Business Combinations - Narrative (Details)	12 Months Ended
	Dec. 31, 2017 USD ($) shares	Dec. 31, 2016 shares	Mar. 01, 2016 USD ($) shares
Business Acquisition [Line Items]
Common stock, shares issued (in shares) | shares	27,019,201	26,318,400
Reimbursement of losses with respect to converted assets percentage	80.00%
FDIC loss sharing period	10 years
Clawback consideration due to FDIC | $	$ 613,609
American Enterprise Bankshares Inc.
Business Acquisition [Line Items]
Goodwill | $			$ 5,164,000
Exchange of shares received by AEB shareholders			0.299
Common stock, shares issued (in shares) | shares			1,470,068