Long-Term Equity Compensation (Weighted Average Grant Date Fair Value and Aggregate Intrinsic Value for RSU and PSU) (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period, Weighted Average Grant Date Fair Value	$ 29.68
Restricted Stock Units and Performance Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period, Weighted Average Grant Date Fair Value	$ 29.68	$ 29.43	$ 38.22
Aggregate intrinsic value of RSUs and PSUs vested	$ 30.5	$ 18.5	$ 49.0