Share-Based Payments Non-vested (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2014
Rsus and Dsus [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Non-vested awards outstanding at the beginning of the period (in shares)	0.7
Granted (in shares)	0.2
Vested (in shares)	(0.2)
Forfeited (in shares)	0
Non-vested awards outstanding at the end of the period (in shares)	0.7
Granted, weighted-average grant date fair value (in dollars per unit)	$ 70.10
Forfeited, weighted-average grant date fair value (in dollars per unit)	$ 0.00
Non-vested, weighted-average grant date fair value at the beginning of the period (in dollars per unit)	$ 47.75
Vested, weighted-average grant date fair value (in dollars per unit)	$ 43.18
Non-vested, weighted-average grant date fair value at the end of the period (in dollars per unit)	$ 53.81
PUs [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Non-vested awards outstanding at the beginning of the period (in shares)	0.5
Granted (in shares)	0
Vested (in shares)	(0.5)
Forfeited (in shares)	0
Non-vested awards outstanding at the end of the period (in shares)	0
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Intrinsic Value, Amount Per Share	$ 0.00		$ 3.22
Granted, weighted-average grant date fair value (in dollars per unit)	$ 0.00
Forfeited, weighted-average grant date fair value (in dollars per unit)	$ 0.00
Vested, weighted-average grant date fair value (in dollars per unit)	$ 2.89
PSUs [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Non-vested awards outstanding at the beginning of the period (in shares)	0.4
Granted (in shares)	0.1
Vested (in shares)	0
Forfeited (in shares)	0
Non-vested awards outstanding at the end of the period (in shares)	0.5
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Intrinsic Value, Amount Per Share	$ 62.47
Granted, weighted-average grant date fair value (in dollars per unit)	$ 74.42	$ 58.69
Forfeited, weighted-average grant date fair value (in dollars per unit)	$ 0.00
Non-vested, weighted-average grant date fair value at the beginning of the period (in dollars per unit)	$ 50.49
Vested, weighted-average grant date fair value (in dollars per unit)	$ 0.00
Non-vested, weighted-average grant date fair value at the end of the period (in dollars per unit)	$ 57.02