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, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021	Dec. 31, 2021
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	$ 29,239		$ 29,239		$ 54,167
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	37,765		37,765		63,660
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment	29,690	$ 30,369	30,233	$ 31,102
Impaired Financing Receivable, with No Related Allowance, Interest Income, Cash Basis Method	138	201	262	300
Impaired Financing Receivable, with Related Allowance, Recorded Investment	6,453		6,453		1,013
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance	7,263		7,263		1,060
Related allowance	360		360		395
Impaired Financing Receivable, with Related Allowance, Average Recorded Investment	6,510	23,120	7,024	21,543
Impaired Financing Receivable, with Related Allowance, Interest Income, Cash Basis Method	0	19	0	36
Recorded investment	35,692		35,692		55,180
Unpaid principal balance	45,028		45,028		64,720
Impaired Financing Receivable, Average Recorded Investment	36,200	53,489	37,257	52,645
Impaired Financing Receivable, Interest Income, Cash Basis Method	138	220	262	336
Commercial, financial, agricultural and other [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	3,653		3,653		3,720
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	10,002		10,002		10,303
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment	3,822	5,591	3,883	3,966
Impaired Financing Receivable, with No Related Allowance, Interest Income, Cash Basis Method	27	31	50	43
Impaired Financing Receivable, with Related Allowance, Recorded Investment	0		0		327
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance	0		0		349
Related allowance	0		0		307
Impaired Financing Receivable, with Related Allowance, Average Recorded Investment	0	8,791	0	6,813
Impaired Financing Receivable, with Related Allowance, Interest Income, Cash Basis Method	0	19	0	36
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	8,638		8,638		9,365
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	10,527		10,527		11,294
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment	8,769	10,560	8,985	10,726
Impaired Financing Receivable, with No Related Allowance, Interest Income, Cash Basis Method	57	159	141	221
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	16,510		16,510		40,591
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	16,752		16,752		41,525
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment	16,676	13,689	16,933	15,879
Impaired Financing Receivable, with No Related Allowance, Interest Income, Cash Basis Method	49	7	63	30
Impaired Financing Receivable, with Related Allowance, Recorded Investment	6,453		6,453		686
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance	7,263		7,263		711
Related allowance	360		360		88
Impaired Financing Receivable, with Related Allowance, Average Recorded Investment	6,510	14,329	7,024	14,730
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	438		438		446
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	484		484		485
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment	423	475	432	477
Impaired Financing Receivable, with No Related Allowance, Interest Income, Cash Basis Method	5	4	8	6
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	3,653		3,653		3,720
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	10,002		10,002		10,303
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment	3,822	5,591	3,883	3,966
Impaired Financing Receivable, with No Related Allowance, Interest Income, Cash Basis Method	27	31	50	43
Impaired Financing Receivable, with Related Allowance, Recorded Investment	0		0		327
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance	0		0		349
Related allowance	0		0		307
Impaired Financing Receivable, with Related Allowance, Average Recorded Investment	0	8,791	0	6,813
Impaired Financing Receivable, with Related Allowance, Interest Income, Cash Basis Method	0	19	0	36
Senior Lien | Residential real estate [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	4,859		4,859		5,200
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	5,950		5,950		6,337
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment	4,963	5,661	5,080	5,822
Impaired Financing Receivable, with No Related Allowance, Interest Income, Cash Basis Method	43	132	105	176
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	3,779		3,779		4,165
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	4,577		4,577		4,957
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment	3,806	4,899	3,905	4,904
Impaired Financing Receivable, with No Related Allowance, Interest Income, Cash Basis Method	14	27	36	45
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	273	0	344	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	450	0	457
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	14,913		14,913		24,581
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	14,939		14,939		25,310
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment	14,796	11,227	14,986	13,079
Impaired Financing Receivable, with No Related Allowance, Interest Income, Cash Basis Method	42	2	52	10
Impaired Financing Receivable, with Related Allowance, Recorded Investment	6,453		6,453		0
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance	7,263		7,263		0
Related allowance	360		360		0
Impaired Financing Receivable, with Related Allowance, Average Recorded Investment	6,510	13,614	7,024	14,096
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	1,597		1,597		1,333
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	1,813		1,813		1,538
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment	1,607	2,462	1,603	2,800
Impaired Financing Receivable, with No Related Allowance, Interest Income, Cash Basis Method	7	5	11	20
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	265	0	177
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	364		364		388
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	405		405		422
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment	365	415	361	426
Impaired Financing Receivable, with No Related Allowance, Interest Income, Cash Basis Method	5	4	8	6
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	74		74		58
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	79		79		63
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment	58	60	71	51
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