Cullen/Frost Bankers (CFR) 10-Q 28 Apr 22 2022 Q1 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - $ / shares	3 Months Ended
	Mar. 31, 2022	Apr. 21, 2022	Dec. 31, 2021
Entity Information [Line Items]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Mar. 31, 2022
Document Transition Report	false
Entity File Number	001-13221
Entity Registrant Name	Cullen/Frost Bankers, Inc.
Entity Incorporation, State or Country Code	TX
Entity Tax Identification Number	74-1751768
Entity Address, Address Line One	111 W. Houston Street,
Entity Address, City or Town	San Antonio,
Entity Address, State or Province	TX
Entity Address, Postal Zip Code	78205
City Area Code	(210)
Local Phone Number	220-4011
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		64,097,017
Common stock, par value	$ 0.01		$ 0.01
Amendment Flag	false
Document Fiscal Year Focus	2022
Document Fiscal Period Focus	Q1
Entity Central Index Key	0000039263
Current Fiscal Year End Date	--12-31
Common Stock [Member] | NEW YORK STOCK EXCHANGE, INC. [Member]
Entity Information [Line Items]
Title of 12(b) Security	Common Stock, $.01 Par Value
Trading Symbol	CFR
Security Exchange Name	NYSE
Series B Preferred Stock [Member] | NEW YORK STOCK EXCHANGE, INC. [Member]
Entity Information [Line Items]
Title of 12(b) Security	Depositary Shares, each representing a 1/40th interest in a share of 4.450% Non-Cumulative Perpetual Preferred Stock, Series B
Trading Symbol	CFR.PrB
Security Exchange Name	NYSE

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Assets:
Cash and due from banks	$ 772,095	$ 555,778
Interest-bearing deposits	13,684,988	15,985,244
Federal funds sold	0	34,075
Resell agreements	0	7,903
Total cash and cash equivalents	14,457,083	16,583,000
Securities held to maturity, net of allowance for credit losses of $158 at March 31, 2022 and $158 at December 31, 2021	1,665,465	1,749,179
Securities available for sale, at estimated fair value	16,184,539	13,924,628
Trading account securities	29,518	25,162
Loans, net of unearned discounts	16,542,537	16,336,397
Less: Allowance for credit losses on loans	(246,835)	(248,666)
Net loans	16,295,702	16,087,731
Premises and equipment, net	1,046,410	1,050,331
Goodwill	654,952	654,952
Other intangible assets, net	720	866
Cash surrender value of life insurance policies	189,471	190,139
Accrued interest receivable and other assets	772,191	612,502
Total assets	51,296,051	50,878,490
Liabilities:
Non-interest-bearing demand deposits	18,114,430	18,423,018
Interest-bearing deposits	26,316,499	24,272,678
Total deposits	44,430,929	42,695,696
Federal funds purchased	35,200	25,925
Repurchase agreements	1,842,618	2,740,799
Junior subordinated deferrable interest debentures, net of unamortized issuance costs	123,026	123,011
Subordinated notes, net of unamortized issuance costs	99,217	99,178
Accrued interest payable and other liabilities	988,769	754,326
Total liabilities	47,519,759	46,438,935
Shareholders’ Equity:
Preferred stock, par value $0.01 per share; 10,000,000 shares authorized; 150,000 Series B shares ($1,000 liquidation preference) issued at March 31, 2022 and December 31, 2021	145,452	145,452
Common stock, par value $0.01 per share; 210,000,000 shares authorized; 64,236,306 shares issued at March 31, 2022 and December 31, 2021	642	642
Additional paid-in capital	1,012,033	1,009,921
Retained earnings	3,002,642	2,956,966
Accumulated other comprehensive income (loss), net of tax	(371,790)	347,318
Treasury stock, at cost; 142,099 shares at March 31, 2022 and 250,070 shares at December 31, 2021	(12,687)	(20,744)
Total shareholders’ equity	3,776,292	4,439,555
Total liabilities and shareholders’ equity	$ 51,296,051	$ 50,878,490

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - USD ($)	Mar. 31, 2022	Dec. 31, 2021
Securities, held-to-maturity, allowance for credit loss	$ 158,000	$ 158,000
Preferred stock liquidation preference value	$ 150,000,000
Common stock, par value	$ 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	142,099	250,070
Series B Preferred Stock [Member]
Preferred stock, par value	$ 0.01	$ 0.01
Preferred stock, shares authorized	10,000,000	10,000,000
Preferred stock, shares issued	150,000	150,000
Preferred stock liquidation preference value	$ 1,000	$ 1,000

Consolidated Statements of Inco

Consolidated Statements of Income - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Interest income:
Loans, including fees	$ 149,977	$ 167,483
Securities:
Taxable	43,058	20,028
Tax-exempt	56,866	56,663
Interest-bearing deposits	6,343	2,433
Federal funds sold	13	3
Resell agreements	4	1
Total interest income	256,261	246,611
Interest expense:
Deposits	4,912	3,517
Federal funds purchased	12	8
Repurchase agreements	518	395
Junior subordinated deferrable interest debentures	584	646
Subordinated notes	1,164	1,164
Total interest expense	7,190	5,730
Net interest income	249,071	240,881
Credit loss expense	0	63
Net interest income after credit loss expense	249,071	240,818
Non-interest income:
Trust and investment management fees	38,656	35,314
Service charges on deposit accounts	22,740	19,993
Insurance commissions and fees	16,608	17,313
Interchange and card transaction fees	4,226	4,093
Other charges, commissions and fees	9,627	8,304
Net gain (loss) on securities transactions	0	0
Other	9,533	8,219
Total non-interest income	101,390	93,236
Non-interest expense:
Salaries and wages	111,329	93,458
Employee benefits	24,220	22,536
Net occupancy	27,411	26,051
Technology, furniture and equipment	29,157	28,016
Deposit insurance	3,633	2,928
Intangible amortization	146	202
Other	42,836	36,951
Total non-interest expense	238,732	210,142
Income before income taxes	111,729	123,912
Income taxes	12,627	7,897
Net income	99,102	116,015
Preferred stock dividends	1,669	2,151
Net income available to common shareholders	$ 97,433	$ 113,864
Earnings per common share:
Basic	$ 1.51	$ 1.78
Diluted	$ 1.50	$ 1.77

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Net income	$ 99,102	$ 116,015
Other comprehensive income (loss), before tax:
Change in net unrealized gain/loss on securities available for sale during the period	(910,795)	(159,779)
Change in net unrealized gain on securities transferred to held to maturity	(209)	(259)
Reclassification adjustment for net (gains) losses included in net income	0	0
Total securities available for sale and transferred securities, before tax amount	(911,004)	(160,038)
Defined-benefit post-retirement benefit plans:
Reclassification adjustment for net amortization of actuarial gain/loss included in net income as a component of net periodic cost (benefit)	741	1,529
Total defined-benefit post-retirement benefit plans	741	1,529
Other comprehensive income (loss), before tax	(910,263)	(158,509)
Deferred tax expense (benefit)	(191,155)	(33,287)
Other comprehensive income (loss), net of tax	(719,108)	(125,222)
Comprehensive income (loss)	$ (620,006)	$ (9,207)

Consolidated Statements of Chan

Consolidated Statements of Changes in Shareholders' Equity - USD ($) $ in Thousands	Total	Preferred Stock [Member]	Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	AOCI Attributable to Parent [Member]	Treasury Stock [Member]
Total shareholders’ equity at beginning of period at Dec. 31, 2020	$ 4,293,016	$ 145,452	$ 642	$ 997,168	$ 2,750,723	$ 512,970	$ (113,939)
Net income	116,015				116,015
Other comprehensive income (loss)	(125,222)					(125,222)
Stock option exercises/stock unit conversions (115,430 shares YTD in 2022 and 513,824 shares YTD in 2021)	29,397				(21,342)		50,739
Stock compensation expense recognized in earnings	2,526			2,526
Purchase of treasury stock (7,459 shares YTD in 2022 and 11,625 shares YTD in 2021)	(1,288)						(1,288)
Treasury stock issued to the 401(k) stock purchase plan (18,555 shares YTD in 2021 )	1,749				(57)		1,806
Cash dividends – preferred stock (approximately $11.13 per share which is equivalent to approximately $0.28 per depository share YTD in 2022 and $14.34 per share which is equivalent to approximately $0.36 per depository share YTD in 2021)	(2,151)				(2,151)
Cash dividends – common stock ($0.75 per share YTD in 2022 and $0.72 per share YTD in 2021)	(46,124)				(46,124)
Total shareholders’ equity at end of period at Mar. 31, 2021	4,267,918	145,452	642	999,694	2,797,064	387,748	(62,682)
Total shareholders’ equity at beginning of period at Dec. 31, 2021	4,439,555	145,452	642	1,009,921	2,956,966	347,318	(20,744)
Net income	99,102				99,102
Other comprehensive income (loss)	(719,108)					(719,108)
Stock option exercises/stock unit conversions (115,430 shares YTD in 2022 and 513,824 shares YTD in 2021)	5,739				(3,314)		9,053
Stock compensation expense recognized in earnings	2,112			2,112
Purchase of treasury stock (7,459 shares YTD in 2022 and 11,625 shares YTD in 2021)	(996)						(996)
Treasury stock issued to the 401(k) stock purchase plan (18,555 shares YTD in 2021 )	0
Cash dividends – preferred stock (approximately $11.13 per share which is equivalent to approximately $0.28 per depository share YTD in 2022 and $14.34 per share which is equivalent to approximately $0.36 per depository share YTD in 2021)	(1,669)				(1,669)
Cash dividends – common stock ($0.75 per share YTD in 2022 and $0.72 per share YTD in 2021)	(48,443)				(48,443)
Total shareholders’ equity at end of period at Mar. 31, 2022	$ 3,776,292	$ 145,452	$ 642	$ 1,012,033	$ 3,002,642	$ (371,790)	$ (12,687)

Consolidated Statements of Ch_2

Consolidated Statements of Changes in Shareholders' Equity (Parenthetical) - $ / shares	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Statement of Stockholders' Equity [Abstract]
Stock option exercise/stock unit conversions (115,430 shares YTD during 2022 and 513,824 shares YTD during 2021)	115,430	513,824
Purchase of treasury stock (7,459 shares during 2022 and 11,625 shares during 2021)	7,459	11,625
Treasury stock issued to the 401(k) stock purchase plan (18,555 shares YTD in 2021 )		18,555
Cash dividend - preferred stock (Approximately $11.13 per share YTD in 2022 and $14.34 per share YTD during 2021)	$ 11.13	$ 14.34
Cash dividend - Preferred Stock Dividends equivalent Per depositary Share Declared ($0.28 YTD during 2022 and $0.36 YTD during 2021)	0.28	0.36
Cash dividends - common stock ($0.75 per share YTD during 2022 and $0.72 per share YTD during 2021)	$ 0.75	$ 0.72

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Operating Activities:
Net income	$ 99,102	$ 116,015
Adjustments to reconcile net income to net cash from operating activities:
Credit loss expense	0	63
Deferred tax expense (benefit)	(432)	4,172
Accretion of loan discounts	(2,945)	(3,425)
Securities premium amortization (discount accretion), net	27,654	30,598
Net (gain) loss on securities transactions	0	0
Depreciation and amortization	17,551	16,941
Net (gain) loss on sale/write-down of assets/foreclosed assets	130	(134)
Stock-based compensation	2,112	2,526
Net tax benefit from stock-based compensation	1,244	3,136
Earnings on life insurance policies	(533)	(740)
Net change in:
Trading account securities	139	(2,153)
Lease right-of-use assets	5,970	5,889
Accrued interest receivable and other assets	(55,232)	73,164
Accrued interest payable and other liabilities	238,065	(26,287)
Net cash from operating activities	332,825	219,765
Investing Activities:
Securities held-to-maturity - Purchases	(31,545)	0
Securities held to maturity: Maturities, calls and principal repayments	111,211	120,029
Securities available for sale:
Purchases	(3,356,279)	(455,091)
Sales	0	0
Maturities, calls and principal repayments	236,032	351,612
Net change in loans	(209,490)	(406,836)
Benefits received on life insurance policies	1,201	968
Proceeds from sales of premises and equipment	1	3
Purchases of premises and equipment	(12,374)	(12,814)
Proceeds from sales of repossessed properties	1,543	100
Net cash from investing activities	(3,259,700)	(402,029)
Financing Activities:
Net change in deposits	1,735,233	1,909,419
Net change in short-term borrowings	(888,906)	(193,573)
Proceeds from stock option exercises	5,739	29,397
Purchase of treasury stock	(996)	(1,288)
Cash dividends paid on preferred stock	(1,669)	(2,151)
Cash dividends paid on common stock	(48,443)	(46,124)
Net cash from financing activities	800,958	1,695,680
Net change in cash and cash equivalents	(2,125,917)	1,513,416
Cash and cash equivalents at beginning of period	16,583,000	10,288,853
Cash and cash equivalents at end of period	$ 14,457,083	$ 11,802,269

Significant Accounting Policies

Significant Accounting Policies	3 Months Ended
	Mar. 31, 2022
Accounting Policies [Abstract]
Significant Accounting Policies	Significant Accounting Policies Nature of Operations. Cullen/Frost Bankers, Inc. (“Cullen/Frost”) is a financial holding company and a bank holding company headquartered in San Antonio, Texas that provides, through its subsidiaries, a broad array of products and services throughout numerous Texas markets. The terms “Cullen/Frost,” “the Corporation,” “we,” “us” and “our” mean Cullen/Frost Bankers, Inc. and its subsidiaries, when appropriate. In addition to general commercial and consumer banking, other products and services offered include trust and investment management, insurance, brokerage, mutual funds, leasing, treasury management, capital markets advisory and item processing. Basis of Presentation. The consolidated financial statements in this Quarterly Report on Form 10-Q include the accounts of Cullen/Frost and all other entities in which Cullen/Frost has a controlling financial interest. All significant intercompany balances and transactions have been eliminated in consolidation. The accounting and financial reporting policies we follow conform, in all material respects, to accounting principles generally accepted in the United States and to general practices within the financial services industry. The consolidated financial statements in this Quarterly Report on Form 10-Q have not been audited by an independent registered public accounting firm, but in the opinion of management, reflect all adjustments necessary for a fair presentation of our financial position and results of operations. All such adjustments were of a normal and recurring nature. The consolidated financial statements have been prepared in accordance with accounting principles generally accepted in the United States for interim financial information and with the instructions to Form 10-Q adopted by the Securities and Exchange Commission (“SEC”). Accordingly, the financial statements do not include all of the information and footnotes required by accounting principles generally accepted in the United States for complete financial statements and should be read in conjunction with our consolidated financial statements, and notes thereto, for the year ended December 31, 2021, included in our Annual Report on Form 10-K filed with the SEC on February 4, 2022 (the “2021 Form 10-K”). Operating results for the interim periods disclosed herein are not necessarily indicative of the results that may be expected for a full year or any future period. Use of Estimates . The preparation of financial statements in conformity with accounting principles generally accepted in the United States requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements. Actual results could differ from those estimates. The allowance for loan losses and the fair values of financial instruments and the status of contingencies are particularly subject to change. Cash Flow Reporting . Additional cash flow information was as follows: Three Months Ended 2022 2021 Cash paid for interest $ 8,069 $ 9,719 Cash paid for income taxes — — Significant non-cash transactions: Unsettled securities transactions 78,769 21,957 Right-of-use lease assets obtained in exchange for lessee operating lease liabilities 4,013 1,326 Treasury stock issued to 401(k) stock purchase plan — 1,749

Securities

Securities	3 Months Ended
	Mar. 31, 2022
Investments, Debt and Equity Securities [Abstract]
Securities	Securities Securities - Held to Maturity. A summary of the amortized cost, fair value and allowance for credit losses related to securities held to maturity as of March 31, 2022 and December 31, 2021 is presented below. Amortized Gross Gross Estimated Allowance Net March 31, 2022 Residential mortgage-backed securities $ 526,969 $ — $ 17,519 $ 509,450 $ — $ 526,969 States and political subdivisions 1,137,154 3,622 11,717 1,129,059 (158) 1,136,996 Other 1,500 — 16 1,484 — 1,500 Total $ 1,665,623 $ 3,622 $ 29,252 $ 1,639,993 $ (158) $ 1,665,465 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 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 $252.0 million and $642.3 million at March 31, 2022 and December 31, 2021, respectively. Accrued interest receivable on held-to-maturity securities totaled $10.0 million and $18.4 million at March 31, 2022 and December 31, 2021, respectively and is included in accrued interest receivable and other assets in the accompanying consolidated balance sheets. From time to time, we have reclassified certain securities from available for sale to held to maturity. The net unamortized, unrealized gain remaining on transferred securities included in accumulated other comprehensive income in the accompanying balance sheet totaled $2.3 million ($1.8 million, net of tax) at March 31, 2022 and $2.5 million ($2.0 million, net of tax) at December 31, 2021. This amount will be amortized out of accumulated other comprehensive income over the remaining life of the underlying securities as an adjustment of the yield on those securities. The following table summarizes Moody's and/or Standard & Poor's bond ratings for our portfolio of held-to-maturity securities issued by States and political subdivisions and other securities as of March 31, 2022 and December 31, 2021: States and Political Subdivisions Not Guaranteed or Pre-Refunded Guaranteed by the Texas PSF Pre-Refunded Total Other March 31, 2022 Aaa/AAA $ 91,034 $ 467,039 $ 471,183 $ 1,029,256 $ — Aa/AA 107,898 — — 107,898 — Not rated — — — — 1,500 Total $ 198,932 $ 467,039 $ 471,183 $ 1,137,154 $ 1,500 December 31, 2021 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 The following table details activity in the allowance for credit losses on held-to-maturity securities during the three months ended March 31, 2022 and 2021. Three Months Ended 2022 2021 Beginning balance $ 158 $ 160 Credit loss expense (benefit) — (2) Ending balance $ 158 $ 158 Securities - Available for Sale. A summary of the amortized cost, fair value and allowance for credit losses related to securities available for sale as of March 31, 2022 and December 31, 2021 is presented below. Amortized Gross Gross Allowance Estimated March 31, 2022 U.S. Treasury $ 3,658,506 $ 1,883 $ 152,643 $ — $ 3,507,746 Residential mortgage-backed securities 5,696,906 7,246 328,113 — 5,376,039 States and political subdivisions 7,218,821 135,206 95,634 — 7,258,393 Other 42,361 — — — 42,361 Total $ 16,616,594 $ 144,335 $ 576,390 $ — $ 16,184,539 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 All mortgage-backed securities included in the above table were issued by U.S. government agencies and corporations. At March 31, 2022, 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 75.7% 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 $4.8 billion and $5.8 billion at March 31, 2022 and December 31, 2021, respectively. Accrued interest receivable on available-for-sale securities totaled $80.8 million and $120.5 million at March 31, 2022 and December 31, 2021, respectively, and is included in accrued interest receivable and other assets in the accompanying consolidated balance sheets. The table below summarizes, as of March 31, 2022, securities available for sale in an unrealized loss position for which an allowance for credit losses has not been recorded, aggregated by type of security and length of time in a continuous unrealized loss position. Less than 12 Months More than 12 Months Total Estimated Unrealized Estimated Unrealized Estimated Unrealized U.S. Treasury $ 3,220,375 $ 152,643 $ — $ — $ 3,220,375 $ 152,643 Residential mortgage-backed securities 4,583,657 286,421 402,940 41,692 4,986,597 328,113 States and political subdivisions 1,233,614 93,136 13,602 2,498 1,247,216 95,634 Total $ 9,037,646 $ 532,200 $ 416,542 $ 44,190 $ 9,454,188 $ 576,390 As of March 31, 2022, no allowance for credit losses has been recognized on available for sale securities in an unrealized loss position as management does not believe any of the securities are impaired due to reasons of credit quality. This is based upon our analysis of the underlying risk characteristics, including credit ratings, and other qualitative factors related to our available for sale securities and in consideration of our historical credit loss experience and internal forecasts. The issuers of these securities continue to make timely principal and interest payments under the contractual terms of the securities. Furthermore, management does not have the intent to sell any of the securities classified as available for sale in the table above and believes that it is more likely than not that we will not have to sell any such securities before a recovery of cost. The unrealized losses are due to increases in market interest rates over the yields available at the time the underlying securities were purchased. The fair value is expected to recover as the securities approach their maturity date or repricing date or if market yields for such investments decline. Contractual Maturities. The following table summarizes the maturity distribution schedule of securities held to maturity and securities available for sale as of March 31, 2022. 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 $ 16 $ — $ 514,842 $ 12,111 $ 526,969 States and political subdivisions 429,852 118,516 56,735 532,051 1,137,154 Other — 1,500 — — 1,500 Total $ 429,868 $ 120,016 $ 571,577 $ 544,162 $ 1,665,623 Estimated Fair Value Residential mortgage-backed securities $ 16 $ — $ 498,078 $ 11,356 $ 509,450 States and political subdivisions 431,961 119,698 56,973 520,427 1,129,059 Other — 1,484 — — 1,484 Total $ 431,977 $ 121,182 $ 555,051 $ 531,783 $ 1,639,993 Available For Sale Amortized Cost U. S. Treasury $ — $ 2,033,995 $ 1,432,731 $ 191,780 $ 3,658,506 Residential mortgage-backed securities 102 12,917 19,060 5,664,827 5,696,906 States and political subdivisions 194,416 1,563,829 888,489 4,572,087 7,218,821 Other — — — — 42,361 Total $ 194,518 $ 3,610,741 $ 2,340,280 $ 10,428,694 $ 16,616,594 Estimated Fair Value U. S. Treasury $ — $ 1,978,865 $ 1,350,553 $ 178,328 $ 3,507,746 Residential mortgage-backed securities 103 13,212 19,327 5,343,397 5,376,039 States and political subdivisions 197,231 1,603,985 899,602 4,557,575 7,258,393 Other — — — — 42,361 Total $ 197,334 $ 3,596,062 $ 2,269,482 $ 10,079,300 $ 16,184,539 Sales of Securities. No held to maturity or available for sale securities were sold during the three months ended March 31, 2022 or 2021. Premiums and Discounts . Premium amortization and discount accretion included in interest income on securities was as follows: Three Months Ended 2022 2021 Premium amortization $ (29,060) $ (31,235) Discount accretion 1,406 637 Net (premium amortization) discount accretion $ (27,654) $ (30,598) Trading Account Securities. Trading account securities, at estimated fair value, were as follows: March 31, December 31, U.S. Treasury $ 23,939 $ 24,237 States and political subdivisions 5,579 925 Total $ 29,518 $ 25,162 Net gains and losses on trading account securities were as follows: Three Months Ended 2022 2021 Net gain on sales transactions $ 340 $ 109 Net mark-to-market gains (losses) (168) (69) Net gain (loss) on trading account securities $ 172 $ 40

Loans

Loans	3 Months Ended
	Mar. 31, 2022
Receivables [Abstract]
Loans	Loans Loans were as follows: March 31, December 31, Commercial and industrial $ 5,584,117 $ 5,364,954 Energy: Production 820,107 878,436 Service 113,708 105,901 Other 102,764 93,455 Total energy 1,036,579 1,077,792 Paycheck Protection Program 207,669 428,882 Commercial real estate: Commercial mortgages 5,918,011 5,867,062 Construction 1,421,878 1,304,271 Land 458,510 405,277 Total commercial real estate 7,798,399 7,576,610 Consumer real estate: Home equity loans 321,842 324,157 Home equity lines of credit 544,822 519,098 Other 566,961 567,535 Total consumer real estate 1,433,625 1,410,790 Total real estate 9,232,024 8,987,400 Consumer and other 482,148 477,369 Total loans $ 16,542,537 $ 16,336,397 Concentrations of Credit. Most of our lending activity occurs within the State of Texas, including the four largest metropolitan areas of Austin, Dallas/Ft. Worth, Houston and San Antonio, as well as other markets. The majority of our loan portfolio consists of commercial and industrial and commercial real estate loans. As of March 31, 2022, there were no concentrations of loans related to any single industry in excess of 10% of total loans. The largest industry concentration was related to the energy industry, which totaled 6.3% of total loans (also 6.3% excluding PPP loans). Unfunded commitments to extend credit and standby letters of credit issued to customers in the energy industry totaled $862.2 million and $76.0 million, respectively, as of March 31, 2022. Foreign Loans. We have U.S. dollar denominated loans and commitments to borrowers in Mexico. The outstanding balance of these loans and the unfunded amounts available under these commitments were not significant at March 31, 2022 or December 31, 2021. Related Party Loans . In the ordinary course of business, we have granted loans to certain directors, executive officers and their affiliates (collectively referred to as “related parties”). Such loans totaled $346.5 million at March 31, 2022 and $350.5 million at December 31, 2021. Accrued Interest Receivable. Accrued interest receivable on loans totaled $39.5 million and $40.0 million at March 31, 2022 and December 31, 2021, 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. Non-accrual loans, segregated by class of loans, were as follows: March 31, 2022 December 31, 2021 Total Non-Accrual Non-Accrual with No Credit Loss Allowance Total Non-Accrual Non-Accrual with No Credit Loss Allowance Commercial and industrial $ 16,693 $ 6,135 $ 22,582 $ 4,701 Energy 12,271 6,912 14,433 8,533 Paycheck Protection Program — — — — Commercial real estate: Buildings, land and other 19,003 17,005 15,297 13,817 Construction 583 583 948 — Consumer real estate 416 114 440 138 Consumer and other — — 13 13 Total $ 48,966 $ 30,749 $ 53,713 $ 27,202 The following table presents non-accrual loans as of March 31, 2022 by class and year of origination. 2021 2020 2019 2018 2017 Prior Revolving Loans Revolving Loans Converted to Term Total Commercial and industrial $ — $ 478 $ 4,101 $ 3,910 $ 1,552 $ 1,033 $ 2,038 $ 3,581 $ 16,693 Energy — — — 5,039 1,137 — 5,997 98 12,271 Paycheck Protection Program — — — — — — — — — Commercial real estate: Buildings, land and other — 8,407 296 1,199 394 2,932 — 5,775 19,003 Construction — — 583 — — — — — 583 Consumer real estate — — — — — 390 — 26 416 Consumer and other — — — — — — — — — Total $ — $ 8,885 $ 4,980 $ 10,148 $ 3,083 $ 4,355 $ 8,035 $ 9,480 $ 48,966 Had non-accrual loans performed in accordance with their original contract terms, we would have recognized additional interest income, net of tax, of approximately $407 thousand for the three months ended March 31, 2022, and approximately $453 thousand for the three months ended March 31, 2021. An age analysis of past due loans (including both accruing and non-accruing loans), segregated by class of loans, as of March 31, 2022 was as follows: Loans Loans Total Current Total Accruing Commercial and industrial $ 13,016 $ 8,042 $ 21,058 $ 5,563,059 $ 5,584,117 $ 4,166 Energy — 6,382 6,382 1,030,197 1,036,579 287 Paycheck Protection Program 671 8,377 9,048 198,621 207,669 8,377 Commercial real estate: Buildings, land and other 21,542 11,546 33,088 6,343,433 6,376,521 1,046 Construction 1,988 — 1,988 1,419,890 1,421,878 — Consumer real estate 4,210 2,409 6,619 1,427,006 1,433,625 2,103 Consumer and other 6,393 593 6,986 475,162 482,148 593 Total $ 47,820 $ 37,349 $ 85,169 $ 16,457,368 $ 16,542,537 $ 16,572 Troubled Debt Restructurings . There were no loans modified as troubled debt restructurings during the three months ended March 31, 2022 and 2021. 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. Modifications have not generally had a significant impact on our determination of the allowance for credit losses on loans. Information as of or for the three months ended March 31, 2022 and 2021 related to loans restructured during the last twelve months is set forth in the following table. March 31, 2022 March 31, 2021 Restructured loans past due in excess of 90 days at period-end: Number of loans 2 2 Dollar amount of loans $ 572 $ 1,392 Charge-offs of restructured loans: Recognized on previously restructured loans 723 1,433 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 set forth in our 2021 Form 10-K. We monitor portfolio credit quality by the weighted-average risk grade of each class of commercial loan. Individual relationship managers, under the oversight of credit administration, review updated financial information for all pass grade loans to reassess the risk grade on at least an annual basis. When a loan has a risk grade of 9, it is still considered a pass grade loan; however, it is considered to be on management’s “watch list,” where a significant risk-modifying action is anticipated in the near term. When a loan has a risk grade of 10 or higher, a special assets officer monitors the loan on an on-going basis. The following tables present weighted-average risk grades for all commercial loans, by class and year of origination/renewal as of March 31, 2022. Paycheck Protection Program (“PPP”) loans are excluded as such loans are fully guaranteed by the Small Business Administration (“SBA”). 2022 2021 2020 2019 2018 Prior Revolving Loans Revolving Loans Converted to Term Total W/A Risk Grade Commercial and industrial Risk grades 1-8 $ 836,152 $ 894,663 $ 592,780 $ 305,667 $ 160,622 $ 243,869 $ 2,255,878 $ 44,778 $ 5,334,409 6.18 Risk grade 9 4,702 34,513 6,562 11,434 21,841 8,319 54,008 4,721 146,100 9.00 Risk grade 10 3,500 22,084 6,527 1,039 4,007 578 13,899 1,198 52,832 10.00 Risk grade 11 — 1,926 6,672 9,679 1,697 2,200 5,958 5,951 34,083 11.00 Risk grade 12 — 478 2,644 3,510 1,488 619 941 2,015 11,695 12.00 Risk grade 13 — — 1,457 400 64 414 1,097 1,566 4,998 13.00 $ 844,354 $ 953,664 $ 616,642 $ 331,729 $ 189,719 $ 255,999 $ 2,331,781 $ 60,229 $ 5,584,117 6.34 W/A risk grade 6.16 6.87 6.17 6.75 7.00 5.80 6.14 7.82 6.34 Energy Risk grades 1-8 $ 279,051 $ 125,435 $ 7,519 $ 8,444 $ 4,068 $ 5,665 $ 509,657 $ 59,424 $ 999,263 5.71 Risk grade 9 1,425 103 508 1,407 96 — 5,668 43 9,250 9.00 Risk grade 10 — — 90 580 351 — — 515 1,536 10.00 Risk grade 11 9,097 265 512 3,256 951 178 — — 14,259 11.00 Risk grade 12 — — — 3,708 58 — 3,215 98 7,079 12.00 Risk grade 13 — — — 1,331 1,079 — 2,782 — 5,192 13.00 $ 289,573 $ 125,803 $ 8,629 $ 18,726 $ 6,603 $ 5,843 $ 521,322 $ 60,080 $ 1,036,579 5.89 W/A risk grade 6.36 5.77 7.73 9.34 9.24 7.16 5.41 6.31 5.89 2022 2021 2020 2019 2018 Prior Revolving Loans Revolving Loans Converted to Term Total W/A Risk Grade Commercial real estate: Buildings, land, other Risk grades 1-8 $ 607,883 $ 1,554,611 $ 1,113,230 $ 809,206 $ 498,477 $ 1,057,840 $ 72,704 $ 96,924 $ 5,810,875 6.89 Risk grade 9 6,163 20,766 108,943 53,448 23,459 45,034 5,516 2,618 265,947 9.00 Risk grade 10 46,125 22,716 7,310 66,821 24,539 57,602 — — 225,113 10.00 Risk grade 11 — 260 1,293 7,328 6,788 36,699 3,215 — 55,583 11.00 Risk grade 12 — 8,081 296 1,199 394 2,932 — 5,775 18,677 12.00 Risk grade 13 — 326 — — — — — — 326 13.00 $ 660,171 $ 1,606,760 $ 1,231,072 $ 938,002 $ 553,657 $ 1,200,107 $ 81,435 $ 105,317 $ 6,376,521 7.14 W/A risk grade 7.08 7.22 7.04 7.32 7.27 6.97 7.06 6.99 7.14 Construction Risk grades 1-8 $ 202,413 $ 634,897 $ 195,127 $ 141,510 $ 636 $ 1,842 $ 207,182 $ 3,666 $ 1,387,273 6.96 Risk grade 9 171 28,069 5,359 — — 423 — — 34,022 9.00 Risk grade 10 — — — — — — — — — 10.00 Risk grade 11 — — — — — — — — — 11.00 Risk grade 12 — — 583 — — — — — 583 12.00 Risk grade 13 — — — — — — — — — 13.00 $ 202,584 $ 662,966 $ 201,069 $ 141,510 $ 636 $ 2,265 $ 207,182 $ 3,666 $ 1,421,878 7.01 W/A risk grade 6.83 7.28 6.38 7.98 6.22 7.17 6.28 8.00 7.01 Total commercial real estate $ 862,755 $ 2,269,726 $ 1,432,141 $ 1,079,512 $ 554,293 $ 1,202,372 $ 288,617 $ 108,983 $ 7,798,399 7.11 W/A risk grade 7.02 7.24 6.95 7.41 7.27 6.97 6.50 7.03 7.11 In the table above, certain energy loans are reported as 2022 originations and have risk grades of 11 or higher. These loans were, for the most part, first originated in various years prior to 2022 but were renewed in the current year. The following tables present weighted average risk grades for all commercial loans by class as of December 31, 2021. Refer to our 2021 Form 10-K for details of these loans by year of origination/renewal. Commercial and Industrial Energy Commercial Real Estate - Buildings, Land and Other Commercial Real Estate - Construction Total Commercial Real Estate W/A Risk Grade Loans W/A Risk Grade Loans W/A Risk Grade Loans W/A Risk Grade Loans W/A Risk Grade Loans Risk grades 1-8 6.01 $ 5,063,847 5.78 $ 1,008,370 6.91 $ 5,574,922 6.99 $ 1,262,200 6.92 $ 6,837,122 Risk grade 9 9.00 187,870 9.00 36,622 9.00 321,533 9.00 41,123 9.00 362,656 Risk grade 10 10.00 59,137 10.00 1,773 10.00 269,447 10.00 — 10.00 269,447 Risk grade 11 11.00 31,518 11.00 16,594 11.00 91,140 11.00 — 11.00 91,140 Risk grade 12 12.00 12,535 12.00 8,953 12.00 15,097 12.00 748 12.00 15,845 Risk grade 13 13.00 10,047 13.00 5,480 13.00 200 13.00 200 13.00 400 Total 6.22 $ 5,364,954 6.06 $ 1,077,792 7.22 $ 6,272,339 7.06 $ 1,304,271 7.19 $ 7,576,610 Information about the payment status of consumer loans, segregated by portfolio segment and year of origination, as of March 31, 2022 was as follows: 2022 2021 2020 2019 2018 Prior Revolving Loans Revolving Loans Converted to Term Total Consumer real estate: Past due 30-89 days $ — $ 303 $ 55 $ 465 $ 309 $ 1,587 $ 60 $ 1,431 $ 4,210 Past due 90 or more days — — 4 — 297 854 1,004 250 2,409 Total past due — 303 59 465 606 2,441 1,064 1,681 6,619 Current loans 51,321 322,814 225,921 86,664 48,481 149,677 533,182 8,946 1,427,006 Total $ 51,321 $ 323,117 $ 225,980 $ 87,129 $ 49,087 $ 152,118 $ 534,246 $ 10,627 $ 1,433,625 Consumer and other: Past due 30-89 days $ 1,470 $ 385 $ 53 $ 69 $ 54 $ 24 $ 2,344 $ 1,994 $ 6,393 Past due 90 or more days — 499 — 23 — 13 — 58 593 Total past due 1,470 884 53 92 54 37 2,344 2,052 6,986 Current loans 21,692 34,798 13,127 4,936 2,207 2,520 371,266 24,616 475,162 Total $ 23,162 $ 35,682 $ 13,180 $ 5,028 $ 2,261 $ 2,557 $ 373,610 $ 26,668 $ 482,148 Revolving loans that converted to term during the three months ended March 31, 2022 and 2021 were as follows: Three Months Ended March 31, 2021 2020 Commercial and industrial $ 5,763 $ 11,843 Energy — 5,928 Commercial real estate: Buildings, land and other 47 23,303 Construction 3,666 — Consumer real estate 858 793 Consumer and other 4,222 3,861 Total $ 14,556 $ 45,728 In assessing the general economic conditions in the State of Texas, management monitors and tracks the Texas Leading Index (“TLI”), which is produced by the Federal Reserve Bank of Dallas. The TLI, the components of which are more fully described in our 2021 Form 10-K, totaled 141.2 at March 31, 2022 and 135.9 at December 31, 2021. A higher TLI value implies more favorable economic conditions. Allowance For Credit Losses - Loans. The allowance for credit losses on loans is a contra-asset valuation account, calculated in accordance with ASC 326, that is deducted from the amortized cost basis of loans to present the net amount expected to be collected. The amount of the allowance represents management's best estimate of current expected credit losses on loans considering available information, from internal and external sources, relevant to assessing collectibility over the loans' contractual terms, adjusted for expected prepayments when appropriate. Credit loss expense related to loans reflects the totality of actions taken on all loans for a particular period including any necessary increases or decreases in the allowance related to changes in credit loss expectations associated with specific loans or pools of loans. Portions of the allowance may be allocated for specific credits; however, the entire allowance is available for any credit that, in management’s judgment, should be charged off. While management utilizes its best judgment and information available, the ultimate appropriateness of the allowance is dependent upon a variety of factors beyond our control, including the performance of our loan portfolio, the economy, changes in interest rates and the view of the regulatory authorities toward loan classifications. Our allowance methodology is more fully described in our 2021 Form 10-K. The following table presents details of the allowance for credit losses on loans segregated by loan portfolio segment as of March 31, 2022 and December 31, 2021. No allowance for credit losses has been recognized for PPP loans as such loans are fully guaranteed by the SBA. March 31, 2022 Commercial Energy Commercial Consumer Consumer Total Modeled expected credit losses $ 46,635 $ 5,971 $ 17,110 $ 6,260 $ 7,634 $ 83,610 Q-Factor and other qualitative adjustments 33,916 4,260 111,518 63 1,440 151,197 Specific allocations 6,475 5,191 326 36 — 12,028 Total $ 87,026 $ 15,422 $ 128,954 $ 6,359 $ 9,074 $ 246,835 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 The following table details activity in the allowance for credit losses on loans by portfolio segment for the three months ended March 31, 2022 and 2021. Allocation of a portion of the allowance to one category of loans does not preclude its availability to absorb losses in other categories. No allowance for credit losses has been recognized for PPP loans as such loans are fully guaranteed by the SBA. Commercial Energy Commercial Consumer Consumer Total Three months ended: March 31, 2022 Beginning balance $ 72,091 $ 17,217 $ 144,936 $ 6,585 $ 7,837 $ 248,666 Credit loss expense (benefit) 17,561 (2,044) (15,609) (26) 4,582 4,464 Charge-offs (3,455) (371) (702) (231) (5,771) (10,530) Recoveries 829 620 329 31 2,426 4,235 Net charge-offs (2,626) 249 (373) (200) (3,345) (6,295) Ending balance $ 87,026 $ 15,422 $ 128,954 $ 6,359 $ 9,074 $ 246,835 March 31, 2021 Beginning balance $ 73,843 $ 39,553 $ 134,892 $ 7,926 $ 6,963 $ 263,177 Credit loss expense (benefit) (1,965) (5,801) 8,922 (2,722) 1,566 — Charge-offs (2,189) (1,433) — (284) (4,060) (7,966) Recoveries 1,203 1,153 626 716 2,349 6,047 Net charge-offs (986) (280) 626 432 (1,711) (1,919) Ending balance $ 70,892 $ 33,472 $ 144,440 $ 5,636 $ 6,818 $ 261,258 The following table presents loans that were evaluated for expected credit losses on an individual basis and the related specific allocations, by loan portfolio segment as of March 31, 2022 and December 31, 2021. March 31, 2022 December 31, 2021 Loan Specific Allocations Loan Specific Allocations Commercial and industrial $ 21,529 $ 6,475 $ 24,523 $ 10,536 Energy 11,931 5,191 16,393 5,480 Paycheck Protection Program — — — — Commercial real estate: Buildings, land and other 28,806 326 24,670 200 Construction — — 948 200 Consumer real estate 302 36 303 36 Consumer and other — — — — Total $ 62,568 $ 12,028 $ 66,837 $ 16,452

Goodwill and Other Intangible A

Goodwill and Other Intangible Assets	3 Months Ended
	Mar. 31, 2022
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill and Other Intangible Assets	Goodwill and Other Intangible Assets Goodwill and other intangible assets are presented in the table below. March 31, December 31, Goodwill $ 654,952 $ 654,952 Other intangible assets: Core deposits $ 591 $ 718 Customer relationships 129 148 $ 720 $ 866 The estimated aggregate future amortization expense for intangible assets remaining as of March 31, 2022 is as follows: Remainder of 2022 $ 335 2023 282 2024 87 2025 11 2026 5 Thereafter — $ 720

Deposits

Deposits	3 Months Ended
	Mar. 31, 2022
Disclosure Text Block [Abstract]
Deposits	Deposits Deposits were as follows: March 31, December 31, Non-interest-bearing demand deposits $ 18,114,430 $ 18,423,018 Interest-bearing deposits: Savings and interest checking 12,484,308 11,930,959 Money market accounts 12,490,612 11,228,815 Time accounts 1,341,579 1,112,904 Total interest-bearing deposits 26,316,499 24,272,678 Total deposits $ 44,430,929 $ 42,695,696 The following table presents additional information about our deposits: March 31, December 31, Deposits from foreign sources (primarily Mexico) $ 1,092,302 $ 993,479 Non-interest-bearing public funds deposits 746,097 1,235,026 Interest-bearing public funds deposits 975,511 810,863 Total deposits not covered by deposit insurance 25,213,248 24,125,359 Time deposits not covered by deposit insurance 357,529 238,608

Commitments and Contingencies

Commitments and Contingencies	3 Months Ended
	Mar. 31, 2022
Commitments and Contingencies Disclosure [Abstract]
Commitments Contingencies and Guarantees	Off-Balance-Sheet Arrangements, Commitments, Guarantees and Contingencies Financial Instruments with Off-Balance-Sheet Risk . In the normal course of business, we enter into various transactions, which, in accordance with generally accepted accounting principles are not included in our consolidated balance sheets. We enter into these transactions to meet the financing needs of our customers. As more fully discussed in our 2021 Form 10-K, these transactions include commitments to extend credit and standby letters of credit, which involve, to varying degrees, elements of credit risk and interest rate risk in excess of the amounts recognized in the consolidated balance sheets. We minimize our exposure to loss under these commitments by subjecting them to credit approval and monitoring procedures. Financial instruments with off-balance-sheet risk were as follows: March 31, December 31, Commitments to extend credit $ 10,356,196 $ 10,420,142 Standby letters of credit 236,798 238,690 Deferred standby letter of credit fees 1,704 2,072 Allowance For Credit Losses - Off-Balance-Sheet Credit Exposures. The allowance for credit losses on off-balance-sheet credit exposures is a liability account, calculated in accordance with ASC 326, representing expected credit losses over the contractual period for which we are exposed to credit risk resulting from a contractual obligation to extend credit. No allowance is recognized if we have the unconditional right to cancel the obligation. Off-balance-sheet credit exposures primarily consist of amounts available under outstanding lines of credit and letters of credit detailed in the table above. The amount of the allowance represents management's best estimate of expected credit losses on commitments expected to be funded over the contractual life of the commitment. Our allowance methodology is more fully described in our 2021 Form 10-K. The following table details activity in the allowance for credit losses on off-balance-sheet credit exposures. Three Months Ended 2022 2021 Beginning balance $ 50,314 $ 44,152 Credit loss expense (benefit) (4,464) 65 Ending balance $ 45,850 $ 44,217 Lease Commitments . We lease certain office facilities and office equipment under operating leases. The components of total lease expense were as follows: Three Months Ended 2022 2021 Amortization of lease right-of-use assets $ 8,105 $ 8,283 Short-term lease expense 613 204 Non-lease components (including taxes, insurance, common maintenance, etc.) 3,020 3,004 Total $ 11,738 $ 11,491 Right-of-use lease assets totaled $279.5 million at March 31, 2022 and $281.4 million at December 31, 2021 and are reported as a component of premises and equipment on our accompanying consolidated balance sheets. The related lease liabilities totaled $311.8 million at March 31, 2022 and $313.4 million at December 31, 2021 and are reported as a component of accrued interest payable and other liabilities in the accompanying consolidated balance sheets. Lease payments under operating leases that were applied to our operating lease liability totaled $8.0 million during the three months ended March 31, 2022 and $8.1 million during the three months ended March 31, 2021. There has been no significant change in our expected future minimum lease payments since December 31, 2021. See the 2021 Form 10-K for information regarding these commitments.

Capital and Regulatory Matters

Capital and Regulatory Matters	3 Months Ended
	Mar. 31, 2022
Banking Regulation, Common Equity Tier One Risk-Based Capital [Abstract]
Capital and Regulatory Matters	Capital and Regulatory Matters Banks and bank holding companies are subject to various regulatory capital requirements administered by state and federal banking agencies. Capital adequacy guidelines and, additionally for banks, prompt corrective action regulations, involve quantitative measures of assets, liabilities, and certain off-balance-sheet items calculated under regulatory accounting practices. Capital amounts and classifications are also subject to qualitative judgments by regulators about components, risk weighting and other factors. Cullen/Frost’s and Frost Bank’s Common Equity Tier 1 capital (“CET1”) includes common stock and related paid-in capital, net of treasury stock, and retained earnings. In connection with the adoption of the Basel III Capital Rules, we elected to opt-out of the requirement to include most components of accumulated other comprehensive income in CET1. We also elected to exclude the effects of credit loss accounting under CECL from CET1 for a five-year transitional period, as further discussed in our 2021 Form 10-K. This CECL transitional adjustment totaled $46.2 million and $61.6 million at March 31, 2022 and December 31, 2021, respectively. CET1 is reduced by goodwill and other intangible assets, net of associated deferred tax liabilities. Frost Bank's CET1 is also reduced by its equity investment in its financial subsidiary, Frost Insurance Agency (“FIA”). Tier 1 capital includes CET1 and additional Tier 1 capital. For Cullen/Frost, additional Tier 1 capital included $145.5 million of 4.450% non-cumulative perpetual preferred stock at March 31, 2022 and December 31, 2021, the details of which are further discussed below. Frost Bank did not have any additional Tier 1 capital beyond Common Equity Tier 1 at March 31, 2022 or December 31, 2021. Total capital includes Tier 1 capital and Tier 2 capital. Tier 2 capital for both Cullen/Frost and Frost Bank includes a permissible portion of the allowances for credit losses on securities, loans and off-balance-sheet credit exposures. Tier 2 capital for Cullen/Frost also includes the permissible portion of qualified subordinated debt (which decreases 20.0% per year during the final five years of the term of the notes) totaling $80.0 million at March 31, 2022 and $100.0 million at December 31, 2021 and trust preferred securities totaling $120.0 million at both March 31, 2022 and December 31, 2021. The following table presents actual and required capital ratios as of March 31, 2022 and December 31, 2021 for Cullen/Frost and Frost Bank under the Basel III Capital Rules. Capital levels required to be considered well capitalized are based upon prompt corrective action regulations, as amended to reflect the changes under the Basel III Capital Rules. See the 2021 Form 10-K for a more detailed discussion of the Basel III Capital Rules. Actual Minimum Capital Required - Basel III Required to be Capital Ratio Capital Ratio Capital Ratio March 31, 2022 Common Equity Tier 1 to Risk-Weighted Assets Cullen/Frost $ 3,412,080 12.78 % $ 1,869,007 7.00 % $ 1,735,506 6.50 % Frost Bank 3,301,515 12.39 1,865,304 7.00 1,732,068 6.50 Tier 1 Capital to Risk-Weighted Assets Cullen/Frost 3,557,532 13.32 2,269,508 8.50 2,136,007 8.00 Frost Bank 3,301,515 12.39 2,265,012 8.50 2,131,776 8.00 Total Capital to Risk-Weighted Assets Cullen/Frost 3,998,333 14.97 2,803,510 10.50 2,670,009 10.00 Frost Bank 3,542,316 13.29 2,797,956 10.50 2,664,720 10.00 Leverage Ratio Cullen/Frost 3,557,532 7.08 2,010,897 4.00 2,513,621 5.00 Frost Bank 3,301,515 6.57 2,009,767 4.00 2,512,209 5.00 December 31, 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 As of March 31, 2022, capital levels at Cullen/Frost and Frost Bank exceed all capital adequacy requirements under the Basel III Capital Rules. Based on the ratios presented above, capital levels as of March 31, 2022 at Cullen/Frost and Frost Bank exceed the minimum levels necessary to be considered “well capitalized.” Cullen/Frost and Frost Bank are subject to the regulatory capital requirements administered by the Federal Reserve Board and, for Frost Bank, the Federal Deposit Insurance Corporation (“FDIC”). Regulatory authorities can initiate certain mandatory actions if Cullen/Frost or Frost Bank fail to meet the minimum capital requirements, which could have a direct material effect on our financial statements. Management believes, as of March 31, 2022, that Cullen/Frost and Frost Bank meet all capital adequacy requirements to which they are subject. Preferred Stock. Outstanding preferred stock includes 150,000 shares, or $150.0 million in aggregate liquidation preference, of our 4.450% Non-Cumulative Perpetual Preferred Stock, Series B, par value $0.01 and liquidation preference $1,000 per share (“Series B Preferred Stock”). Each share of Series B Preferred Stock issued and outstanding is represented by 40 depositary shares, each representing a 1/40th ownership interest in a share of the Series B Preferred Stock (equivalent to a liquidation preference of $25 per share). The Series B Preferred Stock qualifies as Tier 1 capital for the purposes of the regulatory capital calculations. The net proceeds from the issuance and sale of the Series B Preferred Stock, after deducting $4.5 million of issuance costs including the underwriting discount and professional service fees, among other things, were approximately $145.5 million. Refer to our 2021 Form 10-K for additional details related to our Series B Preferred Stock. Stock Repurchase Plans. From time to time, our board of directors has authorized stock repurchase plans. 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 program, allowing us to repurchase shares of our common stock over a one Dividend Restrictions . In the ordinary course of business, Cullen/Frost is dependent upon dividends from Frost Bank to provide funds for the payment of dividends to shareholders and to provide for other cash requirements, including to repurchase its common stock. Banking regulations may limit the amount of dividends that may be paid. Approval by regulatory authorities is required if the effect of dividends declared would cause the regulatory capital of Frost Bank to fall below specified minimum levels. Approval is also required if dividends declared exceed the net profits for that year combined with the retained net profits for the preceding two years. Under the foregoing dividend restrictions and while maintaining its “well capitalized” status, at March 31, 2022, Frost Bank could pay aggregate dividends of up to $325.0 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.

Derivative Financial Instrument

Derivative Financial Instruments	3 Months Ended
	Mar. 31, 2022
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, swaptions 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 in our 2021 Form 10-K. The notional amounts and estimated fair values of interest rate derivative contracts are presented in the following table. The fair values of interest rate derivative contracts are estimated utilizing internal valuation methods with observable market data inputs, or as determined by the Chicago Mercantile Exchange (“CME”) for centrally cleared derivative contracts. CME rules legally characterize variation margin payments for centrally cleared derivatives as settlements of the derivatives' exposure rather than collateral. As a result, the variation margin payment and the related derivative instruments are considered a single unit of account for accounting and financial reporting purposes. Variation margin, as determined by the CME, is settled daily. As a result, derivative contracts that clear through the CME have an estimated fair value of zero as of March 31, 2022 and December 31, 2021. March 31, 2022 December 31, 2021 Notional Estimated Notional Estimated Derivatives designated as hedges of fair value: Financial institution counterparties: Loan/lease interest rate swaps – assets $ 1,807 $ 1 $ — $ — Loan/lease interest rate swaps – liabilities 280 (3) 2,426 (34) Non-hedging interest rate derivatives: Financial institution counterparties: Loan/lease interest rate swaps – assets 697,834 15,311 247,592 1,207 Loan/lease interest rate swaps – liabilities 447,742 (6,184) 928,756 (19,142) Loan/lease interest rate caps – assets 265,930 8,110 270,431 3,239 Customer counterparties: Loan/lease interest rate swaps – assets 447,742 10,275 928,756 39,864 Loan/lease interest rate swaps – liabilities 697,834 (25,437) 247,592 (2,846) Loan/lease interest rate caps – liabilities 265,930 (8,110) 270,431 (3,239) The weighted-average rates paid and received for interest rate swaps outstanding at March 31, 2022 were as follows: Weighted-Average Interest Interest Interest rate swaps: Fair value hedge loan/lease interest rate swaps 2.11 % 0.26 % Non-hedging interest rate swaps – financial institution counterparties 3.69 2.07 Non-hedging interest rate swaps – customer counterparties 2.07 3.69 The weighted-average strike rate for outstanding interest rate caps was 3.27% at March 31, 2022. Commodity Derivatives. We enter into commodity swaps and option contracts that are not designated as hedging instruments primarily to accommodate the business needs of our customers. Upon the origination of a commodity swap or option contract with a customer, we simultaneously enter into an offsetting contract with a third party financial institution to mitigate the exposure to fluctuations in commodity prices. The notional amounts and estimated fair values of non-hedging commodity swap and option derivative positions outstanding are presented in the following table. We obtain dealer quotations and use internal valuation methods with observable market data inputs to value our commodity derivative positions. March 31, 2022 December 31, 2021 Notional Notional Estimated Notional Estimated Financial institution counterparties: Oil – assets Barrels 2,988 $ 9,735 4,809 $ 14,721 Oil – liabilities Barrels 9,767 (189,416) 7,032 (73,594) Natural gas – assets MMBTUs 14,564 1,813 15,947 4,143 Natural gas – liabilities MMBTUs 27,474 (50,244) 29,446 (21,249) Customer counterparties: Oil – assets Barrels 9,767 190,776 7,046 74,437 Oil – liabilities Barrels 2,988 (9,710) 4,796 (14,294) Natural gas – assets MMBTUs 27,474 50,423 29,446 21,456 Natural gas – liabilities MMBTUs 14,564 (1,811) 15,947 (4,124) 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: March 31, 2022 December 31, 2021 Notional Notional Estimated Notional Estimated Financial institution counterparties: Forward contracts – assets EUR 2,400 $ 18 1,900 $ 29 Forward contracts – assets CAD — — 658 — Forward contracts – liabilities EUR 6,500 (111) — — Forward contracts – liabilities CAD 658 (6) — — Customer counterparties: Forward contracts – assets EUR 6,500 122 — — Forward contracts – assets CAD 658 10 658 4 Forward contracts – liabilities EUR 2,400 (14) 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: Three Months Ended 2022 2021 Commercial loan/lease interest rate swaps: Amount of gain (loss) included in interest income on loans $ (13) $ (28) Amount of (gain) loss included in other non-interest expense 2 (3) As stated above, we enter into non-hedge related derivative positions primarily to accommodate the business needs of our customers. Upon the origination of a derivative contract with a customer, we simultaneously enter into an offsetting derivative contract with a third party financial institution. We recognize immediate income based upon the difference in the bid/ask spread of the underlying transactions with our customers and the third party. Because we act only as an intermediary for our customer, subsequent changes in the fair value of the underlying derivative contracts for the most part offset each other and do not significantly impact our results of operations. Amounts included in the consolidated statements of income related to non-hedge related derivative instruments are presented in the table below. Three Months Ended 2022 2021 Non-hedging interest rate derivatives: Other non-interest income $ 516 $ 1,587 Other non-interest expense — (1) Non-hedging commodity derivatives: Other non-interest income 929 1,154 Non-hedging foreign currency derivatives: Other non-interest income 18 30 Counterparty Credit Risk. Our credit exposure relating to interest rate swaps, commodity swaps/options and foreign currency forward contracts with bank customers was approximately $238.4 million at March 31, 2022. 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 $35.7 million at March 31, 2022. This amount was primarily related to initial margin payments to the CME and excess collateral we

Balance Sheet Offsetting

Balance Sheet Offsetting	3 Months Ended
	Mar. 31, 2022
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Balance Sheet Offsetting	Balance Sheet Offsetting and Repurchase Agreements Balance Sheet Offsetting. Certain financial instruments, including resell and repurchase agreements and derivatives, may be eligible for offset in the consolidated balance sheet and/or subject to master netting arrangements or similar agreements. Our derivative transactions with upstream financial institution counterparties are generally executed under International Swaps and Derivative Association (“ISDA”) master agreements which include “right of set-off” provisions. In such cases there is generally a legally enforceable right to offset recognized amounts and there may be an intention to settle such amounts on a net basis. Nonetheless, we do not generally offset such financial instruments for financial reporting purposes. Information about financial instruments that are eligible for offset in the consolidated balance sheet as of March 31, 2022 is presented in the following tables. Gross Amount Gross Amount Net Amount March 31, 2022 Financial assets: Derivatives: Loan/lease interest rate swaps and caps $ 23,422 $ — $ 23,422 Commodity swaps and options 11,548 — 11,548 Foreign currency forward contracts 18 — 18 Total derivatives 34,988 — 34,988 Resell agreements — — — Total $ 34,988 $ — $ 34,988 Financial liabilities: Derivatives: Loan/lease interest rate swaps and caps $ 6,187 $ — $ 6,187 Commodity swaps and options 239,660 — 239,660 Foreign currency forward contracts 117 — 117 Total derivatives 245,964 — 245,964 Repurchase agreements 1,842,618 — 1,842,618 Total $ 2,088,582 $ — $ 2,088,582 Gross Amounts Not Offset Net Amount Financial Collateral Net March 31, 2022 Financial assets: Derivatives: Counterparty A $ 32 $ (32) $ — $ — Counterparty B 11,998 (11,998) — — Other counterparties 22,958 (16,251) (6,707) — Total derivatives 34,988 (28,281) (6,707) — Resell agreements — — — — Total $ 34,988 $ (28,281) $ (6,707) $ — Financial liabilities: Derivatives: Counterparty A $ 2,635 $ (32) $ (2,603) $ — Counterparty B 46,953 (11,998) (34,955) — Counterparty C 3 — (3) — Other counterparties 196,373 (16,251) (180,122) — Total derivatives 245,964 (28,281) (217,683) — Repurchase agreements 1,842,618 — (1,842,618) — Total $ 2,088,582 $ (28,281) $ (2,060,301) $ — 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 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 and caps $ 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 Repurchase Agreements. We utilize securities sold under agreements to repurchase to facilitate the needs of our customers and to facilitate secured short-term funding needs. Securities sold under agreements to repurchase are stated at the amount of cash received in connection with the transaction. We monitor collateral levels on a continuous basis. We may be required to provide additional collateral based on the fair value of the underlying securities. Securities pledged as collateral under repurchase agreements are maintained with our safekeeping agents. The remaining contractual maturity of repurchase agreements in the consolidated balance sheets as of March 31, 2022 and December 31, 2021 is presented in the following tables. Remaining Contractual Maturity of the Agreements Overnight and Continuous Up to 30 Days 30-90 Days Greater than 90 Days Total March 31, 2022 Repurchase agreements: U.S. Treasury $ 876,879 $ — $ — $ — $ 876,879 Residential mortgage-backed securities 965,739 — — — 965,739 Total borrowings $ 1,842,618 $ — $ — $ — $ 1,842,618 Gross amount of recognized liabilities for repurchase agreements $ 1,842,618 Amounts related to agreements not included in offsetting disclosures above $ — 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 $ —

Stock-Based Compensation

Stock-Based Compensation	3 Months Ended
	Mar. 31, 2022
Share-based Payment Arrangement [Abstract]
Stock-Based Compensation	Stock-Based Compensation A combined summary of activity in our active stock plans is presented in the table below. Performance stock units outstanding are presented assuming attainment of the maximum payout rate as set forth by the performance criteria. As of March 31, 2022, there were 794,493 shares remaining available for grant for future stock-based compensation awards. Deferred Non-Vested Performance Stock Options Number Weighted- Number Weighted- Number Weighted- Number Weighted- Balance, January 1, 2022 56,301 $ 79.21 449,337 $ 93.05 202,460 $ 84.71 877,681 $ 69.02 Authorized — — — — — — — — Granted — — 1,038 145.32 — — — — Exercised/vested — — — — (25,180) 87.18 (90,250) 63.59 Forfeited/expired — — (1,786) 89.50 (16,058) 87.18 — — Balance, March 31, 2022 56,301 79.21 448,589 93.19 161,222 84.08 787,431 69.64 Shares issued in connection with stock compensation awards are issued from available treasury shares. If no treasury shares are available, new shares are issued from available authorized shares. Shares issued in connection with stock compensation awards along with other related information were as follows: Three Months Ended 2022 2021 New shares issued from available authorized shares — — Shares issued from available treasury stock 115,430 513,824 Proceeds from stock option exercises $ 5,739 $ 29,397 Stock-based compensation expense is recognized ratably over the requisite service period for all awards. For most stock option awards, the service period generally matches the vesting period. For stock options granted to certain executive officers and for non-vested stock units granted to all participants, the service period does not extend past the date the participant reaches 65 years of age. Deferred stock units granted to non-employee directors generally have immediate vesting and the related expense is fully recognized on the date of grant. For performance stock units, the service period generally matches the three-year performance period specified by the award, however, the service period does not extend past the date the participant reaches 65 years of age. Expense recognized each period is dependent upon our estimate of the number of shares that will ultimately be issued. Stock-based compensation expense or benefit and the related income tax benefit is presented in the following table. The service period for performance stock units granted each year begins on January 1 of the following year. Three Months Ended 2022 2021 Non-vested stock units $ 2,358 $ 1,883 Performance stock units (246) 643 Total $ 2,112 $ 2,526 Income tax benefit $ 708 $ 367 Unrecognized stock-based compensation expense at March 31, 2022 is presented in the table below. Unrecognized stock-based compensation expense related to performance stock units is presented assuming attainment of the maximum payout rate as set forth by the performance criteria. Non-vested stock units $ 16,063 Performance stock units 8,664 Total $ 24,727

Earnings Per Common Share

Earnings Per Common Share	3 Months Ended
	Mar. 31, 2022
Earnings Per Share [Abstract]
Earnings Per Common Share	Earnings Per Common Share Earnings per common share is computed using the two-class method as more fully described in our 2021 Form 10-K. The following table presents a reconciliation of net income available to common shareholders, net earnings allocated to common stock and the number of shares used in the calculation of basic and diluted earnings per common share. Three Months Ended 2022 2021 Net income $ 99,102 $ 116,015 Less: Preferred stock dividends 1,669 2,151 Net income available to common shareholders 97,433 113,864 Less: Earnings allocated to participating securities 849 1,162 Net earnings allocated to common stock $ 96,584 $ 112,702 Distributed earnings allocated to common stock $ 48,051 $ 45,660 Undistributed earnings allocated to common stock 48,533 67,042 Net earnings allocated to common stock $ 96,584 $ 112,702 Weighted-average shares outstanding for basic earnings per common share 64,051,202 63,306,493 Dilutive effect of stock compensation 409,705 509,290 Weighted-average shares outstanding for diluted earnings per common share 64,460,907 63,815,783

Defined Benefit Plans

Defined Benefit Plans	3 Months Ended
	Mar. 31, 2022
Retirement Benefits [Abstract]
Defined Benefit Plans	Defined Benefit Plans The components of the combined net periodic expense (benefit) for our defined benefit pension plans are presented in the table below. Three Months Ended 2022 2021 Expected return on plan assets, net of expenses $ (3,491) $ (3,210) Interest cost on projected benefit obligation 1,004 835 Net amortization and deferral 741 1,529 Net periodic expense (benefit) $ (1,746) $ (846) Our non-qualified defined benefit pension plan is not funded. No contributions to the qualified defined benefit pension plan were made during the three months ended March 31, 2022. We do not expect to make any contributions to the qualified defined benefit plan during the remainder of 2022.

Income Taxes

Income Taxes	3 Months Ended
	Mar. 31, 2022
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes Income tax expense was as follows: Three Months Ended 2022 2021 Current income tax expense (benefit) $ 13,059 $ 3,725 Deferred income tax expense (benefit) (432) 4,172 Income tax expense, as reported $ 12,627 $ 7,897 Effective tax rate 11.3 % 6.4 % We had a net deferred tax asset totaling $110.3 million at March 31, 2022 and a net deferred tax liability totaling $81.2 million at December 31, 2021. No valuation allowance for deferred tax assets was recorded at March 31, 2022 as management believes it is more likely than not that all of the deferred tax assets will be realized against deferred tax liabilities and projected future taxable income. The effective income tax rates differed from the U.S. statutory federal income tax rates of 21% during the comparable periods primarily due to the effect of tax-exempt income from loans, securities and life insurance policies and the income tax effects associated with stock-based compensation. There were no unrecognized tax benefits during any of the reported periods. Interest and/or penalties related to income taxes are reported as a component of income tax expense. Such amounts were not significant during the reported periods. We file income tax returns in the U.S. federal jurisdiction. We are no longer subject to U.S. federal income tax examinations by tax authorities for years before 2018.

Other Comprehensive Income (Los

Other Comprehensive Income (Loss)	3 Months Ended
	Mar. 31, 2022
Equity [Abstract]
Comprehensive Income (Loss) Note	Other Comprehensive Income (Loss) The before and after tax amounts allocated to each component of other comprehensive income (loss) are presented in the following table. Reclassification adjustments related to securities available for sale are included in net gain (loss) on securities transactions in the accompanying consolidated statements of income. Reclassification adjustments related to defined-benefit post-retirement benefit plans are included in the computation of net periodic pension expense (see Note 12 – Defined Benefit Plans). Three Months Ended Three Months Ended Before Tax Tax Expense, Net of Tax Before Tax Tax Expense, Net of Tax Securities available for sale and transferred securities: Change in net unrealized gain/loss during the period $ (910,795) $ (191,267) $ (719,528) $ (159,779) $ (33,554) $ (126,225) Change in net unrealized gain on securities transferred to held to maturity (209) (44) (165) (259) (54) (205) Reclassification adjustment for net (gains) losses included in net income — — — — — — Total securities available for sale and transferred securities (911,004) (191,311) (719,693) (160,038) (33,608) (126,430) Defined-benefit post-retirement benefit plans: Reclassification adjustment for net amortization of actuarial gain/loss included in net income as a component of net periodic expense (benefit) 741 156 585 1,529 321 1,208 Total defined-benefit post-retirement benefit plans 741 156 585 1,529 321 1,208 Total other comprehensive income (loss) $ (910,263) $ (191,155) $ (719,108) $ (158,509) $ (33,287) $ (125,222) Activity in accumulated other comprehensive income (loss), net of tax, was as follows: Securities Defined Accumulated Balance January 1, 2022 $ 380,209 $ (32,891) $ 347,318 Other comprehensive income (loss) before reclassifications (719,693) — (719,693) Reclassification of amounts included in net income — 585 585 Net other comprehensive income (loss) during period (719,693) 585 (719,108) Balance at March 31, 2022 $ (339,484) $ (32,306) $ (371,790) Balance January 1, 2021 $ 563,801 $ (50,831) $ 512,970 Other comprehensive income (loss) before reclassifications (126,430) — (126,430) Reclassification of amounts included in net income — 1,208 1,208 Net other comprehensive income (loss) during period (126,430) 1,208 (125,222) Balance at March 31, 2021 $ 437,371 $ (49,623) $ 387,748

Operating Segments

Operating Segments	3 Months Ended
	Mar. 31, 2022
Segment Reporting [Abstract]
Operating Segments	Operating Segments We are managed under a matrix organizational structure whereby our two primary operating segments, Banking and Frost Wealth Advisors, overlap a regional reporting structure. See our 2021 Form 10-K for additional information regarding our operating segments. Summarized operating results by segment were as follows: Banking Frost Wealth Non-Banks Consolidated Three months ended: March 31, 2022 Net interest income (expense) $ 250,119 $ 700 $ (1,748) $ 249,071 Credit loss expense (benefit) (1) 1 — — Non-interest income 58,706 43,229 (545) 101,390 Non-interest expense 206,538 30,910 1,284 238,732 Income (loss) before income taxes 102,288 13,018 (3,577) 111,729 Income tax expense (benefit) 11,014 2,734 (1,121) 12,627 Net income (loss) 91,274 10,284 (2,456) 99,102 Preferred stock dividends — — 1,669 1,669 Net income (loss) available to common shareholders $ 91,274 $ 10,284 $ (4,125) $ 97,433 Revenues from (expenses to) external customers $ 308,825 $ 43,929 $ (2,293) $ 350,461 March 31, 2021 Net interest income (expense) $ 242,205 $ 486 $ (1,810) $ 240,881 Credit loss expense 63 — — 63 Non-interest income 53,780 39,609 (153) 93,236 Non-interest expense 179,151 29,937 1,054 210,142 Income (loss) before income taxes 116,771 10,158 (3,017) 123,912 Income tax expense (benefit) 7,177 2,133 (1,413) 7,897 Net income (loss) 109,594 8,025 (1,604) 116,015 Preferred stock dividends — — 2,151 2,151 Net income (loss) available to common shareholders $ 109,594 $ 8,025 $ (3,755) $ 113,864 Revenues from (expenses to) external customers $ 295,985 $ 40,095 $ (1,963) $ 334,117

Fair Value Measurements

Fair Value Measurements	3 Months Ended
	Mar. 31, 2022
Fair Value Disclosures [Abstract]
Fair Value Measurements	Fair Value Measurements The fair value of an asset or liability is the price that would be received to sell that asset or paid to transfer that liability in an orderly transaction occurring in the principal market (or most advantageous market in the absence of a principal market) for such asset or liability. In estimating fair value, we utilize valuation techniques that are consistent with the market approach, the income approach and/or the cost approach. Such valuation techniques are consistently applied. Inputs to valuation techniques include the assumptions that market participants would use in pricing an asset or liability. ASC Topic 820 establishes a three-level fair value hierarchy for valuation inputs that gives the highest priority to quoted prices in active markets for identical assets or liabilities and the lowest priority to unobservable inputs. See our 2021 Form 10-K for additional information regarding the fair value hierarchy and a description of our valuation techniques. Financial Assets and Financial Liabilities. The tables below summarize financial assets and financial liabilities measured at fair value on a recurring basis as of March 31, 2022 and December 31, 2021, segregated by the level of the valuation inputs within the fair value hierarchy of ASC Topic 820 utilized to measure fair value. Level 1 Inputs Level 2 Inputs Level 3 Inputs Total Fair Value March 31, 2022 Securities available for sale: U.S. Treasury $ 3,507,746 $ — $ — $ 3,507,746 Residential mortgage-backed securities — 5,376,039 — 5,376,039 States and political subdivisions — 7,258,393 — 7,258,393 Other — 42,361 — 42,361 Trading account securities: U.S. Treasury 23,939 — — 23,939 States and political subdivisions — 5,579 — 5,579 Derivative assets: Interest rate swaps, caps and floors — 33,697 — 33,697 Commodity swaps and options — 252,747 — 252,747 Foreign currency forward contracts 150 — — 150 Derivative liabilities: Interest rate swaps, caps and floors — 39,734 — 39,734 Commodity swaps and options — 251,181 — 251,181 Foreign currency forward contracts 131 — — 131 December 31, 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 Certain financial assets and financial liabilities are measured at fair value on a nonrecurring basis; that is, the instruments are not measured at fair value on an ongoing basis but are subject to fair value adjustments in certain circumstances. Financial assets measured at fair value on a non-recurring basis during the reported periods include certain collateral dependent loans reported at the fair value of the underlying collateral if repayment is expected solely from the collateral. The following table presents collateral dependent loans that were remeasured and reported at fair value through a specific allocation of the allowance for credit losses on loans based upon the fair value of the underlying collateral during the reported periods. Three Months Ended Three Months Ended Level 2 Level 3 Level 2 Level 3 Carrying value before allocations $ 2,064 $ 5,711 $ 100 $ 15,013 Specific (allocations) reversals of prior allocations (126) 3,965 — 600 Fair value $ 1,938 $ 9,676 $ 100 $ 15,613 Non-Financial Assets and Non-Financial Liabilities. We do not have any non-financial assets or non-financial liabilities measured at fair value on a recurring basis. From time to time, non-financial assets measured at fair value on a non-recurring basis may include certain foreclosed assets which, upon initial recognition, were remeasured and reported at fair value through a charge-off to the allowance for loan losses and certain foreclosed assets which, subsequent to their initial recognition, were remeasured at fair value through a write-down included in other non-interest expense. There were no such fair value measurements during the reported periods. Financial Instruments Reported at Amortized Cost. The estimated fair values of financial instruments that are reported at amortized cost in our consolidated balance sheets, segregated by the level of the valuation inputs within the fair value hierarchy utilized to measure fair value, were as follows: March 31, 2022 December 31, 2021 Carrying Estimated Carrying Estimated Financial assets: Level 2 inputs: Cash and cash equivalents $ 14,457,083 $ 14,457,083 $ 16,583,000 $ 16,583,000 Securities held to maturity 1,665,465 1,639,993 1,749,179 1,809,143 Cash surrender value of life insurance policies 189,471 189,471 190,139 190,139 Accrued interest receivable 131,370 131,370 179,111 179,111 Level 3 inputs: Loans, net 16,295,702 16,053,955 16,087,731 16,079,454 Financial liabilities: Level 2 inputs: Deposits 44,430,929 44,422,700 42,695,696 41,343,426 Federal funds purchased 35,200 35,200 25,925 25,925 Repurchase agreements 1,842,618 1,842,618 2,740,799 2,740,799 Junior subordinated deferrable interest debentures 123,026 123,712 123,011 123,712 Subordinated notes 99,217 105,740 99,178 111,430 Accrued interest payable 2,147 2,147 3,026 3,026 Under ASC Topic 825, entities may choose to measure eligible financial instruments at fair value at specified election dates. The fair value measurement option (i) may be applied instrument by instrument, with certain exceptions, (ii) is generally irrevocable and (iii) is applied only to entire instruments and not to portions of instruments. Unrealized gains and losses on items for which the fair value measurement option has been elected must be reported in earnings at each subsequent reporting date. During the reported periods, we had no financial instruments measured at fair value under the fair value measurement option.

Accounting Standards Updates

Accounting Standards Updates	3 Months Ended
	Mar. 31, 2022
Accounting Changes and Error Corrections [Abstract]
Accounting Standards Updates	Accounting Standards Updates Information about certain recently issued accounting standards updates is presented below. Also refer to Note 20 - Accounting Standards Updates in our 2021 Form 10-K for additional information related to previously issued accounting standards updates. ASU 2022-01, “Derivatives and Hedging (Topic 815): Fair Value Hedging - Portfolio Layer Method.” Under prior guidance, entities can apply the last-of-layer hedging method to hedge the exposure of a closed portfolio of prepayable financial assets to fair value changes due to changes in interest rates for a portion of the portfolio that is not expected to be affected by prepayments, defaults, and other events affecting the timing and amount of cash flows. ASU 2022-01 expands the last-of-layer method, which permits only one hedge layer, to allow multiple hedged layers of a single closed portfolio. To reflect that expansion, the last-of-layer method is renamed the portfolio layer method. ASU 2022-01 also (i) expands the scope of the portfolio layer method to include non-prepayable financial assets, (ii) specifies eligible hedging instruments in a single-layer hedge, (iii) provides additional guidance on the accounting for and disclosure of hedge basis adjustments under the portfolio layer method and (iv) specifies how hedge basis adjustments should be considered when determining credit losses for the assets included in the closed portfolio. ASU 2022-01 will be effective for us on January 1, 2023 though early adoption is permitted. The adoption of ASU 2022-01 is not expected to have a significant impact on our financial statements. ASU 2022-02, “Financial Instruments - Credit Losses (Topic 326): Troubled Debt Restructurings and Vintage Disclosures.” ASU 2022-02 eliminates the accounting guidance for troubled debt restructurings in Accounting Standards Codification (“ASC”) Subtopic 310-40, Receivables - Troubled Debt Restructurings by Creditors, while enhancing disclosure requirements for certain loan refinancings and restructurings by creditors when a borrower is experiencing financial difficulty. Additionally, ASU 2022-02 requires entities to disclose current-period gross write-offs by year of origination for financing receivables and net investments in leases within the scope of ASC Subtopic 3126-20, Financial Instruments - Credit Losses - Measured at Amortized Cost. ASU 2022-02 will be effective for us on January 1, 2023 though early adoption is permitted. The adoption of ASU 2022-02 is not expected to have a significant impact on our financial statements.

Significant Accounting Polici_2

Significant Accounting Policies (Policies)	3 Months Ended
	Mar. 31, 2022
Accounting Policies [Abstract]
Nature of Operations	Nature of Operations. Cullen/Frost Bankers, Inc. (“Cullen/Frost”) is a financial holding company and a bank holding company headquartered in San Antonio, Texas that provides, through its subsidiaries, a broad array of products and services throughout numerous Texas markets. The terms “Cullen/Frost,” “the Corporation,” “we,” “us” and “our” mean Cullen/Frost Bankers, Inc. and its subsidiaries, when appropriate. In addition to general commercial and consumer banking, other products and services offered include trust and investment management, insurance, brokerage, mutual funds, leasing, treasury management, capital markets advisory and item processing.
Basis of Presentation	Basis of Presentation. The consolidated financial statements in this Quarterly Report on Form 10-Q include the accounts of Cullen/Frost and all other entities in which Cullen/Frost has a controlling financial interest. All significant intercompany balances and transactions have been eliminated in consolidation. The accounting and financial reporting policies we follow conform, in all material respects, to accounting principles generally accepted in the United States and to general practices within the financial services industry. The consolidated financial statements in this Quarterly Report on Form 10-Q have not been audited by an independent registered public accounting firm, but in the opinion of management, reflect all adjustments necessary for a fair presentation of our financial position and results of operations. All such adjustments were of a normal and recurring nature. The consolidated financial statements have been prepared in accordance with accounting principles generally accepted in the United States for interim financial information and with the instructions to Form 10-Q adopted by the Securities and Exchange Commission (“SEC”). Accordingly, the financial statements do not include all of the information and footnotes required by accounting principles generally accepted in the United States for complete financial statements and should be read in conjunction with our consolidated financial statements, and notes thereto, for the year ended December 31, 2021, included in our Annual Report on Form 10-K filed with the SEC on February 4, 2022 (the “2021 Form 10-K”). Operating results for the interim periods disclosed herein are not necessarily indicative of the results that may be expected for a full year or any future period.
Use of Estimates	Use of Estimates . The preparation of financial statements in conformity with accounting principles generally accepted in the United States requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements. Actual results could differ from those estimates. The allowance for loan losses and the fair values of financial instruments and the status of contingencies are particularly subject to change.
Reclassification, Policy [Policy Text Block]	Certain items in prior financial statements have been reclassified to conform to the current presentation.

Loans Loans - Allowance For Cre

Loans Loans - Allowance For Credit Losses (Policies)	3 Months Ended
	Mar. 31, 2022
Accounting Policies [Abstract]
Loans and Leases Receivable, Allowance for Loan Losses Policy [Policy Text Block]	Allowance For Credit Losses - Loans. The allowance for credit losses on loans is a contra-asset valuation account, calculated in accordance with ASC 326, that is deducted from the amortized cost basis of loans to present the net amount expected to be collected. The amount of the allowance represents management's best estimate of current expected credit losses on loans considering available information, from internal and external sources, relevant to assessing collectibility over the loans' contractual terms, adjusted for expected prepayments when appropriate. Credit loss expense related to loans reflects the totality of actions taken on all loans for a particular period including any necessary increases or decreases in the allowance related to changes in credit loss expectations associated with specific loans or pools of loans. Portions of the allowance may be allocated for specific credits; however, the entire allowance is available for any credit that, in management’s judgment, should be charged off. While management utilizes its best judgment and information available, the ultimate appropriateness of the allowance is dependent upon a variety of factors beyond our control, including the performance of our loan portfolio, the economy, changes in interest rates and the view of the regulatory authorities toward loan classifications. Our allowance methodology is more fully described in our 2021 Form 10-K.

Significant Accounting Polici_3

Significant Accounting Policies (Tables)	3 Months Ended
	Mar. 31, 2022
Accounting Policies [Abstract]
Additional Cash Flow Information	Additional cash flow information was as follows: Three Months Ended 2022 2021 Cash paid for interest $ 8,069 $ 9,719 Cash paid for income taxes — — Significant non-cash transactions: Unsettled securities transactions 78,769 21,957 Right-of-use lease assets obtained in exchange for lessee operating lease liabilities 4,013 1,326 Treasury stock issued to 401(k) stock purchase plan — 1,749

Securities (Tables)

Securities (Tables)	3 Months Ended
	Mar. 31, 2022
Investments, Debt and Equity Securities [Abstract]
Debt Securities, Held-to-maturity [Table Text Block]	A summary of the amortized cost, fair value and allowance for credit losses related to securities held to maturity as of March 31, 2022 and December 31, 2021 is presented below. Amortized Gross Gross Estimated Allowance Net March 31, 2022 Residential mortgage-backed securities $ 526,969 $ — $ 17,519 $ 509,450 $ — $ 526,969 States and political subdivisions 1,137,154 3,622 11,717 1,129,059 (158) 1,136,996 Other 1,500 — 16 1,484 — 1,500 Total $ 1,665,623 $ 3,622 $ 29,252 $ 1,639,993 $ (158) $ 1,665,465 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
Moody's and Standard & Poor's Bond Ratings [Table Text Block]	The following table summarizes Moody's and/or Standard & Poor's bond ratings for our portfolio of held-to-maturity securities issued by States and political subdivisions and other securities as of March 31, 2022 and December 31, 2021: States and Political Subdivisions Not Guaranteed or Pre-Refunded Guaranteed by the Texas PSF Pre-Refunded Total Other March 31, 2022 Aaa/AAA $ 91,034 $ 467,039 $ 471,183 $ 1,029,256 $ — Aa/AA 107,898 — — 107,898 — Not rated — — — — 1,500 Total $ 198,932 $ 467,039 $ 471,183 $ 1,137,154 $ 1,500 December 31, 2021 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 [Table Text Block]	The following table details activity in the allowance for credit losses on held-to-maturity securities during the three months ended March 31, 2022 and 2021. Three Months Ended 2022 2021 Beginning balance $ 158 $ 160 Credit loss expense (benefit) — (2) Ending balance $ 158 $ 158
Amortized Cost, Estimated Fair Value and Allowance for Credit Losses of Securities Available for Sale	A summary of the amortized cost, fair value and allowance for credit losses related to securities available for sale as of March 31, 2022 and December 31, 2021 is presented below. Amortized Gross Gross Allowance Estimated March 31, 2022 U.S. Treasury $ 3,658,506 $ 1,883 $ 152,643 $ — $ 3,507,746 Residential mortgage-backed securities 5,696,906 7,246 328,113 — 5,376,039 States and political subdivisions 7,218,821 135,206 95,634 — 7,258,393 Other 42,361 — — — 42,361 Total $ 16,616,594 $ 144,335 $ 576,390 $ — $ 16,184,539 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
Securities, with Unrealized Losses Segregated by Length of Impairment	The table below summarizes, as of March 31, 2022, securities available for sale in an unrealized loss position for which an allowance for credit losses has not been recorded, aggregated by type of security and length of time in a continuous unrealized loss position. Less than 12 Months More than 12 Months Total Estimated Unrealized Estimated Unrealized Estimated Unrealized U.S. Treasury $ 3,220,375 $ 152,643 $ — $ — $ 3,220,375 $ 152,643 Residential mortgage-backed securities 4,583,657 286,421 402,940 41,692 4,986,597 328,113 States and political subdivisions 1,233,614 93,136 13,602 2,498 1,247,216 95,634 Total $ 9,037,646 $ 532,200 $ 416,542 $ 44,190 $ 9,454,188 $ 576,390
Amortized Cost and Estimated Fair Value of Securities, Excluding Trading Securities, Presented by Contractual Maturity	The following table summarizes the maturity distribution schedule of securities held to maturity and securities available for sale as of March 31, 2022. 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 $ 16 $ — $ 514,842 $ 12,111 $ 526,969 States and political subdivisions 429,852 118,516 56,735 532,051 1,137,154 Other — 1,500 — — 1,500 Total $ 429,868 $ 120,016 $ 571,577 $ 544,162 $ 1,665,623 Estimated Fair Value Residential mortgage-backed securities $ 16 $ — $ 498,078 $ 11,356 $ 509,450 States and political subdivisions 431,961 119,698 56,973 520,427 1,129,059 Other — 1,484 — — 1,484 Total $ 431,977 $ 121,182 $ 555,051 $ 531,783 $ 1,639,993 Available For Sale Amortized Cost U. S. Treasury $ — $ 2,033,995 $ 1,432,731 $ 191,780 $ 3,658,506 Residential mortgage-backed securities 102 12,917 19,060 5,664,827 5,696,906 States and political subdivisions 194,416 1,563,829 888,489 4,572,087 7,218,821 Other — — — — 42,361 Total $ 194,518 $ 3,610,741 $ 2,340,280 $ 10,428,694 $ 16,616,594 Estimated Fair Value U. S. Treasury $ — $ 1,978,865 $ 1,350,553 $ 178,328 $ 3,507,746 Residential mortgage-backed securities 103 13,212 19,327 5,343,397 5,376,039 States and political subdivisions 197,231 1,603,985 899,602 4,557,575 7,258,393 Other — — — — 42,361 Total $ 197,334 $ 3,596,062 $ 2,269,482 $ 10,079,300 $ 16,184,539
Investment Income	Premium amortization and discount accretion included in interest income on securities was as follows: Three Months Ended 2022 2021 Premium amortization $ (29,060) $ (31,235) Discount accretion 1,406 637 Net (premium amortization) discount accretion $ (27,654) $ (30,598)
Trading Account Securities, at Estimated Fair Value	Trading account securities, at estimated fair value, were as follows: March 31, December 31, U.S. Treasury $ 23,939 $ 24,237 States and political subdivisions 5,579 925 Total $ 29,518 $ 25,162
Net Gains and Losses on Trading Account Securities	Net gains and losses on trading account securities were as follows: Three Months Ended 2022 2021 Net gain on sales transactions $ 340 $ 109 Net mark-to-market gains (losses) (168) (69) Net gain (loss) on trading account securities $ 172 $ 40

Loans (Tables)

Loans (Tables)	3 Months Ended
	Mar. 31, 2022
Receivables [Abstract]
Loans	Loans were as follows: March 31, December 31, Commercial and industrial $ 5,584,117 $ 5,364,954 Energy: Production 820,107 878,436 Service 113,708 105,901 Other 102,764 93,455 Total energy 1,036,579 1,077,792 Paycheck Protection Program 207,669 428,882 Commercial real estate: Commercial mortgages 5,918,011 5,867,062 Construction 1,421,878 1,304,271 Land 458,510 405,277 Total commercial real estate 7,798,399 7,576,610 Consumer real estate: Home equity loans 321,842 324,157 Home equity lines of credit 544,822 519,098 Other 566,961 567,535 Total consumer real estate 1,433,625 1,410,790 Total real estate 9,232,024 8,987,400 Consumer and other 482,148 477,369 Total loans $ 16,542,537 $ 16,336,397
Non-Accrual Loans, Segregated by Class of Loans	Non-accrual loans, segregated by class of loans, were as follows: March 31, 2022 December 31, 2021 Total Non-Accrual Non-Accrual with No Credit Loss Allowance Total Non-Accrual Non-Accrual with No Credit Loss Allowance Commercial and industrial $ 16,693 $ 6,135 $ 22,582 $ 4,701 Energy 12,271 6,912 14,433 8,533 Paycheck Protection Program — — — — Commercial real estate: Buildings, land and other 19,003 17,005 15,297 13,817 Construction 583 583 948 — Consumer real estate 416 114 440 138 Consumer and other — — 13 13 Total $ 48,966 $ 30,749 $ 53,713 $ 27,202
Financing Receivable, Non-Accrual Loans, Segregated by Class of Loan and Year of Origination	The following table presents non-accrual loans as of March 31, 2022 by class and year of origination. 2021 2020 2019 2018 2017 Prior Revolving Loans Revolving Loans Converted to Term Total Commercial and industrial $ — $ 478 $ 4,101 $ 3,910 $ 1,552 $ 1,033 $ 2,038 $ 3,581 $ 16,693 Energy — — — 5,039 1,137 — 5,997 98 12,271 Paycheck Protection Program — — — — — — — — — Commercial real estate: Buildings, land and other — 8,407 296 1,199 394 2,932 — 5,775 19,003 Construction — — 583 — — — — — 583 Consumer real estate — — — — — 390 — 26 416 Consumer and other — — — — — — — — — Total $ — $ 8,885 $ 4,980 $ 10,148 $ 3,083 $ 4,355 $ 8,035 $ 9,480 $ 48,966
Age Analysis of Past Due Loans, Segregated by Class of Loans	An age analysis of past due loans (including both accruing and non-accruing loans), segregated by class of loans, as of March 31, 2022 was as follows: Loans Loans Total Current Total Accruing Commercial and industrial $ 13,016 $ 8,042 $ 21,058 $ 5,563,059 $ 5,584,117 $ 4,166 Energy — 6,382 6,382 1,030,197 1,036,579 287 Paycheck Protection Program 671 8,377 9,048 198,621 207,669 8,377 Commercial real estate: Buildings, land and other 21,542 11,546 33,088 6,343,433 6,376,521 1,046 Construction 1,988 — 1,988 1,419,890 1,421,878 — Consumer real estate 4,210 2,409 6,619 1,427,006 1,433,625 2,103 Consumer and other 6,393 593 6,986 475,162 482,148 593 Total $ 47,820 $ 37,349 $ 85,169 $ 16,457,368 $ 16,542,537 $ 16,572
Restructured Loans Past Due in Excess of 90 Days on Financing Receivables	Information as of or for the three months ended March 31, 2022 and 2021 related to loans restructured during the last twelve months is set forth in the following table. March 31, 2022 March 31, 2021 Restructured loans past due in excess of 90 days at period-end: Number of loans 2 2 Dollar amount of loans $ 572 $ 1,392 Charge-offs of restructured loans: Recognized on previously restructured loans 723 1,433
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 March 31, 2022. Paycheck Protection Program (“PPP”) loans are excluded as such loans are fully guaranteed by the Small Business Administration (“SBA”). 2022 2021 2020 2019 2018 Prior Revolving Loans Revolving Loans Converted to Term Total W/A Risk Grade Commercial and industrial Risk grades 1-8 $ 836,152 $ 894,663 $ 592,780 $ 305,667 $ 160,622 $ 243,869 $ 2,255,878 $ 44,778 $ 5,334,409 6.18 Risk grade 9 4,702 34,513 6,562 11,434 21,841 8,319 54,008 4,721 146,100 9.00 Risk grade 10 3,500 22,084 6,527 1,039 4,007 578 13,899 1,198 52,832 10.00 Risk grade 11 — 1,926 6,672 9,679 1,697 2,200 5,958 5,951 34,083 11.00 Risk grade 12 — 478 2,644 3,510 1,488 619 941 2,015 11,695 12.00 Risk grade 13 — — 1,457 400 64 414 1,097 1,566 4,998 13.00 $ 844,354 $ 953,664 $ 616,642 $ 331,729 $ 189,719 $ 255,999 $ 2,331,781 $ 60,229 $ 5,584,117 6.34 W/A risk grade 6.16 6.87 6.17 6.75 7.00 5.80 6.14 7.82 6.34 Energy Risk grades 1-8 $ 279,051 $ 125,435 $ 7,519 $ 8,444 $ 4,068 $ 5,665 $ 509,657 $ 59,424 $ 999,263 5.71 Risk grade 9 1,425 103 508 1,407 96 — 5,668 43 9,250 9.00 Risk grade 10 — — 90 580 351 — — 515 1,536 10.00 Risk grade 11 9,097 265 512 3,256 951 178 — — 14,259 11.00 Risk grade 12 — — — 3,708 58 — 3,215 98 7,079 12.00 Risk grade 13 — — — 1,331 1,079 — 2,782 — 5,192 13.00 $ 289,573 $ 125,803 $ 8,629 $ 18,726 $ 6,603 $ 5,843 $ 521,322 $ 60,080 $ 1,036,579 5.89 W/A risk grade 6.36 5.77 7.73 9.34 9.24 7.16 5.41 6.31 5.89 2022 2021 2020 2019 2018 Prior Revolving Loans Revolving Loans Converted to Term Total W/A Risk Grade Commercial real estate: Buildings, land, other Risk grades 1-8 $ 607,883 $ 1,554,611 $ 1,113,230 $ 809,206 $ 498,477 $ 1,057,840 $ 72,704 $ 96,924 $ 5,810,875 6.89 Risk grade 9 6,163 20,766 108,943 53,448 23,459 45,034 5,516 2,618 265,947 9.00 Risk grade 10 46,125 22,716 7,310 66,821 24,539 57,602 — — 225,113 10.00 Risk grade 11 — 260 1,293 7,328 6,788 36,699 3,215 — 55,583 11.00 Risk grade 12 — 8,081 296 1,199 394 2,932 — 5,775 18,677 12.00 Risk grade 13 — 326 — — — — — — 326 13.00 $ 660,171 $ 1,606,760 $ 1,231,072 $ 938,002 $ 553,657 $ 1,200,107 $ 81,435 $ 105,317 $ 6,376,521 7.14 W/A risk grade 7.08 7.22 7.04 7.32 7.27 6.97 7.06 6.99 7.14 Construction Risk grades 1-8 $ 202,413 $ 634,897 $ 195,127 $ 141,510 $ 636 $ 1,842 $ 207,182 $ 3,666 $ 1,387,273 6.96 Risk grade 9 171 28,069 5,359 — — 423 — — 34,022 9.00 Risk grade 10 — — — — — — — — — 10.00 Risk grade 11 — — — — — — — — — 11.00 Risk grade 12 — — 583 — — — — — 583 12.00 Risk grade 13 — — — — — — — — — 13.00 $ 202,584 $ 662,966 $ 201,069 $ 141,510 $ 636 $ 2,265 $ 207,182 $ 3,666 $ 1,421,878 7.01 W/A risk grade 6.83 7.28 6.38 7.98 6.22 7.17 6.28 8.00 7.01 Total commercial real estate $ 862,755 $ 2,269,726 $ 1,432,141 $ 1,079,512 $ 554,293 $ 1,202,372 $ 288,617 $ 108,983 $ 7,798,399 7.11 W/A risk grade 7.02 7.24 6.95 7.41 7.27 6.97 6.50 7.03 7.11
Weighted Average Risk Grades for All Commercial Loans by Class	The following tables present weighted average risk grades for all commercial loans by class as of December 31, 2021. Refer to our 2021 Form 10-K for details of these loans by year of origination/renewal. Commercial and Industrial Energy Commercial Real Estate - Buildings, Land and Other Commercial Real Estate - Construction Total Commercial Real Estate W/A Risk Grade Loans W/A Risk Grade Loans W/A Risk Grade Loans W/A Risk Grade Loans W/A Risk Grade Loans Risk grades 1-8 6.01 $ 5,063,847 5.78 $ 1,008,370 6.91 $ 5,574,922 6.99 $ 1,262,200 6.92 $ 6,837,122 Risk grade 9 9.00 187,870 9.00 36,622 9.00 321,533 9.00 41,123 9.00 362,656 Risk grade 10 10.00 59,137 10.00 1,773 10.00 269,447 10.00 — 10.00 269,447 Risk grade 11 11.00 31,518 11.00 16,594 11.00 91,140 11.00 — 11.00 91,140 Risk grade 12 12.00 12,535 12.00 8,953 12.00 15,097 12.00 748 12.00 15,845 Risk grade 13 13.00 10,047 13.00 5,480 13.00 200 13.00 200 13.00 400 Total 6.22 $ 5,364,954 6.06 $ 1,077,792 7.22 $ 6,272,339 7.06 $ 1,304,271 7.19 $ 7,576,610
Age analysis of Past Due Consumer Loans by Class and Year of Origination	Information about the payment status of consumer loans, segregated by portfolio segment and year of origination, as of March 31, 2022 was as follows: 2022 2021 2020 2019 2018 Prior Revolving Loans Revolving Loans Converted to Term Total Consumer real estate: Past due 30-89 days $ — $ 303 $ 55 $ 465 $ 309 $ 1,587 $ 60 $ 1,431 $ 4,210 Past due 90 or more days — — 4 — 297 854 1,004 250 2,409 Total past due — 303 59 465 606 2,441 1,064 1,681 6,619 Current loans 51,321 322,814 225,921 86,664 48,481 149,677 533,182 8,946 1,427,006 Total $ 51,321 $ 323,117 $ 225,980 $ 87,129 $ 49,087 $ 152,118 $ 534,246 $ 10,627 $ 1,433,625 Consumer and other: Past due 30-89 days $ 1,470 $ 385 $ 53 $ 69 $ 54 $ 24 $ 2,344 $ 1,994 $ 6,393 Past due 90 or more days — 499 — 23 — 13 — 58 593 Total past due 1,470 884 53 92 54 37 2,344 2,052 6,986 Current loans 21,692 34,798 13,127 4,936 2,207 2,520 371,266 24,616 475,162 Total $ 23,162 $ 35,682 $ 13,180 $ 5,028 $ 2,261 $ 2,557 $ 373,610 $ 26,668 $ 482,148
Revolving Loans Converted to Term [Table Text Block]	Revolving loans that converted to term during the three months ended March 31, 2022 and 2021 were as follows: Three Months Ended March 31, 2021 2020 Commercial and industrial $ 5,763 $ 11,843 Energy — 5,928 Commercial real estate: Buildings, land and other 47 23,303 Construction 3,666 — Consumer real estate 858 793 Consumer and other 4,222 3,861 Total $ 14,556 $ 45,728
Financing Receivable, Allowance for Credit Loss By Loan Class Calculated in Accordance With CECL Methodology	The following table presents details of the allowance for credit losses on loans segregated by loan portfolio segment as of March 31, 2022 and December 31, 2021. No allowance for credit losses has been recognized for PPP loans as such loans are fully guaranteed by the SBA. March 31, 2022 Commercial Energy Commercial Consumer Consumer Total Modeled expected credit losses $ 46,635 $ 5,971 $ 17,110 $ 6,260 $ 7,634 $ 83,610 Q-Factor and other qualitative adjustments 33,916 4,260 111,518 63 1,440 151,197 Specific allocations 6,475 5,191 326 36 — 12,028 Total $ 87,026 $ 15,422 $ 128,954 $ 6,359 $ 9,074 $ 246,835 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
Activity in Allowance for Loan Losses by Portfolio Segment	The following table details activity in the allowance for credit losses on loans by portfolio segment for the three months ended March 31, 2022 and 2021. Allocation of a portion of the allowance to one category of loans does not preclude its availability to absorb losses in other categories. No allowance for credit losses has been recognized for PPP loans as such loans are fully guaranteed by the SBA. Commercial Energy Commercial Consumer Consumer Total Three months ended: March 31, 2022 Beginning balance $ 72,091 $ 17,217 $ 144,936 $ 6,585 $ 7,837 $ 248,666 Credit loss expense (benefit) 17,561 (2,044) (15,609) (26) 4,582 4,464 Charge-offs (3,455) (371) (702) (231) (5,771) (10,530) Recoveries 829 620 329 31 2,426 4,235 Net charge-offs (2,626) 249 (373) (200) (3,345) (6,295) Ending balance $ 87,026 $ 15,422 $ 128,954 $ 6,359 $ 9,074 $ 246,835 March 31, 2021 Beginning balance $ 73,843 $ 39,553 $ 134,892 $ 7,926 $ 6,963 $ 263,177 Credit loss expense (benefit) (1,965) (5,801) 8,922 (2,722) 1,566 — Charge-offs (2,189) (1,433) — (284) (4,060) (7,966) Recoveries 1,203 1,153 626 716 2,349 6,047 Net charge-offs (986) (280) 626 432 (1,711) (1,919) Ending balance $ 70,892 $ 33,472 $ 144,440 $ 5,636 $ 6,818 $ 261,258
Investment in Loans Related to Allowance for Loan Losses by Portfolio Segment Disaggregated Based on Impairment Methodology	The following table presents loans that were evaluated for expected credit losses on an individual basis and the related specific allocations, by loan portfolio segment as of March 31, 2022 and December 31, 2021. March 31, 2022 December 31, 2021 Loan Specific Allocations Loan Specific Allocations Commercial and industrial $ 21,529 $ 6,475 $ 24,523 $ 10,536 Energy 11,931 5,191 16,393 5,480 Paycheck Protection Program — — — — Commercial real estate: Buildings, land and other 28,806 326 24,670 200 Construction — — 948 200 Consumer real estate 302 36 303 36 Consumer and other — — — — Total $ 62,568 $ 12,028 $ 66,837 $ 16,452

Goodwill and Other Intangible_2

Goodwill and Other Intangible Assets (Tables)	3 Months Ended
	Mar. 31, 2022
Goodwill and Intangible Assets Disclosure [Abstract]
Schedule of Intangible Assets and Goodwill	Goodwill and other intangible assets are presented in the table below. March 31, December 31, Goodwill $ 654,952 $ 654,952 Other intangible assets: Core deposits $ 591 $ 718 Customer relationships 129 148 $ 720 $ 866
Estimated Aggregate Future Amortization Expense for Intangible Assets	The estimated aggregate future amortization expense for intangible assets remaining as of March 31, 2022 is as follows: Remainder of 2022 $ 335 2023 282 2024 87 2025 11 2026 5 Thereafter — $ 720

Deposits (Tables)

Deposits (Tables)	3 Months Ended
	Mar. 31, 2022
Disclosure Text Block [Abstract]
Deposit Liabilities, Type	Deposits were as follows: March 31, December 31, Non-interest-bearing demand deposits $ 18,114,430 $ 18,423,018 Interest-bearing deposits: Savings and interest checking 12,484,308 11,930,959 Money market accounts 12,490,612 11,228,815 Time accounts 1,341,579 1,112,904 Total interest-bearing deposits 26,316,499 24,272,678 Total deposits $ 44,430,929 $ 42,695,696
Additional Information About Corporation's Deposits	The following table presents additional information about our deposits: March 31, December 31, Deposits from foreign sources (primarily Mexico) $ 1,092,302 $ 993,479 Non-interest-bearing public funds deposits 746,097 1,235,026 Interest-bearing public funds deposits 975,511 810,863 Total deposits not covered by deposit insurance 25,213,248 24,125,359 Time deposits not covered by deposit insurance 357,529 238,608

Commitments and Contingencies (

Commitments and Contingencies (Tables)	3 Months Ended
	Mar. 31, 2022
Commitments and Contingencies Disclosure [Abstract]
Financial Instruments with Off-Balance-Sheet Risk	Financial instruments with off-balance-sheet risk were as follows: March 31, December 31, Commitments to extend credit $ 10,356,196 $ 10,420,142 Standby letters of credit 236,798 238,690 Deferred standby letter of credit fees 1,704 2,072
Commitments, Off-Balance-Sheet, Allowance for Credit Losses [Table Text Block]	The following table details activity in the allowance for credit losses on off-balance-sheet credit exposures. Three Months Ended 2022 2021 Beginning balance $ 50,314 $ 44,152 Credit loss expense (benefit) (4,464) 65 Ending balance $ 45,850 $ 44,217
Lease Commitments, Components of Lease Expense [Table Text Block]	We lease certain office facilities and office equipment under operating leases. The components of total lease expense were as follows: Three Months Ended 2022 2021 Amortization of lease right-of-use assets $ 8,105 $ 8,283 Short-term lease expense 613 204 Non-lease components (including taxes, insurance, common maintenance, etc.) 3,020 3,004 Total $ 11,738 $ 11,491

Capital and Regulatory Matters

Capital and Regulatory Matters (Tables)	3 Months Ended
	Mar. 31, 2022
Banking Regulation, Common Equity Tier One Risk-Based Capital [Abstract]
Actual and Required Capital Ratios	The following table presents actual and required capital ratios as of March 31, 2022 and December 31, 2021 for Cullen/Frost and Frost Bank under the Basel III Capital Rules. Capital levels required to be considered well capitalized are based upon prompt corrective action regulations, as amended to reflect the changes under the Basel III Capital Rules. See the 2021 Form 10-K for a more detailed discussion of the Basel III Capital Rules. Actual Minimum Capital Required - Basel III Required to be Capital Ratio Capital Ratio Capital Ratio March 31, 2022 Common Equity Tier 1 to Risk-Weighted Assets Cullen/Frost $ 3,412,080 12.78 % $ 1,869,007 7.00 % $ 1,735,506 6.50 % Frost Bank 3,301,515 12.39 1,865,304 7.00 1,732,068 6.50 Tier 1 Capital to Risk-Weighted Assets Cullen/Frost 3,557,532 13.32 2,269,508 8.50 2,136,007 8.00 Frost Bank 3,301,515 12.39 2,265,012 8.50 2,131,776 8.00 Total Capital to Risk-Weighted Assets Cullen/Frost 3,998,333 14.97 2,803,510 10.50 2,670,009 10.00 Frost Bank 3,542,316 13.29 2,797,956 10.50 2,664,720 10.00 Leverage Ratio Cullen/Frost 3,557,532 7.08 2,010,897 4.00 2,513,621 5.00 Frost Bank 3,301,515 6.57 2,009,767 4.00 2,512,209 5.00 December 31, 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

Derivative Financial Instrume_2

Derivative Financial Instruments (Tables)	3 Months Ended
	Mar. 31, 2022
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Schedule of Notional Amounts and Estimated Fair Values of Interest Rate Derivative Contracts Outstanding	The notional amounts and estimated fair values of interest rate derivative contracts are presented in the following table. The fair values of interest rate derivative contracts are estimated utilizing internal valuation methods with observable market data inputs, or as determined by the Chicago Mercantile Exchange (“CME”) for centrally cleared derivative contracts. CME rules legally characterize variation margin payments for centrally cleared derivatives as settlements of the derivatives' exposure rather than collateral. As a result, the variation margin payment and the related derivative instruments are considered a single unit of account for accounting and financial reporting purposes. Variation margin, as determined by the CME, is settled daily. As a result, derivative contracts that clear through the CME have an estimated fair value of zero as of March 31, 2022 and December 31, 2021. March 31, 2022 December 31, 2021 Notional Estimated Notional Estimated Derivatives designated as hedges of fair value: Financial institution counterparties: Loan/lease interest rate swaps – assets $ 1,807 $ 1 $ — $ — Loan/lease interest rate swaps – liabilities 280 (3) 2,426 (34) Non-hedging interest rate derivatives: Financial institution counterparties: Loan/lease interest rate swaps – assets 697,834 15,311 247,592 1,207 Loan/lease interest rate swaps – liabilities 447,742 (6,184) 928,756 (19,142) Loan/lease interest rate caps – assets 265,930 8,110 270,431 3,239 Customer counterparties: Loan/lease interest rate swaps – assets 447,742 10,275 928,756 39,864 Loan/lease interest rate swaps – liabilities 697,834 (25,437) 247,592 (2,846) Loan/lease interest rate caps – liabilities 265,930 (8,110) 270,431 (3,239)
Schedule of Weighted-Average Rates Paid and Received for Interest Rate Swaps Outstanding	The weighted-average rates paid and received for interest rate swaps outstanding at March 31, 2022 were as follows: Weighted-Average Interest Interest Interest rate swaps: Fair value hedge loan/lease interest rate swaps 2.11 % 0.26 % Non-hedging interest rate swaps – financial institution counterparties 3.69 2.07 Non-hedging interest rate swaps – customer counterparties 2.07 3.69
Schedule of Notional Amounts and Estimated Fair Values of Commodity Derivative Positions	The notional amounts and estimated fair values of non-hedging commodity swap and option derivative positions outstanding are presented in the following table. We obtain dealer quotations and use internal valuation methods with observable market data inputs to value our commodity derivative positions. March 31, 2022 December 31, 2021 Notional Notional Estimated Notional Estimated Financial institution counterparties: Oil – assets Barrels 2,988 $ 9,735 4,809 $ 14,721 Oil – liabilities Barrels 9,767 (189,416) 7,032 (73,594) Natural gas – assets MMBTUs 14,564 1,813 15,947 4,143 Natural gas – liabilities MMBTUs 27,474 (50,244) 29,446 (21,249) Customer counterparties: Oil – assets Barrels 9,767 190,776 7,046 74,437 Oil – liabilities Barrels 2,988 (9,710) 4,796 (14,294) Natural gas – assets MMBTUs 27,474 50,423 29,446 21,456 Natural gas – liabilities MMBTUs 14,564 (1,811) 15,947 (4,124)
Schedule of Foreign Exchange Contracts, Statement of Financial Position	The notional amounts and fair values of open foreign currency forward contracts were as follows: March 31, 2022 December 31, 2021 Notional Notional Estimated Notional Estimated Financial institution counterparties: Forward contracts – assets EUR 2,400 $ 18 1,900 $ 29 Forward contracts – assets CAD — — 658 — Forward contracts – liabilities EUR 6,500 (111) — — Forward contracts – liabilities CAD 658 (6) — — Customer counterparties: Forward contracts – assets EUR 6,500 122 — — Forward contracts – assets CAD 658 10 658 4 Forward contracts – liabilities EUR 2,400 (14) 1,900 (55)
Schedule of Amounts Related to Interest Rate Derivatives Designated as Hedges of Fair Value	Amounts included in the consolidated statements of income related to interest rate derivatives designated as hedges of fair value were as follows: Three Months Ended 2022 2021 Commercial loan/lease interest rate swaps: Amount of gain (loss) included in interest income on loans $ (13) $ (28) Amount of (gain) loss included in other non-interest expense 2 (3)
Schedule of Amounts Related to Non-Hedging Interest Rate and Commodity Derivatives	Amounts included in the consolidated statements of income related to non-hedge related derivative instruments are presented in the table below. Three Months Ended 2022 2021 Non-hedging interest rate derivatives: Other non-interest income $ 516 $ 1,587 Other non-interest expense — (1) Non-hedging commodity derivatives: Other non-interest income 929 1,154 Non-hedging foreign currency derivatives: Other non-interest income 18 30

Balance Sheet Offsetting (Table

Balance Sheet Offsetting (Tables)	3 Months Ended
	Mar. 31, 2022
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Financial Instruments Eligible for Offset Consolidated Balance Sheet	Information about financial instruments that are eligible for offset in the consolidated balance sheet as of March 31, 2022 is presented in the following tables. Gross Amount Gross Amount Net Amount March 31, 2022 Financial assets: Derivatives: Loan/lease interest rate swaps and caps $ 23,422 $ — $ 23,422 Commodity swaps and options 11,548 — 11,548 Foreign currency forward contracts 18 — 18 Total derivatives 34,988 — 34,988 Resell agreements — — — Total $ 34,988 $ — $ 34,988 Financial liabilities: Derivatives: Loan/lease interest rate swaps and caps $ 6,187 $ — $ 6,187 Commodity swaps and options 239,660 — 239,660 Foreign currency forward contracts 117 — 117 Total derivatives 245,964 — 245,964 Repurchase agreements 1,842,618 — 1,842,618 Total $ 2,088,582 $ — $ 2,088,582 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 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 and caps $ 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
Financial Instruments Derivative Assets Liabilities and Resell Agreements Net of Amount Not Offset	Gross Amounts Not Offset Net Amount Financial Collateral Net March 31, 2022 Financial assets: Derivatives: Counterparty A $ 32 $ (32) $ — $ — Counterparty B 11,998 (11,998) — — Other counterparties 22,958 (16,251) (6,707) — Total derivatives 34,988 (28,281) (6,707) — Resell agreements — — — — Total $ 34,988 $ (28,281) $ (6,707) $ — Financial liabilities: Derivatives: Counterparty A $ 2,635 $ (32) $ (2,603) $ — Counterparty B 46,953 (11,998) (34,955) — Counterparty C 3 — (3) — Other counterparties 196,373 (16,251) (180,122) — Total derivatives 245,964 (28,281) (217,683) — Repurchase agreements 1,842,618 — (1,842,618) — Total $ 2,088,582 $ (28,281) $ (2,060,301) $ — 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
Remaining Contractual Maturity of the Securities Sold Under Agreement [Table Text Block]	The remaining contractual maturity of repurchase agreements in the consolidated balance sheets as of March 31, 2022 and December 31, 2021 is presented in the following tables. Remaining Contractual Maturity of the Agreements Overnight and Continuous Up to 30 Days 30-90 Days Greater than 90 Days Total March 31, 2022 Repurchase agreements: U.S. Treasury $ 876,879 $ — $ — $ — $ 876,879 Residential mortgage-backed securities 965,739 — — — 965,739 Total borrowings $ 1,842,618 $ — $ — $ — $ 1,842,618 Gross amount of recognized liabilities for repurchase agreements $ 1,842,618 Amounts related to agreements not included in offsetting disclosures above $ — 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 $ —

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	3 Months Ended
	Mar. 31, 2022
Share-based Payment Arrangement [Abstract]
Disclosure of Share-based Compensation Arrangements by Share-based Payment Award	A combined summary of activity in our active stock plans is presented in the table below. Performance stock units outstanding are presented assuming attainment of the maximum payout rate as set forth by the performance criteria. As of March 31, 2022, there were 794,493 shares remaining available for grant for future stock-based compensation awards. Deferred Non-Vested Performance Stock Options Number Weighted- Number Weighted- Number Weighted- Number Weighted- Balance, January 1, 2022 56,301 $ 79.21 449,337 $ 93.05 202,460 $ 84.71 877,681 $ 69.02 Authorized — — — — — — — — Granted — — 1,038 145.32 — — — — Exercised/vested — — — — (25,180) 87.18 (90,250) 63.59 Forfeited/expired — — (1,786) 89.50 (16,058) 87.18 — — Balance, March 31, 2022 56,301 79.21 448,589 93.19 161,222 84.08 787,431 69.64
Shares Issued in Connection with Stock Compensation Awards	Shares issued in connection with stock compensation awards along with other related information were as follows: Three Months Ended 2022 2021 New shares issued from available authorized shares — — Shares issued from available treasury stock 115,430 513,824 Proceeds from stock option exercises $ 5,739 $ 29,397
Share-based Payment Arrangement, Cost by Plan	Stock-based compensation expense or benefit and the related income tax benefit is presented in the following table. The service period for performance stock units granted each year begins on January 1 of the following year. Three Months Ended 2022 2021 Non-vested stock units $ 2,358 $ 1,883 Performance stock units (246) 643 Total $ 2,112 $ 2,526 Income tax benefit $ 708 $ 367
Unrecognized Stock-Based Compensation Expense	Unrecognized stock-based compensation expense at March 31, 2022 is presented in the table below. Unrecognized stock-based compensation expense related to performance stock units is presented assuming attainment of the maximum payout rate as set forth by the performance criteria. Non-vested stock units $ 16,063 Performance stock units 8,664 Total $ 24,727

Earnings Per Common Share (Tabl

Earnings Per Common Share (Tables)	3 Months Ended
	Mar. 31, 2022
Earnings Per Share [Abstract]
Basic and Diluted Earnings Per Common Share	The following table presents a reconciliation of net income available to common shareholders, net earnings allocated to common stock and the number of shares used in the calculation of basic and diluted earnings per common share. Three Months Ended 2022 2021 Net income $ 99,102 $ 116,015 Less: Preferred stock dividends 1,669 2,151 Net income available to common shareholders 97,433 113,864 Less: Earnings allocated to participating securities 849 1,162 Net earnings allocated to common stock $ 96,584 $ 112,702 Distributed earnings allocated to common stock $ 48,051 $ 45,660 Undistributed earnings allocated to common stock 48,533 67,042 Net earnings allocated to common stock $ 96,584 $ 112,702 Weighted-average shares outstanding for basic earnings per common share 64,051,202 63,306,493 Dilutive effect of stock compensation 409,705 509,290 Weighted-average shares outstanding for diluted earnings per common share 64,460,907 63,815,783

Defined Benefit Plans (Tables)

Defined Benefit Plans (Tables)	3 Months Ended
	Mar. 31, 2022
Retirement Benefits [Abstract]
Net Periodic Cost (Benefit)	The components of the combined net periodic expense (benefit) for our defined benefit pension plans are presented in the table below. Three Months Ended 2022 2021 Expected return on plan assets, net of expenses $ (3,491) $ (3,210) Interest cost on projected benefit obligation 1,004 835 Net amortization and deferral 741 1,529 Net periodic expense (benefit) $ (1,746) $ (846)

Income Taxes (Tables)

Income Taxes (Tables)	3 Months Ended
	Mar. 31, 2022
Income Tax Disclosure [Abstract]
Income Tax Expense	Income tax expense was as follows: Three Months Ended 2022 2021 Current income tax expense (benefit) $ 13,059 $ 3,725 Deferred income tax expense (benefit) (432) 4,172 Income tax expense, as reported $ 12,627 $ 7,897 Effective tax rate 11.3 % 6.4 %

Other Comprehensive Income (L_2

Other Comprehensive Income (Loss) (Tables)	3 Months Ended
	Mar. 31, 2022
Equity [Abstract]
Comprehensive Income (Loss)	The before and after tax amounts allocated to each component of other comprehensive income (loss) are presented in the following table. Reclassification adjustments related to securities available for sale are included in net gain (loss) on securities transactions in the accompanying consolidated statements of income. Reclassification adjustments related to defined-benefit post-retirement benefit plans are included in the computation of net periodic pension expense (see Note 12 – Defined Benefit Plans). Three Months Ended Three Months Ended Before Tax Tax Expense, Net of Tax Before Tax Tax Expense, Net of Tax Securities available for sale and transferred securities: Change in net unrealized gain/loss during the period $ (910,795) $ (191,267) $ (719,528) $ (159,779) $ (33,554) $ (126,225) Change in net unrealized gain on securities transferred to held to maturity (209) (44) (165) (259) (54) (205) Reclassification adjustment for net (gains) losses included in net income — — — — — — Total securities available for sale and transferred securities (911,004) (191,311) (719,693) (160,038) (33,608) (126,430) Defined-benefit post-retirement benefit plans: Reclassification adjustment for net amortization of actuarial gain/loss included in net income as a component of net periodic expense (benefit) 741 156 585 1,529 321 1,208 Total defined-benefit post-retirement benefit plans 741 156 585 1,529 321 1,208 Total other comprehensive income (loss) $ (910,263) $ (191,155) $ (719,108) $ (158,509) $ (33,287) $ (125,222)
Schedule of Accumulated Other Comprehensive Income (Loss)	Activity in accumulated other comprehensive income (loss), net of tax, was as follows: Securities Defined Accumulated Balance January 1, 2022 $ 380,209 $ (32,891) $ 347,318 Other comprehensive income (loss) before reclassifications (719,693) — (719,693) Reclassification of amounts included in net income — 585 585 Net other comprehensive income (loss) during period (719,693) 585 (719,108) Balance at March 31, 2022 $ (339,484) $ (32,306) $ (371,790) Balance January 1, 2021 $ 563,801 $ (50,831) $ 512,970 Other comprehensive income (loss) before reclassifications (126,430) — (126,430) Reclassification of amounts included in net income — 1,208 1,208 Net other comprehensive income (loss) during period (126,430) 1,208 (125,222) Balance at March 31, 2021 $ 437,371 $ (49,623) $ 387,748

Operating Segments (Tables)

Operating Segments (Tables)	3 Months Ended
	Mar. 31, 2022
Segment Reporting [Abstract]
Summary of Operating Results by Segment	Summarized operating results by segment were as follows: Banking Frost Wealth Non-Banks Consolidated Three months ended: March 31, 2022 Net interest income (expense) $ 250,119 $ 700 $ (1,748) $ 249,071 Credit loss expense (benefit) (1) 1 — — Non-interest income 58,706 43,229 (545) 101,390 Non-interest expense 206,538 30,910 1,284 238,732 Income (loss) before income taxes 102,288 13,018 (3,577) 111,729 Income tax expense (benefit) 11,014 2,734 (1,121) 12,627 Net income (loss) 91,274 10,284 (2,456) 99,102 Preferred stock dividends — — 1,669 1,669 Net income (loss) available to common shareholders $ 91,274 $ 10,284 $ (4,125) $ 97,433 Revenues from (expenses to) external customers $ 308,825 $ 43,929 $ (2,293) $ 350,461 March 31, 2021 Net interest income (expense) $ 242,205 $ 486 $ (1,810) $ 240,881 Credit loss expense 63 — — 63 Non-interest income 53,780 39,609 (153) 93,236 Non-interest expense 179,151 29,937 1,054 210,142 Income (loss) before income taxes 116,771 10,158 (3,017) 123,912 Income tax expense (benefit) 7,177 2,133 (1,413) 7,897 Net income (loss) 109,594 8,025 (1,604) 116,015 Preferred stock dividends — — 2,151 2,151 Net income (loss) available to common shareholders $ 109,594 $ 8,025 $ (3,755) $ 113,864 Revenues from (expenses to) external customers $ 295,985 $ 40,095 $ (1,963) $ 334,117

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	3 Months Ended
	Mar. 31, 2022
Fair Value Disclosures [Abstract]
Financial Assets and Financial Liabilities Measured at Fair Value on Recurring Basis	The tables below summarize financial assets and financial liabilities measured at fair value on a recurring basis as of March 31, 2022 and December 31, 2021, segregated by the level of the valuation inputs within the fair value hierarchy of ASC Topic 820 utilized to measure fair value. Level 1 Inputs Level 2 Inputs Level 3 Inputs Total Fair Value March 31, 2022 Securities available for sale: U.S. Treasury $ 3,507,746 $ — $ — $ 3,507,746 Residential mortgage-backed securities — 5,376,039 — 5,376,039 States and political subdivisions — 7,258,393 — 7,258,393 Other — 42,361 — 42,361 Trading account securities: U.S. Treasury 23,939 — — 23,939 States and political subdivisions — 5,579 — 5,579 Derivative assets: Interest rate swaps, caps and floors — 33,697 — 33,697 Commodity swaps and options — 252,747 — 252,747 Foreign currency forward contracts 150 — — 150 Derivative liabilities: Interest rate swaps, caps and floors — 39,734 — 39,734 Commodity swaps and options — 251,181 — 251,181 Foreign currency forward contracts 131 — — 131 December 31, 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
Impaired Loans Remeasured And Reported At Fair Value Specific Valuation Allowance Allocation Method Of Underlying Collateral [Table Text Block]	The following table presents collateral dependent loans that were remeasured and reported at fair value through a specific allocation of the allowance for credit losses on loans based upon the fair value of the underlying collateral during the reported periods. Three Months Ended Three Months Ended Level 2 Level 3 Level 2 Level 3 Carrying value before allocations $ 2,064 $ 5,711 $ 100 $ 15,013 Specific (allocations) reversals of prior allocations (126) 3,965 — 600 Fair value $ 1,938 $ 9,676 $ 100 $ 15,613
Estimated Fair Values of Financial Instruments	The estimated fair values of financial instruments that are reported at amortized cost in our consolidated balance sheets, segregated by the level of the valuation inputs within the fair value hierarchy utilized to measure fair value, were as follows: March 31, 2022 December 31, 2021 Carrying Estimated Carrying Estimated Financial assets: Level 2 inputs: Cash and cash equivalents $ 14,457,083 $ 14,457,083 $ 16,583,000 $ 16,583,000 Securities held to maturity 1,665,465 1,639,993 1,749,179 1,809,143 Cash surrender value of life insurance policies 189,471 189,471 190,139 190,139 Accrued interest receivable 131,370 131,370 179,111 179,111 Level 3 inputs: Loans, net 16,295,702 16,053,955 16,087,731 16,079,454 Financial liabilities: Level 2 inputs: Deposits 44,430,929 44,422,700 42,695,696 41,343,426 Federal funds purchased 35,200 35,200 25,925 25,925 Repurchase agreements 1,842,618 1,842,618 2,740,799 2,740,799 Junior subordinated deferrable interest debentures 123,026 123,712 123,011 123,712 Subordinated notes 99,217 105,740 99,178 111,430 Accrued interest payable 2,147 2,147 3,026 3,026

Significant Accounting Polici_4

Significant Accounting Policies - Additional Cash Flow Information (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Accounting Policies [Abstract]
Cash paid for interest	$ 8,069	$ 9,719
Cash paid for income taxes	0	0
Unsettled securities transactions	78,769	21,957
Right-of-use lease assets obtained in exchange for lessee operating lease liabilities	4,013	1,326
Treasury stock issued to 401(k) stock purchase plan	$ 0	$ 1,749

Securities - Additional Informa

Securities - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021	Dec. 31, 2021
Schedule Of Marketable Securities [Line Items]
AOCI, Debt Securities, Available-for-sale, Adjustment, Pre Tax	$ 2,300		$ 2,500
Net unamortized unrealized gain on transferred securities included in accumulated other comprehensive income, net of tax	$ 1,800		2,000
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	75.70%
Debt Securities, Available-for-sale, Allowance for Credit Loss	$ 0		0
Proceeds from Sale of Debt Securities, Available-for-sale	0	$ 0
Proceeds from Sale of Held-to-maturity Securities	0	$ 0
Held-to-maturity Securities [Member]
Schedule Of Marketable Securities [Line Items]
Carry value of securities pledged	252,000		642,300
Accrued interest receivable	10,000		18,400
Available-for-sale Securities [Member]
Schedule Of Marketable Securities [Line Items]
Carry value of securities pledged	4,800,000		5,800,000
Accrued interest receivable	$ 80,800		$ 120,500

Securities Securities - Amortiz

Securities Securities - Amortized Cost, Allowance for Credit Losses and Estimated Fair Value of Securities Held to Maturity (Details) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Schedule of Investments [Line Items]
Held to Maturity, Amortized Cost	$ 1,665,623	$ 1,749,337
Debt Securities, Held-to-maturity, Accumulated Unrecognized Gain	3,622	59,907
Debt Securities, Held-to-maturity, Accumulated Unrecognized Loss	29,252	101
Debt Securities, Held-to-maturity, Fair Value	1,639,993	1,809,143
Securities, held-to-maturity, allowance for credit loss	(158)	(158)
Securities held to maturity, net of allowance for credit losses of $158 at March 31, 2022 and $158 at December 31, 2021	1,665,465	1,749,179
Residential Mortgage Backed Securities [Member]
Schedule of Investments [Line Items]
Held to Maturity, Amortized Cost	526,969	527,264
Debt Securities, Held-to-maturity, Accumulated Unrecognized Gain	0	18,766
Debt Securities, Held-to-maturity, Accumulated Unrecognized Loss	17,519	0
Debt Securities, Held-to-maturity, Fair Value	509,450	546,030
Securities, held-to-maturity, allowance for credit loss	0	0
Securities held to maturity, net of allowance for credit losses of $158 at March 31, 2022 and $158 at December 31, 2021	526,969	527,264
US States and Political Subdivisions Debt Securities [Member]
Schedule of Investments [Line Items]
Held to Maturity, Amortized Cost	1,137,154	1,220,573
Debt Securities, Held-to-maturity, Accumulated Unrecognized Gain	3,622	41,141
Debt Securities, Held-to-maturity, Accumulated Unrecognized Loss	11,717	101
Debt Securities, Held-to-maturity, Fair Value	1,129,059	1,261,613
Securities, held-to-maturity, allowance for credit loss	(158)	(158)
Securities held to maturity, net of allowance for credit losses of $158 at March 31, 2022 and $158 at December 31, 2021	1,136,996	1,220,415
Other Investments [Member]
Schedule of Investments [Line Items]
Held to Maturity, Amortized Cost	1,500	1,500
Debt Securities, Held-to-maturity, Accumulated Unrecognized Gain	0	0
Debt Securities, Held-to-maturity, Accumulated Unrecognized Loss	16	0
Debt Securities, Held-to-maturity, Fair Value	1,484	1,500
Securities, held-to-maturity, allowance for credit loss	0	0
Securities held to maturity, net of allowance for credit losses of $158 at March 31, 2022 and $158 at December 31, 2021	$ 1,500	$ 1,500

Securities Securities - Moody's

Securities Securities - Moody's and/or Standard & Poor's Bond Rating (Details) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-maturity	$ 1,665,623	$ 1,749,337
US States and Political Subdivisions Debt Securities [Member]
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-maturity	1,137,154	1,220,573
Other Investments [Member]
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-maturity	1,500	1,500
Aaa/AAA [Member] | US States and Political Subdivisions Debt Securities [Member]
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-maturity	1,029,256	1,116,278
Aaa/AAA [Member] | Other Investments [Member]
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-maturity	0	0
Aa/AA [Member] | US States and Political Subdivisions Debt Securities [Member]
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-maturity	107,898	104,295
Aa/AA [Member] | Other Investments [Member]
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-maturity	0	0
Not rated [Member] | US States and Political Subdivisions Debt Securities [Member]
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-maturity	0	0
Not rated [Member] | Other Investments [Member]
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-maturity	1,500	1,500
Not Guaranteed or Pre-Refunded [Member] | US States and Political Subdivisions Debt Securities [Member]
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-maturity	198,932	196,674
Not Guaranteed or Pre-Refunded [Member] | Aaa/AAA [Member] | US States and Political Subdivisions Debt Securities [Member]
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-maturity	91,034	92,379
Not Guaranteed or Pre-Refunded [Member] | Aa/AA [Member] | US States and Political Subdivisions Debt Securities [Member]
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-maturity	107,898	104,295
Not Guaranteed or Pre-Refunded [Member] | Not rated [Member] | US States and Political Subdivisions Debt Securities [Member]
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-maturity	0	0
Guaranteed by the Texas PSF [Member] | US States and Political Subdivisions Debt Securities [Member]
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-maturity	467,039	460,648
Guaranteed by the Texas PSF [Member] | Aaa/AAA [Member] | US States and Political Subdivisions Debt Securities [Member]
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-maturity	467,039	460,648
Guaranteed by the Texas PSF [Member] | Aa/AA [Member] | US States and Political Subdivisions Debt Securities [Member]
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-maturity	0	0
Guaranteed by the Texas PSF [Member] | Not rated [Member] | US States and Political Subdivisions Debt Securities [Member]
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-maturity	0	0
Pre-Refunded [Member] | US States and Political Subdivisions Debt Securities [Member]
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-maturity	471,183	563,251
Pre-Refunded [Member] | Aaa/AAA [Member] | US States and Political Subdivisions Debt Securities [Member]
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-maturity	471,183	563,251
Pre-Refunded [Member] | Aa/AA [Member] | US States and Political Subdivisions Debt Securities [Member]
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-maturity	0	0
Pre-Refunded [Member] | Not rated [Member] | US States and Political Subdivisions Debt Securities [Member]
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-maturity	$ 0	$ 0

Securities Securities - Allowan

Securities Securities - Allowance for Credit Losses on Held to Maturity Securities (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021	Dec. 31, 2021	Dec. 31, 2020
Schedule of Held-to-maturity Securities [Line Items]
Securities, held-to-maturity, allowance for credit loss	$ 158		$ 158
Debt Securities [Member]
Schedule of Held-to-maturity Securities [Line Items]
Securities, held-to-maturity, allowance for credit loss	158	$ 158	$ 158	$ 160
Credit loss expense (benefit)	$ 0	$ (2)

Securities Securities - Amort_2

Securities Securities - Amortized Cost, Allowance for Credit Losses and Estimated Fair Value of Securities Available for Sale (Details) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Schedule of Investments [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	$ 16,616,594	$ 13,445,888
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	144,335	518,805
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	576,390	40,065
Debt Securities, Available-for-sale, Allowance for Credit Loss	0	0
Securities available for sale, at estimated fair value	16,184,539	13,924,628
US Treasury Securities [Member]
Schedule of Investments [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	3,658,506	2,165,702
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	1,883	23,333
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	152,643	9,602
Debt Securities, Available-for-sale, Allowance for Credit Loss	0	0
Securities available for sale, at estimated fair value	3,507,746	2,179,433
Residential Mortgage Backed Securities [Member]
Schedule of Investments [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	5,696,906	4,059,692
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	7,246	31,662
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	328,113	25,089
Debt Securities, Available-for-sale, Allowance for Credit Loss	0	0
Securities available for sale, at estimated fair value	5,376,039	4,066,265
US States and Political Subdivisions Debt Securities [Member]
Schedule of Investments [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	7,218,821	7,178,135
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	135,206	463,810
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	95,634	5,374
Debt Securities, Available-for-sale, Allowance for Credit Loss	0	0
Securities available for sale, at estimated fair value	7,258,393	7,636,571
Other Investments [Member]
Schedule of Investments [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	42,361	42,359
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	0	0
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	0	0
Debt Securities, Available-for-sale, Allowance for Credit Loss	0	0
Securities available for sale, at estimated fair value	$ 42,361	$ 42,359

Securities - Securities Availab

Securities - Securities Available for Sale, with Unrealized Losses Segregated by Length of Impairment (Detail) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Schedule of Available-for-Sale Securities [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	$ 9,037,646
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	532,200
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	416,542
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	44,190
Debt Securities, Available-for-sale, Unrealized Loss Position	9,454,188
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	576,390	$ 40,065
U.S. Treasury [Member]
Schedule of Available-for-Sale Securities [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	3,220,375
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	152,643
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
Debt Securities, Available-for-sale, Unrealized Loss Position	3,220,375
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	152,643	9,602
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	4,583,657
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	286,421
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	402,940
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	41,692
Debt Securities, Available-for-sale, Unrealized Loss Position	4,986,597
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	328,113	25,089
States and political subdivisions [Member]
Schedule of Available-for-Sale Securities [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	1,233,614
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	93,136
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	13,602
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	2,498
Debt Securities, Available-for-sale, Unrealized Loss Position	1,247,216
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	$ 95,634	$ 5,374

Securities - Amortized Cost and

Securities - Amortized Cost and Estimated Fair Value of Securities, Excluding Trading Securities, Presented by Contractual Maturity (Detail) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Schedule of Investments [Line Items]
Held to Maturity, Due in one year or less, Amortized Cost	$ 429,868
Held to Maturity, Due after one year through five years, Amortized Cost	120,016
Held to Maturity, Due after five years through ten years, Amortized Cost	571,577
Held to Maturity, Due after ten years, Amortized Cost	544,162
Held to Maturity, Amortized Cost	1,665,623	$ 1,749,337
Held to Maturity, Due in one year or less, Estimated Fair Value	431,977
Held to Maturity, Due after one year through five years, Estimated Fair Value	121,182
Held to Maturity, Due after five years through ten years, Estimated Fair Value	555,051
Held to Maturity, Due after ten years, Estimated Fair Value	531,783
Held to Maturity, Estimated Fair Value	1,639,993	1,809,143
Available-for-sale Securities, Due in one year or less, Amortized Cost	194,518
Available for Sale, Due after one year through five years, Amortized Cost	3,610,741
Available for Sale, Due after five years through ten years, Amortized Cost	2,340,280
Available for Sale, Due after ten years, Amortized Cost	10,428,694
Debt Securities, Available-for-sale, Amortized Cost	16,616,594	13,445,888
Available for Sale, Due in one year or less, Estimated Fair Value	197,334
Available for Sale, Due after one year through five years, Estimated Fair Value	3,596,062
Available for Sale, Due after five years through ten years, Estimated Fair Value	2,269,482
Available for Sale, Due after ten years, Estimated Fair Value	10,079,300
Securities available for sale, at estimated fair value	16,184,539	13,924,628
US Treasury Securities [Member]
Schedule of Investments [Line Items]
Available-for-sale Securities, Due in one year or less, Amortized Cost	0
Available for Sale, Due after one year through five years, Amortized Cost	2,033,995
Available for Sale, Due after five years through ten years, Amortized Cost	1,432,731
Available for Sale, Due after ten years, Amortized Cost	191,780
Debt Securities, Available-for-sale, Amortized Cost	3,658,506	2,165,702
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	1,978,865
Available for Sale, Due after five years through ten years, Estimated Fair Value	1,350,553
Available for Sale, Due after ten years, Estimated Fair Value	178,328
Securities available for sale, at estimated fair value	3,507,746	2,179,433
Residential Mortgage Backed Securities [Member]
Schedule of Investments [Line Items]
Held to Maturity, Due in one year or less, Amortized Cost	16
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	514,842
Held to Maturity, Due after ten years, Amortized Cost	12,111
Held to Maturity, Amortized Cost	526,969	527,264
Held to Maturity, Due in one year or less, Estimated Fair Value	16
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	498,078
Held to Maturity, Due after ten years, Estimated Fair Value	11,356
Held to Maturity, Estimated Fair Value	509,450	546,030
Available-for-sale Securities, Due in one year or less, Amortized Cost	102
Available for Sale, Due after one year through five years, Amortized Cost	12,917
Available for Sale, Due after five years through ten years, Amortized Cost	19,060
Available for Sale, Due after ten years, Amortized Cost	5,664,827
Debt Securities, Available-for-sale, Amortized Cost	5,696,906	4,059,692
Available for Sale, Due in one year or less, Estimated Fair Value	103
Available for Sale, Due after one year through five years, Estimated Fair Value	13,212
Available for Sale, Due after five years through ten years, Estimated Fair Value	19,327
Available for Sale, Due after ten years, Estimated Fair Value	5,343,397
Securities available for sale, at estimated fair value	5,376,039	4,066,265
US States and Political Subdivisions Debt Securities [Member]
Schedule of Investments [Line Items]
Held to Maturity, Due in one year or less, Amortized Cost	429,852
Held to Maturity, Due after one year through five years, Amortized Cost	118,516
Held to Maturity, Due after five years through ten years, Amortized Cost	56,735
Held to Maturity, Due after ten years, Amortized Cost	532,051
Held to Maturity, Amortized Cost	1,137,154	1,220,573
Held to Maturity, Due in one year or less, Estimated Fair Value	431,961
Held to Maturity, Due after one year through five years, Estimated Fair Value	119,698
Held to Maturity, Due after five years through ten years, Estimated Fair Value	56,973
Held to Maturity, Due after ten years, Estimated Fair Value	520,427
Held to Maturity, Estimated Fair Value	1,129,059	1,261,613
Available-for-sale Securities, Due in one year or less, Amortized Cost	194,416
Available for Sale, Due after one year through five years, Amortized Cost	1,563,829
Available for Sale, Due after five years through ten years, Amortized Cost	888,489
Available for Sale, Due after ten years, Amortized Cost	4,572,087
Debt Securities, Available-for-sale, Amortized Cost	7,218,821	7,178,135
Available for Sale, Due in one year or less, Estimated Fair Value	197,231
Available for Sale, Due after one year through five years, Estimated Fair Value	1,603,985
Available for Sale, Due after five years through ten years, Estimated Fair Value	899,602
Available for Sale, Due after ten years, Estimated Fair Value	4,557,575
Securities available for sale, at estimated fair value	7,258,393	7,636,571
Other Investments [Member]
Schedule of Investments [Line Items]
Held to Maturity, Due in one year or less, Amortized Cost	0
Held to Maturity, Due after one year through five years, Amortized Cost	1,500
Held to Maturity, Due after five years through ten years, Amortized Cost	0
Held to Maturity, Due after ten years, Amortized Cost	0
Held to Maturity, Amortized Cost	1,500	1,500
Held to Maturity, Due in one year or less, Estimated Fair Value	0
Held to Maturity, Due after one year through five years, Estimated Fair Value	1,484
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	1,484	1,500
Available-for-sale Securities, Due in one year or less, Amortized Cost	0
Available for Sale, Due after one year through five years, Amortized Cost	0
Available for Sale, Due after five years through ten years, Amortized Cost	0
Available for Sale, Due after ten years, Amortized Cost	0
Debt Securities, Available-for-sale, Amortized Cost	42,361	42,359
Available for Sale, Due in one year or less, Estimated Fair Value	0
Available for Sale, Due after one year through five years, Estimated Fair Value	0
Available for Sale, Due after five years through ten years, Estimated Fair Value	0
Available for Sale, Due after ten years, Estimated Fair Value	0
Securities available for sale, at estimated fair value	$ 42,361	$ 42,359

Securities Securities - Premium

Securities Securities - Premium Amortization and Discount Accretion Included in Income on Securities (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Investments, Debt and Equity Securities [Abstract]
Premium amortization	$ (29,060)	$ (31,235)
Discount accretion	1,406	637
Net (premium amortization) discount accretion	$ (27,654)	$ (30,598)

Securities - Trading Account Se

Securities - Trading Account Securities, at Estimated Fair Value (Detail) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Debt and Equity Securities, FV-NI [Line Items]
Trading account securities	$ 29,518	$ 25,162
U.S. Treasury [Member]
Debt and Equity Securities, FV-NI [Line Items]
Trading account securities	23,939	24,237
States and political subdivisions [Member]
Debt and Equity Securities, FV-NI [Line Items]
Trading account securities	$ 5,579	$ 925

Securities - Net Gains and Loss

Securities - Net Gains and Losses on Trading Account Securities (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Investments, Debt and Equity Securities [Abstract]
Net gain on sales transactions	$ 340	$ 109
Net mark-to-market gains (losses)	(168)	(69)
Net gain (loss) on trading account securities	$ 172	$ 40

Loans - Additional Information

Loans - Additional Information (Detail) $ in Thousands	3 Months Ended
	Mar. 31, 2022USD ($)	Mar. 31, 2021USD ($)	Dec. 31, 2021USD ($)	Dec. 31, 2020USD ($)
Accounts, Notes, Loans and Financing Receivable [Line Items]
Concentration of loans in a single industry in excess of ten percent	0.00%
Maximum percentage loan related to single industry	10.00%
U.S. dollar denominated loans and commitments to borrowers in Mexico	$ 0		$ 0
Loans and Leases Receivable, Related Parties	346,500		$ 350,500
Loans modified as troubled debt restructurings	$ 0	$ 0
Texas Leading Index economic condition indicator	141.2		135.9
Financing Receivable, Allowance for Credit Loss	$ 246,835		$ 248,666
Commercial and Industrial Total Energy Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Percentage of total energy loans to total loans	6.30%
Percentage of total energy loans to total loans excluding PPP Loans	6.30%
Financing Receivable, Allowance for Credit Loss	$ 15,422	33,472	17,217	$ 39,553
Paycheck Protection Program [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Allowance for Credit Loss	0	0	0
Non Accrual Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Additional interest that would have been recognized on non-accrual loans, net of tax	407	$ 453
Commitments to Extend Credit [Member] | Commercial and Industrial Total Energy Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unfunded balances	862,200
Standby Letters of Credit [Member] | Commercial and Industrial Total Energy Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unfunded balances	76,000
Loans Receivable [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Interest Receivable	$ 39,500		$ 40,000

Loans - Loans (Detail)

Loans - Loans (Detail) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	$ 16,542,537	$ 16,336,397
Commercial Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	5,584,117	5,364,954
Energy Production [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	820,107	878,436
Energy Service [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	113,708	105,901
Energy Other [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	102,764	93,455
Commercial and Industrial Total Energy Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	1,036,579	1,077,792
Paycheck Protection Program [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	207,669	428,882
Commercial mortgage [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	5,918,011	5,867,062
Construction Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	1,421,878	1,304,271
Commercial land loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	458,510	405,277
Commercial Real Estate Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	7,798,399	7,576,610
Home Equity Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	321,842	324,157
Home Equity Line of Credit [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	544,822	519,098
Other consumer real estate loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	566,961	567,535
Total consumer real estate loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	1,433,625	1,410,790
Real Estate Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	9,232,024	8,987,400
Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	$ 482,148	$ 477,369

Loans - Non-Accrual Loans, Segr

Loans - Non-Accrual Loans, Segregated by Class of Loans (Detail) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Non Accrual Loans Segregated By Class Of Loans [Line Items]
Non-accrual loans	$ 48,966	$ 53,713
Non-accrual with no credit loss allowance	30,749	27,202
Commercial Portfolio Segment [Member]
Non Accrual Loans Segregated By Class Of Loans [Line Items]
Non-accrual loans	16,693	22,582
Non-accrual with no credit loss allowance	6,135	4,701
Commercial and Industrial Total Energy Loans [Member]
Non Accrual Loans Segregated By Class Of Loans [Line Items]
Non-accrual loans	12,271	14,433
Non-accrual with no credit loss allowance	6,912	8,533
Paycheck Protection Program [Member]
Non Accrual Loans Segregated By Class Of Loans [Line Items]
Non-accrual loans	0	0
Non-accrual with no credit loss allowance	0	0
Commercial Real Estate Buildings Land And Other Loans [Member]
Non Accrual Loans Segregated By Class Of Loans [Line Items]
Non-accrual loans	19,003	15,297
Non-accrual with no credit loss allowance	17,005	13,817
Construction Loans [Member]
Non Accrual Loans Segregated By Class Of Loans [Line Items]
Non-accrual loans	583	948
Non-accrual with no credit loss allowance	583	0
Total consumer real estate loans [Member]
Non Accrual Loans Segregated By Class Of Loans [Line Items]
Non-accrual loans	416	440
Non-accrual with no credit loss allowance	114	138
Consumer Loan [Member]
Non Accrual Loans Segregated By Class Of Loans [Line Items]
Non-accrual loans	0	13
Non-accrual with no credit loss allowance	$ 0	$ 13

Loans Loans - Non-Accrual Loans

Loans Loans - Non-Accrual Loans, Segregated by Class of Loans and Year of Origination (Details) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Loans and Leases Receivable Disclosure [Line Items]
Non-accrual loans	$ 48,966	$ 53,713
Nonperforming Financial Instruments [Member]
Loans and Leases Receivable Disclosure [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	0
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	8,885
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	4,980
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	10,148
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	3,083
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	4,355
Financing Receivable, Revolving	8,035
Financing Receivable, Revolving, Converted to Term Loan	9,480
Commercial Portfolio Segment [Member]
Loans and Leases Receivable Disclosure [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	844,354
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	953,664
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	616,642
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	331,729
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	189,719
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	255,999
Financing Receivable, Revolving	2,331,781
Non-accrual loans	16,693	22,582
Commercial Portfolio Segment [Member] | Nonperforming Financial Instruments [Member]
Loans and Leases Receivable Disclosure [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	0
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	478
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	4,101
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	3,910
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	1,552
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	1,033
Financing Receivable, Revolving	2,038
Financing Receivable, Revolving, Converted to Term Loan	3,581
Commercial and Industrial Total Energy Loans [Member]
Loans and Leases Receivable Disclosure [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	289,573
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	125,803
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	8,629
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	18,726
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	6,603
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	5,843
Financing Receivable, Revolving	521,322
Non-accrual loans	12,271	14,433
Commercial and Industrial Total Energy Loans [Member] | Nonperforming Financial Instruments [Member]
Loans and Leases Receivable Disclosure [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	0
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	0
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	0
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	5,039
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	1,137
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	0
Financing Receivable, Revolving	5,997
Financing Receivable, Revolving, Converted to Term Loan	98
Paycheck Protection Program [Member]
Loans and Leases Receivable Disclosure [Line Items]
Non-accrual loans	0	0
Paycheck Protection Program [Member] | Nonperforming Financial Instruments [Member]
Loans and Leases Receivable Disclosure [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	0
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	0
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	0
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	0
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	0
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	0
Financing Receivable, Revolving	0
Financing Receivable, Revolving, Converted to Term Loan	0
Commercial Real Estate Buildings Land And Other Loans [Member]
Loans and Leases Receivable Disclosure [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	660,171
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	1,606,760
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	1,231,072
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	938,002
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	553,657
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	1,200,107
Financing Receivable, Revolving	81,435
Non-accrual loans	19,003	15,297
Commercial Real Estate Buildings Land And Other Loans [Member] | Nonperforming Financial Instruments [Member]
Loans and Leases Receivable Disclosure [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	0
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	8,407
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	296
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	1,199
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	394
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	2,932
Financing Receivable, Revolving	0
Financing Receivable, Revolving, Converted to Term Loan	5,775
Construction Loans [Member]
Loans and Leases Receivable Disclosure [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	202,584
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	662,966
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	201,069
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	141,510
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	636
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	2,265
Financing Receivable, Revolving	207,182
Non-accrual loans	583	948
Construction Loans [Member] | Nonperforming Financial Instruments [Member]
Loans and Leases Receivable Disclosure [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	0
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	0
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	583
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	0
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	0
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	0
Financing Receivable, Revolving	0
Financing Receivable, Revolving, Converted to Term Loan	0
Total consumer real estate loans [Member]
Loans and Leases Receivable Disclosure [Line Items]
Non-accrual loans	416	440
Total consumer real estate loans [Member] | Nonperforming Financial Instruments [Member]
Loans and Leases Receivable Disclosure [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	0
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	0
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	0
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	0
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	0
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	390
Financing Receivable, Revolving	0
Financing Receivable, Revolving, Converted to Term Loan	26
Consumer Loan [Member]
Loans and Leases Receivable Disclosure [Line Items]
Non-accrual loans	0	$ 13
Consumer Loan [Member] | Nonperforming Financial Instruments [Member]
Loans and Leases Receivable Disclosure [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	0
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	0
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	0
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	0
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	0
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	0
Financing Receivable, Revolving	0
Financing Receivable, Revolving, Converted to Term Loan	$ 0

Loans - Age Analysis of Past Du

Loans - Age Analysis of Past Due Loans, Segregated by Class of Loans (Detail) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Financing Receivable, Past Due [Line Items]
Total loans	$ 16,542,537	$ 16,336,397
Accruing Loans 90 or More Days Past Due	16,572
Commercial Portfolio Segment [Member]
Financing Receivable, Past Due [Line Items]
Total loans	5,584,117	5,364,954
Accruing Loans 90 or More Days Past Due	4,166
Commercial and Industrial Total Energy Loans [Member]
Financing Receivable, Past Due [Line Items]
Total loans	1,036,579	1,077,792
Accruing Loans 90 or More Days Past Due	287
Paycheck Protection Program [Member]
Financing Receivable, Past Due [Line Items]
Total loans	207,669	428,882
Accruing Loans 90 or More Days Past Due	8,377
Commercial Real Estate Buildings Land And Other Loans [Member]
Financing Receivable, Past Due [Line Items]
Total loans	6,376,521	6,272,339
Accruing Loans 90 or More Days Past Due	1,046
Construction Loans [Member]
Financing Receivable, Past Due [Line Items]
Total loans	1,421,878	1,304,271
Accruing Loans 90 or More Days Past Due	0
Total consumer real estate loans [Member]
Financing Receivable, Past Due [Line Items]
Total loans	1,433,625	1,410,790
Accruing Loans 90 or More Days Past Due	2,103
Consumer Loan [Member]
Financing Receivable, Past Due [Line Items]
Total loans	482,148	$ 477,369
Accruing Loans 90 or More Days Past Due	593
Financing Receivables, 30 to 89 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	47,820
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	13,016
Financing Receivables, 30 to 89 Days Past Due [Member] | Commercial and Industrial Total Energy Loans [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	0
Financing Receivables, 30 to 89 Days Past Due [Member] | Paycheck Protection Program [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	671
Financing Receivables, 30 to 89 Days Past Due [Member] | Commercial Real Estate Buildings Land And Other Loans [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	21,542
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	1,988
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	4,210
Financing Receivables, 30 to 89 Days Past Due [Member] | Consumer Loan [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	6,393
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	37,349
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	8,042
Financial Asset, Equal to or Greater than 90 Days Past Due [Member] | Commercial and Industrial Total Energy Loans [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	6,382
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	8,377
Financial Asset, Equal to or Greater than 90 Days Past Due [Member] | Commercial Real Estate Buildings Land And Other Loans [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	11,546
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	2,409
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	593
Financial Asset, Past Due
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	85,169
Financial Asset, Past Due | Commercial Portfolio Segment [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	21,058
Financial Asset, Past Due | Commercial and Industrial Total Energy Loans [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	6,382
Financial Asset, Past Due | Paycheck Protection Program [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	9,048
Financial Asset, Past Due | Commercial Real Estate Buildings Land And Other Loans [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	33,088
Financial Asset, Past Due | Construction Loans [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	1,988
Financial Asset, Past Due | Total consumer real estate loans [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	6,619
Financial Asset, Past Due | Consumer Loan [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	6,986
Financial Asset, Not Past Due
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	16,457,368
Financial Asset, Not Past Due | Commercial Portfolio Segment [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	5,563,059
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	1,030,197
Financial Asset, Not Past Due | Paycheck Protection Program [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	198,621
Financial Asset, Not Past Due | Commercial Real Estate Buildings Land And Other Loans [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	6,343,433
Financial Asset, Not Past Due | Construction Loans [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	1,419,890
Financial Asset, Not Past Due | Total consumer real estate loans [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	1,427,006
Financial Asset, Not Past Due | Consumer Loan [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	$ 475,162

Loans Loans - Restructured Loan

Loans Loans - Restructured Loans Past Due in Excess of 90 Days on Financing Receivables (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2022USD ($)Item	Mar. 31, 2021USD ($)Item
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number Of Restructured Loans Past Due In Excess of 90 Days At Period-End | Item	2	2
Dollar amount of previously restructured loans past due	$ 572	$ 1,392
Charge-offs of restructured loans recognized on previously restructured loans	$ 723	$ 1,433

Loans Loans - Weighted Average

Loans Loans - Weighted Average Risk Grade for All Commercial Loans by Class and Year of Origination (Details) $ in Thousands	Mar. 31, 2022USD ($)Grade	Dec. 31, 2021USD ($)Grade
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Net of Deferred Income	$ 16,542,537	$ 16,336,397
Commercial Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	844,354
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	953,664
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	616,642
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	331,729
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	189,719
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	255,999
Financing Receivable, Revolving	2,331,781
Loans and Leases Receivable, Net of Deferred Income	$ 5,584,117	$ 5,364,954
Weighted Average Risk Grade For Loans | Grade	6.34	6.22
Commercial and Industrial Total Energy Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	$ 289,573
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	125,803
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	8,629
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	18,726
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	6,603
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	5,843
Financing Receivable, Revolving	521,322
Loans and Leases Receivable, Net of Deferred Income	$ 1,036,579	$ 1,077,792
Weighted Average Risk Grade For Loans | Grade	5.89	6.06
Commercial Real Estate Buildings Land And Other Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	$ 660,171
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	1,606,760
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	1,231,072
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	938,002
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	553,657
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	1,200,107
Financing Receivable, Revolving	81,435
Loans and Leases Receivable, Net of Deferred Income	$ 6,376,521	$ 6,272,339
Weighted Average Risk Grade For Loans | Grade	7.14	7.22
Construction Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	$ 202,584
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	662,966
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	201,069
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	141,510
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	636
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	2,265
Financing Receivable, Revolving	207,182
Loans and Leases Receivable, Net of Deferred Income	$ 1,421,878	$ 1,304,271
Weighted Average Risk Grade For Loans | Grade	7.01	7.06
Commercial Real Estate Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	$ 862,755
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	2,269,726
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	1,432,141
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	1,079,512
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	554,293
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	1,202,372
Financing Receivable, Revolving	288,617
Loans and Leases Receivable, Net of Deferred Income	$ 7,798,399	$ 7,576,610
Weighted Average Risk Grade For Loans | Grade	7.11	7.19
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	$ 836,152
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	894,663
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	592,780
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	305,667
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	160,622
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	243,869
Financing Receivable, Revolving	2,255,878
Loans and Leases Receivable, Net of Deferred Income	$ 5,334,409	$ 5,063,847
Weighted Average Risk Grade For Loans | Grade	6.18	6.01
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	$ 279,051
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	125,435
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	7,519
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	8,444
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	4,068
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	5,665
Financing Receivable, Revolving	509,657
Loans and Leases Receivable, Net of Deferred Income	$ 999,263	$ 1,008,370
Weighted Average Risk Grade For Loans | Grade	5.71	5.78
Risk Grade One To Eight [Member] | Commercial Real Estate Buildings Land And Other Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	$ 607,883
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	1,554,611
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	1,113,230
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	809,206
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	498,477
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	1,057,840
Financing Receivable, Revolving	72,704
Loans and Leases Receivable, Net of Deferred Income	$ 5,810,875	$ 5,574,922
Weighted Average Risk Grade For Loans | Grade	6.89	6.91
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	$ 202,413
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	634,897
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	195,127
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	141,510
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	636
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	1,842
Financing Receivable, Revolving	207,182
Loans and Leases Receivable, Net of Deferred Income	$ 1,387,273	$ 1,262,200
Weighted Average Risk Grade For Loans | Grade	6.96	6.99
Risk Grade One To Eight [Member] | Commercial Real Estate Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Net of Deferred Income		$ 6,837,122
Weighted Average Risk Grade For Loans | Grade		6.92
Risk Grade Nine [Member] | Commercial Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	$ 4,702
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	34,513
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	6,562
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	11,434
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	21,841
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	8,319
Financing Receivable, Revolving	54,008
Loans and Leases Receivable, Net of Deferred Income	$ 146,100	$ 187,870
Weighted Average Risk Grade For Loans | Grade	9	9
Risk Grade Nine [Member] | Commercial and Industrial Total Energy Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	$ 1,425
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	103
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	508
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	1,407
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	96
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	0
Financing Receivable, Revolving	5,668
Loans and Leases Receivable, Net of Deferred Income	$ 9,250	$ 36,622
Weighted Average Risk Grade For Loans | Grade	9	9
Risk Grade Nine [Member] | Commercial Real Estate Buildings Land And Other Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	$ 6,163
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	20,766
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	108,943
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	53,448
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	23,459
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	45,034
Financing Receivable, Revolving	5,516
Loans and Leases Receivable, Net of Deferred Income	$ 265,947	$ 321,533
Weighted Average Risk Grade For Loans | Grade	9	9
Risk Grade Nine [Member] | Construction Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	$ 171
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	28,069
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	5,359
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	0
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	0
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	423
Financing Receivable, Revolving	0
Loans and Leases Receivable, Net of Deferred Income	$ 34,022	$ 41,123
Weighted Average Risk Grade For Loans | Grade	9	9
Risk Grade Nine [Member] | Commercial Real Estate Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Net of Deferred Income		$ 362,656
Weighted Average Risk Grade For Loans | Grade		9
Risk Grade Ten [Member] | Commercial Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	$ 3,500
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	22,084
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	6,527
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	1,039
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	4,007
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	578
Financing Receivable, Revolving	13,899
Loans and Leases Receivable, Net of Deferred Income	$ 52,832	$ 59,137
Weighted Average Risk Grade For Loans | Grade	10	10
Risk Grade Ten [Member] | Commercial and Industrial Total Energy Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	$ 0
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	0
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	90
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	580
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	351
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	0
Financing Receivable, Revolving	0
Loans and Leases Receivable, Net of Deferred Income	$ 1,536	$ 1,773
Weighted Average Risk Grade For Loans | Grade	10	10
Risk Grade Ten [Member] | Commercial Real Estate Buildings Land And Other Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	$ 46,125
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	22,716
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	7,310
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	66,821
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	24,539
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	57,602
Financing Receivable, Revolving	0
Loans and Leases Receivable, Net of Deferred Income	$ 225,113	$ 269,447
Weighted Average Risk Grade For Loans | Grade	10	10
Risk Grade Ten [Member] | Construction Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	$ 0
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	0
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	0
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	0
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	0
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	0
Financing Receivable, Revolving	0
Loans and Leases Receivable, Net of Deferred Income	$ 0	$ 0
Weighted Average Risk Grade For Loans | Grade	10	10
Risk Grade Ten [Member] | Commercial Real Estate Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Net of Deferred Income		$ 269,447
Weighted Average Risk Grade For Loans | Grade		10
Risk Grade Eleven [Member] | Commercial Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	$ 0
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	1,926
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	6,672
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	9,679
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	1,697
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	2,200
Financing Receivable, Revolving	5,958
Loans and Leases Receivable, Net of Deferred Income	$ 34,083	$ 31,518
Weighted Average Risk Grade For Loans | Grade	11	11
Risk Grade Eleven [Member] | Commercial and Industrial Total Energy Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	$ 9,097
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	265
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	512
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	3,256
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	951
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	178
Financing Receivable, Revolving	0
Loans and Leases Receivable, Net of Deferred Income	$ 14,259	$ 16,594
Weighted Average Risk Grade For Loans | Grade	11	11
Risk Grade Eleven [Member] | Commercial Real Estate Buildings Land And Other Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	$ 0
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	260
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	1,293
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	7,328
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	6,788
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	36,699
Financing Receivable, Revolving	3,215
Loans and Leases Receivable, Net of Deferred Income	$ 55,583	$ 91,140
Weighted Average Risk Grade For Loans | Grade	11	11
Risk Grade Eleven [Member] | Construction Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	$ 0
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	0
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	0
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	0
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	0
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	0
Financing Receivable, Revolving	0
Loans and Leases Receivable, Net of Deferred Income	$ 0	$ 0
Weighted Average Risk Grade For Loans | Grade	11	11
Risk Grade Eleven [Member] | Commercial Real Estate Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Net of Deferred Income		$ 91,140
Weighted Average Risk Grade For Loans | Grade		11
Risk Grade Twelve [Member] | Commercial Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	$ 0
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	478
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	2,644
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	3,510
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	1,488
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	619
Financing Receivable, Revolving	941
Loans and Leases Receivable, Net of Deferred Income	$ 11,695	$ 12,535
Weighted Average Risk Grade For Loans | Grade	12	12
Risk Grade Twelve [Member] | Commercial and Industrial Total Energy Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	$ 0
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	0
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	0
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	3,708
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	58
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	0
Financing Receivable, Revolving	3,215
Loans and Leases Receivable, Net of Deferred Income	$ 7,079	$ 8,953
Weighted Average Risk Grade For Loans | Grade	12	12
Risk Grade Twelve [Member] | Commercial Real Estate Buildings Land And Other Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	$ 0
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	8,081
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	296
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	1,199
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	394
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	2,932
Financing Receivable, Revolving	0
Loans and Leases Receivable, Net of Deferred Income	$ 18,677	$ 15,097
Weighted Average Risk Grade For Loans | Grade	12	12
Risk Grade Twelve [Member] | Construction Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	$ 0
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	0
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	583
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	0
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	0
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	0
Financing Receivable, Revolving	0
Loans and Leases Receivable, Net of Deferred Income	$ 583	$ 748
Weighted Average Risk Grade For Loans | Grade	12	12
Risk Grade Twelve [Member] | Commercial Real Estate Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Net of Deferred Income		$ 15,845
Weighted Average Risk Grade For Loans | Grade		12
Risk Grade Thirteen [Member] | Commercial Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	$ 0
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	0
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	1,457
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	400
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	64
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	414
Financing Receivable, Revolving	1,097
Loans and Leases Receivable, Net of Deferred Income	$ 4,998	$ 10,047
Weighted Average Risk Grade For Loans | Grade	13	13
Risk Grade Thirteen [Member] | Commercial and Industrial Total Energy Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	$ 0
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	0
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	0
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	1,331
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	1,079
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	0
Financing Receivable, Revolving	2,782
Loans and Leases Receivable, Net of Deferred Income	$ 5,192	$ 5,480
Weighted Average Risk Grade For Loans | Grade	13	13
Risk Grade Thirteen [Member] | Commercial Real Estate Buildings Land And Other Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	$ 0
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	326
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	0
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	0
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	0
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	0
Financing Receivable, Revolving	0
Loans and Leases Receivable, Net of Deferred Income	$ 326	$ 200
Weighted Average Risk Grade For Loans | Grade	13	13
Risk Grade Thirteen [Member] | Construction Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	$ 0
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	0
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	0
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	0
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	0
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	0
Financing Receivable, Revolving	0
Loans and Leases Receivable, Net of Deferred Income	$ 0	$ 200
Weighted Average Risk Grade For Loans | Grade	13	13
Risk Grade Thirteen [Member] | Commercial Real Estate Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Net of Deferred Income		$ 400
Weighted Average Risk Grade For Loans | Grade		13
Revolving Credit Facility [Member] | Commercial Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade For Loans | Grade	6.14
Revolving Credit Facility [Member] | Commercial and Industrial Total Energy Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade For Loans | Grade	5.41
Revolving Credit Facility [Member] | Commercial Real Estate Buildings Land And Other Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade For Loans | Grade	7.06
Revolving Credit Facility [Member] | Construction Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade For Loans | Grade	6.28
Revolving Credit Facility [Member] | Commercial Real Estate Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade For Loans | Grade	6.50
Revolving Loans Converted to Term [Member] | Commercial Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Revolving, Converted to Term Loan	$ 60,229
Weighted Average Risk Grade For Loans | Grade	7.82
Revolving Loans Converted to Term [Member] | Commercial and Industrial Total Energy Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Revolving, Converted to Term Loan	$ 60,080
Weighted Average Risk Grade For Loans | Grade	6.31
Revolving Loans Converted to Term [Member] | Commercial Real Estate Buildings Land And Other Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Revolving, Converted to Term Loan	$ 105,317
Weighted Average Risk Grade For Loans | Grade	6.99
Revolving Loans Converted to Term [Member] | Construction Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Revolving, Converted to Term Loan	$ 3,666
Weighted Average Risk Grade For Loans | Grade	8
Revolving Loans Converted to Term [Member] | Commercial Real Estate Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Revolving, Converted to Term Loan	$ 108,983
Weighted Average Risk Grade For Loans | Grade	7.03
Revolving Loans Converted to Term [Member] | Risk Grade One To Eight [Member] | Commercial Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Revolving, Converted to Term Loan	$ 44,778
Revolving Loans Converted to Term [Member] | Risk Grade One To Eight [Member] | Commercial and Industrial Total Energy Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Revolving, Converted to Term Loan	59,424
Revolving Loans Converted to Term [Member] | Risk Grade One To Eight [Member] | Commercial Real Estate Buildings Land And Other Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Revolving, Converted to Term Loan	96,924
Revolving Loans Converted to Term [Member] | Risk Grade One To Eight [Member] | Construction Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Revolving, Converted to Term Loan	3,666
Revolving Loans Converted to Term [Member] | Risk Grade Nine [Member] | Commercial Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Revolving, Converted to Term Loan	4,721
Revolving Loans Converted to Term [Member] | Risk Grade Nine [Member] | Commercial and Industrial Total Energy Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Revolving, Converted to Term Loan	43
Revolving Loans Converted to Term [Member] | Risk Grade Nine [Member] | Commercial Real Estate Buildings Land And Other Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Revolving, Converted to Term Loan	2,618
Revolving Loans Converted to Term [Member] | Risk Grade Nine [Member] | Construction Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Revolving, Converted to Term Loan	0
Revolving Loans Converted to Term [Member] | Risk Grade Ten [Member] | Commercial Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Revolving, Converted to Term Loan	1,198
Revolving Loans Converted to Term [Member] | Risk Grade Ten [Member] | Commercial and Industrial Total Energy Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Revolving, Converted to Term Loan	515
Revolving Loans Converted to Term [Member] | Risk Grade Ten [Member] | Commercial Real Estate Buildings Land And Other Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Revolving, Converted to Term Loan	0
Revolving Loans Converted to Term [Member] | Risk Grade Ten [Member] | Construction Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Revolving, Converted to Term Loan	0
Revolving Loans Converted to Term [Member] | Risk Grade Eleven [Member] | Commercial Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Revolving, Converted to Term Loan	5,951
Revolving Loans Converted to Term [Member] | Risk Grade Eleven [Member] | Commercial and Industrial Total Energy Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Revolving, Converted to Term Loan	0
Revolving Loans Converted to Term [Member] | Risk Grade Eleven [Member] | Commercial Real Estate Buildings Land And Other Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Revolving, Converted to Term Loan	0
Revolving Loans Converted to Term [Member] | Risk Grade Eleven [Member] | Construction Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Revolving, Converted to Term Loan	0
Revolving Loans Converted to Term [Member] | Risk Grade Twelve [Member] | Commercial Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Revolving, Converted to Term Loan	2,015
Revolving Loans Converted to Term [Member] | Risk Grade Twelve [Member] | Commercial and Industrial Total Energy Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Revolving, Converted to Term Loan	98
Revolving Loans Converted to Term [Member] | Risk Grade Twelve [Member] | Commercial Real Estate Buildings Land And Other Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Revolving, Converted to Term Loan	5,775
Revolving Loans Converted to Term [Member] | Risk Grade Twelve [Member] | Construction Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Revolving, Converted to Term Loan	0
Revolving Loans Converted to Term [Member] | Risk Grade Thirteen [Member] | Commercial Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Revolving, Converted to Term Loan	1,566
Revolving Loans Converted to Term [Member] | Risk Grade Thirteen [Member] | Commercial and Industrial Total Energy Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Revolving, Converted to Term Loan	0
Revolving Loans Converted to Term [Member] | Risk Grade Thirteen [Member] | Commercial Real Estate Buildings Land And Other Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Revolving, Converted to Term Loan	0
Revolving Loans Converted to Term [Member] | Risk Grade Thirteen [Member] | Construction Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Revolving, Converted to Term Loan	$ 0
2022 [Member] | Commercial Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade For Loans | Grade	6.16
2022 [Member] | Commercial and Industrial Total Energy Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade For Loans | Grade	6.36
2022 [Member] | Commercial Real Estate Buildings Land And Other Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade For Loans | Grade	7.08
2022 [Member] | Construction Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade For Loans | Grade	6.83
2022 [Member] | Commercial Real Estate Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade For Loans | Grade	7.02
2021 [Member] | Commercial Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade For Loans | Grade	6.87
2021 [Member] | Commercial and Industrial Total Energy Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade For Loans | Grade	5.77
2021 [Member] | Commercial Real Estate Buildings Land And Other Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade For Loans | Grade	7.22
2021 [Member] | Construction Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade For Loans | Grade	7.28
2021 [Member] | Commercial Real Estate Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade For Loans | Grade	7.24
2020 [Member] | Commercial Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade For Loans | Grade	6.17
2020 [Member] | Commercial and Industrial Total Energy Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade For Loans | Grade	7.73
2020 [Member] | Commercial Real Estate Buildings Land And Other Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade For Loans | Grade	7.04
2020 [Member] | Construction Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade For Loans | Grade	6.38
2020 [Member] | Commercial Real Estate Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade For Loans | Grade	6.95
2019 [Member] | Commercial Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade For Loans | Grade	6.75
2019 [Member] | Commercial and Industrial Total Energy Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade For Loans | Grade	9.34
2019 [Member] | Commercial Real Estate Buildings Land And Other Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade For Loans | Grade	7.32
2019 [Member] | Construction Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade For Loans | Grade	7.98
2019 [Member] | Commercial Real Estate Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade For Loans | Grade	7.41
2018 [Member] | Commercial Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade For Loans | Grade	7
2018 [Member] | Commercial and Industrial Total Energy Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade For Loans | Grade	9.24
2018 [Member] | Commercial Real Estate Buildings Land And Other Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade For Loans | Grade	7.27
2018 [Member] | Construction Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade For Loans | Grade	6.22
2018 [Member] | Commercial Real Estate Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade For Loans | Grade	7.27
Prior Years [Member] | Commercial Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade For Loans | Grade	5.80
Prior Years [Member] | Commercial and Industrial Total Energy Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade For Loans | Grade	7.16
Prior Years [Member] | Commercial Real Estate Buildings Land And Other Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade For Loans | Grade	6.97
Prior Years [Member] | Construction Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade For Loans | Grade	7.17
Prior Years [Member] | Commercial Real Estate Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade For Loans | Grade	6.97

Loans - Weighted Average Risk G

Loans - Weighted Average Risk Grades for All Commercial Loans by Class (Detail) $ in Thousands	Mar. 31, 2022USD ($)Grade	Dec. 31, 2021USD ($)Grade
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Net of Deferred Income	$ 16,542,537	$ 16,336,397
Commercial Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade | Grade	6.34	6.22
Loans and Leases Receivable, Net of Deferred Income	$ 5,584,117	$ 5,364,954
Commercial and Industrial Total Energy Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade | Grade	5.89	6.06
Loans and Leases Receivable, Net of Deferred Income	$ 1,036,579	$ 1,077,792
Commercial Real Estate Buildings Land And Other Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade | Grade	7.14	7.22
Loans and Leases Receivable, Net of Deferred Income	$ 6,376,521	$ 6,272,339
Construction Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade | Grade	7.01	7.06
Loans and Leases Receivable, Net of Deferred Income	$ 1,421,878	$ 1,304,271
Commercial Real Estate Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade | Grade	7.11	7.19
Loans and Leases Receivable, Net of Deferred Income	$ 7,798,399	$ 7,576,610
Risk Grade One To Eight [Member] | Commercial Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade | Grade	6.18	6.01
Loans and Leases Receivable, Net of Deferred Income	$ 5,334,409	$ 5,063,847
Risk Grade One To Eight [Member] | Commercial and Industrial Total Energy Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade | Grade	5.71	5.78
Loans and Leases Receivable, Net of Deferred Income	$ 999,263	$ 1,008,370
Risk Grade One To Eight [Member] | Commercial Real Estate Buildings Land And Other Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade | Grade	6.89	6.91
Loans and Leases Receivable, Net of Deferred Income	$ 5,810,875	$ 5,574,922
Risk Grade One To Eight [Member] | Construction Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade | Grade	6.96	6.99
Loans and Leases Receivable, Net of Deferred Income	$ 1,387,273	$ 1,262,200
Risk Grade One To Eight [Member] | Commercial Real Estate Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade | Grade		6.92
Loans and Leases Receivable, Net of Deferred Income		$ 6,837,122
Risk Grade Nine [Member] | Commercial Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade | Grade	9	9
Loans and Leases Receivable, Net of Deferred Income	$ 146,100	$ 187,870
Risk Grade Nine [Member] | Commercial and Industrial Total Energy Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade | Grade	9	9
Loans and Leases Receivable, Net of Deferred Income	$ 9,250	$ 36,622
Risk Grade Nine [Member] | Commercial Real Estate Buildings Land And Other Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade | Grade	9	9
Loans and Leases Receivable, Net of Deferred Income	$ 265,947	$ 321,533
Risk Grade Nine [Member] | Construction Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade | Grade	9	9
Loans and Leases Receivable, Net of Deferred Income	$ 34,022	$ 41,123
Risk Grade Nine [Member] | Commercial Real Estate Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade | Grade		9
Loans and Leases Receivable, Net of Deferred Income		$ 362,656
Risk Grade Ten [Member] | Commercial Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade | Grade	10	10
Loans and Leases Receivable, Net of Deferred Income	$ 52,832	$ 59,137
Risk Grade Ten [Member] | Commercial and Industrial Total Energy Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade | Grade	10	10
Loans and Leases Receivable, Net of Deferred Income	$ 1,536	$ 1,773
Risk Grade Ten [Member] | Commercial Real Estate Buildings Land And Other Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade | Grade	10	10
Loans and Leases Receivable, Net of Deferred Income	$ 225,113	$ 269,447
Risk Grade Ten [Member] | Construction Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade | Grade	10	10
Loans and Leases Receivable, Net of Deferred Income	$ 0	$ 0
Risk Grade Ten [Member] | Commercial Real Estate Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade | Grade		10
Loans and Leases Receivable, Net of Deferred Income		$ 269,447
Risk Grade Eleven [Member] | Commercial Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade | Grade	11	11
Loans and Leases Receivable, Net of Deferred Income	$ 34,083	$ 31,518
Risk Grade Eleven [Member] | Commercial and Industrial Total Energy Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade | Grade	11	11
Loans and Leases Receivable, Net of Deferred Income	$ 14,259	$ 16,594
Risk Grade Eleven [Member] | Commercial Real Estate Buildings Land And Other Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade | Grade	11	11
Loans and Leases Receivable, Net of Deferred Income	$ 55,583	$ 91,140
Risk Grade Eleven [Member] | Construction Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade | Grade	11	11
Loans and Leases Receivable, Net of Deferred Income	$ 0	$ 0
Risk Grade Eleven [Member] | Commercial Real Estate Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade | Grade		11
Loans and Leases Receivable, Net of Deferred Income		$ 91,140
Risk Grade Twelve [Member] | Commercial Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade | Grade	12	12
Loans and Leases Receivable, Net of Deferred Income	$ 11,695	$ 12,535
Risk Grade Twelve [Member] | Commercial and Industrial Total Energy Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade | Grade	12	12
Loans and Leases Receivable, Net of Deferred Income	$ 7,079	$ 8,953
Risk Grade Twelve [Member] | Commercial Real Estate Buildings Land And Other Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade | Grade	12	12
Loans and Leases Receivable, Net of Deferred Income	$ 18,677	$ 15,097
Risk Grade Twelve [Member] | Construction Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade | Grade	12	12
Loans and Leases Receivable, Net of Deferred Income	$ 583	$ 748
Risk Grade Twelve [Member] | Commercial Real Estate Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade | Grade		12
Loans and Leases Receivable, Net of Deferred Income		$ 15,845
Risk Grade Thirteen [Member] | Commercial Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade | Grade	13	13
Loans and Leases Receivable, Net of Deferred Income	$ 4,998	$ 10,047
Risk Grade Thirteen [Member] | Commercial and Industrial Total Energy Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade | Grade	13	13
Loans and Leases Receivable, Net of Deferred Income	$ 5,192	$ 5,480
Risk Grade Thirteen [Member] | Commercial Real Estate Buildings Land And Other Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade | Grade	13	13
Loans and Leases Receivable, Net of Deferred Income	$ 326	$ 200
Risk Grade Thirteen [Member] | Construction Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade | Grade	13	13
Loans and Leases Receivable, Net of Deferred Income	$ 0	$ 200
Risk Grade Thirteen [Member] | Commercial Real Estate Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade | Grade		13
Loans and Leases Receivable, Net of Deferred Income		$ 400

Loans Loans - Age Analysis of P

Loans Loans - Age Analysis of Past Due Consumer Loans,Segregated by Class and Year of Origination (Details) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Net of Deferred Income	$ 16,542,537	$ 16,336,397
Total consumer real estate loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Net of Deferred Income	1,433,625	1,410,790
Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Net of Deferred Income	482,148	$ 477,369
Financing Receivables, 30 to 89 Days Past Due [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	47,820
Financing Receivables, 30 to 89 Days Past Due [Member] | Total consumer real estate loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	4,210
Financing Receivables, 30 to 89 Days Past Due [Member] | Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	6,393
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	37,349
Financial Asset, Equal to or Greater than 90 Days Past Due [Member] | Total consumer real estate loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	2,409
Financial Asset, Equal to or Greater than 90 Days Past Due [Member] | Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	593
Financial Asset, Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	85,169
Financial Asset, Past Due | Total consumer real estate loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	6,619
Financial Asset, Past Due | Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	6,986
Financial Asset, Not Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	16,457,368
Financial Asset, Not Past Due | Total consumer real estate loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	1,427,006
Financial Asset, Not Past Due | Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	475,162
Revolving Credit Facility [Member] | Total consumer real estate loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Net of Deferred Income	534,246
Revolving Credit Facility [Member] | Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Net of Deferred Income	373,610
Revolving Credit Facility [Member] | Financing Receivables, 30 to 89 Days Past Due [Member] | Total consumer real estate loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	60
Revolving Credit Facility [Member] | Financing Receivables, 30 to 89 Days Past Due [Member] | Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	2,344
Revolving Credit Facility [Member] | Financial Asset, Equal to or Greater than 90 Days Past Due [Member] | Total consumer real estate loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	1,004
Revolving Credit Facility [Member] | Financial Asset, Equal to or Greater than 90 Days Past Due [Member] | Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	0
Revolving Credit Facility [Member] | Financial Asset, Past Due | Total consumer real estate loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	1,064
Revolving Credit Facility [Member] | Financial Asset, Past Due | Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	2,344
Revolving Credit Facility [Member] | Financial Asset, Not Past Due | Total consumer real estate loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	533,182
Revolving Credit Facility [Member] | Financial Asset, Not Past Due | Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	371,266
Revolving Loans Converted to Term [Member] | Total consumer real estate loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Net of Deferred Income	10,627
Revolving Loans Converted to Term [Member] | Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Net of Deferred Income	26,668
Revolving Loans Converted to Term [Member] | Financing Receivables, 30 to 89 Days Past Due [Member] | Total consumer real estate loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	1,431
Revolving Loans Converted to Term [Member] | Financing Receivables, 30 to 89 Days Past Due [Member] | Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	1,994
Revolving Loans Converted to Term [Member] | Financial Asset, Equal to or Greater than 90 Days Past Due [Member] | Total consumer real estate loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	250
Revolving Loans Converted to Term [Member] | Financial Asset, Equal to or Greater than 90 Days Past Due [Member] | Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	58
Revolving Loans Converted to Term [Member] | Financial Asset, Past Due | Total consumer real estate loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	1,681
Revolving Loans Converted to Term [Member] | Financial Asset, Past Due | Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	2,052
Revolving Loans Converted to Term [Member] | Financial Asset, Not Past Due | Total consumer real estate loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	8,946
Revolving Loans Converted to Term [Member] | Financial Asset, Not Past Due | Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	24,616
2022 [Member] | Total consumer real estate loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Net of Deferred Income	51,321
2022 [Member] | Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Net of Deferred Income	23,162
2022 [Member] | Financing Receivables, 30 to 89 Days Past Due [Member] | Total consumer real estate loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	0
2022 [Member] | Financing Receivables, 30 to 89 Days Past Due [Member] | Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	1,470
2022 [Member] | Financial Asset, Equal to or Greater than 90 Days Past Due [Member] | Total consumer real estate loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	0
2022 [Member] | Financial Asset, Equal to or Greater than 90 Days Past Due [Member] | Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	0
2022 [Member] | Financial Asset, Past Due | Total consumer real estate loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	0
2022 [Member] | Financial Asset, Past Due | Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	1,470
2022 [Member] | Financial Asset, Not Past Due | Total consumer real estate loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	51,321
2022 [Member] | Financial Asset, Not Past Due | Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	21,692
2021 [Member] | Total consumer real estate loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Net of Deferred Income	323,117
2021 [Member] | Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Net of Deferred Income	35,682
2021 [Member] | Financing Receivables, 30 to 89 Days Past Due [Member] | Total consumer real estate loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	303
2021 [Member] | Financing Receivables, 30 to 89 Days Past Due [Member] | Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	385
2021 [Member] | Financial Asset, Equal to or Greater than 90 Days Past Due [Member] | Total consumer real estate loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	0
2021 [Member] | Financial Asset, Equal to or Greater than 90 Days Past Due [Member] | Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	499
2021 [Member] | Financial Asset, Past Due | Total consumer real estate loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	303
2021 [Member] | Financial Asset, Past Due | Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	884
2021 [Member] | Financial Asset, Not Past Due | Total consumer real estate loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	322,814
2021 [Member] | Financial Asset, Not Past Due | Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	34,798
2020 [Member] | Total consumer real estate loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Net of Deferred Income	225,980
2020 [Member] | Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Net of Deferred Income	13,180
2020 [Member] | Financing Receivables, 30 to 89 Days Past Due [Member] | Total consumer real estate loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	55
2020 [Member] | Financing Receivables, 30 to 89 Days Past Due [Member] | Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	53
2020 [Member] | Financial Asset, Equal to or Greater than 90 Days Past Due [Member] | Total consumer real estate loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	4
2020 [Member] | Financial Asset, Equal to or Greater than 90 Days Past Due [Member] | Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	0
2020 [Member] | Financial Asset, Past Due | Total consumer real estate loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	59
2020 [Member] | Financial Asset, Past Due | Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	53
2020 [Member] | Financial Asset, Not Past Due | Total consumer real estate loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	225,921
2020 [Member] | Financial Asset, Not Past Due | Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	13,127
2019 [Member] | Total consumer real estate loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Net of Deferred Income	87,129
2019 [Member] | Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Net of Deferred Income	5,028
2019 [Member] | Financing Receivables, 30 to 89 Days Past Due [Member] | Total consumer real estate loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	465
2019 [Member] | Financing Receivables, 30 to 89 Days Past Due [Member] | Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	69
2019 [Member] | Financial Asset, Equal to or Greater than 90 Days Past Due [Member] | Total consumer real estate loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	0
2019 [Member] | Financial Asset, Equal to or Greater than 90 Days Past Due [Member] | Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	23
2019 [Member] | Financial Asset, Past Due | Total consumer real estate loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	465
2019 [Member] | Financial Asset, Past Due | Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	92
2019 [Member] | Financial Asset, Not Past Due | Total consumer real estate loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	86,664
2019 [Member] | Financial Asset, Not Past Due | Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	4,936
2018 [Member] | Total consumer real estate loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Net of Deferred Income	49,087
2018 [Member] | Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Net of Deferred Income	2,261
2018 [Member] | Financing Receivables, 30 to 89 Days Past Due [Member] | Total consumer real estate loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	309
2018 [Member] | Financing Receivables, 30 to 89 Days Past Due [Member] | Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	54
2018 [Member] | Financial Asset, Equal to or Greater than 90 Days Past Due [Member] | Total consumer real estate loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	297
2018 [Member] | Financial Asset, Equal to or Greater than 90 Days Past Due [Member] | Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	0
2018 [Member] | Financial Asset, Past Due | Total consumer real estate loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	606
2018 [Member] | Financial Asset, Past Due | Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	54
2018 [Member] | Financial Asset, Not Past Due | Total consumer real estate loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	48,481
2018 [Member] | Financial Asset, Not Past Due | Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	2,207
Prior Years [Member] | Total consumer real estate loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Net of Deferred Income	152,118
Prior Years [Member] | Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Net of Deferred Income	2,557
Prior Years [Member] | Financing Receivables, 30 to 89 Days Past Due [Member] | Total consumer real estate loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	1,587
Prior Years [Member] | Financing Receivables, 30 to 89 Days Past Due [Member] | Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	24
Prior Years [Member] | Financial Asset, Equal to or Greater than 90 Days Past Due [Member] | Total consumer real estate loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	854
Prior Years [Member] | Financial Asset, Equal to or Greater than 90 Days Past Due [Member] | Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	13
Prior Years [Member] | Financial Asset, Past Due | Total consumer real estate loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	2,441
Prior Years [Member] | Financial Asset, Past Due | Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	37
Prior Years [Member] | Financial Asset, Not Past Due | Total consumer real estate loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	149,677
Prior Years [Member] | Financial Asset, Not Past Due | Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	$ 2,520

Loans Loans - Revolving Loans C

Loans Loans - Revolving Loans Converted to Term (Details) - Revolving Loans Converted to Term [Member] - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Accounts, Notes, Loans and Financing Receivable [Line Items]
Remaining Revolving Loans Converted to Term During Period	$ 14,556	$ 45,728
Commercial Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Remaining Revolving Loans Converted to Term During Period	5,763	11,843
Commercial and Industrial Total Energy Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Remaining Revolving Loans Converted to Term During Period	0	5,928
Commercial Real Estate Buildings Land And Other Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Remaining Revolving Loans Converted to Term During Period	47	23,303
Construction Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Remaining Revolving Loans Converted to Term During Period	3,666	0
Total consumer real estate loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Remaining Revolving Loans Converted to Term During Period	858	793
Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Remaining Revolving Loans Converted to Term During Period	$ 4,222	$ 3,861

Loans Loans - Allowance for C_2

Loans Loans - Allowance for Credit Loss By Loan Class Calculated in Accordance With CECL Methodology (Details) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021	Mar. 31, 2021	Dec. 31, 2020
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, Allowance for Credit Loss	$ 246,835	$ 248,666
Commercial Portfolio Segment [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, Allowance for Credit Loss	87,026	72,091	$ 70,892	$ 73,843
Commercial and Industrial Total Energy Loans [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, Allowance for Credit Loss	15,422	17,217	33,472	39,553
Commercial Real Estate Portfolio Segment [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, Allowance for Credit Loss	128,954	144,936	144,440	134,892
Total consumer real estate loans [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, Allowance for Credit Loss	6,359	6,585	5,636	7,926
Consumer Loan [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, Allowance for Credit Loss	9,074	7,837	6,818	6,963
Loans Receivable [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, Allowance for Credit Loss	246,835	248,666	$ 261,258	$ 263,177
Modeled Expected Credit Losses [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, Allowance for Credit Loss	83,610	82,866
Modeled Expected Credit Losses [Member] | Commercial Portfolio Segment [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, Allowance for Credit Loss	46,635	46,946
Modeled Expected Credit Losses [Member] | Commercial and Industrial Total Energy Loans [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, Allowance for Credit Loss	5,971	6,363
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	17,110	16,676
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	6,260	6,484
Modeled Expected Credit Losses [Member] | Consumer Loan [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, Allowance for Credit Loss	7,634	6,397
Q-factor adjustments [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, Allowance for Credit Loss	151,197	149,348
Q-factor adjustments [Member] | Commercial Portfolio Segment [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, Allowance for Credit Loss	33,916	14,609
Q-factor adjustments [Member] | Commercial and Industrial Total Energy Loans [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, Allowance for Credit Loss	4,260	5,374
Q-factor adjustments [Member] | Commercial Real Estate Portfolio Segment [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, Allowance for Credit Loss	111,518	127,860
Q-factor adjustments [Member] | Total consumer real estate loans [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, Allowance for Credit Loss	63	65
Q-factor adjustments [Member] | Consumer Loan [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, Allowance for Credit Loss	1,440	1,440
Specific Valuation Allowances [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, Allowance for Credit Loss	12,028	16,452
Specific Valuation Allowances [Member] | Commercial Portfolio Segment [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, Allowance for Credit Loss	6,475	10,536
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	5,191	5,480
Specific Valuation Allowances [Member] | Commercial Real Estate Portfolio Segment [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, Allowance for Credit Loss	326	400
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	36
Specific Valuation Allowances [Member] | Consumer Loan [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, Allowance for Credit Loss	$ 0	$ 0

Loans - Activity in the Allowan

Loans - Activity in the Allowance for Credit Losses on Loans by Portfolio Segment (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning balance	$ 248,666
Ending balance	246,835
Commercial Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning balance	72,091	$ 73,843
Credit loss, expense (reversal)	17,561	(1,965)
Charge-offs	(3,455)	(2,189)
Recoveries	829	1,203
Net charge-offs	(2,626)	(986)
Ending balance	87,026	70,892
Commercial and Industrial Total Energy Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning balance	17,217	39,553
Credit loss, expense (reversal)	(2,044)	(5,801)
Charge-offs	(371)	(1,433)
Recoveries	620	1,153
Net charge-offs	249	(280)
Ending balance	15,422	33,472
Commercial Real Estate Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning balance	144,936	134,892
Credit loss, expense (reversal)	(15,609)	8,922
Charge-offs	(702)	0
Recoveries	329	626
Net charge-offs	(373)	626
Ending balance	128,954	144,440
Total consumer real estate loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning balance	6,585	7,926
Credit loss, expense (reversal)	(26)	(2,722)
Charge-offs	(231)	(284)
Recoveries	31	716
Net charge-offs	(200)	432
Ending balance	6,359	5,636
Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning balance	7,837	6,963
Credit loss, expense (reversal)	4,582	1,566
Charge-offs	(5,771)	(4,060)
Recoveries	2,426	2,349
Net charge-offs	(3,345)	(1,711)
Ending balance	9,074	6,818
Loans Receivable [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning balance	248,666	263,177
Credit loss, expense (reversal)	4,464	0
Charge-offs	(10,530)	(7,966)
Recoveries	4,235	6,047
Net charge-offs	(6,295)	(1,919)
Ending balance	$ 246,835	$ 261,258

Loans - Investment in Loans Rel

Loans - Investment in Loans Related to Allowance for Loan Losses by Portfolio Segment Disaggregated Based on Impairment Methodology (Detail) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Net of Deferred Income	$ 16,542,537	$ 16,336,397
Commercial Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Net of Deferred Income	5,584,117	5,364,954
Commercial and Industrial Total Energy Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Net of Deferred Income	1,036,579	1,077,792
Paycheck Protection Program [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Net of Deferred Income	207,669	428,882
Commercial Real Estate Buildings Land And Other Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Net of Deferred Income	6,376,521	6,272,339
Construction Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Net of Deferred Income	1,421,878	1,304,271
Total consumer real estate loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Net of Deferred Income	1,433,625	1,410,790
Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Net of Deferred Income	482,148	477,369
Specific Valuation Allowances [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Specific Allocations	12,028	16,452
Specific Valuation Allowances [Member] | Commercial Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Specific Allocations	6,475	10,536
Specific Valuation Allowances [Member] | Commercial and Industrial Total Energy Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Specific Allocations	5,191	5,480
Specific Valuation Allowances [Member] | Paycheck Protection Program [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Specific Allocations	0	0
Specific Valuation Allowances [Member] | Commercial Real Estate Buildings Land And Other Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Specific Allocations	326	200
Specific Valuation Allowances [Member] | Construction Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Specific Allocations	0	200
Specific Valuation Allowances [Member] | Total consumer real estate loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Specific Allocations	36	36
Specific Valuation Allowances [Member] | Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Specific Allocations	0	0
Loans Individually Evaluated for Impairment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Net of Deferred Income	62,568	66,837
Loans Individually Evaluated for Impairment [Member] | Commercial Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Net of Deferred Income	21,529	24,523
Loans Individually Evaluated for Impairment [Member] | Commercial and Industrial Total Energy Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Net of Deferred Income	11,931	16,393
Loans Individually Evaluated for Impairment [Member] | Paycheck Protection Program [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Net of Deferred Income	0	0
Loans Individually Evaluated for Impairment [Member] | Commercial Real Estate Buildings Land And Other Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Net of Deferred Income	28,806	24,670
Loans Individually Evaluated for Impairment [Member] | Construction Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Net of Deferred Income	0	948
Loans Individually Evaluated for Impairment [Member] | Total consumer real estate loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Net of Deferred Income	302	303
Loans Individually Evaluated for Impairment [Member] | Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Net of Deferred Income	$ 0	$ 0

Goodwill and Other Intangible_3

Goodwill and Other Intangible Assets - Schedule of Goodwill (Detail) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill	$ 654,952	$ 654,952

Goodwill and Other Intangible_4

Goodwill and Other Intangible Assets - Schedule of Other Intangible Assets (Detail) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Finite-Lived Intangible Assets [Line Items]
Other intangible assets, net	$ 720	$ 866
Core deposits [Member]
Finite-Lived Intangible Assets [Line Items]
Other intangible assets, net	591	718
Customer relationships [Member]
Finite-Lived Intangible Assets [Line Items]
Other intangible assets, net	$ 129	$ 148

Goodwill and Other Intangible_5

Goodwill and Other Intangible Assets - Estimated Aggregate Future Amortization Expense for Intangible Assets (Detail) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Goodwill and Intangible Assets Disclosure [Abstract]
Remainder of 2022	$ 335
2023	282
2024	87
2025	11
2026	5
Thereafter	0
Future Amortization Expense, Total	$ 720	$ 866

Deposits - Schedule of Deposits

Deposits - Schedule of Deposits (Detail) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Deposit [Line Items]
Non-interest-bearing demand deposits	$ 18,114,430	$ 18,423,018
Interest-bearing Domestic Deposit, Savings	12,484,308	11,930,959
Interest-bearing Domestic Deposit, Money Market	12,490,612	11,228,815
Interest-bearing Domestic Deposit, Time Deposits	1,341,579	1,112,904
Interest-bearing deposits	26,316,499	24,272,678
Deposits	$ 44,430,929	$ 42,695,696

Deposits - Additional Informati

Deposits - Additional Information About Corporation's Deposits (Detail) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Deposit Liability [Line Items]
Deposits from foreign sources (primarily Mexico)	$ 1,092,302	$ 993,479
Non-interest-bearing demand deposits	18,114,430	18,423,018
Interest-bearing deposits	26,316,499	24,272,678
Total deposits not covered by deposit insurance	25,213,248	24,125,359
Time deposits not covered by deposit insurance	357,529	238,608
Public Funds [Member]
Deposit Liability [Line Items]
Non-interest-bearing demand deposits	746,097	1,235,026
Interest-bearing deposits	$ 975,511	$ 810,863

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021	Dec. 31, 2021
Lessee, Operating Lease, Liability, Payments, Due	$ 8,000	$ 8,100
Significant change in expected future minimum lease payments since year end	0
Premises and Equipment
Operating Lease, Right-of-Use Asset	279,500		$ 281,400
Other Liabilities [Member]
Operating Lease, Liability	$ 311,800		$ 313,400

Commitments and Contingencies_2

Commitments and Contingencies - Financial Instruments with Off-Balance-Sheet Risk (Detail) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Standby Letters of Credit [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Financial instruments with off- balance-sheet risk	$ 236,798	$ 238,690
Deferred Standby Letter Of Credit Fees [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Financial instruments with off- balance-sheet risk	1,704	2,072
Commitments to Extend Credit [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Financial instruments with off- balance-sheet risk	$ 10,356,196	$ 10,420,142

Commitments and Contingencies C

Commitments and Contingencies Commitments and Contingencies - Credit Losses on Off-Balance-Sheet Commitments (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Commitments and Contingencies Disclosure [Abstract]
Off-Balance Sheet, Credit Loss, Liability	$ 50,314	$ 44,152
Credit loss expense (benefit)	(4,464)	65
Off-Balance Sheet, Credit Loss, Liability	$ 45,850	$ 44,217

Commitments and Contingencies_3

Commitments and Contingencies Commitments and Contingencies - Components of Lease Commitments Expense (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Commitments and Contingencies Disclosure [Abstract]
Operating Lease, Right-of-Use Asset, Amortization Expense	$ 8,105	$ 8,283
Short-term lease expense	613	204
Non-lease components (including taxes, insurance, common maintenance, etc.)	3,020	3,004
Total operating lease expense, excluding rent	$ 11,738	$ 11,491

Capital and Regulatory Matter_2

Capital and Regulatory Matters - Additional Information (Detail)	Jan. 26, 2022USD ($)	Nov. 19, 2020USD ($)	Mar. 31, 2022USD ($)quarter$ / sharesshares	Mar. 31, 2021shares	Dec. 31, 2021USD ($)$ / sharesshares
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
CECL Transition Amount			$ 46,200,000		$ 61,600,000
Preferred Stock, Aggregate Liquidation Preference, Value			$ 150,000,000
Treasury Stock, Shares, Acquired | shares			7,459	11,625
Maximum dividends available without prior regulatory approval			$ 325,000,000
Maximum number of quarterly periods by which the corporation has the right to defer interest payments on junior subordinated deferrable interest debentures | quarter			20
Series B Preferred Stock [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Preferred stock dividend rate percentage		4.45%
Preferred stock, shares issued | shares			150,000		150,000
Preferred Stock, Aggregate Liquidation Preference, Value			$ 1,000		$ 1,000
Preferred stock, par value | $ / shares			$ 0.01		$ 0.01
Preferred Stock, 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 and Preference Stock		$ 145,500,000
Series B Preferred Stock Equivalent Depositary Shares Member
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Preferred Stock, Liquidation Preference Per Share | $ / shares			$ 25
Cullen/Frost [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Additional Tier 1 Capital beyond Common Equity Tier 1			$ 145,500,000		$ 145,500,000
Preferred stock dividend rate percentage			4.45%		4.45%
Cullen/Frost [Member] | Trust Preferred Securities Tier Two Capital Allowable Portion [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Trust preferred securities			$ 120,000,000		$ 120,000,000
Frost Bank [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Additional Tier 1 Capital beyond Common Equity Tier 1			$ 0		0
stock repurchase 2022 plan
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Stock Repurchase Program, Authorized Amount	$ 100,000,000
Stock Repurchase Program, Period in Force	1 year
stock repurchase 2022 plan | Treasury Stock [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Treasury Stock, Shares, Acquired | shares			0
Subordinated Debt [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Permissible Percentage Decreased Each Of Final Five Years Of Term Of Notes			20.00%
Final years of the term of the notes			5 years
Subordinated Debt [Member] | Cullen/Frost [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Permissible portion of subordinated note included in capital			$ 80,000,000		$ 100,000,000

Capital and Regulatory Matter_3

Capital and Regulatory Matters - Actual and Required Capital Ratios (Detail) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Cullen/Frost [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Common Equity Tier 1 to Risk-Weighted Assets, Actual, Capital Amount	$ 3,412,080	$ 3,371,043
Common Equity Tier 1 to Risk-Weighted Assets, Actual , Ratio	12.78%	13.13%
Common Equity Tier 1 to Risk-Weighted Assets, Minimum Capital Required - Basel III Fully Phased-In, Capital Amount	$ 1,869,007	$ 1,796,549
Common Equity Tier 1 to Risk-Weighted Assets, Minimum Capital Required - Basel III Fully Phased In, Ratio	7.00%	7.00%
Common Equity Tier 1 to Risk-Weighted Assets, Required To Be Considered Well Capitalized, Capital Amount	$ 1,735,506	$ 1,668,224
Common Equity Tier 1 to Risk-Weighted Assets, Required To Be Considered Well Capitalized, Ratio	6.50%	6.50%
Tier 1 Capital to Risk-Weighted Assets, Actual, Capital Amount	$ 3,557,532	$ 3,516,495
Tier 1 Capital to Risk-Weighted Assets, Actual, Ratio	13.32%	13.70%
Tier 1 Capital to Risk-Weighted Assets, Minimum Capital Required - Basel III Fully Phased-In, Capital Amount	$ 2,269,508	$ 2,181,523
Tier 1 Capital to Risk-Weighted Assets, Minimum Capital Required - Basel III Fully Phased-In, Ratio	8.50%	8.50%
Tier 1 Capital to Risk-Weighted Assets, Required to be Considered Well Capitalized, Capital Amount	$ 2,136,007	$ 2,053,198
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	$ 3,998,333	$ 3,966,244
Total Capital to Risk-Weighted Assets, Actual, Ratio	14.97%	15.45%
Total Capital to Risk-Weighted Assets, Minimum Capital Required - Basel III Fully Phased-In, Capital Amount	$ 2,803,510	$ 2,694,823
Total Capital to Risk-Weighted Assets, Minimum Capital Required - Basel III Fully Phased-In, Ratio	10.50%	10.50%
Total Capital to Risk-Weighted Assets, Required to be Considered Well Capitalized, Capital Amount	$ 2,670,009	$ 2,566,498
Total Capital to Risk-Weighted Assets, Required to be Considered Well Capitalized, Ratio	10.00%	10.00%
Leverage Ratio, Actual, Capital Amount	$ 3,557,532	$ 3,516,495
Leverage Ratio, Actual, Ratio	7.08%	7.34%
Leverage Ratio, Minimum Capital Required - Basel III Fully Phased-In, Capital Amount	$ 2,010,897	$ 1,917,533
Leverage Ratio, Minimum Capital Required - Basel III Fully Phased-In, Ratio	4.00%	4.00%
Leverage Ratio, Required to be Considered Well Capitalized, Capital Amount	$ 2,513,621	$ 2,396,917
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 1 to Risk-Weighted Assets, Actual, Capital Amount	$ 3,301,515	$ 3,261,532
Common Equity Tier 1 to Risk-Weighted Assets, Actual , Ratio	12.39%	12.72%
Common Equity Tier 1 to Risk-Weighted Assets, Minimum Capital Required - Basel III Fully Phased-In, Capital Amount	$ 1,865,304	$ 1,795,221
Common Equity Tier 1 to Risk-Weighted Assets, Minimum Capital Required - Basel III Fully Phased In, Ratio	7.00%	7.00%
Common Equity Tier 1 to Risk-Weighted Assets, Required To Be Considered Well Capitalized, Capital Amount	$ 1,732,068	$ 1,666,991
Common Equity Tier 1 to Risk-Weighted Assets, Required To Be Considered Well Capitalized, Ratio	6.50%	6.50%
Tier 1 Capital to Risk-Weighted Assets, Actual, Capital Amount	$ 3,301,515	$ 3,261,532
Tier 1 Capital to Risk-Weighted Assets, Actual, Ratio	12.39%	12.72%
Tier 1 Capital to Risk-Weighted Assets, Minimum Capital Required - Basel III Fully Phased-In, Capital Amount	$ 2,265,012	$ 2,179,911
Tier 1 Capital to Risk-Weighted Assets, Minimum Capital Required - Basel III Fully Phased-In, Ratio	8.50%	8.50%
Tier 1 Capital to Risk-Weighted Assets, Required to be Considered Well Capitalized, Capital Amount	$ 2,131,776	$ 2,051,681
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	$ 3,542,316	$ 3,491,281
Total Capital to Risk-Weighted Assets, Actual, Ratio	13.29%	13.61%
Total Capital to Risk-Weighted Assets, Minimum Capital Required - Basel III Fully Phased-In, Capital Amount	$ 2,797,956	$ 2,692,831
Total Capital to Risk-Weighted Assets, Minimum Capital Required - Basel III Fully Phased-In, Ratio	10.50%	10.50%
Total Capital to Risk-Weighted Assets, Required to be Considered Well Capitalized, Capital Amount	$ 2,664,720	$ 2,564,601
Total Capital to Risk-Weighted Assets, Required to be Considered Well Capitalized, Ratio	10.00%	10.00%
Leverage Ratio, Actual, Capital Amount	$ 3,301,515	$ 3,261,532
Leverage Ratio, Actual, Ratio	6.57%	6.80%
Leverage Ratio, Minimum Capital Required - Basel III Fully Phased-In, Capital Amount	$ 2,009,767	$ 1,917,679
Leverage Ratio, Minimum Capital Required - Basel III Fully Phased-In, Ratio	4.00%	4.00%
Leverage Ratio, Required to be Considered Well Capitalized, Capital Amount	$ 2,512,209	$ 2,397,099
Leverage Ratio, Required to be Considered Well Capitalized, Ratio	5.00%	5.00%

Derivative Financial Instrume_3

Derivative Financial Instruments - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Dec. 31, 2021
Derivative [Line Items]
Weighted-average strike rate for outstanding interest rate caps	3.27%
Approximate credit exposure related to swaps with bank customers	$ 238,400
Cash collateral for borrowed securities deposited with other financial institutions	247,300
Interest rate swaps with upstream financial institution counterparties [Member]
Derivative [Line Items]
Approximate credit exposure related to swaps with bank customers	35,700
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

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	Mar. 31, 2022	Dec. 31, 2021
Designated as Hedging Instrument [Member] | Financial institution counterparties Loan/lease interest rate swaps assets [Member]
Derivatives, Fair Value [Line Items]
Forward Contracts – Assets Notional Amount	$ 1,807	$ 0
Estimated Fair Value	1	0
Designated as Hedging Instrument [Member] | Financial institution counterparties Loan/lease interest rate swaps liabilities [Member]
Derivatives, Fair Value [Line Items]
Forward Contracts – Liability Notional Amount	280	2,426
Estimated Fair Value	(3)	(34)
Non Designated as Hedging Instrument [Member] | Financial institution counterparties Loan/lease interest rate swaps assets [Member]
Derivatives, Fair Value [Line Items]
Forward Contracts – Assets Notional Amount	697,834	247,592
Estimated Fair Value	15,311	1,207
Non Designated as Hedging Instrument [Member] | Financial institution counterparties Loan/lease interest rate swaps liabilities [Member]
Derivatives, Fair Value [Line Items]
Forward Contracts – Liability Notional Amount	447,742	928,756
Estimated Fair Value	(6,184)	(19,142)
Non Designated as Hedging Instrument [Member] | Financial institution counterparties Loan/lease interest-rate caps assets [Member]
Derivatives, Fair Value [Line Items]
Forward Contracts – Assets Notional Amount	265,930	270,431
Estimated Fair Value	8,110	3,239
Non Designated as Hedging Instrument [Member] | Customer counterparties Loan/lease interest rate swaps assets [Member]
Derivatives, Fair Value [Line Items]
Forward Contracts – Assets Notional Amount	447,742	928,756
Estimated Fair Value	10,275	39,864
Non Designated as Hedging Instrument [Member] | Customer counterparties Loan/lease interest rate swaps liabilities [Member]
Derivatives, Fair Value [Line Items]
Forward Contracts – Liability Notional Amount	697,834	247,592
Estimated Fair Value	(25,437)	(2,846)
Non Designated as Hedging Instrument [Member] | Customer counterparties Loan/lease interest rate caps liabilities [Member]
Derivatives, Fair Value [Line Items]
Forward Contracts – Liability Notional Amount	265,930	270,431
Estimated Fair Value	$ (8,110)	$ (3,239)

Derivative Financial Instrume_5

Derivative Financial Instruments - Schedule of Weighted-Average Rates Paid and Received for Interest Rate Swaps Outstanding (Detail)	Mar. 31, 2022
Weighted Average Interest Rate Paid [Member]
Short-duration insurance contracts, discounted liabilities [Line Items]
Fair value hedge loan/lease interest rate swaps	2.11%
Weighted-Average Interest Rate Received [Member]
Short-duration insurance contracts, discounted liabilities [Line Items]
Fair value hedge loan/lease interest rate swaps	0.26%
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	3.69%
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	2.07%
Customer Counterparties [Member] | Weighted Average Interest Rate Paid [Member]
Short-duration insurance contracts, discounted liabilities [Line Items]
Non-hedging interest rate swaps – customer counterparties	2.07%
Customer Counterparties [Member] | Weighted-Average Interest Rate Received [Member]
Short-duration insurance contracts, discounted liabilities [Line Items]
Non-hedging interest rate swaps – customer counterparties	3.69%

Derivative Financial Instrume_6

Derivative Financial Instruments - Schedule of Notional Amounts and Estimated Fair Values of Commodity Derivative Positions (Detail) bbl in Thousands, MMBTU in Thousands, $ in Thousands	Mar. 31, 2022USD ($)bblMMBTU	Dec. 31, 2021USD ($)MMBTUbbl
Financial Institution Counterparties [Member] | Oil Commodity Derivative [Member]
Derivative Instruments [Line Items]
Oil/Natural Gas Derivative Assets, Notional Amount | bbl	2,988	4,809
Oil/Natural Gas Derivative Liabilities, Notional Amount | bbl	9,767	7,032
Oil/Natural Gas Derivative Assets, Estimated Fair Value	$ 9,735	$ 14,721
Oil/Natural Gas Derivative Liabilities, Estimated Fair Value	$ (189,416)	$ (73,594)
Financial Institution Counterparties [Member] | Natural Gas Commodity Derivative [Member]
Derivative Instruments [Line Items]
Oil/Natural Gas Derivative Assets, Notional Amount | MMBTU	14,564	15,947
Oil/Natural Gas Derivative Liabilities, Notional Amount | MMBTU	27,474	29,446
Oil/Natural Gas Derivative Assets, Estimated Fair Value	$ 1,813	$ 4,143
Oil/Natural Gas Derivative Liabilities, Estimated Fair Value	$ (50,244)	$ (21,249)
Customer Counterparties [Member] | Oil Commodity Derivative [Member]
Derivative Instruments [Line Items]
Oil/Natural Gas Derivative Assets, Notional Amount | bbl	9,767	7,046
Oil/Natural Gas Derivative Liabilities, Notional Amount | bbl	2,988	4,796
Oil/Natural Gas Derivative Assets, Estimated Fair Value	$ 190,776	$ 74,437
Oil/Natural Gas Derivative Liabilities, Estimated Fair Value	$ (9,710)	$ (14,294)
Customer Counterparties [Member] | Natural Gas Commodity Derivative [Member]
Derivative Instruments [Line Items]
Oil/Natural Gas Derivative Assets, Notional Amount | MMBTU	27,474	29,446
Oil/Natural Gas Derivative Liabilities, Notional Amount | MMBTU	14,564	15,947
Oil/Natural Gas Derivative Assets, Estimated Fair Value	$ 50,423	$ 21,456
Oil/Natural Gas Derivative Liabilities, Estimated Fair Value	$ (1,811)	$ (4,124)

Derivative Financial Instrume_7

Derivative Financial Instruments - Schedule of Notional Amounts and Fair Values of Open Foreign Currency Forward Contracts (Details) € in Thousands, $ in Thousands, $ in Thousands	Mar. 31, 2022USD ($)	Mar. 31, 2022EUR (€)	Mar. 31, 2022CAD ($)	Dec. 31, 2021USD ($)	Dec. 31, 2021EUR (€)	Dec. 31, 2021CAD ($)
Financial Institution Counterparties [Member] | GBP Foreign Exchange Forward
Derivative Instruments [Line Items]
Forward Contracts – Assets Estimated Fair Value	$ 18			$ 29
Forward Contracts - Liability Estimated Fair Value	(111)			0
Financial Institution Counterparties [Member] | Foreign Exchange Forward [Member]
Derivative Instruments [Line Items]
Forward Contracts – Assets Estimated Fair Value	0			0
Forward Contracts - Liability Estimated Fair Value	(6)			0
Financial Institution Counterparties [Member] | Other Assets [Member] | Non Designated as Hedging Instrument [Member]
Derivative Instruments [Line Items]
Forward Contracts – Assets Notional Amount		€ 2,400	$ 0		€ 1,900	$ 658
Financial Institution Counterparties [Member] | Other Liabilities [Member] | Non Designated as Hedging Instrument [Member]
Derivative Instruments [Line Items]
Forward Contracts – Liability Notional Amount		6,500	658		0	0
Customer Counterparties [Member] | GBP Foreign Exchange Forward
Derivative Instruments [Line Items]
Forward Contracts – Assets Estimated Fair Value	122			0
Forward Contracts - Liability Estimated Fair Value	(14)			(55)
Customer Counterparties [Member] | Foreign Exchange Forward [Member]
Derivative Instruments [Line Items]
Forward Contracts – Assets Estimated Fair Value	$ 10			$ 4
Customer Counterparties [Member] | Other Assets [Member] | Non Designated as Hedging Instrument [Member]
Derivative Instruments [Line Items]
Forward Contracts – Assets Notional Amount		6,500	$ 658		0	$ 658
Customer Counterparties [Member] | Other Liabilities [Member] | Non Designated as Hedging Instrument [Member]
Derivative Instruments [Line Items]
Forward Contracts – Liability Notional Amount | €		€ 2,400			€ 1,900

Derivative Financial Instrume_8

Derivative Financial Instruments - Schedule of Amounts Related to Interest Rate Derivatives Designated as Hedges of Fair Value (Detail) - Designated as Hedging Instrument [Member] - Commercial Loan/Lease Interest Rate Swaps [Member] - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Interest Income on Loans [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of gain (loss) included in income	$ (13)	$ (28)
Other Non-Interest Expense [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of gain (loss) included in income	$ 2	$ (3)

Derivative Financial Instrume_9

Derivative Financial Instruments - Schedule of Amounts Related to Non-Hedging Interest Rate and Commodity Derivatives (Detail) - Non Designated as Hedging Instrument [Member] - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Interest Rate Contract [Member] | Other Non-Interest Income [Member]
Other Non Interest Income Non Hedging Interest Rate Derivatives [Line Items]
Amount of gain (loss) included in income (expense)	$ 516	$ 1,587
Interest Rate Contract [Member] | Other Non-Interest Expense [Member]
Other Non Interest Income Non Hedging Interest Rate Derivatives [Line Items]
Amount of gain (loss) included in income (expense)	0	(1)
Commodity Contract [Member] | Other Non-Interest Income [Member]
Other Non Interest Income Non Hedging Interest Rate Derivatives [Line Items]
Amount of gain (loss) included in income (expense)	929	1,154
Foreign Currency Derivative Contracts [Member] | Other Non-Interest Income [Member]
Other Non Interest Income Non Hedging Interest Rate Derivatives [Line Items]
Amount of gain (loss) included in income (expense)	$ 18	$ 30

Balance Sheet Offsetting - Fina

Balance Sheet Offsetting - Financial Instruments Eligible for Offset Consolidated Balance Sheet (Detail) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Gross Amount Recognized, Derivatives, Financial Assets	$ 34,988	$ 23,339
Gross Amount Offset, Derivatives, Financial assets	0	0
Net Amount Recognized, Derivatives, Financial assets	34,988	23,339
Gross Amount Recognized, Resell agreements, Financial assets	0	7,903
Gross Amount Offset, Resell agreements, Financial assets	0	0
Net Amount Recognized, Resell agreements, Financial assets	0	7,903
Gross Amount Recognized, Financial assets	34,988	31,242
Gross Amount Offset, Financial assets	0	0
Net Amount Recognized, Financial assets	34,988	31,242
Gross Amount Recognized, Derivatives, Financial Liabilities	245,964	114,019
Gross Amount Offset, Derivatives, Financial liabilities	0	0
Net Amount Recognized, Derivatives, Financial liabilities	245,964	114,019
Gross Amount Recognized, Repurchase agreements, Financial liabilities	1,842,618	2,740,799
Gross Amount Offset, Repurchase agreements, Financial liabilities	0	0
Net Amount Recognized, Repurchase agreements, Financial liabilities	1,842,618	2,740,799
Gross Amount Recognized, Financial liabilities	2,088,582	2,854,818
Gross Amount Offset, Financial liabilities	0	0
Net Amount Recognized, Financial Liabilities	2,088,582	2,854,818
Loan/lease interest rate swaps and caps [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Gross Amount Recognized, Derivatives, Financial Assets	23,422	4,446
Gross Amount Offset, Derivatives, Financial assets	0	0
Net Amount Recognized, Derivatives, Financial assets	23,422	4,446
Loan/lease interest rate swaps [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Gross Amount Recognized, Derivatives, Financial Liabilities	6,187	19,176
Gross Amount Offset, Derivatives, Financial liabilities	0	0
Net Amount Recognized, Derivatives, Financial liabilities	6,187	19,176
Commodity swaps and options [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Gross Amount Recognized, Derivatives, Financial Assets	11,548	18,864
Gross Amount Offset, Derivatives, Financial assets	0	0
Net Amount Recognized, Derivatives, Financial assets	11,548	18,864
Gross Amount Recognized, Derivatives, Financial Liabilities	239,660	94,843
Gross Amount Offset, Derivatives, Financial liabilities	0	0
Net Amount Recognized, Derivatives, Financial liabilities	239,660	$ 94,843
Foreign currency forward contracts [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Gross Amount Recognized, Derivatives, Financial Assets	18
Gross Amount Offset, Derivatives, Financial assets	0
Net Amount Recognized, Derivatives, Financial assets	18
Gross Amount Recognized, Derivatives, Financial Liabilities	117
Gross Amount Offset, Derivatives, Financial liabilities	0
Net Amount Recognized, Derivatives, Financial liabilities	$ 117

Balance Sheet Offsetting - Fi_2

Balance Sheet Offsetting - Financial Instruments Derivative Assets Liabilities and Resell Agreements Net of Amount Not Offset (Detail) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Net Amount Recognized, Derivatives, Financial Assets	$ 34,988	$ 23,339
Gross Amounts Not Offset, Financial Instruments, Total Derivatives, Financial Assets	(28,281)	(23,339)
Gross Amount Not Offset Collateral, Derivatives, Financial Assets	(6,707)	0
Net Amount, Derivatives, Financial Assets	0	0
Net Amount Recognized, Resell agreements, Financial Assets	0	7,903
Gross Amounts Not Offset Financial Instruments, Resell Agreements	0	0
Gross Amounts Not Offset Collateral, Resell Agreements, Financial Assets	0	(7,903)
Net Amount, Financial Assets, Resell Agreements	0	0
Net Amount Recognized, Total Financial Assets	34,988	31,242
Gross Amounts Not Offset Collateral, Financial Assets	(6,707)	(7,903)
Net Amount, Financial Assets	0	0
Net Amount Recognized, Derivatives, Financial Liabilities	245,964	114,019
Gross Amounts Not Offset Financial Instruments, Total Derivatives, Financial Liabilities	(28,281)	(23,339)
Gross Amounts Not Offset Collateral, Derivatives, Financial Liabilities	(217,683)	(90,573)
Net Amount, Derivatives, Financial Liabilities	0	107
Net Amount Recognized, Repurchase Agreements, Financial Liabilities	1,842,618	2,740,799
Gross Amounts Not Offset Financial Instruments, Repurchase Agreements, Financial Liabilities	0	0
Gross Amounts Not Offset Collateral, Repurchase Agreements, Financial Liabilities	(1,842,618)	(2,740,799)
Net Amount, Repurchase Agreements, Financial Liabilities	0	0
Net Amount Recognized, Financial Liabilities	2,088,582	2,854,818
Gross Amounts Not Offset Collateral, Financial Liabilities	(2,060,301)	(2,831,372)
Net Amount, Financial Liabilities	0	107
Counterparty A [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Net Amount Recognized, Derivatives, Financial Assets	32	6
Gross Amounts Not Offset, Financial Instruments, Total Derivatives, Financial Assets	(32)	(6)
Gross Amount Not Offset Collateral, Derivatives, Financial Assets	0	0
Net Amount, Derivatives, Financial Assets	0	0
Net Amount Recognized, Derivatives, Financial Liabilities	2,635	3,870
Gross Amounts Not Offset Financial Instruments, Total Derivatives, Financial Liabilities	(32)	(6)
Gross Amounts Not Offset Collateral, Derivatives, Financial Liabilities	(2,603)	(3,864)
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	11,998	7,655
Gross Amounts Not Offset, Financial Instruments, Total Derivatives, Financial Assets	(11,998)	(7,655)
Gross Amount Not Offset Collateral, Derivatives, Financial Assets	0	0
Net Amount, Derivatives, Financial Assets	0	0
Net Amount Recognized, Derivatives, Financial Liabilities	46,953	28,130
Gross Amounts Not Offset Financial Instruments, Total Derivatives, Financial Liabilities	(11,998)	(7,655)
Gross Amounts Not Offset Collateral, Derivatives, Financial Liabilities	(34,955)	(20,475)
Net Amount, Derivatives, Financial Liabilities	0	0
Counterparty C [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Net Amount Recognized, Derivatives, Financial Liabilities	3	9
Gross Amounts Not Offset Financial Instruments, Total Derivatives, Financial Liabilities	0	0
Gross Amounts Not Offset Collateral, Derivatives, Financial Liabilities	(3)	(9)
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	22,958	15,678
Gross Amounts Not Offset, Financial Instruments, Total Derivatives, Financial Assets	(16,251)	(15,678)
Gross Amount Not Offset Collateral, Derivatives, Financial Assets	(6,707)	0
Net Amount, Derivatives, Financial Assets	0	0
Net Amount Recognized, Derivatives, Financial Liabilities	196,373	82,010
Gross Amounts Not Offset Financial Instruments, Total Derivatives, Financial Liabilities	(16,251)	(15,678)
Gross Amounts Not Offset Collateral, Derivatives, Financial Liabilities	(180,122)	(66,225)
Net Amount, Derivatives, Financial Liabilities	$ 0	$ 107

Balance Sheet Offsetting Balanc

Balance Sheet Offsetting Balance Sheet Offsetting - Remaining Contractual Maturity of the Securities Sold Under Agreement to Repurchase (Details) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Remaining Contractual Maturity of the Securities Sold Under Agreement to Repurchase [Line Items]
Remaining contractual maturity of the agreements overnight and continuous	$ 1,842,618	$ 2,740,799
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	1,842,618	2,740,799
Securities Sold under Agreements to Repurchase, Gross	1,842,618	2,740,799
Securities Sold under Agreements to Repurchase, Collateral, Right to Reclaim Securities	0	0
US Treasury Securities [Member]
Remaining Contractual Maturity of the Securities Sold Under Agreement to Repurchase [Line Items]
Remaining contractual maturity of the agreements overnight and continuous	876,879	1,342,591
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	876,879	1,342,591
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	965,739	1,398,208
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	$ 965,739	$ 1,398,208

Stock-Based Compensation Stock-

Stock-Based Compensation Stock-Based Compensation - Narrative (Details)	Mar. 31, 2022shares
Performance Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant	794,493

Stock-Based Compensation - Summ

Stock-Based Compensation - Summary of Activity in Corporation's Active Stock Plans (Detail) - $ / shares	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock options exercised, Number of Shares	(115,430)	(513,824)
Director deferred stock units outstanding [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Beginning Balance, Number of Shares/Units	56,301
Ending Balance, Number of Shares/Units	56,301
Beginning Balance, Weighted-Average Grant-Date Fair Value	$ 79.21
Ending Balance, Weighted-Average Grant-Date Fair Value	$ 79.21
Non-Vested Stock Awards/Stock Units Outstanding [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Beginning Balance, Number of Shares/Units	449,337
Granted, Number of Units	1,038
Forfeited/expired, Number of Shares/Units	(1,786)
Ending Balance, Number of Shares/Units	448,589
Beginning Balance, Weighted-Average Grant-Date Fair Value	$ 93.05
Granted Weighted-Average Grant-Date Fair Value	145.32
Forfeited/Expired, Weighted-Average Price	89.50
Ending Balance, Weighted-Average Grant-Date Fair Value	$ 93.19
Stock Options Outstanding [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Beginning Balance, Number of Shares	877,681
Stock options exercised, Number of Shares	(90,250)
Ending Balance, Number of Shares	787,431
Beginning Balance, Weighted-Average Exercise Price	$ 69.02
Stock options exercised, Weighted-Average Exercise Price	63.59
Ending Balance, Weighted-Average Exercise Price	$ 69.64
Maximum [Member] | Performance Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Beginning Balance, Number of Shares/Units	202,460
Stock Awards exercised/vested, Number of Shares	(25,180)
Forfeited/expired, Number of Shares/Units	(16,058)
Ending Balance, Number of Shares/Units	161,222
Beginning Balance, Weighted-Average Grant-Date Fair Value	$ 84.71
Stock Award Exercised/Vested, Weighted Average Grant Date Fair Value	87.18
Forfeited/Expired, Weighted-Average Price	87.18
Ending Balance, Weighted-Average Grant-Date Fair Value	$ 84.08

Stock-Based Compensation - Shar

Stock-Based Compensation - Shares Issued in Connection with Stock Compensation Awards (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Share-based Payment Arrangement [Abstract]
New shares issued from available authorized shares	0	0
Shares issued from available treasury stock	115,430	513,824
Proceeds from stock option exercises	$ 5,739	$ 29,397

Stock-Based Compensation - Stoc

Stock-Based Compensation - Stock-Based Compensation Expense (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Non-vested stock units	$ 2,358	$ 1,883
Share-based compensation benefit on performance stock units	(246)
Share-based compensation expense on performance stock units		643
Total	2,112	2,526
Income tax benefit	$ 708	$ 367

Stock-Based Compensation - Unre

Stock-Based Compensation - Unrecognized Stock-Based Compensation Expense (Detail) $ in Thousands	Mar. 31, 2022USD ($)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Non-vested stock units	$ 16,063
Performance stock units	8,664
Total	$ 24,727

Earnings Per Common Share - Bas

Earnings Per Common Share - Basic and Diluted Earnings Per Common Share (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Earnings Per Share [Abstract]
Net income	$ 99,102	$ 116,015
Less: Preferred stock dividends	1,669	2,151
Net income available to common shareholders	97,433	113,864
Less: Earnings allocated to participating securities	849	1,162
Distributed earnings allocated to common stock	48,051	45,660
Undistributed earnings allocated to common stock	48,533	67,042
Net earnings allocated to common stock	$ 96,584	$ 112,702
Weighted-average shares outstanding for basic earnings per common share	64,051,202	63,306,493
Dilutive effect of stock compensation	409,705	509,290
Weighted-average shares outstanding for diluted earnings per common share	64,460,907	63,815,783

Defined Benefit Plans Additiona

Defined Benefit Plans Additional Information (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2022USD ($)
Retirement Benefits [Abstract]
Defined Benefit Plan, Plan Assets, Contributions by Employer	$ 0
Defined Benefit Plan, Expected Future Employer Contributions, Current Fiscal Year	$ 0

Defined Benefit Plans - Net Per

Defined Benefit Plans - Net Periodic Cost (Benefit) (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Retirement Benefits [Abstract]
Expected return on plan assets, net of expenses	$ (3,491)	$ (3,210)
Interest cost on projected benefit obligation	1,004	835
Net amortization and deferral	741	1,529
Net periodic expense (benefit)	$ (1,746)	$ (846)

Income Taxes - Additional Infor

Income Taxes - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021	Dec. 31, 2021
Income Tax Disclosure [Abstract]
Deferred Tax Assets, Net	$ 110.3
Deferred Tax Liabilities, Net			$ 81.2
Valuation allowance	$ 0
U.S. federal statutory income tax rate, percent	21.00%	21.00%
Unrecognized tax benefits	$ 0	$ 0

Income Taxes - Income Tax Expen

Income Taxes - Income Tax Expense (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Income Tax Disclosure [Abstract]
Current income tax expense (benefit)	$ 13,059	$ 3,725
Deferred income tax expense (benefit)	(432)	4,172
Income tax expense, as reported	$ 12,627	$ 7,897
Effective tax rate	11.30%	6.40%

Other Comprehensive Income (L_3

Other Comprehensive Income (Loss) - Component of Other Comprehensive Income (Loss) (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Equity [Abstract]
Securities available for sale and transferred securities, Change in net unrealized gain/loss during the period, Before Tax Amount	$ (910,795)	$ (159,779)
Securities available for sale and transferred securities, Change in net unrealized gain on securities transferred to held to maturity, Before Tax Amount	(209)	(259)
Securities available for sale and transferred securities, Reclassification adjustment for net (gains) losses included in net income, Before Tax Amount	0	0
Total securities available for sale and transferred securities, before tax amount	(911,004)	(160,038)
Reclassification adjustment for net amortization of actuarial gain/loss included in net income as a component of net periodic cost (benefit), before tax amount	741	1,529
Total defined-benefit post-retirement benefit plans	741	1,529
Total other comprehensive income (loss), before tax	(910,263)	(158,509)
Securities available for sale and transferred securities, Change in net unrealized gain/loss during the period, Tax Expense (Benefit)	(191,267)	(33,554)
Securities available for sale and transferred securities, Change in net unrealized gain on securities transferred to held to maturity, Tax Expense (Benefit)	(44)	(54)
Securities available for sale and transferred securities, Reclassification adjustment for net (gains) losses included in net income, Tax Expense (Benefit)	0	0
Total securities available for sale and transferred securities, Tax Expense (Benefit)	(191,311)	(33,608)
Reclassification adjustment for net amortization of actuarial gain/loss included in net income as a component of net periodic cost (benefit), Tax Expense (Benefit)	156	321
Total defined-benefit post-retirement benefit plans, Tax Expense (Benefit)	156	321
Total other comprehensive income (loss), Tax Expense (Benefit)	(191,155)	(33,287)
Securities available for sale and transferred securities, Change in net unrealized gain/loss during the period, Net of Tax	(719,528)	(126,225)
Securities available for sale and transferred securities, Change in net unrealized gain on securities transferred to held to maturity, Net of Tax	(165)	(205)
Securities available for sale and transferred securities, Reclassification adjustment for net (gains) losses included in net income, Net of Tax	0	0
Total securities available for sale and transferred securities, Net of Tax	(719,693)	(126,430)
Reclassification adjustment for net amortization of actuarial gain/lloss included in net income as a component of net periodic cost (benefit), Net of Tax	585	1,208
Total defined-benefit post-retirement benefit plans, Net of Tax Amount	585	1,208
Other comprehensive income (loss), net of tax	$ (719,108)	$ (125,222)

Other Comprehensive Income - Sc

Other Comprehensive Income - Schedule of Accumulated Other Comprehensive Income, Net of Tax (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning Balance	$ 347,318
Other comprehensive income (loss), net of tax	(719,108)	$ (125,222)
Ending Balance	(371,790)
Securities Available For Sale [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning Balance	380,209	563,801
Other comprehensive income (loss) before reclassifications	(719,693)	(126,430)
Reclassification of amounts included in net income	0	0
Other comprehensive income (loss), net of tax	(719,693)	(126,430)
Ending Balance	(339,484)	437,371
Defined Benefit Plans [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning Balance	(32,891)	(50,831)
Other comprehensive income (loss) before reclassifications	0	0
Reclassification of amounts included in net income	585	1,208
Other comprehensive income (loss), net of tax	585	1,208
Ending Balance	(32,306)	(49,623)
AOCI Attributable to Parent [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning Balance	347,318	512,970
Other comprehensive income (loss) before reclassifications	(719,693)	(126,430)
Reclassification of amounts included in net income	585	1,208
Other comprehensive income (loss), net of tax	(719,108)	(125,222)
Ending Balance	$ (371,790)	$ 387,748

Operating Segments - Additional

Operating Segments - Additional Information (Detail)	3 Months Ended
	Mar. 31, 2022Segment
Segment Reporting [Abstract]
Number of primary operating segments	2

Operating Segments - Summary of

Operating Segments - Summary of Operating Results by Segment (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Segment Reporting Information [Line Items]
Interest Income (Expense), Net	$ 249,071	$ 240,881
Credit loss expense	0	63
Total non-interest income	101,390	93,236
Total non-interest expense	238,732	210,142
Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest	111,729	123,912
Income taxes	12,627	7,897
Net income	99,102	116,015
Less: Preferred stock dividends	1,669	2,151
Net Income (Loss) Available to Common Stockholders, Basic	97,433	113,864
Revenues from (expenses to) external customers	350,461	334,117
Bank
Segment Reporting Information [Line Items]
Interest Income (Expense), Net	250,119	242,205
Credit loss expense	(1)	63
Total non-interest income	58,706	53,780
Total non-interest expense	206,538	179,151
Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest	102,288	116,771
Income taxes	11,014	7,177
Net income	91,274	109,594
Less: Preferred stock dividends	0	0
Net Income (Loss) Available to Common Stockholders, Basic	91,274	109,594
Revenues from (expenses to) external customers	308,825	295,985
Frost Wealth Advisors [Member]
Segment Reporting Information [Line Items]
Interest Income (Expense), Net	700	486
Credit loss expense	1	0
Total non-interest income	43,229	39,609
Total non-interest expense	30,910	29,937
Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest	13,018	10,158
Income taxes	2,734	2,133
Net income	10,284	8,025
Less: Preferred stock dividends	0	0
Net Income (Loss) Available to Common Stockholders, Basic	10,284	8,025
Revenues from (expenses to) external customers	43,929	40,095
Non-Banks [Member]
Segment Reporting Information [Line Items]
Interest Income (Expense), Net	(1,748)	(1,810)
Credit loss expense	0	0
Total non-interest income	(545)	(153)
Total non-interest expense	1,284	1,054
Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest	(3,577)	(3,017)
Income taxes	(1,121)	(1,413)
Net income	(2,456)	(1,604)
Less: Preferred stock dividends	1,669	2,151
Net Income (Loss) Available to Common Stockholders, Basic	(4,125)	(3,755)
Revenues from (expenses to) external customers	$ (2,293)	$ (1,963)

Fair Value Measurements - Addit

Fair Value Measurements - Additional Information (Detail) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments using fair value measurement option	$ 0	$ 0

Fair Value Measurements - Finan

Fair Value Measurements - Financial Assets and Financial Liabilities Measured at Fair Value on Recurring Basis (Detail) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale, at estimated fair value	$ 16,184,539	$ 13,924,628
Trading account securities	29,518	25,162
Derivative assets	34,988	23,339
Derivative liabilities	245,964	114,019
Interest rate swaps, caps and floors [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	33,697	44,310
Derivative liabilities	39,734	25,261
Commodity swaps and options [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	252,747	114,757
Derivative liabilities	251,181	113,261
Foreign Exchange Forward [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	150	33
Derivative liabilities	131	55
U.S. Treasury [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale, at estimated fair value	3,507,746	2,179,433
Trading account securities	23,939	24,237
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	5,376,039	4,066,265
States and political subdivisions [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale, at estimated fair value	7,258,393	7,636,571
Trading account securities	5,579	925
Other [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale, at estimated fair value	42,361	42,359
Level 1 [Member] | Foreign Exchange Forward [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	150	33
Derivative liabilities	131	55
Level 1 [Member] | U.S. Treasury [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale, at estimated fair value	3,507,746	2,179,433
Trading account securities	23,939	24,237
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	33,697	44,310
Derivative liabilities	39,734	25,261
Level 2 [Member] | Commodity swaps and options [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	252,747	114,757
Derivative liabilities	251,181	113,261
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	5,376,039	4,066,265
Level 2 [Member] | States and political subdivisions [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale, at estimated fair value	7,258,393	7,636,571
Trading account securities	5,579	925
Level 2 [Member] | Other [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale, at estimated fair value	$ 42,361	$ 42,359

Fair Value Measurements - Impai

Fair Value Measurements - Impaired Loans Remeasured and Reported at Fair Value of Underlying Collateral (Detail) - USD ($) $ in Thousands	Mar. 31, 2022	Mar. 31, 2021
Level 2 [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Carrying value of impaired loans before allocations	$ 2,064	$ 100
Impaired Financing Receivable, Related Allowance	(126)	0
Loans receivable, fair value disclosure	1,938	100
Level 3 [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Carrying value of impaired loans before allocations	5,711	15,013
Impaired Financing Receivable, Reversal of Specific Valuation Allowance Allocations	3,965	600
Loans receivable, fair value disclosure	$ 9,676	$ 15,613

Fair Value Measurements - Estim

Fair Value Measurements - Estimated Fair Values of Financial Instruments (Detail) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Securities held to maturity	$ 1,665,465	$ 1,749,179
Loans, net	16,295,702	16,087,731
Deposits	44,430,929	42,695,696
Federal funds purchased	35,200	25,925
Repurchase agreements	1,842,618	2,740,799
Junior subordinated deferrable interest debentures, net of unamortized issuance costs	123,026	123,011
Subordinated notes	99,217	99,178
Carrying Amount [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	14,457,083	16,583,000
Securities held to maturity	1,665,465	1,749,179
Cash surrender value of life insurance policies	189,471	190,139
Accrued interest receivable	131,370	179,111
Deposits	44,430,929	42,695,696
Federal funds purchased	35,200	25,925
Repurchase agreements	1,842,618	2,740,799
Junior subordinated deferrable interest debentures, net of unamortized issuance costs	123,026	123,011
Subordinated notes	99,217	99,178
Accrued interest payable	2,147	3,026
Carrying Amount [Member] | Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans, net	16,295,702	16,087,731
Estimated Fair Value [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	14,457,083	16,583,000
Securities held to maturity	1,639,993	1,809,143
Cash surrender value of life insurance policies	189,471	190,139
Accrued interest receivable	131,370	179,111
Deposits	44,422,700	41,343,426
Federal funds purchased	35,200	25,925
Repurchase agreements	1,842,618	2,740,799
Junior subordinated deferrable interest debentures, net of unamortized issuance costs	123,712	123,712
Subordinated notes	105,740	111,430
Accrued interest payable	2,147	3,026
Estimated Fair Value [Member] | Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans, net	$ 16,053,955	$ 16,079,454