Shareholders' Equity (Details) (USD $) In Thousands, except Share data, unless otherwise specified	1 Months Ended		12 Months Ended
	Dec. 31, 2012	Oct. 31, 2011	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Shareholders' Equity [Abstract]
Number of shares authorized to be repurchased	4,000,000		4,000,000
Shares issued during the period			2,300,000	1,700,000	8,100,000
Common stock reissued			2,100,000	1,700,000	800,000
Issuance of common stock for acquisitions, Shares	100,000	200,000	200,000	0	1,000,000
Treasury Stock Acquired, Average Cost Per Share			$ 30.35	$ 28.12	$ 31.02
Treasury Stock, Shares, Acquired			400,000	1,700,000	3,000,000
Treasury Stock, Value, Acquired, Cost Method			$ 11,380	$ 48,505	$ 91,769
Class of Warrant or Right, Exercise Price of Warrants or Rights				16.00
Class of Warrant or Right, Number of Securities Called by Warrants or Rights				1,130,000
Class of Warrant or Right, Outstanding	0		0	34,328
Class of Warrant or Right, Exercisable Period				5 years