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
	Mar. 31, 2022	Mar. 31, 2021	Dec. 31, 2021
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	$ 36,514		$ 54,167
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	45,691		63,660
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment	37,509	$ 39,444
Impaired Financing Receivable, with No Related Allowance, Interest Income, Cash Basis Method	130	98
Impaired Financing Receivable, with Related Allowance, Recorded Investment	953		1,013
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance	1,013		1,060
Related allowance	351		395
Impaired Financing Receivable, with Related Allowance, Average Recorded Investment	800	12,357
Impaired Financing Receivable, with Related Allowance, Interest Income, Cash Basis Method	6	18
Recorded investment	37,467		55,180
Unpaid principal balance	46,704		64,720
Impaired Financing Receivable, Average Recorded Investment	38,309	51,801
Impaired Financing Receivable, Interest Income, Cash Basis Method	136	116
Commercial, financial, agricultural and other [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	3,505		3,720
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	9,719		10,303
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment	3,561	2,280
Impaired Financing Receivable, with No Related Allowance, Interest Income, Cash Basis Method	29	11
Impaired Financing Receivable, with Related Allowance, Recorded Investment	544		327
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance	572		349
Related allowance	272		307
Impaired Financing Receivable, with Related Allowance, Average Recorded Investment	384	4,895
Impaired Financing Receivable, with Related Allowance, Interest Income, Cash Basis Method	6	18
Construction
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	0		45
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	0		53
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
Residential real estate [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	9,161		9,365
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	11,035		11,294
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment	9,201	10,892
Impaired Financing Receivable, with No Related Allowance, Interest Income, Cash Basis Method	84	63
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
Commercial Real Estate [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	23,425		40,591
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	24,395		41,525
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment	24,312	25,739
Impaired Financing Receivable, with No Related Allowance, Interest Income, Cash Basis Method	13	22
Impaired Financing Receivable, with Related Allowance, Recorded Investment	409		686
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance	441		711
Related allowance	79		88
Impaired Financing Receivable, with Related Allowance, Average Recorded Investment	416	7,462
Impaired Financing Receivable, with Related Allowance, Interest Income, Cash Basis Method	0	0
Loans to individuals [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	423		446
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	542		485
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment	435	479
Impaired Financing Receivable, with No Related Allowance, Interest Income, Cash Basis Method	4	2
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
Real estate construction [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment	0	54
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 | Commercial, financial, agricultural and other [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	3,505		3,720
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	9,719		10,303
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment	3,561	2,280
Impaired Financing Receivable, with No Related Allowance, Interest Income, Cash Basis Method	29	11
Impaired Financing Receivable, with Related Allowance, Recorded Investment	544		327
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance	572		349
Related allowance	272		307
Impaired Financing Receivable, with Related Allowance, Average Recorded Investment	384	4,895
Impaired Financing Receivable, with Related Allowance, Interest Income, Cash Basis Method	6	18
Senior Lien | Residential real estate [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	5,245		5,200
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	6,327		6,337
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment	5,197	5,982
Impaired Financing Receivable, with No Related Allowance, Interest Income, Cash Basis Method	62	45
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
Junior Lien | Residential real estate [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	3,916		4,165
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	4,708		4,957
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment	4,004	4,910
Impaired Financing Receivable, with No Related Allowance, Interest Income, Cash Basis Method	22	18
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
Multifamily | Commercial Real Estate [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	0		14,677
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	0		14,677
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	409		421
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance	441		446
Related allowance	79		88
Impaired Financing Receivable, with Related Allowance, Average Recorded Investment	416	464
Impaired Financing Receivable, with Related Allowance, Interest Income, Cash Basis Method	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	21,791		24,581
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	22,558		25,310
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment	22,714	22,593
Impaired Financing Receivable, with No Related Allowance, Interest Income, Cash Basis Method	9	7
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	6,917
Impaired Financing Receivable, with Related Allowance, Interest Income, Cash Basis Method	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	1,634		1,333
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	1,837		1,538
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment	1,598	3,146
Impaired Financing Receivable, with No Related Allowance, Interest Income, Cash Basis Method	4	15
Impaired Financing Receivable, with Related Allowance, Recorded Investment	0		265
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance	0		265
Related allowance	0		0
Impaired Financing Receivable, with Related Allowance, Average Recorded Investment	0	81
Impaired Financing Receivable, with Related Allowance, Interest Income, Cash Basis Method	0	0
Automobiles | Loans to individuals [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	327		388
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	441		422
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment	350	437
Impaired Financing Receivable, with No Related Allowance, Interest Income, Cash Basis Method	4	2
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
Other Consumer Loans | Loans to individuals [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	96		58
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	101		63
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment	85	42
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
Construction Residential | Construction
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	0
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	0
Impaired Financing Receivable, with Related Allowance, Recorded Investment	0
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance	0
Related allowance	0
Construction Residential | Real estate construction [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment	0
Impaired Financing Receivable, with No Related Allowance, Interest Income, Cash Basis Method	0
Impaired Financing Receivable, with Related Allowance, Average Recorded Investment	0
Impaired Financing Receivable, with Related Allowance, Interest Income, Cash Basis Method	0
Construction Other | Construction
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	0
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	0
Impaired Financing Receivable, with Related Allowance, Recorded Investment	0
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance	0
Related allowance	0
Construction Other | Real estate construction [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment	0
Impaired Financing Receivable, with No Related Allowance, Interest Income, Cash Basis Method	0
Impaired Financing Receivable, with Related Allowance, Average Recorded Investment	0
Impaired Financing Receivable, with Related Allowance, Interest Income, Cash Basis Method	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
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	0
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment	0
Impaired Financing Receivable, with No Related Allowance, Interest Income, Cash Basis Method	0
Impaired Financing Receivable, with Related Allowance, Recorded Investment	0
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance	0
Related allowance	0
Impaired Financing Receivable, with Related Allowance, Average Recorded Investment	0
Impaired Financing Receivable, with Related Allowance, Interest Income, Cash Basis Method	0
Equipment Finance | Commercial, financial, agricultural and other [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	0
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	0
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment	0
Impaired Financing Receivable, with No Related Allowance, Interest Income, Cash Basis Method	0
Impaired Financing Receivable, with Related Allowance, Recorded Investment	0
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance	0
Related allowance	0
Impaired Financing Receivable, with Related Allowance, Average Recorded Investment	0
Impaired Financing Receivable, with Related Allowance, Interest Income, Cash Basis Method	$ 0