Consolidated Statements of Stockholders' Equity (Parenthetical) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016
Consolidated Statements Of Stockholders' Equity [Abstract]
Dividends declared per share	$ 0.14	$ 0.13
Common stock grants to directors, shares	5,156	5,934
Unearned compensation expense	$ 403	$ 234
Shares issued under employee stock purchase plan, shares	1,830
Treasury stock, shares, acquired	6,557
Purchased treasury stock, price per share	$ 14.80