Stock-based Compensation Stock-based Compensation (Details textual) (USD $) In Millions, except Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Share-based Compensation [Abstract]
Unrecognized stock-based compensation costs, net of estimated forfeitures	$ 50.7		$ 50.7
Weighted average period of unrecognized stock-based compensation costs, net of estimated forfeitures	2 years 1 month 6 days
Cash received from the exercise of stock options	18.0	0.6	28.1	1.7
Related tax benefit realized from the exercise of the stock options	$ 4.3	$ (0.3)	$ 7.0	$ 0.1
Time-vested restricted stock unit [Member]
Statement [Line Items]
Restricted stock units granted			665,000	1,088,000
Weighted average grant date fair value per share			$ 32.85	$ 23.43
Market-based restricted stock unit
Statement [Line Items]
Restricted stock units granted				7,000
Weighted average grant date fair value per share				$ 15.87
Employee Stock Purchase Plan [Member]
Statement [Line Items]
Number of common stock shares issued			85,000
Employee Stock
Statement [Line Items]
Weighted average grant date fair value per share	$ 7.87	$ 5.25	$ 7.87	$ 5.25
Shares of common stock reserved for future issuance under all of the stock incentive plans	3,545,000		3,545,000