Stock based Compensation (Details Textuals) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Stock based Compensation [Abstract]
Stock-based compensation expense	$ 13,200,000	$ 12,400,000	$ 13,600,000
Total tax benefit recognized in earnings from stock-based compensation	4,600,000	4,400,000	4,800,000
Unrecognized compensation expense related to unvested options and restricted stock awards	24,800,000
Total unrecognized compensation cost recognized over a weighted-average period	3.0
Board Of Directors Fully Vested Stock Compensation	80,000
Chairman Of Board Fully Vested Common Stock Compensation	200,000
Aggregate intrinsic value of options exercised	10,200,000	5,900,000	8,700,000
Cash receipts from option exercises	60,000,000	39,800,000	29,900,000
Fair Value Of Rest Stock Awards Vested	10,900,000	1,100,000
Fair Value Of Rest Stock Units Vested	2,600,000
Tax benefit (charge) from stock options	$ 3,700,000	$ 2,100,000	$ 3,100,000
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant	1,700,000
Share Based Compensation Arrangement By Share Based Payment Award Number Of Shares Reserved For Issuance	3,600,000
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Authorized	5,300,000