Equity (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2019	Sep. 30, 2018	Aug. 31, 2019
Securities Repurchase Program
Repurchase of common stock	$ 43.6	$ 174.1	$ 55.8
Securities Repurchase Program
Securities Repurchase Program
Repurchased shares	1,021,622	3,871,887
Repurchase of common stock	$ 43.6	$ 169.2
Repurchased shares, average price (in dollars per share)	$ 42.66	$ 43.71
Amount authorized to be repurchased	$ 200.0	$ 200.0
Remaining amount authorized to be repurchased	$ 200.0	$ 200.0		$ 30.8
Acquired Employee Equity Awards
Securities Repurchase Program
Repurchased shares		114,949
Repurchase of common stock		$ 4.9
Repurchased shares, average price (in dollars per share)		$ 42.72