Equity (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Stock Repurchase Period
Repurchase of common stock	$ 48.9	$ 15.5	$ 15.8
Acquired Employee Equity Awards
Stock Repurchase Period
Repurchased shares	156,383	160,350	97,818
Repurchase of common stock	$ 8.0	$ 7.5	$ 3.1
Repurchased shares, average price (in dollars per share)	$ 51.05	$ 46.48	$ 32.13
Share Repurchase Program
Stock Repurchase Period
Repurchased shares	854,313	175,000	410,000
Repurchase of common stock	$ 40.9	$ 8.0	$ 12.7
Repurchased shares, average price (in dollars per share)	$ 47.86	$ 45.95	$ 30.93
Amount authorized to be repurchased	$ 200.0