Business Combinations - Summary of Total Consideration Paid (Details) - USD ($) $ in Thousands	Mar. 01, 2016	Dec. 31, 2017	Dec. 31, 2016
Business Acquisition [Line Items]
Common stock, shares issued (in shares)		27,019,201	26,318,400
American Enterprise Bankshares Inc.
Business Acquisition [Line Items]
Common stock, shares issued (in shares)	1,470,068
Total equity consideration	$ 22,727
Cash	32
Total consideration paid	22,759
Fair value of net assets assumed	17,595
Goodwill	$ 5,164