ 215 $ 215 $ (170) Loans: Commercial and industrial $ 51,593 $ 21,263 $ 72,856 $ (16,798) Energy 37,382 (10,453) 26,929 8,258 Commercial real estate 31,037 (13,519) 17,518 10,680 Consumer real estate 4,113 2,392 6,505 (1,890) Consumer and other 8,042 (2,248) 5,794 1,776 Total $ 132,167 $ (2,565) $ 129,602 $ 2,026 Off-balance-sheet credit exposures $ 500 $ 39,377 $ 39,877 $ (31,108)

Securities (Tables)

Securities (Tables)	12 Months Ended
	Dec. 31, 2021
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, 2021 and 2020 is presented below. Amortized Gross Gross Estimated Allowance Net December 31, 2021 Residential mortgage-backed securities $ 527,264 $ 18,766 $ — $ 546,030 $ — $ 527,264 States and political subdivisions 1,220,573 41,141 101 1,261,613 (158) 1,220,415 Other 1,500 — — 1,500 — 1,500 Total $ 1,749,337 $ 59,907 $ 101 $ 1,809,143 $ (158) $ 1,749,179 December 31, 2020 Residential mortgage-backed securities $ 528,784 $ 41,742 $ — $ 570,526 $ — $ 528,784 States and political subdivisions 1,415,549 65,321 — 1,480,870 (160) 1,415,389 Other 1,500 — — 1,500 — 1,500 Total $ 1,945,833 $ 107,063 $ — $ 2,052,896 $ (160) $ 1,945,673
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, 2021: States and Political Subdivisions Not Guaranteed or Pre-Refunded Guaranteed by the Texas PSF Pre-Refunded Total Other Aaa/AAA $ 92,379 $ 460,648 $ 563,251 $ 1,116,278 $ — Aa/AA 104,295 — — 104,295 — Not rated — — — — 1,500 Total $ 196,674 $ 460,648 $ 563,251 $ 1,220,573 $ 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. 2021 2020 Beginning balance $ 160 $ — Impact of adopting ASC 326 — 215 Credit loss expense (benefit) (2) (55) Ending balance $ 158 $ 160
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, 2021 and 2020 is presented below. Amortized Gross Gross Allowance Estimated December 31, 2021 U.S. Treasury $ 2,165,702 $ 23,333 $ 9,602 $ — $ 2,179,433 Residential mortgage-backed securities 4,059,692 31,662 25,089 — 4,066,265 States and political subdivisions 7,178,135 463,810 5,374 — 7,636,571 Other 42,359 — — — 42,359 Total $ 13,445,888 $ 518,805 $ 40,065 $ — $ 13,924,628 December 31, 2020 U.S. Treasury $ 1,084,542 $ 35,091 $ — $ — $ 1,119,633 Residential mortgage-backed securities 1,916,581 71,102 4 — 1,987,679 States and political subdivisions 6,683,927 603,975 — — 7,287,902 Other 42,351 — — — 42,351 Total $ 9,727,401 $ 710,168 $ 4 $ — $ 10,437,565
Year End Securities with Unrealized Losses, Segregated by Length of Impairment	The table below summarizes, as of December 31, 2021, 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 $ 684,242 $ 9,602 $ — $ — $ 684,242 $ 9,602 Residential mortgage-backed securities 2,219,261 23,625 45,963 1,464 2,265,224 25,089 States and political subdivisions 364,056 5,074 5,675 300 369,731 5,374 Total $ 3,267,559 $ 38,301 $ 51,638 $ 1,764 $ 3,319,197 $ 40,065
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, 2021. 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 $ 37 $ — $ 515,100 $ 12,127 $ 527,264 States and political subdivisions 464,112 180,373 73,808 502,280 1,220,573 Other 1,500 — — — 1,500 Total $ 465,649 $ 180,373 $ 588,908 $ 514,407 $ 1,749,337 Estimated Fair Value Residential mortgage-backed securities $ 37 $ — $ 533,454 $ 12,539 $ 546,030 States and political subdivisions 468,685 185,458 74,729 532,741 1,261,613 Other 1,500 — — — 1,500 Total $ 470,222 $ 185,458 $ 608,183 $ 545,280 $ 1,809,143 Available For Sale Amortized Cost U. S. Treasury $ — $ 1,030,591 $ 943,417 $ 191,694 $ 2,165,702 Residential mortgage-backed securities 63 15,278 19,175 4,025,176 4,059,692 States and political subdivisions 86,485 1,611,040 808,323 4,672,287 7,178,135 Other — — — — 42,359 Total $ 86,548 $ 2,656,909 $ 1,770,915 $ 8,889,157 $ 13,445,888 Estimated Fair Value U. S. Treasury $ — $ 1,038,734 $ 942,113 $ 198,586 $ 2,179,433 Residential mortgage-backed securities 64 15,954 19,624 4,030,623 4,066,265 States and political subdivisions 87,493 1,715,065 858,485 4,975,528 7,636,571 Other — — — — 42,359 Total $ 87,557 $ 2,769,753 $ 1,820,222 $ 9,204,737 $ 13,924,628
Schedule of Realized Gain (Loss)	Sales of securities available for sale were as follows: 2021 2020 2019 Proceeds from sales $ 1,999,891 $ 1,162,352 $ 18,660,147 Gross realized gains 69 108,989 930 Gross realized losses — — (637) Tax benefit (expense) related to securities gains/losses (14) (22,888) (62)
Investment Income	Premium amortization and discount accretion included in interest income on securities was as follows: 2021 2020 2019 Premium amortization $ (121,994) $ (126,210) $ (120,785) Discount accretion 2,752 2,425 5,227 Net (premium amortization) discount accretion $ (119,242) $ (123,785) $ (115,558)
Year End Trading Account Securities, at Estimated Fair Value	Year-end trading account securities, at estimated fair value, were as follows: 2021 2020 U.S. Treasury $ 24,237 $ 23,996 States and political subdivisions 925 460 Total $ 25,162 $ 24,456
Net Gains and Losses on Trading Account Securities	Net gains and losses on trading account securities were as follows: 2021 2020 2019 Net gain on sales transactions $ 1,014 $ 1,102 $ 2,173 Net mark-to-market gains (losses) (75) 85 (176) Net gain on trading account securities $ 939 $ 1,187 $ 1,997

Loans (Tables)

Loans (Tables)	12 Months Ended
	Dec. 31, 2021
Receivables [Abstract]
Loans	Year-end loans, including leases net of unearned discounts, consisted of the following: 2021 2020 Commercial and industrial $ 5,364,954 $ 4,955,341 Energy: Production 878,436 976,473 Service 105,901 116,825 Other 93,455 141,900 Total energy 1,077,792 1,235,198 Paycheck Protection Program 428,882 2,433,849 Commercial real estate: Commercial mortgages 5,867,062 5,478,806 Construction 1,304,271 1,223,814 Land 405,277 317,847 Total commercial real estate 7,576,610 7,020,467 Consumer real estate: Home equity loans 324,157 329,390 Home equity lines of credit 519,098 452,854 Other 567,535 548,530 Total consumer real estate 1,410,790 1,330,774 Total real estate 8,987,400 8,351,241 Consumer and other 477,369 505,680 Total loans $ 16,336,397 $ 17,481,309
Activities in Related Party Loans	Activity in related party loans during 2021 is presented in the following table. Other changes were primarily related to changes in related-party status. Balance outstanding at December 31, 2020 $ 353,105 Principal additions 262,761 Principal payments (196,634) Other changes (68,694) Balance outstanding at December 31, 2021 $ 350,538
Non-Accrual Loans, Segregated by Class of Loans	Year-end non-accrual loans, segregated by class of loans, were as follows: December 31, 2021 December 31, 2020 Total Non-Accrual Non-Accrual with No Credit Loss Allowance Total Non-Accrual Non-Accrual with No Credit Loss Allowance Commercial and industrial $ 22,582 $ 4,701 $ 19,849 $ 4,479 Energy 14,433 8,533 23,168 639 Paycheck Protection Program — — — — Commercial real estate: Buildings, land and other 15,297 13,817 15,737 14,116 Construction 948 — 1,684 1,684 Consumer real estate 440 138 993 993 Consumer and other 13 13 18 — Total $ 53,713 $ 27,202 $ 61,449 $ 21,911
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, 2021 and December 31, 2020 by class and year of origination. December 31, 2021 2021 2020 2019 2018 2017 Prior Revolving Loans Revolving Loans Converted to Term Total Commercial and industrial $ 636 $ 3,856 $ 5,047 $ 1,820 $ 765 $ 353 $ 4,635 $ 5,470 $ 22,582 Energy — — 5,358 1,325 — — 6,931 819 14,433 Paycheck Protection Program — — — — — — — — — Commercial real estate: Buildings, land and other 6,038 307 3,446 814 2,030 2,662 — — 15,297 Construction — 948 — — — — — — 948 Consumer real estate — — — — — 408 — 32 440 Consumer and other 13 — — — — — — — 13 Total $ 6,687 $ 5,111 $ 13,851 $ 3,959 $ 2,795 $ 3,423 $ 11,566 $ 6,321 $ 53,713 December 31, 2020 2020 2019 2018 2017 2016 Prior Revolving Loans Revolving Loans Converted to Term Total Commercial and industrial $ 9,479 $ 3,351 $ 1,846 $ 1,489 $ 105 $ 29 $ 839 $ 2,711 $ 19,849 Energy 2,421 6,772 2,144 — — 359 11,193 279 23,168 Paycheck Protection Program — — — — — — — — — Commercial real estate: Buildings, land and other 2,914 5,031 999 2,019 1,933 2,736 105 — 15,737 Construction 1,684 — — — — — — — 1,684 Consumer real estate — — — 211 — 408 259 115 993 Consumer and other — — — — — — 18 — 18 Total $ 16,498 $ 15,154 $ 4,989 $ 3,719 $ 2,038 $ 3,532 $ 12,414 $ 3,105 $ 61,449
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, 2021 is presented in the following table. Despite their past due status, Paycheck Protection Plan loans are fully guaranteed by the SBA. Loans Loans Total Past Current Total Loans Accruing Commercial and industrial $ 34,096 $ 12,364 $ 46,460 $ 5,318,494 $ 5,364,954 $ 7,802 Energy 1,451 7,867 9,318 1,068,474 1,077,792 215 Paycheck Protection Program 4,979 18,766 23,745 405,137 428,882 18,766 Commercial real estate: Buildings, land and other 37,899 14,136 52,035 6,220,304 6,272,339 8,687 Construction 188 — 188 1,304,083 1,304,271 — Consumer real estate 4,877 2,513 7,390 1,403,400 1,410,790 2,177 Consumer and other 4,185 1,076 5,261 472,108 477,369 1,076 Total $ 87,675 $ 56,722 $ 144,397 $ 16,192,000 $ 16,336,397 $ 38,723
Troubled Debt Restructurings	Troubled debt restructurings that occurred during 2021, 2020 and 2019 are set forth in the following table. 2021 2020 2019 Balance at Balance at Balance at Balance at Balance at Balance at Commercial and industrial $ 1,312 $ 1,162 $ 3,661 $ 192 $ 3,845 $ 2,161 Energy 3,817 721 2,432 2,421 — — Commercial real estate: Buildings, land and other 1,888 1,862 9,310 4,922 9,457 9,393 Construction — — 1,017 1,017 — — Consumer real estate — — — — 124 120 Consumer and other — — 1,104 — — — $ 7,017 $ 3,745 $ 17,524 $ 8,552 $ 13,426 $ 11,674
Restructured Loans Past Due in Excess of 90 Days on Financing Receivables	Additional information related to restructured loans was as follows: 2021 2020 2019 Restructured loans past due in excess of 90 days at period-end: Number of loans 2 1 4 Dollar amount of loans $ 1,027 $ 2,008 $ 3,340 Restructured loans on non-accrual status at period end 3,439 8,552 5,576 Charge-offs of restructured loans: Recognized in connection with restructuring — 337 — Recognized on previously restructured loans 4,278 3,894 1,500
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, 2021 and 2020. Paycheck Protection Program (“PPP”) loans are excluded as such loans are fully guaranteed by the Small Business Administration (“SBA”). December 31, 2021 2021 2020 2019 2018 2017 Prior Revolving Loans Revolving Loans Converted to Term Total Commercial and industrial Risk grades 1-8 $ 1,567,883 $ 657,529 $ 350,563 $ 179,209 $ 146,064 $ 131,201 $ 1,987,061 $ 44,337 $ 5,063,847 Risk grade 9 32,866 21,094 24,683 26,327 612 11,419 65,131 5,738 187,870 Risk grade 10 27,961 6,273 4,047 4,357 1,021 98 14,091 1,289 59,137 Risk grade 11 1,178 4,572 8,068 2,450 2,460 221 4,714 7,855 31,518 Risk grade 12 456 2,495 3,828 1,756 347 353 613 2,687 12,535 Risk grade 13 180 1,361 1,219 64 418 — 4,022 2,783 10,047 $ 1,630,524 $ 693,324 $ 392,408 $ 214,163 $ 150,922 $ 143,292 $ 2,075,632 $ 64,689 $ 5,364,954 W/A risk grade 5.91 6.30 6.89 7.06 5.91 5.80 6.21 8.04 6.22 Energy Risk grades 1-8 $ 445,489 $ 8,075 $ 9,259 $ 6,441 $ 3,110 $ 4,368 $ 464,454 $ 67,174 $ 1,008,370 Risk grade 9 19,274 611 1,775 187 — 724 11,635 2,416 36,622 Risk grade 10 — 101 631 511 — — — 530 1,773 Risk grade 11 10,260 752 3,968 1,016 — 546 — 52 16,594 Risk grade 12 — — 3,888 246 — — 4,000 819 8,953 Risk grade 13 — — 1,470 1,079 — — 2,931 — 5,480 $ 475,023 $ 9,539 $ 20,991 $ 9,480 $ 3,110 $ 5,638 $ 483,020 $ 70,991 $ 1,077,792 W/A risk grade 6.21 7.81 9.34 8.60 7.12 7.63 5.61 6.46 6.06 Commercial real estate: Buildings, land, other Risk grades 1-8 $ 1,707,550 $ 1,096,274 $ 874,130 $ 533,362 $ 492,492 $ 713,268 $ 52,150 $ 105,696 $ 5,574,922 Risk grade 9 16,302 145,340 52,427 43,806 27,188 27,767 4,445 4,258 321,533 Risk grade 10 28,209 13,813 69,643 46,250 64,950 46,582 — — 269,447 Risk grade 11 3,455 1,321 8,720 7,788 26,107 34,970 3,000 5,779 91,140 Risk grade 12 5,838 307 3,446 814 2,030 2,662 — — 15,097 Risk grade 13 200 — — — — — — — 200 $ 1,761,554 $ 1,257,055 $ 1,008,366 $ 632,020 $ 612,767 $ 825,249 $ 59,595 $ 115,733 $ 6,272,339 W/A risk grade 7.19 7.18 7.35 7.39 7.34 7.01 7.06 7.02 7.22 Construction Risk grades 1-8 $ 657,471 $ 262,176 $ 178,226 $ 2,339 $ 38 $ 1,930 $ 160,020 $ — $ 1,262,200 Risk grade 9 35,721 4,956 — — 446 — — — 41,123 Risk grade 10 — — — — — — — — — Risk grade 11 — — — — — — — — — Risk grade 12 — 748 — — — — — — 748 Risk grade 13 — 200 — — — — — — 200 $ 693,192 $ 268,080 $ 178,226 $ 2,339 $ 484 $ 1,930 $ 160,020 $ — $ 1,304,271 W/A risk grade 7.17 6.56 7.60 7.51 8.92 6.73 6.79 — 7.06 Total commercial real estate $ 2,454,746 $ 1,525,135 $ 1,186,592 $ 634,359 $ 613,251 $ 827,179 $ 219,615 $ 115,733 $ 7,576,610 W/A risk grade 7.18 7.07 7.39 7.39 7.34 7.00 6.86 7.02 7.19 December 31, 2020 2020 2019 2018 2017 2016 Prior Revolving Loans Revolving Loans Converted to Term Total Commercial and industrial Risk grades 1-8 $ 1,300,844 $ 552,885 $ 290,088 $ 226,232 $ 107,063 $ 113,458 $ 1,852,341 $ 63,210 $ 4,506,121 Risk grade 9 50,785 37,865 33,961 20,851 12,348 5,510 85,756 9,122 256,198 Risk grade 10 31,333 7,361 11,379 6,749 710 113 65,180 3,152 125,977 Risk grade 11 4,700 7,002 6,551 3,416 1,426 140 15,005 8,956 47,196 Risk grade 12 6,899 2,399 1,195 1,005 105 29 480 2,416 14,528 Risk grade 13 2,580 952 651 484 — — 359 295 5,321 $ 1,397,141 $ 608,464 $ 343,825 $ 258,737 $ 121,652 $ 119,250 $ 2,019,121 $ 87,151 $ 4,955,341 W/A risk grade 6.19 6.88 7.22 6.39 6.32 5.84 6.38 7.51 6.45 Energy Risk grades 1-8 $ 403,156 $ 18,911 $ 9,759 $ 8,083 $ 1,415 $ 4,326 $ 494,946 $ 27,548 $ 968,144 Risk grade 9 105,772 2,272 1,743 — — — 18,194 5,566 133,547 Risk grade 10 703 4,049 1,339 — 759 — 37,637 1,940 46,427 Risk grade 11 12,218 16,849 1,325 — — 661 30,124 2,735 63,912 Risk grade 12 1,101 4,580 654 — — 359 6,768 279 13,741 Risk grade 13 1,320 2,192 1,490 — — — 4,425 — 9,427 $ 524,270 $ 48,853 $ 16,310 $ 8,083 $ 2,174 $ 5,346 $ 592,094 $ 38,068 $ 1,235,198 W/A risk grade 6.86 9.57 8.68 7.40 7.85 8.06 6.45 8.20 6.85 Commercial real estate: Buildings, land, other Risk grades 1-8 $ 1,544,558 $ 947,102 $ 749,879 $ 605,152 $ 432,941 $ 661,301 $ 56,600 $ 50,340 $ 5,047,873 Risk grade 9 45,527 81,224 75,893 45,485 26,745 37,728 10,521 2,104 325,227 Risk grade 10 14,183 36,414 45,014 71,814 25,343 60,225 200 5,261 258,454 Risk grade 11 22,633 16,302 11,916 39,727 8,655 42,904 6,977 248 149,362 Risk grade 12 2,714 5,031 999 2,019 1,683 2,736 42 — 15,224 Risk grade 13 200 — — — 250 — 63 — 513 $ 1,629,815 $ 1,086,073 $ 883,701 $ 764,197 $ 495,617 $ 804,894 $ 74,403 $ 57,953 $ 5,796,653 W/A risk grade 7.13 7.36 7.54 7.55 7.54 7.20 7.54 7.12 7.34 Construction Risk grades 1-8 $ 374,661 $ 436,077 $ 168,517 $ 67 $ 1,144 $ 1,758 $ 127,801 $ — $ 1,110,025 Risk grade 9 37,430 16,567 — 2,848 — — 14,311 1,131 72,287 Risk grade 10 5,846 — 27,653 — — — 5,463 — 38,962 Risk grade 11 856 — — — — — — — 856 Risk grade 12 1,684 — — — — — — — 1,684 Risk grade 13 — — — — — — — — — $ 420,477 $ 452,644 $ 196,170 $ 2,915 $ 1,144 $ 1,758 $ 147,575 $ 1,131 $ 1,223,814 W/A risk grade 6.82 7.18 8.08 8.95 7.30 6.44 7.29 9.00 7.22 Total commercial real estate $ 2,050,292 $ 1,538,717 $ 1,079,871 $ 767,112 $ 496,761 $ 806,652 $ 221,978 $ 59,084 $ 7,020,467 W/A risk grade 7.06 7.31 7.64 7.56 7.54 7.20 7.37 7.15 7.32
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, 2021 and December 31, 2020 was as follows: December 31, 2021 2021 2020 2019 2018 2017 Prior Revolving Loans Revolving Loans Converted to Term Total Consumer real estate: Past due 30-89 days $ 280 $ 204 $ 406 $ 489 $ 296 $ 1,344 $ 126 $ 1,732 $ 4,877 Past due 90 or more days — — — 154 355 828 991 185 2,513 Total past due 280 204 406 643 651 2,172 1,117 1,917 7,390 Current loans 319,042 251,160 95,900 55,893 48,841 116,423 505,333 10,808 1,403,400 Total $ 319,322 $ 251,364 $ 96,306 $ 56,536 $ 49,492 $ 118,595 $ 506,450 $ 12,725 $ 1,410,790 Consumer and other: Past due 30-89 days $ 1,600 $ 91 $ 120 $ 38 $ 51 $ 17 $ 325 $ 1,943 $ 4,185 Past due 90 or more days 548 — 45 — — — 34 449 1,076 Total past due 2,148 91 165 38 51 17 359 2,392 5,261 Current loans 46,708 17,843 6,215 2,684 1,708 1,158 371,866 23,926 472,108 Total $ 48,856 $ 17,934 $ 6,380 $ 2,722 $ 1,759 $ 1,175 $ 372,225 $ 26,318 $ 477,369 December 31, 2020 2020 2019 2018 2017 2016 Prior Revolving Loans Revolving Loans Converted to Term Total Consumer real estate: Past due 30-89 days $ 225 $ 1,038 $ 1,556 $ 553 $ 628 $ 2,907 $ 652 $ 531 $ 8,090 Past due 90 or more days 15 139 109 706 25 1,287 615 151 3,047 Total past due 240 1,177 1,665 1,259 653 4,194 1,267 682 11,137 Current loans 336,441 166,323 94,374 80,625 66,241 124,590 434,939 16,104 1,319,637 Total $ 336,681 $ 167,500 $ 96,039 $ 81,884 $ 66,894 $ 128,784 $ 436,206 $ 16,786 $ 1,330,774 Consumer and other: Past due 30-89 days $ 1,750 $ 300 $ 453 $ 52 $ 17 $ — $ 2,238 $ 727 $ 5,537 Past due 90 or more days 71 10 118 — — — 1,031 21 1,251 Total past due 1,821 310 571 52 17 — 3,269 748 6,788 Current loans 45,286 27,813 5,397 2,799 1,705 572 386,791 28,529 498,892 Total $ 47,107 $ 28,123 $ 5,968 $ 2,851 $ 1,722 $ 572 $ 390,060 $ 29,277 $ 505,680
Financing Receivable Revolving Loans Converted to Term	Revolving loans that converted to term during 2021 and 2020 were as follows: 2021 2020 Commercial and industrial $ 40,099 $ 47,562 Energy 54,996 33,150 Commercial real estate: Buildings, land and other 68,337 10,505 Construction — 1,131 Consumer real estate 1,156 2,264 Consumer and other 8,367 16,395 Total $ 172,955 $ 111,007
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, 2021 and 2020, 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, 2021 Modeled expected credit losses $ 46,946 $ 6,363 $ 16,676 $ 6,484 $ 6,397 $ 82,866 Q-Factor and other qualitative adjustments 14,609 5,374 127,860 65 1,440 149,348 Specific allocations 10,536 5,480 400 36 — 16,452 Total $ 72,091 $ 17,217 $ 144,936 $ 6,585 $ 7,837 $ 248,666 December 31, 2020 Modeled expected credit losses $ 65,645 $ 8,910 $ 125,126 $ 7,926 $ 6,945 $ 214,552 Q-Factor and other qualitative adjustments 2,877 21,216 9,253 — — 33,346 Specific allocations 5,321 9,427 513 — 18 15,279 Total $ 73,843 $ 39,553 $ 134,892 $ 7,926 $ 6,963 $ 263,177
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 2021, 2020 and 2019. 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 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 2020 Beginning balance $ 51,593 $ 37,382 $ 31,037 $ 4,113 $ 8,042 $ 132,167 Impacting of adopting ASC 326 21,263 (10,453) (13,519) 2,392 (2,248) (2,565) Credit loss (expense) benefit 15,156 85,889 124,427 1,906 9,632 237,010 Charge-offs (18,908) (76,107) (7,499) (2,186) (17,830) (122,530) Recoveries 4,739 2,842 446 1,701 9,367 19,095 Net (charge-offs) recoveries (14,169) (73,265) (7,053) (485) (8,463) (103,435) Ending balance $ 73,843 $ 39,553 $ 134,892 $ 7,926 $ 6,963 $ 263,177 2019 Beginning balance $ 48,580 $ 29,052 $ 38,777 $ 6,103 $ 9,620 $ 132,132 Credit loss (expense) benefit 13,144 14,388 (6,934) 467 12,694 33,759 Charge-offs (14,117) (7,500) (1,025) (3,665) (24,725) (51,032) Recoveries 3,986 1,442 219 1,208 10,453 17,308 Net (charge-offs) recoveries (10,131) (6,058) (806) (2,457) (14,272) (33,724) Ending balance $ 51,593 $ 37,382 $ 31,037 $ 4,113 $ 8,042 $ 132,167
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, 2021 and December 31, 2020. December 31, 2021 December 31, 2020 Loan Specific Allocations Loan Specific Allocations Commercial and industrial $ 24,523 $ 10,536 $ 21,287 $ 5,321 Energy 16,393 5,480 22,888 9,427 Paycheck Protection Program — — — — Commercial real estate: Buildings, land and other 24,670 200 34,057 513 Construction 948 200 1,684 — Consumer real estate 303 36 561 — Consumer and other — — 18 18 Total $ 66,837 $ 16,452 $ 80,495 $ 15,279

Premises and Equipment (Tables)

Premises and Equipment (Tables)	12 Months Ended
	Dec. 31, 2021
Property, Plant and Equipment [Abstract]
Premises and Equipment	Year-end premises and equipment were as follows: 2021 2020 Land $ 152,219 $ 128,739 Buildings 495,903 458,693 Technology, furniture and equipment 256,323 243,395 Leasehold improvements 192,207 183,827 Construction and projects in progress 14,513 41,202 Lease right-of-use assets 281,438 292,087 1,392,603 1,347,943 Less accumulated depreciation and amortization (342,272) (302,365) Total premises and equipment, net $ 1,050,331 $ 1,045,578
Lease Commitments, Components of Lease Expense	The components of total lease expense in 2021 and 2020 were as follows: 2021 2020 Amortization of lease right-of-use assets $ 32,811 $ 32,772 Short-term lease expense 1,595 1,799 Non-lease components (including taxes, insurance, common maintenance, etc.) 11,203 11,396 Total $ 45,609 $ 45,967
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, 2021: Future lease payments 2022 $ 32,222 2023 31,458 2024 29,398 2025 28,253 2026 27,833 Thereafter 245,819 Total undiscounted operating lease liability 394,983 Imputed interest 81,579 Total operating lease liability included in the accompanying balance sheet $ 313,404 Weighted-average lease term in years 14.73 Weighted-average discount rate 3.05%

Goodwill and Other Intangible_2

Goodwill and Other Intangible Assets (Tables)	12 Months Ended
	Dec. 31, 2021
Goodwill and Intangible Assets Disclosure [Abstract]
Schedule of Goodwill	Goodwill . Year-end goodwill was as follows: 2021 2020 Goodwill $ 654,952 $ 654,952
Schedule of Other Intangible Assets	Other Intangible Assets. Year-end other intangible assets were as follows: Gross Accumulated Net 2021 Core deposits $ 9,300 $ (8,582) $ 718 Customer relationships 2,385 (2,237) 148 $ 11,685 $ (10,819) $ 866 2020 Core deposits $ 9,300 $ (8,004) $ 1,296 Customer relationships 2,886 (2,619) 267 $ 12,186 $ (10,623) $ 1,563
Estimated Aggregate Future Amortization Expense for Intangible Assets	The estimated aggregate future amortization expense for intangible assets remaining as of December 31, 2021 is as follows: 2022 $ 481 2023 282 2024 87 2025 11 2026 5 Thereafter — $ 866

Deposits (Tables)

Deposits (Tables)	12 Months Ended
	Dec. 31, 2021
Deposits [Abstract]
Deposit Liabilities, Type	Year-end deposits were as follows: 2021 2020 Non-interest-bearing demand deposits $ 18,423,018 $ 15,117,051 Interest-bearing deposits: Savings and interest checking 11,930,959 9,730,292 Money market accounts 11,228,815 9,027,655 Time accounts 1,112,904 1,140,763 Total interest-bearing deposits 24,272,678 19,898,710 Total deposits $ 42,695,696 $ 35,015,761
Additional Information About Corporation's Deposits	The following table presents additional information about our year-end deposits: 2021 2020 Deposits from the Certificate of Deposit Account Registry Service (CDARS) $ — $ 372 Deposits from foreign sources (primarily Mexico) 993,479 884,169 Non-interest-bearing public funds deposits 1,235,026 960,072 Interest-bearing public funds deposits 810,863 652,761 Total deposits not covered by deposit insurance 24,125,359 18,694,320 Time deposits not covered by deposit insurance 238,608 237,298 Deposits from certain directors, executive officers and their affiliates 276,556 210,389
Scheduled Maturities of Time Deposits	Scheduled maturities of time deposits at December 31, 2021 were as follows: 2022 $ 891,392 2023 221,512 $ 1,112,904
Time Deposit Maturities	Scheduled maturities of time deposits not covered by deposit insurance at December 31, 2021, were as follows: Due within 3 months or less $ 92,403 Due after 3 months and within 6 months 34,038 Due after 6 months and within 12 months 58,357 Due after 12 months 53,810 $ 238,608

Off-Balance-Sheet Arrangement_2

Off-Balance-Sheet Arrangements, Commitments, Guarantees and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2021
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. 2021 2020 Commitments to extend credit $ 10,420,142 $ 9,814,475 Standby letters of credit 238,690 241,345 Deferred standby letter of credit fees 2,072 1,723
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. 2021 2020 2019 Beginning balance $ 44,152 $ 500 $ 500 Impact of adopting ASC 326 — 39,377 — Credit loss expense 6,162 4,275 — Ending balance $ 50,314 $ 44,152 $ 500

Capital and Regulatory Matters

Capital and Regulatory Matters (Tables)	12 Months Ended
	Dec. 31, 2021
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, 2021 and December 31, 2020 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 - Basel III Fully Phased-In Required to be Capital Ratio Capital Ratio Capital Ratio 2021 Common Equity Tier 1 to Risk-Weighted Assets Cullen/Frost $ 3,371,043 13.13 % $ 1,796,549 7.00 % $ 1,668,224 6.50 % Frost Bank 3,261,532 12.72 1,795,221 7.00 1,666,991 6.50 Tier 1 Capital to Risk-Weighted Assets Cullen/Frost 3,516,495 13.70 2,181,523 8.50 2,053,198 8.00 Frost Bank 3,261,532 12.72 2,179,911 8.50 2,051,681 8.00 Total Capital to Risk-Weighted Assets Cullen/Frost 3,966,244 15.45 2,694,823 10.50 2,566,498 10.00 Frost Bank 3,491,281 13.61 2,692,831 10.50 2,564,601 10.00 Leverage Ratio Cullen/Frost 3,516,495 7.34 1,917,533 4.00 2,396,917 5.00 Frost Bank 3,261,532 6.80 1,917,679 4.00 2,397,099 5.00 2020 Common Equity Tier 1 to Risk-Weighted Assets Cullen/Frost $ 3,058,447 12.86 % $ 1,664,867 7.00 % $ 1,545,948 6.50 % Frost Bank 3,030,093 12.77 1,661,620 7.00 1,542,933 6.50 Tier 1 Capital to Risk-Weighted Assets Cullen/Frost 3,203,899 13.47 2,021,624 8.50 1,902,705 8.00 Frost Bank 3,030,093 12.77 2,017,682 8.50 1,898,995 8.00 Total Capital to Risk-Weighted Assets Cullen/Frost 3,672,912 15.44 2,497,300 10.50 2,378,381 10.00 Frost Bank 3,266,106 13.76 2,492,430 10.50 2,373,743 10.00 Leverage Ratio Cullen/Frost 3,203,899 8.07 1,589,004 4.00 1,986,255 5.00 Frost Bank 3,030,093 7.63 1,588,200 4.00 1,985,250 5.00

Earnings Per Common Share (Tabl

Earnings Per Common Share (Tables)	12 Months Ended
	Dec. 31, 2021
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. 2021 2020 2019 Net Income $ 443,079 $ 331,151 $ 443,599 Less: Preferred stock dividends 7,157 2,016 8,063 Redemption of preferred stock — 5,514 — Net income available to common shareholders 435,922 323,621 435,536 Less: Earnings allocated to participating securities 3,881 3,136 3,687 Net earnings allocated to common stock $ 432,041 $ 320,485 $ 431,849 Distributed earnings allocated to common stock $ 187,202 $ 178,863 $ 175,540 Undistributed earnings allocated to common stock 244,839 141,622 256,309 Net earnings allocated to common stock $ 432,041 $ 320,485 $ 431,849 Weighted-average shares outstanding for basic earnings per common share 63,612,658 62,727,053 62,741,769 Dilutive effect of stock compensation 489,462 276,784 700,101 Weighted-average shares outstanding for diluted earnings per common share 64,102,120 63,003,837 63,441,870

Employee Benefit Plans (Tables)

Employee Benefit Plans (Tables)	12 Months Ended
	Dec. 31, 2021
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: 2021 2020 2019 Change in plan assets: Fair value of plan assets at beginning of year $ 182,088 $ 174,173 $ 152,820 Actual return on plan assets 24,908 16,599 29,945 Employer contributions 1,236 1,201 1,163 Benefits paid (10,485) (9,885) (9,755) Fair value of plan assets at end of year 197,747 182,088 174,173 Change in benefit obligation: Benefit obligation at beginning of year 197,593 186,641 167,107 Interest cost 3,341 5,010 6,472 Actuarial (gain) loss (4,524) 15,827 22,817 Benefits paid (10,485) (9,885) (9,755) Benefit obligation at end of year 185,925 197,593 186,641 Funded status of the plan at end of year and accrued benefit (liability) recognized $ 11,822 $ (15,505) $ (12,468) Accumulated benefit obligation at end of year $ 185,925 $ 197,593 $ 186,641
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 2021 2020 2021 2020 Projected benefit obligation $ 170,389 $ 180,986 $ 15,536 $ 16,607 Accumulated benefit obligation 170,389 180,986 15,536 16,607 Fair value of plan assets 197,747 182,088 — — Funded status of the plan at end of year and accrued benefit (liability) recognized 27,358 1,102 (15,536) (16,607)
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. 2021 2020 2019 Expected return on plan assets, net of expenses $ (12,839) $ (12,289) $ (10,772) Interest cost on projected benefit obligation 3,341 5,010 6,472 Net amortization and deferral 6,116 5,319 5,623 Net periodic expense (benefit) $ (3,382) $ (1,960) $ 1,323
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: 2021 2020 2019 Net actuarial gain (loss) $ 22,709 $ (6,199) $ 1,979 Deferred tax (expense) benefit (4,769) 1,302 (416) Other comprehensive income (loss), net of tax $ 17,940 $ (4,897) $ 1,563
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. 2021 2020 Net actuarial loss $ (41,634) $ (64,343) Deferred tax benefit 8,743 13,512 Amounts included in accumulated other comprehensive income/loss, net of tax (32,891) (50,831)
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. 2021 2020 2019 Benefit obligations: Discount rate 2.79 % 2.43 % 3.20 % Net periodic benefit cost: Discount rate 2.43 % 3.20 % 4.36 % Expected return on plan assets 7.25 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 17 - Fair Value Measurements). Our Restoration Plan is unfunded. 2021 2020 Level 1: Mutual funds $ 195,452 $ 180,693 Cash and cash equivalents 2,295 1,395 Total fair value of plan assets $ 197,747 $ 182,088
Expected Future Benefit Payments Related to Defined Benefit Plans	As of December 31, 2021, expected future benefit payments related to our defined benefit plans were as follows: 2022 $ 11,592 2023 11,805 2024 11,975 2025 11,982 2026 12,018 2027 through 2031 56,494 $ 115,866
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 2021, 2020 and 2019 was 30,723, 48,409 and 34,317, respectively. As of December 31, 2021, there were 777,687 shares remaining available for grant for future awards. Director Deferred Non-Vested Stock Performance Stock Units Outstanding Stock Options Number of Units Weighted- Number Weighted- Number of Units Weighted- Number Weighted- January 1, 2019 48,910 $ 71.14 383,797 $ 85.59 125,809 $ 82.55 2,352,008 $ 63.55 Granted 7,592 102.70 127,091 93.46 51,479 85.74 — — Exercised/vested (1,132) 106.03 (53,990) 65.11 — — (359,892) 57.71 Forfeited/expired — — (16,251) 89.71 — — (11,250) 65.11 December 31, 2019 55,370 74.76 440,647 90.22 177,288 83.48 1,980,866 64.60 Granted 10,428 73.84 151,038 66.79 72,618 57.89 — — Exercised/vested (12,938) 71.09 (117,990) 76.07 (41,755) 69.70 (235,880) 53.23 Forfeited/expired — — (3,336) 91.07 (6,894) 81.33 (5,427) 75.74 December 31, 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
Options Outstanding and Exercisable	Other information regarding options outstanding and exercisable as of December 31, 2021 is as follows: Options Outstanding Options Exercisable Range of Number Weighted- Weighted- Number Weighted- $ 50.01 to $ 55.00 123,314 $ 54.56 0.81 123,314 $ 54.56 65.01 to 70.00 319,081 65.11 3.72 319,081 65.11 70.01 to 75.00 169,726 71.39 1.78 169,726 71.39 75.01 to 80.00 265,560 78.92 2.75 265,560 78.92 Total 877,681 69.02 2.64 877,681 69.02 Total intrinsic value $ 50,070 $ 50,070
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: 2021 2020 2019 Shares issued from available treasury stock 987,758 408,563 399,224 Proceeds from stock option exercises $ 54,417 $ 12,557 $ 20,770 Intrinsic value of stock options exercised 43,904 5,365 13,713 Fair value of stock awards/units vested 15,751 12,773 5,192
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. 2021 2020 2019 Stock options $ — $ — $ 1,185 Non-vested stock awards/stock units 9,977 10,240 9,339 Deferred stock-units 700 770 780 Performance stock units 2,076 2,908 4,642 Total $ 12,753 $ 13,918 $ 15,946 Income tax benefit $ 1,713 $ 2,142 $ 2,359
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, 2021 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 stock awards/stock units $ 18,431 2.07 Performance stock units 9,818 2.16 Total $ 28,249

Other Non-Interest Income and_2

Other Non-Interest Income and Expense (Tables)	12 Months Ended
	Dec. 31, 2021
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. 2021 2020 2019 Other non-interest income: Other $ 48,528 $ 47,712 $ 43,563 Total $ 48,528 $ 47,712 $ 43,563 Other non-interest expense: Professional services $ 34,747 $ 37,253 $ 39,238 Advertising, promotions and public relations 34,539 34,390 38,001 Travel/meals and entertainment 4,946 7,109 16,459 Other 97,225 87,558 86,967 Total $ 171,457 $ 166,310 $ 180,665

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2021
Income Tax Disclosure [Abstract]
Income Tax Expense	Income tax expense was as follows: 2021 2020 2019 Current income tax expense $ 38,675 $ 36,002 $ 48,256 Deferred income tax expense (benefit) 7,784 (15,832) 7,614 Income tax expense, as reported $ 46,459 $ 20,170 $ 55,870 Effective tax rate 9.5 % 5.7 % 11.2 %
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. 2021 2020 2019 Income tax expense computed at the statutory rate $ 102,803 $ 73,777 $ 104,888 Effect of tax-exempt interest (50,740) (51,624) (49,166) Tax benefit on dividends paid in our 401k plan (1,764) (1,851) (1,743) Bank owned life insurance income (517) (783) (774) Non-deductible FDIC premiums 2,629 1,790 1,267 Non-deductible compensation 1,773 1,123 1,708 Non-deductible meals and entertainment 625 786 1,299 Net tax benefit from stock-based compensation (7,877) (852) (2,447) Asset contribution to a charitable trust — (2,556) — Tax basis adjustment of premises and equipment (1,026) — — Other 553 360 838 Income tax expense, as reported $ 46,459 $ 20,170 $ 55,870
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%. 2021 2020 Deferred tax assets: Lease liabilities under operating leases $ 65,815 $ 67,839 Allowance for credit losses 62,819 64,573 Net actuarial loss on defined benefit post-retirement benefit plans 8,743 13,512 Stock-based compensation 6,989 10,033 Bonus accrual 7,506 3,961 Deferred loan and lease origination fees 3,118 10,252 Other 3,834 3,834 Total gross deferred tax assets 158,824 174,004 Deferred tax liabilities: Net unrealized gain on securities available for sale and transferred securities (101,067) (149,870) Right-of-use assets under operating leases (59,415) (61,963) Premises and equipment (49,645) (49,602) Intangible assets (16,595) (14,596) Defined benefit post-retirement benefit plans (11,027) (10,081) Partnership interests — (2,913) Leases (712) (1,090) Other (1,611) (1,387) Total gross deferred tax liabilities (240,072) (291,502) Net deferred tax asset (liability) $ (81,248) $ (117,498)

Other Comprehensive Income (L_2

Other Comprehensive Income (Loss) (Tables)	12 Months Ended
	Dec. 31, 2021
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 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) 2020 Securities available for sale and transferred securities: Change in net unrealized gain/loss during the period $ 427,331 $ 89,741 $ 337,590 Change in net unrealized gain on securities transferred to held to maturity (1,256) (264) (992) Reclassification adjustment for net (gains) losses included in net income (108,989) (22,888) (86,101) Total securities available for sale and transferred securities 317,086 66,589 250,497 Defined-benefit post-retirement benefit plans: Change in the net actuarial gain/loss (11,518) (2,419) (9,099) Reclassification adjustment for net amortization of actuarial gain/loss included in net income as a component of net periodic cost (benefit) 5,319 1,117 4,202 Total defined-benefit post-retirement benefit plans (6,199) (1,302) (4,897) Total other comprehensive income (loss) $ 310,887 $ 65,287 $ 245,600 2019 Securities available for sale and transferred securities: Change in net unrealized gain/loss during the period $ 418,556 $ 87,897 $ 330,659 Change in net unrealized gain on securities transferred to held to maturity (1,292) (271) (1,021) Reclassification adjustment for net (gains) losses included in net income (293) (62) (231) Total securities available for sale and transferred securities 416,971 87,564 329,407 Defined-benefit post-retirement benefit plans: Change in the net actuarial gain/loss (3,644) (765) (2,879) Reclassification adjustment for net amortization of actuarial gain/loss included in net income as a component of net periodic cost (benefit) 5,623 1,181 4,442 Total defined-benefit post-retirement benefit plans 1,979 416 1,563 Total other comprehensive income (loss) $ 418,950 $ 87,980 $ 330,970
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, 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 Balance January 1, 2020 $ 313,304 $ (45,934) $ 267,370 Other comprehensive income (loss) before reclassification 336,598 (9,099) 327,499 Reclassification of amounts included in net income (86,101) 4,202 (81,899) Net other comprehensive income (loss) during period 250,497 (4,897) 245,600 Balance December 31, 2020 $ 563,801 $ (50,831) $ 512,970 Balance January 1, 2019 $ (16,103) $ (47,497) $ (63,600) Other comprehensive income (loss) before reclassification 329,638 (2,879) 326,759 Reclassification of amounts included in net income (231) 4,442 4,211 Net other comprehensive income (loss) during period 329,407 1,563 330,970 Balance December 31, 2019 $ 313,304 $ (45,934) $ 267,370

Derivative Financial Instrume_2

Derivative Financial Instruments (Tables)	12 Months Ended
	Dec. 31, 2021
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, 2021 and 2020 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, 2021 and 2020. December 31, 2021 December 31, 2020 Notional Estimated Notional Estimated Derivatives designated as hedges of fair value: Financial institution counterparties: Loan/lease interest rate swaps - liabilities $ 2,426 $ (34) $ 3,724 $ (134) Non-hedging interest rate derivatives: Financial institution counterparties: Loan/lease interest rate swaps - assets 247,592 1,207 — — Loan/lease interest rate swaps - liabilities 928,756 (19,142) 1,173,173 (33,812) Loan/lease interest rate caps - assets 270,431 3,239 356,601 1,241 Customer counterparties: Loan/lease interest rate swaps - assets 928,756 39,864 1,173,173 84,424 Loan/lease interest rate swaps - liabilities 247,592 (2,846) — — Loan/lease interest rate caps - liabilities 270,431 (3,239) 356,601 (1,241)
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, 2021 were as follows: Weighted-Average Interest Interest Interest rate swaps: Fair value hedge loan/lease interest rate swaps 2.48 % 0.10 % Non-hedging interest rate swaps - financial institution counterparties 3.73 1.90 Non-hedging interest rate swaps - customer counterparties 1.90 3.73
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, 2021 December 31, 2020 Notional Notional Estimated Notional Estimated Financial institution counterparties: Oil - assets Barrels 4,809 $ 14,721 3,056 $ 8,341 Oil - liabilities Barrels 7,032 (73,594) 6,391 (32,112) Natural gas - assets MMBTUs 15,947 4,143 9,281 1,529 Natural gas - liabilities MMBTUs 29,446 (21,249) 15,079 (3,265) Customer counterparties: Oil - assets Barrels 7,046 74,437 6,391 32,670 Oil - liabilities Barrels 4,796 (14,294) 3,056 (8,264) Natural gas - assets MMBTUs 29,446 21,456 17,636 3,451 Natural gas - liabilities MMBTUs 15,947 (4,124) 6,724 (1,458)
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, 2021 December 31, 2020 Notional Notional Estimated Notional Estimated Financial institution counterparties: Forward contracts - assets EUR 1,900 $ 29 — $ — Forward contracts - assets CAD 658 — — — Customer counterparties: Forward contracts - assets EUR — — — — Forward contracts - assets CAD 658 4 — — Forward contracts - liabilities EUR 1,900 (55) — —
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: 2021 2020 2019 Commercial loan/lease interest rate swaps: Amount of gain (loss) included in interest income on loans $ (91) $ (111) $ 86 Amount of (gain) loss included in other non-interest expense 10 9 —
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. 2021 2020 2019 Non-hedging interest rate derivatives: Other non-interest income $ 4,285 $ 3,413 $ 2,005 Other non-interest expense (1) 1 (1) Non-hedging commodity derivatives: Other non-interest income 4,052 1,768 503 Non-hedging foreign currency derivatives: Other non-interest income 39 28 51 Non-hedging other derivatives: Other non-interest income — 5,992 750

Balance Sheet Offsetting Balanc

Balance Sheet Offsetting Balance Sheet Offsetting (Tables)	12 Months Ended
	Dec. 31, 2021
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, 2021 is presented in the following tables. Gross Amount Gross Amount Net Amount December 31, 2021 Financial assets: Derivatives: Loan/lease interest rate swaps and caps $ 4,446 $ — $ 4,446 Commodity swaps and options 18,864 — 18,864 Foreign currency forward contracts 29 — 29 Total derivatives 23,339 — 23,339 Resell agreements 7,903 — 7,903 Total $ 31,242 $ — $ 31,242 Financial liabilities: Derivatives: Loan/lease interest rate swaps $ 19,176 $ — $ 19,176 Commodity swaps and options 94,843 — 94,843 Total derivatives 114,019 — 114,019 Repurchase agreements 2,740,799 — 2,740,799 Total $ 2,854,818 $ — $ 2,854,818 Information about financial instruments that are eligible for offset in the consolidated balance sheet as of December 31, 2020 is presented in the following tables. Gross Amount Gross Amount Net Amount December 31, 2020 Financial assets: Derivatives: Loan/lease interest rate swaps and caps $ 1,241 $ — $ 1,241 Commodity swaps and options 9,870 — 9,870 Total derivatives 11,111 — 11,111 Resell agreements — — — Total $ 11,111 $ — $ 11,111 Financial liabilities: Derivatives: Loan/lease interest rate swaps $ 33,946 $ — $ 33,946 Commodity swaps and options 35,377 — 35,377 Foreign currency forward contracts — — — Total derivatives 69,323 — 69,323 Repurchase agreements 2,068,147 — 2,068,147 Total $ 2,137,470 $ — $ 2,137,470
Financial Instruments Derivative Assets Liabilities And Resell Agreements Net Of Amount Not Offset	Gross Amounts Not Offset Net Amount Financial Collateral Net December 31, 2021 Financial assets: Derivatives: Counterparty A $ 6 $ (6) $ — $ — Counterparty B 7,655 (7,655) — — Other counterparties 15,678 (15,678) — — Total derivatives 23,339 (23,339) — — Resell agreements 7,903 — (7,903) — Total $ 31,242 $ (23,339) $ (7,903) $ — Financial liabilities: Derivatives: Counterparty A $ 3,870 $ (6) $ (3,864) $ — Counterparty B 28,130 (7,655) (20,475) — Counterparty C 9 — (9) — Other counterparties 82,010 (15,678) (66,225) 107 Total derivatives 114,019 (23,339) (90,573) 107 Repurchase agreements 2,740,799 — (2,740,799) — Total $ 2,854,818 $ (23,339) $ (2,831,372) $ 107 Gross Amounts Not Offset Net Amount Financial Collateral Net December 31, 2020 Financial assets: Derivatives: Counterparty A $ 2 $ (2) $ — $ — Counterparty B 5,838 (5,838) — — Other counterparties 5,271 (5,271) — — Total derivatives 11,111 (11,111) — — Resell agreements — — — — Total $ 11,111 $ (11,111) $ — $ — Financial liabilities: Derivatives: Counterparty A $ 6,430 $ (2) $ (6,428) $ — Counterparty B 20,722 (5,838) (14,700) 184 Counterparty C 71 — (71) — Other counterparties 42,100 (5,271) (35,832) 997 Total derivatives 69,323 (11,111) (57,031) 1,181 Repurchase agreements 2,068,147 — (2,068,147) — Total $ 2,137,470 $ (11,111) $ (2,125,178) $ 1,181
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, 2021 and December 31, 2020 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, 2021 Repurchase agreements: U.S. Treasury $ 1,342,591 $ — $ — $ — $ 1,342,591 Residential mortgage-backed securities 1,398,208 — — — 1,398,208 Total borrowings $ 2,740,799 $ — $ — $ — $ 2,740,799 Gross amount of recognized liabilities for repurchase agreements $ 2,740,799 Amounts related to agreements not included in offsetting disclosures above $ — December 31, 2020 Repurchase agreements: U.S. Treasury $ 692,860 $ — $ — $ — $ 692,860 Residential mortgage-backed securities 1,375,287 — — — 1,375,287 Total borrowings $ 2,068,147 $ — $ — $ — $ 2,068,147 Gross amount of recognized liabilities for repurchase agreements $ 2,068,147 Amounts related to agreements not included in offsetting disclosures above $ —

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	12 Months Ended
	Dec. 31, 2021
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, 2021 and 2020, 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 2021 Securities available for sale: U.S. Treasury $ 2,179,433 $ — $ — $ 2,179,433 Residential mortgage-backed securities — 4,066,265 — 4,066,265 States and political subdivisions — 7,636,571 — 7,636,571 Other — 42,359 — 42,359 Trading account securities: U.S. Treasury 24,237 — — 24,237 States and political subdivisions — 925 — 925 Derivative assets: Interest rate swaps, caps and floors — 44,310 — 44,310 Commodity swaps and options — 114,757 — 114,757 Foreign currency forward contracts 33 — — 33 Derivative liabilities: Interest rate swaps, caps and floors — 25,261 — 25,261 Commodity swaps and options — 113,261 — 113,261 Foreign currency forward contracts 55 — — 55 2020 Securities available for sale: U.S. Treasury $ 1,119,633 $ — $ — $ 1,119,633 Residential mortgage-backed securities — 1,987,679 — 1,987,679 States and political subdivisions — 7,287,902 — 7,287,902 Other — 42,351 — 42,351 Trading account securities: U.S. Treasury 23,996 — — 23,996 States and political subdivisions — 460 — 460 Derivative assets: Interest rate swaps, caps and floors — 85,665 — 85,665 Commodity swaps and options — 45,535 456 45,991 Derivative liabilities: Interest rate swaps, caps and floors — 35,187 — 35,187 Commodity swaps and options — 45,099 — 45,099
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: 2021 2020 2019 Level 2 Carrying value before allocations $ 1,333 $ 1,559 $ 2,354 Specific (allocations) reversals of prior allocations 214 (450) (383) Fair value $ 1,547 $ 1,109 $ 1,971 Level 3 Carrying value before allocations $ 16,074 $ 34,302 $ 65,176 Specific (allocations) reversals of prior allocations (5,178) (11,151) (18,019) Fair value $ 10,896 $ 23,151 $ 47,157
Foreclosed Assets Remeasured and Reported at Fair Value	The following table presents foreclosed assets that were remeasured and reported at fair value: 2021 2020 2019 Foreclosed assets remeasured at initial recognition: Carrying value of foreclosed assets prior to remeasurement $ — $ — $ 1,348 Charge-offs recognized in the allowance for credit losses on loans — — (76) Fair value $ — $ — $ 1,272 Foreclosed assets remeasured subsequent to initial recognition: Carrying value of foreclosed assets prior to remeasurement $ 14 $ 328 $ — Write-downs included in other non-interest expense (14) (231) — Fair value $ — $ 97 $ —
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, 2021 December 31, 2020 Carrying Estimated Carrying Estimated Financial assets: Level 2 inputs: Cash and cash equivalents $ 16,583,000 $ 16,583,000 $ 10,288,853 $ 10,288,853 Securities held to maturity 1,749,179 1,809,143 1,945,673 2,052,896 Cash surrender value of life insurance policies 190,139 190,139 189,984 189,984 Accrued interest receivable 179,111 179,111 181,432 181,432 Level 3 inputs: Loans, net 16,087,731 16,079,454 17,218,132 17,390,683 Financial liabilities: Level 2 inputs: Deposits 42,695,696 41,343,426 35,015,761 35,018,185 Federal funds purchased 25,925 25,925 48,850 48,850 Repurchase agreements 2,740,799 2,740,799 2,068,147 2,068,147 Junior subordinated deferrable interest debentures 123,011 123,712 136,357 137,115 Subordinated notes 99,178 111,430 99,021 115,717 Accrued interest payable 3,026 3,026 8,127 8,127

Operating Segments (Tables)

Operating Segments (Tables)	12 Months Ended
	Dec. 31, 2021
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 $43.3 billion, $38.6 billion and $37.8 billion at December 31, 2021, 2020 and 2019. Banking Frost Non-Banks Consolidated 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 Banking Frost Non-Banks Consolidated 2020 Net interest income (expense) $ 981,441 $ 2,776 $ (8,216) $ 976,001 Credit loss expense 241,230 — — 241,230 Non-interest income 321,136 145,268 (950) 465,454 Non-interest expense 718,519 123,630 6,755 848,904 Income (loss) before income taxes 342,828 24,414 (15,921) 351,321 Income tax expense (benefit) 20,347 5,127 (5,304) 20,170 Net income (loss) 322,481 19,287 (10,617) 331,151 Preferred stock dividends — — 2,016 2,016 Redemption of preferred stock — — 5,514 5,514 Net income (loss) available to common shareholders $ 322,481 $ 19,287 $ (18,147) $ 323,621 Revenues from (expenses to) external customers $ 1,302,577 $ 148,044 $ (9,166) $ 1,441,455 Average assets (in millions) $ 37,892 $ 59 $ 10 $ 37,961 2019 Net interest income (expense) $ 1,010,368 $ 4,001 $ (10,364) $ 1,004,005 Credit loss expense 33,758 1 — 33,759 Non-interest income 218,447 145,905 (450) 363,902 Non-interest expense 703,121 124,622 6,936 834,679 Income (loss) before income taxes 491,936 25,283 (17,750) 499,469 Income tax expense (benefit) 55,520 5,308 (4,958) 55,870 Net income (loss) 436,416 19,975 (12,792) 443,599 Preferred stock dividends — — 8,063 8,063 Net income (loss) available to common shareholders $ 436,416 $ 19,975 $ (20,855) $ 435,536 Revenues from (expenses to) external customers $ 1,228,815 $ 149,906 $ (10,814) $ 1,367,907 Average assets (in millions) $ 32,019 $ 56 $ 11 $ 32,086

Condensed Financial Statement_2

Condensed Financial Statements of Parent Company (Tables)	12 Months Ended
	Dec. 31, 2021
Condensed Financial Information Disclosure [Abstract]
Schedule of Condensed Balance Sheets	Condensed Balance Sheets December 31, 2021 2020 Assets: Cash $ 471,875 $ 381,240 Resell agreements — — Total cash and cash equivalents 471,875 381,240 Investment in subsidiaries 4,222,288 4,155,619 Accrued interest receivable and other assets 2,228 2,164 Total assets $ 4,696,391 $ 4,539,023 Liabilities: Junior subordinated deferrable interest debentures, net of unamortized issuance costs $ 123,011 $ 136,357 Subordinated notes, net of unamortized issuance costs 99,178 99,021 Accrued interest payable and other liabilities 34,647 10,629 Total liabilities 256,836 246,007 Shareholders’ Equity 4,439,555 4,293,016 Total liabilities and shareholders’ equity $ 4,696,391 $ 4,539,023
Schedule of Condensed Statements of Income	Condensed Statements of Income Year Ended December 31, 2021 2020 2019 Income: Dividend income paid by Frost Bank $ 219,386 $ 298,884 $ 234,531 Dividend income paid by non-banks 473 736 1,822 Interest and other income 101 446 2,868 Total income 219,960 300,066 239,221 Expenses: Interest expense 7,141 8,216 10,363 Salaries and employee benefits 1,499 1,581 1,551 Other 5,867 6,833 7,033 Total expenses 14,507 16,630 18,947 Income before income taxes and equity in undistributed earnings of subsidiaries 205,453 283,436 220,274 Income tax benefit 4,899 5,406 5,135 Equity in undistributed earnings of subsidiaries 232,727 42,309 218,190 Net income 443,079 331,151 443,599 Preferred stock dividends 7,157 2,016 8,063 Redemption of preferred stock — 5,514 — Net income available to common shareholders $ 435,922 $ 323,621 $ 435,536
Schedule of Condensed Statements of Cash Flows	Condensed Statements of Cash Flows Year Ended December 31, 2021 2020 2019 Operating Activities: Net income $ 443,079 $ 331,151 $ 443,599 Adjustments to reconcile net income to net cash provided by operating activities: Equity in undistributed earnings of subsidiaries (232,727) (42,309) (218,190) Stock-based compensation 700 770 780 Net tax benefit from stock-based compensation 278 370 240 Net change in other assets and other liabilities 23,890 (8,937) 22,216 Net cash from operating activities 235,220 281,045 248,645 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) — — Redemption of Series A preferred stock — (150,000) — Proceeds from issuance of Series B preferred stock — 145,452 — Proceeds from stock option exercises 54,417 12,557 20,770 Proceeds from stock-based compensation activities of subsidiaries 12,053 13,148 15,166 Purchase of treasury stock (3,864) (15,785) (68,793) Treasury stock issued to 401(k) stock purchase plan 1,749 10,307 — Cash dividends paid on preferred stock (7,157) (2,016) (8,063) Cash dividends paid on common stock (188,786) (180,584) (177,006) Net cash from financing activities (144,991) (166,921) (217,926) Net change in cash and cash equivalents 90,635 114,124 30,719 Cash and cash equivalents at beginning of year 381,240 267,116 236,397 Cash and cash equivalents at end of year $ 471,875 $ 381,240 $ 267,116

Summary of Significant Accoun_4

Summary of Significant Accounting Policies (Narrative) (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Jan. 01, 2020	Jan. 01, 2019	Dec. 31, 2018
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cash on hand or on deposit required		$ 42,000
Cash collateral on deposit	$ 110,300	74,000
Foreclosed assets	3,400	850
Real Estate Owned, Valuation Allowance, Provision	$ 14	$ 231	$ 0
Amount of significant concentrations of any properties with write downs from any single geographic region	0.00%	0.00%	0.00%
Cumulative effect of accounting change			$ (29,252)			$ (14,672)
Operating Lease, Right-of-Use Asset	$ 281,438	$ 292,087
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	80.00%
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	125.00%
Premises and Equipment
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating Lease, Right-of-Use Asset	$ 281,400	292,100			$ 170,500
Other Liabilities [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating lease, liability	$ 313,404	$ 323,000			174,400
Retained Earnings [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect of accounting change			$ (29,252)	$ (29,300)	$ (14,700)	$ (14,672)

Summary of Significant Accoun_5

Summary of Significant Accounting Policies (Additional Cash Flow Information) (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Accounting Policies [Abstract]
Cash paid for interest	$ 29,003	$ 49,300	$ 124,781
Cash paid for income tax	39,852	44,140	45,352
Transfer of securities from available for sale to held to maturity	0	0	377,812
Exchange of real estate	11,036	0	0
Unsettled securities transactions	27,032	57,783	0
Loans foreclosed and transferred to other real estate owned and foreclosed assets	3,464	140	1,348
Loans to facilitate the sale of other real estate owned	0	0	847
Right-of-use lease assets obtained in exchange for lessee operating lease liabilities	12,854	18,284	319,286
Treasury stock issued to 401(k) stock purchase plan	$ 1,749	$ 10,307	$ 0

Summary of Significant Accoun_6

Summary of Significant Accounting Policies (Impact of Adoption of New Accounting Standard Related to CECL) (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020	Jan. 01, 2020	Dec. 31, 2019	Jan. 01, 2019	Dec. 31, 2018
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Securities held to maturity, net of allowance for credit losses of $158 in 2021 and $160 in 2020	$ 158	$ 160
Financing Receivable, Allowance for Credit Loss	248,666	263,177
Off-Balance Sheet, Credit Loss, Liability	50,314	44,152		$ 500		$ 500
Cumulative effect of accounting change				(29,252)		(14,672)
Retained Earnings [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect of accounting change			$ (29,300)	(29,252)	$ (14,700)	(14,672)
Commercial Portfolio Segment [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Financing Receivable, Allowance for Credit Loss	72,091	73,843		51,593		48,580
Commercial Portfolio Segment [Member] | Retained Earnings [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect of accounting change			(16,798)
Commercial and Industrial Total Energy Loans [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Financing Receivable, Allowance for Credit Loss	17,217	39,553		37,382		29,052
Commercial and Industrial Total Energy Loans [Member] | Retained Earnings [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect of accounting change			8,258
Commercial Real Estate Portfolio Segment [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Financing Receivable, Allowance for Credit Loss	144,936	134,892		31,037		38,777
Commercial Real Estate Portfolio Segment [Member] | Retained Earnings [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect of accounting change			10,680
Total consumer real estate loans [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Financing Receivable, Allowance for Credit Loss	6,585	7,926		4,113		6,103
Total consumer real estate loans [Member] | Retained Earnings [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect of accounting change			(1,890)
Consumer Loan [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Financing Receivable, Allowance for Credit Loss	7,837	6,963		8,042		9,620
Consumer Loan [Member] | Retained Earnings [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect of accounting change			1,776
Loans Receivable [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Financing Receivable, Allowance for Credit Loss	248,666	263,177		132,167		$ 132,132
Loans Receivable [Member] | Retained Earnings [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect of accounting change			2,026
US Treasury [Member] | Retained Earnings [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect of accounting change			0
Residential Mortgage Backed Securities [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Securities held to maturity, net of allowance for credit losses of $158 in 2021 and $160 in 2020	0	0
Residential Mortgage Backed Securities [Member] | Retained Earnings [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect of accounting change			0
States and Political Subdivisions [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Securities held to maturity, net of allowance for credit losses of $158 in 2021 and $160 in 2020	158	160
States and Political Subdivisions [Member] | Retained Earnings [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect of accounting change			(170)
Other [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Securities held to maturity, net of allowance for credit losses of $158 in 2021 and $160 in 2020	0	0
Other [Member] | Retained Earnings [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect of accounting change			0
Debt Securities [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Securities held to maturity, net of allowance for credit losses of $158 in 2021 and $160 in 2020	158	$ 160		$ 0
Debt Securities [Member] | Retained Earnings [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect of accounting change			(170)
Commitments to Extend Credit [Member] | Retained Earnings [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect of accounting change			(31,108)
Pre-Adoption Allowance [Member] | Commercial Portfolio Segment [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Financing Receivable, Allowance for Credit Loss			51,593
Pre-Adoption Allowance [Member] | Commercial and Industrial Total Energy Loans [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Financing Receivable, Allowance for Credit Loss			37,382
Pre-Adoption Allowance [Member] | Commercial Real Estate Portfolio Segment [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Financing Receivable, Allowance for Credit Loss			31,037
Pre-Adoption Allowance [Member] | Total consumer real estate loans [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Financing Receivable, Allowance for Credit Loss			4,113
Pre-Adoption Allowance [Member] | Consumer Loan [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Financing Receivable, Allowance for Credit Loss			8,042
Pre-Adoption Allowance [Member] | Loans Receivable [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Financing Receivable, Allowance for Credit Loss			132,167
Pre-Adoption Allowance [Member] | US Treasury [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Securities held to maturity, net of allowance for credit losses of $158 in 2021 and $160 in 2020			0
Pre-Adoption Allowance [Member] | Residential Mortgage Backed Securities [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Securities held to maturity, net of allowance for credit losses of $158 in 2021 and $160 in 2020			0
Pre-Adoption Allowance [Member] | States and Political Subdivisions [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Securities held to maturity, net of allowance for credit losses of $158 in 2021 and $160 in 2020			0
Pre-Adoption Allowance [Member] | Other [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Securities held to maturity, net of allowance for credit losses of $158 in 2021 and $160 in 2020			0
Pre-Adoption Allowance [Member] | Debt Securities [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Securities held to maturity, net of allowance for credit losses of $158 in 2021 and $160 in 2020			0
Pre-Adoption Allowance [Member] | Commitments to Extend Credit [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Off-Balance Sheet, Credit Loss, Liability			500
Accounting Standards Update 2016-13 [Member] | Commercial Portfolio Segment [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Financing Receivable, Allowance for Credit Loss			21,263
Accounting Standards Update 2016-13 [Member] | Commercial and Industrial Total Energy Loans [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Financing Receivable, Allowance for Credit Loss			(10,453)
Accounting Standards Update 2016-13 [Member] | Commercial Real Estate Portfolio Segment [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Financing Receivable, Allowance for Credit Loss			(13,519)
Accounting Standards Update 2016-13 [Member] | Total consumer real estate loans [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Financing Receivable, Allowance for Credit Loss			2,392
Accounting Standards Update 2016-13 [Member] | Consumer Loan [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Financing Receivable, Allowance for Credit Loss			(2,248)
Accounting Standards Update 2016-13 [Member] | Loans Receivable [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Financing Receivable, Allowance for Credit Loss			(2,565)
Accounting Standards Update 2016-13 [Member] | US Treasury [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Securities held to maturity, net of allowance for credit losses of $158 in 2021 and $160 in 2020			0
Accounting Standards Update 2016-13 [Member] | Residential Mortgage Backed Securities [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Securities held to maturity, net of allowance for credit losses of $158 in 2021 and $160 in 2020			0
Accounting Standards Update 2016-13 [Member] | States and Political Subdivisions [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Securities held to maturity, net of allowance for credit losses of $158 in 2021 and $160 in 2020			215
Accounting Standards Update 2016-13 [Member] | Other [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Securities held to maturity, net of allowance for credit losses of $158 in 2021 and $160 in 2020			0
Accounting Standards Update 2016-13 [Member] | Debt Securities [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Securities held to maturity, net of allowance for credit losses of $158 in 2021 and $160 in 2020	$ 0		215
Accounting Standards Update 2016-13 [Member] | Commitments to Extend Credit [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Off-Balance Sheet, Credit Loss, Liability			39,377
Post-Adoption Allowance [Member] | Commercial Portfolio Segment [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Financing Receivable, Allowance for Credit Loss			72,856
Post-Adoption Allowance [Member] | Commercial and Industrial Total Energy Loans [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Financing Receivable, Allowance for Credit Loss			26,929
Post-Adoption Allowance [Member] | Commercial Real Estate Portfolio Segment [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Financing Receivable, Allowance for Credit Loss			17,518
Post-Adoption Allowance [Member] | Total consumer real estate loans [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Financing Receivable, Allowance for Credit Loss			6,505
Post-Adoption Allowance [Member] | Consumer Loan [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Financing Receivable, Allowance for Credit Loss			5,794
Post-Adoption Allowance [Member] | Loans Receivable [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Financing Receivable, Allowance for Credit Loss			129,602
Post-Adoption Allowance [Member] | US Treasury [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Securities held to maturity, net of allowance for credit losses of $158 in 2021 and $160 in 2020			0
Post-Adoption Allowance [Member] | Residential Mortgage Backed Securities [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Securities held to maturity, net of allowance for credit losses of $158 in 2021 and $160 in 2020			0
Post-Adoption Allowance [Member] | States and Political Subdivisions [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Securities held to maturity, net of allowance for credit losses of $158 in 2021 and $160 in 2020			215
Post-Adoption Allowance [Member] | Other [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Securities held to maturity, net of allowance for credit losses of $158 in 2021 and $160 in 2020			0
Post-Adoption Allowance [Member] | Debt Securities [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Securities held to maturity, net of allowance for credit losses of $158 in 2021 and $160 in 2020			215
Post-Adoption Allowance [Member] | Commitments to Extend Credit [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Off-Balance Sheet, Credit Loss, Liability			$ 39,877

Securities (Narrative) (Detail)

Securities (Narrative) (Detail) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Schedule Of Marketable Securities [Line Items]
Net unamortized, unrealized gain on transferred securities included in accumulated other comprehensive income, pre tax	$ 2,500	$ 3,500
Net unamortized, unrealized gain on transferred securities included in accumulated other comprehensive income, net of tax	2,000	2,800
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 $158 in 2021 and $160 in 2020	$ 158	160
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	76.60%
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 $158 in 2021 and $160 in 2020	158	160	$ 0
Held-to-maturity Securities [Member]
Schedule Of Marketable Securities [Line Items]
Carry value of securities pledged	642,300	659,200
Accrued interest receivable	18,400	21,700
Reclassified To Held To Maturity [Member]
Schedule Of Marketable Securities [Line Items]
Securities available for sale, at estimated fair value			377,800
Available for sale securities reclassified to held to maturity, unrealized gain			3,300
Available for sale securities reclassified to held to maturity, unrealized gain net of tax			$ 2,600
Available-for-sale Securities [Member]
Schedule Of Marketable Securities [Line Items]
Carry value of securities pledged	5,800,000	4,400,000
Accrued interest receivable	120,500	$ 111,000
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 $158 in 2021 and $160 in 2020	0
Pre-Refunded [Member] | Debt Securities [Member]
Schedule Of Marketable Securities [Line Items]
Securities held to maturity, net of allowance for credit losses of $158 in 2021 and $160 in 2020	$ 0

Securities (Year End Securities

Securities (Year End Securities Held to Maturity) (Detail) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Schedule of Investments [Line Items]
Held to Maturity, Amortized Cost	$ 1,749,337	$ 1,945,833
Debt Securities, Held-to-maturity, Accumulated Unrecognized Gain	59,907	107,063
Debt Securities, Held-to-maturity, Accumulated Unrecognized Loss	101	0
Debt Securities, Held to Maturity, Estimated Fair Value	1,809,143	2,052,896
Debt Securities, Held-to-maturity, Allowance for Credit Loss	(158)	(160)
Securities held to maturity, net of allowance for credit losses of $158 in 2021 and $160 in 2020	1,749,179	1,945,673
Residential Mortgage Backed Securities [Member]
Schedule of Investments [Line Items]
Held to Maturity, Amortized Cost	527,264	528,784
Debt Securities, Held-to-maturity, Accumulated Unrecognized Gain	18,766	41,742
Debt Securities, Held-to-maturity, Accumulated Unrecognized Loss	0	0
Debt Securities, Held to Maturity, Estimated Fair Value	546,030	570,526
Debt Securities, Held-to-maturity, Allowance for Credit Loss	0	0
Securities held to maturity, net of allowance for credit losses of $158 in 2021 and $160 in 2020	527,264	528,784
States and Political Subdivisions [Member]
Schedule of Investments [Line Items]
Held to Maturity, Amortized Cost	1,220,573	1,415,549
Debt Securities, Held-to-maturity, Accumulated Unrecognized Gain	41,141	65,321
Debt Securities, Held-to-maturity, Accumulated Unrecognized Loss	101	0
Debt Securities, Held to Maturity, Estimated Fair Value	1,261,613	1,480,870
Debt Securities, Held-to-maturity, Allowance for Credit Loss	(158)	(160)
Securities held to maturity, net of allowance for credit losses of $158 in 2021 and $160 in 2020	1,220,415	1,415,389
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	0	0
Debt Securities, Held to Maturity, Estimated Fair Value	1,500	1,500
Debt Securities, Held-to-maturity, Allowance for Credit Loss	0	0
Securities held to maturity, net of allowance for credit losses of $158 in 2021 and $160 in 2020	$ 1,500	$ 1,500

Securities (Securities Moody's

Securities (Securities Moody's and Standard & Poor's Bond Rating) (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Schedule of Held-to-maturity Securities [Line Items]
Held to Maturity, Amortized Cost	$ 1,749,337	$ 1,945,833
States and Political Subdivisions [Member]
Schedule of Held-to-maturity Securities [Line Items]
Held to Maturity, Amortized Cost	1,220,573	1,415,549
States and Political Subdivisions [Member] | Not Guaranteed or Pre-Refunded [Member]
Schedule of Held-to-maturity Securities [Line Items]
Held to Maturity, Amortized Cost	196,674
States and Political Subdivisions [Member] | Guaranteed by the Texas PSF [Member]
Schedule of Held-to-maturity Securities [Line Items]
Held to Maturity, Amortized Cost	460,648
States and Political Subdivisions [Member] | Pre-Refunded [Member]
Schedule of Held-to-maturity Securities [Line Items]
Held to Maturity, Amortized Cost	563,251
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	1,116,278
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	92,379
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	460,648
Aaa/AAA [Member] | States and Political Subdivisions [Member] | Pre-Refunded [Member]
Schedule of Held-to-maturity Securities [Line Items]
Held to Maturity, Amortized Cost	563,251
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	104,295
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	104,295
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] | 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] | 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, 2021	Dec. 31, 2020	Jan. 01, 2020	Dec. 31, 2019
Schedule of Held-to-maturity Securities [Line Items]
Securities held to maturity, net of allowance for credit losses of $158 in 2021 and $160 in 2020	$ 158	$ 160
Debt Securities [Member]
Schedule of Held-to-maturity Securities [Line Items]
Securities held to maturity, net of allowance for credit losses of $158 in 2021 and $160 in 2020	158	160		$ 0
Debt Securities, Held-to-maturity, Allowance for Credit Loss, Period Increase (Decrease)	(2)	$ (55)
Debt Securities [Member] | Accounting Standards Update 2016-13 [Member]
Schedule of Held-to-maturity Securities [Line Items]
Securities held to maturity, net of allowance for credit losses of $158 in 2021 and $160 in 2020	$ 0		$ 215

Securities (Securities Availabl

Securities (Securities Available for Sale) (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Schedule of Investments [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	$ 13,445,888	$ 9,727,401
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	518,805	710,168
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	40,065	4
Debt Securities, Available-for-sale, Allowance for Credit Loss	0	0
Debt Securities, Available-for-sale	13,924,628	10,437,565
US Treasury [Member]
Schedule of Investments [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	2,165,702	1,084,542
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	23,333	35,091
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	9,602	0
Debt Securities, Available-for-sale, Allowance for Credit Loss	0	0
Debt Securities, Available-for-sale	2,179,433	1,119,633
Residential Mortgage Backed Securities [Member]
Schedule of Investments [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	4,059,692	1,916,581
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	31,662	71,102
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	25,089	4
Debt Securities, Available-for-sale, Allowance for Credit Loss	0	0
Debt Securities, Available-for-sale	4,066,265	1,987,679
States and Political Subdivisions [Member]
Schedule of Investments [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	7,178,135	6,683,927
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	463,810	603,975
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	5,374	0
Debt Securities, Available-for-sale, Allowance for Credit Loss	0	0
Debt Securities, Available-for-sale	7,636,571	7,287,902
Other [Member]
Schedule of Investments [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	42,359	42,351
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	$ 42,359	$ 42,351

Securities (Year End Securiti_2

Securities (Year End Securities with Unrealized Losses Segregated by Length of Impairment) (Detail) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Schedule of Available-for-Sale Securities [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	$ 3,267,559
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	38,301
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	51,638
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	1,764
Available for Sale, Total Estimated Fair Value	3,319,197
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	40,065	$ 4
US Treasury [Member]
Schedule of Available-for-Sale Securities [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	684,242
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	9,602
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	0
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	0
Available for Sale, Total Estimated Fair Value	684,242
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	9,602	0
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	2,219,261
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	23,625
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	45,963
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	1,464
Available for Sale, Total Estimated Fair Value	2,265,224
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	25,089	4
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	364,056
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	5,074
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	5,675
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	300
Available for Sale, Total Estimated Fair Value	369,731
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	$ 5,374	$ 0

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, 2021	Dec. 31, 2020
Schedule of Available-for-Sale Securities [Line Items]
Held to Maturity, Due in one year or less, Amortized Cost	$ 465,649
Held to Maturity, Due after one year through five years, Amortized Cost	180,373
Held to Maturity, Due after five years through ten years, Amortized Cost	588,908
Held to Maturity, Due after ten years, Amortized Cost	514,407
Held to Maturity, Amortized Cost	1,749,337	$ 1,945,833
Held to Maturity, Due in one year or less, Estimated Fair Value	470,222
Held to Maturity, Due after one year through five years, Estimated Fair Value	185,458
Held to Maturity, Due after five years through ten years, Estimated Fair Value	608,183
Held to Maturity, Due after ten years, Estimated Fair Value	545,280
Held to Maturity, Estimated Fair Value	1,809,143	2,052,896
Available for Sale, Due in one year or less, Amortized Cost	86,548
Available for Sale, Due after one year through five years, Amortized Cost	2,656,909
Available for Sale, Due after five years through ten years, Amortized Cost	1,770,915
Available for Sale, Due after ten years, Amortized Cost	8,889,157
Debt Securities, Available-for-sale, Amortized Cost, Total	13,445,888	9,727,401
Available for Sale, Due in one year or less, Estimated Fair Value	87,557
Available for Sale, Due after one year through five years, Estimated Fair Value	2,769,753
Available for Sale, Due after five years through ten years, Estimated Fair Value	1,820,222
Available for Sale, Due after ten years, Estimated Fair Value	9,204,737
Debt Securities, Available-for-sale	13,924,628	10,437,565
Residential Mortgage Backed Securities [Member]
Schedule of Available-for-Sale Securities [Line Items]
Held to Maturity, Due in one year or less, Amortized Cost	37
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	515,100
Held to Maturity, Due after ten years, Amortized Cost	12,127
Held to Maturity, Amortized Cost	527,264	528,784
Held to Maturity, Due in one year or less, Estimated Fair Value	37
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	533,454
Held to Maturity, Due after ten years, Estimated Fair Value	12,539
Held to Maturity, Estimated Fair Value	546,030	570,526
Available for Sale, Due in one year or less, Amortized Cost	63
Available for Sale, Due after one year through five years, Amortized Cost	15,278
Available for Sale, Due after five years through ten years, Amortized Cost	19,175
Available for Sale, Due after ten years, Amortized Cost	4,025,176
Debt Securities, Available-for-sale, Amortized Cost, Total	4,059,692	1,916,581
Available for Sale, Due in one year or less, Estimated Fair Value	64
Available for Sale, Due after one year through five years, Estimated Fair Value	15,954
Available for Sale, Due after five years through ten years, Estimated Fair Value	19,624
Available for Sale, Due after ten years, Estimated Fair Value	4,030,623
Debt Securities, Available-for-sale	4,066,265	1,987,679
States and Political Subdivisions [Member]
Schedule of Available-for-Sale Securities [Line Items]
Held to Maturity, Due in one year or less, Amortized Cost	464,112
Held to Maturity, Due after one year through five years, Amortized Cost	180,373
Held to Maturity, Due after five years through ten years, Amortized Cost	73,808
Held to Maturity, Due after ten years, Amortized Cost	502,280
Held to Maturity, Amortized Cost	1,220,573	1,415,549
Held to Maturity, Due in one year or less, Estimated Fair Value	468,685
Held to Maturity, Due after one year through five years, Estimated Fair Value	185,458
Held to Maturity, Due after five years through ten years, Estimated Fair Value	74,729
Held to Maturity, Due after ten years, Estimated Fair Value	532,741
Held to Maturity, Estimated Fair Value	1,261,613	1,480,870
Available for Sale, Due in one year or less, Amortized Cost	86,485
Available for Sale, Due after one year through five years, Amortized Cost	1,611,040
Available for Sale, Due after five years through ten years, Amortized Cost	808,323
Available for Sale, Due after ten years, Amortized Cost	4,672,287
Debt Securities, Available-for-sale, Amortized Cost, Total	7,178,135	6,683,927
Available for Sale, Due in one year or less, Estimated Fair Value	87,493
Available for Sale, Due after one year through five years, Estimated Fair Value	1,715,065
Available for Sale, Due after five years through ten years, Estimated Fair Value	858,485
Available for Sale, Due after ten years, Estimated Fair Value	4,975,528
Debt Securities, Available-for-sale	7,636,571	7,287,902
Other [Member]
Schedule of Available-for-Sale Securities [Line Items]
Held to Maturity, Due in one year or less, Amortized Cost	1,500
Held to Maturity, Due after one year through five years, Amortized Cost	0
Held to Maturity, Due after five years through ten years, Amortized Cost	0
Held to Maturity, Due after ten years, Amortized Cost	0
Held to Maturity, Amortized Cost	1,500	1,500
Held to Maturity, Due in one year or less, Estimated Fair Value	1,500
Held to Maturity, Due after one year through five years, Estimated Fair Value	0
Held to Maturity, Due after five years through ten years, Estimated Fair Value	0
Held to Maturity, Due after ten years, Estimated Fair Value	0
Held to Maturity, Estimated Fair Value	1,500	1,500
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, Total	42,359	42,351
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	42,359	42,351
US Treasury [Member]
Schedule of Available-for-Sale Securities [Line Items]
Available for Sale, Due in one year or less, Amortized Cost	0
Available for Sale, Due after one year through five years, Amortized Cost	1,030,591
Available for Sale, Due after five years through ten years, Amortized Cost	943,417
Available for Sale, Due after ten years, Amortized Cost	191,694
Debt Securities, Available-for-sale, Amortized Cost, Total	2,165,702	1,084,542
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	1,038,734
Available for Sale, Due after five years through ten years, Estimated Fair Value	942,113
Available for Sale, Due after ten years, Estimated Fair Value	198,586
Debt Securities, Available-for-sale	$ 2,179,433	$ 1,119,633

Securities (Sales of Securities

Securities (Sales of Securities Available for Sale) (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Investments, Debt and Equity Securities [Abstract]
Proceeds from sales	$ 1,999,891	$ 1,162,352	$ 18,660,147
Gross realized gains	69	108,989	930
Gross realized losses	0	0	(637)
Tax benefit (expense) related to securities gains/losses	$ (14)	$ (22,888)	$ (62)

Securities Securities - (Premiu

Securities Securities - (Premium Amortization and Discount Accretion Included in Income on Securities) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Investments, Debt and Equity Securities [Abstract]
Premium amortization	$ (121,994)	$ (126,210)	$ (120,785)
Discount accretion	2,752	2,425	5,227
Net (premium amortization) discount accretion	$ (119,242)	$ (123,785)	$ (115,558)

Securities (Year End Trading Ac

Securities (Year End Trading Account Securities at Estimated Fair Value) (Detail) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Debt and Equity Securities, FV-NI [Line Items]
Trading account securities	$ 25,162	$ 24,456
US Treasury [Member]
Debt and Equity Securities, FV-NI [Line Items]
Trading account securities	24,237	23,996
States and Political Subdivisions [Member]
Debt and Equity Securities, FV-NI [Line Items]
Trading account securities	$ 925	$ 460

Securities (Net Gains and Losse

Securities (Net Gains and Losses on Trading Account Securities) (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Investments, Debt and Equity Securities [Abstract]
Net gain on sales transactions	$ 1,014	$ 1,102	$ 2,173
Net mark-to-market gains (losses)	(75)	85	(176)
Net gain on trading account securities	$ 939	$ 1,187	$ 1,997

Loans (Narrative) (Detail)

Loans (Narrative) (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2021USD ($)Grade	Dec. 31, 2020USD ($)Grade	Dec. 31, 2019USD ($)	Dec. 31, 2018USD ($)
Accounts, Notes, Loans and Financing Receivable [Line Items]
Concentration of loans in a single industry in excess of ten percent	0.00%	0.00%
Maximum percentage loan related to single industry	10.00%	10.00%
U.S. dollar denominated loans and commitments to borrowers in Mexico	$ 0	$ 0
Commercial and industrial loans related to overdraft for correspondent bank customer	$ 7,800	$ 5,600
Financing Receivable, Threshold Period Past Due	90 days
Number of days past due for payment of interest on loans, minimum	120 days
Texas Leading Index economic condition indicator	134.7	118.1
Financing Receivable, Allowance for Credit Loss	$ 248,666	$ 263,177
Loans Receivable [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accrued interest receivable	$ 40,000	$ 48,700
Commercial and Industrial Total Energy Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Percentage of total energy loans to total loans	6.60%	7.10%
Percentage of total energy loans to total loans excluding PPP Loans	6.80%	8.20%
Weighted Average Risk Grade | Grade	6.06	6.85
Financing Receivable, Allowance for Credit Loss	$ 17,217	$ 39,553	$ 37,382	$ 29,052
Commercial and Industrial Total Energy Loans [Member] | Risk Grade One To Eight [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade | Grade	5.78	5.99
Non Accrual Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Additional interest that would have been recognized on non-accrual loans, net of tax	$ 1,800	$ 2,900	3,900
Grade 12 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
General percentage of valuation allowance in excess of principal balance, maximum	30.00%
Grade 13 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
General percentage of valuation allowance in excess of principal balance, minimum	30.00%
Commercial Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade | Grade	6.22	6.45
Financing Receivable, Allowance for Credit Loss	$ 72,091	$ 73,843	51,593	48,580
Commercial Portfolio Segment [Member] | Risk Grade One To Eight [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade | Grade	6.01	6.13
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]
Weighted Average Risk Grade | Grade	7.19	7.32
Financing Receivable, Allowance for Credit Loss	$ 144,936	$ 134,892	31,037	38,777
Commercial Real Estate Buildings Land And Other Financing Receivable [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade | Grade	7.22	7.34
Commercial Real Estate Buildings Land And Other Financing Receivable [Member] | Risk Grade One To Eight [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade | Grade	6.91	6.97
Construction Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade | Grade	7.06	7.22
Construction Loans [Member] | Risk Grade One To Eight [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade | Grade	6.99	6.99
Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Allowance for Credit Loss	$ 7,837	$ 6,963	$ 8,042	$ 9,620
Paycheck Protection Program [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Allowance for Credit Loss	0
Commitments to Extend Credit [Member] | Commercial and Industrial Total Energy Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unfunded balances	891,400
Standby Letters of Credit [Member] | Commercial and Industrial Total Energy Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unfunded balances	$ 68,900

Loans (Loans) (Detail)

Loans (Loans) (Detail) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	$ 16,336,397	$ 17,481,309
Commercial Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	5,364,954	4,955,341
Energy Production [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	878,436	976,473
Energy Service [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	105,901	116,825
Energy Other [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	93,455	141,900
Commercial and Industrial Total Energy Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	1,077,792	1,235,198
Paycheck Protection Program [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	428,882	2,433,849
Commercial mortgage [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	5,867,062	5,478,806
Construction Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	1,304,271	1,223,814
Commercial land loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	405,277	317,847
Commercial Real Estate Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	7,576,610	7,020,467
Home Equity Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	324,157	329,390
Home Equity Line of Credit [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	519,098	452,854
Other consumer real estate loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	567,535	548,530
Total consumer real estate loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	1,410,790	1,330,774
Real Estate Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	8,987,400	8,351,241
Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	$ 477,369	$ 505,680

Loans (Activities in Related Pa

Loans (Activities in Related Party Loans) (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2021USD ($)
Receivables [Abstract]
Balance outstanding at December 31, 2020	$ 353,105
Principal additions	262,761
Principal payments	(196,634)
Other changes	(68,694)
Balance outstanding at December 31, 2021	$ 350,538

Loans (Non-Accrual Loans, Segre

Loans (Non-Accrual Loans, Segregated by Class of Loans) (Detail) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Non Accrual Loans Segregated By Class Of Loans [Line Items]
Non-accrual loans	$ 53,713	$ 61,449
Financing Receivable, Nonaccrual, No Allowance	27,202	21,911
Commercial Portfolio Segment [Member]
Non Accrual Loans Segregated By Class Of Loans [Line Items]
Non-accrual loans	22,582	19,849
Financing Receivable, Nonaccrual, No Allowance	4,701	4,479
Commercial and Industrial Total Energy Loans [Member]
Non Accrual Loans Segregated By Class Of Loans [Line Items]
Non-accrual loans	14,433	23,168
Financing Receivable, Nonaccrual, No Allowance	8,533	639
Paycheck Protection Program [Member]
Non Accrual Loans Segregated By Class Of Loans [Line Items]
Non-accrual loans	0	0
Financing Receivable, Nonaccrual, No Allowance	0	0
Commercial Real Estate, Buildings, Land and Other [Member]
Non Accrual Loans Segregated By Class Of Loans [Line Items]
Non-accrual loans	15,297	15,737
Financing Receivable, Nonaccrual, No Allowance	13,817	14,116
Construction Loans [Member]
Non Accrual Loans Segregated By Class Of Loans [Line Items]
Non-accrual loans	948	1,684
Financing Receivable, Nonaccrual, No Allowance	0	1,684
Total consumer real estate loans [Member]
Non Accrual Loans Segregated By Class Of Loans [Line Items]
Non-accrual loans	440	993
Financing Receivable, Nonaccrual, No Allowance	138	993
Consumer Loan [Member]
Non Accrual Loans Segregated By Class Of Loans [Line Items]
Non-accrual loans	13	18
Financing Receivable, Nonaccrual, No Allowance	$ 13	$ 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, 2021	Dec. 31, 2020
Loans and Leases Receivable Disclosure [Line Items]
Non-accrual loans	$ 53,713	$ 61,449
Commercial Portfolio Segment [Member]
Loans and Leases Receivable Disclosure [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	1,630,524	1,397,141
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	693,324	608,464
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	392,408	343,825
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	214,163	258,737
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	150,922	121,652
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	143,292	119,250
Financing Receivable, Revolving	2,075,632	2,019,121
Non-accrual loans	22,582	19,849
Commercial and Industrial Total Energy Loans [Member]
Loans and Leases Receivable Disclosure [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	475,023	524,270
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	9,539	48,853
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	20,991	16,310
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	9,480	8,083
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	3,110	2,174
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	5,638	5,346
Financing Receivable, Revolving	483,020	592,094
Non-accrual loans	14,433	23,168
Paycheck Protection Program [Member]
Loans and Leases Receivable Disclosure [Line Items]
Non-accrual loans	0	0
Commercial Real Estate, Buildings, Land and Other [Member]
Loans and Leases Receivable Disclosure [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	1,761,554	1,629,815
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	1,257,055	1,086,073
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	1,008,366	883,701
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	632,020	764,197
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	612,767	495,617
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	825,249	804,894
Financing Receivable, Revolving	59,595	74,403
Non-accrual loans	15,297	15,737
Construction Loans [Member]
Loans and Leases Receivable Disclosure [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	693,192	420,477
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	268,080	452,644
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	178,226	196,170
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	2,339	2,915
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	484	1,144
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	1,930	1,758
Financing Receivable, Revolving	160,020	147,575
Non-accrual loans	948	1,684
Total consumer real estate loans [Member]
Loans and Leases Receivable Disclosure [Line Items]
Non-accrual loans	440	993
Consumer Loan [Member]
Loans and Leases Receivable Disclosure [Line Items]
Non-accrual loans	13	18
Nonperforming Financial Instruments [Member]
Loans and Leases Receivable Disclosure [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	6,687	16,498
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	5,111	15,154
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	13,851	4,989
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	3,959	3,719
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	2,795	2,038
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	3,423	3,532
Financing Receivable, Revolving	11,566	12,414
Financing Receivable, Revolving, Converted to Term Loan	6,321	3,105
Nonperforming Financial Instruments [Member] | Commercial Portfolio Segment [Member]
Loans and Leases Receivable Disclosure [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	636	9,479
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	3,856	3,351
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	5,047	1,846
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	1,820	1,489
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	765	105
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	353	29
Financing Receivable, Revolving	4,635	839
Financing Receivable, Revolving, Converted to Term Loan	5,470	2,711
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	0	2,421
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	0	6,772
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	5,358	2,144
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	1,325	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	359
Financing Receivable, Revolving	6,931	11,193
Financing Receivable, Revolving, Converted to Term Loan	819	279
Nonperforming Financial Instruments [Member] | Paycheck Protection Program [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] | Commercial Real Estate, Buildings, Land and Other [Member]
Loans and Leases Receivable Disclosure [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	6,038	2,914
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	307	5,031
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	3,446	999
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	814	2,019
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	2,030	1,933
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	2,662	2,736
Financing Receivable, Revolving	0	105
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	1,684
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	948	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	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	211
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	0	0
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	408	408
Financing Receivable, Revolving	0	259
Financing Receivable, Revolving, Converted to Term Loan	32	115
Nonperforming Financial Instruments [Member] | Consumer Loan [Member]
Loans and Leases Receivable Disclosure [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	13	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	18
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, 2021	Dec. 31, 2020
Financing Receivable, Past Due [Line Items]
Total loans	$ 16,336,397	$ 17,481,309
Accruing Loans 90 or More Days Past Due	38,723
Commercial Portfolio Segment [Member]
Financing Receivable, Past Due [Line Items]
Total loans	5,364,954	4,955,341
Accruing Loans 90 or More Days Past Due	7,802
Commercial and Industrial Total Energy Loans [Member]
Financing Receivable, Past Due [Line Items]
Total loans	1,077,792	1,235,198
Accruing Loans 90 or More Days Past Due	215
Paycheck Protection Program [Member]
Financing Receivable, Past Due [Line Items]
Total loans	428,882	2,433,849
Accruing Loans 90 or More Days Past Due	18,766
Commercial Real Estate, Buildings, Land and Other [Member]
Financing Receivable, Past Due [Line Items]
Total loans	6,272,339	5,796,653
Accruing Loans 90 or More Days Past Due	8,687
Construction Loans [Member]
Financing Receivable, Past Due [Line Items]
Total loans	1,304,271	1,223,814
Accruing Loans 90 or More Days Past Due	0
Total consumer real estate loans [Member]
Financing Receivable, Past Due [Line Items]
Total loans	1,410,790	1,330,774
Accruing Loans 90 or More Days Past Due	2,177
Consumer Loan [Member]
Financing Receivable, Past Due [Line Items]
Total loans	477,369	505,680
Accruing Loans 90 or More Days Past Due	1,076
Financing Receivables, 30 to 89 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	87,675
Financing Receivables, 30 to 89 Days Past Due [Member] | Commercial Portfolio Segment [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	34,096
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	1,451
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	4,979
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	37,899
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	188
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	4,877	8,090
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	4,185	5,537
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	56,722
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	12,364
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	7,867
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	18,766
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	14,136
Financial Asset, Equal to or Greater than 90 Days Past Due [Member] | Construction Loans [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	0
Financial Asset, Equal to or Greater than 90 Days Past Due [Member] | Total consumer real estate loans [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	2,513	3,047
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	1,076	1,251
Financial Asset, Past Due
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	144,397
Financial Asset, Past Due | Commercial Portfolio Segment [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	46,460
Financial Asset, Past Due | Commercial and Industrial Total Energy Loans [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	9,318
Financial Asset, Past Due | Paycheck Protection Program [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	23,745
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	52,035
Financial Asset, Past Due | Construction Loans [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	188
Financial Asset, Past Due | Total consumer real estate loans [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	7,390	11,137
Financial Asset, Past Due | Consumer Loan [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	5,261	6,788
Financial Asset, Not Past Due
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	16,192,000
Financial Asset, Not Past Due | Commercial Portfolio Segment [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	5,318,494
Financial Asset, Not Past Due | Commercial and Industrial Total Energy Loans [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	1,068,474
Financial Asset, Not Past Due | Paycheck Protection Program [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	405,137
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	6,220,304
Financial Asset, Not Past Due | Construction Loans [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	1,304,083
Financial Asset, Not Past Due | Total consumer real estate loans [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	1,403,400	1,319,637
Financial Asset, Not Past Due | Consumer Loan [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	$ 472,108	$ 498,892

Loans (Troubled Debt Restructur

Loans (Troubled Debt Restructurings) (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Financing Receivable, Troubled Debt Restructuring [Line Items]
Balance at Restructure	$ 7,017	$ 17,524	$ 13,426
Balance at Year-end	3,745	8,552	11,674
Commercial Portfolio Segment [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Balance at Restructure	1,312	3,661	3,845
Balance at Year-end	1,162	192	2,161
Commercial and Industrial Total Energy Loans [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Balance at Restructure	3,817	2,432	0
Balance at Year-end	721	2,421	0
Commercial Real Estate, Buildings, Land and Other [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Balance at Restructure	1,888	9,310	9,457
Balance at Year-end	1,862	4,922	9,393
Construction Loans [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Balance at Restructure	0	1,017	0
Balance at Year-end	0	1,017	0
Total consumer real estate loans [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Balance at Restructure	0	0	124
Balance at Year-end	0	0	120
Consumer Loan [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Balance at Restructure	0	1,104	0
Balance at Year-end	$ 0	$ 0	$ 0

Loans Loans (Restructured Loans

Loans Loans (Restructured Loans Past Due in Excess of 90 Days) (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2021USD ($)Item	Dec. 31, 2020USD ($)Item	Dec. 31, 2019USD ($)Item
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number Of restructured loans past due in excess of 90 days at period-end | Item	2	1	4
Dollar amount of loans previously restructured during the last year in excess of 90 days past due	$ 1,027	$ 2,008	$ 3,340
Restructured loans on non-accrual status at period end	3,439	8,552	5,576
Chare-offs of restrucured loans recognized in connection with restructuring	0	337	0
Charge-offs of restructured loans recognized on previously restructured loans	$ 4,278	$ 3,894	$ 1,500

Loans (Weighted Average Risk Gr

Loans (Weighted Average Risk Grades for All Commercial Loans by Class) (Detail) $ in Thousands	Dec. 31, 2021USD ($)Grade	Dec. 31, 2020USD ($)Grade
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	$ 16,336,397	$ 17,481,309
Commercial Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	1,630,524	1,397,141
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	693,324	608,464
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	392,408	343,825
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	214,163	258,737
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	150,922	121,652
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	143,292	119,250
Financing Receivable, Revolving	2,075,632	2,019,121
Loans, net of unearned discounts	$ 5,364,954	$ 4,955,341
Weighted Average Risk Grade | Grade	6.22	6.45
Commercial Portfolio Segment [Member] | Revolving Credit Facility
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade | Grade	6.21	6.38
Commercial Portfolio Segment [Member] | Revolving Loans Converted to Term
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Revolving, Converted to Term Loan	$ 64,689	$ 87,151
Weighted Average Risk Grade | Grade	8.04	7.51
Commercial Portfolio Segment [Member] | 2021
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade | Grade	5.91
Commercial Portfolio Segment [Member] | 2020
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade | Grade	6.30	6.19
Commercial Portfolio Segment [Member] | 2019
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade | Grade	6.89	6.88
Commercial Portfolio Segment [Member] | 2018
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade | Grade	7.06	7.22
Commercial Portfolio Segment [Member] | 2017
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade | Grade	5.91	6.39
Commercial Portfolio Segment [Member] | 2016
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade | Grade		6.32
Commercial Portfolio Segment [Member] | Prior Years
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade | Grade	5.80	5.84
Commercial and Industrial Total Energy Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	$ 475,023	$ 524,270
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	9,539	48,853
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	20,991	16,310
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	9,480	8,083
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	3,110	2,174
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	5,638	5,346
Financing Receivable, Revolving	483,020	592,094
Loans, net of unearned discounts	$ 1,077,792	$ 1,235,198
Weighted Average Risk Grade | Grade	6.06	6.85
Commercial and Industrial Total Energy Loans [Member] | Revolving Credit Facility
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade | Grade	5.61	6.45
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	$ 70,991	$ 38,068
Weighted Average Risk Grade | Grade	6.46	8.20
Commercial and Industrial Total Energy Loans [Member] | 2021
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade | Grade	6.21
Commercial and Industrial Total Energy Loans [Member] | 2020
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade | Grade	7.81	6.86
Commercial and Industrial Total Energy Loans [Member] | 2019
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade | Grade	9.34	9.57
Commercial and Industrial Total Energy Loans [Member] | 2018
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade | Grade	8.60	8.68
Commercial and Industrial Total Energy Loans [Member] | 2017
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade | Grade	7.12	7.40
Commercial and Industrial Total Energy Loans [Member] | 2016
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade | Grade		7.85
Commercial and Industrial Total Energy Loans [Member] | Prior Years
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade | Grade	7.63	8.06
Commercial Real Estate, Buildings, Land and Other [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	$ 1,761,554	$ 1,629,815
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	1,257,055	1,086,073
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	1,008,366	883,701
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	632,020	764,197
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	612,767	495,617
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	825,249	804,894
Financing Receivable, Revolving	59,595	74,403
Loans, net of unearned discounts	$ 6,272,339	$ 5,796,653
Weighted Average Risk Grade | Grade	7.22	7.34
Commercial Real Estate, Buildings, Land and Other [Member] | Revolving Credit Facility
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade | Grade	7.06	7.54
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	$ 115,733	$ 57,953
Weighted Average Risk Grade | Grade	7.02	7.12
Commercial Real Estate, Buildings, Land and Other [Member] | 2021
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade | Grade	7.19
Commercial Real Estate, Buildings, Land and Other [Member] | 2020
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade | Grade	7.18	7.13
Commercial Real Estate, Buildings, Land and Other [Member] | 2019
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade | Grade	7.35	7.36
Commercial Real Estate, Buildings, Land and Other [Member] | 2018
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade | Grade	7.39	7.54
Commercial Real Estate, Buildings, Land and Other [Member] | 2017
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade | Grade	7.34	7.55
Commercial Real Estate, Buildings, Land and Other [Member] | 2016
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade | Grade		7.54
Commercial Real Estate, Buildings, Land and Other [Member] | Prior Years
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade | Grade	7.01	7.20
Construction Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	$ 693,192	$ 420,477
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	268,080	452,644
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	178,226	196,170
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	2,339	2,915
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	484	1,144
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	1,930	1,758
Financing Receivable, Revolving	160,020	147,575
Loans, net of unearned discounts	$ 1,304,271	$ 1,223,814
Weighted Average Risk Grade | Grade	7.06	7.22
Construction Loans [Member] | Revolving Credit Facility
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade | Grade	6.79	7.29
Construction Loans [Member] | Revolving Loans Converted to Term
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Revolving, Converted to Term Loan	$ 0	$ 1,131
Weighted Average Risk Grade | Grade	0	9
Construction Loans [Member] | 2021
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade | Grade	7.17
Construction Loans [Member] | 2020
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade | Grade	6.56	6.82
Construction Loans [Member] | 2019
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade | Grade	7.60	7.18
Construction Loans [Member] | 2018
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade | Grade	7.51	8.08
Construction Loans [Member] | 2017
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade | Grade	8.92	8.95
Construction Loans [Member] | 2016
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade | Grade		7.30
Construction Loans [Member] | Prior Years
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade | Grade	6.73	6.44
Commercial Real Estate Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	$ 2,454,746	$ 2,050,292
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	1,525,135	1,538,717
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	1,186,592	1,079,871
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	634,359	767,112
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	613,251	496,761
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	827,179	806,652
Financing Receivable, Revolving	219,615	221,978
Loans, net of unearned discounts	$ 7,576,610	$ 7,020,467
Weighted Average Risk Grade | Grade	7.19	7.32
Commercial Real Estate Portfolio Segment [Member] | Revolving Credit Facility
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade | Grade	6.86	7.37
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	$ 115,733	$ 59,084
Weighted Average Risk Grade | Grade	7.02	7.15
Commercial Real Estate Portfolio Segment [Member] | 2021
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade | Grade	7.18
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	7.39	7.31
Commercial Real Estate Portfolio Segment [Member] | 2018
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade | Grade	7.39	7.64
Commercial Real Estate Portfolio Segment [Member] | 2017
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade | Grade	7.34	7.56
Commercial Real Estate Portfolio Segment [Member] | 2016
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade | Grade		7.54
Commercial Real Estate Portfolio Segment [Member] | Prior Years
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade | Grade	7	7.20
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	$ 1,567,883	$ 1,300,844
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	657,529	552,885
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	350,563	290,088
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	179,209	226,232
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	146,064	107,063
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	131,201	113,458
Financing Receivable, Revolving	1,987,061	1,852,341
Loans, net of unearned discounts	$ 5,063,847	$ 4,506,121
Weighted Average Risk Grade | Grade	6.01	6.13
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	$ 44,337	$ 63,210
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	445,489	403,156
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	8,075	18,911
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	9,259	9,759
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	6,441	8,083
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	3,110	1,415
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	4,368	4,326
Financing Receivable, Revolving	464,454	494,946
Loans, net of unearned discounts	$ 1,008,370	$ 968,144
Weighted Average Risk Grade | Grade	5.78	5.99
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	$ 67,174	$ 27,548
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	1,707,550	1,544,558
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	1,096,274	947,102
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	874,130	749,879
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	533,362	605,152
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	492,492	432,941
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	713,268	661,301
Financing Receivable, Revolving	52,150	56,600
Loans, net of unearned discounts	$ 5,574,922	$ 5,047,873
Weighted Average Risk Grade | Grade	6.91	6.97
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	$ 105,696	$ 50,340
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	657,471	374,661
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	262,176	436,077
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	178,226	168,517
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	2,339	67
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	38	1,144
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	1,930	1,758
Financing Receivable, Revolving	160,020	127,801
Loans, net of unearned discounts	$ 1,262,200	$ 1,110,025
Weighted Average Risk Grade | Grade	6.99	6.99
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	$ 0
Risk Grade Nine [Member] | Commercial Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	32,866	50,785
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	21,094	37,865
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	24,683	33,961
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	26,327	20,851
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	612	12,348
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	11,419	5,510
Financing Receivable, Revolving	65,131	85,756
Loans, net of unearned discounts	187,870	256,198
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	5,738	9,122
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	19,274	105,772
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	611	2,272
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	1,775	1,743
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	187	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	724	0
Financing Receivable, Revolving	11,635	18,194
Loans, net of unearned discounts	36,622	133,547
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	2,416	5,566
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	16,302	45,527
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	145,340	81,224
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	52,427	75,893
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	43,806	45,485
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	27,188	26,745
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	27,767	37,728
Financing Receivable, Revolving	4,445	10,521
Loans, net of unearned discounts	321,533	325,227
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	4,258	2,104
Risk Grade Nine [Member] | Construction Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	35,721	37,430
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	4,956	16,567
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	2,848
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	446	0
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	0	0
Financing Receivable, Revolving	0	14,311
Loans, net of unearned discounts	41,123	72,287
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	1,131
Risk Grade Ten [Member] | Commercial Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	27,961	31,333
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	6,273	7,361
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	4,047	11,379
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	4,357	6,749
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	1,021	710
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	98	113
Financing Receivable, Revolving	14,091	65,180
Loans, net of unearned discounts	59,137	125,977
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	1,289	3,152
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	703
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	101	4,049
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	631	1,339
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	511	0
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	0	759
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	0	0
Financing Receivable, Revolving	0	37,637
Loans, net of unearned discounts	1,773	46,427
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	530	1,940
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	28,209	14,183
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	13,813	36,414
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	69,643	45,014
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	46,250	71,814
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	64,950	25,343
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	46,582	60,225
Financing Receivable, Revolving	0	200
Loans, net of unearned discounts	269,447	258,454
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	5,261
Risk Grade Ten [Member] | Construction Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	0	5,846
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	27,653
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	5,463
Loans, net of unearned discounts	0	38,962
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	1,178	4,700
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	4,572	7,002
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	8,068	6,551
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	2,450	3,416
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	2,460	1,426
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	221	140
Financing Receivable, Revolving	4,714	15,005
Loans, net of unearned discounts	31,518	47,196
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	7,855	8,956
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	10,260	12,218
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	752	16,849
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	3,968	1,325
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	1,016	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	546	661
Financing Receivable, Revolving	0	30,124
Loans, net of unearned discounts	16,594	63,912
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	52	2,735
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	3,455	22,633
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	1,321	16,302
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	8,720	11,916
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	7,788	39,727
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	26,107	8,655
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	34,970	42,904
Financing Receivable, Revolving	3,000	6,977
Loans, net of unearned discounts	91,140	149,362
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	5,779	248
Risk Grade Eleven [Member] | Construction Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	0	856
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	856
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	456	6,899
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	2,495	2,399
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	3,828	1,195
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	1,756	1,005
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	347	105
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	353	29
Financing Receivable, Revolving	613	480
Loans, net of unearned discounts	12,535	14,528
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	2,687	2,416
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	0	1,101
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	0	4,580
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	3,888	654
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	246	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	359
Financing Receivable, Revolving	4,000	6,768
Loans, net of unearned discounts	8,953	13,741
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	819	279
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	5,838	2,714
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	307	5,031
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	3,446	999
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	814	2,019
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	2,030	1,683
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	2,662	2,736
Financing Receivable, Revolving	0	42
Loans, net of unearned discounts	15,097	15,224
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	1,684
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	748	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	748	1,684
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	180	2,580
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	1,361	952
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	1,219	651
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	64	484
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	418	0
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	0	0
Financing Receivable, Revolving	4,022	359
Loans, net of unearned discounts	10,047	5,321
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	2,783	295
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	1,320
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	0	2,192
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	1,470	1,490
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	1,079	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	2,931	4,425
Loans, net of unearned discounts	5,480	9,427
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	0
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	200	200
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	250
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	0	0
Financing Receivable, Revolving	0	63
Loans, net of unearned discounts	200	513
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	200	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	200	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, 2021	Dec. 31, 2020
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	$ 16,336,397	$ 17,481,309
Financing Receivables, 30 to 89 Days Past Due [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	87,675
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	56,722
Financial Asset, Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	144,397
Financial Asset, Not Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	16,192,000
Total consumer real estate loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	1,410,790	1,330,774
Total consumer real estate loans [Member] | Revolving Credit Facility
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	506,450	436,206
Total consumer real estate loans [Member] | Revolving Loans Converted to Term
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	12,725	16,786
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	4,877	8,090
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	126	652
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	1,732	531
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	2,513	3,047
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	991	615
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	185	151
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	7,390	11,137
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	1,117	1,267
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	1,917	682
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	1,403,400	1,319,637
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	505,333	434,939
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	10,808	16,104
Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	477,369	505,680
Consumer Loan [Member] | Revolving Credit Facility
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	372,225	390,060
Consumer Loan [Member] | Revolving Loans Converted to Term
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	26,318	29,277
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	4,185	5,537
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	325	2,238
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	1,943	727
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	1,076	1,251
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	34	1,031
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	449	21
Consumer Loan [Member] | Financial Asset, Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	5,261	6,788
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	359	3,269
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	2,392	748
Consumer Loan [Member] | Financial Asset, Not Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	472,108	498,892
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	371,866	386,791
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	23,926	28,529
2021 | Total consumer real estate loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	319,322
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	280
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	0
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	280
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	319,042
2021 | Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	48,856
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	1,600
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	548
2021 | Consumer Loan [Member] | Financial Asset, Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	2,148
2021 | Consumer Loan [Member] | Financial Asset, Not Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	46,708
2020 | Total consumer real estate loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	251,364	336,681
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	204	225
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	0	15
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	204	240
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	251,160	336,441
2020 | Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	17,934	47,107
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	91	1,750
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	71
2020 | Consumer Loan [Member] | Financial Asset, Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	91	1,821
2020 | Consumer Loan [Member] | Financial Asset, Not Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	17,843	45,286
2019 | Total consumer real estate loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	96,306	167,500
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	406	1,038
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	139
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	406	1,177
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	95,900	166,323
2019 | Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	6,380	28,123
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	120	300
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	45	10
2019 | Consumer Loan [Member] | Financial Asset, Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	165	310
2019 | Consumer Loan [Member] | Financial Asset, Not Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	6,215	27,813
2018 | Total consumer real estate loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	56,536	96,039
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	489	1,556
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	154	109
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	643	1,665
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	55,893	94,374
2018 | Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	2,722	5,968
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	38	453
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	118
2018 | Consumer Loan [Member] | Financial Asset, Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	38	571
2018 | Consumer Loan [Member] | Financial Asset, Not Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	2,684	5,397
2017 | Total consumer real estate loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	49,492	81,884
2017 | 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	296	553
2017 | 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	355	706
2017 | 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	651	1,259
2017 | 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	48,841	80,625
2017 | Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	1,759	2,851
2017 | 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	51	52
2017 | 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
2017 | Consumer Loan [Member] | Financial Asset, Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	51	52
2017 | Consumer Loan [Member] | Financial Asset, Not Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	1,708	2,799
2016 | Total consumer real estate loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts		66,894
2016 | 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		628
2016 | 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		25
2016 | 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		653
2016 | 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		66,241
2016 | Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts		1,722
2016 | 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		17
2016 | 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
2016 | Consumer Loan [Member] | Financial Asset, Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss		17
2016 | Consumer Loan [Member] | Financial Asset, Not Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss		1,705
Prior Years | Total consumer real estate loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	118,595	128,784
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	1,344	2,907
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	828	1,287
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	2,172	4,194
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	116,423	124,590
Prior Years | Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	1,175	572
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	17	0
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	17	0
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	$ 1,158	$ 572

Loans (Revolving Loans Converte

Loans (Revolving Loans Converted to Term) (Details) - Revolving Loans Converted to Term - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Accounts, Notes, Loans and Financing Receivable [Line Items]
Remaining Revolving Loans Converted to Term During Period	$ 172,955	$ 111,007
Commercial Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Remaining Revolving Loans Converted to Term During Period	40,099	47,562
Commercial and Industrial Total Energy Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Remaining Revolving Loans Converted to Term During Period	54,996	33,150
Commercial Real Estate, Buildings, Land and Other [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Remaining Revolving Loans Converted to Term During Period	68,337	10,505
Construction Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Remaining Revolving Loans Converted to Term During Period	0	1,131
Total consumer real estate loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Remaining Revolving Loans Converted to Term During Period	1,156	2,264
Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Remaining Revolving Loans Converted to Term During Period	$ 8,367	$ 16,395

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, 2021	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, Allowance for Credit Loss	$ 248,666	$ 263,177
Commercial Portfolio Segment [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, Allowance for Credit Loss	72,091	73,843	$ 51,593	$ 48,580
Commercial and Industrial Total Energy Loans [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, Allowance for Credit Loss	17,217	39,553	37,382	29,052
Commercial Real Estate Portfolio Segment [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, Allowance for Credit Loss	144,936	134,892	31,037	38,777
Total consumer real estate loans [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, Allowance for Credit Loss	6,585	7,926	4,113	6,103
Consumer Loan [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, Allowance for Credit Loss	7,837	6,963	8,042	9,620
Loans Receivable [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, Allowance for Credit Loss	248,666	263,177	$ 132,167	$ 132,132
Modeled Expected Credit Losses [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, Allowance for Credit Loss	82,866	214,552
Modeled Expected Credit Losses [Member] | Commercial Portfolio Segment [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, Allowance for Credit Loss	46,946	65,645
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	6,363	8,910
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	16,676	125,126
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	6,484	7,926
Modeled Expected Credit Losses [Member] | Consumer Loan [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, Allowance for Credit Loss	6,397	6,945
Q-factor adjustments [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, Allowance for Credit Loss	149,348	33,346
Q-factor adjustments [Member] | Commercial Portfolio Segment [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, Allowance for Credit Loss	14,609	2,877
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	5,374	21,216
Q-factor adjustments [Member] | Commercial Real Estate Portfolio Segment [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, Allowance for Credit Loss	127,860	9,253
Q-factor adjustments [Member] | Total consumer real estate loans [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, Allowance for Credit Loss	65	0
Q-factor adjustments [Member] | Consumer Loan [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, Allowance for Credit Loss	1,440	0
Specific Valuation Allowances [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, Allowance for Credit Loss	16,452	15,279
Specific Valuation Allowances [Member] | Commercial Portfolio Segment [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, Allowance for Credit Loss	10,536	5,321
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	5,480	9,427
Specific Valuation Allowances [Member] | Commercial Real Estate Portfolio Segment [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, Allowance for Credit Loss	400	513
Specific Valuation Allowances [Member] | Total consumer real estate loans [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, Allowance for Credit Loss	36	0
Specific Valuation Allowances [Member] | Consumer Loan [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, Allowance for Credit Loss	$ 0	$ 18

Loans (Activity in Allowance fo

Loans (Activity in Allowance for Loan Losses by Portfolio Segment) (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Jan. 01, 2020	Dec. 31, 2018
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Allowance for Credit Loss	$ 248,666	$ 263,177
Commercial Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Allowance for Credit Loss	72,091	73,843	$ 51,593		$ 48,580
Financing Receivable, Credit Loss, Expense (Reversal)	(2,160)	15,156	13,144
Financing Receivable, Allowance for Credit Loss, Writeoff	(5,513)	(18,908)	(14,117)
Financing Receivable, Allowance for Credit Loss, Recovery	5,921	4,739	3,986
Allowance for Loan and Lease Losses Write-offs, Net	408	(14,169)	(10,131)
Commercial Portfolio Segment [Member] | Accounting Standards Update 2016-13 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Allowance for Credit Loss				$ 21,263
Commercial And Industrial Energy Financing Receivable [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Allowance for Credit Loss	17,217	39,553	37,382		29,052
Financing Receivable, Credit Loss, Expense (Reversal)	(19,207)	85,889	14,388
Financing Receivable, Allowance for Credit Loss, Writeoff	(5,331)	(76,107)	(7,500)
Financing Receivable, Allowance for Credit Loss, Recovery	2,202	2,842	1,442
Allowance for Loan and Lease Losses Write-offs, Net	(3,129)	(73,265)	(6,058)
Commercial And Industrial Energy Financing Receivable [Member] | Accounting Standards Update 2016-13 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Allowance for Credit Loss				(10,453)
Commercial Real Estate Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Allowance for Credit Loss	144,936	134,892	31,037		38,777
Financing Receivable, Credit Loss, Expense (Reversal)	8,101	124,427	(6,934)
Financing Receivable, Allowance for Credit Loss, Writeoff	(399)	(7,499)	(1,025)
Financing Receivable, Allowance for Credit Loss, Recovery	2,342	446	219
Allowance for Loan and Lease Losses Write-offs, Net	1,943	(7,053)	(806)
Commercial Real Estate Portfolio Segment [Member] | Accounting Standards Update 2016-13 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Allowance for Credit Loss				(13,519)
Total consumer real estate loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Allowance for Credit Loss	6,585	7,926	4,113		6,103
Financing Receivable, Credit Loss, Expense (Reversal)	(3,061)	1,906	467
Financing Receivable, Allowance for Credit Loss, Writeoff	(829)	(2,186)	(3,665)
Financing Receivable, Allowance for Credit Loss, Recovery	2,549	1,701	1,208
Allowance for Loan and Lease Losses Write-offs, Net	1,720	(485)	(2,457)
Total consumer real estate loans [Member] | Accounting Standards Update 2016-13 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Allowance for Credit Loss				2,392
Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Allowance for Credit Loss	7,837	6,963	8,042		9,620
Financing Receivable, Credit Loss, Expense (Reversal)	10,230	9,632	12,694
Financing Receivable, Allowance for Credit Loss, Writeoff	(18,614)	(17,830)	(24,725)
Financing Receivable, Allowance for Credit Loss, Recovery	9,258	9,367	10,453
Allowance for Loan and Lease Losses Write-offs, Net	(9,356)	(8,463)	(14,272)
Consumer Loan [Member] | Accounting Standards Update 2016-13 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Allowance for Credit Loss				(2,248)
Loans Receivable [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Allowance for Credit Loss	248,666	263,177	132,167		$ 132,132
Financing Receivable, Credit Loss, Expense (Reversal)	(6,097)	237,010	33,759
Financing Receivable, Allowance for Credit Loss, Writeoff	(30,686)	(122,530)	(51,032)
Financing Receivable, Allowance for Credit Loss, Recovery	22,272	19,095	17,308
Allowance for Loan and Lease Losses Write-offs, Net	$ (8,414)	$ (103,435)	$ (33,724)
Loans Receivable [Member] | Accounting Standards Update 2016-13 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Allowance for Credit Loss				$ (2,565)

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, 2021	Dec. 31, 2020
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	$ 16,336,397	$ 17,481,309
Commercial Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	5,364,954	4,955,341
Commercial and Industrial Total Energy Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	1,077,792	1,235,198
Paycheck Protection Program [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	428,882	2,433,849
Commercial Real Estate, Buildings, Land and Other [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	6,272,339	5,796,653
Construction Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	1,304,271	1,223,814
Total consumer real estate loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	1,410,790	1,330,774
Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	477,369	505,680
Specific Valuation Allowances [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Portion of allowance for loan losses	16,452	15,279
Specific Valuation Allowances [Member] | Commercial Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Portion of allowance for loan losses	10,536	5,321
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	5,480	9,427
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	200	513
Specific Valuation Allowances [Member] | Construction Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Portion of allowance for loan losses	200	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	36	0
Specific Valuation Allowances [Member] | Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Portion of allowance for loan losses	0	18
Loans Individually Evaluated for Impairment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	66,837	80,495
Loans Individually Evaluated for Impairment [Member] | Commercial Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	24,523	21,287
Loans Individually Evaluated for Impairment [Member] | Commercial and Industrial Total Energy Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	16,393	22,888
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	24,670	34,057
Loans Individually Evaluated for Impairment [Member] | Construction Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	948	1,684
Loans Individually Evaluated for Impairment [Member] | Total consumer real estate loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	303	561
Loans Individually Evaluated for Impairment [Member] | Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	$ 0	$ 18

Premises and Equipment (Narrati

Premises and Equipment (Narrative) (Detail) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Jun. 30, 2019	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Jan. 01, 2019
Property, Plant and Equipment [Line Items]
Depreciation		$ 55,100	$ 49,900	$ 41,000
Operating Lease, Rent Expense		45,600	46,000	42,100
Operating Lease, Right-of-Use Asset		281,438	292,087
Operating lease, payments		32,100	31,600
Recognition of right of use asset related to the new corporate headquarters facility	$ 121,700
Recognition of operating lease liability related to the new corporate headquarters facility	$ 121,700
Premises and Equipment
Property, Plant and Equipment [Line Items]
Operating Lease, Right-of-Use Asset		281,400	292,100		$ 170,500
Other Liabilities [Member]
Property, Plant and Equipment [Line Items]
Operating lease, liability		313,404	323,000		$ 174,400
Partnership Interest [Member]
Property, Plant and Equipment [Line Items]
Operating Lease, Rent Expense		$ 322	$ 9,800	$ 5,900

Premises and Equipment (Premise

Premises and Equipment (Premises and Equipment) (Detail) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Property, Plant and Equipment [Abstract]
Land	$ 152,219	$ 128,739
Buildings	495,903	458,693
Technology, furniture and equipment	256,323	243,395
Leasehold improvements	192,207	183,827
Construction and projects in progress	14,513	41,202
Operating lease, right-of-use asset	281,438	292,087
Premises and equipment, Gross	1,392,603	1,347,943
Less accumulated depreciation and amortization	(342,272)	(302,365)
Total premises and equipment, net	$ 1,050,331	$ 1,045,578

Premises and Equipment (Lease C

Premises and Equipment (Lease Commitments, Components of Lease Expense) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Property, Plant and Equipment [Line Items]
Amortization of lease right-of-use assets	$ 32,811	$ 32,772
Short-term lease expense	1,595	1,799
Non-lease components (including taxes, insurance, common maintenance, etc.)	11,203	11,396
Total operating lease expense, excluding rent	$ 45,609	$ 45,967

Premises and Equipment Future M

Premises and Equipment Future Minimum Lease Payments Due Under non-Cancelable Operating Leases (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020	Jan. 01, 2019
Property, Plant and Equipment [Line Items]
2022	$ 32,222
2023	31,458
2024	29,398
2025	28,253
2026	27,833
Thereafter	245,819
Total undiscounted operating lease liability	394,983
Imputed interest	$ 81,579
Weighted-average lease term in years	14 years 8 months 23 days
Weighted-average discount rate	3.05%
Other Liabilities [Member]
Property, Plant and Equipment [Line Items]
Operating lease, liability	$ 313,404	$ 323,000	$ 174,400

Goodwill and Other Intangible_3

Goodwill and Other Intangible Assets (Narrative) (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Finite-Lived Intangible Assets [Line Items]
Amortization expense related to intangible assets	$ 697	$ 918	$ 1,168
Minimum [Member]
Finite-Lived Intangible Assets [Line Items]
Other intangible assets estimated lives, years	5 years
Maximum [Member]
Finite-Lived Intangible Assets [Line Items]
Other intangible assets estimated lives, years	10 years

Goodwill and Other Intangible_4

Goodwill and Other Intangible Assets (Schedule of Goodwill) (Detail) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill	$ 654,952	$ 654,952

Goodwill and Other Intangible_5

Goodwill and Other Intangible Assets (Schedule of Other Intangible Assets) (Detail) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Finite-Lived Intangible Assets [Line Items]
Gross Intangible Assets	$ 11,685	$ 12,186
Accumulated Amortization	(10,819)	(10,623)
Net Intangible Assets	866	1,563
Core Deposits [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Intangible Assets	9,300	9,300
Accumulated Amortization	(8,582)	(8,004)
Net Intangible Assets	718	1,296
Customer Relationships [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Intangible Assets	2,385	2,886
Accumulated Amortization	(2,237)	(2,619)
Net Intangible Assets	$ 148	$ 267

Goodwill and Other Intangible_6

Goodwill and Other Intangible Assets (Estimated Aggregate Future Amortization Expense for Intangible Assets) (Detail) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Goodwill and Intangible Assets Disclosure [Abstract]
2022	$ 481
2023	282
2024	87
2025	11
2026	5
Thereafter	0
Finite-Lived Intangible Assets, Net, Total	$ 866	$ 1,563

Deposits (Schedule of Deposits)

Deposits (Schedule of Deposits) (Detail) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Deposit Liability [Line Items]
Non-interest-bearing demand deposits	$ 18,423,018	$ 15,117,051
Savings and interest checking	11,930,959	9,730,292
Money market accounts	11,228,815	9,027,655
Time accounts	1,112,904	1,140,763
Total Interest-bearing deposits	24,272,678	19,898,710
Total deposits	$ 42,695,696	$ 35,015,761

Deposits (Additional Informatio

Deposits (Additional Information About Corporation's Deposits) (Detail) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Deposit Liability [Line Items]
Deposits from the Certificate of Deposit Account Registry Service (CDARS)	$ 0	$ 372
Deposits from foreign sources (primarily Mexico)	993,479	884,169
Non-interest-bearing public funds deposits	18,423,018	15,117,051
Interest-bearing public funds deposits	24,272,678	19,898,710
Total deposits not covered by deposit insurance	24,125,359	18,694,320
Time deposits not covered by deposit insurance	238,608	237,298
Deposits from certain directors, executive officers and their affiliates	276,556	210,389
Public Funds [Member]
Deposit Liability [Line Items]
Non-interest-bearing public funds deposits	1,235,026	960,072
Interest-bearing public funds deposits	$ 810,863	$ 652,761

Deposits (Scheduled Maturities

Deposits (Scheduled Maturities of Time Deposits) (Detail) $ in Thousands	Dec. 31, 2021USD ($)
Deposits [Abstract]
2022	$ 891,392
2023	221,512
Time deposits, Total	$ 1,112,904

Deposits (Scheduled Maturitie_2

Deposits (Scheduled Maturities of Time Deposits Not Covered By Deposit Insurance) (Detail) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Deposits [Abstract]
Due within 3 months or less	$ 92,403
Due after 3 months and within 6 months	34,038
Due after 6 months and within 12 months	58,357
Due after 12 months	53,810
Time deposits liability, above US Insurance Limit Total	$ 238,608	$ 237,298

Borrowed Funds (Narrative) (Det

Borrowed Funds (Narrative) (Detail) $ in Thousands	Mar. 17, 2017USD ($)	Dec. 31, 2021USD ($)quarter	Dec. 31, 2020USD ($)	Dec. 31, 2004USD ($)
Borrowed Funds [Line Items]
Federal funds purchased		$ 25,925	$ 48,850
Repurchase agreements		2,740,799	2,068,147
Subordinated notes		99,178	99,021
Junior subordinated deferrable interest debentures		$ 123,011	136,357
Proceeds from issuance of Common Equity Securities			145,452
Maximum number of quarterly periods by which the corporation has the right to defer interest payments on junior subordinated deferrable interest debentures | quarter		20
Trust Preferred Securities Tier Two Capital Allowable Portion [Member] | Cullen/Frost [Member]
Borrowed Funds [Line Items]
Proceeds from Issuance of Trust Preferred Securities		$ 120,000	133,000
Trust II [Member]
Borrowed Funds [Line Items]
Maturity date				Mar. 1, 2034
Proceeds from Issuance of Trust Preferred Securities				$ 120,000
Floating rate 3 month Libor plus margin				1.55%
Proceeds from issuance of Common Equity Securities				$ 3,700
WNB Capital Trust I [Member]
Borrowed Funds [Line Items]
Proceeds from Issuance of Trust Preferred Securities				$ 13,000
Floating rate 3 month Libor plus margin				2.35%
Proceeds from issuance of Common Equity Securities				$ 403
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		$ 822	1,000
Junior Subordinated Deferrable Interest Debenture [Member] | Trust II [Member]
Borrowed Funds [Line Items]
Unamortized debt issuance cost related to note		701	758
Junior subordinated deferrable interest debentures		$ 123,700	$ 123,700	123,700
Floating rate 3 month Libor plus margin		1.72%	1.78%
Junior Subordinated Deferrable Interest Debenture [Member] | WNB Capital Trust I [Member]
Borrowed Funds [Line Items]
Junior subordinated deferrable interest debentures			$ 13,400	$ 13,400
Floating rate 3 month Libor plus margin			2.56%

Off-Balance Sheet Arrangements

Off-Balance Sheet Arrangements Commitments Guarantees and Contingencies (Narrative) (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Commitments And Guarantees [Line Items]
Credit card guarantees	$ 8,600	$ 9,100
Fully collateralized credit card guarantees	962	8,200
Frost Wealth Advisors [Member]
Commitments And Guarantees [Line Items]
Fair value of off-balance sheet managed and custody assets	$ 43,300,000	$ 38,600,000	$ 37,800,000

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, 2021	Dec. 31, 2020
Standby Letters of Credit [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Financial instruments with off- balance-sheet risk	$ 238,690	$ 241,345
Deferred Standby Letter of Credit Fees [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Financial instruments with off- balance-sheet risk	2,072	1,723
Commitments to Extend Credit [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Financial instruments with off- balance-sheet risk	$ 10,420,142	$ 9,814,475

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, 2021	Dec. 31, 2020	Dec. 31, 2019
Fair Value Disclosures [Abstract]
Off-Balance Sheet, Credit Loss, Liability, Beginning Balance	$ 44,152	$ 500	$ 500
Impact of New Accounting Pronouncement	0	39,377	0
Off-Balance Sheet, Credit Loss, Liability, Credit Loss Expense (Reversal)	6,162	4,275	0
Off-Balance Sheet, Credit Loss, Liability, Ending Balance	$ 50,314	$ 44,152	$ 500

Capital and Regulatory Matter_2

Capital and Regulatory Matters (Narrative) (Detail)	Jan. 26, 2022USD ($)	Nov. 19, 2020USD ($)$ / sharesshares	Mar. 16, 2020USD ($)$ / shares	Mar. 17, 2017USD ($)	Feb. 15, 2013USD ($)$ / sharesshares	Dec. 31, 2021USD ($)$ / sharesRateshares	Mar. 31, 2020USD ($)shares	Dec. 31, 2021USD ($)quarter$ / sharesRateshares	Dec. 31, 2020USD ($)$ / sharesRateshares	Dec. 31, 2019USD ($)shares	Dec. 31, 2004USD ($)	Jan. 01, 2020USD ($)	Jan. 01, 2019USD ($)Rate	Dec. 31, 2018USD ($)
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Credit loss optional transitional period under CECL								5 years
Payments for Repurchase of Trust Preferred Securities								$ 13,403,000
Subordinated notes						$ 99,178,000		$ 99,178,000	$ 99,021,000
Cumulative effect of accounting change										$ (29,252,000)				$ (14,672,000)
Credit loss transitional period in years under CECL								3 years
CECL Transition Amount						61,600,000		$ 61,600,000
Estimated Incremental Effect of CECL								$ 32,400,000
Stock Redeemed or Called During Period, Value									$ 150,000,000
Treasury stock, shares, acquired | shares								31,317	206,951	716,062
Treasury Stock, Value, Acquired, Cost Method								$ (3,864,000)	$ (15,785,000)	$ (68,793,000)
Aggregate dividends available for payment without prior regulatory approval						$ 494,100,000		$ 494,100,000
Maximum number of quarterly periods by which the corporation has the right to defer interest payments on junior subordinated deferrable interest debentures | quarter								20
Subsequent Event
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
WNB Capital Trust I [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Trust preferred securities											$ 13,000,000
Retained Earnings [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Cumulative effect of accounting change										(29,252,000)		$ (29,300,000)	$ (14,700,000)	$ (14,672,000)
Stock Redeemed or Called During Period, Value									$ 5,514,000
Series A Preferred Stock [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Non-cumulative perpetual preferred stock, dividend rate percentage					5.375%
Preferred Stock, Shares Issued | shares					6,000,000
Preferred Stock, Aggregate Liquidation Preference, Value					$ 150,000,000
Preferred Stock, Par or Stated Value Per Share | $ / shares					$ 0.01
Liquidation preference per share | $ / shares			$ 25		$ 25
Payments of Stock Issuance Costs					$ 5,500,000
Proceeds from issuance of preferred stock					$ 144,500,000
Stock Redeemed or Called During Period, Value			$ 150,000,000
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	150,000
Preferred Stock, Aggregate Liquidation Preference, Value		$ 150,000,000				$ 1,000		$ 1,000	$ 1,000
Preferred Stock, Par or Stated Value Per Share | $ / shares		$ 0.01				$ 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								20.00%
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	$ 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						7.00%		7.00%	7.00%				7.00%
Tier One Risk Based Capital Required for Capital Adequacy to Risk Weighted Assets | Rate													6.00%
Effective tier one capital ratio, upon full implementation						8.50%		8.50%	8.50%				8.50%
Minimum ratio of Total capital to risk weighted assets | Rate						15.45%		15.45%	15.44%				8.00%
Tier one risk based capital to risk weighted assets, ratio upon full implementation						10.50%		10.50%	10.50%				10.50%
Minimum leverage ratio						4.00%		4.00%	4.00%				4.00%
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	$ 133,000,000
Cullen/Frost [Member] | Trust Preferred Securities Tier Two Capital Allowable Portion [Member] | WNB Capital Trust I [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Payments for Repurchase of Trust Preferred Securities						$ 13,000,000
Cullen/Frost [Member] | Subordinated Debt [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Permissible Portion Of Subordinated Note Included In Capital						100,000,000		100,000,000	100,000,000
Frost Bank [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Additional Tier 1 Capital beyond Common Equity Tier 1						$ 0		$ 0	$ 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						7.00%		7.00%	7.00%
Tier One Risk Based Capital Required for Capital Adequacy to Risk Weighted Assets | Rate													6.00%
Effective tier one capital ratio, upon full implementation						8.50%		8.50%	8.50%				8.50%
Minimum ratio of Total capital to risk weighted assets | Rate						13.61%		13.61%	13.76%				8.00%
Tier one risk based capital to risk weighted assets, ratio upon full implementation						10.50%		10.50%	10.50%				10.50%
Minimum leverage ratio						4.00%		4.00%	4.00%				4.00%
Prior stock repurchase plans [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Treasury Stock, Value, Acquired, Cost Method							$ (13,700,000)			$ (67,200,000)
Prior stock repurchase plans [Member] | Treasury Stock [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Treasury stock, shares, acquired | shares							177,834			699,031
stock repurchase 2021 plan | Treasury Stock [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Treasury stock, shares, acquired | shares								0

Regulatory Matters (Actual and

Regulatory Matters (Actual and Required Capital Ratios) (Detail) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020	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	$ 3,371,043	$ 3,058,447
Common Equity Tier One Risk-Based Capital Ratio, Actual	13.13%	12.86%
Common Equity Tier One Capital Required For Capital Adequacy Minimum Capital Required Basel III Fully Phased In, Capital Amount	$ 1,796,549	$ 1,664,867
Common Equity Tier One Risk Based Capital To Risk Weighted Assets Minimum Capital Required Basel III Fully Phased In, Ratio	7.00%	7.00%	7.00%
Common Equity Tier One Capital Required To Be Well Capitalized, Capital Amount	$ 1,668,224	$ 1,545,948
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	$ 3,516,495	$ 3,203,899
Tier 1 Capital to Risk-Weighted Assets, Actual, Ratio	13.70%	13.47%
Tier One Risk Based Capital Required For Capital Adequacy Minimum Capital Required Basel III Fully Phased In, Capital Amount	$ 2,181,523	$ 2,021,624
Tier One Risk Based Capital Required for Capital Adequacy to Risk Weighted Assets Minimum Capital Required Basel III Fully Phased In, Ratio	8.50%	8.50%	8.50%
Tier 1 Capital to Risk-Weighted Assets, Required to be Considered Well Capitalized, Capital Amount	$ 2,053,198	$ 1,902,705
Tier 1 Capital to Risk-Weighted Assets, Required to be Considered Well Capitalized, Ratio	8.00%	8.00%
Total Capital to Risk-Weighted Assets, Actual, Capital Amount	$ 3,966,244	$ 3,672,912
Total Capital to Risk-Weighted Assets, Actual, Ratio	15.45%	15.44%	8.00%
Capital Required for Capital Adequacy Minimum Capital Required Basel III Fully Phased In, Capital Amount	$ 2,694,823	$ 2,497,300
Capital Required for Capital Adequacy to Risk Weighted Assets Minimum Capital Required Basel III Fully Phased In, Ratio	10.50%	10.50%	10.50%
Total Capital to Risk-Weighted Assets, Required to be Considered Well Capitalized, Capital Amount	$ 2,566,498	$ 2,378,381
Total Capital to Risk-Weighted Assets, Required to be Considered Well Capitalized, Ratio	10.00%	10.00%
Leverage Ratio, Actual, Capital Amount	$ 3,516,495	$ 3,203,899
Leverage Ratio, Actual, Ratio	7.34%	8.07%
Tier One Leverage Capital Required for Capital Adequacy Minimum Capital Required Basel III Fully Phased In, Capital Amount	$ 1,917,533	$ 1,589,004
Tier One Leverage Capital Required for Capital Adequacy to Average Assets Minimum Capital Required Basel III Fully Phased In, Ratio	4.00%	4.00%	4.00%
Leverage Ratio, Required to be Considered Well Capitalized, Capital Amount	$ 2,396,917	$ 1,986,255
Leverage Ratio, Required to be Considered Well Capitalized, Ratio	5.00%	5.00%
Frost Bank [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Common Equity Tier One to Risk-Weighted Assets, Actual, Capital Amount	$ 3,261,532	$ 3,030,093
Common Equity Tier One Risk-Based Capital Ratio, Actual	12.72%	12.77%
Common Equity Tier One Capital Required For Capital Adequacy Minimum Capital Required Basel III Fully Phased In, Capital Amount	$ 1,795,221	$ 1,661,620
Common Equity Tier One Risk Based Capital To Risk Weighted Assets Minimum Capital Required Basel III Fully Phased In, Ratio	7.00%	7.00%
Common Equity Tier One Capital Required To Be Well Capitalized, Capital Amount	$ 1,666,991	$ 1,542,933
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	$ 3,261,532	$ 3,030,093
Tier 1 Capital to Risk-Weighted Assets, Actual, Ratio	12.72%	12.77%
Tier One Risk Based Capital Required For Capital Adequacy Minimum Capital Required Basel III Fully Phased In, Capital Amount	$ 2,179,911	$ 2,017,682
Tier One Risk Based Capital Required for Capital Adequacy to Risk Weighted Assets Minimum Capital Required Basel III Fully Phased In, Ratio	8.50%	8.50%	8.50%
Tier 1 Capital to Risk-Weighted Assets, Required to be Considered Well Capitalized, Capital Amount	$ 2,051,681	$ 1,898,995
Tier 1 Capital to Risk-Weighted Assets, Required to be Considered Well Capitalized, Ratio	8.00%	8.00%
Total Capital to Risk-Weighted Assets, Actual, Capital Amount	$ 3,491,281	$ 3,266,106
Total Capital to Risk-Weighted Assets, Actual, Ratio	13.61%	13.76%	8.00%
Capital Required for Capital Adequacy Minimum Capital Required Basel III Fully Phased In, Capital Amount	$ 2,692,831	$ 2,492,430
Capital Required for Capital Adequacy to Risk Weighted Assets Minimum Capital Required Basel III Fully Phased In, Ratio	10.50%	10.50%	10.50%
Total Capital to Risk-Weighted Assets, Required to be Considered Well Capitalized, Capital Amount	$ 2,564,601	$ 2,373,743
Total Capital to Risk-Weighted Assets, Required to be Considered Well Capitalized, Ratio	10.00%	10.00%
Leverage Ratio, Actual, Capital Amount	$ 3,261,532	$ 3,030,093
Leverage Ratio, Actual, Ratio	6.80%	7.63%
Tier One Leverage Capital Required for Capital Adequacy Minimum Capital Required Basel III Fully Phased In, Capital Amount	$ 1,917,679	$ 1,588,200
Tier One Leverage Capital Required for Capital Adequacy to Average Assets Minimum Capital Required Basel III Fully Phased In, Ratio	4.00%	4.00%	4.00%
Leverage Ratio, Required to be Considered Well Capitalized, Capital Amount	$ 2,397,099	$ 1,985,250
Leverage Ratio, Required to be Considered Well Capitalized, Ratio	5.00%	5.00%

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, 2021	Dec. 31, 2020	Dec. 31, 2019
Earnings Per Share [Abstract]
Net income	$ 443,079	$ 331,151	$ 443,599
Less: Preferred stock dividends	7,157	2,016	8,063
Redemption of preferred stock	0	5,514	0
Net income available to common shareholders	435,922	323,621	435,536
Less: Earnings allocated to participating securities	3,881	3,136	3,687
Net earnings allocated to common stock	432,041	320,485	431,849
Distributed earnings allocated to common stock	187,202	178,863	175,540
Undistributed earnings allocated to common stock	$ 244,839	$ 141,622	$ 256,309
Weighted-average shares outstanding for basic earnings per common share	63,612,658	62,727,053	62,741,769
Dilutive effect of stock compensation	489,462	276,784	700,101
Weighted-average shares outstanding for diluted earnings per common share	64,102,120	63,003,837	63,441,870

Employee Benefit Plans (Narrati

Employee Benefit Plans (Narrative) (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Defined contribution plan, cost	$ 23,800,000	$ 17,900,000
Percentage of equity investments in mutual fund	68.00%
Net periodic benefit cost, Expected return on plan assets	7.25%	7.25%	7.25%
Expected defined benefit plans contribution within a year	$ 1,200,000
Number of stock plans	3
Dividends, share-based compensation	$ 0.75	$ 0.72	$ 0.71
Weighted-average risk-free interest rate	0.77%	0.19%	1.65%
Options awarded during period	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	777,687
Base-year adjusted net revenue amount	$ 426,600,000
Base-year calculation basis point adjustment	0.30%
Percentage level of achievement - 13 percent average growth	13.00%
Award payout percentage of target at 50 percent	50.00%
Percentage level of achievement - 19 percent average growth	19.00%
Award payout percentage of target at 100 percent	100.00%
Percentage level of achievement - 25 percent average growth	25.00%
Award payout percentage of target at 150 percent	150.00%
Award payout percentage at less than 25th percentile level of achievement	0.00%
Award payout percentage at the 25th percentile level of achievement	50.00%
Award payout percentage at the 50th percentile level of achievement	100.00%
Award payout percentage at the 75th percentile level of achievement	150.00%
Performance Shares [Member] | Pro Forma [Member]
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Granted in period, number of shares/units	30,723	48,409	34,317
Equity Securities [Member]
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Target asset allocation percentage	62.00%
Fixed Income Securities [Member]
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Target asset allocation percentage	36.00%
Two Thousand Fifteen Plan [Member] | Stock Options [Member]
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Vesting period of options awarded, years	4 years
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]
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
Minimum [Member] | Performance Shares [Member]
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Percentage level of achievement - less than 13 percent average growth	13.00%
Award payout percentage of target at 0 percent	0.00%
Maximum [Member] | Performance Shares [Member]
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Granted in period, number of shares/units	46,086	72,618	51,479
Deferred Profit Sharing [Member]
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Defined contribution plan, cost	$ 0	$ 0	$ 0
Other Pension Plan [Member] | Qualified Plan [Member]
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Defined contribution plan, cost			$ 28,900,000
Participants contribution eligible for match	100.00%
Other Pension Plan [Member] | Qualified Plan [Member] | Minimum [Member]
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Maximum annual contributions per employee, percent	2.00%
Other Pension Plan [Member] | Qualified Plan [Member] | Maximum [Member]
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Maximum annual contributions per employee, percent	50.00%
Employer matching contribution, percent of employees' gross pay	6.00%

Employee Benefit Plans (Combine

Employee Benefit Plans (Combined Activity in Corporations Defined Benefit Pension Plans) (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Retirement Benefits [Abstract]
Fair value of plan assets at beginning of year	$ 182,088	$ 174,173	$ 152,820
Actual return on plan assets	24,908	16,599	29,945
Employer contributions	1,236	1,201	1,163
Benefits paid	(10,485)	(9,885)	(9,755)
Fair value of plan assets at end of year	197,747	182,088	174,173
Benefit obligation at beginning of year	197,593	186,641	167,107
Interest cost	3,341	5,010	6,472
Actuarial (gain) loss	(4,524)	15,827	22,817
Benefits paid	(10,485)	(9,885)	(9,755)
Benefit obligation at end of year	185,925	197,593	186,641
Funded status of the plan at end of year and accrued benefit (liability) recognized	11,822	(15,505)	(12,468)
Accumulated benefit obligation at end of year	$ 185,925	$ 197,593	$ 186,641

Employee Benefit Plans (Disaggr

Employee Benefit Plans (Disaggregated Information Related to Corporations Defined Benefit Pension Plans) (Detail) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Defined Benefit Plan Disclosure [Line Items]
Projected benefit obligation	$ 185,925	$ 197,593	$ 186,641	$ 167,107
Accumulated benefit obligation	185,925	197,593	186,641
Fair value of plan assets	197,747	182,088	174,173	$ 152,820
Funded status of the plan at end of year and accrued benefit (liability) recognized	11,822	(15,505)	$ (12,468)
Retirement Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Projected benefit obligation	170,389	180,986
Accumulated benefit obligation	170,389	180,986
Fair value of plan assets	197,747	182,088
Funded status of the plan at end of year and accrued benefit (liability) recognized	27,358	1,102
Restoration Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Projected benefit obligation	15,536	16,607
Accumulated benefit obligation	15,536	16,607
Fair value of plan assets	0	0
Funded status of the plan at end of year and accrued benefit (liability) recognized	$ (15,536)	$ (16,607)

Employee Benefit Plans (Net Per

Employee Benefit Plans (Net Periodic Benefit Cost (Benefit)) (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Retirement Benefits [Abstract]
Expected return on plan assets, net of expenses	$ (12,839)	$ (12,289)	$ (10,772)
Interest cost on projected benefit obligation	3,341	5,010	6,472
Net amortization and deferral	6,116	5,319	5,623
Net periodic expense (benefit)	$ (3,382)	$ (1,960)	$ 1,323

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, 2021	Dec. 31, 2020	Dec. 31, 2019
Defined Benefit Plan Disclosure [Line Items]
Net actuarial gain (loss)	$ 22,709	$ (6,199)	$ 1,979
Deferred tax (expense) benefit	(4,769)	1,302	(416)
Other comprehensive income (loss), net of tax	$ 17,940	$ (4,897)	$ 1,563

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, 2021	Dec. 31, 2020
Defined Benefit Plan Disclosure [Line Items]
Net actuarial loss	$ (41,634)	$ (64,343)
Deferred tax benefit	8,743	13,512
Amounts included in accumulated other comprehensive loss, net of tax	$ (32,891)	$ (50,831)

Employee Benefit Plans (Weighte

Employee Benefit Plans (Weighted-Average Assumptions Used to Determine Benefit Obligations) (Detail)	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Retirement Benefits [Abstract]
Benefit obligations, Discount rate	2.79%	2.43%	3.20%
Net periodic benefit cost, Discount rate	2.43%	3.20%	4.36%
Net periodic benefit cost, Expected return on plan assets	7.25%	7.25%	7.25%

Employee Benefit Plans (Fair Va

Employee Benefit Plans (Fair Value of Plan Assets) (Detail) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 197,747	$ 182,088	$ 174,173	$ 152,820
Mutual Funds [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	195,452	180,693
Cash and Cash Equivalents [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 2,295	$ 1,395

Employee Benefit Plans (Expecte

Employee Benefit Plans (Expected Future Benefit Payments Related to Defined Benefit Plans) (Detail) $ in Thousands	Dec. 31, 2021USD ($)
Retirement Benefits [Abstract]
2022	$ 11,592
2023	11,805
2024	11,975
2025	11,982
2026	12,018
2027 through 2031	56,494
Total defined benefit plan expected future benefit payments	$ 115,866

Employee Benefit Plans (Summary

Employee Benefit Plans (Summary of Activity in Corporation's Active Stock Plans) (Detail) - $ / shares	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock options exercised, number of shares	(987,758)	(408,563)	(399,224)
Director deferred stock units outstanding [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Ending balance, number of shares/units	56,301	52,860	55,370
Beginning balance, number of shares/units	52,860	55,370	48,910
Ending balance, weighted-average grant-date fair value	$ 79.21	$ 75.47	$ 74.76
Beginning balance, weighted-average grant-date fair value	$ 75.47	$ 74.76	$ 71.14
Granted in period, number of shares/units	5,940	10,428	7,592
Granted in period, weighted-average grant-date fair value	$ 117.90	$ 73.84	$ 102.70
Stock awards exercised/vested in period, number of shares	(2,499)	(12,938)	(1,132)
Stock awards exercised/vested in period, weighted-average grant date fair value	$ 92.03	$ 71.09	$ 106.03
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	449,337	470,359	440,647
Beginning balance, number of shares/units	470,359	440,647	383,797
Ending balance, weighted-average grant-date fair value	$ 93.05	$ 86.24	$ 90.22
Beginning balance, weighted-average grant-date fair value	$ 86.24	$ 90.22	$ 85.59
Granted in period, number of shares/units	95,258	151,038	127,091
Granted in period, weighted-average grant-date fair value	$ 130.36	$ 66.79	$ 93.46
Stock awards exercised/vested in period, number of shares	(88,250)	(117,990)	(53,990)
Stock awards exercised/vested in period, weighted-average grant date fair value	$ 98.90	$ 76.07	$ 65.11
Forfeited/expired in period, number of shares/units	(28,030)	(3,336)	(16,251)
Forfeited/expired in period, weighted-average grant date fair value	$ 87.08	$ 91.07	$ 89.71
Share-based Payment Arrangement, Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Ending balance, number of shares	877,681	1,739,559	1,980,866
Beginning balance, number of shares	1,739,559	1,980,866	2,352,008
Ending balance, weighted-average exercise price	$ 69.02	$ 66.11	$ 64.60
Beginning balance, weighted-average exercise price	$ 66.11	$ 64.60	$ 63.55
Stock options exercised, number of shares	(861,878)	(235,880)	(359,892)
Stock options exercised, weighted-average exercise price	$ 63.14	$ 53.23	$ 57.71
Forfeited/expired, number of shares		(5,427)	(11,250)
Forfeited/expired, weighted-average exercise price		$ 75.74	$ 65.11
Maximum [Member] | Performance Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Ending balance, number of shares/units	202,460	201,257	177,288
Beginning balance, number of shares/units	201,257	177,288	125,809
Ending balance, weighted-average grant-date fair value	$ 84.71	$ 77.18	$ 83.48
Beginning balance, weighted-average grant-date fair value	$ 77.18	$ 83.48	$ 82.55
Granted in period, number of shares/units	46,086	72,618	51,479
Granted in period, weighted-average grant-date fair value	$ 121.46	$ 57.89	$ 85.74
Stock awards exercised/vested in period, number of shares	(35,131)	(41,755)
Stock awards exercised/vested in period, weighted-average grant date fair value	$ 92.27	$ 69.70
Forfeited/expired in period, number of shares/units	(9,752)	(6,894)
Forfeited/expired in period, weighted-average grant date fair value	$ 75.70	$ 81.33

Employee Benefit Plans (Options

Employee Benefit Plans (Options Outstanding and Exercisable) (Detail) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2021USD ($)$ / sharesshares
50.01 - 55.00 [Member]
Share-based Payment Arrangement, Option, Exercise Price Range [Line Items]
Range of Exercise Prices, Minimum	$ 50.01
Range of Exercise Prices, Maximum	55
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
70.01 - 75.00 [Member]
Share-based Payment Arrangement, Option, Exercise Price Range [Line Items]
Range of Exercise Prices, Minimum	70.01
Range of Exercise Prices, Maximum	75
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	877,681
Weighted-Average Exercise Price, Options Outstanding	$ 69.02
Weighted- Average Remaining Contractual Life in Years	2 years 7 months 20 days
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Intrinsic Value | $	$ 50,070
Options Outstanding [Member] | 50.01 - 55.00 [Member]
Share-based Payment Arrangement, Option, Exercise Price Range [Line Items]
Number of Shares, Options Outstanding | shares	123,314
Weighted-Average Exercise Price, Options Outstanding	$ 54.56
Weighted- Average Remaining Contractual Life in Years	9 months 21 days
Options Outstanding [Member] | 65.01 - 70.00 [Member]
Share-based Payment Arrangement, Option, Exercise Price Range [Line Items]
Number of Shares, Options Outstanding | shares	319,081
Weighted-Average Exercise Price, Options Outstanding	$ 65.11
Weighted- Average Remaining Contractual Life in Years	3 years 8 months 19 days
Options Outstanding [Member] | 70.01 - 75.00 [Member]
Share-based Payment Arrangement, Option, Exercise Price Range [Line Items]
Number of Shares, Options Outstanding | shares	169,726
Weighted-Average Exercise Price, Options Outstanding	$ 71.39
Weighted- Average Remaining Contractual Life in Years	1 year 9 months 10 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	265,560
Weighted-Average Exercise Price, Options Outstanding	$ 78.92
Weighted- Average Remaining Contractual Life in Years	2 years 9 months
Options Exercisable [Member]
Share-based Payment Arrangement, Option, Exercise Price Range [Line Items]
Number of Shares, Options Exercisable | shares	877,681
Weighted-Average Exercise Price, Options Exercisable	$ 69.02
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Intrinsic Value | $	$ 50,070
Options Exercisable [Member] | 50.01 - 55.00 [Member]
Share-based Payment Arrangement, Option, Exercise Price Range [Line Items]
Number of Shares, Options Exercisable | shares	123,314
Weighted-Average Exercise Price, Options Exercisable	$ 54.56
Options Exercisable [Member] | 65.01 - 70.00 [Member]
Share-based Payment Arrangement, Option, Exercise Price Range [Line Items]
Number of Shares, Options Exercisable | shares	319,081
Weighted-Average Exercise Price, Options Exercisable	$ 65.11
Options Exercisable [Member] | 70.01 - 75.00 [Member]
Share-based Payment Arrangement, Option, Exercise Price Range [Line Items]
Number of Shares, Options Exercisable | shares	169,726
Weighted-Average Exercise Price, Options Exercisable	$ 71.39
Options Exercisable [Member] | 75.01 - 80.00 [Member]
Share-based Payment Arrangement, Option, Exercise Price Range [Line Items]
Number of Shares, Options Exercisable | shares	265,560
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, 2021	Dec. 31, 2020	Dec. 31, 2019
Retirement Benefits [Abstract]
Shares issued from available treasury stock	987,758	408,563	399,224
Proceeds from stock option exercises	$ 54,417	$ 12,557	$ 20,770
Intrinsic value of stock options exercised	43,904	5,365	13,713
Fair value of stock awards/units vested	$ 15,751	$ 12,773	$ 5,192

Employee Benefit Plans (Stock-B

Employee Benefit Plans (Stock-Based Compensation Expense) (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Stock options	$ 0	$ 0	$ 1,185
Non-vested stock awards/stock units	9,977	10,240	9,339
Deferred stock-units	700	770	780
Performance stock units	2,076	2,908	4,642
Total	12,753	13,918	15,946
Income tax benefit	$ 1,713	$ 2,142	$ 2,359

Employee Benefit Plans (Unrecog

Employee Benefit Plans (Unrecognized Stock-Based Compensation Expense) (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2021USD ($)
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Non-vested stock awards/stock units	$ 18,431
Performance stock units	9,818
Total	$ 28,249
Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Period for Recognition	2 years 25 days
Employee service share-based compensation, Performance stock units,compensation cost not yet recognized,period for recognition	2 years 1 month 28 days

Other Non-Interest Income and_3

Other Non-Interest Income and Expense (Narrative) (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
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	1.00%	1.00%	1.00%
Payment for services provided by related party	$ 257	$ 551	$ 567

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, 2021	Dec. 31, 2020	Dec. 31, 2019
Other Income and Expenses [Abstract]
Other	$ 48,528	$ 47,712	$ 43,563
Total other non-interest income	48,528	47,712	43,563
Professional services	34,747	37,253	39,238
Advertising, promotions and public relations	34,539	34,390	38,001
Travel/meals and entertainment	4,946	7,109	16,459
Other	97,225	87,558	86,967
Total other non-interest expense	$ 171,457	$ 166,310	$ 180,665

Income Taxes (Narrative) (Detai

Income Taxes (Narrative) (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Income Tax Disclosure [Abstract]
U.S. federal statutory income tax rate	21.00%	21.00%	21.00%
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, 2021	Dec. 31, 2020	Dec. 31, 2019
Income Tax Disclosure [Abstract]
Current income tax expense	$ 38,675	$ 36,002	$ 48,256
Deferred income tax expense (benefit)	7,784	(15,832)	7,614
Income tax expense, as reported	$ 46,459	$ 20,170	$ 55,870
Effective tax rate	9.50%	5.70%	11.20%

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, 2021	Dec. 31, 2020	Dec. 31, 2019
Income Tax Disclosure [Abstract]
Income tax expense computed at the statutory rate	$ 102,803	$ 73,777	$ 104,888
Effect of tax-exempt interest	(50,740)	(51,624)	(49,166)
Tax benefit on dividends paid in our 401k plan	(1,764)	(1,851)	(1,743)
Bank owned life insurance income	(517)	(783)	(774)
Non-deductible FDIC premiums	2,629	1,790	1,267
Non-deductible compensation	1,773	1,123	1,708
Non-deductible meals and entertainment	625	786	1,299
Net tax benefit from stock-based compensation	(7,877)	(852)	(2,447)
Asset contribution to a charitable trust	0	(2,556)	0
Tax basis adjustment of premises and equipment	(1,026)	0	0
Other	553	360	838
Income tax expense, as reported	$ 46,459	$ 20,170	$ 55,870

Income Taxes (Schedule of Defer

Income Taxes (Schedule of Deferred Tax Assets and Liabilities) (Detail) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Income Tax Disclosure [Abstract]
Lease liabilities under operating leases	$ 65,815	$ 67,839
Allowance for credit losses	62,819	64,573
Net actuarial loss on defined benefit post-retirement benefit plans	8,743	13,512
Stock-based compensation	6,989	10,033
Bonus accrual	7,506	3,961
Deferred loan and lease origination fees	3,118	10,252
Other	3,834	3,834
Total gross deferred tax assets	158,824	174,004
Net unrealized gain on securities available for sale and transferred securities	(101,067)	(149,870)
Right-of-use assets under operating leases	(59,415)	(61,963)
Premises and equipment	(49,645)	(49,602)
Intangible assets	(16,595)	(14,596)
Defined benefit post-retirement benefit plans	(11,027)	(10,081)
Partnership interests	0	(2,913)
Leases	(712)	(1,090)
Other	(1,611)	(1,387)
Total gross deferred tax liabilities	(240,072)	(291,502)
Deferred Tax Liabilities, Net	$ (81,248)	$ (117,498)

Other Comprehensive Income (L_3

Other Comprehensive Income (Loss) (Component of Other Comprehensive Income (Loss)) (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Equity [Abstract]
Securities available for sale and transferred securities, Change in net unrealized gain/loss during the period, before tax amount	$ (231,355)	$ 427,331	$ 418,556
Securities available for sale and transferred securities, Change in net unrealized gain on securities transferred to held to maturity, before tax amount	(971)	(1,256)	(1,292)
Securities available for sale and transferred securities, Reclassification adjustment for net (gains) losses included in net income, before tax amount	(69)	(108,989)	(293)
Total securities available for sale and transferred securities before tax amount	(232,395)	317,086	416,971
Change in the net actuarial gain/loss before tax amount	16,593	(11,518)	(3,644)
Reclassification adjustment for net amortization of actuarial gain/loss included in net income as a component of net periodic cost (benefit) before tax amount	6,116	5,319	5,623
Total defined-benefit post-retirement benefit plans	22,709	(6,199)	1,979
Other comprehensive income (loss), before tax	(209,686)	310,887	418,950
Securities available for sale and transferred securities, Change in net unrealized gain/loss during the period, tax expense (benefit)	(48,585)	89,741	87,897
Securities available for sale and transferred securities, change in net unrealized gain on securities transfers to held-to-maturity, tax expense benefit	(204)	(264)	(271)
Securities available for sale and transferred securities, Reclassification adjustment for net (gains) losses included in net income, tax expense (benefit)	(14)	(22,888)	(62)
Total securities available for sale and transferred securities, tax expense (benefit)	(48,803)	66,589	87,564
Change in the net actuarial gain/loss, tax expense (benefit)	3,485	(2,419)	(765)
Reclassification adjustment for net amortization of actuarial gain/loss included in net income as a componet of net periodic cost (benefit) , tax expense (benefit)	1,284	1,117	1,181
Total defined-benefit post-retirement benefit plans, tax expense (benefit)	4,769	(1,302)	416
Total other comprehensive income, tax expense (benefit)	(44,034)	65,287	87,980
Securities available for sale and transferred securities, change in net unrealized gain/loss during the period, net of tax amount	(182,770)	337,590	330,659
Securities available for sale and transferred securities. change in net unrealized gain on securities transfers to held-to-maturity, net of tax amount	(767)	(992)	(1,021)
Securities available for sale and securities transferred, reclassification adjustment for net (gains) losses included in net income, net of tax amount	(55)	(86,101)	(231)
Total securities available for sale and transferred securities, net of tax amount	(183,592)	250,497	329,407
Change in the net actuarial gain/loss, net of tax amount	13,108	(9,099)	(2,879)
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	4,832	4,202	4,442
Total defined-benefit post-retirement benefit plans, net of tax amount	17,940	(4,897)	1,563
Other comprehensive income (loss), net of tax	$ (165,652)	$ 245,600	$ 330,970

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, 2021	Dec. 31, 2020	Dec. 31, 2019
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance	$ 512,970
Net other comprehensive income (loss) during period	(165,652)	$ 245,600	$ 330,970
Ending Balance	347,318	512,970
Available-for-sale Securities [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance	563,801	313,304	(16,103)
Other comprehensive income (loss) before reclassification	(183,537)	336,598	329,638
Reclassification of amounts included in net income	(55)	(86,101)	(231)
Net other comprehensive income (loss) during period	(183,592)	250,497	329,407
Ending Balance	380,209	563,801	313,304
Defined Benefit Plans [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance	(50,831)	(45,934)	(47,497)
Other comprehensive income (loss) before reclassification	13,108	(9,099)	(2,879)
Reclassification of amounts included in net income	4,832	4,202	4,442
Net other comprehensive income (loss) during period	17,940	(4,897)	1,563
Ending Balance	(32,891)	(50,831)	(45,934)
AOCI Attributable to Parent [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance	512,970	267,370	(63,600)
Other comprehensive income (loss) before reclassification	(170,429)	327,499	326,759
Reclassification of amounts included in net income	4,777	(81,899)	4,211
Net other comprehensive income (loss) during period	(165,652)	245,600	330,970
Ending Balance	$ 347,318	$ 512,970	$ 267,370

Derivative Financial Instrume_3

Derivative Financial Instruments (Narrative) (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Derivative [Line Items]
Weighted-average strike rate for outstanding interest rate caps	3.26%
Approximate credit exposure related to swaps with bank customers	$ 118,300
Cash collateral on deposit with other financial institutions	110,300	$ 74,000
Interest Rate Swaps With Upstream Financial Institution Counterparties [Member]
Derivative [Line Items]
Approximate credit exposure related to swaps with bank customers	19,700
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
Not Designated as Hedging Instrument [Member] | Put Option [Member] | Other Non-Interest Income [Member]
Derivative [Line Items]
Gains included in other income from the sale of put options	$ 0	$ 5,992	$ 750

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, 2021	Dec. 31, 2020
Designated as Hedging Instrument [Member] | Financial Institution Counterparties Loan Lease Interest Rate Swaps Liabilities [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability, Notional Amount	$ 2,426	$ 3,724
Estimated Fair Value	(34)	(134)
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	247,592	0
Estimated Fair Value	1,207	0
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	928,756	1,173,173
Estimated Fair Value	(19,142)	(33,812)
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	270,431	356,601
Estimated Fair Value	3,239	1,241
Not Designated as Hedging Instrument [Member] | Customer Counterparties Loan Lease Interest Rate Swaps Assets [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Notional Amount	928,756	1,173,173
Estimated Fair Value	39,864	84,424
Not Designated as Hedging Instrument [Member] | Customer Counterparties Loan Lease Interest Rate Swaps Liabilities [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability, Notional Amount	247,592	0
Estimated Fair Value	(2,846)	0
Not Designated as Hedging Instrument [Member] | Customer Counterparties Loan Lease Interest Rate Caps Liabilities [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability, Notional Amount	270,431	356,601
Estimated Fair Value	$ (3,239)	$ (1,241)

Derivative Financial Instrume_5

Derivative Financial Instruments (Schedule of Weighted-Average Rates Paid and Received for Interest Rate Swaps Outstanding) (Detail)	Dec. 31, 2021
Weighted Average Interest Rate Paid [Member]
Short-duration Insurance Contracts, Discounted Liabilities [Line Items]
Fair Value Hedge Loan Lease Interest Rate Swaps	2.48%
Weighted-Average Interest Rate Received [Member]
Short-duration Insurance Contracts, Discounted Liabilities [Line Items]
Fair Value Hedge Loan Lease Interest Rate Swaps	0.10%
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	3.73%
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	1.90%
Customer Counterparties [Member] | Weighted Average Interest Rate Paid [Member]
Short-duration Insurance Contracts, Discounted Liabilities [Line Items]
Non-hedging interest rate swaps - customer counterparties	1.90%
Customer Counterparties [Member] | Weighted-Average Interest Rate Received [Member]
Short-duration Insurance Contracts, Discounted Liabilities [Line Items]
Non-hedging interest rate swaps - customer counterparties	3.73%

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, 2021USD ($)MMBTUbbl	Dec. 31, 2020USD ($)bblMMBTU
Financial Institution Counterparties [Member] | Oil Commodity Derivative [Member]
Derivative Instruments [Line Items]
Oil/Natural Gas Derivative Assets Notional Amount | bbl	4,809	3,056
Oil/Natural Gas Derivative Assets, Estimated Fair Value	$ 14,721	$ 8,341
Oil/Natural Gas Derivative Liabilities Notional Amount | bbl	7,032	6,391
Oil/Natural Gas Derivative Liabilities, Estimated Fair Value	$ (73,594)	$ (32,112)
Financial Institution Counterparties [Member] | Natural Gas Commodity Derivative [Member]
Derivative Instruments [Line Items]
Oil/Natural Gas Derivative Assets Notional Amount | MMBTU	15,947	9,281
Oil/Natural Gas Derivative Assets, Estimated Fair Value	$ 4,143	$ 1,529
Oil/Natural Gas Derivative Liabilities Notional Amount | MMBTU	29,446	15,079
Oil/Natural Gas Derivative Liabilities, Estimated Fair Value	$ (21,249)	$ (3,265)
Customer Counterparties [Member] | Oil Commodity Derivative [Member]
Derivative Instruments [Line Items]
Oil/Natural Gas Derivative Assets Notional Amount | bbl	7,046	6,391
Oil/Natural Gas Derivative Assets, Estimated Fair Value	$ 74,437	$ 32,670
Oil/Natural Gas Derivative Liabilities Notional Amount | bbl	4,796	3,056
Oil/Natural Gas Derivative Liabilities, Estimated Fair Value	$ (14,294)	$ (8,264)
Customer Counterparties [Member] | Natural Gas Commodity Derivative [Member]
Derivative Instruments [Line Items]
Oil/Natural Gas Derivative Assets Notional Amount | MMBTU	29,446	17,636
Oil/Natural Gas Derivative Assets, Estimated Fair Value	$ 21,456	$ 3,451
Oil/Natural Gas Derivative Liabilities Notional Amount | MMBTU	15,947	6,724
Oil/Natural Gas Derivative Liabilities, Estimated Fair Value	$ (4,124)	$ (1,458)

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, 2021USD ($)	Dec. 31, 2021EUR (€)	Dec. 31, 2021CAD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2020EUR (€)	Dec. 31, 2020CAD ($)
Financial Institution Counterparties [Member] | Other Assets [Member] | Not Designated as Hedging Instrument [Member]
Derivative Counter Party [Line Items]
Forward Contracts - Assets, Notional Amount		€ 1,900	$ 658		€ 0	$ 0
Customer Counterparties [Member] | Other Assets [Member] | Not Designated as Hedging Instrument [Member]
Derivative Counter Party [Line Items]
Forward Contracts - Assets, Notional Amount		0	$ 658		0	$ 0
Customer Counterparties [Member] | Other Liabilities [Member] | Not Designated as Hedging Instrument [Member]
Derivative Counter Party [Line Items]
Forward Contracts Liability, Notional Amount | €		€ 1,900			€ 0
GBP Foreign Exchange Forward [Member] | Financial Institution Counterparties [Member]
Derivative Counter Party [Line Items]
Forward Contracts - Assets Estimated Fair Value	$ 29			$ 0
GBP Foreign Exchange Forward [Member] | Customer Counterparties [Member]
Derivative Counter Party [Line Items]
Forward Contracts - Assets Estimated Fair Value	0			0
Forward Contracts, Liability Estimated Fair Value	(55)			0
Foreign Exchange Forward [Member] | Financial Institution Counterparties [Member]
Derivative Counter Party [Line Items]
Forward Contracts - Assets Estimated Fair Value	0			0
Foreign Exchange Forward [Member] | Customer Counterparties [Member]
Derivative Counter Party [Line Items]
Forward Contracts - Assets Estimated Fair Value	$ 4			$ 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, 2021	Dec. 31, 2020	Dec. 31, 2019
Interest Income on Loans [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount included in income or expense	$ (91)	$ (111)	$ 86
Other Non-Interest Expense [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount included in income or expense	$ 10	$ 9	$ 0

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, 2021	Dec. 31, 2020	Dec. 31, 2019
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	$ 4,285	$ 3,413	$ 2,005
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	(1)	1	(1)
Commodity Contract [Member] | Other Non-Interest Income [Member]
Other Non Interest Income Non Hedging Interest Rate Derivatives [Line Items]
Amount included in income or expense	4,052	1,768	503
Foreign Exchange Contract [Member] | Other Non-Interest Income [Member]
Other Non Interest Income Non Hedging Interest Rate Derivatives [Line Items]
Amount included in income or expense	39	28	51
Put Option [Member] | Other Non-Interest Income [Member]
Other Non Interest Income Non Hedging Interest Rate Derivatives [Line Items]
Amount included in income or expense	$ 0	$ 5,992	$ 750

Balance Sheet Offsetting - Fina

Balance Sheet Offsetting - Financial Instruments Eligible for Offset Consolidated Balance Sheet (Detail) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Gross Amount Recognized, Derivative, Financial Assets	$ 23,339	$ 11,111
Gross Amount Offset, Derivatives, Financial Assets	0	0
Net Amount Recognized, Derivative, Financial Assets	23,339	11,111
Gross Amount Recognized, Resell Agreements, Financial Assets	7,903	0
Gross Amount Offset, Resell Agreements, Financial Assets	0	0
Net Amount Recognized, Resell Agreements, Financial Assets	7,903	0
Gross Amount Recognized, Financial Assets	31,242	11,111
Gross Amount Offset, Financial Assets	0	0
Net Amount Recognized, Financial Assets	31,242	11,111
Gross Amount Recognized, Derivative, Financial Liabilities	114,019	69,323
Gross Amount Offset, Derivative, Financial Liabilities	0	0
Net Amount Recognized, Derivative, Financial Liabilities	114,019	69,323
Gross Amount Recognized, Repurchase Agreements, Financial Liabilities	2,740,799	2,068,147
Gross Amount Offset, Repurchase Agreements, Financial Liabilities	0	0
Net Amount Recognized, Repurchase Agreements, Financial Liabilities	2,740,799	2,068,147
Gross Amount Recognized, Financial Liabilities	2,854,818	2,137,470
Gross Amount Offset, Financial Liabilities	0	0
Net Amount Recognized, Financial Liabilities	2,854,818	2,137,470
Loan Lease Interest Rate Swaps And Caps [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Gross Amount Recognized, Derivative, Financial Assets	4,446	1,241
Gross Amount Offset, Derivatives, Financial Assets	0	0
Net Amount Recognized, Derivative, Financial Assets	4,446	1,241
Commodity Swaps And Options [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Gross Amount Recognized, Derivative, Financial Assets	18,864	9,870
Gross Amount Offset, Derivatives, Financial Assets	0	0
Net Amount Recognized, Derivative, Financial Assets	18,864	9,870
Gross Amount Recognized, Derivative, Financial Liabilities	94,843	35,377
Gross Amount Offset, Derivative, Financial Liabilities	0	0
Net Amount Recognized, Derivative, Financial Liabilities	94,843	35,377
Foreign Currency Forward Contracts [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Gross Amount Recognized, Derivative, Financial Assets	29
Gross Amount Offset, Derivatives, Financial Assets	0
Net Amount Recognized, Derivative, Financial Assets	29
Gross Amount Recognized, Derivative, Financial Liabilities		0
Gross Amount Offset, Derivative, Financial Liabilities		0
Net Amount Recognized, Derivative, Financial Liabilities		0
Loan Lease Interest Rate Swaps [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Gross Amount Recognized, Derivative, Financial Liabilities	19,176	33,946
Gross Amount Offset, Derivative, Financial Liabilities	0	0
Net Amount Recognized, Derivative, Financial Liabilities	$ 19,176	$ 33,946

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, 2021	Dec. 31, 2020
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Net Amount Recognized, Derivatives, Financial Assets	$ 23,339	$ 11,111
Gross Amounts Not Offset, Financial Instruments, Total Derivatives, Financial Assets	(23,339)	(11,111)
Gross Amounts Not Offset, Collateral, Derivatives, Financial Assets	0	0
Net Amount, Derivatives, Financial Assets	0	0
Net Amount Recognized, Resell Agreements, Financial Assets	7,903	0
Gross Amounts Not Offset, Financial Instruments, Resell Agreements, Financial Assets	0	0
Gross Amounts Not Offset, Collateral, Resell Agreements, Financial Assets	(7,903)	0
Net Amount, Resell Agreements, Financial Assets	0	0
Net Amount Recognized, Total Financial Assets	31,242	11,111
Gross Amounts Not Offset, Collateral, Financial Assets	(7,903)	0
Net Amount, Financial Assets	0	0
Net Amount Recognized, Derivatives, Financial Liabilities	114,019	69,323
Gross Amounts Not Offset, Financial Instruments, Total Derivatives, Financial Liabilities	(23,339)	(11,111)
Gross Amounts Not offset, Collateral, Derivatives, Financial Liabilities	(90,573)	(57,031)
Net Amount, Derivatives, Financial Liabilities	107	1,181
Net Amount Recognized, Repurchase Agreements, Financial Liabilities	2,740,799	2,068,147
Gross Amounts Not Offset, Financial Instruments, Repurchase Agreements, Financial Liabilities	0	0
Gross Amounts Not Offset, Collateral, Repurchase Agreements, Financial Liabilities	(2,740,799)	(2,068,147)
Net Amount, Repurchase Agreements, Financial Liabilities	0	0
Net Amount Recognized, Financial Liabilities	2,854,818	2,137,470
Gross Amounts Not Offset, Collateral, Financial Liabilities	(2,831,372)	(2,125,178)
Net Amount, Financial Liabilities	107	1,181
Counterparty A [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Net Amount Recognized, Derivatives, Financial Assets	6	2
Gross Amounts Not Offset, Financial Instruments, Total Derivatives, Financial Assets	(6)	(2)
Gross Amounts Not Offset, Collateral, Derivatives, Financial Assets	0	0
Net Amount, Derivatives, Financial Assets	0	0
Net Amount Recognized, Derivatives, Financial Liabilities	3,870	6,430
Gross Amounts Not Offset, Financial Instruments, Total Derivatives, Financial Liabilities	(6)	(2)
Gross Amounts Not offset, Collateral, Derivatives, Financial Liabilities	(3,864)	(6,428)
Net Amount, Derivatives, Financial Liabilities	0	0
Counterparty B [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Net Amount Recognized, Derivatives, Financial Assets	7,655	5,838
Gross Amounts Not Offset, Financial Instruments, Total Derivatives, Financial Assets	(7,655)	(5,838)
Gross Amounts Not Offset, Collateral, Derivatives, Financial Assets	0	0
Net Amount, Derivatives, Financial Assets	0	0
Net Amount Recognized, Derivatives, Financial Liabilities	28,130	20,722
Gross Amounts Not Offset, Financial Instruments, Total Derivatives, Financial Liabilities	(7,655)	(5,838)
Gross Amounts Not offset, Collateral, Derivatives, Financial Liabilities	(20,475)	(14,700)
Net Amount, Derivatives, Financial Liabilities	0	184
Counterparty C [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Net Amount Recognized, Derivatives, Financial Liabilities	9	71
Gross Amounts Not Offset, Financial Instruments, Total Derivatives, Financial Liabilities	0	0
Gross Amounts Not offset, Collateral, Derivatives, Financial Liabilities	(9)	(71)
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	15,678	5,271
Gross Amounts Not Offset, Financial Instruments, Total Derivatives, Financial Assets	(15,678)	(5,271)
Gross Amounts Not Offset, Collateral, Derivatives, Financial Assets	0	0
Net Amount, Derivatives, Financial Assets	0	0
Net Amount Recognized, Derivatives, Financial Liabilities	82,010	42,100
Gross Amounts Not Offset, Financial Instruments, Total Derivatives, Financial Liabilities	(15,678)	(5,271)
Gross Amounts Not offset, Collateral, Derivatives, Financial Liabilities	(66,225)	(35,832)
Net Amount, Derivatives, Financial Liabilities	$ 107	$ 997

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, 2021	Dec. 31, 2020
Remaining Contractual Maturity of the Securities Sold Under Agreement to Repurchase [Line Items]
Remaining contractual maturity of the agreements overnight and continuous	$ 2,740,799	$ 2,068,147
Remaining contractual maturity of the agreements up to 30 Days	0	0
Remaining contractual maturity of the agreements 30 to 90 Days	0	0
Remaining contractual maturity of the agreements greater than 90 Days	0	0
Remaining contractual maturity of the agreements total	2,740,799	2,068,147
Securities Sold under Agreements to Repurchase, Gross	2,740,799	2,068,147
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	1,342,591	692,860
Remaining contractual maturity of the agreements up to 30 Days	0	0
Remaining contractual maturity of the agreements 30 to 90 Days	0	0
Remaining contractual maturity of the agreements greater than 90 Days	0	0
Remaining contractual maturity of the agreements total	1,342,591	692,860
Residential Mortgage Backed Securities [Member]
Remaining Contractual Maturity of the Securities Sold Under Agreement to Repurchase [Line Items]
Remaining contractual maturity of the agreements overnight and continuous	1,398,208	1,375,287
Remaining contractual maturity of the agreements up to 30 Days	0	0
Remaining contractual maturity of the agreements 30 to 90 Days	0	0
Remaining contractual maturity of the agreements greater than 90 Days	0	0
Remaining contractual maturity of the agreements total	$ 1,398,208	$ 1,375,287

Fair Value Measurements (Narrat

Fair Value Measurements (Narrative) (Detail) $ in Thousands	Dec. 31, 2021USD ($)	Dec. 31, 2020Grade
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments using fair value measurement option | $	$ 0
Commodity Swaps And Options [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Weighted Average Risk Grade | Grade		14
Weighted average loss severity in the event of default on commodity swaps		10.00%

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, 2021	Dec. 31, 2020
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale, at estimated fair value	$ 13,924,628	$ 10,437,565
Trading account securities	25,162	24,456
Derivative assets:	23,339	11,111
Derivative liabilities:	114,019	69,323
Interest Rate Swaps Caps And Floors [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets:	44,310	85,665
Derivative liabilities:	25,261	35,187
Commodity Swaps And Options [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets:	114,757	45,991
Derivative liabilities:	113,261	45,099
Foreign Exchange Forward [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets:	33
Derivative liabilities:	55
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	2,179,433	1,119,633
Trading account securities	24,237	23,996
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	4,066,265	1,987,679
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	7,636,571	7,287,902
Trading account securities	925	460
Other Investments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale, at estimated fair value	42,359	42,351
Level 1 [Member] | Foreign Exchange Forward [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets:	33
Derivative liabilities:	55
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	2,179,433	1,119,633
Trading account securities	24,237	23,996
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:	44,310	85,665
Derivative liabilities:	25,261	35,187
Level 2 [Member] | Commodity Swaps And Options [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets:	114,757	45,535
Derivative liabilities:	113,261	45,099
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	4,066,265	1,987,679
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	7,636,571	7,287,902
Trading account securities	925	460
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	42,359	42,351
Level 3 [Member] | Commodity Swaps And Options [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets:	0	456
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	2,179,433	1,119,633
Trading account securities	24,237	23,996
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	4,066,265	1,987,679
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	7,636,571	7,287,902
Trading account securities	925	460
Other Investments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale, at estimated fair value	$ 42,359	$ 42,351

Fair Value Measurements (Impair

Fair Value Measurements (Impaired Loans Remeasured and Reported at Fair Value of Underlying Collateral) (Detail) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying value before allocations	$ 1,333	$ 1,559	$ 2,354
Specific valuation allowance allocations		(450)	(383)
Reversal of specific valuation allowance allocations	214
Fair value	1,547	1,109	1,971
Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying value before allocations	16,074	34,302	65,176
Specific valuation allowance allocations	(5,178)	(11,151)	(18,019)
Fair value	$ 10,896	$ 23,151	$ 47,157

Fair Value Measurements (Forecl

Fair Value Measurements (Foreclosed Assets Remeasured and Reported at Fair Value) (Detail) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Foreclosed Assets Remeasured at Initial Recognition Carrying Value Of Foreclosed Assets Prior To Remeasurement	$ 0	$ 0	$ 1,348
Foreclosed Assets Remeasured at Initial Recognition Charge Offs Recognized In Allowance For Loan Losses	0	0	(76)
Fair Value of Foreclosed Assets Remeasured at Initial Recognition	0	0	1,272
Foreclosed Assets Remeasured Subsequent to Initial Recognition Carrying Value Of Foreclosed Assets Prior To Remeasurement	14	328	0
Foreclosed Assets Remeasured Subsequent to initial Recognition Write Downs Included In Other Non Interest Expense	(14)	(231)	0
Fair Value of Foreclosed Assets Remeasured Subsequent to Initial Recognition	$ 0	$ 97	$ 0

Fair Value Measurements (Estima

Fair Value Measurements (Estimated Fair Values of Financial Instruments) (Detail) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	$ 16,583,000	$ 10,288,853	$ 3,788,181	$ 3,955,779
Securities held to maturity	1,749,179	1,945,673
Loans, net	16,087,731	17,218,132
Deposits	42,695,696	35,015,761
Federal funds purchased	25,925	48,850
Repurchase agreements	2,740,799	2,068,147
Junior subordinated deferrable interest debentures	123,011	136,357
Subordinated notes	99,178	99,021
Carrying Amount [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	16,583,000	10,288,853
Securities held to maturity	1,749,179	1,945,673
Cash surrender value of life insurance policies	190,139	189,984
Accrued interest receivable	179,111	181,432
Deposits	42,695,696	35,015,761
Federal funds purchased	25,925	48,850
Repurchase agreements	2,740,799	2,068,147
Junior subordinated deferrable interest debentures	123,011	136,357
Subordinated notes	99,178	99,021
Accrued interest payable	3,026	8,127
Carrying Amount [Member] | Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans, net	16,087,731	17,218,132
Estimated Fair Value [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	16,583,000	10,288,853
Securities held to maturity	1,809,143	2,052,896
Cash surrender value of life insurance policies	190,139	189,984
Accrued interest receivable	179,111	181,432
Deposits	41,343,426	35,018,185
Federal funds purchased	25,925	48,850
Repurchase agreements	2,740,799	2,068,147
Junior subordinated deferrable interest debentures	123,712	137,115
Subordinated notes	111,430	115,717
Accrued interest payable	3,026	8,127
Estimated Fair Value [Member] | Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans, net	$ 16,079,454	$ 17,390,683

Operating Segments Operating Se

Operating Segments Operating Segments - Additional Information (Details) $ in Billions	12 Months Ended
	Dec. 31, 2021USD ($)Segment	Dec. 31, 2020USD ($)Segment	Dec. 31, 2019USD ($)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 | $	$ 43.3	$ 38.6	$ 37.8

Operating Segments (Summary of

Operating Segments (Summary of Operating Results by Segment) (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Segment Reporting Information [Line Items]
Net interest income (expense)	$ 984,867	$ 976,001	$ 1,004,005
Credit loss expense	63	241,230	33,759
Non-interest income	386,728	465,454	363,902
Non-interest expense	881,994	848,904	834,679
Income before income taxes	489,538	351,321	499,469
Income tax expense (benefit)	46,459	20,170	55,870
Net income	443,079	331,151	443,599
Preferred stock dividends	7,157	2,016	8,063
Redemption of preferred stock	0	5,514	0
Net income available to common shareholders	435,922	323,621	435,536
Revenues from (expenses to) external customers	1,371,595	1,441,455	1,367,907
Average assets	45,983,000	37,961,000	32,086,000
Banking [Member]
Segment Reporting Information [Line Items]
Net interest income (expense)	989,870	981,441	1,010,368
Credit loss expense	54	241,230	33,758
Non-interest income	220,662	321,136	218,447
Non-interest expense	753,719	718,519	703,121
Income before income taxes	456,759	342,828	491,936
Income tax expense (benefit)	41,483	20,347	55,520
Net income	415,276	322,481	436,416
Preferred stock dividends	0	0	0
Redemption of preferred stock		0
Net income available to common shareholders	415,276	322,481	436,416
Revenues from (expenses to) external customers	1,210,532	1,302,577	1,228,815
Average assets	45,903,000	37,892,000	32,019,000
Frost Wealth Advisors [Member]
Segment Reporting Information [Line Items]
Net interest income (expense)	2,138	2,776	4,001
Credit loss expense	9	0	1
Non-interest income	167,442	145,268	145,905
Non-interest expense	122,972	123,630	124,622
Income before income taxes	46,599	24,414	25,283
Income tax expense (benefit)	9,786	5,127	5,308
Net income	36,813	19,287	19,975
Preferred stock dividends	0	0	0
Redemption of preferred stock		0
Net income available to common shareholders	36,813	19,287	19,975
Revenues from (expenses to) external customers	169,580	148,044	149,906
Average assets	70,000	59,000	56,000
Non-Banks [Member]
Segment Reporting Information [Line Items]
Net interest income (expense)	(7,141)	(8,216)	(10,364)
Credit loss expense	0	0	0
Non-interest income	(1,376)	(950)	(450)
Non-interest expense	5,303	6,755	6,936
Income before income taxes	(13,820)	(15,921)	(17,750)
Income tax expense (benefit)	(4,810)	(5,304)	(4,958)
Net income	(9,010)	(10,617)	(12,792)
Preferred stock dividends	7,157	2,016	8,063
Redemption of preferred stock		5,514
Net income available to common shareholders	(16,167)	(18,147)	(20,855)
Revenues from (expenses to) external customers	(8,517)	(9,166)	(10,814)
Average assets	$ 10,000	$ 10,000	$ 11,000

Condensed Financial Statement_3

Condensed Financial Statements of Parent Company (Schedule of Condensed Balance Sheets) (Detail) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Condensed Financial Statements, Captions [Line Items]
Cash	$ 555,778	$ 529,454
Resell agreements	7,903	0
Cash and cash equivalents	16,583,000	10,288,853	$ 3,788,181	$ 3,955,779
Total assets	50,878,490	42,391,317
Junior subordinated deferrable interest debentures, net of unamortized issuance costs	123,011	136,357
Subordinated notes, net of unamortized issuance costs	99,178	99,021
Accrued interest payable and other liabilities	754,326	730,165
Total liabilities	46,438,935	38,098,301
Shareholders’ Equity	4,439,555	4,293,016	$ 3,911,668	$ 3,368,917
Total liabilities and shareholders’ equity	50,878,490	42,391,317
Parent Company [Member]
Condensed Financial Statements, Captions [Line Items]
Cash	471,875	381,240
Resell agreements	0	0
Cash and cash equivalents	471,875	381,240
Investment in subsidiaries	4,222,288	4,155,619
Accrued interest receivable and other assets	2,228	2,164
Total assets	4,696,391	4,539,023
Junior subordinated deferrable interest debentures, net of unamortized issuance costs	123,011	136,357
Subordinated notes, net of unamortized issuance costs	99,178	99,021
Accrued interest payable and other liabilities	34,647	10,629
Total liabilities	256,836	246,007
Shareholders’ Equity	4,439,555	4,293,016
Total liabilities and shareholders’ equity	$ 4,696,391	$ 4,539,023

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, 2021	Dec. 31, 2020	Dec. 31, 2019
Condensed Financial Statements, Captions [Line Items]
Total interest income	$ 1,008,769	$ 1,021,035	$ 1,133,785
Interest expense	23,902	45,034	129,780
Other	171,457	166,310	180,665
Income before income taxes and equity in undistributed earnings of subsidiaries	489,538	351,321	499,469
Income tax benefit	(46,459)	(20,170)	(55,870)
Net income	443,079	331,151	443,599
Preferred stock dividends	7,157	2,016	8,063
Redemption of preferred stock	0	5,514	0
Net income available to common shareholders	435,922	323,621	435,536
Parent Company [Member]
Condensed Financial Statements, Captions [Line Items]
Dividend income paid by Frost Bank	219,386	298,884	234,531
Dividend income paid by non-banks	473	736	1,822
Interest and other income	101	446	2,868
Total interest income	219,960	300,066	239,221
Interest expense	7,141	8,216	10,363
Salaries and employee benefits	1,499	1,581	1,551
Other	5,867	6,833	7,033
Total expenses	14,507	16,630	18,947
Income before income taxes and equity in undistributed earnings of subsidiaries	205,453	283,436	220,274
Income tax benefit	4,899	5,406	5,135
Equity in undistributed earnings of subsidiaries	232,727	42,309	218,190
Net income	443,079	331,151	443,599
Preferred stock dividends	7,157	2,016	8,063
Redemption of preferred stock	0	5,514	0
Net income available to common shareholders	$ 435,922	$ 323,621	$ 435,536

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, 2021	Dec. 31, 2020	Dec. 31, 2019
Condensed Financial Statements, Captions [Line Items]
Net income	$ 443,079	$ 331,151	$ 443,599
Stock-based compensation	12,753	13,918	15,946
Net tax benefit from stock-based compensation	7,877	852	2,447
Net cash provided by (used in) operating activities	648,293	524,243	634,090
Net cash provided by (used in) investing activities	(2,525,015)	(1,631,047)	(1,386,750)
Principal payments on long-term borrowings	(13,403)
Redemption of Series A preferred stock	0	(150,000)	0
Proceeds from issuance of Series B preferred stock	0	145,452	0
Proceeds from stock option exercises	54,417	12,557	20,770
Purchase of treasury stock	(3,864)	(15,785)	(68,793)
Treasury stock issued to 401(k) stock purchase plan	1,749	10,307	0
Cash dividends paid on preferred stock	(7,157)	(2,016)	(8,063)
Cash dividends paid on common stock	(188,786)	(180,584)	(177,006)
Net cash provided by (used in) financing activities	8,170,869	7,607,476	585,062
Parent Company [Member]
Condensed Financial Statements, Captions [Line Items]
Net income	443,079	331,151	443,599
Equity in undistributed earnings of subsidiaries	(232,727)	(42,309)	(218,190)
Stock-based compensation	700	770	780
Net tax benefit from stock-based compensation	278	370	240
Net change in other assets and other liabilities	23,890	(8,937)	22,216
Net cash provided by (used in) operating activities	235,220	281,045	248,645
Redemption of investment in non-bank subsidiary	406	0	0
Net cash provided by (used in) investing activities	406	0	0
Principal payments on long-term borrowings	(13,403)	0	0
Redemption of Series A preferred stock	0	(150,000)	0
Proceeds from issuance of Series B preferred stock	0	145,452	0
Proceeds from stock option exercises	54,417	12,557	20,770
Proceeds from stock-based compensation activities of subsidiaries	12,053	13,148	15,166
Purchase of treasury stock	(3,864)	(15,785)	(68,793)
Treasury stock issued to 401(k) stock purchase plan	1,749	10,307	0
Cash dividends paid on preferred stock	(7,157)	(2,016)	(8,063)
Cash dividends paid on common stock	(188,786)	(180,584)	(177,006)
Net cash provided by (used in) financing activities	(144,991)	(166,921)	(217,926)
Net change in cash and cash equivalents	90,635	114,124	30,719
Cash and cash equivalents at beginning of year	381,240	267,116	236,397
Cash and cash equivalents at end of year	$ 471,875	$ 381,240	$ 267,116

Accounting Standards Updates Ac

Accounting Standards Updates Accounting Standards Update (Narrative) (Details) - USD ($) $ in Thousands	Jan. 01, 2020	Dec. 31, 2019	Jan. 01, 2019	Dec. 31, 2018
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect of accounting change		$ (29,252)		$ (14,672)
Retained Earnings [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect of accounting change	$ (29,300)	$ (29,252)	$ (14,700)	$ (14,672)