Acquisitions - Narrative (Details) - USD ($) $ in Thousands		12 Months Ended
	Apr. 01, 2019	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Business Acquisition [Line Items]
Merger related expenses		$ 11,782	$ 872	$ 0
HomeTown Bankshares Corporation Merger
Business Acquisition [Line Items]
Number of shares issued per share of common stock (in shares)	0.4150
Acquisition-related Costs [Member] | HomeTown Bankshares Corporation Merger
Business Acquisition [Line Items]
Merger related expenses		11,800
Data processing termination and conversion costs | HomeTown Bankshares Corporation Merger
Business Acquisition [Line Items]
Merger related expenses		9,100
Legal and Professional Fees | HomeTown Bankshares Corporation Merger
Business Acquisition [Line Items]
Merger related expenses		1,700
Salary and Related Expense | HomeTown Bankshares Corporation Merger
Business Acquisition [Line Items]
Merger related expenses		400
Other Noninterest Expense | HomeTown Bankshares Corporation Merger
Business Acquisition [Line Items]
Merger related expenses		$ 600