Allowance for Credit Losses - Troubled Debt Restructurings (Detail) $ in Thousands	3 Months Ended
	Mar. 31, 2022 USD ($) investmentSecurity	Mar. 31, 2021 USD ($) investmentSecurity
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number (in investment securities) | investmentSecurity	3,000	5,000
Pre-mod outstanding principal balance	$ 1,228	$ 1,373
Post-mod outstanding principal balance	1,440	1,366
Financial impact due to TDR taken as additional provision	$ 0	$ 1,366
Number that defaulted during the period (in investment securities) | investmentSecurity	0	4,000
Recorded investment of TDRs that defaulted during the period	$ 0	$ 1,094
Financial impact due to the default of previous TDR taken as charge- offs or additional provisions	$ 0	$ 0
Commercial real estate
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number (in investment securities) | investmentSecurity	3,000	2,000
Pre-mod outstanding principal balance	$ 1,228	$ 1,057
Post-mod outstanding principal balance	1,440	1,056
Financial impact due to TDR taken as additional provision	$ 0	$ 1,056
Number that defaulted during the period (in investment securities) | investmentSecurity	0	3,000
Recorded investment of TDRs that defaulted during the period	$ 0	$ 847
Financial impact due to the default of previous TDR taken as charge- offs or additional provisions	$ 0	$ 0
Consumer
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number (in investment securities) | investmentSecurity	0	0
Pre-mod outstanding principal balance	$ 0	$ 0
Post-mod outstanding principal balance	0	0
Financial impact due to TDR taken as additional provision	$ 0	$ 0
Number that defaulted during the period (in investment securities) | investmentSecurity	0	0
Recorded investment of TDRs that defaulted during the period	$ 0	$ 0
Financial impact due to the default of previous TDR taken as charge- offs or additional provisions	$ 0	$ 0
Commercial and industrial
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number (in investment securities) | investmentSecurity	0	3,000
Pre-mod outstanding principal balance	$ 0	$ 316
Post-mod outstanding principal balance	0	310
Financial impact due to TDR taken as additional provision	$ 0	$ 310
Number that defaulted during the period (in investment securities) | investmentSecurity	0	1,000
Recorded investment of TDRs that defaulted during the period	$ 0	$ 247
Financial impact due to the default of previous TDR taken as charge- offs or additional provisions	$ 0	$ 0
Construction
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number (in investment securities) | investmentSecurity	0	0
Pre-mod outstanding principal balance	$ 0	$ 0
Post-mod outstanding principal balance	0	0
Financial impact due to TDR taken as additional provision	$ 0	$ 0
Number that defaulted during the period (in investment securities) | investmentSecurity	0	0
Recorded investment of TDRs that defaulted during the period	$ 0	$ 0
Financial impact due to the default of previous TDR taken as charge- offs or additional provisions	$ 0	$ 0
Agriculture production
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number (in investment securities) | investmentSecurity	0	0
Pre-mod outstanding principal balance	$ 0	$ 0
Post-mod outstanding principal balance	0	0
Financial impact due to TDR taken as additional provision	$ 0	$ 0
Number that defaulted during the period (in investment securities) | investmentSecurity	0	0
Recorded investment of TDRs that defaulted during the period	$ 0	$ 0
Financial impact due to the default of previous TDR taken as charge- offs or additional provisions	$ 0	$ 0
Leases
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number (in investment securities) | investmentSecurity	0	0
Pre-mod outstanding principal balance	$ 0	$ 0
Post-mod outstanding principal balance	0	0
Financial impact due to TDR taken as additional provision	$ 0	$ 0
Number that defaulted during the period (in investment securities) | investmentSecurity	0	0
Recorded investment of TDRs that defaulted during the period	$ 0	$ 0
Financial impact due to the default of previous TDR taken as charge- offs or additional provisions	$ 0	$ 0
CRE non-owner occupied | Commercial real estate
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number (in investment securities) | investmentSecurity	0	1,000
Pre-mod outstanding principal balance	$ 0	$ 317
Post-mod outstanding principal balance	0	314
Financial impact due to TDR taken as additional provision	$ 0	$ 314
Number that defaulted during the period (in investment securities) | investmentSecurity	0	0
Recorded investment of TDRs that defaulted during the period	$ 0	$ 0
Financial impact due to the default of previous TDR taken as charge- offs or additional provisions	$ 0	$ 0
CRE owner occupied | Commercial real estate
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number (in investment securities) | investmentSecurity	0	1,000
Pre-mod outstanding principal balance	$ 0	$ 740
Post-mod outstanding principal balance	0	742
Financial impact due to TDR taken as additional provision	$ 0	$ 742
Number that defaulted during the period (in investment securities) | investmentSecurity	0	0
Recorded investment of TDRs that defaulted during the period	$ 0	$ 0
Financial impact due to the default of previous TDR taken as charge- offs or additional provisions	$ 0	$ 0
Multifamily | Commercial real estate
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number (in investment securities) | investmentSecurity	0	0
Pre-mod outstanding principal balance	$ 0	$ 0
Post-mod outstanding principal balance	0	0
Financial impact due to TDR taken as additional provision	$ 0	$ 0
Number that defaulted during the period (in investment securities) | investmentSecurity	0	0
Recorded investment of TDRs that defaulted during the period	$ 0	$ 0
Financial impact due to the default of previous TDR taken as charge- offs or additional provisions	$ 0	$ 0
Farmland | Commercial real estate
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number (in investment securities) | investmentSecurity	3,000	0
Pre-mod outstanding principal balance	$ 1,228	$ 0
Post-mod outstanding principal balance	1,440	0
Financial impact due to TDR taken as additional provision	$ 0	$ 0
Number that defaulted during the period (in investment securities) | investmentSecurity	0	3,000
Recorded investment of TDRs that defaulted during the period	$ 0	$ 847
Financial impact due to the default of previous TDR taken as charge- offs or additional provisions	$ 0	$ 0
SFR 1-4 1st DT liens | Consumer
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number (in investment securities) | investmentSecurity	0	0
Pre-mod outstanding principal balance	$ 0	$ 0
Post-mod outstanding principal balance	0	0
Financial impact due to TDR taken as additional provision	$ 0	$ 0
Number that defaulted during the period (in investment securities) | investmentSecurity	0	0
Recorded investment of TDRs that defaulted during the period	$ 0	$ 0
Financial impact due to the default of previous TDR taken as charge- offs or additional provisions	$ 0	$ 0
SFR HELOCs and junior liens | Consumer
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number (in investment securities) | investmentSecurity	0	0
Pre-mod outstanding principal balance	$ 0	$ 0
Post-mod outstanding principal balance	0	0
Financial impact due to TDR taken as additional provision	$ 0	$ 0
Number that defaulted during the period (in investment securities) | investmentSecurity	0	0
Recorded investment of TDRs that defaulted during the period	$ 0	$ 0
Financial impact due to the default of previous TDR taken as charge- offs or additional provisions	$ 0	$ 0
Other | Consumer
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number (in investment securities) | investmentSecurity	0	0
Pre-mod outstanding principal balance	$ 0	$ 0
Post-mod outstanding principal balance	0	0
Financial impact due to TDR taken as additional provision	$ 0	$ 0
Number that defaulted during the period (in investment securities) | investmentSecurity	0	0
Recorded investment of TDRs that defaulted during the period	$ 0	$ 0
Financial impact due to the default of previous TDR taken as charge- offs or additional provisions	$ 0	$ 0