Equity (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Securities Repurchase Program
Repurchase of common stock	$ 174.1	$ 68.9	$ 18.5
Securities Repurchase Program
Securities Repurchase Program
Repurchased shares	3,871,887	1,467,886	302,000
Repurchase of common stock	$ 169.2	$ 63.1	$ 12.7
Repurchased shares, average price (in dollars per share)	$ 43.71	$ 43.00	$ 41.95
Amount authorized to be repurchased	$ 200.0
Acquired Employee Equity Awards
Securities Repurchase Program
Repurchased shares	114,949	119,608	133,710
Repurchase of common stock	$ 4.9	$ 5.8	$ 5.8
Repurchased shares, average price (in dollars per share)	$ 42.72	$ 48.61	$ 43.28