Equity (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Securities Repurchase Program
Repurchase of common stock	$ 173.6	$ 48.9	$ 15.5
Acquired Employee Equity Awards
Securities Repurchase Program
Repurchased shares	144,717	156,383	160,350
Repurchase of common stock	$ 5.7	$ 8.0	$ 7.5
Repurchased shares, average price (in dollars per share)	$ 39.47	$ 51.05	$ 46.48
Share Repurchase Program
Securities Repurchase Program
Repurchased shares	4,512,325	854,313	175,000
Repurchase of common stock	$ 167.9	$ 40.9	$ 8.0
Repurchased shares, average price (in dollars per share)	$ 37.21	$ 47.86	$ 45.95
Amount authorized to be repurchased	$ 32.1
Common Stock
Securities Repurchase Program
Repurchased shares	4,657,042	1,010,696	335,350