CONSOLIDATED STATEMENTS OF CHANGES IN SHAREHOLDERS' EQUITY (Parenthetical) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Options exercised, shares	435,665	1,158,537	389,089
Conversion of common stock units, shares	10,834	11,851	15,084
Conversion of restricted stock units, shares	169,444	146,930	104,152
Cash dividends, per share	$ 0.92	$ 0.78	$ 0.55
Treasury stock, beginning balance, shares	23,117,554	22,943,925	22,028,030
Treasury stock, acquisition of shares	190,876	173,629	915,895
Treasury stock, ending balance, shares	23,308,430	23,117,554	22,943,925