Equity (Details 6) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Additional share based compensation information
Future Allocated Share-based Compensation Expense Next Twelve Months	$ 11.4
Future Allocated Share-based Compensation Expense Year Two	6.8
Future Allocated Share-based Compensation Expense Year Three	1.5
Unrecognized compensation expense on awards not expected to vest	46.9
Amortization of share based compensation	16.3	$ 27.9	$ 21.0
Employee Service Share-based Compensation, Tax Benefit from Compensation Expense	6.4	10.9	8.2
Excess tax benefits from share based compensation	4.7	5.6	6.1
Proceeds from issuance of common stock	5.3	$ 11.8	13.0
Additional paid-in capital
Additional share based compensation information
Unrecognized stock-based compensation expense	$ 66.6
Restricted shares with service and performance features
Shares
Non-vested at the end of the period (in shares)	0.2
Performance-based awards
Shares
Non-vested at the end of the period (in shares)	0.7
Restricted stock awards
Shares
Non-vested at the beginning of the period (in shares)	0.9
Granted (in shares)	0.5
Vested (in shares)	(0.4)
Forfeited (in shares)	(0.1)
Non-vested at the end of the period (in shares)	0.9	0.9
Weighted Average Grant Date Fair Value
Non-vested at the beginning of the period (in dollars per share)	$ 91.32
Granted (in dollars per share)	107.49
Vested (in dollars per share)	81.54
Forfeited (in dollars per share)	84.19
Non-vested at the end of the period (in dollars per share)	$ 104.76	$ 91.32
Additional share based compensation information
Grant date fair value of restricted stock awards vested	$ 30.2	$ 9.6	9.7
Additional paid-in capital
Additional share based compensation information
Amortization of share based compensation	$ 16.3	$ 27.9	$ 21.0