CONSOLIDATED STATEMENTS OF CHANGES IN SHAREHOLDERS' EQUITY (UNAUDITED) (Parenthetical) (USD $)	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Common stock, par value beginning balance	$ 0.001	$ 0.001
Conversion of common stock units, shares	8,293	10,834
Conversion of restricted stock units, shares	157,539	65,730
Cash dividends, per share	$ 0.25	$ 0.23
Treasury stock, beginning balance, shares	23,308,430	23,117,554
Treasury stock, acquisition of shares	23,500	136,976
Treasury stock, ending balance, shares	23,331,930	23,254,530
Options exercised, shares	43,298	196,840