CONSOLIDATED STATEMENTS OF CHANGES IN STOCKHOLDERS' EQUITY (Parenthetical) - $ / shares	9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014
Statement Of Stockholders Equity [Abstract]
Common stock dividends, per share	$ 0.66	$ 0.56
Stock option plan, shares	35,039	13,834
Employee stock purchase plan, shares	19,377	18,404
Director stock purchase plan, shares	837
Restricted stock, shares	53,746	54,535
Treasury Stock, Shares, Acquired	728,932