Shareholders' Equity and Stock-Based Compensation (Details 4) (USD $) In Millions, except Share data in Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Stock option activity, Shares
Exercised (in shares)		(8)	(174)
Restricted stock shares and restricted stock units
Unvested Restricted Stock Shares and Restricted Stock Units
Outstanding at the beginning of the period (in shares)	1,537	1,935	1,440
Granted (in shares)	519	652	823
Vested (in shares)	(604)	(754)	(264)
Forfeited (in shares)	(284)	(296)	(64)
Outstanding at the end of the period (in shares)	1,168	1,537	1,935
Weighted-Average Grant-Date Fair Value
Outstanding at the beginning of the period (in dollars per share)	$ 58.39	$ 54.70	$ 54.38
Granted (in dollars per share)	$ 86.99	$ 61.66	$ 50.64
Vested (in dollars per share)	$ 59.49	$ 54.34	$ 39.75
Forfeited (in dollars per share)	$ 63.76	$ 52.20	$ 57.77
Outstanding at the end of the period (in dollars per share)	$ 69.22	$ 58.39	$ 54.70
Unrecognized compensation cost
Unrecognized compensation cost related to restricted stock share and restricted stock unit	$ 22.1
Weighted-average period over which unrecognized compensation costs will be recognized	1 year 8 months 12 days
Stock options
Stock option activity, Shares
Options outstanding and exercisable at the beginning of the period (in shares)		13	364
Exercised (in shares)		(8)	(174)
Terminated (in shares)		(5)	(177)
Options outstanding and exercisable at the end of the period (in shares)			13
Weighted-Average Exercise Price
Options outstanding and exercisable at the beginning of the period (in dollars per share)		$ 62.45	$ 54.87
Exercised (in dollars per share)		$ 50.79	$ 39.58
Terminated (in dollars per share)		$ 85.36	$ 69.42
Options outstanding and exercisable at the end of the period (in dollars per share)			$ 62.45
Stock option outstanding and exercisable
Aggregate intrinsic value of options exercised		$ 0.4	$ 5.9