Share-Based Payments Stock Options (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended		12 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Proceeds and Excess Tax Benefit from Share-based Compensation	$ 17.0	$ 6.1
Options and Sosars [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Outstanding at the beginning of the period (in shares)	1.5
Granted (in shares)	0.2
Exercised (in shares)	(0.1)
Forfeited (in shares)	0.0
Outstanding at the end of the period (in shares)	1.6
Share-based Compensation Arrangement by Share-based Payment Award, Options, Expected to Vest, Outstanding, Number	0.4
Exercisable (in shares)	1.2
Weighted-average exercise price of shares outstanding, beginning of the period (in dollars per share)	$ 59.79
Weighted-average exercise price of shares granted (in dollars per share)	96.77
Weighted-average exercise price of shares exercised (in dollars per share)	54.81
Weighted-average exercise price of shares forfeited (in dollars per share)	0.00
Weighted-average exercise price of shares outstanding, end of the period (in dollars per share)	63.88
Share-based Compensation Arrangement by Share-based Payment Award, Options, Expected to Vest, Outstanding, Weighted Average Exercise Price	89.67
Weighted-average exercise price of shares exercisable (in dollars per share)	$ 56.28
Weighted-average remaining contractual life, outstanding (in years)	5 years 10 months 24 days		5 years 4 months 24 days
Share-based Compensation Arrangement by Share-based Payment Award, Options, Expected to Vest, Outstanding, Weighted Average Remaining Contractual Term	9 years 2 months 12 days
Weighted-average remaining contractual life, exercisable (in years)	4 years 10 months 24 days
Aggregate intrinsic value of shares outstanding (in dollars)	$ 58.2
Aggregate intrinsic value of shares outstanding (in dollars)	51.4
Share-based Compensation Arrangement by Share-based Payment Award, Options, Expected to Vest, Outstanding, Aggregate Intrinsic Value	2.3
Aggregate intrinsic value of shares exercisable (in dollars)	$ 49.0