Mergers and Acquisitions - Schedule of Fair Value of Identifiable Assets Acquired and Liabilities Assumed (Details) - USD ($) $ in Thousands		9 Months Ended
	Apr. 01, 2017	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Consideration Paid:
Cash paid to shareholders		$ 608	$ 0
Fair value of liabilities assumed:
Goodwill resulting from merger with Middleburg		$ 167,409		$ 1,501
Middleburg Financial Corporation
Consideration Paid:
Common shares issued (9,516,097)	$ 285,679
Cash paid to shareholders	608
Value of consideration	286,287
Fair value of assets acquired:
Cash and cash equivalents	90,940
Investment securities	243,679
Restricted stock	4,119
Loans	815,817
Bank premises and equipment	22,516
OREO	3,949
Core deposit intangible	16,057
Bank owned life insurance	24,081
Other assets	24,572
Total assets	1,245,730
Fair value of liabilities assumed:
Deposits	1,056,619
Short-term borrowings	26,033
Long-term borrowings	29,892
Trust preferred debentures	3,824
Other liabilities	10,206
Total liabilities	1,126,574
Net assets acquired	119,156
Goodwill resulting from merger with Middleburg	$ 167,131
Corporation's common shares issued (in shares)	9,516,097