Allowance for Credit Losses - Schedule of Non Accrual Loans (Detail) - Financial asset originated - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Financing Receivable, Past Due [Line Items]
Non accrual with no allowance for credit losses	$ 21,703	$ 13,909
Non accrual, no allowance including guaranteed loans	22,390	14,825
Non accrual including guaranteed loans	26,864	16,845
Total non accrual	26,053	15,855
Loans Insured or Guaranteed by US Government Authorities
Financing Receivable, Past Due [Line Items]
Non accrual with no allowance for credit losses	687	916
Total non accrual	811	990
Financial Asset, Equal to or Greater than 90 Days Past Due
Financing Receivable, Past Due [Line Items]
Past due 90 days or more and still accruing	0	19
Commercial real estate
Financing Receivable, Past Due [Line Items]
Non accrual with no allowance for credit losses	7,689	5,316
Total non accrual	8,709	5,316
Commercial real estate | Financial Asset, Equal to or Greater than 90 Days Past Due
Financing Receivable, Past Due [Line Items]
Past due 90 days or more and still accruing	0	0
Consumer
Financing Receivable, Past Due [Line Items]
Non accrual with no allowance for credit losses	9,498	9,019
Total non accrual	11,408	9,441
Consumer | Financial Asset, Equal to or Greater than 90 Days Past Due
Financing Receivable, Past Due [Line Items]
Past due 90 days or more and still accruing	0	19
Commercial and industrial
Financing Receivable, Past Due [Line Items]
Non accrual with no allowance for credit losses	652	476
Total non accrual	2,183	2,050
Commercial and industrial | Financial Asset, Equal to or Greater than 90 Days Past Due
Financing Receivable, Past Due [Line Items]
Past due 90 days or more and still accruing	0	0
Construction
Financing Receivable, Past Due [Line Items]
Non accrual with no allowance for credit losses	4,546	0
Total non accrual	4,546	0
Construction | Financial Asset, Equal to or Greater than 90 Days Past Due
Financing Receivable, Past Due [Line Items]
Past due 90 days or more and still accruing	0	0
Agriculture production
Financing Receivable, Past Due [Line Items]
Non accrual with no allowance for credit losses	5	14
Total non accrual	18	38
Agriculture production | Financial Asset, Equal to or Greater than 90 Days Past Due
Financing Receivable, Past Due [Line Items]
Past due 90 days or more and still accruing	0	0
Leases
Financing Receivable, Past Due [Line Items]
Non accrual with no allowance for credit losses
Total non accrual	0
Leases | Financial Asset, Equal to or Greater than 90 Days Past Due
Financing Receivable, Past Due [Line Items]
Past due 90 days or more and still accruing	0	0
CRE non-owner occupied | Commercial real estate
Financing Receivable, Past Due [Line Items]
Non accrual with no allowance for credit losses	3,110	639
Total non accrual	3,110	642
CRE non-owner occupied | Commercial real estate | Financial Asset, Equal to or Greater than 90 Days Past Due
Financing Receivable, Past Due [Line Items]
Past due 90 days or more and still accruing	0	0
CRE owner occupied | Commercial real estate
Financing Receivable, Past Due [Line Items]
Non accrual with no allowance for credit losses	3,111	1,411
Total non accrual	4,061	1,408
CRE owner occupied | Commercial real estate | Financial Asset, Equal to or Greater than 90 Days Past Due
Financing Receivable, Past Due [Line Items]
Past due 90 days or more and still accruing	0	0
Multifamily | Commercial real estate
Financing Receivable, Past Due [Line Items]
Non accrual with no allowance for credit losses	0	2,024
Total non accrual	0	2,024
Multifamily | Commercial real estate | Financial Asset, Equal to or Greater than 90 Days Past Due
Financing Receivable, Past Due [Line Items]
Past due 90 days or more and still accruing	0	0
Farmland | Commercial real estate
Financing Receivable, Past Due [Line Items]
Non accrual with no allowance for credit losses	1,468	1,242
Total non accrual	1,538	1,242
Farmland | Commercial real estate | Financial Asset, Equal to or Greater than 90 Days Past Due
Financing Receivable, Past Due [Line Items]
Past due 90 days or more and still accruing	0	0
SFR 1-4 1st DT liens | Consumer
Financing Receivable, Past Due [Line Items]
Non accrual with no allowance for credit losses	4,950	5,023
Total non accrual	5,093	5,192
SFR 1-4 1st DT liens | Consumer | Financial Asset, Equal to or Greater than 90 Days Past Due
Financing Receivable, Past Due [Line Items]
Past due 90 days or more and still accruing	0	0
SFR HELOCs and junior liens | Consumer
Financing Receivable, Past Due [Line Items]
Non accrual with no allowance for credit losses	4,480	3,992
Total non accrual	6,148	4,217
SFR HELOCs and junior liens | Consumer | Financial Asset, Equal to or Greater than 90 Days Past Due
Financing Receivable, Past Due [Line Items]
Past due 90 days or more and still accruing	0	0
Other | Consumer
Financing Receivable, Past Due [Line Items]
Non accrual with no allowance for credit losses	68	4
Total non accrual	167	32
Other | Consumer | Financial Asset, Equal to or Greater than 90 Days Past Due
Financing Receivable, Past Due [Line Items]
Past due 90 days or more and still accruing	$ 0	$ 19