CONDENSED CONSOLIDATED STATEMENTS OF CHANGES IN STOCKHOLDERS' EQUITY - (Parenthetical) - $ / shares	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Statement Of Stockholders Equity [Abstract]
Common stock dividends, per share	$ 0.82	$ 0.78
Stock option plan, shares	19,918	28,736
Employee stock purchase plan, shares	21,428	13,486
Restricted stock, shares	37,705	47,064
Number of shares issued by the company, pursuant to WashingtonFirst acquisition	11,446,197