Loans and Allowance for Credit Losses - Recorded Investment and Unpaid Principal Balance for Impaired Loans with Associated Allowance (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021	Dec. 31, 2021
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	$ 28,034		$ 28,034		$ 54,167
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	37,309		37,309		63,660
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment	29,066	$ 36,443	29,844	$ 41,123
Impaired Financing Receivable, with No Related Allowance, Interest Income, Cash Basis Method	110	131	380	438
Impaired Financing Receivable, with Related Allowance, Recorded Investment	7,658		7,658		1,013
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance	8,755		8,755		1,060
Related allowance	1,534		1,534		395
Impaired Financing Receivable, with Related Allowance, Average Recorded Investment	6,920	9,318	6,990	9,228
Impaired Financing Receivable, with Related Allowance, Interest Income, Cash Basis Method	0	19	0	50
Recorded investment	35,692		35,692		55,180
Unpaid principal balance	46,064		46,064		64,720
Impaired Financing Receivable, Average Recorded Investment	35,986	45,761	36,834	50,351
Impaired Financing Receivable, Interest Income, Cash Basis Method	110	150	380	488
Commercial, financial, agricultural and other [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	3,381		3,381		3,720
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	9,749		9,749		10,303
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment	3,518	9,858	3,762	9,266
Impaired Financing Receivable, with No Related Allowance, Interest Income, Cash Basis Method	30	3	88	50
Impaired Financing Receivable, with Related Allowance, Recorded Investment	1,380		1,380		327
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance	1,555		1,555		349
Related allowance	1,380		1,380		307
Impaired Financing Receivable, with Related Allowance, Average Recorded Investment	584	1,842	195	1,820
Impaired Financing Receivable, with Related Allowance, Interest Income, Cash Basis Method	0	19	0	50
Construction
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	0		0		45
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	0		0		53
Impaired Financing Receivable, with Related Allowance, Recorded Investment	0		0		0
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance	0		0		0
Related allowance	0		0		0
Residential real estate [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	8,711		8,711		9,365
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	10,573		10,573		11,294
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment	8,981	10,060	8,984	10,504
Impaired Financing Receivable, with No Related Allowance, Interest Income, Cash Basis Method	48	54	190	275
Impaired Financing Receivable, with Related Allowance, Recorded Investment	0		0		0
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance	0		0		0
Related allowance	0		0		0
Impaired Financing Receivable, with Related Allowance, Average Recorded Investment	0	0	0	0
Impaired Financing Receivable, with Related Allowance, Interest Income, Cash Basis Method	0	0	0	0
Commercial Real Estate [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	15,467		15,467		40,591
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	16,434		16,434		41,525
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment	16,124	15,967	16,663	20,813
Impaired Financing Receivable, with No Related Allowance, Interest Income, Cash Basis Method	27	68	89	101
Impaired Financing Receivable, with Related Allowance, Recorded Investment	6,278		6,278		686
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance	7,200		7,200		711
Related allowance	154		154		88
Impaired Financing Receivable, with Related Allowance, Average Recorded Investment	6,336	7,476	6,795	7,408
Impaired Financing Receivable, with Related Allowance, Interest Income, Cash Basis Method	0	0	0	0
Loans to individuals [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	475		475		446
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	553		553		485
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment	443	504	435	486
Impaired Financing Receivable, with No Related Allowance, Interest Income, Cash Basis Method	5	6	13	12
Impaired Financing Receivable, with Related Allowance, Recorded Investment	0		0		0
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance	0		0		0
Related allowance	0		0		0
Impaired Financing Receivable, with Related Allowance, Average Recorded Investment	0	0	0	0
Impaired Financing Receivable, with Related Allowance, Interest Income, Cash Basis Method	0	0	0	0
Real estate construction [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment	0	54	0	54
Impaired Financing Receivable, with No Related Allowance, Interest Income, Cash Basis Method	0	0	0	0
Impaired Financing Receivable, with Related Allowance, Average Recorded Investment	0	0	0	0
Impaired Financing Receivable, with Related Allowance, Interest Income, Cash Basis Method	0	0	0	0
Time and Demand Loans | Commercial, financial, agricultural and other [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	3,381		3,381		3,720
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	9,749		9,749		10,303
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment	3,518	9,858	3,762	9,266
Impaired Financing Receivable, with No Related Allowance, Interest Income, Cash Basis Method	30	3	88	50
Impaired Financing Receivable, with Related Allowance, Recorded Investment	1,380		1,380		327
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance	1,555		1,555		349
Related allowance	1,380		1,380		307
Impaired Financing Receivable, with Related Allowance, Average Recorded Investment	584	1,842	195	1,820
Impaired Financing Receivable, with Related Allowance, Interest Income, Cash Basis Method	0	19	0	50
Senior Lien | Residential real estate [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	5,180		5,180		5,200
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	6,262		6,262		6,337
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment	5,200	5,558	5,120	5,734
Impaired Financing Receivable, with No Related Allowance, Interest Income, Cash Basis Method	33	34	139	210
Impaired Financing Receivable, with Related Allowance, Recorded Investment	0		0		0
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance	0		0		0
Related allowance	0		0		0
Impaired Financing Receivable, with Related Allowance, Average Recorded Investment	0	0	0	0
Impaired Financing Receivable, with Related Allowance, Interest Income, Cash Basis Method	0	0	0	0
Junior Lien | Residential real estate [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	3,531		3,531		4,165
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	4,311		4,311		4,957
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment	3,781	4,502	3,864	4,770
Impaired Financing Receivable, with No Related Allowance, Interest Income, Cash Basis Method	15	20	51	65
Impaired Financing Receivable, with Related Allowance, Recorded Investment	0		0		0
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance	0		0		0
Related allowance	0		0		0
Impaired Financing Receivable, with Related Allowance, Average Recorded Investment	0	0	0	0
Impaired Financing Receivable, with Related Allowance, Interest Income, Cash Basis Method	0	0	0	0
Multifamily | Commercial Real Estate [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	0		0		14,677
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	0		0		14,677
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment	0	0	230	0
Impaired Financing Receivable, with No Related Allowance, Interest Income, Cash Basis Method	0	0	0	0
Impaired Financing Receivable, with Related Allowance, Recorded Investment	0		0		421
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance	0		0		446
Related allowance	0		0		88
Impaired Financing Receivable, with Related Allowance, Average Recorded Investment	0	439	0	451
Impaired Financing Receivable, with Related Allowance, Interest Income, Cash Basis Method	0	0	0	0
Nonowner Occupied Commercial Real Estate | Commercial Real Estate [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	14,121		14,121		24,581
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	14,896		14,896		25,310
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment	14,637	13,633	14,869	18,050
Impaired Financing Receivable, with No Related Allowance, Interest Income, Cash Basis Method	18	4	69	15
Impaired Financing Receivable, with Related Allowance, Recorded Investment	6,278		6,278		0
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance	7,200		7,200		0
Related allowance	154		154		0
Impaired Financing Receivable, with Related Allowance, Average Recorded Investment	6,336	6,917	6,795	6,917
Impaired Financing Receivable, with Related Allowance, Interest Income, Cash Basis Method	0	0	0	0
Owner Occupied Commercial Real Estate | Commercial Real Estate [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	1,346		1,346		1,333
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	1,538		1,538		1,538
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment	1,487	2,334	1,564	2,763
Impaired Financing Receivable, with No Related Allowance, Interest Income, Cash Basis Method	9	64	20	86
Impaired Financing Receivable, with Related Allowance, Recorded Investment	0		0		265
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance	0		0		265
Related allowance	0		0		0
Impaired Financing Receivable, with Related Allowance, Average Recorded Investment	0	120	0	40
Impaired Financing Receivable, with Related Allowance, Interest Income, Cash Basis Method	0	0	0	0
Automobiles | Loans to individuals [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	408		408		388
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	481		481		422
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment	369	448	363	433
Impaired Financing Receivable, with No Related Allowance, Interest Income, Cash Basis Method	5	6	13	12
Impaired Financing Receivable, with Related Allowance, Recorded Investment	0		0		0
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance	0		0		0
Related allowance	0		0		0
Impaired Financing Receivable, with Related Allowance, Average Recorded Investment	0	0	0	0
Impaired Financing Receivable, with Related Allowance, Interest Income, Cash Basis Method	0	0	0	0
Other Consumer Loans | Loans to individuals [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	67		67		58
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	72		72		63
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment	74	56	72	53
Impaired Financing Receivable, with No Related Allowance, Interest Income, Cash Basis Method	0	0	0	0
Impaired Financing Receivable, with Related Allowance, Recorded Investment	0		0		0
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance	0		0		0
Related allowance	0		0		$ 0
Impaired Financing Receivable, with Related Allowance, Average Recorded Investment	0	0	0	0
Impaired Financing Receivable, with Related Allowance, Interest Income, Cash Basis Method	0	$ 0	0	$ 0
Construction Residential | Construction
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	0		0
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	0		0
Impaired Financing Receivable, with Related Allowance, Recorded Investment	0		0
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance	0		0
Related allowance	0		0
Construction Residential | Real estate construction [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment	0		0
Impaired Financing Receivable, with No Related Allowance, Interest Income, Cash Basis Method	0		0
Impaired Financing Receivable, with Related Allowance, Average Recorded Investment	0		0
Impaired Financing Receivable, with Related Allowance, Interest Income, Cash Basis Method	0		0
Construction Other | Construction
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	0		0
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	0		0
Impaired Financing Receivable, with Related Allowance, Recorded Investment	0		0
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance	0		0
Related allowance	0		0
Construction Other | Real estate construction [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment	0		0
Impaired Financing Receivable, with No Related Allowance, Interest Income, Cash Basis Method	0		0
Impaired Financing Receivable, with Related Allowance, Average Recorded Investment	0		0
Impaired Financing Receivable, with Related Allowance, Interest Income, Cash Basis Method	0		0
Time and Demand Loans Other | Commercial, financial, agricultural and other [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	0		0
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	0		0
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment	0		0
Impaired Financing Receivable, with No Related Allowance, Interest Income, Cash Basis Method	0		0
Impaired Financing Receivable, with Related Allowance, Recorded Investment	0		0
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance	0		0
Related allowance	0		0
Impaired Financing Receivable, with Related Allowance, Average Recorded Investment	0		0
Impaired Financing Receivable, with Related Allowance, Interest Income, Cash Basis Method	0		0
Equipment Finance | Commercial, financial, agricultural and other [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	0		0
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	0		0
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment	0		0
Impaired Financing Receivable, with No Related Allowance, Interest Income, Cash Basis Method	0		0
Impaired Financing Receivable, with Related Allowance, Recorded Investment	0		0
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance	0		0
Related allowance	0		0
Impaired Financing Receivable, with Related Allowance, Average Recorded Investment	0		0
Impaired Financing Receivable, with Related Allowance, Interest Income, Cash Basis Method	$ 0		$ 0