Loans - Summary of Loan Balances (Detail) - USD ($) $ in Thousands	Dec. 31, 2020	Jan. 01, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Loans and Leases Receivable Disclosure [Line Items]
Total	$ 4,763,127		$ 4,307,366
Total principal balance of loans owed, net of charge-offs	4,805,596		4,351,725
Unamortized net deferred loan fees	(16,984)		(8,927)
Discounts to principal balance of loans owed, net of charge-offs	(25,485)		(35,432)
Allowance for credit losses	(91,847)	$ (49,529)	(30,616)	$ (32,582)	$ (30,323)
Commercial real estate
Loans and Leases Receivable Disclosure [Line Items]
Total	2,951,902		2,818,782
Allowance for credit losses	(53,693)		(11,995)	(12,944)	(11,441)
Consumer
Loans and Leases Receivable Disclosure [Line Items]
Total	952,108		955,050
Allowance for credit losses	(25,148)		(10,084)	(11,051)	(10,544)
Commercial and industrial
Loans and Leases Receivable Disclosure [Line Items]
Total	526,327		249,791
Allowance for credit losses	(4,252)		(4,867)	(5,610)	(5,757)
Construction
Loans and Leases Receivable Disclosure [Line Items]
Total	284,842		249,827
Allowance for credit losses	(7,540)		(3,388)	(2,497)	(1,826)
Agriculture production
Loans and Leases Receivable Disclosure [Line Items]
Total	44,164		32,633
Allowance for credit losses	(1,209)		(261)	(480)	(755)
Leases
Loans and Leases Receivable Disclosure [Line Items]
Total	3,784		1,283
Allowance for credit losses	(5)		(21)	0	0
CRE non-owner occupied | Commercial real estate
Loans and Leases Receivable Disclosure [Line Items]
Total	1,535,555		1,609,556
Allowance for credit losses	(29,380)		(5,948)	(7,401)	(6,693)
CRE owner occupied | Commercial real estate
Loans and Leases Receivable Disclosure [Line Items]
Total	624,375		546,434
Allowance for credit losses	(10,861)		(2,027)	(2,711)	(2,686)
Multifamily | Commercial real estate
Loans and Leases Receivable Disclosure [Line Items]
Total	639,480		517,725
Allowance for credit losses	(11,472)		(3,352)	(2,429)	(1,491)
Farmland | Commercial real estate
Loans and Leases Receivable Disclosure [Line Items]
Total	152,492		145,067
Allowance for credit losses	(1,980)		(668)	(403)	(571)
SFR 1-4 1st DT liens | Consumer
Loans and Leases Receivable Disclosure [Line Items]
Total	546,592		509,508
SFR HELOCs and junior liens | Consumer
Loans and Leases Receivable Disclosure [Line Items]
Total	327,484		362,886
Allowance for credit losses	(11,771)		(6,183)	(7,582)	(7,641)
Other | Consumer
Loans and Leases Receivable Disclosure [Line Items]
Total	78,032		82,656
Allowance for credit losses	$ (3,260)		$ (1,595)	$ (793)	$ (586)