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		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022	Dec. 31, 2022
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	$ 31,021		$ 31,021		$ 34,319
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	43,385		43,385		45,247
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment	34,035	$ 29,690	33,846	$ 30,233
Impaired Financing Receivable, with No Related Allowance, Interest Income, Cash Basis Method	(33)	(138)	(12)	(262)
Impaired Financing Receivable, with Related Allowance, Recorded Investment	16,988		16,988		1,168
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance	17,852		17,852		1,186
Related allowance	12,570		12,570		711
Impaired Financing Receivable, with Related Allowance, Average Recorded Investment	12,882	6,510	9,186	7,024
Impaired Financing Receivable, with Related Allowance, Interest Income, Cash Basis Method	0	0	0	0
Recorded investment	48,009		48,009		35,487
Unpaid principal balance	61,237		61,237		46,433
Impaired Financing Receivable, Average Recorded Investment	46,917	36,200	43,032	37,257
Impaired Financing Receivable, Interest Income, Cash Basis Method	(33)	(138)	(12)	(262)
Commercial, financial, agricultural and other [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	1,878		1,878		3,141
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	10,270		10,270		9,555
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment	4,416	3,822	4,444	3,883
Impaired Financing Receivable, with No Related Allowance, Interest Income, Cash Basis Method	(10)	(27)	(10)	(50)
Impaired Financing Receivable, with Related Allowance, Recorded Investment	15,152		15,152		1,168
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance	15,826		15,826		1,186
Related allowance	12,404		12,404		711
Impaired Financing Receivable, with Related Allowance, Average Recorded Investment	11,445	0	8,056	0
Impaired Financing Receivable, with Related Allowance, Interest Income, Cash Basis Method	0	0	0	0
Construction
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	0		0		0
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	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
Residential real estate [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	6,266		6,266		9,145
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	8,071		8,071		11,010
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment	6,312	8,769	6,190	8,985
Impaired Financing Receivable, with No Related Allowance, Interest Income, Cash Basis Method	(19)	(57)	(40)	(141)
Impaired Financing Receivable, with Related Allowance, Recorded Investment	1,236		1,236		0
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance	1,406		1,406		0
Related allowance	103		103		0
Impaired Financing Receivable, with Related Allowance, Average Recorded Investment	1,237	0	1,030	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	22,409		22,409		21,505
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	24,509		24,509		24,119
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment	22,853	16,676	22,769	16,933
Impaired Financing Receivable, with No Related Allowance, Interest Income, Cash Basis Method	(43)	(49)	(43)	(63)
Impaired Financing Receivable, with Related Allowance, Recorded Investment	600		600		0
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance	620		620		0
Related allowance	63		63		0
Impaired Financing Receivable, with Related Allowance, Average Recorded Investment	200	6,510	100	7,024
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	468		468		528
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	535		535		563
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment	454	423	443	432
Impaired Financing Receivable, with No Related Allowance, Interest Income, Cash Basis Method	(1)	(5)	(1)	(8)
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	0	0	0
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	1,755		1,755		3,141
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	10,147		10,147		9,555
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment	4,332	3,822	4,283	3,883
Impaired Financing Receivable, with No Related Allowance, Interest Income, Cash Basis Method	(10)	(27)	(10)	(50)
Impaired Financing Receivable, with Related Allowance, Recorded Investment	15,152		15,152		1,168
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance	15,826		15,826		1,186
Related allowance	12,404		12,404		711
Impaired Financing Receivable, with Related Allowance, Average Recorded Investment	11,445	0	8,056	0
Impaired Financing Receivable, with Related Allowance, Interest Income, Cash Basis Method	0	0	0	0
Senior Lien | Residential real estate [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	3,548		3,548		5,754
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	4,618		4,618		6,848
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment	3,584	4,963	3,510	5,080
Impaired Financing Receivable, with No Related Allowance, Interest Income, Cash Basis Method	(19)	(43)	(40)	(105)
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	2,718		2,718		3,391
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	3,453		3,453		4,162
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment	2,728	3,806	2,680	3,905
Impaired Financing Receivable, with No Related Allowance, Interest Income, Cash Basis Method	0	(14)	0	(36)
Impaired Financing Receivable, with Related Allowance, Recorded Investment	1,236		1,236		0
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance	1,406		1,406		0
Related allowance	103		103		0
Impaired Financing Receivable, with Related Allowance, Average Recorded Investment	1,237	0	1,030	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	68		68		0
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	68		68		0
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment	23	273	11	344
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
Nonowner Occupied Commercial Real Estate | Commercial Real Estate [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	20,649		20,649		20,155
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	22,931		22,931		22,565
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment	20,527	14,796	20,565	14,986
Impaired Financing Receivable, with No Related Allowance, Interest Income, Cash Basis Method	(4)	(42)	(4)	(52)
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	6,510	0	7,024
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	1,692		1,692		1,350
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	1,510		1,510		1,554
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment	2,303	1,607	2,193	1,603
Impaired Financing Receivable, with No Related Allowance, Interest Income, Cash Basis Method	(47)	(7)	(47)	(11)
Impaired Financing Receivable, with Related Allowance, Recorded Investment	600		600		0
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance	620		620		0
Related allowance	63		63		0
Impaired Financing Receivable, with Related Allowance, Average Recorded Investment	200	0	100	0
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	350		350		440
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	418		418		475
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment	353	365	355	361
Impaired Financing Receivable, with No Related Allowance, Interest Income, Cash Basis Method	(1)	(5)	(1)	(8)
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	118		118		88
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	117		117		88
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment	101	58	88	71
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		0
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	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
Construction Residential | Real estate construction [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment	0	0	0	0
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
Construction Other | Construction
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	0		0		0
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	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
Construction Other | Real estate construction [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment	0	0	0	0
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 Other | Commercial, financial, agricultural and other [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	0		0		0
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	0		0		0
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment	0	0	0	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		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
Equipment Finance | Commercial, financial, agricultural and other [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	123		123		0
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	123		123		0
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment	84	0	161	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		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