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, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022	Dec. 31, 2022
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	$ 17,789		$ 17,789		$ 34,319
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	28,958		28,958		45,247
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment	18,204	$ 29,066	20,244	$ 29,844
Impaired Financing Receivable, with No Related Allowance, Interest Income, Cash Basis Method	(389)	(110)	(393)	(380)
Impaired Financing Receivable, with Related Allowance, Recorded Investment	30,135		30,135		1,168
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance	32,427		32,427		1,186
Related allowance	16,226		16,226		711
Impaired Financing Receivable, with Related Allowance, Average Recorded Investment	29,730	6,920	24,423	6,990
Impaired Financing Receivable, with Related Allowance, Interest Income, Cash Basis Method	0	0	16	0
Recorded investment	47,924		47,924		35,487
Unpaid principal balance	61,385		61,385		46,433
Impaired Financing Receivable, Average Recorded Investment	47,934	35,986	44,667	36,834
Impaired Financing Receivable, Interest Income, Cash Basis Method	(389)	(110)	(377)	(380)
Commercial, financial, agricultural and other [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	2,671		2,671		3,141
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	11,142		11,142		9,555
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment	2,509	3,518	3,974	3,762
Impaired Financing Receivable, with No Related Allowance, Interest Income, Cash Basis Method	(135)	(30)	(141)	(88)
Impaired Financing Receivable, with Related Allowance, Recorded Investment	15,229		15,229		1,168
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance	16,562		16,562		1,186
Related allowance	11,994		11,994		711
Impaired Financing Receivable, with Related Allowance, Average Recorded Investment	14,980	584	10,190	195
Impaired Financing Receivable, with Related Allowance, Interest Income, Cash Basis Method	0	0	16	0
Construction
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	3,288		3,288		0
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	3,288		3,288		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	6,514		6,514		9,145
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	8,328		8,328		11,010
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment	6,290	8,981	6,224	8,984
Impaired Financing Receivable, with No Related Allowance, Interest Income, Cash Basis Method	(35)	(48)	(75)	(190)
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	70		70		0
Impaired Financing Receivable, with Related Allowance, Average Recorded Investment	1,236	0	1,099	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	5,114		5,114		21,505
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	5,847		5,847		24,119
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment	7,908	16,124	9,253	16,663
Impaired Financing Receivable, with No Related Allowance, Interest Income, Cash Basis Method	(213)	(27)	(170)	(89)
Impaired Financing Receivable, with Related Allowance, Recorded Investment	13,670		13,670		0
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance	14,459		14,459		0
Related allowance	4,162		4,162		0
Impaired Financing Receivable, with Related Allowance, Average Recorded Investment	13,514	6,336	13,134	6,795
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	202		202		528
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	353		353		563
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment	401	443	428	435
Impaired Financing Receivable, with No Related Allowance, Interest Income, Cash Basis Method	(6)	(5)	(7)	(13)
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	1,096	0	365	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	2,290		2,290		3,141
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	10,761		10,761		9,555
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment	2,269	3,518	3,786	3,762
Impaired Financing Receivable, with No Related Allowance, Interest Income, Cash Basis Method	(135)	(30)	(141)	(88)
Impaired Financing Receivable, with Related Allowance, Recorded Investment	15,229		15,229		1,168
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance	16,562		16,562		1,186
Related allowance	11,994		11,994		711
Impaired Financing Receivable, with Related Allowance, Average Recorded Investment	14,980	584	10,190	195
Impaired Financing Receivable, with Related Allowance, Interest Income, Cash Basis Method	0	0	16	0
Senior Lien | Residential real estate [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	3,883		3,883		5,754
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	4,970		4,970		6,848
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment	3,784	5,200	3,602	5,120
Impaired Financing Receivable, with No Related Allowance, Interest Income, Cash Basis Method	(34)	(33)	(74)	(139)
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	2,631		2,631		3,391
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	3,358		3,358		4,162
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment	2,506	3,781	2,622	3,864
Impaired Financing Receivable, with No Related Allowance, Interest Income, Cash Basis Method	(1)	(15)	(1)	(51)
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	70		70		0
Impaired Financing Receivable, with Related Allowance, Average Recorded Investment	1,236	0	1,099	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	68	0	30	230
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	3,575		3,575		20,155
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	4,553		4,553		22,565
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment	6,498	14,637	7,313	14,869
Impaired Financing Receivable, with No Related Allowance, Interest Income, Cash Basis Method	(53)	(18)	(57)	(69)
Impaired Financing Receivable, with Related Allowance, Recorded Investment	12,601		12,601		0
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance	13,369		13,369		0
Related allowance	4,099		4,099		0
Impaired Financing Receivable, with Related Allowance, Average Recorded Investment	12,601	6,336	12,763	6,795
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	1,471		1,471		1,350
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	1,226		1,226		1,554
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment	1,342	1,487	1,910	1,564
Impaired Financing Receivable, with No Related Allowance, Interest Income, Cash Basis Method	(160)	(9)	(113)	(20)
Impaired Financing Receivable, with Related Allowance, Recorded Investment	1,069		1,069		0
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance	1,090		1,090		0
Related allowance	63		63		0
Impaired Financing Receivable, with Related Allowance, Average Recorded Investment	913	0	371	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	200		200		440
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	351		351		475
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment	315	369	341	363
Impaired Financing Receivable, with No Related Allowance, Interest Income, Cash Basis Method	(6)	(5)	(7)	(13)
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	2		2		88
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	2		2		88
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment	86	74	87	72
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	3,288		3,288		0
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	3,288		3,288		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	1,096	0	365	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	381		381		0
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	381		381		0
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment	240	0	188	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