Cullen/Frost Bankers (CFR) 10-Q 28 Jul 22 2022 Q2 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - $ / shares	6 Months Ended
	Jun. 30, 2022	Jul. 21, 2022	Dec. 31, 2021
Entity Information [Line Items]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Jun. 30, 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		64,127,979
Common stock, par value	$ 0.01		$ 0.01
Amendment Flag	false
Document Fiscal Year Focus	2022
Document Fiscal Period Focus	Q2
Entity Central Index Key	0000039263
Current Fiscal Year End Date	--12-31
Common Stock [Member] | NEW YORK STOCK EXCHANGE, INC. [Member]
Entity Information [Line Items]
Title of 12(b) Security	Common Stock, $.01 Par Value
Trading Symbol	CFR
Security Exchange Name	NYSE
Series B Preferred Stock [Member] | NEW YORK STOCK EXCHANGE, INC. [Member]
Entity Information [Line Items]
Title of 12(b) Security	Depositary Shares, each representing a 1/40th interest in a share of 4.450% Non-Cumulative Perpetual Preferred Stock, Series B
Trading Symbol	CFR.PrB
Security Exchange Name	NYSE

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Jun. 30, 2022	Dec. 31, 2021
Assets:
Cash and due from banks	$ 743,098	$ 555,778
Interest-bearing deposits	12,809,937	15,985,244
Federal funds sold	95,900	34,075
Resell agreements	9,650	7,903
Total cash and cash equivalents	13,658,585	16,583,000
Securities held to maturity, net of allowance for credit losses of $158 at June 30, 2022 and $158 at December 31, 2021	1,946,428	1,749,179
Securities available for sale, at estimated fair value	16,781,685	13,924,628
Trading account securities	24,680	25,162
Loans, net of unearned discounts	16,736,026	16,336,397
Less: Allowance for credit losses on loans	(239,632)	(248,666)
Net loans	16,496,394	16,087,731
Premises and equipment, net	1,046,495	1,050,331
Goodwill	654,952	654,952
Other intangible assets, net	589	866
Cash surrender value of life insurance policies	189,823	190,139
Accrued interest receivable and other assets	985,257	612,502
Total assets	51,784,888	50,878,490
Liabilities:
Non-interest-bearing demand deposits	18,783,931	18,423,018
Interest-bearing deposits	26,817,834	24,272,678
Total deposits	45,601,765	42,695,696
Federal funds purchased	43,200	25,925
Repurchase agreements	1,664,685	2,740,799
Junior Subordinated Notes	123,040	123,011
Subordinated notes, net of unamortized issuance costs	99,256	99,178
Accrued interest payable and other liabilities	905,967	754,326
Total liabilities	48,437,913	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 June 30, 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 June 30, 2022 and December 31, 2021	642	642
Additional paid-in capital	1,015,451	1,009,921
Retained earnings	3,070,109	2,956,966
Accumulated other comprehensive income (loss), net of tax	(874,206)	347,318
Treasury stock, at cost; 113,267 shares at June 30, 2022 and 250,070 shares at December 31, 2021	(10,473)	(20,744)
Total shareholders’ equity	3,346,975	4,439,555
Total liabilities and shareholders’ equity	$ 51,784,888	$ 50,878,490

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Jun. 30, 2022	Dec. 31, 2021
Securities, held-to-maturity, allowance for credit loss	$ 158	$ 158
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	113,267	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	$ 150,000

Consolidated Statements of Inco

Consolidated Statements of Income - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Interest income:
Loans, including fees	$ 166,679	$ 182,695	$ 316,656	$ 350,178
Securities:
Taxable	56,365	20,602	99,423	40,630
Tax-exempt	57,078	56,111	113,944	112,774
Interest-bearing deposits	26,371	3,614	32,714	6,047
Federal funds sold	99	8	112	11
Resell agreements	10	4	14	5
Total interest income	306,602	263,034	562,863	509,645
Interest expense:
Deposits	14,593	3,499	19,505	7,016
Federal funds purchased	75	7	87	15
Repurchase agreements	1,790	570	2,308	965
Junior subordinated deferrable interest debentures	772	638	1,356	1,284
Subordinated notes	1,164	1,164	2,328	2,328
Total interest expense	18,394	5,878	25,584	11,608
Net interest income	288,208	257,156	537,279	498,037
Credit loss expense	0	0	0	63
Net interest income after credit loss expense	288,208	257,156	537,279	497,974
Non-interest income:
Trust and investment management fees	37,776	37,874	76,432	73,188
Service charges on deposit accounts	23,870	19,849	46,610	39,842
Insurance commissions and fees	11,776	10,773	28,384	28,086
Interchange and card transaction fees	4,911	4,641	9,137	8,734
Other charges, commissions and fees	9,887	8,640	19,514	16,944
Net gain (loss) on securities transactions	0	0	0	0
Other	9,707	9,470	19,240	17,689
Total non-interest income	97,927	91,247	199,317	184,483
Non-interest expense:
Salaries and wages	116,881	97,035	228,210	190,493
Employee benefits	20,733	18,728	44,953	41,264
Net occupancy	28,379	26,650	55,790	52,701
Technology, furniture and equipment	29,921	27,998	59,078	56,014
Deposit insurance	3,724	2,877	7,357	5,805
Intangible amortization	131	185	277	387
Other	46,578	41,781	89,414	78,732
Total non-interest expense	246,347	215,254	485,079	425,396
Income before income taxes	139,788	133,149	251,517	257,061
Income taxes	20,674	15,081	33,301	22,978
Net income	119,114	118,068	218,216	234,083
Preferred stock dividends	1,669	1,669	3,338	3,820
Net income available to common shareholders	$ 117,445	$ 116,399	$ 214,878	$ 230,263
Earnings per common share:
Basic	$ 1.82	$ 1.81	$ 3.32	$ 3.59
Diluted	$ 1.81	$ 1.80	$ 3.31	$ 3.57

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Net income	$ 119,114	$ 118,068	$ 218,216	$ 234,083
Other comprehensive income (loss), before tax:
Change in net unrealized gain/loss on securities available for sale during the period	(636,523)	30,668	(1,547,318)	(129,111)
Change in net unrealized gain on securities transferred to held to maturity	(189)	(245)	(398)	(504)
Reclassification adjustment for net (gains) losses included in net income	0	0	0	0
Total securities available for sale and transferred securities, before tax amount	(636,712)	30,423	(1,547,716)	(129,615)
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	1,482	3,058
Total defined-benefit post-retirement benefit plans	741	1,529	1,482	3,058
Other comprehensive income (loss), before tax	(635,971)	31,952	(1,546,234)	(126,557)
Deferred tax expense (benefit)	(133,555)	6,710	(324,710)	(26,577)
Other comprehensive income (loss), net of tax	(502,416)	25,242	(1,221,524)	(99,980)
Comprehensive income (loss)	$ (383,302)	$ 143,310	$ (1,003,308)	$ 134,103

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	234,083				234,083
Other comprehensive income (loss)	(99,980)					(99,980)
Stock option exercises/stock unit conversions (28,832 shares QTD and 144,262 shares YTD in 2022 and 114,252 shares QTD and 628,076 shares YTD in 2021)	36,682				(25,567)		62,249
Stock compensation expense recognized in earnings	5,771			5,771
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 and $22.25 per share which is equivalent to approximately $0.28 and $0.56 per depository share QTD and YTD in 2022, respectively and $11.13 and $25.46 per share which is equivalent to approximately $0.28 and $0.64 per depository share QTD and YTD in 2021, respectively)	(3,820)				(3,820)
Cash dividends – common stock ($0.75 per share QTD and $1.50 per share YTD in 2022 and $0.72 per share QTD and $1.44 per share YTD in 2021)	(92,396)				(92,396)
Total shareholders’ equity at end of period at Jun. 30, 2021	4,373,817	145,452	642	1,002,939	2,862,966	412,990	(51,172)
Total shareholders’ equity at beginning of period at Mar. 31, 2021	4,267,918	145,452	642	999,694	2,797,064	387,748	(62,682)
Net income	118,068				118,068
Other comprehensive income (loss)	25,242					25,242
Stock option exercises/stock unit conversions (28,832 shares QTD and 144,262 shares YTD in 2022 and 114,252 shares QTD and 628,076 shares YTD in 2021)	7,285				(4,225)		11,510
Stock compensation expense recognized in earnings	3,245			3,245
Cash dividends – preferred stock (approximately $11.13 and $22.25 per share which is equivalent to approximately $0.28 and $0.56 per depository share QTD and YTD in 2022, respectively and $11.13 and $25.46 per share which is equivalent to approximately $0.28 and $0.64 per depository share QTD and YTD in 2021, respectively)	(1,669)				(1,669)
Cash dividends – common stock ($0.75 per share QTD and $1.50 per share YTD in 2022 and $0.72 per share QTD and $1.44 per share YTD in 2021)	(46,272)				(46,272)
Total shareholders’ equity at end of period at Jun. 30, 2021	4,373,817	145,452	642	1,002,939	2,862,966	412,990	(51,172)
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	218,216				218,216
Other comprehensive income (loss)	(1,221,524)					(1,221,524)
Stock option exercises/stock unit conversions (28,832 shares QTD and 144,262 shares YTD in 2022 and 114,252 shares QTD and 628,076 shares YTD in 2021)	6,490				(4,777)		11,267
Stock compensation expense recognized in earnings	5,530			5,530
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 and $22.25 per share which is equivalent to approximately $0.28 and $0.56 per depository share QTD and YTD in 2022, respectively and $11.13 and $25.46 per share which is equivalent to approximately $0.28 and $0.64 per depository share QTD and YTD in 2021, respectively)	(3,338)				(3,338)
Cash dividends – common stock ($0.75 per share QTD and $1.50 per share YTD in 2022 and $0.72 per share QTD and $1.44 per share YTD in 2021)	(96,958)				(96,958)
Total shareholders’ equity at end of period at Jun. 30, 2022	3,346,975	145,452	642	1,015,451	3,070,109	(874,206)	(10,473)
Total shareholders’ equity at beginning of period at Mar. 31, 2022	3,776,292	145,452	642	1,012,033	3,002,642	(371,790)	(12,687)
Net income	119,114				119,114
Other comprehensive income (loss)	(502,416)					(502,416)
Stock option exercises/stock unit conversions (28,832 shares QTD and 144,262 shares YTD in 2022 and 114,252 shares QTD and 628,076 shares YTD in 2021)	751				(1,463)		2,214
Stock compensation expense recognized in earnings	3,418			3,418
Cash dividends – preferred stock (approximately $11.13 and $22.25 per share which is equivalent to approximately $0.28 and $0.56 per depository share QTD and YTD in 2022, respectively and $11.13 and $25.46 per share which is equivalent to approximately $0.28 and $0.64 per depository share QTD and YTD in 2021, respectively)	(1,669)				(1,669)
Cash dividends – common stock ($0.75 per share QTD and $1.50 per share YTD in 2022 and $0.72 per share QTD and $1.44 per share YTD in 2021)	(48,515)				(48,515)
Total shareholders’ equity at end of period at Jun. 30, 2022	$ 3,346,975	$ 145,452	$ 642	$ 1,015,451	$ 3,070,109	$ (874,206)	$ (10,473)

Consolidated Statements of Ch_2

Consolidated Statements of Changes in Shareholders' Equity (Parenthetical) - $ / shares	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Statement of Stockholders' Equity [Abstract]
Stock option exercise/stock unit conversions (28,832 shares QTD and 144,262 shares YTD in 2022 and 114,252 shares QTD and 628,076 shares YTD during 2021)	28,832	114,252	144,262	628,076
Purchase of treasury stock (7,459 shares YTD in 2022 and 11,625 shares YTD in 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 and $22.25 per share QTD and YTD in 2022, respectively and $11.13 and $25.46 per share QTD and YTD during 2021, respectively)	$ 11.13	$ 11.13	$ 22.25	$ 25.46
Cash dividend - Preferred Stock Dividends equivalent Per depositary Share Declared ($0.28 and $0.56 QTD and YTD respectively, during 2022 and $0.28 and 0.64 QTD and YTD, respectively during 2021)	0.28	0.28	0.56	0.64
Cash dividends - common stock ($0.75 per share QTD and $1.50 per share YTD in 2022 and $0.72 per share QTD and $1.44 per share YTD in 2021)	$ 0.75	$ 0.72	$ 1.50	$ 1.44

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021
Operating Activities:
Net income	$ 218,216	$ 234,083
Adjustments to reconcile net income to net cash from operating activities:
Credit loss expense	0	63
Deferred tax expense (benefit)	(2,404)	5,188
Accretion of loan discounts	(6,581)	(6,577)
Securities premium amortization (discount accretion), net	53,225	60,434
Net (gain) loss on securities transactions	0	0
Depreciation and amortization	35,406	34,060
Net (gain) loss on sale/write-down of assets/foreclosed assets	103	(1,876)
Stock-based compensation	5,530	5,771
Net tax benefit from stock-based compensation	1,645	4,218
Earnings on life insurance policies	(1,016)	(1,343)
Net change in:
Trading account securities	482	319
Lease right-of-use assets	12,042	11,697
Accrued interest receivable and other assets	(135,239)	(39,195)
Accrued interest payable and other liabilities	113,645	41,748
Net cash from operating activities	295,054	348,590
Investing Activities:
Securities held-to-maturity - Purchases	(411,527)	0
Securities held to maturity: Maturities, calls and principal repayments	263,226	122,416
Securities available for sale:
Purchases	(4,778,475)	(801,167)
Sales	0	0
Maturities, calls and principal repayments	382,152	576,763
Proceeds from sale of loans	2,365	0
Net change in loans	(404,515)	884,799
Benefits received on life insurance policies	1,332	1,509
Proceeds from sales of premises and equipment	18	6,436
Purchases of premises and equipment	(28,016)	(28,053)
Proceeds from sales of repossessed properties	1,543	100
Net cash from investing activities	(4,971,897)	762,803
Financing Activities:
Net change in deposits	2,906,069	3,718,379
Net change in short-term borrowings	(1,058,839)	126,592
Proceeds from stock option exercises	6,490	36,682
Purchase of treasury stock	(996)	(1,288)
Cash dividends paid on preferred stock	(3,338)	(3,820)
Cash dividends paid on common stock	(96,958)	(92,396)
Net cash from financing activities	1,752,428	3,784,149
Net change in cash and cash equivalents	(2,924,415)	4,895,542
Cash and cash equivalents at beginning of period	16,583,000	10,288,853
Cash and cash equivalents at end of period	$ 13,658,585	$ 15,184,395

Significant Accounting Policies

Significant Accounting Policies	6 Months Ended
	Jun. 30, 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: Six Months Ended 2022 2021 Cash paid for interest $ 22,551 $ 15,936 Cash paid for income taxes 45,500 15,400 Significant non-cash transactions: Unsettled securities transactions 110,623 358,752 Loans foreclosed and transferred to other real estate owned and foreclosed assets — 3,251 Right-of-use lease assets obtained in exchange for lessee operating lease liabilities 8,857 1,552 Treasury stock issued to 401(k) stock purchase plan — 1,749

Securities

Securities	6 Months Ended
	Jun. 30, 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 June 30, 2022 and December 31, 2021 is presented below. Amortized Gross Gross Estimated Allowance Net June 30, 2022 Residential mortgage-backed securities $ 526,675 $ — $ 40,383 $ 486,292 $ — $ 526,675 States and political subdivisions 1,418,411 3,956 81,583 1,340,784 (158) 1,418,253 Other 1,500 — 61 1,439 — 1,500 Total $ 1,946,586 $ 3,956 $ 122,027 $ 1,828,515 $ (158) $ 1,946,428 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 $245.5 million and $642.3 million at June 30, 2022 and December 31, 2021, respectively. Accrued interest receivable on held-to-maturity securities totaled $18.0 million and $18.4 million at June 30, 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 $2.1 million ($1.7 million, net of tax) at June 30, 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 June 30, 2022 and December 31, 2021: States and Political Subdivisions Not Guaranteed or Pre-Refunded Guaranteed by the Texas PSF Pre-Refunded Total Other June 30, 2022 Aaa/AAA $ 161,274 $ 764,405 $ 344,335 $ 1,270,014 $ — Aa/AA 148,397 — — 148,397 — Not rated — — — — 1,500 Total $ 309,671 $ 764,405 $ 344,335 $ 1,418,411 $ 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 and six months ended June 30, 2022 and 2021. Three Months Ended Six Months Ended 2022 2021 2022 2021 Beginning balance $ 158 $ 158 $ 158 $ 160 Credit loss expense (benefit) — — — (2) Ending balance $ 158 $ 158 $ 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 June 30, 2022 and December 31, 2021 is presented below. Amortized Gross Gross Allowance Estimated June 30, 2022 U.S. Treasury $ 4,656,896 $ 2,093 $ 242,690 $ — $ 4,416,299 Residential mortgage-backed securities 5,967,803 3,443 635,521 — 5,335,725 States and political subdivisions 7,183,199 50,465 246,368 — 6,987,296 Other 42,365 — — — 42,365 Total $ 17,850,263 $ 56,001 $ 1,124,579 $ — $ 16,781,685 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 June 30, 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 75.3% 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 $4.4 billion and $5.8 billion at June 30, 2022 and December 31, 2021, respectively. Accrued interest receivable on available-for-sale securities totaled $131.3 million and $120.5 million at June 30, 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 June 30, 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 $ 4,224,018 $ 242,690 $ — $ — $ 4,224,018 $ 242,690 Residential mortgage-backed securities 4,825,871 568,405 369,098 67,116 5,194,969 635,521 States and political subdivisions 3,249,625 241,884 13,824 4,484 3,263,449 246,368 Total $ 12,299,514 $ 1,052,979 $ 382,922 $ 71,600 $ 12,682,436 $ 1,124,579 As of June 30, 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 June 30, 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 $ 3 $ — $ 514,582 $ 12,090 $ 526,675 States and political subdivisions 350,365 84,053 22,102 961,891 1,418,411 Other — 1,500 — — 1,500 Total $ 350,368 $ 85,553 $ 536,684 $ 973,981 $ 1,946,586 Estimated Fair Value Residential mortgage-backed securities $ 3 $ — $ 475,721 $ 10,568 $ 486,292 States and political subdivisions 351,237 84,787 22,166 882,594 1,340,784 Other — 1,439 — — 1,439 Total $ 351,240 $ 86,226 $ 497,887 $ 893,162 $ 1,828,515 Available For Sale Amortized Cost U. S. Treasury $ — $ 3,031,706 $ 1,433,320 $ 191,870 $ 4,656,896 Residential mortgage-backed securities 55 11,080 18,743 5,937,925 5,967,803 States and political subdivisions 207,078 1,546,995 902,953 4,526,173 7,183,199 Other — — — — 42,365 Total $ 207,133 $ 4,589,781 $ 2,355,016 $ 10,655,968 $ 17,850,263 Estimated Fair Value U. S. Treasury $ — $ 2,957,018 $ 1,301,539 $ 157,742 $ 4,416,299 Residential mortgage-backed securities 55 11,231 18,792 5,305,647 5,335,725 States and political subdivisions 209,138 1,579,097 893,132 4,305,929 6,987,296 Other — — — — 42,365 Total $ 209,193 $ 4,547,346 $ 2,213,463 $ 9,769,318 $ 16,781,685 Sales of Securities. No held to maturity or available for sale securities were sold during the three or six months ended June 30, 2022 or 2021. Premiums and Discounts . Premium amortization and discount accretion included in interest income on securities was as follows: Three Months Ended Six Months Ended 2022 2021 2022 2021 Premium amortization $ (28,053) $ (30,541) $ (57,113) $ (61,776) Discount accretion 2,482 705 3,888 1,342 Net (premium amortization) discount accretion $ (25,571) $ (29,836) $ (53,225) $ (60,434) Trading Account Securities. Trading account securities, at estimated fair value, were as follows: June 30, December 31, U.S. Treasury $ 24,615 $ 24,237 States and political subdivisions 65 925 Total $ 24,680 $ 25,162 Net gains and losses on trading account securities were as follows: Three Months Ended Six Months Ended 2022 2021 2022 2021 Net gain on sales transactions $ 1,012 $ 293 $ 1,352 $ 402 Net mark-to-market gains (losses) (76) — (244) (69) Net gain (loss) on trading account securities $ 936 $ 293 $ 1,108 $ 333

Loans

Loans	6 Months Ended
	Jun. 30, 2022
Receivables [Abstract]
Loans	Loans Loans were as follows: June 30, December 31, Commercial and industrial $ 5,539,277 $ 5,364,954 Energy: Production 762,625 878,436 Service 121,356 105,901 Other 103,944 93,455 Total energy 987,925 1,077,792 Paycheck Protection Program 91,919 428,882 Commercial real estate: Commercial mortgages 6,041,606 5,867,062 Construction 1,535,808 1,304,271 Land 478,674 405,277 Total commercial real estate 8,056,088 7,576,610 Consumer real estate: Home equity loans 352,633 324,157 Home equity lines of credit 603,907 519,098 Other 604,495 567,535 Total consumer real estate 1,561,035 1,410,790 Total real estate 9,617,123 8,987,400 Consumer and other 499,782 477,369 Total loans $ 16,736,026 $ 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 June 30, 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 5.9% of total loans (also 5.9% excluding PPP loans). Unfunded commitments to extend credit and standby letters of credit issued to customers in the energy industry totaled $887.3 million and $79.1 million, respectively, as of June 30, 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 June 30, 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 $342.5 million at June 30, 2022 and $350.5 million at December 31, 2021. Accrued Interest Receivable. Accrued interest receivable on loans totaled $44.8 million and $40.0 million at June 30, 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: June 30, 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 $ 11,170 $ 3,093 $ 22,582 $ 4,701 Energy 11,114 6,442 14,433 8,533 Paycheck Protection Program — — — — Commercial real estate: Buildings, land and other 11,806 6,419 15,297 13,817 Construction — — 948 — Consumer real estate 1,035 732 440 138 Consumer and other — — 13 13 Total $ 35,125 $ 16,686 $ 53,713 $ 27,202 The following table presents non-accrual loans as of June 30, 2022 by class and year of origination. 2022 2021 2020 2019 2018 Prior Revolving Loans Revolving Loans Converted to Term Total Commercial and industrial $ — $ 98 $ 3,520 $ 3,507 $ 1,491 $ 653 $ 108 $ 1,793 $ 11,170 Energy 5,779 — — — 21 — 5,127 187 11,114 Paycheck Protection Program — — — — — — — — — Commercial real estate: Buildings, land and other 1,116 7,556 — 229 313 2,592 — — 11,806 Construction — — — — — — — — — Consumer real estate — — — — — 380 — 655 1,035 Consumer and other — — — — — — — — — Total $ 6,895 $ 7,654 $ 3,520 $ 3,736 $ 1,825 $ 3,625 $ 5,235 $ 2,635 $ 35,125 Had non-accrual loans performed in accordance with their original contract terms, we would have recognized additional interest income, net of tax, of approximately $436 thousand and $843 thousand for the three and six months ended June 30, 2022, respectively, and approximately $427 thousand and $881 thousand for the three and six months ended June 30, 2021, respectively. An age analysis of past due loans (including both accruing and non-accruing loans), segregated by class of loans, as of June 30, 2022 was as follows: Loans Loans Total Current Total Accruing Commercial and industrial $ 14,529 $ 3,993 $ 18,522 $ 5,520,755 $ 5,539,277 $ 3,280 Energy 200 3,275 3,475 984,450 987,925 — Paycheck Protection Program 5,919 5,063 10,982 80,937 91,919 5,063 Commercial real estate: Buildings, land and other 17,852 7,441 25,293 6,494,987 6,520,280 781 Construction 832 — 832 1,534,976 1,535,808 — Consumer real estate 6,921 1,268 8,189 1,552,846 1,561,035 903 Consumer and other 4,443 598 5,041 494,741 499,782 598 Total $ 50,696 $ 21,638 $ 72,334 $ 16,663,692 $ 16,736,026 $ 10,625 Troubled Debt Restructurings . Troubled debt restructurings during the six months ended June 30, 2022 and 2021 are set forth in the following table. Six Months Ended Six Months Ended Balance at Balance at Balance at Balance at Energy $ — $ — $ 3,817 $ 3,817 Commercial real estate: Buildings, land and other 1,155 1,116 582 579 $ 1,155 $ 1,116 $ 4,399 $ 4,396 Loan modifications are typically related to extending amortization periods, converting loans to interest only for a limited period of time, deferral of interest payments, waiver of certain covenants, consolidating notes and/or reducing collateral or interest rates. The modifications during the reported periods did not significantly impact our determination of the allowance for credit losses on loans. Information as of or for the six months ended June 30, 2022 and 2021 related to loans restructured during the preceding twelve months is set forth in the following table. June 30, 2022 June 30, 2021 Restructured loans past due in excess of 90 days at period-end: Number of loans — 1 Dollar amount of loans $ — $ 1,322 Restructured loans on non-accrual status at period end 1,116 4,090 Charge-offs of restructured loans: Recognized in connection with restructuring — — Recognized on previously restructured loans 723 — Proceeds from sale of restructured loans 1,070 — Credit Quality Indicators. As part of the on-going monitoring of the credit quality of our loan portfolio, management tracks certain credit quality indicators including trends related to (i) the weighted-average risk grade of commercial loans, (ii) the level of classified commercial loans, (iii) the delinquency status of consumer loans, (iv) non-performing loans (see details above) and (v) the general economic conditions in the State of Texas. We utilize a risk grading matrix to assign a risk grade to each of our commercial loans. Loans are graded on a scale of 1 to 14. A description of the general characteristics of the 14 risk grades is set forth in our 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 June 30, 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 $ 1,009,520 $ 805,675 $ 563,122 $ 267,129 $ 142,114 $ 221,192 $ 2,213,761 $ 54,235 $ 5,276,748 6.23 Risk grade 9 12,633 21,474 6,914 9,067 20,961 8,682 79,546 5,662 164,939 9.00 Risk grade 10 5,000 23,293 2,437 705 1,808 255 20,879 2,093 56,470 10.00 Risk grade 11 — 1,651 6,280 9,490 1,556 2,027 4,100 4,846 29,950 11.00 Risk grade 12 — 98 2,569 3,106 1,427 251 108 747 8,306 12.00 Risk grade 13 — — 951 401 64 402 — 1,046 2,864 13.00 $ 1,027,153 $ 852,191 $ 582,273 $ 289,898 $ 167,930 $ 232,809 $ 2,318,394 $ 68,629 $ 5,539,277 6.38 W/A risk grade 6.28 7.03 6.10 6.75 7.01 5.79 6.20 7.52 6.38 Energy Risk grades 1-8 $ 312,271 $ 111,163 $ 6,939 $ 6,332 $ 3,564 $ 5,239 $ 446,460 $ 49,185 $ 941,153 5.57 Risk grade 9 1,660 95 268 1,192 26 — 10,955 39 14,235 9.00 Risk grade 10 — — 73 515 239 — — 58 885 10.00 Risk grade 11 9,097 221 541 4,630 885 164 5,000 — 20,538 11.00 Risk grade 12 3,463 — — — 21 — 2,771 187 6,442 12.00 Risk grade 13 2,316 — — — — — 2,356 — 4,672 13.00 $ 328,807 $ 111,479 $ 7,821 $ 12,669 $ 4,735 $ 5,403 $ 467,542 $ 49,469 $ 987,925 5.82 W/A risk grade 6.09 5.66 7.69 8.63 8.30 7.17 5.46 6.25 5.82 Commercial real estate: Buildings, land, other Risk grades 1-8 $ 1,101,851 $ 1,495,414 $ 999,836 $ 788,421 $ 428,539 $ 963,918 $ 84,964 $ 106,450 $ 5,969,393 6.90 Risk grade 9 64,026 27,271 99,934 47,898 20,773 35,908 7,412 2,848 306,070 9.00 Risk grade 10 5,851 17,824 17,104 52,210 20,353 53,622 3,500 — 170,464 10.00 Risk grade 11 162 434 1,269 7,189 8,969 44,318 206 — 62,547 11.00 Risk grade 12 646 6,545 — 229 313 2,592 — — 10,325 12.00 Risk grade 13 470 1,011 — — — — — — 1,481 13.00 $ 1,173,006 $ 1,548,499 $ 1,118,143 $ 895,947 $ 478,947 $ 1,100,358 $ 96,082 $ 109,298 $ 6,520,280 7.12 W/A risk grade 7.01 7.23 7.16 7.25 7.28 6.95 7.24 6.44 7.12 Construction Risk grades 1-8 $ 276,072 $ 662,364 $ 179,896 $ 100,915 $ 631 $ 1,804 $ 253,781 $ 4,247 $ 1,479,710 6.86 Risk grade 9 11,295 637 2,670 — — 401 — — 15,003 9.00 Risk grade 10 27,992 — — 13,103 — — — — 41,095 10.00 Risk grade 11 — — — — — — — — — 11.00 Risk grade 12 — — — — — — — — — 12.00 Risk grade 13 — — — — — — — — — 13.00 $ 315,359 $ 663,001 $ 182,566 $ 114,018 $ 631 $ 2,205 $ 253,781 $ 4,247 $ 1,535,808 6.96 W/A risk grade 7.10 7.12 6.64 8.21 6.21 7.16 6.10 5.01 6.96 Total commercial real estate $ 1,488,365 $ 2,211,500 $ 1,300,709 $ 1,009,965 $ 479,578 $ 1,102,563 $ 349,863 $ 113,545 $ 8,056,088 7.09 W/A risk grade 7.03 7.19 7.09 7.36 7.28 6.95 6.41 6.39 7.09 In the table above, certain energy and commercial real estate 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 June 30, 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 $ 140 $ 287 $ 387 $ 668 $ 401 $ 2,771 $ 602 $ 1,665 $ 6,921 Past due 90 or more days — — — 4 142 875 247 — 1,268 Total past due 140 287 387 672 543 3,646 849 1,665 8,189 Current loans 154,178 324,089 211,133 80,351 43,828 137,836 592,539 8,892 1,552,846 Total $ 154,318 $ 324,376 $ 211,520 $ 81,023 $ 44,371 $ 141,482 $ 593,388 $ 10,557 $ 1,561,035 Consumer and other: Past due 30-89 days $ 1,974 $ 69 $ 64 $ 44 $ 5 $ 45 $ 32 $ 2,210 $ 4,443 Past due 90 or more days 439 — — 19 11 — — 129 598 Total past due 2,413 69 64 63 16 45 32 2,339 5,041 Current loans 31,230 30,712 10,798 4,166 1,814 2,042 391,713 22,266 494,741 Total $ 33,643 $ 30,781 $ 10,862 $ 4,229 $ 1,830 $ 2,087 $ 391,745 $ 24,605 $ 499,782 Revolving loans that converted to term during the three and six months ended June 30, 2022 and 2021 were as follows: Three Months Ended June 30, Six Months Ended June 30, 2022 2021 2022 2021 Commercial and industrial $ 16,518 $ 22,111 $ 21,973 $ 31,561 Energy 247 294 247 6,177 Commercial real estate: Buildings, land and other 10,681 8,195 10,726 31,321 Construction 13 — 4,248 — Consumer real estate 888 205 1,684 977 Consumer and other 1,792 1,961 5,868 5,696 Total $ 30,139 $ 32,766 $ 44,746 $ 75,732 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 138.4 at June 30, 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 June 30, 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. June 30, 2022 Commercial Energy Commercial Consumer Consumer Total Modeled expected credit losses $ 48,776 $ 6,106 $ 20,093 $ 6,639 $ 9,609 $ 91,223 Q-Factor and other qualitative adjustments 35,134 3,989 95,532 133 2,526 137,314 Specific allocations 3,360 6,172 1,481 82 — 11,095 Total $ 87,270 $ 16,267 $ 117,106 $ 6,854 $ 12,135 $ 239,632 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 and six months ended June 30, 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: June 30, 2022 Beginning balance $ 87,026 $ 15,422 $ 128,954 $ 6,359 $ 9,074 $ 246,835 Credit loss expense (benefit) 942 427 (12,232) 583 5,884 (4,396) Charge-offs (1,891) — — (131) (5,322) (7,344) Recoveries 1,193 418 384 43 2,499 4,537 Net charge-offs (698) 418 384 (88) (2,823) (2,807) Ending balance $ 87,270 $ 16,267 $ 117,106 $ 6,854 $ 12,135 $ 239,632 June 30, 2021 Beginning balance $ 70,892 $ 33,472 $ 144,440 $ 5,636 $ 6,818 $ 261,258 Credit loss expense (benefit) (5,901) (5,527) 3,654 611 2,784 (4,379) Charge-offs (685) — (137) (388) (3,882) (5,092) Recoveries 965 65 36 295 2,140 3,501 Net charge-offs 280 65 (101) (93) (1,742) (1,591) Ending balance $ 65,271 $ 28,010 $ 147,993 $ 6,154 $ 7,860 $ 255,288 Commercial Energy Commercial Consumer Consumer Total Six months ended: June 30, 2022 Beginning balance $ 72,091 $ 17,217 $ 144,936 $ 6,585 $ 7,837 $ 248,666 Credit loss expense (benefit) 18,503 (1,617) (27,841) 557 10,466 68 Charge-offs (5,346) (371) (702) (362) (11,093) (17,874) Recoveries 2,022 1,038 713 74 4,925 8,772 Net (charge-offs) recoveries (3,324) 667 11 (288) (6,168) (9,102) Ending balance $ 87,270 $ 16,267 $ 117,106 $ 6,854 $ 12,135 $ 239,632 June 30, 2021 Beginning balance $ 73,843 $ 39,553 $ 134,892 $ 7,926 $ 6,963 $ 263,177 Credit loss expense (benefit) (7,866) (11,328) 12,576 (2,111) 4,350 (4,379) Charge-offs (2,874) (1,433) (137) (672) (7,942) (13,058) Recoveries 2,168 1,218 662 1,011 4,489 9,548 Net (charge-offs) recoveries (706) (215) 525 339 (3,453) (3,510) Ending balance $ 65,271 $ 28,010 $ 147,993 $ 6,154 $ 7,860 $ 255,288 The following table presents loans that were evaluated for expected credit losses on an individual basis and the related specific allocations, by loan portfolio segment, as of June 30, 2022 and December 31, 2021. June 30, 2022 December 31, 2021 Loan Specific Allocations Loan Specific Allocations Commercial and industrial $ 12,539 $ 3,360 $ 24,523 $ 10,536 Energy 15,906 6,172 16,393 5,480 Paycheck Protection Program — — — — Commercial real estate: Buildings, land and other 21,205 1,481 24,670 200 Construction — — 948 200 Consumer real estate 934 82 303 36 Consumer and other — — — — Total $ 50,584 $ 11,095 $ 66,837 $ 16,452

Goodwill and Other Intangible A

Goodwill and Other Intangible Assets	6 Months Ended
	Jun. 30, 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. June 30, December 31, Goodwill $ 654,952 $ 654,952 Other intangible assets: Core deposits $ 479 $ 718 Customer relationships 110 148 $ 589 $ 866 The estimated aggregate future amortization expense for intangible assets remaining as of June 30, 2022 is as follows: Remainder of 2022 $ 204 2023 282 2024 87 2025 11 2026 5 $ 589

Deposits

Deposits	6 Months Ended
	Jun. 30, 2022
Disclosure Text Block [Abstract]
Deposits	Deposits Deposits were as follows: June 30, December 31, Non-interest-bearing demand deposits $ 18,783,931 $ 18,423,018 Interest-bearing deposits: Savings and interest checking 12,309,066 11,930,959 Money market accounts 12,989,902 11,228,815 Time accounts 1,518,866 1,112,904 Total interest-bearing deposits 26,817,834 24,272,678 Total deposits $ 45,601,765 $ 42,695,696 The following table presents additional information about our deposits: June 30, December 31, Deposits from foreign sources (primarily Mexico) $ 1,090,169 $ 993,479 Non-interest-bearing public funds deposits 681,205 1,235,026 Interest-bearing public funds deposits 837,427 810,863 Total deposits not covered by deposit insurance 25,810,407 24,125,359 Time deposits not covered by deposit insurance 364,486 238,608

Commitments and Contingencies

Commitments and Contingencies	6 Months Ended
	Jun. 30, 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: June 30, December 31, Commitments to extend credit $ 10,771,940 $ 10,420,142 Standby letters of credit 327,847 238,690 Deferred standby letter of credit fees 1,890 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 Six Months Ended 2022 2021 2022 2021 Beginning balance $ 45,850 $ 44,217 $ 50,314 $ 44,152 Credit loss expense (benefit) 4,396 4,379 (68) 4,444 Ending balance $ 50,246 $ 48,596 $ 50,246 $ 48,596 Lease Commitments . We lease certain office facilities and office equipment under operating leases. The components of total lease expense were as follows: Three Months Ended Six Months Ended 2022 2021 2022 2021 Amortization of lease right-of-use assets $ 8,209 $ 8,129 $ 16,314 $ 16,412 Short-term lease expense 490 530 1,103 734 Non-lease components (including taxes, insurance, common maintenance, etc.) 2,748 2,337 5,768 5,341 Total $ 11,447 $ 10,996 $ 23,185 $ 22,487 Right-of-use lease assets totaled $278.3 million at June 30, 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 $310.5 million at June 30, 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 $8.4 million and $16.4 million during the three and six months ended June 30, 2022, respectively, and $8.0 million and $16.1 million during the three and six months ended June 30, 2021, respectively. 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	6 Months Ended
	Jun. 30, 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 June 30, 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 June 30, 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 June 30, 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 June 30, 2022 and $100.0 million at December 31, 2021 and trust preferred securities totaling $120.0 million at both June 30, 2022 and December 31, 2021. The following table presents actual and required capital ratios as of June 30, 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 June 30, 2022 Common Equity Tier 1 to Risk-Weighted Assets Cullen/Frost $ 3,485,759 12.64 % $ 1,930,703 7.00 % $ 1,792,796 6.50 % Frost Bank 3,423,585 12.42 1,929,368 7.00 1,791,556 6.50 Tier 1 Capital to Risk-Weighted Assets Cullen/Frost 3,631,211 13.17 2,344,425 8.50 2,206,518 8.00 Frost Bank 3,423,585 12.42 2,342,804 8.50 2,204,992 8.00 Total Capital to Risk-Weighted Assets Cullen/Frost 4,069,206 14.75 2,896,055 10.50 2,758,148 10.00 Frost Bank 3,661,580 13.28 2,894,052 10.50 2,756,240 10.00 Leverage Ratio Cullen/Frost 3,631,211 7.03 2,067,513 4.00 2,584,391 5.00 Frost Bank 3,423,585 6.62 2,067,942 4.00 2,584,928 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 June 30, 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 June 30, 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 June 30, 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 through private transactions. No shares have been repurchased under this plan or the prior plan during the reported periods. Under the Basel III Capital Rules, Cullen/Frost may not repurchase or redeem any of its preferred stock or subordinated notes and, in some cases, its common stock without the prior approval of the Federal Reserve Board. Dividend Restrictions . In the ordinary course of business, Cullen/Frost is dependent upon dividends from Frost Bank to provide funds for the payment of dividends to shareholders and to provide for other cash requirements, including to repurchase its common stock. Banking regulations may limit the amount of dividends that may be paid. Approval by regulatory authorities is required if the effect of dividends declared would cause the regulatory capital of Frost Bank to fall below specified minimum levels. Approval is also required if dividends declared exceed the net profits for that year combined with the retained net profits for the preceding two years. Under the foregoing dividend restrictions and while maintaining its “well capitalized” status, at June 30, 2022, Frost Bank could pay aggregate dividends of up to $447.3 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	6 Months Ended
	Jun. 30, 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 June 30, 2022 and December 31, 2021. June 30, 2022 December 31, 2021 Notional Estimated Notional Estimated Derivatives designated as hedges of fair value: Financial institution counterparties: Loan/lease interest rate swaps – assets $ 1,743 $ 18 $ — $ — Loan/lease interest rate swaps – liabilities — — 2,426 (34) Non-hedging interest rate derivatives: Financial institution counterparties: Loan/lease interest rate swaps – assets 904,706 27,908 247,592 1,207 Loan/lease interest rate swaps – liabilities 244,663 (2,489) 928,756 (19,142) Loan/lease interest rate caps – assets 269,389 10,209 270,431 3,239 Customer counterparties: Loan/lease interest rate swaps – assets 244,663 3,350 928,756 39,864 Loan/lease interest rate swaps – liabilities 904,706 (45,542) 247,592 (2,846) Loan/lease interest rate caps – liabilities 269,389 (10,209) 270,431 (3,239) The weighted-average rates paid and received for interest rate swaps outstanding at June 30, 2022 were as follows: Weighted-Average Interest Interest Interest rate swaps: Fair value hedge loan/lease interest rate swaps 1.58 % 1.06 % Non-hedging interest rate swaps – financial institution counterparties 3.71 2.87 Non-hedging interest rate swaps – customer counterparties 2.87 3.71 The weighted-average strike rate for outstanding interest rate caps was 3.28% at June 30, 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. June 30, 2022 December 31, 2021 Notional Notional Estimated Notional Estimated Financial institution counterparties: Oil – assets Barrels 4,173 $ 20,653 4,809 $ 14,721 Oil – liabilities Barrels 9,125 (181,161) 7,032 (73,594) Natural gas – assets MMBTUs 11,753 3,181 15,947 4,143 Natural gas – liabilities MMBTUs 21,557 (38,990) 29,446 (21,249) Customer counterparties: Oil – assets Barrels 9,606 182,274 7,046 74,437 Oil – liabilities Barrels 3,692 (20,306) 4,796 (14,294) Natural gas – assets MMBTUs 21,557 39,110 29,446 21,456 Natural gas – liabilities MMBTUs 11,753 (3,181) 15,947 (4,124) Foreign Currency Derivatives . We enter into foreign currency forward and option contracts that are not designated as hedging instruments primarily to accommodate the business needs of our customers. Upon the origination of a foreign currency denominated transaction with a customer, we simultaneously enter into an offsetting contract with a third party financial institution to negate the exposure to fluctuations in foreign currency exchange rates. We also utilize foreign currency forward contracts and options that are not designated as hedging instruments to mitigate the economic effect of fluctuations in foreign currency exchange rates on foreign currency holdings and certain short-term, non-U.S. dollar denominated loans. The notional amounts and fair values of open foreign currency forward and option contracts were as follows: June 30, 2022 December 31, 2021 Notional Notional Estimated Notional Estimated Financial institution counterparties: Forward and option contracts – assets EUR 6,400 $ 16 1,900 $ 29 Forward and option contracts – assets CAD 658 9 658 — Forward and option contracts – liabilities EUR 6,400 (174) — — Customer counterparties: Forward and option contracts – assets EUR 6,400 174 — — Forward and option contracts – assets CAD — — 658 4 Forward and option contracts – liabilities EUR 6,400 (16) 1,900 (55) Forward and option contracts – liabilities CAD 658 (5) — — Gains, Losses and Derivative Cash Flows . For fair value hedges, the changes in the fair value of both the derivative hedging instrument and the hedged item are included in other non-interest income or other non-interest expense. The extent that such changes in fair value do not offset represents hedge ineffectiveness. Net cash flows from interest rate swaps on commercial loans/leases designated as hedging instruments in effective hedges of fair value are included in interest income on loans. For non-hedging derivative instruments, gains and losses due to changes in fair value and all cash flows are included in other non-interest income and other non-interest expense. Amounts included in the consolidated statements of income related to interest rate derivatives designated as hedges of fair value were as follows: Three Months Ended Six Months Ended 2022 2021 2022 2021 Commercial loan/lease interest rate swaps: Amount of gain (loss) included in interest income on loans $ (5) $ (25) $ (18) $ (53) Amount of (gain) loss included in other non-interest expense 3 2 5 5 As stated above, we enter into non-hedge related derivative positions primarily to accommodate the business needs of our customers. Upon the origination of a derivative contract with a customer, we simultaneously enter into an offsetting derivative contract with a third party financial institution. We recognize immediate income based upon the difference in the bid/ask spread of the underlying transactions with our customers and the third party. Because we act only as an intermediary for our customer, subsequent changes in the fair value of the underlying derivative contracts for the most part offset each other and do not significantly impact our results of operations. Amounts included in the consolidated statements of income related to non-hedge related derivative instruments are presented in the table below. Three Months Ended Six Months Ended 2022 2021 2022 2021 Non-hedging interest rate derivatives: Other non-interest income $ 515 $ 141 $ 1,031 $ 1,728 Other non-interest expense — — — (1) Non-hedging commodity derivatives: Other non-interest income 649 969 1,578 2,123 Non-hedging foreign currency derivatives: Other non-interest income 45 — 63 30 Counterparty Credit Risk. Our credit exposure relating to interest rate swaps, commodity swaps/options and foreign currency forward and option contracts with bank customers was approximately $198.1 million at June 30, 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/option contracts with upstream financial institution counterparties was approximately $41.5 million at June 30, 2022. This amount was primarily related to initial margin payments to the CME and excess collateral we posted to counterparties. Excess collateral is generally cleared on the next business day. Collateral levels for upstream financial institution counterparties are monitored and adjusted as necessary. See Note 9 – Balance Sheet Offsetting and Repurchase Agreements for additional information regarding our credit exposure with upstream financial institution counterparties. At June 30, 2022, we had $212.4 million in cash collateral related to derivative contracts on deposit with other financial institution counterparties.

Balance Sheet Offsetting

Balance Sheet Offsetting	6 Months Ended
	Jun. 30, 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 June 30, 2022 is presented in the following tables. Gross Amount Gross Amount Net Amount June 30, 2022 Financial assets: Derivatives: Loan/lease interest rate swaps and caps $ 38,135 $ — $ 38,135 Commodity swaps and options 23,834 — 23,834 Foreign currency forward contracts 25 — 25 Total derivatives 61,994 — 61,994 Resell agreements 9,650 — 9,650 Total $ 71,644 $ — $ 71,644 Financial liabilities: Derivatives: Loan/lease interest rate swaps and caps $ 2,489 $ — $ 2,489 Commodity swaps and options 220,151 — 220,151 Foreign currency forward contracts 174 — 174 Total derivatives 222,814 — 222,814 Repurchase agreements 1,664,685 — 1,664,685 Total $ 1,887,499 $ — $ 1,887,499 Gross Amounts Not Offset Net Amount Financial Collateral Net June 30, 2022 Financial assets: Derivatives: Counterparty A $ 41 $ (41) $ — $ — Counterparty B 25,962 (25,962) — — Counterparty C 16 (16) — — Other counterparties 35,975 (25,533) (10,442) — Total derivatives 61,994 (51,552) (10,442) — Resell agreements 9,650 — (9,650) — Total $ 71,644 $ (51,552) $ (20,092) $ — Financial liabilities: Derivatives: Counterparty A $ 1,726 $ (41) $ (1,571) $ 114 Counterparty B 50,901 (25,962) (24,939) — Counterparty C 174 (16) (10) 148 Other counterparties 170,013 (25,533) (144,463) 17 Total derivatives 222,814 (51,552) (170,983) 279 Repurchase agreements 1,664,685 — (1,664,685) — Total $ 1,887,499 $ (51,552) $ (1,835,668) $ 279 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 June 30, 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 June 30, 2022 Repurchase agreements: U.S. Treasury $ 834,063 $ — $ — $ — $ 834,063 Residential mortgage-backed securities 830,622 — — — 830,622 Total borrowings $ 1,664,685 $ — $ — $ — $ 1,664,685 Gross amount of recognized liabilities for repurchase agreements $ 1,664,685 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	6 Months Ended
	Jun. 30, 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 June 30, 2022, there were 788,070 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 5,382 133.67 3,460 132.72 — — — — Exercised/vested (16,022) 74.89 — — (25,180) 87.18 (103,060) 62.97 Forfeited/expired — — (3,167) 94.57 (16,058) 87.18 — — Balance, June 30, 2022 45,661 87.15 449,630 93.35 161,222 84.08 774,621 69.83 Shares issued in connection with stock compensation awards are issued from available treasury shares. If no treasury shares are available, new shares are issued from available authorized shares. Shares issued in connection with stock compensation awards along with other related information were as follows: Three Months Ended Six Months Ended 2022 2021 2022 2021 New shares issued from available authorized shares — — — — Shares issued from available treasury stock 28,832 114,252 144,262 628,076 Proceeds from stock option exercises $ 751 $ 7,285 $ 6,490 $ 36,682 Stock-based compensation expense is recognized ratably over the requisite service period for all awards. For most stock option awards, the service period generally matches the vesting period. For stock options granted to certain executive officers and for non-vested stock units granted to all participants, the service period does not extend past the date the participant reaches 65 years of age. Deferred stock units granted to non-employee directors generally have immediate vesting and the related expense is fully recognized on the date of grant. For performance stock units, the service period generally matches the three-year performance period specified by the award, however, the service period does not extend past the date the participant reaches 65 years of age. Expense recognized each period is dependent upon our estimate of the number of shares that will ultimately be issued. Stock-based compensation expense or benefit and the related income tax benefit is presented in the following table. The service period for performance stock units granted each year begins on January 1 of the following year. Three Months Ended Six Months Ended 2022 2021 2022 2021 Non-vested stock units $ 2,291 $ 1,768 $ 4,649 $ 3,651 Deferred stock units 720 700 720 700 Performance stock units 407 777 161 1,420 Total $ 3,418 $ 3,245 $ 5,530 $ 5,771 Income tax benefit $ 612 $ 514 $ 1,320 $ 881 Unrecognized stock-based compensation expense at June 30, 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 $ 13,954 Performance stock units 8,256 Total $ 22,210

Earnings Per Common Share

Earnings Per Common Share	6 Months Ended
	Jun. 30, 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 Six Months Ended 2022 2021 2022 2021 Net income $ 119,114 $ 118,068 $ 218,216 $ 234,083 Less: Preferred stock dividends 1,669 1,669 3,338 3,820 Net income available to common shareholders 117,445 116,399 214,878 230,263 Less: Earnings allocated to participating securities 1,036 1,141 1,888 2,307 Net earnings allocated to common stock $ 116,409 $ 115,258 $ 212,990 $ 227,956 Distributed earnings allocated to common stock $ 48,092 $ 45,824 $ 96,143 $ 91,484 Undistributed earnings allocated to common stock 68,317 69,434 116,847 136,472 Net earnings allocated to common stock $ 116,409 $ 115,258 $ 212,990 $ 227,956 Weighted-average shares outstanding for basic earnings per common share 64,112,828 63,606,340 64,082,185 63,457,245 Dilutive effect of stock compensation 354,401 495,819 382,395 511,288 Weighted-average shares outstanding for diluted earnings per common share 64,467,229 64,102,159 64,464,580 63,968,533

Defined Benefit Plans

Defined Benefit Plans	6 Months Ended
	Jun. 30, 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 Six Months Ended 2022 2021 2022 2021 Expected return on plan assets, net of expenses $ (3,492) $ (3,210) $ (6,983) $ (6,420) Interest cost on projected benefit obligation 1,004 836 2,008 1,671 Net amortization and deferral 741 1,529 1,482 3,058 Net periodic expense (benefit) $ (1,747) $ (845) $ (3,493) $ (1,691) Our non-qualified defined benefit pension plan is not funded. No contributions to the qualified defined benefit pension plan were made during the six months ended June 30, 2022. We do not expect to make any contributions to the qualified defined benefit plan during the remainder of 2022.

Income Taxes

Income Taxes	6 Months Ended
	Jun. 30, 2022
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes Income tax expense was as follows: Three Months Ended Six Months Ended 2022 2021 2022 2021 Current income tax expense (benefit) $ 22,646 $ 14,065 $ 35,705 $ 17,790 Deferred income tax expense (benefit) (1,972) 1,016 (2,404) 5,188 Income tax expense, as reported $ 20,674 $ 15,081 $ 33,301 $ 22,978 Effective tax rate 14.8 % 11.3 % 13.2 % 8.9 % We had a net deferred tax asset totaling $245.9 million at June 30, 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 June 30, 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)	6 Months Ended
	Jun. 30, 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 $ (636,523) $ (133,670) $ (502,853) $ 30,668 $ 6,441 $ 24,227 Change in net unrealized gain on securities transferred to held to maturity (189) (40) (149) (245) (52) (193) Reclassification adjustment for net (gains) losses included in net income — — — — — — Total securities available for sale and transferred securities (636,712) (133,710) (503,002) 30,423 6,389 24,034 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) 741 155 586 1,529 321 1,208 Total defined-benefit post-retirement benefit plans 741 155 586 1,529 321 1,208 Total other comprehensive income (loss) $ (635,971) $ (133,555) $ (502,416) $ 31,952 $ 6,710 $ 25,242 Six Months Ended Six Months Ended Before Tax Tax Expense, Net of Tax Before Tax Tax Expense, Net of Tax Securities available for sale and transferred securities: Change in net unrealized gain/loss during the period $ (1,547,318) $ (324,937) $ (1,222,381) $ (129,111) $ (27,113) $ (101,998) Change in net unrealized gain on securities transferred to held to maturity (398) (84) (314) (504) (106) (398) Reclassification adjustment for net (gains) losses included in net income — — — — — — Total securities available for sale and transferred securities (1,547,716) (325,021) (1,222,695) (129,615) (27,219) (102,396) 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) 1,482 311 1,171 3,058 642 2,416 Total defined-benefit post-retirement benefit plans 1,482 311 1,171 3,058 642 2,416 Total other comprehensive income (loss) $ (1,546,234) $ (324,710) $ (1,221,524) $ (126,557) $ (26,577) $ (99,980) 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 (1,222,695) — (1,222,695) Reclassification of amounts included in net income — 1,171 1,171 Net other comprehensive income (loss) during period (1,222,695) 1,171 (1,221,524) Balance at June 30, 2022 $ (842,486) $ (31,720) $ (874,206) Balance January 1, 2021 $ 563,801 $ (50,831) $ 512,970 Other comprehensive income (loss) before reclassifications (102,396) — (102,396) Reclassification of amounts included in net income — 2,416 2,416 Net other comprehensive income (loss) during period (102,396) 2,416 (99,980) Balance at June 30, 2021 $ 461,405 $ (48,415) $ 412,990

Operating Segments

Operating Segments	6 Months Ended
	Jun. 30, 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: June 30, 2022 Net interest income (expense) $ 289,186 $ 958 $ (1,936) $ 288,208 Credit loss expense 1 (1) — — Non-interest income 55,397 43,054 (524) 97,927 Non-interest expense 211,044 33,158 2,145 246,347 Income (loss) before income taxes 133,538 10,855 (4,605) 139,788 Income tax expense (benefit) 19,821 2,279 (1,426) 20,674 Net income (loss) 113,717 8,576 (3,179) 119,114 Preferred stock dividends — — 1,669 1,669 Net income (loss) available to common shareholders $ 113,717 $ 8,576 $ (4,848) $ 117,445 Revenues from (expenses to) external customers $ 344,583 $ 44,012 $ (2,460) $ 386,135 June 30, 2021 Net interest income (expense) $ 258,450 $ 508 $ (1,802) $ 257,156 Credit loss expense (benefit) — — — — Non-interest income 48,944 42,534 (231) 91,247 Non-interest expense 183,109 30,014 2,131 215,254 Income (loss) before income taxes 124,285 13,028 (4,164) 133,149 Income tax expense (benefit) 13,605 2,736 (1,260) 15,081 Net income (loss) 110,680 10,292 (2,904) 118,068 Preferred stock dividends — — 1,669 1,669 Net income (loss) available to common shareholders $ 110,680 $ 10,292 $ (4,573) $ 116,399 Revenues from (expenses to) external customers $ 307,394 $ 43,042 $ (2,033) $ 348,403 Six months ended: June 30, 2022 Net interest income (expense) $ 539,305 $ 1,658 $ (3,684) $ 537,279 Credit loss expense (benefit) — — — — Non-interest income 114,103 86,283 (1,069) 199,317 Non-interest expense 417,582 64,068 3,429 485,079 Income (loss) before income taxes 235,826 23,873 (8,182) 251,517 Income tax expense (benefit) 30,835 5,013 (2,547) 33,301 Net income (loss) 204,991 18,860 (5,635) 218,216 Preferred stock dividends — — 3,338 3,338 Net income (loss) available to common shareholders $ 204,991 $ 18,860 $ (8,973) $ 214,878 Revenues from (expenses to) external customers $ 653,408 $ 87,941 $ (4,753) $ 736,596 June 30, 2021 Net interest income (expense) $ 500,655 $ 994 $ (3,612) $ 498,037 Credit loss expense 63 — — 63 Non-interest income 102,724 82,143 (384) 184,483 Non-interest expense 362,260 59,951 3,185 425,396 Income (loss) before income taxes 241,056 23,186 (7,181) 257,061 Income tax expense (benefit) 20,782 4,869 (2,673) 22,978 Net income (loss) 220,274 18,317 (4,508) 234,083 Preferred stock dividends — — 3,820 3,820 Net income (loss) available to common shareholders $ 220,274 $ 18,317 $ (8,328) $ 230,263 Revenues from (expenses to) external customers $ 603,379 $ 83,137 $ (3,996) $ 682,520

Fair Value Measurements

Fair Value Measurements	6 Months Ended
	Jun. 30, 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 June 30, 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 June 30, 2022 Securities available for sale: U.S. Treasury $ 4,416,299 $ — $ — $ 4,416,299 Residential mortgage-backed securities — 5,335,725 — 5,335,725 States and political subdivisions — 6,987,296 — 6,987,296 Other — 42,365 — 42,365 Trading account securities: U.S. Treasury 24,615 — — 24,615 States and political subdivisions — 65 — 65 Derivative assets: Interest rate swaps, caps and floors — 41,485 — 41,485 Commodity swaps and options — 245,218 — 245,218 Foreign currency forward contracts 199 — — 199 Derivative liabilities: Interest rate swaps, caps and floors — 58,240 — 58,240 Commodity swaps and options — 243,638 — 243,638 Foreign currency forward contracts 195 — — 195 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. Six Months Ended Six Months Ended Level 2 Level 3 Level 2 Level 3 Carrying value before allocations $ 5,454 $ 3,614 $ 3,399 $ 19,423 Specific (allocations) reversals of prior allocations (1,327) 6,877 (336) (3,273) Fair value $ 4,127 $ 10,491 $ 3,063 $ 16,150 Non-Financial Assets and Non-Financial Liabilities. We do not have any non-financial assets or non-financial liabilities measured at fair value on a recurring basis. From time to time, non-financial assets measured at fair value on a non-recurring basis may include certain foreclosed assets which, upon initial recognition, were remeasured and reported at fair value through a charge-off to the allowance for loan losses and certain foreclosed assets which, subsequent to their initial recognition, were remeasured at fair value through a write-down included in other non-interest expense. There were no such fair value measurements during the reported periods. Financial Instruments Reported at Amortized Cost. The estimated fair values of financial instruments that are reported at amortized cost in our consolidated balance sheets, segregated by the level of the valuation inputs within the fair value hierarchy utilized to measure fair value, were as follows: June 30, 2022 December 31, 2021 Carrying Estimated Carrying Estimated Financial assets: Level 2 inputs: Cash and cash equivalents $ 13,658,585 $ 13,658,585 $ 16,583,000 $ 16,583,000 Securities held to maturity 1,946,428 1,828,515 1,749,179 1,809,143 Cash surrender value of life insurance policies 189,823 189,823 190,139 190,139 Accrued interest receivable 194,049 194,049 179,111 179,111 Level 3 inputs: Loans, net 16,496,394 16,126,497 16,087,731 16,079,454 Financial liabilities: Level 2 inputs: Deposits 45,601,765 45,584,113 42,695,696 41,343,426 Federal funds purchased 43,200 43,200 25,925 25,925 Repurchase agreements 1,664,685 1,664,685 2,740,799 2,740,799 Junior subordinated deferrable interest debentures 123,040 123,712 123,011 123,712 Subordinated notes 99,256 99,626 99,178 111,430 Accrued interest payable 6,059 6,059 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	6 Months Ended
	Jun. 30, 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. ASU 2022-03, “Fair Value Measurement (Topic 820): Fair Value Measurement of Equity Securities Subject to Contractual Sale Restrictions.” ASU 2022-03 clarifies that a contractual restriction on the sale of an equity security is not considered part of the unit of account of the equity security and, therefore, is not considered in measuring fair value. ASU 2022-03 also clarifies that an entity cannot, as a separate unit of account, recognize and measure a contractual sale restriction and requires certain new disclosures for equity securities subject to contractual sale restrictions. ASU 2022-03 will be effective for us on January 1, 2024 though early adoption is permitted. The adoption of ASU 2022-03 is not expected to have a significant impact on our financial statements.

Significant Accounting Polici_2

Significant Accounting Policies (Policies)	6 Months Ended
	Jun. 30, 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)	6 Months Ended
	Jun. 30, 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)	6 Months Ended
	Jun. 30, 2022
Accounting Policies [Abstract]
Additional Cash Flow Information	Additional cash flow information was as follows: Six Months Ended 2022 2021 Cash paid for interest $ 22,551 $ 15,936 Cash paid for income taxes 45,500 15,400 Significant non-cash transactions: Unsettled securities transactions 110,623 358,752 Loans foreclosed and transferred to other real estate owned and foreclosed assets — 3,251 Right-of-use lease assets obtained in exchange for lessee operating lease liabilities 8,857 1,552 Treasury stock issued to 401(k) stock purchase plan — 1,749

Securities (Tables)

Securities (Tables)	6 Months Ended
	Jun. 30, 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 June 30, 2022 and December 31, 2021 is presented below. Amortized Gross Gross Estimated Allowance Net June 30, 2022 Residential mortgage-backed securities $ 526,675 $ — $ 40,383 $ 486,292 $ — $ 526,675 States and political subdivisions 1,418,411 3,956 81,583 1,340,784 (158) 1,418,253 Other 1,500 — 61 1,439 — 1,500 Total $ 1,946,586 $ 3,956 $ 122,027 $ 1,828,515 $ (158) $ 1,946,428 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 June 30, 2022 and December 31, 2021: States and Political Subdivisions Not Guaranteed or Pre-Refunded Guaranteed by the Texas PSF Pre-Refunded Total Other June 30, 2022 Aaa/AAA $ 161,274 $ 764,405 $ 344,335 $ 1,270,014 $ — Aa/AA 148,397 — — 148,397 — Not rated — — — — 1,500 Total $ 309,671 $ 764,405 $ 344,335 $ 1,418,411 $ 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 and six months ended June 30, 2022 and 2021. Three Months Ended Six Months Ended 2022 2021 2022 2021 Beginning balance $ 158 $ 158 $ 158 $ 160 Credit loss expense (benefit) — — — (2) Ending balance $ 158 $ 158 $ 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 June 30, 2022 and December 31, 2021 is presented below. Amortized Gross Gross Allowance Estimated June 30, 2022 U.S. Treasury $ 4,656,896 $ 2,093 $ 242,690 $ — $ 4,416,299 Residential mortgage-backed securities 5,967,803 3,443 635,521 — 5,335,725 States and political subdivisions 7,183,199 50,465 246,368 — 6,987,296 Other 42,365 — — — 42,365 Total $ 17,850,263 $ 56,001 $ 1,124,579 $ — $ 16,781,685 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 June 30, 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 $ 4,224,018 $ 242,690 $ — $ — $ 4,224,018 $ 242,690 Residential mortgage-backed securities 4,825,871 568,405 369,098 67,116 5,194,969 635,521 States and political subdivisions 3,249,625 241,884 13,824 4,484 3,263,449 246,368 Total $ 12,299,514 $ 1,052,979 $ 382,922 $ 71,600 $ 12,682,436 $ 1,124,579
Amortized Cost and Estimated Fair Value of Securities, Excluding Trading Securities, Presented by Contractual Maturity	The following table summarizes the maturity distribution schedule of securities held to maturity and securities available for sale as of June 30, 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 $ 3 $ — $ 514,582 $ 12,090 $ 526,675 States and political subdivisions 350,365 84,053 22,102 961,891 1,418,411 Other — 1,500 — — 1,500 Total $ 350,368 $ 85,553 $ 536,684 $ 973,981 $ 1,946,586 Estimated Fair Value Residential mortgage-backed securities $ 3 $ — $ 475,721 $ 10,568 $ 486,292 States and political subdivisions 351,237 84,787 22,166 882,594 1,340,784 Other — 1,439 — — 1,439 Total $ 351,240 $ 86,226 $ 497,887 $ 893,162 $ 1,828,515 Available For Sale Amortized Cost U. S. Treasury $ — $ 3,031,706 $ 1,433,320 $ 191,870 $ 4,656,896 Residential mortgage-backed securities 55 11,080 18,743 5,937,925 5,967,803 States and political subdivisions 207,078 1,546,995 902,953 4,526,173 7,183,199 Other — — — — 42,365 Total $ 207,133 $ 4,589,781 $ 2,355,016 $ 10,655,968 $ 17,850,263 Estimated Fair Value U. S. Treasury $ — $ 2,957,018 $ 1,301,539 $ 157,742 $ 4,416,299 Residential mortgage-backed securities 55 11,231 18,792 5,305,647 5,335,725 States and political subdivisions 209,138 1,579,097 893,132 4,305,929 6,987,296 Other — — — — 42,365 Total $ 209,193 $ 4,547,346 $ 2,213,463 $ 9,769,318 $ 16,781,685
Investment Income	Premium amortization and discount accretion included in interest income on securities was as follows: Three Months Ended Six Months Ended 2022 2021 2022 2021 Premium amortization $ (28,053) $ (30,541) $ (57,113) $ (61,776) Discount accretion 2,482 705 3,888 1,342 Net (premium amortization) discount accretion $ (25,571) $ (29,836) $ (53,225) $ (60,434)
Trading Account Securities, at Estimated Fair Value	Trading account securities, at estimated fair value, were as follows: June 30, December 31, U.S. Treasury $ 24,615 $ 24,237 States and political subdivisions 65 925 Total $ 24,680 $ 25,162
Net Gains and Losses on Trading Account Securities	Net gains and losses on trading account securities were as follows: Three Months Ended Six Months Ended 2022 2021 2022 2021 Net gain on sales transactions $ 1,012 $ 293 $ 1,352 $ 402 Net mark-to-market gains (losses) (76) — (244) (69) Net gain (loss) on trading account securities $ 936 $ 293 $ 1,108 $ 333

Loans (Tables)

Loans (Tables)	6 Months Ended
	Jun. 30, 2022
Receivables [Abstract]
Loans	Loans were as follows: June 30, December 31, Commercial and industrial $ 5,539,277 $ 5,364,954 Energy: Production 762,625 878,436 Service 121,356 105,901 Other 103,944 93,455 Total energy 987,925 1,077,792 Paycheck Protection Program 91,919 428,882 Commercial real estate: Commercial mortgages 6,041,606 5,867,062 Construction 1,535,808 1,304,271 Land 478,674 405,277 Total commercial real estate 8,056,088 7,576,610 Consumer real estate: Home equity loans 352,633 324,157 Home equity lines of credit 603,907 519,098 Other 604,495 567,535 Total consumer real estate 1,561,035 1,410,790 Total real estate 9,617,123 8,987,400 Consumer and other 499,782 477,369 Total loans $ 16,736,026 $ 16,336,397
Non-Accrual Loans, Segregated by Class of Loans	Non-accrual loans, segregated by class of loans, were as follows: June 30, 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 $ 11,170 $ 3,093 $ 22,582 $ 4,701 Energy 11,114 6,442 14,433 8,533 Paycheck Protection Program — — — — Commercial real estate: Buildings, land and other 11,806 6,419 15,297 13,817 Construction — — 948 — Consumer real estate 1,035 732 440 138 Consumer and other — — 13 13 Total $ 35,125 $ 16,686 $ 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 June 30, 2022 by class and year of origination. 2022 2021 2020 2019 2018 Prior Revolving Loans Revolving Loans Converted to Term Total Commercial and industrial $ — $ 98 $ 3,520 $ 3,507 $ 1,491 $ 653 $ 108 $ 1,793 $ 11,170 Energy 5,779 — — — 21 — 5,127 187 11,114 Paycheck Protection Program — — — — — — — — — Commercial real estate: Buildings, land and other 1,116 7,556 — 229 313 2,592 — — 11,806 Construction — — — — — — — — — Consumer real estate — — — — — 380 — 655 1,035 Consumer and other — — — — — — — — — Total $ 6,895 $ 7,654 $ 3,520 $ 3,736 $ 1,825 $ 3,625 $ 5,235 $ 2,635 $ 35,125
Age Analysis of Past Due Loans, Segregated by Class of Loans	An age analysis of past due loans (including both accruing and non-accruing loans), segregated by class of loans, as of June 30, 2022 was as follows: Loans Loans Total Current Total Accruing Commercial and industrial $ 14,529 $ 3,993 $ 18,522 $ 5,520,755 $ 5,539,277 $ 3,280 Energy 200 3,275 3,475 984,450 987,925 — Paycheck Protection Program 5,919 5,063 10,982 80,937 91,919 5,063 Commercial real estate: Buildings, land and other 17,852 7,441 25,293 6,494,987 6,520,280 781 Construction 832 — 832 1,534,976 1,535,808 — Consumer real estate 6,921 1,268 8,189 1,552,846 1,561,035 903 Consumer and other 4,443 598 5,041 494,741 499,782 598 Total $ 50,696 $ 21,638 $ 72,334 $ 16,663,692 $ 16,736,026 $ 10,625
Troubled debt restructurings	Troubled debt restructurings during the six months ended June 30, 2022 and 2021 are set forth in the following table. Six Months Ended Six Months Ended Balance at Balance at Balance at Balance at Energy $ — $ — $ 3,817 $ 3,817 Commercial real estate: Buildings, land and other 1,155 1,116 582 579 $ 1,155 $ 1,116 $ 4,399 $ 4,396
Restructured Loans Past Due in Excess of 90 Days on Financing Receivables	Information as of or for the six months ended June 30, 2022 and 2021 related to loans restructured during the preceding twelve months is set forth in the following table. June 30, 2022 June 30, 2021 Restructured loans past due in excess of 90 days at period-end: Number of loans — 1 Dollar amount of loans $ — $ 1,322 Restructured loans on non-accrual status at period end 1,116 4,090 Charge-offs of restructured loans: Recognized in connection with restructuring — — Recognized on previously restructured loans 723 — Proceeds from sale of restructured loans 1,070 —
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 June 30, 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 $ 1,009,520 $ 805,675 $ 563,122 $ 267,129 $ 142,114 $ 221,192 $ 2,213,761 $ 54,235 $ 5,276,748 6.23 Risk grade 9 12,633 21,474 6,914 9,067 20,961 8,682 79,546 5,662 164,939 9.00 Risk grade 10 5,000 23,293 2,437 705 1,808 255 20,879 2,093 56,470 10.00 Risk grade 11 — 1,651 6,280 9,490 1,556 2,027 4,100 4,846 29,950 11.00 Risk grade 12 — 98 2,569 3,106 1,427 251 108 747 8,306 12.00 Risk grade 13 — — 951 401 64 402 — 1,046 2,864 13.00 $ 1,027,153 $ 852,191 $ 582,273 $ 289,898 $ 167,930 $ 232,809 $ 2,318,394 $ 68,629 $ 5,539,277 6.38 W/A risk grade 6.28 7.03 6.10 6.75 7.01 5.79 6.20 7.52 6.38 Energy Risk grades 1-8 $ 312,271 $ 111,163 $ 6,939 $ 6,332 $ 3,564 $ 5,239 $ 446,460 $ 49,185 $ 941,153 5.57 Risk grade 9 1,660 95 268 1,192 26 — 10,955 39 14,235 9.00 Risk grade 10 — — 73 515 239 — — 58 885 10.00 Risk grade 11 9,097 221 541 4,630 885 164 5,000 — 20,538 11.00 Risk grade 12 3,463 — — — 21 — 2,771 187 6,442 12.00 Risk grade 13 2,316 — — — — — 2,356 — 4,672 13.00 $ 328,807 $ 111,479 $ 7,821 $ 12,669 $ 4,735 $ 5,403 $ 467,542 $ 49,469 $ 987,925 5.82 W/A risk grade 6.09 5.66 7.69 8.63 8.30 7.17 5.46 6.25 5.82 Commercial real estate: Buildings, land, other Risk grades 1-8 $ 1,101,851 $ 1,495,414 $ 999,836 $ 788,421 $ 428,539 $ 963,918 $ 84,964 $ 106,450 $ 5,969,393 6.90 Risk grade 9 64,026 27,271 99,934 47,898 20,773 35,908 7,412 2,848 306,070 9.00 Risk grade 10 5,851 17,824 17,104 52,210 20,353 53,622 3,500 — 170,464 10.00 Risk grade 11 162 434 1,269 7,189 8,969 44,318 206 — 62,547 11.00 Risk grade 12 646 6,545 — 229 313 2,592 — — 10,325 12.00 Risk grade 13 470 1,011 — — — — — — 1,481 13.00 $ 1,173,006 $ 1,548,499 $ 1,118,143 $ 895,947 $ 478,947 $ 1,100,358 $ 96,082 $ 109,298 $ 6,520,280 7.12 W/A risk grade 7.01 7.23 7.16 7.25 7.28 6.95 7.24 6.44 7.12 Construction Risk grades 1-8 $ 276,072 $ 662,364 $ 179,896 $ 100,915 $ 631 $ 1,804 $ 253,781 $ 4,247 $ 1,479,710 6.86 Risk grade 9 11,295 637 2,670 — — 401 — — 15,003 9.00 Risk grade 10 27,992 — — 13,103 — — — — 41,095 10.00 Risk grade 11 — — — — — — — — — 11.00 Risk grade 12 — — — — — — — — — 12.00 Risk grade 13 — — — — — — — — — 13.00 $ 315,359 $ 663,001 $ 182,566 $ 114,018 $ 631 $ 2,205 $ 253,781 $ 4,247 $ 1,535,808 6.96 W/A risk grade 7.10 7.12 6.64 8.21 6.21 7.16 6.10 5.01 6.96 Total commercial real estate $ 1,488,365 $ 2,211,500 $ 1,300,709 $ 1,009,965 $ 479,578 $ 1,102,563 $ 349,863 $ 113,545 $ 8,056,088 7.09 W/A risk grade 7.03 7.19 7.09 7.36 7.28 6.95 6.41 6.39 7.09
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 June 30, 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 $ 140 $ 287 $ 387 $ 668 $ 401 $ 2,771 $ 602 $ 1,665 $ 6,921 Past due 90 or more days — — — 4 142 875 247 — 1,268 Total past due 140 287 387 672 543 3,646 849 1,665 8,189 Current loans 154,178 324,089 211,133 80,351 43,828 137,836 592,539 8,892 1,552,846 Total $ 154,318 $ 324,376 $ 211,520 $ 81,023 $ 44,371 $ 141,482 $ 593,388 $ 10,557 $ 1,561,035 Consumer and other: Past due 30-89 days $ 1,974 $ 69 $ 64 $ 44 $ 5 $ 45 $ 32 $ 2,210 $ 4,443 Past due 90 or more days 439 — — 19 11 — — 129 598 Total past due 2,413 69 64 63 16 45 32 2,339 5,041 Current loans 31,230 30,712 10,798 4,166 1,814 2,042 391,713 22,266 494,741 Total $ 33,643 $ 30,781 $ 10,862 $ 4,229 $ 1,830 $ 2,087 $ 391,745 $ 24,605 $ 499,782
Revolving Loans Converted to Term [Table Text Block]	Revolving loans that converted to term during the three and six months ended June 30, 2022 and 2021 were as follows: Three Months Ended June 30, Six Months Ended June 30, 2022 2021 2022 2021 Commercial and industrial $ 16,518 $ 22,111 $ 21,973 $ 31,561 Energy 247 294 247 6,177 Commercial real estate: Buildings, land and other 10,681 8,195 10,726 31,321 Construction 13 — 4,248 — Consumer real estate 888 205 1,684 977 Consumer and other 1,792 1,961 5,868 5,696 Total $ 30,139 $ 32,766 $ 44,746 $ 75,732
Financing Receivable, Allowance for Credit Loss By Loan Class Calculated in Accordance With CECL Methodology	The following table presents details of the allowance for credit losses on loans segregated by loan portfolio segment as of June 30, 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. June 30, 2022 Commercial Energy Commercial Consumer Consumer Total Modeled expected credit losses $ 48,776 $ 6,106 $ 20,093 $ 6,639 $ 9,609 $ 91,223 Q-Factor and other qualitative adjustments 35,134 3,989 95,532 133 2,526 137,314 Specific allocations 3,360 6,172 1,481 82 — 11,095 Total $ 87,270 $ 16,267 $ 117,106 $ 6,854 $ 12,135 $ 239,632 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 and six months ended June 30, 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: June 30, 2022 Beginning balance $ 87,026 $ 15,422 $ 128,954 $ 6,359 $ 9,074 $ 246,835 Credit loss expense (benefit) 942 427 (12,232) 583 5,884 (4,396) Charge-offs (1,891) — — (131) (5,322) (7,344) Recoveries 1,193 418 384 43 2,499 4,537 Net charge-offs (698) 418 384 (88) (2,823) (2,807) Ending balance $ 87,270 $ 16,267 $ 117,106 $ 6,854 $ 12,135 $ 239,632 June 30, 2021 Beginning balance $ 70,892 $ 33,472 $ 144,440 $ 5,636 $ 6,818 $ 261,258 Credit loss expense (benefit) (5,901) (5,527) 3,654 611 2,784 (4,379) Charge-offs (685) — (137) (388) (3,882) (5,092) Recoveries 965 65 36 295 2,140 3,501 Net charge-offs 280 65 (101) (93) (1,742) (1,591) Ending balance $ 65,271 $ 28,010 $ 147,993 $ 6,154 $ 7,860 $ 255,288 Commercial Energy Commercial Consumer Consumer Total Six months ended: June 30, 2022 Beginning balance $ 72,091 $ 17,217 $ 144,936 $ 6,585 $ 7,837 $ 248,666 Credit loss expense (benefit) 18,503 (1,617) (27,841) 557 10,466 68 Charge-offs (5,346) (371) (702) (362) (11,093) (17,874) Recoveries 2,022 1,038 713 74 4,925 8,772 Net (charge-offs) recoveries (3,324) 667 11 (288) (6,168) (9,102) Ending balance $ 87,270 $ 16,267 $ 117,106 $ 6,854 $ 12,135 $ 239,632 June 30, 2021 Beginning balance $ 73,843 $ 39,553 $ 134,892 $ 7,926 $ 6,963 $ 263,177 Credit loss expense (benefit) (7,866) (11,328) 12,576 (2,111) 4,350 (4,379) Charge-offs (2,874) (1,433) (137) (672) (7,942) (13,058) Recoveries 2,168 1,218 662 1,011 4,489 9,548 Net (charge-offs) recoveries (706) (215) 525 339 (3,453) (3,510) Ending balance $ 65,271 $ 28,010 $ 147,993 $ 6,154 $ 7,860 $ 255,288
Investment in Loans Related to Allowance for Loan Losses by Portfolio Segment Disaggregated Based on Impairment Methodology	The following table presents loans that were evaluated for expected credit losses on an individual basis and the related specific allocations, by loan portfolio segment, as of June 30, 2022 and December 31, 2021. June 30, 2022 December 31, 2021 Loan Specific Allocations Loan Specific Allocations Commercial and industrial $ 12,539 $ 3,360 $ 24,523 $ 10,536 Energy 15,906 6,172 16,393 5,480 Paycheck Protection Program — — — — Commercial real estate: Buildings, land and other 21,205 1,481 24,670 200 Construction — — 948 200 Consumer real estate 934 82 303 36 Consumer and other — — — — Total $ 50,584 $ 11,095 $ 66,837 $ 16,452

Goodwill and Other Intangible_2

Goodwill and Other Intangible Assets (Tables)	6 Months Ended
	Jun. 30, 2022
Goodwill and Intangible Assets Disclosure [Abstract]
Schedule of Intangible Assets and Goodwill	Goodwill and other intangible assets are presented in the table below. June 30, December 31, Goodwill $ 654,952 $ 654,952 Other intangible assets: Core deposits $ 479 $ 718 Customer relationships 110 148 $ 589 $ 866
Estimated Aggregate Future Amortization Expense for Intangible Assets	The estimated aggregate future amortization expense for intangible assets remaining as of June 30, 2022 is as follows: Remainder of 2022 $ 204 2023 282 2024 87 2025 11 2026 5 $ 589

Deposits (Tables)

Deposits (Tables)	6 Months Ended
	Jun. 30, 2022
Disclosure Text Block [Abstract]
Deposit Liabilities, Type	Deposits were as follows: June 30, December 31, Non-interest-bearing demand deposits $ 18,783,931 $ 18,423,018 Interest-bearing deposits: Savings and interest checking 12,309,066 11,930,959 Money market accounts 12,989,902 11,228,815 Time accounts 1,518,866 1,112,904 Total interest-bearing deposits 26,817,834 24,272,678 Total deposits $ 45,601,765 $ 42,695,696
Additional Information About Corporation's Deposits	The following table presents additional information about our deposits: June 30, December 31, Deposits from foreign sources (primarily Mexico) $ 1,090,169 $ 993,479 Non-interest-bearing public funds deposits 681,205 1,235,026 Interest-bearing public funds deposits 837,427 810,863 Total deposits not covered by deposit insurance 25,810,407 24,125,359 Time deposits not covered by deposit insurance 364,486 238,608

Commitments and Contingencies (

Commitments and Contingencies (Tables)	6 Months Ended
	Jun. 30, 2022
Commitments and Contingencies Disclosure [Abstract]
Financial Instruments with Off-Balance-Sheet Risk	Financial instruments with off-balance-sheet risk were as follows: June 30, December 31, Commitments to extend credit $ 10,771,940 $ 10,420,142 Standby letters of credit 327,847 238,690 Deferred standby letter of credit fees 1,890 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 Six Months Ended 2022 2021 2022 2021 Beginning balance $ 45,850 $ 44,217 $ 50,314 $ 44,152 Credit loss expense (benefit) 4,396 4,379 (68) 4,444 Ending balance $ 50,246 $ 48,596 $ 50,246 $ 48,596
Lease Commitments, Components of Lease Expense [Table Text Block]	We lease certain office facilities and office equipment under operating leases. The components of total lease expense were as follows: Three Months Ended Six Months Ended 2022 2021 2022 2021 Amortization of lease right-of-use assets $ 8,209 $ 8,129 $ 16,314 $ 16,412 Short-term lease expense 490 530 1,103 734 Non-lease components (including taxes, insurance, common maintenance, etc.) 2,748 2,337 5,768 5,341 Total $ 11,447 $ 10,996 $ 23,185 $ 22,487

Capital and Regulatory Matters

Capital and Regulatory Matters (Tables)	6 Months Ended
	Jun. 30, 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 June 30, 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 June 30, 2022 Common Equity Tier 1 to Risk-Weighted Assets Cullen/Frost $ 3,485,759 12.64 % $ 1,930,703 7.00 % $ 1,792,796 6.50 % Frost Bank 3,423,585 12.42 1,929,368 7.00 1,791,556 6.50 Tier 1 Capital to Risk-Weighted Assets Cullen/Frost 3,631,211 13.17 2,344,425 8.50 2,206,518 8.00 Frost Bank 3,423,585 12.42 2,342,804 8.50 2,204,992 8.00 Total Capital to Risk-Weighted Assets Cullen/Frost 4,069,206 14.75 2,896,055 10.50 2,758,148 10.00 Frost Bank 3,661,580 13.28 2,894,052 10.50 2,756,240 10.00 Leverage Ratio Cullen/Frost 3,631,211 7.03 2,067,513 4.00 2,584,391 5.00 Frost Bank 3,423,585 6.62 2,067,942 4.00 2,584,928 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)	6 Months Ended
	Jun. 30, 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 June 30, 2022 and December 31, 2021. June 30, 2022 December 31, 2021 Notional Estimated Notional Estimated Derivatives designated as hedges of fair value: Financial institution counterparties: Loan/lease interest rate swaps – assets $ 1,743 $ 18 $ — $ — Loan/lease interest rate swaps – liabilities — — 2,426 (34) Non-hedging interest rate derivatives: Financial institution counterparties: Loan/lease interest rate swaps – assets 904,706 27,908 247,592 1,207 Loan/lease interest rate swaps – liabilities 244,663 (2,489) 928,756 (19,142) Loan/lease interest rate caps – assets 269,389 10,209 270,431 3,239 Customer counterparties: Loan/lease interest rate swaps – assets 244,663 3,350 928,756 39,864 Loan/lease interest rate swaps – liabilities 904,706 (45,542) 247,592 (2,846) Loan/lease interest rate caps – liabilities 269,389 (10,209) 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 June 30, 2022 were as follows: Weighted-Average Interest Interest Interest rate swaps: Fair value hedge loan/lease interest rate swaps 1.58 % 1.06 % Non-hedging interest rate swaps – financial institution counterparties 3.71 2.87 Non-hedging interest rate swaps – customer counterparties 2.87 3.71
Schedule of Notional Amounts and Estimated Fair Values of Commodity Derivative Positions	The notional amounts and estimated fair values of non-hedging commodity swap and option derivative positions outstanding are presented in the following table. We obtain dealer quotations and use internal valuation methods with observable market data inputs to value our commodity derivative positions. June 30, 2022 December 31, 2021 Notional Notional Estimated Notional Estimated Financial institution counterparties: Oil – assets Barrels 4,173 $ 20,653 4,809 $ 14,721 Oil – liabilities Barrels 9,125 (181,161) 7,032 (73,594) Natural gas – assets MMBTUs 11,753 3,181 15,947 4,143 Natural gas – liabilities MMBTUs 21,557 (38,990) 29,446 (21,249) Customer counterparties: Oil – assets Barrels 9,606 182,274 7,046 74,437 Oil – liabilities Barrels 3,692 (20,306) 4,796 (14,294) Natural gas – assets MMBTUs 21,557 39,110 29,446 21,456 Natural gas – liabilities MMBTUs 11,753 (3,181) 15,947 (4,124)
Schedule of Foreign Exchange Contracts, Statement of Financial Position	The notional amounts and fair values of open foreign currency forward and option contracts were as follows: June 30, 2022 December 31, 2021 Notional Notional Estimated Notional Estimated Financial institution counterparties: Forward and option contracts – assets EUR 6,400 $ 16 1,900 $ 29 Forward and option contracts – assets CAD 658 9 658 — Forward and option contracts – liabilities EUR 6,400 (174) — — Customer counterparties: Forward and option contracts – assets EUR 6,400 174 — — Forward and option contracts – assets CAD — — 658 4 Forward and option contracts – liabilities EUR 6,400 (16) 1,900 (55) Forward and option contracts – liabilities CAD 658 (5) — —
Schedule of Amounts Related to Interest Rate Derivatives Designated as Hedges of Fair Value	Amounts included in the consolidated statements of income related to interest rate derivatives designated as hedges of fair value were as follows: Three Months Ended Six Months Ended 2022 2021 2022 2021 Commercial loan/lease interest rate swaps: Amount of gain (loss) included in interest income on loans $ (5) $ (25) $ (18) $ (53) Amount of (gain) loss included in other non-interest expense 3 2 5 5
Schedule of Amounts Related to Non-Hedging Interest Rate and Commodity Derivatives	Amounts included in the consolidated statements of income related to non-hedge related derivative instruments are presented in the table below. Three Months Ended Six Months Ended 2022 2021 2022 2021 Non-hedging interest rate derivatives: Other non-interest income $ 515 $ 141 $ 1,031 $ 1,728 Other non-interest expense — — — (1) Non-hedging commodity derivatives: Other non-interest income 649 969 1,578 2,123 Non-hedging foreign currency derivatives: Other non-interest income 45 — 63 30

Balance Sheet Offsetting (Table

Balance Sheet Offsetting (Tables)	6 Months Ended
	Jun. 30, 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 June 30, 2022 is presented in the following tables. Gross Amount Gross Amount Net Amount June 30, 2022 Financial assets: Derivatives: Loan/lease interest rate swaps and caps $ 38,135 $ — $ 38,135 Commodity swaps and options 23,834 — 23,834 Foreign currency forward contracts 25 — 25 Total derivatives 61,994 — 61,994 Resell agreements 9,650 — 9,650 Total $ 71,644 $ — $ 71,644 Financial liabilities: Derivatives: Loan/lease interest rate swaps and caps $ 2,489 $ — $ 2,489 Commodity swaps and options 220,151 — 220,151 Foreign currency forward contracts 174 — 174 Total derivatives 222,814 — 222,814 Repurchase agreements 1,664,685 — 1,664,685 Total $ 1,887,499 $ — $ 1,887,499 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 June 30, 2022 Financial assets: Derivatives: Counterparty A $ 41 $ (41) $ — $ — Counterparty B 25,962 (25,962) — — Counterparty C 16 (16) — — Other counterparties 35,975 (25,533) (10,442) — Total derivatives 61,994 (51,552) (10,442) — Resell agreements 9,650 — (9,650) — Total $ 71,644 $ (51,552) $ (20,092) $ — Financial liabilities: Derivatives: Counterparty A $ 1,726 $ (41) $ (1,571) $ 114 Counterparty B 50,901 (25,962) (24,939) — Counterparty C 174 (16) (10) 148 Other counterparties 170,013 (25,533) (144,463) 17 Total derivatives 222,814 (51,552) (170,983) 279 Repurchase agreements 1,664,685 — (1,664,685) — Total $ 1,887,499 $ (51,552) $ (1,835,668) $ 279 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 June 30, 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 June 30, 2022 Repurchase agreements: U.S. Treasury $ 834,063 $ — $ — $ — $ 834,063 Residential mortgage-backed securities 830,622 — — — 830,622 Total borrowings $ 1,664,685 $ — $ — $ — $ 1,664,685 Gross amount of recognized liabilities for repurchase agreements $ 1,664,685 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)	6 Months Ended
	Jun. 30, 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 June 30, 2022, there were 788,070 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 5,382 133.67 3,460 132.72 — — — — Exercised/vested (16,022) 74.89 — — (25,180) 87.18 (103,060) 62.97 Forfeited/expired — — (3,167) 94.57 (16,058) 87.18 — — Balance, June 30, 2022 45,661 87.15 449,630 93.35 161,222 84.08 774,621 69.83
Shares Issued in Connection with Stock Compensation Awards	Shares issued in connection with stock compensation awards along with other related information were as follows: Three Months Ended Six Months Ended 2022 2021 2022 2021 New shares issued from available authorized shares — — — — Shares issued from available treasury stock 28,832 114,252 144,262 628,076 Proceeds from stock option exercises $ 751 $ 7,285 $ 6,490 $ 36,682
Share-based Payment Arrangement, Cost by Plan	Stock-based compensation expense or benefit and the related income tax benefit is presented in the following table. The service period for performance stock units granted each year begins on January 1 of the following year. Three Months Ended Six Months Ended 2022 2021 2022 2021 Non-vested stock units $ 2,291 $ 1,768 $ 4,649 $ 3,651 Deferred stock units 720 700 720 700 Performance stock units 407 777 161 1,420 Total $ 3,418 $ 3,245 $ 5,530 $ 5,771 Income tax benefit $ 612 $ 514 $ 1,320 $ 881
Unrecognized Stock-Based Compensation Expense	Unrecognized stock-based compensation expense at June 30, 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 $ 13,954 Performance stock units 8,256 Total $ 22,210

Earnings Per Common Share (Tabl

Earnings Per Common Share (Tables)	6 Months Ended
	Jun. 30, 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 Six Months Ended 2022 2021 2022 2021 Net income $ 119,114 $ 118,068 $ 218,216 $ 234,083 Less: Preferred stock dividends 1,669 1,669 3,338 3,820 Net income available to common shareholders 117,445 116,399 214,878 230,263 Less: Earnings allocated to participating securities 1,036 1,141 1,888 2,307 Net earnings allocated to common stock $ 116,409 $ 115,258 $ 212,990 $ 227,956 Distributed earnings allocated to common stock $ 48,092 $ 45,824 $ 96,143 $ 91,484 Undistributed earnings allocated to common stock 68,317 69,434 116,847 136,472 Net earnings allocated to common stock $ 116,409 $ 115,258 $ 212,990 $ 227,956 Weighted-average shares outstanding for basic earnings per common share 64,112,828 63,606,340 64,082,185 63,457,245 Dilutive effect of stock compensation 354,401 495,819 382,395 511,288 Weighted-average shares outstanding for diluted earnings per common share 64,467,229 64,102,159 64,464,580 63,968,533

Defined Benefit Plans (Tables)

Defined Benefit Plans (Tables)	6 Months Ended
	Jun. 30, 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 Six Months Ended 2022 2021 2022 2021 Expected return on plan assets, net of expenses $ (3,492) $ (3,210) $ (6,983) $ (6,420) Interest cost on projected benefit obligation 1,004 836 2,008 1,671 Net amortization and deferral 741 1,529 1,482 3,058 Net periodic expense (benefit) $ (1,747) $ (845) $ (3,493) $ (1,691)

Income Taxes (Tables)

Income Taxes (Tables)	6 Months Ended
	Jun. 30, 2022
Income Tax Disclosure [Abstract]
Income Tax Expense	Income tax expense was as follows: Three Months Ended Six Months Ended 2022 2021 2022 2021 Current income tax expense (benefit) $ 22,646 $ 14,065 $ 35,705 $ 17,790 Deferred income tax expense (benefit) (1,972) 1,016 (2,404) 5,188 Income tax expense, as reported $ 20,674 $ 15,081 $ 33,301 $ 22,978 Effective tax rate 14.8 % 11.3 % 13.2 % 8.9 %

Other Comprehensive Income (L_2

Other Comprehensive Income (Loss) (Tables)	6 Months Ended
	Jun. 30, 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 $ (636,523) $ (133,670) $ (502,853) $ 30,668 $ 6,441 $ 24,227 Change in net unrealized gain on securities transferred to held to maturity (189) (40) (149) (245) (52) (193) Reclassification adjustment for net (gains) losses included in net income — — — — — — Total securities available for sale and transferred securities (636,712) (133,710) (503,002) 30,423 6,389 24,034 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) 741 155 586 1,529 321 1,208 Total defined-benefit post-retirement benefit plans 741 155 586 1,529 321 1,208 Total other comprehensive income (loss) $ (635,971) $ (133,555) $ (502,416) $ 31,952 $ 6,710 $ 25,242 Six Months Ended Six Months Ended Before Tax Tax Expense, Net of Tax Before Tax Tax Expense, Net of Tax Securities available for sale and transferred securities: Change in net unrealized gain/loss during the period $ (1,547,318) $ (324,937) $ (1,222,381) $ (129,111) $ (27,113) $ (101,998) Change in net unrealized gain on securities transferred to held to maturity (398) (84) (314) (504) (106) (398) Reclassification adjustment for net (gains) losses included in net income — — — — — — Total securities available for sale and transferred securities (1,547,716) (325,021) (1,222,695) (129,615) (27,219) (102,396) 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) 1,482 311 1,171 3,058 642 2,416 Total defined-benefit post-retirement benefit plans 1,482 311 1,171 3,058 642 2,416 Total other comprehensive income (loss) $ (1,546,234) $ (324,710) $ (1,221,524) $ (126,557) $ (26,577) $ (99,980)
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 (1,222,695) — (1,222,695) Reclassification of amounts included in net income — 1,171 1,171 Net other comprehensive income (loss) during period (1,222,695) 1,171 (1,221,524) Balance at June 30, 2022 $ (842,486) $ (31,720) $ (874,206) Balance January 1, 2021 $ 563,801 $ (50,831) $ 512,970 Other comprehensive income (loss) before reclassifications (102,396) — (102,396) Reclassification of amounts included in net income — 2,416 2,416 Net other comprehensive income (loss) during period (102,396) 2,416 (99,980) Balance at June 30, 2021 $ 461,405 $ (48,415) $ 412,990

Operating Segments (Tables)

Operating Segments (Tables)	6 Months Ended
	Jun. 30, 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: June 30, 2022 Net interest income (expense) $ 289,186 $ 958 $ (1,936) $ 288,208 Credit loss expense 1 (1) — — Non-interest income 55,397 43,054 (524) 97,927 Non-interest expense 211,044 33,158 2,145 246,347 Income (loss) before income taxes 133,538 10,855 (4,605) 139,788 Income tax expense (benefit) 19,821 2,279 (1,426) 20,674 Net income (loss) 113,717 8,576 (3,179) 119,114 Preferred stock dividends — — 1,669 1,669 Net income (loss) available to common shareholders $ 113,717 $ 8,576 $ (4,848) $ 117,445 Revenues from (expenses to) external customers $ 344,583 $ 44,012 $ (2,460) $ 386,135 June 30, 2021 Net interest income (expense) $ 258,450 $ 508 $ (1,802) $ 257,156 Credit loss expense (benefit) — — — — Non-interest income 48,944 42,534 (231) 91,247 Non-interest expense 183,109 30,014 2,131 215,254 Income (loss) before income taxes 124,285 13,028 (4,164) 133,149 Income tax expense (benefit) 13,605 2,736 (1,260) 15,081 Net income (loss) 110,680 10,292 (2,904) 118,068 Preferred stock dividends — — 1,669 1,669 Net income (loss) available to common shareholders $ 110,680 $ 10,292 $ (4,573) $ 116,399 Revenues from (expenses to) external customers $ 307,394 $ 43,042 $ (2,033) $ 348,403 Six months ended: June 30, 2022 Net interest income (expense) $ 539,305 $ 1,658 $ (3,684) $ 537,279 Credit loss expense (benefit) — — — — Non-interest income 114,103 86,283 (1,069) 199,317 Non-interest expense 417,582 64,068 3,429 485,079 Income (loss) before income taxes 235,826 23,873 (8,182) 251,517 Income tax expense (benefit) 30,835 5,013 (2,547) 33,301 Net income (loss) 204,991 18,860 (5,635) 218,216 Preferred stock dividends — — 3,338 3,338 Net income (loss) available to common shareholders $ 204,991 $ 18,860 $ (8,973) $ 214,878 Revenues from (expenses to) external customers $ 653,408 $ 87,941 $ (4,753) $ 736,596 June 30, 2021 Net interest income (expense) $ 500,655 $ 994 $ (3,612) $ 498,037 Credit loss expense 63 — — 63 Non-interest income 102,724 82,143 (384) 184,483 Non-interest expense 362,260 59,951 3,185 425,396 Income (loss) before income taxes 241,056 23,186 (7,181) 257,061 Income tax expense (benefit) 20,782 4,869 (2,673) 22,978 Net income (loss) 220,274 18,317 (4,508) 234,083 Preferred stock dividends — — 3,820 3,820 Net income (loss) available to common shareholders $ 220,274 $ 18,317 $ (8,328) $ 230,263 Revenues from (expenses to) external customers $ 603,379 $ 83,137 $ (3,996) $ 682,520

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	6 Months Ended
	Jun. 30, 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 June 30, 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 June 30, 2022 Securities available for sale: U.S. Treasury $ 4,416,299 $ — $ — $ 4,416,299 Residential mortgage-backed securities — 5,335,725 — 5,335,725 States and political subdivisions — 6,987,296 — 6,987,296 Other — 42,365 — 42,365 Trading account securities: U.S. Treasury 24,615 — — 24,615 States and political subdivisions — 65 — 65 Derivative assets: Interest rate swaps, caps and floors — 41,485 — 41,485 Commodity swaps and options — 245,218 — 245,218 Foreign currency forward contracts 199 — — 199 Derivative liabilities: Interest rate swaps, caps and floors — 58,240 — 58,240 Commodity swaps and options — 243,638 — 243,638 Foreign currency forward contracts 195 — — 195 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. Six Months Ended Six Months Ended Level 2 Level 3 Level 2 Level 3 Carrying value before allocations $ 5,454 $ 3,614 $ 3,399 $ 19,423 Specific (allocations) reversals of prior allocations (1,327) 6,877 (336) (3,273) Fair value $ 4,127 $ 10,491 $ 3,063 $ 16,150
Estimated Fair Values of Financial Instruments	The estimated fair values of financial instruments that are reported at amortized cost in our consolidated balance sheets, segregated by the level of the valuation inputs within the fair value hierarchy utilized to measure fair value, were as follows: June 30, 2022 December 31, 2021 Carrying Estimated Carrying Estimated Financial assets: Level 2 inputs: Cash and cash equivalents $ 13,658,585 $ 13,658,585 $ 16,583,000 $ 16,583,000 Securities held to maturity 1,946,428 1,828,515 1,749,179 1,809,143 Cash surrender value of life insurance policies 189,823 189,823 190,139 190,139 Accrued interest receivable 194,049 194,049 179,111 179,111 Level 3 inputs: Loans, net 16,496,394 16,126,497 16,087,731 16,079,454 Financial liabilities: Level 2 inputs: Deposits 45,601,765 45,584,113 42,695,696 41,343,426 Federal funds purchased 43,200 43,200 25,925 25,925 Repurchase agreements 1,664,685 1,664,685 2,740,799 2,740,799 Junior subordinated deferrable interest debentures 123,040 123,712 123,011 123,712 Subordinated notes 99,256 99,626 99,178 111,430 Accrued interest payable 6,059 6,059 3,026 3,026

Significant Accounting Polici_4

Significant Accounting Policies - Additional Cash Flow Information (Detail) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021
Accounting Policies [Abstract]
Cash paid for interest	$ 22,551	$ 15,936
Cash paid for income taxes	45,500	15,400
Unsettled securities transactions	110,623	358,752
Loans foreclosed and transferred to other real estate owned and foreclosed assets	0	3,251
Right-of-use lease assets obtained in exchange for lessee operating lease liabilities	8,857	1,552
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		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021	Dec. 31, 2021
Schedule Of Marketable Securities [Line Items]
AOCI, Debt Securities, Available-for-sale, Adjustment, Pre Tax	$ 2,100		$ 2,100		$ 2,500
Net unamortized unrealized gain on transferred securities included in accumulated other comprehensive income, net of tax	$ 1,700		$ 1,700		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	75.30%		75.30%
Debt Securities, Available-for-sale, Allowance for Credit Loss	$ 0		$ 0		0
Proceeds from Sale of Held-to-maturity Securities	0	$ 0	0	$ 0
Proceeds from Sale of Debt Securities, Available-for-sale	0	$ 0	0	$ 0
Held-to-maturity Securities [Member]
Schedule Of Marketable Securities [Line Items]
Carry value of securities pledged	245,500		245,500		642,300
Accrued interest receivable	18,000		18,000		18,400
Available-for-sale Securities [Member]
Schedule Of Marketable Securities [Line Items]
Carry value of securities pledged	4,400,000		4,400,000		5,800,000
Accrued interest receivable	$ 131,300		$ 131,300		$ 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	Jun. 30, 2022	Dec. 31, 2021
Schedule of Investments [Line Items]
Held to Maturity, Amortized Cost	$ 1,946,586	$ 1,749,337
Debt Securities, Held-to-maturity, Accumulated Unrecognized Gain	3,956	59,907
Debt Securities, Held-to-maturity, Accumulated Unrecognized Loss	122,027	101
Debt Securities, Held-to-maturity, Fair Value	1,828,515	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 June 30, 2022 and $158 at December 31, 2021	1,946,428	1,749,179
Residential Mortgage Backed Securities [Member]
Schedule of Investments [Line Items]
Held to Maturity, Amortized Cost	526,675	527,264
Debt Securities, Held-to-maturity, Accumulated Unrecognized Gain	0	18,766
Debt Securities, Held-to-maturity, Accumulated Unrecognized Loss	40,383	0
Debt Securities, Held-to-maturity, Fair Value	486,292	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 June 30, 2022 and $158 at December 31, 2021	526,675	527,264
US States and Political Subdivisions Debt Securities [Member]
Schedule of Investments [Line Items]
Held to Maturity, Amortized Cost	1,418,411	1,220,573
Debt Securities, Held-to-maturity, Accumulated Unrecognized Gain	3,956	41,141
Debt Securities, Held-to-maturity, Accumulated Unrecognized Loss	81,583	101
Debt Securities, Held-to-maturity, Fair Value	1,340,784	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 June 30, 2022 and $158 at December 31, 2021	1,418,253	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	61	0
Debt Securities, Held-to-maturity, Fair Value	1,439	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 June 30, 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	Jun. 30, 2022	Dec. 31, 2021
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-maturity	$ 1,946,586	$ 1,749,337
US States and Political Subdivisions Debt Securities [Member]
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-maturity	1,418,411	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	1,270,014	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	148,397	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	309,671	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	161,274	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	148,397	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	764,405	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	764,405	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	344,335	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	344,335	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		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021	Mar. 31, 2022	Dec. 31, 2021	Mar. 31, 2021	Dec. 31, 2020
Schedule of Held-to-maturity Securities [Line Items]
Securities, held-to-maturity, allowance for credit loss	$ 158		$ 158			$ 158
Debt Securities [Member]
Schedule of Held-to-maturity Securities [Line Items]
Securities, held-to-maturity, allowance for credit loss	158	$ 158	158	$ 158	$ 158	$ 158	$ 158	$ 160
Credit loss expense (benefit)	$ 0	$ 0	$ 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	Jun. 30, 2022	Dec. 31, 2021
Schedule of Investments [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	$ 17,850,263	$ 13,445,888
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	56,001	518,805
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	1,124,579	40,065
Debt Securities, Available-for-sale, Allowance for Credit Loss	0	0
Securities available for sale, at estimated fair value	16,781,685	13,924,628
US Treasury Securities [Member]
Schedule of Investments [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	4,656,896	2,165,702
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	2,093	23,333
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	242,690	9,602
Debt Securities, Available-for-sale, Allowance for Credit Loss	0	0
Securities available for sale, at estimated fair value	4,416,299	2,179,433
Residential Mortgage Backed Securities [Member]
Schedule of Investments [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	5,967,803	4,059,692
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	3,443	31,662
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	635,521	25,089
Debt Securities, Available-for-sale, Allowance for Credit Loss	0	0
Securities available for sale, at estimated fair value	5,335,725	4,066,265
US States and Political Subdivisions Debt Securities [Member]
Schedule of Investments [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	7,183,199	7,178,135
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	50,465	463,810
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	246,368	5,374
Debt Securities, Available-for-sale, Allowance for Credit Loss	0	0
Securities available for sale, at estimated fair value	6,987,296	7,636,571
Other Investments [Member]
Schedule of Investments [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	42,365	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	$ 42,365	$ 42,359

Securities - Securities Availab

Securities - Securities Available for Sale, with Unrealized Losses Segregated by Length of Impairment (Detail) - USD ($) $ in Thousands	Jun. 30, 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	$ 12,299,514
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	1,052,979
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	382,922
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	71,600
Debt Securities, Available-for-sale, Unrealized Loss Position	12,682,436
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	1,124,579	$ 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	4,224,018
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	242,690
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	4,224,018
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	242,690	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	4,825,871
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	568,405
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	369,098
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	67,116
Debt Securities, Available-for-sale, Unrealized Loss Position	5,194,969
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	635,521	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	3,249,625
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	241,884
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	13,824
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	4,484
Debt Securities, Available-for-sale, Unrealized Loss Position	3,263,449
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	$ 246,368	$ 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	Jun. 30, 2022	Dec. 31, 2021
Schedule of Investments [Line Items]
Held to Maturity, Due in one year or less, Amortized Cost	$ 350,368
Held to Maturity, Due after one year through five years, Amortized Cost	85,553
Held to Maturity, Due after five years through ten years, Amortized Cost	536,684
Held to Maturity, Due after ten years, Amortized Cost	973,981
Held to Maturity, Amortized Cost	1,946,586	$ 1,749,337
Held to Maturity, Due in one year or less, Estimated Fair Value	351,240
Held to Maturity, Due after one year through five years, Estimated Fair Value	86,226
Held to Maturity, Due after five years through ten years, Estimated Fair Value	497,887
Held to Maturity, Due after ten years, Estimated Fair Value	893,162
Held to Maturity, Estimated Fair Value	1,828,515	1,809,143
Available-for-sale Securities, Due in one year or less, Amortized Cost	207,133
Available for Sale, Due after one year through five years, Amortized Cost	4,589,781
Available for Sale, Due after five years through ten years, Amortized Cost	2,355,016
Available for Sale, Due after ten years, Amortized Cost	10,655,968
Debt Securities, Available-for-sale, Amortized Cost	17,850,263	13,445,888
Available for Sale, Due in one year or less, Estimated Fair Value	209,193
Available for Sale, Due after one year through five years, Estimated Fair Value	4,547,346
Available for Sale, Due after five years through ten years, Estimated Fair Value	2,213,463
Available for Sale, Due after ten years, Estimated Fair Value	9,769,318
Securities available for sale, at estimated fair value	16,781,685	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	3,031,706
Available for Sale, Due after five years through ten years, Amortized Cost	1,433,320
Available for Sale, Due after ten years, Amortized Cost	191,870
Debt Securities, Available-for-sale, Amortized Cost	4,656,896	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	2,957,018
Available for Sale, Due after five years through ten years, Estimated Fair Value	1,301,539
Available for Sale, Due after ten years, Estimated Fair Value	157,742
Securities available for sale, at estimated fair value	4,416,299	2,179,433
Residential Mortgage Backed Securities [Member]
Schedule of Investments [Line Items]
Held to Maturity, Due in one year or less, Amortized Cost	3
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	514,582
Held to Maturity, Due after ten years, Amortized Cost	12,090
Held to Maturity, Amortized Cost	526,675	527,264
Held to Maturity, Due in one year or less, Estimated Fair Value	3
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	475,721
Held to Maturity, Due after ten years, Estimated Fair Value	10,568
Held to Maturity, Estimated Fair Value	486,292	546,030
Available-for-sale Securities, Due in one year or less, Amortized Cost	55
Available for Sale, Due after one year through five years, Amortized Cost	11,080
Available for Sale, Due after five years through ten years, Amortized Cost	18,743
Available for Sale, Due after ten years, Amortized Cost	5,937,925
Debt Securities, Available-for-sale, Amortized Cost	5,967,803	4,059,692
Available for Sale, Due in one year or less, Estimated Fair Value	55
Available for Sale, Due after one year through five years, Estimated Fair Value	11,231
Available for Sale, Due after five years through ten years, Estimated Fair Value	18,792
Available for Sale, Due after ten years, Estimated Fair Value	5,305,647
Securities available for sale, at estimated fair value	5,335,725	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	350,365
Held to Maturity, Due after one year through five years, Amortized Cost	84,053
Held to Maturity, Due after five years through ten years, Amortized Cost	22,102
Held to Maturity, Due after ten years, Amortized Cost	961,891
Held to Maturity, Amortized Cost	1,418,411	1,220,573
Held to Maturity, Due in one year or less, Estimated Fair Value	351,237
Held to Maturity, Due after one year through five years, Estimated Fair Value	84,787
Held to Maturity, Due after five years through ten years, Estimated Fair Value	22,166
Held to Maturity, Due after ten years, Estimated Fair Value	882,594
Held to Maturity, Estimated Fair Value	1,340,784	1,261,613
Available-for-sale Securities, Due in one year or less, Amortized Cost	207,078
Available for Sale, Due after one year through five years, Amortized Cost	1,546,995
Available for Sale, Due after five years through ten years, Amortized Cost	902,953
Available for Sale, Due after ten years, Amortized Cost	4,526,173
Debt Securities, Available-for-sale, Amortized Cost	7,183,199	7,178,135
Available for Sale, Due in one year or less, Estimated Fair Value	209,138
Available for Sale, Due after one year through five years, Estimated Fair Value	1,579,097
Available for Sale, Due after five years through ten years, Estimated Fair Value	893,132
Available for Sale, Due after ten years, Estimated Fair Value	4,305,929
Securities available for sale, at estimated fair value	6,987,296	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	1,439
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	1,439	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	42,365	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	$ 42,365	$ 42,359

Securities Securities - Premium

Securities Securities - Premium Amortization and Discount Accretion Included in Income on Securities (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Investments, Debt and Equity Securities [Abstract]
Premium amortization	$ (28,053)	$ (30,541)	$ (57,113)	$ (61,776)
Discount accretion	2,482	705	3,888	1,342
Net (premium amortization) discount accretion	$ (25,571)	$ (29,836)	$ (53,225)	$ (60,434)

Securities - Trading Account Se

Securities - Trading Account Securities, at Estimated Fair Value (Detail) - USD ($) $ in Thousands	Jun. 30, 2022	Dec. 31, 2021
Debt and Equity Securities, FV-NI [Line Items]
Trading account securities	$ 24,680	$ 25,162
U.S. Treasury [Member]
Debt and Equity Securities, FV-NI [Line Items]
Trading account securities	24,615	24,237
States and political subdivisions [Member]
Debt and Equity Securities, FV-NI [Line Items]
Trading account securities	$ 65	$ 925

Securities - Net Gains and Loss

Securities - Net Gains and Losses on Trading Account Securities (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Investments, Debt and Equity Securities [Abstract]
Net gain on sales transactions	$ 1,012	$ 293	$ 1,352	$ 402
Net mark-to-market gains (losses)	(76)	0	(244)	(69)
Net gain (loss) on trading account securities	$ 936	$ 293	$ 1,108	$ 333

Loans - Additional Information

Loans - Additional Information (Detail) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2022 USD ($)	Jun. 30, 2021 USD ($)	Jun. 30, 2022 USD ($)	Jun. 30, 2021 USD ($)	Mar. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)	Mar. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)
Accounts, Notes, Loans and Financing Receivable [Line Items]
Concentration of loans in a single industry in excess of ten percent	0%		0%
Maximum percentage loan related to single industry	10%		10%
U.S. dollar denominated loans and commitments to borrowers in Mexico	$ 0		$ 0			$ 0
Loans and Leases Receivable, Related Parties	$ 342,500		$ 342,500			$ 350,500
Texas Leading Index economic condition indicator	138.4		138.4			135.9
Financing Receivable, Allowance for Credit Loss	$ 239,632		$ 239,632			$ 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	5.90%		5.90%
Percentage of total energy loans to total loans excluding PPP Loans	5.90%		5.90%
Financing Receivable, Allowance for Credit Loss	$ 16,267	$ 28,010	$ 16,267	$ 28,010	$ 15,422	17,217	$ 33,472	$ 39,553
Paycheck Protection Program [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Allowance for Credit Loss	0	0	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	436	$ 427	843	$ 881
Commitments to Extend Credit [Member] | Commercial and Industrial Total Energy Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unfunded balances	887,300		887,300
Standby Letters of Credit [Member] | Commercial and Industrial Total Energy Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unfunded balances	79,100		79,100
Loans Receivable [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Interest Receivable	$ 44,800		$ 44,800			$ 40,000

Loans - Loans (Detail)

Loans - Loans (Detail) - USD ($) $ in Thousands	Jun. 30, 2022	Dec. 31, 2021
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	$ 16,736,026	$ 16,336,397
Commercial Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	5,539,277	5,364,954
Energy Production [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	762,625	878,436
Energy Service [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	121,356	105,901
Energy Other [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	103,944	93,455
Commercial and Industrial Total Energy Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	987,925	1,077,792
Paycheck Protection Program [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	91,919	428,882
Commercial mortgage [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	6,041,606	5,867,062
Construction Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	1,535,808	1,304,271
Commercial land loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	478,674	405,277
Commercial Real Estate Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	8,056,088	7,576,610
Home Equity Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	352,633	324,157
Home Equity Line of Credit [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	603,907	519,098
Other consumer real estate loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	604,495	567,535
Total consumer real estate loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	1,561,035	1,410,790
Real Estate Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	9,617,123	8,987,400
Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	$ 499,782	$ 477,369

Loans - Non-Accrual Loans, Segr

Loans - Non-Accrual Loans, Segregated by Class of Loans (Detail) - USD ($) $ in Thousands	Jun. 30, 2022	Dec. 31, 2021
Non Accrual Loans Segregated By Class Of Loans [Line Items]
Non-accrual loans	$ 35,125	$ 53,713
Non-accrual with no credit loss allowance	16,686	27,202
Commercial Portfolio Segment [Member]
Non Accrual Loans Segregated By Class Of Loans [Line Items]
Non-accrual loans	11,170	22,582
Non-accrual with no credit loss allowance	3,093	4,701
Commercial and Industrial Total Energy Loans [Member]
Non Accrual Loans Segregated By Class Of Loans [Line Items]
Non-accrual loans	11,114	14,433
Non-accrual with no credit loss allowance	6,442	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	11,806	15,297
Non-accrual with no credit loss allowance	6,419	13,817
Construction Loans [Member]
Non Accrual Loans Segregated By Class Of Loans [Line Items]
Non-accrual loans	0	948
Non-accrual with no credit loss allowance	0	0
Total consumer real estate loans [Member]
Non Accrual Loans Segregated By Class Of Loans [Line Items]
Non-accrual loans	1,035	440
Non-accrual with no credit loss allowance	732	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	Jun. 30, 2022	Dec. 31, 2021
Loans and Leases Receivable Disclosure [Line Items]
Non-accrual loans	$ 35,125	$ 53,713
Nonperforming Financial Instruments [Member]
Loans and Leases Receivable Disclosure [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	6,895
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	7,654
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	3,520
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	3,736
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	1,825
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	3,625
Financing Receivable, Revolving	5,235
Financing Receivable, Revolving, Converted to Term Loan	2,635
Commercial Portfolio Segment [Member]
Loans and Leases Receivable Disclosure [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	1,027,153
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	852,191
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	582,273
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	289,898
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	167,930
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	232,809
Financing Receivable, Revolving	2,318,394
Non-accrual loans	11,170	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	98
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	3,520
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	3,507
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	1,491
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	653
Financing Receivable, Revolving	108
Financing Receivable, Revolving, Converted to Term Loan	1,793
Commercial and Industrial Total Energy Loans [Member]
Loans and Leases Receivable Disclosure [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	328,807
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	111,479
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	7,821
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	12,669
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	4,735
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	5,403
Financing Receivable, Revolving	467,542
Non-accrual loans	11,114	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	5,779
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	21
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	0
Financing Receivable, Revolving	5,127
Financing Receivable, Revolving, Converted to Term Loan	187
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	1,173,006
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	1,548,499
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	1,118,143
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	895,947
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	478,947
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	1,100,358
Financing Receivable, Revolving	96,082
Non-accrual loans	11,806	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	1,116
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	7,556
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	0
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	229
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	313
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	2,592
Financing Receivable, Revolving	0
Financing Receivable, Revolving, Converted to Term Loan	0
Construction Loans [Member]
Loans and Leases Receivable Disclosure [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	315,359
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	663,001
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	182,566
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	114,018
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	631
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	2,205
Financing Receivable, Revolving	253,781
Non-accrual loans	0	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	0
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	0
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	0
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	0
Financing Receivable, Revolving	0
Financing Receivable, Revolving, Converted to Term Loan	0
Total consumer real estate loans [Member]
Loans and Leases Receivable Disclosure [Line Items]
Non-accrual loans	1,035	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	380
Financing Receivable, Revolving	0
Financing Receivable, Revolving, Converted to Term Loan	655
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	Jun. 30, 2022	Dec. 31, 2021
Financing Receivable, Past Due [Line Items]
Total loans	$ 16,736,026	$ 16,336,397
Accruing Loans 90 or More Days Past Due	10,625
Commercial Portfolio Segment [Member]
Financing Receivable, Past Due [Line Items]
Total loans	5,539,277	5,364,954
Accruing Loans 90 or More Days Past Due	3,280
Commercial and Industrial Total Energy Loans [Member]
Financing Receivable, Past Due [Line Items]
Total loans	987,925	1,077,792
Accruing Loans 90 or More Days Past Due	0
Paycheck Protection Program [Member]
Financing Receivable, Past Due [Line Items]
Total loans	91,919	428,882
Accruing Loans 90 or More Days Past Due	5,063
Commercial Real Estate Buildings Land And Other Loans [Member]
Financing Receivable, Past Due [Line Items]
Total loans	6,520,280	6,272,339
Accruing Loans 90 or More Days Past Due	781
Construction Loans [Member]
Financing Receivable, Past Due [Line Items]
Total loans	1,535,808	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	1,561,035	1,410,790
Accruing Loans 90 or More Days Past Due	903
Consumer Loan [Member]
Financing Receivable, Past Due [Line Items]
Total loans	499,782	$ 477,369
Accruing Loans 90 or More Days Past Due	598
Financing Receivables, 30 to 89 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	50,696
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	14,529
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	200
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	5,919
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	17,852
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	832
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	6,921
Financing Receivables, 30 to 89 Days Past Due [Member] | Consumer Loan [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	4,443
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	21,638
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	3,993
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	3,275
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	5,063
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	7,441
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	1,268
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	598
Financial Asset, Past Due
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	72,334
Financial Asset, Past Due | Commercial Portfolio Segment [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	18,522
Financial Asset, Past Due | Commercial and Industrial Total Energy Loans [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	3,475
Financial Asset, Past Due | Paycheck Protection Program [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	10,982
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	25,293
Financial Asset, Past Due | Construction Loans [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	832
Financial Asset, Past Due | Total consumer real estate loans [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	8,189
Financial Asset, Past Due | Consumer Loan [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	5,041
Financial Asset, Not Past Due
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	16,663,692
Financial Asset, Not Past Due | Commercial Portfolio Segment [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	5,520,755
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	984,450
Financial Asset, Not Past Due | Paycheck Protection Program [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	80,937
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	6,494,987
Financial Asset, Not Past Due | Construction Loans [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	1,534,976
Financial Asset, Not Past Due | Total consumer real estate loans [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	1,552,846
Financial Asset, Not Past Due | Consumer Loan [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	$ 494,741

Loans - Troubled Debt Restructu

Loans - Troubled Debt Restructuring (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021
Financing Receivable, Troubled Debt Restructuring [Line Items]
Loans modified as troubled debt restructurings	$ 1,155	$ 4,399
Balance at period end	1,116	4,396
Commercial and Industrial Total Energy Loans [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Loans modified as troubled debt restructurings	0	3,817
Balance at period end	0	3,817
Commercial Real Estate Buildings Land And Other Loans [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Loans modified as troubled debt restructurings	1,155	582
Balance at period end	$ 1,116	$ 579

Loans Loans - Restructured Loan

Loans Loans - Restructured Loans Past Due in Excess of 90 Days on Financing Receivables (Details) $ in Thousands	6 Months Ended
	Jun. 30, 2022 USD ($) Item	Jun. 30, 2021 USD ($) Item
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number Of Restructured Loans Past Due In Excess of 90 Days At Period-End | Item	0	1
Dollar amount of previously restructured loans past due	$ 0	$ 1,322
Restructured loans on non-accrual status at period end	1,116	4,090
Charge-offs of restructured loans recognized in connection with restructuring	0	0
Charge-offs of restructured loans recognized on previously restructured loans	723	0
Proceeds from sale of restructured loans	$ 1,070	$ 0

Loans Loans - Weighted Average

Loans Loans - Weighted Average Risk Grade for All Commercial Loans by Class and Year of Origination (Details) $ in Thousands	Jun. 30, 2022 USD ($) Grade	Dec. 31, 2021 USD ($) Grade
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Net of Deferred Income	$ 16,736,026	$ 16,336,397
Commercial Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	1,027,153
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	852,191
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	582,273
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	289,898
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	167,930
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	232,809
Financing Receivable, Revolving	2,318,394
Loans and Leases Receivable, Net of Deferred Income	$ 5,539,277	$ 5,364,954
Weighted Average Risk Grade For Loans | Grade	6.38	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	$ 328,807
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	111,479
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	7,821
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	12,669
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	4,735
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	5,403
Financing Receivable, Revolving	467,542
Loans and Leases Receivable, Net of Deferred Income	$ 987,925	$ 1,077,792
Weighted Average Risk Grade For Loans | Grade	5.82	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	$ 1,173,006
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	1,548,499
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	1,118,143
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	895,947
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	478,947
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	1,100,358
Financing Receivable, Revolving	96,082
Loans and Leases Receivable, Net of Deferred Income	$ 6,520,280	$ 6,272,339
Weighted Average Risk Grade For Loans | Grade	7.12	7.22
Construction Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	$ 315,359
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	663,001
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	182,566
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	114,018
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	631
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	2,205
Financing Receivable, Revolving	253,781
Loans and Leases Receivable, Net of Deferred Income	$ 1,535,808	$ 1,304,271
Weighted Average Risk Grade For Loans | Grade	6.96	7.06
Commercial Real Estate Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	$ 1,488,365
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	2,211,500
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	1,300,709
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	1,009,965
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	479,578
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	1,102,563
Financing Receivable, Revolving	349,863
Loans and Leases Receivable, Net of Deferred Income	$ 8,056,088	$ 7,576,610
Weighted Average Risk Grade For Loans | Grade	7.09	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	$ 1,009,520
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	805,675
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	563,122
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	267,129
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	142,114
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	221,192
Financing Receivable, Revolving	2,213,761
Loans and Leases Receivable, Net of Deferred Income	$ 5,276,748	$ 5,063,847
Weighted Average Risk Grade For Loans | Grade	6.23	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	$ 312,271
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	111,163
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	6,939
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	6,332
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	3,564
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	5,239
Financing Receivable, Revolving	446,460
Loans and Leases Receivable, Net of Deferred Income	$ 941,153	$ 1,008,370
Weighted Average Risk Grade For Loans | Grade	5.57	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	$ 1,101,851
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	1,495,414
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	999,836
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	788,421
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	428,539
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	963,918
Financing Receivable, Revolving	84,964
Loans and Leases Receivable, Net of Deferred Income	$ 5,969,393	$ 5,574,922
Weighted Average Risk Grade For Loans | Grade	6.90	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	$ 276,072
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	662,364
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	179,896
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	100,915
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	631
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	1,804
Financing Receivable, Revolving	253,781
Loans and Leases Receivable, Net of Deferred Income	$ 1,479,710	$ 1,262,200
Weighted Average Risk Grade For Loans | Grade	6.86	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	$ 12,633
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	21,474
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	6,914
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	9,067
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	20,961
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	8,682
Financing Receivable, Revolving	79,546
Loans and Leases Receivable, Net of Deferred Income	$ 164,939	$ 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	$ 1,660
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	95
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	268
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	1,192
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	26
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	0
Financing Receivable, Revolving	10,955
Loans and Leases Receivable, Net of Deferred Income	$ 14,235	$ 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	$ 64,026
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	27,271
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	99,934
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	47,898
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	20,773
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	35,908
Financing Receivable, Revolving	7,412
Loans and Leases Receivable, Net of Deferred Income	$ 306,070	$ 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	$ 11,295
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	637
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	2,670
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	401
Financing Receivable, Revolving	0
Loans and Leases Receivable, Net of Deferred Income	$ 15,003	$ 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	$ 5,000
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	23,293
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	2,437
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	705
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	1,808
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	255
Financing Receivable, Revolving	20,879
Loans and Leases Receivable, Net of Deferred Income	$ 56,470	$ 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	73
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	515
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	239
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	0
Financing Receivable, Revolving	0
Loans and Leases Receivable, Net of Deferred Income	$ 885	$ 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	$ 5,851
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	17,824
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	17,104
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	52,210
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	20,353
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	53,622
Financing Receivable, Revolving	3,500
Loans and Leases Receivable, Net of Deferred Income	$ 170,464	$ 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	$ 27,992
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	13,103
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	0
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	0
Financing Receivable, Revolving	0
Loans and Leases Receivable, Net of Deferred Income	$ 41,095	$ 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	1,651
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	6,280
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	9,490
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	1,556
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	2,027
Financing Receivable, Revolving	4,100
Loans and Leases Receivable, Net of Deferred Income	$ 29,950	$ 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	221
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	541
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	4,630
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	885
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	164
Financing Receivable, Revolving	5,000
Loans and Leases Receivable, Net of Deferred Income	$ 20,538	$ 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	$ 162
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	434
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	1,269
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	7,189
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	8,969
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	44,318
Financing Receivable, Revolving	206
Loans and Leases Receivable, Net of Deferred Income	$ 62,547	$ 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	98
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	2,569
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	3,106
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	1,427
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	251
Financing Receivable, Revolving	108
Loans and Leases Receivable, Net of Deferred Income	$ 8,306	$ 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	$ 3,463
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	21
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	0
Financing Receivable, Revolving	2,771
Loans and Leases Receivable, Net of Deferred Income	$ 6,442	$ 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	$ 646
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	6,545
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	0
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	229
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	313
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	2,592
Financing Receivable, Revolving	0
Loans and Leases Receivable, Net of Deferred Income	$ 10,325	$ 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	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	$ 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	951
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	401
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	64
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	402
Financing Receivable, Revolving	0
Loans and Leases Receivable, Net of Deferred Income	$ 2,864	$ 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	$ 2,316
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	0
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	0
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	0
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	0
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	0
Financing Receivable, Revolving	2,356
Loans and Leases Receivable, Net of Deferred Income	$ 4,672	$ 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	$ 470
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	1,011
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	$ 1,481	$ 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	6.20
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	5.46
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	7.24
Revolving Credit Facility [Member] | Construction Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade For Loans | Grade	6.10
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	6.41
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	$ 68,629
Weighted Average Risk Grade For Loans | Grade	7.52
Revolving Loans Converted to Term [Member] | Commercial and Industrial Total Energy Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Revolving, Converted to Term Loan	$ 49,469
Weighted Average Risk Grade For Loans | Grade	6.25
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	$ 109,298
Weighted Average Risk Grade For Loans | Grade	6.44
Revolving Loans Converted to Term [Member] | Construction Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Revolving, Converted to Term Loan	$ 4,247
Weighted Average Risk Grade For Loans | Grade	5.01
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	$ 113,545
Weighted Average Risk Grade For Loans | Grade	6.39
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	$ 54,235
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	49,185
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	106,450
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	4,247
Revolving Loans Converted to Term [Member] | Risk Grade Nine [Member] | Commercial Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Revolving, Converted to Term Loan	5,662
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	39
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	2,848
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	2,093
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	58
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	4,846
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	747
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	187
Revolving Loans Converted to Term [Member] | Risk Grade Twelve [Member] | Commercial Real Estate Buildings Land And Other Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Revolving, Converted to Term Loan	0
Revolving Loans Converted to Term [Member] | Risk Grade Twelve [Member] | Construction Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Revolving, Converted to Term Loan	0
Revolving Loans Converted to Term [Member] | Risk Grade Thirteen [Member] | Commercial Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Revolving, Converted to Term Loan	1,046
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	6.28
2022 [Member] | Commercial and Industrial Total Energy Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade For Loans | Grade	6.09
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	7.01
2022 [Member] | Construction Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade For Loans | Grade	7.10
2022 [Member] | Commercial Real Estate Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade For Loans | Grade	7.03
2021 [Member] | Commercial Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade For Loans | Grade	7.03
2021 [Member] | Commercial and Industrial Total Energy Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade For Loans | Grade	5.66
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	7.23
2021 [Member] | Construction Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade For Loans | Grade	7.12
2021 [Member] | Commercial Real Estate Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade For Loans | Grade	7.19
2020 [Member] | Commercial Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade For Loans | Grade	6.10
2020 [Member] | Commercial and Industrial Total Energy Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade For Loans | Grade	7.69
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	7.16
2020 [Member] | Construction Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade For Loans | Grade	6.64
2020 [Member] | Commercial Real Estate Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade For Loans | Grade	7.09
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	8.63
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	7.25
2019 [Member] | Construction Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade For Loans | Grade	8.21
2019 [Member] | Commercial Real Estate Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade For Loans | Grade	7.36
2018 [Member] | Commercial Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade For Loans | Grade	7.01
2018 [Member] | Commercial and Industrial Total Energy Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade For Loans | Grade	8.30
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	7.28
2018 [Member] | Construction Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade For Loans | Grade	6.21
2018 [Member] | Commercial Real Estate Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade For Loans | Grade	7.28
Prior Years [Member] | Commercial Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade For Loans | Grade	5.79
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	7.17
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	6.95
Prior Years [Member] | Construction 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 Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade For Loans | Grade	6.95

Loans - Weighted Average Risk G

Loans - Weighted Average Risk Grades for All Commercial Loans by Class (Detail) $ in Thousands	Jun. 30, 2022 USD ($) Grade	Dec. 31, 2021 USD ($) Grade
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Net of Deferred Income	$ 16,736,026	$ 16,336,397
Commercial Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade | Grade	6.38	6.22
Loans and Leases Receivable, Net of Deferred Income	$ 5,539,277	$ 5,364,954
Commercial and Industrial Total Energy Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade | Grade	5.82	6.06
Loans and Leases Receivable, Net of Deferred Income	$ 987,925	$ 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	7.12	7.22
Loans and Leases Receivable, Net of Deferred Income	$ 6,520,280	$ 6,272,339
Construction Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade | Grade	6.96	7.06
Loans and Leases Receivable, Net of Deferred Income	$ 1,535,808	$ 1,304,271
Commercial Real Estate Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade | Grade	7.09	7.19
Loans and Leases Receivable, Net of Deferred Income	$ 8,056,088	$ 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	6.23	6.01
Loans and Leases Receivable, Net of Deferred Income	$ 5,276,748	$ 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	5.57	5.78
Loans and Leases Receivable, Net of Deferred Income	$ 941,153	$ 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	6.90	6.91
Loans and Leases Receivable, Net of Deferred Income	$ 5,969,393	$ 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	6.86	6.99
Loans and Leases Receivable, Net of Deferred Income	$ 1,479,710	$ 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	$ 164,939	$ 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	$ 14,235	$ 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	$ 306,070	$ 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	$ 15,003	$ 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	$ 56,470	$ 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	$ 885	$ 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	$ 170,464	$ 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	$ 41,095	$ 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	$ 29,950	$ 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	$ 20,538	$ 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	$ 62,547	$ 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	$ 8,306	$ 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	$ 6,442	$ 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	$ 10,325	$ 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	$ 0	$ 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	$ 2,864	$ 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	$ 4,672	$ 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	$ 1,481	$ 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	Jun. 30, 2022	Dec. 31, 2021
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Net of Deferred Income	$ 16,736,026	$ 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	1,561,035	1,410,790
Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Net of Deferred Income	499,782	$ 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	50,696
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	6,921
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	4,443
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	21,638
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	1,268
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	598
Financial Asset, Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	72,334
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	8,189
Financial Asset, Past Due | Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	5,041
Financial Asset, Not Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	16,663,692
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	1,552,846
Financial Asset, Not Past Due | Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	494,741
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	593,388
Revolving Credit Facility [Member] | Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Net of Deferred Income	391,745
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	602
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	32
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	247
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	849
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	32
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	592,539
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	391,713
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	10,557
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	24,605
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	1,665
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	2,210
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	0
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	129
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	1,665
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	2,339
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	8,892
Revolving Loans Converted to Term [Member] | Financial Asset, Not Past Due | Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	22,266
2022 [Member] | Total consumer real estate loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Net of Deferred Income	154,318
2022 [Member] | Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Net of Deferred Income	33,643
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	140
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	1,974
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	439
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	140
2022 [Member] | Financial Asset, Past Due | Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	2,413
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	154,178
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	31,230
2021 [Member] | Total consumer real estate loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Net of Deferred Income	324,376
2021 [Member] | Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Net of Deferred Income	30,781
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	287
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	69
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	0
2021 [Member] | Financial Asset, Past Due | Total consumer real estate loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	287
2021 [Member] | Financial Asset, Past Due | Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	69
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	324,089
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	30,712
2020 [Member] | Total consumer real estate loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Net of Deferred Income	211,520
2020 [Member] | Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Net of Deferred Income	10,862
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	387
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	64
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	0
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	387
2020 [Member] | Financial Asset, Past Due | Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	64
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	211,133
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	10,798
2019 [Member] | Total consumer real estate loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Net of Deferred Income	81,023
2019 [Member] | Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Net of Deferred Income	4,229
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	668
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	44
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	4
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	19
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	672
2019 [Member] | Financial Asset, Past Due | Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	63
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	80,351
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	4,166
2018 [Member] | Total consumer real estate loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Net of Deferred Income	44,371
2018 [Member] | Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Net of Deferred Income	1,830
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	401
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	5
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	142
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	11
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	543
2018 [Member] | Financial Asset, Past Due | Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	16
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	43,828
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	1,814
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	141,482
Prior Years [Member] | Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Net of Deferred Income	2,087
Prior Years [Member] | Financing Receivables, 30 to 89 Days Past Due [Member] | Total consumer real estate loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	2,771
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	45
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	875
Prior Years [Member] | Financial Asset, Equal to or Greater than 90 Days Past Due [Member] | Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	0
Prior Years [Member] | Financial Asset, Past Due | Total consumer real estate loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	3,646
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	45
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	137,836
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	$ 2,042

Loans Loans - Revolving Loans C

Loans Loans - Revolving Loans Converted to Term (Details) - Revolving Loans Converted to Term [Member] - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Accounts, Notes, Loans and Financing Receivable [Line Items]
Remaining Revolving Loans Converted to Term During Period	$ 30,139	$ 32,766	$ 44,746	$ 75,732
Commercial Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Remaining Revolving Loans Converted to Term During Period	16,518	22,111	21,973	31,561
Commercial and Industrial Total Energy Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Remaining Revolving Loans Converted to Term During Period	247	294	247	6,177
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	10,681	8,195	10,726	31,321
Construction Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Remaining Revolving Loans Converted to Term During Period	13	0	4,248	0
Total consumer real estate loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Remaining Revolving Loans Converted to Term During Period	888	205	1,684	977
Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Remaining Revolving Loans Converted to Term During Period	$ 1,792	$ 1,961	$ 5,868	$ 5,696

Loans Loans - Allowance for C_2

Loans Loans - Allowance for Credit Loss By Loan Class Calculated in Accordance With CECL Methodology (Details) - USD ($) $ in Thousands	Jun. 30, 2022	Mar. 31, 2022	Dec. 31, 2021	Jun. 30, 2021	Mar. 31, 2021	Dec. 31, 2020
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, Allowance for Credit Loss	$ 239,632		$ 248,666
Commercial Portfolio Segment [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, Allowance for Credit Loss	87,270	$ 87,026	72,091	$ 65,271	$ 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	16,267	15,422	17,217	28,010	33,472	39,553
Commercial Real Estate Portfolio Segment [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, Allowance for Credit Loss	117,106	128,954	144,936	147,993	144,440	134,892
Total consumer real estate loans [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, Allowance for Credit Loss	6,854	6,359	6,585	6,154	5,636	7,926
Consumer Loan [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, Allowance for Credit Loss	12,135	9,074	7,837	7,860	6,818	6,963
Loans Receivable [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, Allowance for Credit Loss	239,632	$ 246,835	248,666	$ 255,288	$ 261,258	$ 263,177
Modeled Expected Credit Losses [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, Allowance for Credit Loss	91,223		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	48,776		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	6,106		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	20,093		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	6,639		6,484
Modeled Expected Credit Losses [Member] | Consumer Loan [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, Allowance for Credit Loss	9,609		6,397
Q-factor adjustments [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, Allowance for Credit Loss	137,314		149,348
Q-factor adjustments [Member] | Commercial Portfolio Segment [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, Allowance for Credit Loss	35,134		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	3,989		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	95,532		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	133		65
Q-factor adjustments [Member] | Consumer Loan [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, Allowance for Credit Loss	2,526		1,440
Specific Valuation Allowances [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, Allowance for Credit Loss	11,095		16,452
Specific Valuation Allowances [Member] | Commercial Portfolio Segment [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, Allowance for Credit Loss	3,360		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	6,172		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	1,481		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	82		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		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning balance			$ 248,666
Ending balance	$ 239,632		239,632
Commercial Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning balance	87,026	$ 70,892	72,091	$ 73,843
Credit loss, expense (reversal)	942	(5,901)	18,503	(7,866)
Charge-offs	(1,891)	(685)	(5,346)	(2,874)
Recoveries	1,193	965	2,022	2,168
Net charge-offs	(698)	280	(3,324)	(706)
Ending balance	87,270	65,271	87,270	65,271
Commercial and Industrial Total Energy Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning balance	15,422	33,472	17,217	39,553
Credit loss, expense (reversal)	427	(5,527)	(1,617)	(11,328)
Charge-offs	0	0	(371)	(1,433)
Recoveries	418	65	1,038	1,218
Net charge-offs	418	65	667	(215)
Ending balance	16,267	28,010	16,267	28,010
Commercial Real Estate Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning balance	128,954	144,440	144,936	134,892
Credit loss, expense (reversal)	(12,232)	3,654	(27,841)	12,576
Charge-offs	0	(137)	(702)	(137)
Recoveries	384	36	713	662
Net charge-offs	384	(101)	11	525
Ending balance	117,106	147,993	117,106	147,993
Total consumer real estate loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning balance	6,359	5,636	6,585	7,926
Credit loss, expense (reversal)	583	611	557	(2,111)
Charge-offs	(131)	(388)	(362)	(672)
Recoveries	43	295	74	1,011
Net charge-offs	(88)	(93)	(288)	339
Ending balance	6,854	6,154	6,854	6,154
Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning balance	9,074	6,818	7,837	6,963
Credit loss, expense (reversal)	5,884	2,784	10,466	4,350
Charge-offs	(5,322)	(3,882)	(11,093)	(7,942)
Recoveries	2,499	2,140	4,925	4,489
Net charge-offs	(2,823)	(1,742)	(6,168)	(3,453)
Ending balance	12,135	7,860	12,135	7,860
Loans Receivable [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning balance	246,835	261,258	248,666	263,177
Credit loss, expense (reversal)	(4,396)	(4,379)	68	(4,379)
Charge-offs	(7,344)	(5,092)	(17,874)	(13,058)
Recoveries	4,537	3,501	8,772	9,548
Net charge-offs	(2,807)	(1,591)	(9,102)	(3,510)
Ending balance	$ 239,632	$ 255,288	$ 239,632	$ 255,288

Loans - Investment in Loans Rel

Loans - Investment in Loans Related to Allowance for Loan Losses by Portfolio Segment Disaggregated Based on Impairment Methodology (Detail) - USD ($) $ in Thousands	Jun. 30, 2022	Dec. 31, 2021
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Net of Deferred Income	$ 16,736,026	$ 16,336,397
Commercial Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Net of Deferred Income	5,539,277	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	987,925	1,077,792
Paycheck Protection Program [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Net of Deferred Income	91,919	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	6,520,280	6,272,339
Construction Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Net of Deferred Income	1,535,808	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	1,561,035	1,410,790
Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Net of Deferred Income	499,782	477,369
Specific Valuation Allowances [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Specific Allocations	11,095	16,452
Specific Valuation Allowances [Member] | Commercial Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Specific Allocations	3,360	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	6,172	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	1,481	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	82	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	50,584	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	12,539	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	15,906	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	21,205	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	934	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	Jun. 30, 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	Jun. 30, 2022	Dec. 31, 2021
Finite-Lived Intangible Assets [Line Items]
Other intangible assets, net	$ 589	$ 866
Core deposits [Member]
Finite-Lived Intangible Assets [Line Items]
Other intangible assets, net	479	718
Customer relationships [Member]
Finite-Lived Intangible Assets [Line Items]
Other intangible assets, net	$ 110	$ 148

Goodwill and Other Intangible_5

Goodwill and Other Intangible Assets - Estimated Aggregate Future Amortization Expense for Intangible Assets (Detail) - USD ($) $ in Thousands	Jun. 30, 2022	Dec. 31, 2021
Goodwill and Intangible Assets Disclosure [Abstract]
Remainder of 2022	$ 204
2023	282
2024	87
2025	11
2026	5
Future Amortization Expense, Total	$ 589	$ 866

Deposits - Schedule of Deposits

Deposits - Schedule of Deposits (Detail) - USD ($) $ in Thousands	Jun. 30, 2022	Dec. 31, 2021
Deposit [Line Items]
Non-interest-bearing demand deposits	$ 18,783,931	$ 18,423,018
Interest-bearing Domestic Deposit, Savings	12,309,066	11,930,959
Interest-bearing Domestic Deposit, Money Market	12,989,902	11,228,815
Interest-bearing Domestic Deposit, Time Deposits	1,518,866	1,112,904
Total interest-bearing deposit	26,817,834	24,272,678
Total deposits	$ 45,601,765	$ 42,695,696

Deposits - Additional Informati

Deposits - Additional Information About Corporation's Deposits (Detail) - USD ($) $ in Thousands	Jun. 30, 2022	Dec. 31, 2021
Deposit Liability [Line Items]
Deposits from foreign sources (primarily Mexico)	$ 1,090,169	$ 993,479
Non-interest-bearing public funds deposits	18,783,931	18,423,018
Interest-bearing public funds deposits	26,817,834	24,272,678
Total deposits not covered by deposit insurance	25,810,407	24,125,359
Time deposits not covered by deposit insurance	364,486	238,608
Public Funds [Member]
Deposit Liability [Line Items]
Non-interest-bearing public funds deposits	681,205	1,235,026
Interest-bearing public funds deposits	$ 837,427	$ 810,863

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021	Dec. 31, 2021
Lessee, Operating Lease, Liability, Payments, Due	$ 8,400	$ 8,000	$ 16,400	$ 16,100
Significant change in expected future minimum lease payments since year end			0
Premises and Equipment
Operating Lease, Right-of-Use Asset	278,300		278,300		$ 281,400
Other Liabilities [Member]
Operating Lease, Liability	$ 310,500		$ 310,500		$ 313,400

Commitments and Contingencies_2

Commitments and Contingencies - Financial Instruments with Off-Balance-Sheet Risk (Detail) - USD ($) $ in Thousands	Jun. 30, 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	$ 327,847	$ 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	1,890	2,072
Commitments to Extend Credit [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Financial instruments with off- balance-sheet risk	$ 10,771,940	$ 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		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Commitments and Contingencies Disclosure [Abstract]
Off-Balance Sheet, Credit Loss, Liability	$ 45,850	$ 44,217	$ 50,314	$ 44,152
Credit loss expense (benefit)	4,396	4,379	(68)	4,444
Off-Balance Sheet, Credit Loss, Liability	$ 50,246	$ 48,596	$ 50,246	$ 48,596

Commitments and Contingencies_3

Commitments and Contingencies Commitments and Contingencies - Components of Lease Commitments Expense (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Commitments and Contingencies Disclosure [Abstract]
Operating Lease, Right-of-Use Asset, Amortization Expense	$ 8,209	$ 8,129	$ 16,314	$ 16,412
Short-term lease expense	490	530	1,103	734
Non-lease components (including taxes, insurance, common maintenance, etc.)	2,748	2,337	5,768	5,341
Total operating lease expense, excluding rent	$ 11,447	$ 10,996	$ 23,185	$ 22,487

Capital and Regulatory Matter_2

Capital and Regulatory Matters - Additional Information (Detail) $ / shares in Units, $ in Millions			3 Months Ended	6 Months Ended		12 Months Ended
	Jan. 26, 2022 USD ($)	Nov. 19, 2020 USD ($)	Mar. 31, 2022	Jun. 30, 2022 USD ($) quarter $ / shares shares	Jun. 30, 2021 shares	Dec. 31, 2021 USD ($) $ / shares shares
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
CECL Transition Amount				$ 46.2		$ 61.6
Treasury Stock, Shares, Acquired | shares				7,459	11,625
Maximum dividends available without prior regulatory approval				$ 447.3
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				$ 150
Preferred stock, par value | $ / shares				$ 0.01		$ 0.01
Preferred Stock, Liquidation Preference Per Share | $ / shares				$ 1,000		$ 1,000
Number of Preferred Stock equivalent depositary shares | shares				40
Payments of Stock Issuance Costs		$ 4.5
Proceeds from Issuance of Preferred Stock and Preference Stock		$ 145.5
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				$ 145.5		$ 145.5
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		120
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
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%
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		$ 100

Capital and Regulatory Matter_3

Capital and Regulatory Matters - Actual and Required Capital Ratios (Detail) - USD ($) $ in Thousands	Jun. 30, 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	$ 3,485,759	$ 3,371,043
Common Equity Tier 1 to Risk-Weighted Assets, Actual , Ratio	12.64%	13.13%
Common Equity Tier 1 to Risk-Weighted Assets, Minimum Capital Required - Basel III Fully Phased-In, Capital Amount	$ 1,930,703	$ 1,796,549
Common Equity Tier 1 to Risk-Weighted Assets, Minimum Capital Required - Basel III Fully Phased In, Ratio	7%	7%
Common Equity Tier 1 to Risk-Weighted Assets, Required To Be Considered Well Capitalized, Capital Amount	$ 1,792,796	$ 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	$ 3,631,211	$ 3,516,495
Tier 1 Capital to Risk-Weighted Assets, Actual, Ratio	13.17%	13.70%
Tier 1 Capital to Risk-Weighted Assets, Minimum Capital Required - Basel III Fully Phased-In, Capital Amount	$ 2,344,425	$ 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	$ 2,206,518	$ 2,053,198
Tier 1 Capital to Risk-Weighted Assets, Required to be Considered Well Capitalized, Ratio	8%	8%
Total Capital to Risk-Weighted Assets, Actual, Capital Amount	$ 4,069,206	$ 3,966,244
Total Capital to Risk-Weighted Assets, Actual, Ratio	14.75%	15.45%
Total Capital to Risk-Weighted Assets, Minimum Capital Required - Basel III Fully Phased-In, Capital Amount	$ 2,896,055	$ 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	$ 2,758,148	$ 2,566,498
Total Capital to Risk-Weighted Assets, Required to be Considered Well Capitalized, Ratio	10%	10%
Leverage Ratio, Actual, Capital Amount	$ 3,631,211	$ 3,516,495
Leverage Ratio, Actual, Ratio	7.03%	7.34%
Leverage Ratio, Minimum Capital Required - Basel III Fully Phased-In, Capital Amount	$ 2,067,513	$ 1,917,533
Leverage Ratio, Minimum Capital Required - Basel III Fully Phased-In, Ratio	4%	4%
Leverage Ratio, Required to be Considered Well Capitalized, Capital Amount	$ 2,584,391	$ 2,396,917
Leverage Ratio, Required to be Considered Well Capitalized, Ratio	5%	5%
Frost Bank [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Common Equity Tier 1 to Risk-Weighted Assets, Actual, Capital Amount	$ 3,423,585	$ 3,261,532
Common Equity Tier 1 to Risk-Weighted Assets, Actual , Ratio	12.42%	12.72%
Common Equity Tier 1 to Risk-Weighted Assets, Minimum Capital Required - Basel III Fully Phased-In, Capital Amount	$ 1,929,368	$ 1,795,221
Common Equity Tier 1 to Risk-Weighted Assets, Minimum Capital Required - Basel III Fully Phased In, Ratio	7%	7%
Common Equity Tier 1 to Risk-Weighted Assets, Required To Be Considered Well Capitalized, Capital Amount	$ 1,791,556	$ 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	$ 3,423,585	$ 3,261,532
Tier 1 Capital to Risk-Weighted Assets, Actual, Ratio	12.42%	12.72%
Tier 1 Capital to Risk-Weighted Assets, Minimum Capital Required - Basel III Fully Phased-In, Capital Amount	$ 2,342,804	$ 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	$ 2,204,992	$ 2,051,681
Tier 1 Capital to Risk-Weighted Assets, Required to be Considered Well Capitalized, Ratio	8%	8%
Total Capital to Risk-Weighted Assets, Actual, Capital Amount	$ 3,661,580	$ 3,491,281
Total Capital to Risk-Weighted Assets, Actual, Ratio	13.28%	13.61%
Total Capital to Risk-Weighted Assets, Minimum Capital Required - Basel III Fully Phased-In, Capital Amount	$ 2,894,052	$ 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	$ 2,756,240	$ 2,564,601
Total Capital to Risk-Weighted Assets, Required to be Considered Well Capitalized, Ratio	10%	10%
Leverage Ratio, Actual, Capital Amount	$ 3,423,585	$ 3,261,532
Leverage Ratio, Actual, Ratio	6.62%	6.80%
Leverage Ratio, Minimum Capital Required - Basel III Fully Phased-In, Capital Amount	$ 2,067,942	$ 1,917,679
Leverage Ratio, Minimum Capital Required - Basel III Fully Phased-In, Ratio	4%	4%
Leverage Ratio, Required to be Considered Well Capitalized, Capital Amount	$ 2,584,928	$ 2,397,099
Leverage Ratio, Required to be Considered Well Capitalized, Ratio	5%	5%

Derivative Financial Instrume_3

Derivative Financial Instruments - Additional Information (Detail) - USD ($) $ in Thousands	Jun. 30, 2022	Dec. 31, 2021
Derivative [Line Items]
Weighted-average strike rate for outstanding interest rate caps	3.28%
Approximate credit exposure related to swaps with bank customers	$ 198,100
Cash collateral for borrowed securities deposited with other financial institutions	212,400
Interest rate swaps with upstream financial institution counterparties [Member]
Derivative [Line Items]
Approximate credit exposure related to swaps with bank customers	41,500
Not Designated as Hedging Instrument [Member] | Financial Institution Counterparties Loan Lease Interest Rate Swaps Liabilities [Member]
Derivative [Line Items]
Estimated fair value of derivative contracts cleared through Chicago Mercantile Exchange	$ 0	$ 0

Derivative Financial Instrume_4

Derivative Financial Instruments - Schedule of Notional Amounts and Estimated Fair Values of Interest Rate Derivative Contracts Outstanding (Detail) - USD ($) $ in Thousands	Jun. 30, 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	$ 1,743	$ 0
Estimated Fair Value	18	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	0	2,426
Estimated Fair Value	0	(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	904,706	247,592
Estimated Fair Value	27,908	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	244,663	928,756
Estimated Fair Value	(2,489)	(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	269,389	270,431
Estimated Fair Value	10,209	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	244,663	928,756
Estimated Fair Value	3,350	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	904,706	247,592
Estimated Fair Value	(45,542)	(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	269,389	270,431
Estimated Fair Value	$ (10,209)	$ (3,239)

Derivative Financial Instrume_5

Derivative Financial Instruments - Schedule of Weighted-Average Rates Paid and Received for Interest Rate Swaps Outstanding (Detail)	Jun. 30, 2022
Weighted Average Interest Rate Paid [Member]
Short-duration insurance contracts, discounted liabilities [Line Items]
Fair value hedge loan/lease interest rate swaps	1.58%
Weighted-Average Interest Rate Received [Member]
Short-duration insurance contracts, discounted liabilities [Line Items]
Fair value hedge loan/lease interest rate swaps	1.06%
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	3.71%
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	2.87%
Customer Counterparties [Member] | Weighted Average Interest Rate Paid [Member]
Short-duration insurance contracts, discounted liabilities [Line Items]
Non-hedging interest rate swaps – customer counterparties	2.87%
Customer Counterparties [Member] | Weighted-Average Interest Rate Received [Member]
Short-duration insurance contracts, discounted liabilities [Line Items]
Non-hedging interest rate swaps – customer counterparties	3.71%

Derivative Financial Instrume_6

Derivative Financial Instruments - Schedule of Notional Amounts and Estimated Fair Values of Commodity Derivative Positions (Detail) bbl in Thousands, MMBTU in Thousands, $ in Thousands	Jun. 30, 2022 USD ($) MMBTU bbl	Dec. 31, 2021 USD ($) MMBTU bbl
Financial Institution Counterparties [Member] | Oil Commodity Derivative [Member]
Derivative Instruments [Line Items]
Oil/Natural Gas Derivative Assets, Notional Amount | bbl	4,173	4,809
Oil/Natural Gas Derivative Liabilities, Notional Amount | bbl	9,125	7,032
Oil/Natural Gas Derivative Assets, Estimated Fair Value	$ 20,653	$ 14,721
Oil/Natural Gas Derivative Liabilities, Estimated Fair Value	$ (181,161)	$ (73,594)
Financial Institution Counterparties [Member] | Natural Gas Commodity Derivative [Member]
Derivative Instruments [Line Items]
Oil/Natural Gas Derivative Assets, Notional Amount | MMBTU	11,753	15,947
Oil/Natural Gas Derivative Liabilities, Notional Amount | MMBTU	21,557	29,446
Oil/Natural Gas Derivative Assets, Estimated Fair Value	$ 3,181	$ 4,143
Oil/Natural Gas Derivative Liabilities, Estimated Fair Value	$ (38,990)	$ (21,249)
Customer Counterparties [Member] | Oil Commodity Derivative [Member]
Derivative Instruments [Line Items]
Oil/Natural Gas Derivative Assets, Notional Amount | bbl	9,606	7,046
Oil/Natural Gas Derivative Liabilities, Notional Amount | bbl	3,692	4,796
Oil/Natural Gas Derivative Assets, Estimated Fair Value	$ 182,274	$ 74,437
Oil/Natural Gas Derivative Liabilities, Estimated Fair Value	$ (20,306)	$ (14,294)
Customer Counterparties [Member] | Natural Gas Commodity Derivative [Member]
Derivative Instruments [Line Items]
Oil/Natural Gas Derivative Assets, Notional Amount | MMBTU	21,557	29,446
Oil/Natural Gas Derivative Liabilities, Notional Amount | MMBTU	11,753	15,947
Oil/Natural Gas Derivative Assets, Estimated Fair Value	$ 39,110	$ 21,456
Oil/Natural Gas Derivative Liabilities, Estimated Fair Value	$ (3,181)	$ (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	Jun. 30, 2022 USD ($)	Jun. 30, 2022 EUR (€)	Jun. 30, 2022 CAD ($)	Dec. 31, 2021 USD ($)	Dec. 31, 2021 EUR (€)	Dec. 31, 2021 CAD ($)
Financial Institution Counterparties [Member] | GBP Foreign Exchange Forward
Derivative Instruments [Line Items]
Forward Contracts – Assets Estimated Fair Value	$ 16			$ 29
Forward Contracts - Liability Estimated Fair Value	(174)			0
Financial Institution Counterparties [Member] | Foreign Exchange Forward [Member]
Derivative Instruments [Line Items]
Forward Contracts – Assets Estimated Fair Value	9			0
Financial Institution Counterparties [Member] | Other Assets [Member] | Non Designated as Hedging Instrument [Member]
Derivative Instruments [Line Items]
Forward Contracts – Assets Notional Amount		€ 6,400	$ 658		€ 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 | €		6,400			0
Customer Counterparties [Member] | GBP Foreign Exchange Forward
Derivative Instruments [Line Items]
Forward Contracts – Assets Estimated Fair Value	174			0
Forward Contracts - Liability Estimated Fair Value	(16)			(55)
Customer Counterparties [Member] | Foreign Exchange Forward [Member]
Derivative Instruments [Line Items]
Forward Contracts – Assets Estimated Fair Value	0			4
Forward Contracts - Liability Estimated Fair Value	$ (5)			$ 0
Customer Counterparties [Member] | Other Assets [Member] | Non Designated as Hedging Instrument [Member]
Derivative Instruments [Line Items]
Forward Contracts – Assets Notional Amount		6,400	0		0	658
Customer Counterparties [Member] | Other Liabilities [Member] | Non Designated as Hedging Instrument [Member]
Derivative Instruments [Line Items]
Forward Contracts – Liability Notional Amount		€ 6,400	$ 658		€ 1,900	$ 0

Derivative Financial Instrume_8

Derivative Financial Instruments - Schedule of Amounts Related to Interest Rate Derivatives Designated as Hedges of Fair Value (Detail) - Designated as Hedging Instrument [Member] - Commercial Loan/Lease Interest Rate Swaps [Member] - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Interest Income on Loans [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of gain (loss) included in income	$ (5)	$ (25)	$ (18)	$ (53)
Other Non-Interest Expense [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of gain (loss) included in income	$ 3	$ 2	$ 5	$ 5

Derivative Financial Instrume_9

Derivative Financial Instruments - Schedule of Amounts Related to Non-Hedging Interest Rate and Commodity Derivatives (Detail) - Non Designated as Hedging Instrument [Member] - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 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)	$ 515	$ 141	$ 1,031	$ 1,728
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	0	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)	649	969	1,578	2,123
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)	$ 45	$ 0	$ 63	$ 30

Balance Sheet Offsetting - Fina

Balance Sheet Offsetting - Financial Instruments Eligible for Offset Consolidated Balance Sheet (Detail) - USD ($) $ in Thousands	Jun. 30, 2022	Dec. 31, 2021
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Gross Amount Recognized, Derivatives, Financial Assets	$ 61,994	$ 23,339
Gross Amount Offset, Derivatives, Financial assets	0	0
Net Amount Recognized, Derivatives, Financial assets	61,994	23,339
Gross Amount Recognized, Resell agreements, Financial assets	9,650	7,903
Gross Amount Offset, Resell agreements, Financial assets	0	0
Net Amount Recognized, Resell agreements, Financial assets	9,650	7,903
Gross Amount Recognized, Financial assets	71,644	31,242
Gross Amount Offset, Financial assets	0	0
Net Amount Recognized, Financial assets	71,644	31,242
Gross Amount Recognized, Derivatives, Financial Liabilities	222,814	114,019
Gross Amount Offset, Derivatives, Financial liabilities	0	0
Net Amount Recognized, Derivatives, Financial liabilities	222,814	114,019
Gross Amount Recognized, Repurchase agreements, Financial liabilities	1,664,685	2,740,799
Gross Amount Offset, Repurchase agreements, Financial liabilities	0	0
Net Amount Recognized, Repurchase agreements, Financial liabilities	1,664,685	2,740,799
Gross Amount Recognized, Financial liabilities	1,887,499	2,854,818
Gross Amount Offset, Financial liabilities	0	0
Net Amount Recognized, Financial Liabilities	1,887,499	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	38,135	4,446
Gross Amount Offset, Derivatives, Financial assets	0	0
Net Amount Recognized, Derivatives, Financial assets	38,135	4,446
Gross Amount Recognized, Derivatives, Financial Liabilities	2,489	19,176
Gross Amount Offset, Derivatives, Financial liabilities	0	0
Net Amount Recognized, Derivatives, Financial liabilities	2,489	19,176
Commodity swaps and options [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Gross Amount Recognized, Derivatives, Financial Assets	23,834	18,864
Gross Amount Offset, Derivatives, Financial assets	0	0
Net Amount Recognized, Derivatives, Financial assets	23,834	18,864
Gross Amount Recognized, Derivatives, Financial Liabilities	220,151	94,843
Gross Amount Offset, Derivatives, Financial liabilities	0	0
Net Amount Recognized, Derivatives, Financial liabilities	220,151	$ 94,843
Foreign currency forward contracts [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Gross Amount Recognized, Derivatives, Financial Assets	25
Gross Amount Offset, Derivatives, Financial assets	0
Net Amount Recognized, Derivatives, Financial assets	25
Gross Amount Recognized, Derivatives, Financial Liabilities	174
Gross Amount Offset, Derivatives, Financial liabilities	0
Net Amount Recognized, Derivatives, Financial liabilities	$ 174

Balance Sheet Offsetting - Fi_2

Balance Sheet Offsetting - Financial Instruments Derivative Assets Liabilities and Resell Agreements Net of Amount Not Offset (Detail) - USD ($) $ in Thousands	Jun. 30, 2022	Dec. 31, 2021
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Net Amount Recognized, Derivatives, Financial Assets	$ 61,994	$ 23,339
Gross Amounts Not Offset, Financial Instruments, Total Derivatives, Financial Assets	(51,552)	(23,339)
Gross Amount Not Offset Collateral, Derivatives, Financial Assets	(10,442)	0
Net Amount, Derivatives, Financial Assets	0	0
Net Amount Recognized, Resell agreements, Financial Assets	9,650	7,903
Gross Amounts Not Offset Financial Instruments, Resell Agreements	0	0
Gross Amounts Not Offset Collateral, Resell Agreements, Financial Assets	(9,650)	(7,903)
Net Amount, Financial Assets, Resell Agreements	0	0
Net Amount Recognized, Total Financial Assets	71,644	31,242
Gross Amounts Not Offset Collateral, Financial Assets	(20,092)	(7,903)
Net Amount, Financial Assets	0	0
Net Amount Recognized, Derivatives, Financial Liabilities	222,814	114,019
Gross Amounts Not Offset Financial Instruments, Total Derivatives, Financial Liabilities	(51,552)	(23,339)
Gross Amounts Not Offset Collateral, Derivatives, Financial Liabilities	(170,983)	(90,573)
Net Amount, Derivatives, Financial Liabilities	279	107
Net Amount Recognized, Repurchase Agreements, Financial Liabilities	1,664,685	2,740,799
Gross Amounts Not Offset Financial Instruments, Repurchase Agreements, Financial Liabilities	0	0
Gross Amounts Not Offset Collateral, Repurchase Agreements, Financial Liabilities	(1,664,685)	(2,740,799)
Net Amount, Repurchase Agreements, Financial Liabilities	0	0
Net Amount Recognized, Financial Liabilities	1,887,499	2,854,818
Gross Amounts Not Offset Collateral, Financial Liabilities	(1,835,668)	(2,831,372)
Net Amount, Financial Liabilities	279	107
Counterparty A [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Net Amount Recognized, Derivatives, Financial Assets	41	6
Gross Amounts Not Offset, Financial Instruments, Total Derivatives, Financial Assets	(41)	(6)
Gross Amount Not Offset Collateral, Derivatives, Financial Assets	0	0
Net Amount, Derivatives, Financial Assets	0	0
Net Amount Recognized, Derivatives, Financial Liabilities	1,726	3,870
Gross Amounts Not Offset Financial Instruments, Total Derivatives, Financial Liabilities	(41)	(6)
Gross Amounts Not Offset Collateral, Derivatives, Financial Liabilities	(1,571)	(3,864)
Net Amount, Derivatives, Financial Liabilities	114	0
Counterparty B [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Net Amount Recognized, Derivatives, Financial Assets	25,962	7,655
Gross Amounts Not Offset, Financial Instruments, Total Derivatives, Financial Assets	(25,962)	(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	50,901	28,130
Gross Amounts Not Offset Financial Instruments, Total Derivatives, Financial Liabilities	(25,962)	(7,655)
Gross Amounts Not Offset Collateral, Derivatives, Financial Liabilities	(24,939)	(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 Assets	16
Gross Amounts Not Offset, Financial Instruments, Total Derivatives, Financial Assets	(16)
Gross Amount Not Offset Collateral, Derivatives, Financial Assets	0
Net Amount, Derivatives, Financial Assets	0
Net Amount Recognized, Derivatives, Financial Liabilities	174	9
Gross Amounts Not Offset Financial Instruments, Total Derivatives, Financial Liabilities	(16)	0
Gross Amounts Not Offset Collateral, Derivatives, Financial Liabilities	(10)	(9)
Net Amount, Derivatives, Financial Liabilities	148	0
Other Counterparties [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Net Amount Recognized, Derivatives, Financial Assets	35,975	15,678
Gross Amounts Not Offset, Financial Instruments, Total Derivatives, Financial Assets	(25,533)	(15,678)
Gross Amount Not Offset Collateral, Derivatives, Financial Assets	(10,442)	0
Net Amount, Derivatives, Financial Assets	0	0
Net Amount Recognized, Derivatives, Financial Liabilities	170,013	82,010
Gross Amounts Not Offset Financial Instruments, Total Derivatives, Financial Liabilities	(25,533)	(15,678)
Gross Amounts Not Offset Collateral, Derivatives, Financial Liabilities	(144,463)	(66,225)
Net Amount, Derivatives, Financial Liabilities	$ 17	$ 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	Jun. 30, 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	$ 1,664,685	$ 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	1,664,685	2,740,799
Securities Sold under Agreements to Repurchase, Gross	1,664,685	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	834,063	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	834,063	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	830,622	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	$ 830,622	$ 1,398,208

Stock-Based Compensation Stock-

Stock-Based Compensation Stock-Based Compensation - Narrative (Details)	Jun. 30, 2022 shares
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	788,070

Stock-Based Compensation - Summ

Stock-Based Compensation - Summary of Activity in Corporation's Active Stock Plans (Detail) - $ / shares	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock options exercised, Number of Shares	(28,832)	(114,252)	(144,262)	(628,076)
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
Granted, Number of Units			5,382
Stock Awards exercised/vested, Number of Shares			(16,022)
Ending Balance, Number of Shares/Units	45,661		45,661
Beginning Balance, Weighted-Average Grant-Date Fair Value			$ 79.21
Granted Weighted-Average Grant-Date Fair Value			133.67
Stock Award Exercised/Vested, Weighted Average Grant Date Fair Value			74.89
Ending Balance, Weighted-Average Grant-Date Fair Value	$ 87.15		$ 87.15
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			3,460
Forfeited/expired, Number of Shares/Units			(3,167)
Ending Balance, Number of Shares/Units	449,630		449,630
Beginning Balance, Weighted-Average Grant-Date Fair Value			$ 93.05
Granted Weighted-Average Grant-Date Fair Value			132.72
Forfeited/Expired, Weighted-Average Price			94.57
Ending Balance, Weighted-Average Grant-Date Fair Value	$ 93.35		$ 93.35
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			(103,060)
Ending Balance, Number of Shares	774,621		774,621
Beginning Balance, Weighted-Average Exercise Price			$ 69.02
Stock options exercised, Weighted-Average Exercise Price			62.97
Ending Balance, Weighted-Average Exercise Price	$ 69.83		$ 69.83
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		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		$ 84.08

Stock-Based Compensation - Shar

Stock-Based Compensation - Shares Issued in Connection with Stock Compensation Awards (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Share-based Payment Arrangement [Abstract]
New shares issued from available authorized shares	0	0	0	0
Shares issued from available treasury stock	28,832	114,252	144,262	628,076
Proceeds from stock option exercises	$ 751	$ 7,285	$ 6,490	$ 36,682

Stock-Based Compensation - Stoc

Stock-Based Compensation - Stock-Based Compensation Expense (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Payment Arrangement, Expense	$ 3,418	$ 3,245	$ 5,530	$ 5,771
Income tax benefit	612	514	1,320	881
Non-Vested Stock Awards/Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted Stock or Unit Expense	2,291	1,768	4,649	3,651
Director deferred stock units outstanding [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted Stock or Unit Expense	720	700	720	700
Performance Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted Stock or Unit Expense	$ 407	$ 777	$ 161	$ 1,420

Stock-Based Compensation - Unre

Stock-Based Compensation - Unrecognized Stock-Based Compensation Expense (Detail) $ in Thousands	Jun. 30, 2022 USD ($)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Non-vested stock units	$ 13,954
Performance stock units	8,256
Total	$ 22,210

Earnings Per Common Share - Bas

Earnings Per Common Share - Basic and Diluted Earnings Per Common Share (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Earnings Per Share [Abstract]
Net income	$ 119,114	$ 118,068	$ 218,216	$ 234,083
Less: Preferred stock dividends	1,669	1,669	3,338	3,820
Net income available to common shareholders	117,445	116,399	214,878	230,263
Less: Earnings allocated to participating securities	1,036	1,141	1,888	2,307
Distributed earnings allocated to common stock	48,092	45,824	96,143	91,484
Undistributed earnings allocated to common stock	68,317	69,434	116,847	136,472
Net earnings allocated to common stock	$ 116,409	$ 115,258	$ 212,990	$ 227,956
Weighted-average shares outstanding for basic earnings per common share	64,112,828	63,606,340	64,082,185	63,457,245
Dilutive effect of stock compensation	354,401	495,819	382,395	511,288
Weighted-average shares outstanding for diluted earnings per common share	64,467,229	64,102,159	64,464,580	63,968,533

Defined Benefit Plans Additiona

Defined Benefit Plans Additional Information (Details) $ in Thousands	6 Months Ended
	Jun. 30, 2022 USD ($)
Retirement Benefits [Abstract]
Defined Benefit Plan, Plan Assets, Contributions by Employer	$ 0
Defined Benefit Plan, Expected Future Employer Contributions, Current Fiscal Year	$ 0

Defined Benefit Plans - Net Per

Defined Benefit Plans - Net Periodic Cost (Benefit) (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Retirement Benefits [Abstract]
Expected return on plan assets, net of expenses	$ (3,492)	$ (3,210)	$ (6,983)	$ (6,420)
Interest cost on projected benefit obligation	1,004	836	2,008	1,671
Net amortization and deferral	741	1,529	1,482	3,058
Net periodic expense (benefit)	$ (1,747)	$ (845)	$ (3,493)	$ (1,691)

Income Taxes - Additional Infor

Income Taxes - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021	Dec. 31, 2021
Income Tax Disclosure [Abstract]
Deferred Tax Assets, Net	$ 245.9		$ 245.9
Deferred Tax Liabilities, Net					$ 81.2
Valuation allowance	$ 0		$ 0
U.S. federal statutory income tax rate, percent	21%	21%	21%	21%
Unrecognized tax benefits	$ 0	$ 0	$ 0	$ 0

Income Taxes - Income Tax Expen

Income Taxes - Income Tax Expense (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Income Tax Disclosure [Abstract]
Current income tax expense (benefit)	$ 22,646	$ 14,065	$ 35,705	$ 17,790
Deferred income tax expense (benefit)	(1,972)	1,016	(2,404)	5,188
Income tax expense, as reported	$ 20,674	$ 15,081	$ 33,301	$ 22,978
Effective tax rate	14.80%	11.30%	13.20%	8.90%

Other Comprehensive Income (L_3

Other Comprehensive Income (Loss) - Component of Other Comprehensive Income (Loss) (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Equity [Abstract]
Securities available for sale and transferred securities, Change in net unrealized gain/loss during the period, Before Tax Amount	$ (636,523)	$ 30,668	$ (1,547,318)	$ (129,111)
Securities available for sale and transferred securities, Change in net unrealized gain on securities transferred to held to maturity, Before Tax Amount	(189)	(245)	(398)	(504)
Securities available for sale and transferred securities, Reclassification adjustment for net (gains) losses included in net income, Before Tax Amount	0	0	0	0
Total securities available for sale and transferred securities, before tax amount	(636,712)	30,423	(1,547,716)	(129,615)
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	1,482	3,058
Total defined-benefit post-retirement benefit plans	741	1,529	1,482	3,058
Total other comprehensive income (loss), before tax	(635,971)	31,952	(1,546,234)	(126,557)
Securities available for sale and transferred securities, Change in net unrealized gain/loss during the period, Tax Expense (Benefit)	(133,670)	6,441	(324,937)	(27,113)
Securities available for sale and transferred securities, Change in net unrealized gain on securities transferred to held to maturity, Tax Expense (Benefit)	(40)	(52)	(84)	(106)
Securities available for sale and transferred securities, Reclassification adjustment for net (gains) losses included in net income, Tax Expense (Benefit)	0	0	0	0
Total securities available for sale and transferred securities, Tax Expense (Benefit)	(133,710)	6,389	(325,021)	(27,219)
Reclassification adjustment for net amortization of actuarial gain/loss included in net income as a component of net periodic cost (benefit), Tax Expense (Benefit)	155	321	311	642
Total defined-benefit post-retirement benefit plans, Tax Expense (Benefit)	155	321	311	642
Total other comprehensive income (loss), Tax Expense (Benefit)	(133,555)	6,710	(324,710)	(26,577)
Securities available for sale and transferred securities, Change in net unrealized gain/loss during the period, Net of Tax	(502,853)	24,227	(1,222,381)	(101,998)
Securities available for sale and transferred securities, Change in net unrealized gain on securities transferred to held to maturity, Net of Tax	(149)	(193)	(314)	(398)
Securities available for sale and transferred securities, Reclassification adjustment for net (gains) losses included in net income, Net of Tax	0	0	0	0
Total securities available for sale and transferred securities, Net of Tax	(503,002)	24,034	(1,222,695)	(102,396)
Reclassification adjustment for net amortization of actuarial gain/lloss included in net income as a component of net periodic cost (benefit), Net of Tax	586	1,208	1,171	2,416
Total defined-benefit post-retirement benefit plans, Net of Tax Amount	586	1,208	1,171	2,416
Other comprehensive income (loss), net of tax	$ (502,416)	$ 25,242	$ (1,221,524)	$ (99,980)

Other Comprehensive Income - Sc

Other Comprehensive Income - Schedule of Accumulated Other Comprehensive Income, Net of Tax (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning Balance			$ 347,318
Other comprehensive income (loss), net of tax	$ (502,416)	$ 25,242	(1,221,524)	$ (99,980)
Ending Balance	(874,206)		(874,206)
Securities Available For Sale [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning Balance			380,209	563,801
Other comprehensive income (loss) before reclassifications			(1,222,695)	(102,396)
Reclassification of amounts included in net income			0	0
Other comprehensive income (loss), net of tax			(1,222,695)	(102,396)
Ending Balance	(842,486)	461,405	(842,486)	461,405
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			1,171	2,416
Other comprehensive income (loss), net of tax			1,171	2,416
Ending Balance	(31,720)	(48,415)	(31,720)	(48,415)
AOCI Attributable to Parent [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning Balance			347,318	512,970
Other comprehensive income (loss) before reclassifications			(1,222,695)	(102,396)
Reclassification of amounts included in net income			1,171	2,416
Other comprehensive income (loss), net of tax			(1,221,524)	(99,980)
Ending Balance	$ (874,206)	$ 412,990	$ (874,206)	$ 412,990

Operating Segments - Additional

Operating Segments - Additional Information (Detail)	6 Months Ended
	Jun. 30, 2022 Segment
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		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Segment Reporting Information [Line Items]
Interest Income (Expense), Net	$ 288,208	$ 257,156	$ 537,279	$ 498,037
Credit loss expense	0	0	0	63
Total non-interest income	97,927	91,247	199,317	184,483
Total non-interest expense	246,347	215,254	485,079	425,396
Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest	139,788	133,149	251,517	257,061
Income taxes	20,674	15,081	33,301	22,978
Net income	119,114	118,068	218,216	234,083
Less: Preferred stock dividends	1,669	1,669	3,338	3,820
Net Income (Loss) Available to Common Stockholders, Basic	117,445	116,399	214,878	230,263
Revenues from (expenses to) external customers	386,135	348,403	736,596	682,520
Bank
Segment Reporting Information [Line Items]
Interest Income (Expense), Net	289,186	258,450	539,305	500,655
Credit loss expense	1	0	0	63
Total non-interest income	55,397	48,944	114,103	102,724
Total non-interest expense	211,044	183,109	417,582	362,260
Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest	133,538	124,285	235,826	241,056
Income taxes	19,821	13,605	30,835	20,782
Net income	113,717	110,680	204,991	220,274
Less: Preferred stock dividends	0	0	0	0
Net Income (Loss) Available to Common Stockholders, Basic	113,717	110,680	204,991	220,274
Revenues from (expenses to) external customers	344,583	307,394	653,408	603,379
Frost Wealth Advisors [Member]
Segment Reporting Information [Line Items]
Interest Income (Expense), Net	958	508	1,658	994
Credit loss expense	(1)	0	0	0
Total non-interest income	43,054	42,534	86,283	82,143
Total non-interest expense	33,158	30,014	64,068	59,951
Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest	10,855	13,028	23,873	23,186
Income taxes	2,279	2,736	5,013	4,869
Net income	8,576	10,292	18,860	18,317
Less: Preferred stock dividends	0	0	0	0
Net Income (Loss) Available to Common Stockholders, Basic	8,576	10,292	18,860	18,317
Revenues from (expenses to) external customers	44,012	43,042	87,941	83,137
Non-Banks [Member]
Segment Reporting Information [Line Items]
Interest Income (Expense), Net	(1,936)	(1,802)	(3,684)	(3,612)
Credit loss expense	0	0	0	0
Total non-interest income	(524)	(231)	(1,069)	(384)
Total non-interest expense	2,145	2,131	3,429	3,185
Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest	(4,605)	(4,164)	(8,182)	(7,181)
Income taxes	(1,426)	(1,260)	(2,547)	(2,673)
Net income	(3,179)	(2,904)	(5,635)	(4,508)
Less: Preferred stock dividends	1,669	1,669	3,338	3,820
Net Income (Loss) Available to Common Stockholders, Basic	(4,848)	(4,573)	(8,973)	(8,328)
Revenues from (expenses to) external customers	$ (2,460)	$ (2,033)	$ (4,753)	$ (3,996)

Fair Value Measurements - Addit

Fair Value Measurements - Additional Information (Detail) - USD ($) $ in Thousands	Jun. 30, 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	Jun. 30, 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	$ 16,781,685	$ 13,924,628
Trading account securities	24,680	25,162
Derivative assets	61,994	23,339
Derivative liabilities	222,814	114,019
Interest rate swaps, caps and floors [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	41,485	44,310
Derivative liabilities	58,240	25,261
Commodity swaps and options [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	245,218	114,757
Derivative liabilities	243,638	113,261
Foreign Exchange Forward [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	199	33
Derivative liabilities	195	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	4,416,299	2,179,433
Trading account securities	24,615	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	5,335,725	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	6,987,296	7,636,571
Trading account securities	65	925
Other [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale, at estimated fair value	42,365	42,359
Level 1 [Member] | Foreign Exchange Forward [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	199	33
Derivative liabilities	195	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	4,416,299	2,179,433
Trading account securities	24,615	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	41,485	44,310
Derivative liabilities	58,240	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	245,218	114,757
Derivative liabilities	243,638	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	5,335,725	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	6,987,296	7,636,571
Trading account securities	65	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	$ 42,365	$ 42,359

Fair Value Measurements - Impai

Fair Value Measurements - Impaired Loans Remeasured and Reported at Fair Value of Underlying Collateral (Detail) - USD ($) $ in Thousands	Jun. 30, 2022	Jun. 30, 2021
Level 2 [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Carrying value of impaired loans before allocations	$ 5,454	$ 3,399
Impaired Financing Receivable, Related Allowance	(1,327)	(336)
Loans receivable, fair value disclosure	4,127	3,063
Level 3 [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Carrying value of impaired loans before allocations	3,614	19,423
Impaired Financing Receivable, Related Allowance		(3,273)
Impaired Financing Receivable, Reversal of Specific Valuation Allowance Allocations	6,877
Loans receivable, fair value disclosure	$ 10,491	$ 16,150

Fair Value Measurements - Estim

Fair Value Measurements - Estimated Fair Values of Financial Instruments (Detail) - USD ($) $ in Thousands	Jun. 30, 2022	Dec. 31, 2021	Jun. 30, 2021	Dec. 31, 2020
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	$ 13,658,585	$ 16,583,000	$ 15,184,395	$ 10,288,853
Securities held to maturity	1,946,428	1,749,179
Loans, net	16,496,394	16,087,731
Deposits	45,601,765	42,695,696
Federal funds purchased	43,200	25,925
Repurchase agreements	1,664,685	2,740,799
Junior subordinated deferrable interest debentures	123,040	123,011
Subordinated notes	99,256	99,178
Carrying Amount [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	13,658,585	16,583,000
Securities held to maturity	1,946,428	1,749,179
Cash surrender value of life insurance policies	189,823	190,139
Accrued interest receivable	194,049	179,111
Deposits	45,601,765	42,695,696
Federal funds purchased	43,200	25,925
Repurchase agreements	1,664,685	2,740,799
Junior subordinated deferrable interest debentures	123,040	123,011
Subordinated notes	99,256	99,178
Accrued interest payable	6,059	3,026
Carrying Amount [Member] | Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans, net	16,496,394	16,087,731
Estimated Fair Value [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	13,658,585	16,583,000
Securities held to maturity	1,828,515	1,809,143
Cash surrender value of life insurance policies	189,823	190,139
Accrued interest receivable	194,049	179,111
Deposits	45,584,113	41,343,426
Federal funds purchased	43,200	25,925
Repurchase agreements	1,664,685	2,740,799
Junior subordinated deferrable interest debentures	123,712	123,712
Subordinated notes	99,626	111,430
Accrued interest payable	6,059	3,026
Estimated Fair Value [Member] | Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans, net	$ 16,126,497	$ 16,079,454