Loans - Summary of Loan Balances (Detail) - USD ($) $ in Thousands	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018
Loans and Leases Receivable Disclosure [Line Items]
Total	$ 4,801,405		$ 4,307,366
Total principal balance of loans owed, net of charge-offs	4,854,351		4,351,725
Unamortized net deferred loan fees	(22,500)		(8,927)
Discounts to principal balance of loans owed, net of charge-offs	30,446		35,432
Allowance for loan losses	(79,739)	$ (57,911)	(30,616)	$ (32,868)	$ (32,064)	$ (32,582)
Commercial real estate
Loans and Leases Receivable Disclosure [Line Items]
Total	2,905,485		2,818,782
Allowance for loan losses	(44,850)	(29,253)	(11,995)	(12,099)	(12,330)	(12,944)
Consumer
Loans and Leases Receivable Disclosure [Line Items]
Total	945,669		955,050
Allowance for loan losses	(23,165)	(19,592)	(10,084)	(11,128)	(10,841)	(11,051)
Commercial and industrial
Loans and Leases Receivable Disclosure [Line Items]
Total	634,481		249,791
Allowance for loan losses	(4,018)	(3,867)	(4,867)	(6,481)	(5,854)	(5,610)
Construction
Loans and Leases Receivable Disclosure [Line Items]
Total	278,566		249,827
Allowance for loan losses	(6,775)	(4,595)	(3,388)	(2,896)	(2,815)	(2,497)
Agriculture production
Loans and Leases Receivable Disclosure [Line Items]
Total	35,441		32,633
Allowance for loan losses	(919)	(593)	(261)	(264)	(224)	(480)
Leases
Loans and Leases Receivable Disclosure [Line Items]
Total	1,763		1,283
Allowance for loan losses	(12)	(11)	(21)	0	0	0
CRE non-owner occupied | Commercial real estate
Loans and Leases Receivable Disclosure [Line Items]
Total	1,596,941		1,609,556
Allowance for loan losses	(26,091)	(18,034)	(5,948)	(6,182)	(6,268)	(7,401)
CRE owner occupied | Commercial real estate
Loans and Leases Receivable Disclosure [Line Items]
Total	579,803		546,434
Allowance for loan losses	(8,710)	(5,366)	(2,027)	(2,214)	(2,323)	(2,711)
Multifamily | Commercial real estate
Loans and Leases Receivable Disclosure [Line Items]
Total	577,217		517,725
Allowance for loan losses	(8,581)	(5,140)	(3,352)	(3,082)	(3,271)	(2,429)
Farmland | Commercial real estate
Loans and Leases Receivable Disclosure [Line Items]
Total	151,524		145,067
Allowance for loan losses	(1,468)	(713)	(668)	(621)	(468)	(403)
SFR 1-4 1st DT liens | Consumer
Loans and Leases Receivable Disclosure [Line Items]
Total	506,069		509,508
SFR HELOCs and junior liens | Consumer
Loans and Leases Receivable Disclosure [Line Items]
Total	358,087		362,886
Allowance for loan losses	(12,108)	(11,196)	(6,183)	(7,101)	(7,301)	(7,582)
Other | Consumer
Loans and Leases Receivable Disclosure [Line Items]
Total	81,513		82,656
Allowance for loan losses	$ (3,042)	$ (2,746)	$ (1,595)	$ (1,451)	$ (1,040)	$ (793)