Stock-Based Compensation (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015	May 03, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares available for issuance under the 2011 Plan (in shares)	5,441,195		5,441,195		5,500,000
Stock options, granted (in shares)			589,428
Stock options, weighted average exercise price (in dollars per share)			$ 61.55
Stock options, weighted average grant date fair value (in dollars per share)			$ 11.92
Risk-free interest rate (in hundredths)			1.39%
Expected life (in years)			5 years 11 months
Stock volatility (in hundredths)			21.00%
Dividend yield (in hundredths)			1.00%
Share-based Compensation, Executive Retirements	$ 10.4			$ 10.4
Stock-based compensation expense	$ 4.9	$ 15.5	$ 9.5	$ 20.8
Employee Stock Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Reduction in Number of Shares Available for Grant For Each Award Granted			1
Award Types Other than Stock Options and Stock Appreciation Rights [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Reduction in Number of Shares Available for Grant For Each Award Granted			2.5
Performance Vesting Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted (in shares)			110,595
Grant date fair value (in dollars per share)			$ 59.93
Number of shares of common stock per PVS award (in shares)	1		1
Performance period			3 years
PVS payout, Minimum (in hundredths)	0.00%		0.00%
PVS payout, Maximum (in hundredths)	200.00%		200.00%