Allowance for Credit Losses - Analysis of Past Due and Nonaccrual Loans (Detail) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Financing Receivable, Past Due [Line Items]
Total	$ 4,763,127	$ 4,307,366
Commercial real estate
Financing Receivable, Past Due [Line Items]
Total	2,951,902	2,818,782
Consumer
Financing Receivable, Past Due [Line Items]
Total	952,108	955,050
Commercial and industrial
Financing Receivable, Past Due [Line Items]
Total	526,327	249,791
Construction
Financing Receivable, Past Due [Line Items]
Total	284,842	249,827
Agriculture production
Financing Receivable, Past Due [Line Items]
Total	44,164	32,633
Leases
Financing Receivable, Past Due [Line Items]
Total	3,784	1,283
CRE non-owner occupied | Commercial real estate
Financing Receivable, Past Due [Line Items]
Total	1,535,555	1,609,556
CRE owner occupied | Commercial real estate
Financing Receivable, Past Due [Line Items]
Total	624,375	546,434
Multifamily | Commercial real estate
Financing Receivable, Past Due [Line Items]
Total	639,480	517,725
Farmland | Commercial real estate
Financing Receivable, Past Due [Line Items]
Total	152,492	145,067
SFR 1-4 1st DT liens | Commercial real estate
Financing Receivable, Past Due [Line Items]
Total	546,592
SFR 1-4 1st DT liens | Consumer
Financing Receivable, Past Due [Line Items]
Total		509,508
SFR HELOCs and junior liens | Consumer
Financing Receivable, Past Due [Line Items]
Total	327,484	362,886
Other | Consumer
Financing Receivable, Past Due [Line Items]
Total	78,032	82,656
Financial asset originated
Financing Receivable, Past Due [Line Items]
Past due	6,767	10,720
Current	4,756,360	4,296,646
Total	4,763,127	4,307,366
Financial asset originated | Commercial real estate
Financing Receivable, Past Due [Line Items]
Past due	2,629	3,148
Current	2,949,273	2,815,634
Total	2,951,902	2,818,782
Financial asset originated | Consumer
Financing Receivable, Past Due [Line Items]
Past due	3,452	6,599
Current	948,656	948,451
Total	952,108	955,050
Financial asset originated | Commercial and industrial
Financing Receivable, Past Due [Line Items]
Past due	686	924
Current	525,641	248,867
Total	526,327	249,791
Financial asset originated | Construction
Financing Receivable, Past Due [Line Items]
Past due	0	0
Current	284,842	249,827
Total	284,842	249,827
Financial asset originated | Agriculture production
Financing Receivable, Past Due [Line Items]
Past due	0	49
Current	44,164	32,584
Total	44,164	32,633
Financial asset originated | Leases
Financing Receivable, Past Due [Line Items]
Past due	0	0
Current	3,784	1,283
Total	3,784	1,283
Financial asset originated | CRE non-owner occupied | Commercial real estate
Financing Receivable, Past Due [Line Items]
Past due	539	518
Current	1,535,016	1,609,038
Total	1,535,555	1,609,556
Financial asset originated | CRE owner occupied | Commercial real estate
Financing Receivable, Past Due [Line Items]
Past due	1,121	293
Current	623,254	546,141
Total	624,375	546,434
Financial asset originated | Multifamily | Commercial real estate
Financing Receivable, Past Due [Line Items]
Past due	0	2,307
Current	639,480	515,418
Total	639,480	517,725
Financial asset originated | Farmland | Commercial real estate
Financing Receivable, Past Due [Line Items]
Past due	969	30
Current	151,523	145,037
Total	152,492	145,067
Financial asset originated | SFR 1-4 1st DT liens | Consumer
Financing Receivable, Past Due [Line Items]
Past due	997	3,477
Current	545,595	506,031
Total	546,592	509,508
Financial asset originated | SFR HELOCs and junior liens | Consumer
Financing Receivable, Past Due [Line Items]
Past due	2,301	2,926
Current	325,183	359,960
Total	327,484	362,886
Financial asset originated | Other | Consumer
Financing Receivable, Past Due [Line Items]
Past due	154	196
Current	77,878	82,460
Total	78,032	82,656
Financial Asset, 30 to 59 Days Past Due | Financial asset originated
Financing Receivable, Past Due [Line Items]
Past due	1,974	3,812
Financial Asset, 30 to 59 Days Past Due | Financial asset originated | Commercial real estate
Financing Receivable, Past Due [Line Items]
Past due	1,323	581
Financial Asset, 30 to 59 Days Past Due | Financial asset originated | Consumer
Financing Receivable, Past Due [Line Items]
Past due	496	2,579
Financial Asset, 30 to 59 Days Past Due | Financial asset originated | Commercial and industrial
Financing Receivable, Past Due [Line Items]
Past due	155	603
Financial Asset, 30 to 59 Days Past Due | Financial asset originated | Construction
Financing Receivable, Past Due [Line Items]
Past due	0	0
Financial Asset, 30 to 59 Days Past Due | Financial asset originated | Agriculture production
Financing Receivable, Past Due [Line Items]
Past due	0	49
Financial Asset, 30 to 59 Days Past Due | Financial asset originated | Leases
Financing Receivable, Past Due [Line Items]
Past due	0	0
Financial Asset, 30 to 59 Days Past Due | Financial asset originated | CRE non-owner occupied | Commercial real estate
Financing Receivable, Past Due [Line Items]
Past due	127	268
Financial Asset, 30 to 59 Days Past Due | Financial asset originated | CRE owner occupied | Commercial real estate
Financing Receivable, Past Due [Line Items]
Past due	297	0
Financial Asset, 30 to 59 Days Past Due | Financial asset originated | Multifamily | Commercial real estate
Financing Receivable, Past Due [Line Items]
Past due	0	283
Financial Asset, 30 to 59 Days Past Due | Financial asset originated | Farmland | Commercial real estate
Financing Receivable, Past Due [Line Items]
Past due	899	30
Financial Asset, 30 to 59 Days Past Due | Financial asset originated | SFR 1-4 1st DT liens | Consumer
Financing Receivable, Past Due [Line Items]
Past due	37	1,149
Financial Asset, 30 to 59 Days Past Due | Financial asset originated | SFR HELOCs and junior liens | Consumer
Financing Receivable, Past Due [Line Items]
Past due	418	1,258
Financial Asset, 30 to 59 Days Past Due | Financial asset originated | Other | Consumer
Financing Receivable, Past Due [Line Items]
Past due	41	172
Financial Asset, 60 to 89 Days Past Due | Financial asset originated
Financing Receivable, Past Due [Line Items]
Past due	824	1,385
Financial Asset, 60 to 89 Days Past Due | Financial asset originated | Commercial real estate
Financing Receivable, Past Due [Line Items]
Past due	173	136
Financial Asset, 60 to 89 Days Past Due | Financial asset originated | Consumer
Financing Receivable, Past Due [Line Items]
Past due	225	952
Financial Asset, 60 to 89 Days Past Due | Financial asset originated | Commercial and industrial
Financing Receivable, Past Due [Line Items]
Past due	426	297
Financial Asset, 60 to 89 Days Past Due | Financial asset originated | Construction
Financing Receivable, Past Due [Line Items]
Past due	0	0
Financial Asset, 60 to 89 Days Past Due | Financial asset originated | Agriculture production
Financing Receivable, Past Due [Line Items]
Past due	0	0
Financial Asset, 60 to 89 Days Past Due | Financial asset originated | Leases
Financing Receivable, Past Due [Line Items]
Past due	0	0
Financial Asset, 60 to 89 Days Past Due | Financial asset originated | CRE non-owner occupied | Commercial real estate
Financing Receivable, Past Due [Line Items]
Past due	173	136
Financial Asset, 60 to 89 Days Past Due | Financial asset originated | CRE owner occupied | Commercial real estate
Financing Receivable, Past Due [Line Items]
Past due	0	0
Financial Asset, 60 to 89 Days Past Due | Financial asset originated | Multifamily | Commercial real estate
Financing Receivable, Past Due [Line Items]
Past due	0	0
Financial Asset, 60 to 89 Days Past Due | Financial asset originated | Farmland | Commercial real estate
Financing Receivable, Past Due [Line Items]
Past due	0	0
Financial Asset, 60 to 89 Days Past Due | Financial asset originated | SFR 1-4 1st DT liens | Consumer
Financing Receivable, Past Due [Line Items]
Past due	0	371
Financial Asset, 60 to 89 Days Past Due | Financial asset originated | SFR HELOCs and junior liens | Consumer
Financing Receivable, Past Due [Line Items]
Past due	212	580
Financial Asset, 60 to 89 Days Past Due | Financial asset originated | Other | Consumer
Financing Receivable, Past Due [Line Items]
Past due	13	1
Financial Asset, Equal to or Greater than 90 Days Past Due | Financial asset originated
Financing Receivable, Past Due [Line Items]
Past due	3,969	5,523
Financial Asset, Equal to or Greater than 90 Days Past Due | Financial asset originated | Commercial real estate
Financing Receivable, Past Due [Line Items]
Past due	1,133	2,431
Financial Asset, Equal to or Greater than 90 Days Past Due | Financial asset originated | Consumer
Financing Receivable, Past Due [Line Items]
Past due	2,731	3,068
Financial Asset, Equal to or Greater than 90 Days Past Due | Financial asset originated | Commercial and industrial
Financing Receivable, Past Due [Line Items]
Past due	105	24
Financial Asset, Equal to or Greater than 90 Days Past Due | Financial asset originated | Construction
Financing Receivable, Past Due [Line Items]
Past due	0	0
Financial Asset, Equal to or Greater than 90 Days Past Due | Financial asset originated | Agriculture production
Financing Receivable, Past Due [Line Items]
Past due	0	0
Financial Asset, Equal to or Greater than 90 Days Past Due | Financial asset originated | Leases
Financing Receivable, Past Due [Line Items]
Past due	0	0
Financial Asset, Equal to or Greater than 90 Days Past Due | Financial asset originated | CRE non-owner occupied | Commercial real estate
Financing Receivable, Past Due [Line Items]
Past due	239	114
Financial Asset, Equal to or Greater than 90 Days Past Due | Financial asset originated | CRE owner occupied | Commercial real estate
Financing Receivable, Past Due [Line Items]
Past due	824	293
Financial Asset, Equal to or Greater than 90 Days Past Due | Financial asset originated | Multifamily | Commercial real estate
Financing Receivable, Past Due [Line Items]
Past due	0	2,024
Financial Asset, Equal to or Greater than 90 Days Past Due | Financial asset originated | Farmland | Commercial real estate
Financing Receivable, Past Due [Line Items]
Past due	70	0
Financial Asset, Equal to or Greater than 90 Days Past Due | Financial asset originated | SFR 1-4 1st DT liens | Consumer
Financing Receivable, Past Due [Line Items]
Past due	960	1,957
Financial Asset, Equal to or Greater than 90 Days Past Due | Financial asset originated | SFR HELOCs and junior liens | Consumer
Financing Receivable, Past Due [Line Items]
Past due	1,671	1,088
Financial Asset, Equal to or Greater than 90 Days Past Due | Financial asset originated | Other | Consumer
Financing Receivable, Past Due [Line Items]
Past due	$ 100	$ 23