Allowance for Credit Losses - Analysis of Past Due and Nonaccrual Loans (Detail) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Financing Receivable, Past Due [Line Items]
Total	$ 4,944,894	$ 4,763,127
Commercial real estate
Financing Receivable, Past Due [Line Items]
Total	3,194,336	2,951,902
Consumer
Financing Receivable, Past Due [Line Items]
Total	1,050,609	952,108
Commercial and industrial
Financing Receivable, Past Due [Line Items]
Total	452,069	526,327
Construction
Financing Receivable, Past Due [Line Items]
Total	200,714	284,842
Agriculture production
Financing Receivable, Past Due [Line Items]
Total	41,967	44,164
Leases
Financing Receivable, Past Due [Line Items]
Total	5,199	3,784
CRE non-owner occupied | Commercial real estate
Financing Receivable, Past Due [Line Items]
Total	1,534,256	1,535,555
CRE owner occupied | Commercial real estate
Financing Receivable, Past Due [Line Items]
Total	659,948	624,375
Multifamily | Commercial real estate
Financing Receivable, Past Due [Line Items]
Total	828,101	639,480
Farmland | Commercial real estate
Financing Receivable, Past Due [Line Items]
Total	172,031	152,492
SFR 1-4 1st DT liens | Consumer
Financing Receivable, Past Due [Line Items]
Total	654,373	546,592
SFR HELOCs and junior liens | Consumer
Financing Receivable, Past Due [Line Items]
Total	325,127	327,484
Other | Consumer
Financing Receivable, Past Due [Line Items]
Total	71,109	78,032
Financial Asset Originated
Financing Receivable, Past Due [Line Items]
Past due	9,292	6,767
Current	4,935,602	4,756,360
Total	4,944,894	4,763,127
Financial Asset Originated | Commercial real estate
Financing Receivable, Past Due [Line Items]
Past due	5,653	2,629
Current	3,188,683	2,949,273
Total	3,194,336	2,951,902
Financial Asset Originated | Consumer
Financing Receivable, Past Due [Line Items]
Past due	2,810	3,452
Current	1,047,799	948,656
Total	1,050,609	952,108
Financial Asset Originated | Commercial and industrial
Financing Receivable, Past Due [Line Items]
Past due	588	686
Current	451,481	525,641
Total	452,069	526,327
Financial Asset Originated | Construction
Financing Receivable, Past Due [Line Items]
Past due	0	0
Current	200,714	284,842
Total	200,714	284,842
Financial Asset Originated | Agriculture production
Financing Receivable, Past Due [Line Items]
Past due	241	0
Current	41,726	44,164
Total	41,967	44,164
Financial Asset Originated | Leases
Financing Receivable, Past Due [Line Items]
Past due	0	0
Current	5,199	3,784
Total	5,199	3,784
Financial Asset Originated | CRE non-owner occupied | Commercial real estate
Financing Receivable, Past Due [Line Items]
Past due	4,305	539
Current	1,529,951	1,535,016
Total	1,534,256	1,535,555
Financial Asset Originated | CRE owner occupied | Commercial real estate
Financing Receivable, Past Due [Line Items]
Past due	502	1,121
Current	659,446	623,254
Total	659,948	624,375
Financial Asset Originated | Multifamily | Commercial real estate
Financing Receivable, Past Due [Line Items]
Past due	0	0
Current	828,101	639,480
Total	828,101	639,480
Financial Asset Originated | Farmland | Commercial real estate
Financing Receivable, Past Due [Line Items]
Past due	846	969
Current	171,185	151,523
Total	172,031	152,492
Financial Asset Originated | SFR 1-4 1st DT liens | Consumer
Financing Receivable, Past Due [Line Items]
Past due	423	997
Current	653,950	545,595
Total	654,373	546,592
Financial Asset Originated | SFR HELOCs and junior liens | Consumer
Financing Receivable, Past Due [Line Items]
Past due	2,322	2,301
Current	322,805	325,183
Total	325,127	327,484
Financial Asset Originated | Other | Consumer
Financing Receivable, Past Due [Line Items]
Past due	65	154
Current	71,044	77,878
Total	71,109	78,032
Financial Asset, 30 to 59 Days Past Due | Financial Asset Originated
Financing Receivable, Past Due [Line Items]
Past due	1,563	1,974
Financial Asset, 30 to 59 Days Past Due | Financial Asset Originated | Commercial real estate
Financing Receivable, Past Due [Line Items]
Past due	365	1,323
Financial Asset, 30 to 59 Days Past Due | Financial Asset Originated | Consumer
Financing Receivable, Past Due [Line Items]
Past due	707	496
Financial Asset, 30 to 59 Days Past Due | Financial Asset Originated | Commercial and industrial
Financing Receivable, Past Due [Line Items]
Past due	250	155
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	241	0
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	337	127
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	28	297
Financial Asset, 30 to 59 Days Past Due | Financial Asset Originated | Multifamily | Commercial real estate
Financing Receivable, Past Due [Line Items]
Past due	0	0
Financial Asset, 30 to 59 Days Past Due | Financial Asset Originated | Farmland | Commercial real estate
Financing Receivable, Past Due [Line Items]
Past due	0	899
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	0	37
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	694	418
Financial Asset, 30 to 59 Days Past Due | Financial Asset Originated | Other | Consumer
Financing Receivable, Past Due [Line Items]
Past due	13	41
Financial Asset, 60 to 89 Days Past Due | Financial Asset Originated
Financing Receivable, Past Due [Line Items]
Past due	352	824
Financial Asset, 60 to 89 Days Past Due | Financial Asset Originated | Commercial real estate
Financing Receivable, Past Due [Line Items]
Past due	111	173
Financial Asset, 60 to 89 Days Past Due | Financial Asset Originated | Consumer
Financing Receivable, Past Due [Line Items]
Past due	63	225
Financial Asset, 60 to 89 Days Past Due | Financial Asset Originated | Commercial and industrial
Financing Receivable, Past Due [Line Items]
Past due	178	426
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	49	173
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	62
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	0
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	63	212
Financial Asset, 60 to 89 Days Past Due | Financial Asset Originated | Other | Consumer
Financing Receivable, Past Due [Line Items]
Past due	0	13
Financial Asset, Equal to or Greater than 90 Days Past Due | Financial Asset Originated
Financing Receivable, Past Due [Line Items]
Past due	7,377	3,969
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	5,177	1,133
Financial Asset, Equal to or Greater than 90 Days Past Due | Financial Asset Originated | Consumer
Financing Receivable, Past Due [Line Items]
Past due	2,040	2,731
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	160	105
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	3,919	239
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	412	824
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	0
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	846	70
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	423	960
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	1,565	1,671
Financial Asset, Equal to or Greater than 90 Days Past Due | Financial Asset Originated | Other | Consumer
Financing Receivable, Past Due [Line Items]
Past due	$ 52	$ 100