Allowance for Credit Losses - Summary of Activity in Allowance for Loan Losses (Detail) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	$ 91,847	$ 30,616	$ 30,616
Charge-offs	(226)	(510)	(1,755)
Recoveries	560	892	1,885
Provision (benefit)	(6,240)	8,000	42,188
Ending balance	85,941	57,911	91,847
Off-Balance Sheet, Credit Loss, Liability [Roll Forward]
Beginning balance	3,400	2,775	2,775
Charge-offs	0	0	0
Recoveries	0	0	0
Provision (benefit)	180	0	625
Ending balance	3,580	2,775	3,400
Credit Loss [Roll Forward]
Beginning balance	95,247	33,391	33,391
Charge-offs	(226)	(510)	(1,755)
Recoveries	560	892	1,885
Provision (benefit)	(6,060)	8,000	42,813
Ending balance	89,521	60,686	95,247
Impact of CECL Adoption
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance		18,913	18,913
Off-Balance Sheet, Credit Loss, Liability [Roll Forward]
Beginning balance		0	0
Credit Loss [Roll Forward]
Beginning balance		18,913	18,913
Commercial real estate
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	53,693	11,995	11,995
Charge-offs	0	0	(182)
Recoveries	3	194	226
Provision (benefit)	(3,293)	5,213	29,806
Ending balance	50,403	29,250	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	25,148	10,084	10,084
Charge-offs	(193)	(130)	(799)
Recoveries	401	552	1,067
Provision (benefit)	(752)	802	6,512
Ending balance	24,604	19,592	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	4,252	4,867	4,867
Charge-offs	(33)	(380)	(774)
Recoveries	136	126	568
Provision (benefit)	109	1,216	1,552
Ending balance	4,464	3,868	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	7,540	3,388	3,388
Charge-offs	0	0	0
Recoveries	0	0	0
Provision (benefit)	(2,064)	274	3,219
Ending balance	5,476	4,595	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	1,209	261	261
Charge-offs	0	0	0
Recoveries	20	20	24
Provision (benefit)	(241)	493	1,103
Ending balance	988	595	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	5	21	21
Charge-offs	0	0	0
Recoveries	0	0	0
Provision (benefit)	1	2	(4)
Ending balance	6	11	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	29,380	5,948	5,948
Charge-offs	0	0	0
Recoveries	2	189	198
Provision (benefit)	(2,948)	5,195	16,533
Ending balance	26,434	18,033	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	10,861	2,027	2,027
Charge-offs	0	0	0
Recoveries	1	5	28
Provision (benefit)	(988)	1,052	6,525
Ending balance	9,874	5,365	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	11,472	3,352	3,352
Charge-offs	0	0	0
Recoveries	0	0	0
Provision (benefit)	899	(493)	5,839
Ending balance	12,371	5,140	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	1,980	668	668
Charge-offs	0	0	(182)
Recoveries	0	0	0
Provision (benefit)	(256)	(541)	909
Ending balance	1,724	712	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	10,117	2,306	2,306
Charge-offs	0	0	(13)
Recoveries	10	410	416
Provision (benefit)	538	259	4,733
Ending balance	10,665	5,650	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	11,771	6,183	6,183
Charge-offs	0	0	(116)
Recoveries	285	48	304
Provision (benefit)	(977)	327	762
Ending balance	11,079	11,196	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	3,260	1,595	1,595
Charge-offs	(193)	(130)	(670)
Recoveries	106	94	347
Provision (benefit)	(313)	216	1,017
Ending balance	$ 2,860	2,746	3,260
Other \| Consumer \| Impact of CECL Adoption
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance		$ 971	$ 971

Credit Loss, Allowance For Credit Loss

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Credit Loss, Allowance For Credit Loss, Recovery

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Credit Loss, Allowance For Credit Loss, Writeoff

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Credit Loss, Expense (Reversal)

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Off Balance Sheet, Credit Loss, Recovery

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A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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Amount of allowance for credit loss on financing receivable. Excludes allowance for financing receivable covered under loss sharing agreement.

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Amount of recovery of financing receivables doubtful of collection that were previously charged off.

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Amount of writeoff of financing receivable, charged against allowance for credit loss.

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Amount of expected credit loss for credit exposure on off-balance-sheet commitment, including but not limited to, loan commitment, standby letter of credit, financial guarantee not accounted for as insurance. Excludes off-balance sheet credit exposure accounted for as insurance and instrument accounted for under derivatives and hedging.

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Amount of expense (reversal of expense) for expected credit loss for off-balance sheet credit exposure. Excludes off-balance sheet credit exposure accounted for as insurance and instrument accounted for under derivatives and hedging.

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Amount of credit loss expense (reversal of expense) for financing receivable.

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