Acquisition of MainStreet BankShares, Inc. - Summary of Consideration Paid and Fair Value of Assets Acquired and Liabilities Assumed (Details) - USD ($) $ in Thousands		12 Months Ended
	Jan. 01, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Consideration Paid:
Cash paid to Shareholders		$ 0	$ 5,935	$ 0
Liabilities assumed:
Goodwill resulting from merger with MainStreet		43,872	43,872	$ 39,043
MainStreet BankShares, Inc.
Business Acquisition [Line Items]
Number of common stock shares issued in connection with merger (in shares)	825,586
Consideration Paid:
Common shares issued (825,586)			20,483
Cash paid to Shareholders			5,935
Value of consideration			26,418
Assets acquired:
Cash and cash equivalents			18,173
Investment securities			18,507
Restricted stock			587
Loans			115,960
Premises and equipment			956
Deferred income taxes			2,794
Core deposit intangible		$ 1,839	1,839
Other real estate owned			168
Bank owned life insurance			1,955
Accrued interest receivable and other assets			1,049
Total assets			161,988
Liabilities assumed:
Deposits			137,323
Accrued interest payable and other liabilities			3,076
Total liabilities			140,399
Net assets acquired			21,589
Goodwill resulting from merger with MainStreet	$ 5,300		4,829
Amounts Previously Recognized | MainStreet BankShares, Inc.
Consideration Paid:
Common shares issued (825,586)			20,483
Cash paid to Shareholders			5,935
Value of consideration			26,418
Assets acquired:
Cash and cash equivalents			18,173
Investment securities			18,507
Restricted stock			587
Loans			115,237
Premises and equipment			956
Deferred income taxes			3,056
Core deposit intangible			1,839
Other real estate owned			168
Bank owned life insurance			1,955
Accrued interest receivable and other assets			1,049
Total assets			161,527
Liabilities assumed:
Deposits			137,323
Accrued interest payable and other liabilities			3,076
Total liabilities			140,399
Net assets acquired			21,128
Goodwill resulting from merger with MainStreet			5,290
Measurement Period Adjustments | MainStreet BankShares, Inc.
Consideration Paid:
Common shares issued (825,586)			0
Cash paid to Shareholders			0
Value of consideration			0
Assets acquired:
Cash and cash equivalents			0
Investment securities			0
Restricted stock			0
Loans			(723)
Premises and equipment			0
Deferred income taxes			262
Core deposit intangible			0
Other real estate owned			0
Bank owned life insurance			0
Accrued interest receivable and other assets			0
Total assets			(461)
Liabilities assumed:
Deposits			0
Accrued interest payable and other liabilities			0
Total liabilities			0
Net assets acquired			$ (461)