Acquisitions - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended	3 Months Ended
	Mar. 26, 2019	Mar. 31, 2019	Dec. 31, 2018
Business Acquisition [Line Items]
Common stock, shares outstanding		45,052,747	38,375,407
Acquisition of goodwill		$ 145,690	$ 119,880
Salin Bank and Trust Company [Member]
Business Acquisition [Line Items]
Exchange ratio per share	23907.50%
Cash paid for each share	$ 87,417.17
Common stock, shares outstanding	275,000
Common stock issued	6,563,697
Market closing price per share	$ 15.65
Estimated transaction value	$ 126,700
Costs related to the acquisition	4,600
Total purchase price	126,722
Net intangible assets acquired	21,111
Acquisition of goodwill	$ 25,810
Core deposit intangible amortization period		10 years