Stock-Based Compensation (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares available for issuance under the 2011 Plan (in shares)	5,422,685		5,422,685
Stock options, granted (in shares)			607,228
Stock options, weighted average exercise price (in dollars per share)			$ 63.75
Stock options, weighted average grant date fair value (in dollars per share)			$ 12.35
Risk-free interest rate (in hundredths)			1.43%
Expected life (in years)			5 years 11 months
Stock volatility (in hundredths)			21.60%
Dividend yield (in hundredths)			1.00%
Share-based Compensation, Executive Retirements				$ 10.4
Stock-based compensation expense	$ 4.6	$ 3.6	$ 14.1	$ 24.4
Performance Vesting Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted (in shares)			114,029
Grant date fair value (in dollars per share)			$ 60.37
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%