CONSOLIDATED STATEMENTS OF CHANGES IN STOCKHOLDERS' EQUITY (Parenthetical) - $ / shares	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Statement Of Stockholders Equity [Abstract]
Common stock dividends, per share	$ 0.24	$ 0.22
Stock option plan, shares	21,694	5,752
Employee stock purchase plan, shares	6,937	6,663
Restricted stock, shares	15,162	27,945
Treasury Stock, Shares, Retired	512,459	351,369