Allowance for Credit Losses - Summary of Activity in Allowance for Loan Losses (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	$ 85,941	$ 57,911	$ 91,847	$ 30,616	$ 30,616
Charge-offs	(387)		(613)	(1,001)	(1,755)
Recoveries	653	230	1,213	1,122	1,885
Provision (benefit)	(145)	22,089	(6,385)	30,089	42,188
Ending balance	86,062	79,739	86,062	79,739	91,847
Off-Balance Sheet, Credit Loss, Liability [Roll Forward]
Beginning balance	3,580	2,845	3,400	2,775	2,775
Charge-offs	0		0	0	0
Recoveries	0	0	0	0	0
Provision (benefit)	(115)	154	65	224	625
Ending balance	3,465	2,999	3,465	2,999	3,400
Credit Loss [Roll Forward]
Beginning balance	89,521	60,756	95,247	33,391	33,391
Charge-offs	(387)		(613)	(1,001)	(1,755)
Recoveries	653	230	1,213	1,122	1,885
Provision (benefit)	(260)	22,243	(6,320)	30,313	42,813
Ending balance	89,527	82,738	89,527	82,738	95,247
Impact of CECL Adoption
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance				18,913	18,913
Charge-offs		(491)
Off-Balance Sheet, Credit Loss, Liability [Roll Forward]
Beginning balance				0	0
Charge-offs		0
Credit Loss [Roll Forward]
Beginning balance				18,913	18,913
Charge-offs		(491)
Commercial real estate
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	50,403	29,253	53,693	11,995	11,995
Charge-offs	0	0	0	0	(182)
Recoveries	0	9	3	202	226
Provision (benefit)	1,234	15,588	(2,059)	20,805	29,806
Ending balance	51,637	44,850	51,637	44,850	53,693
Commercial real estate | Impact of CECL Adoption
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance				11,848	11,848
Consumer
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	24,604	19,592	25,148	10,084	10,084
Charge-offs	(86)	(277)	(279)	(407)	(799)
Recoveries	572	166	973	719	1,067
Provision (benefit)	(1,140)	3,684	(1,892)	4,485	6,512
Ending balance	23,950	23,165	23,950	23,165	25,148
Consumer | Impact of CECL Adoption
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance				8,284	8,284
Commercial and industrial
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	4,464	3,867	4,252	4,867	4,867
Charge-offs	(301)	(214)	(334)	(594)	(774)
Recoveries	79	55	215	181	568
Provision (benefit)	269	310	378	1,525	1,552
Ending balance	4,511	4,018	4,511	4,018	4,252
Commercial and industrial | Impact of CECL Adoption
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance				(1,961)	(1,961)
Construction
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	5,476	4,595	7,540	3,388	3,388
Charge-offs	0	0	0	0	0
Recoveries	0	0	0	0	0
Provision (benefit)	(525)	2,180	(2,589)	2,454	3,219
Ending balance	4,951	6,775	4,951	6,775	7,540
Construction | Impact of CECL Adoption
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance				933	933
Agriculture production
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	988	593	1,209	261	261
Charge-offs	0	0	0	0	0
Recoveries	2	0	22	20	24
Provision (benefit)	17	326	(224)	817	1,103
Ending balance	1,007	919	1,007	919	1,209
Agriculture production | Impact of CECL Adoption
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance				(179)	(179)
Leases
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	6	11	5	21	21
Charge-offs	0	0	0	0	0
Recoveries	0	0	0	0	0
Provision (benefit)	0	1	1	3	(4)
Ending balance	6	12	6	12	5
Leases | Impact of CECL Adoption
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance				(12)	(12)
CRE non-owner occupied | Commercial real estate
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	26,434	18,034	29,380	5,948	5,948
Charge-offs	0	0	0	0	0
Recoveries	0	5	2	193	198
Provision (benefit)	(406)	8,052	(3,354)	13,249	16,533
Ending balance	26,028	26,091	26,028	26,091	29,380
CRE non-owner occupied | Commercial real estate | Impact of CECL Adoption
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance				6,701	6,701
CRE owner occupied | Commercial real estate
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	9,874	5,366	10,861	2,027	2,027
Charge-offs	0	0	0	0	0
Recoveries	0	4	1	9	28
Provision (benefit)	589	3,340	(399)	4,393	6,525
Ending balance	10,463	8,710	10,463	8,710	10,861
CRE owner occupied | Commercial real estate | Impact of CECL Adoption
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance				2,281	2,281
Multifamily | Commercial real estate
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	12,371	5,140	11,472	3,352	3,352
Charge-offs	0	0	0	0	0
Recoveries	0	0	0	0	0
Provision (benefit)	825	3,441	1,724	2,948	5,839
Ending balance	13,196	8,581	13,196	8,581	11,472
Multifamily | Commercial real estate | Impact of CECL Adoption
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance				2,281	2,281
Farmland | Commercial real estate
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	1,724	713	1,980	668	668
Charge-offs	0	0	0	0	(182)
Recoveries	0	0	0	0	0
Provision (benefit)	226	755	(30)	215	909
Ending balance	1,950	1,468	1,950	1,468	1,980
Farmland | Commercial real estate | Impact of CECL Adoption
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance				585	585
SFR 1-4 1st DT liens | Consumer
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	10,665	5,650	10,117	2,306	2,306
Charge-offs	0	(11)	0	(11)	(13)
Recoveries	1	2	11	412	416
Provision (benefit)	(37)	2,374	501	2,633	4,733
Ending balance	10,629	8,015	10,629	8,015	10,117
SFR 1-4 1st DT liens | Consumer | Impact of CECL Adoption
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance				2,675	2,675
SFR HELOCs and junior liens | Consumer
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	11,079	11,196	11,771	6,183	6,183
Charge-offs	0	(23)	0	(23)	(116)
Recoveries	512	92	797	140	304
Provision (benefit)	(890)	843	(1,867)	1,170	762
Ending balance	10,701	12,108	10,701	12,108	11,771
SFR HELOCs and junior liens | Consumer | Impact of CECL Adoption
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance				4,638	4,638
Other | Consumer
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	2,860	2,746	3,260	1,595	1,595
Charge-offs	(86)	(243)	(279)	(373)	(670)
Recoveries	59	72	165	167	347
Provision (benefit)	(213)	467	(526)	682	1,017
Ending balance	$ 2,620	$ 3,042	$ 2,620	3,042	3,260
Other | Consumer | Impact of CECL Adoption
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance				$ 971	$ 971