Other Income, net (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Other Income, net
Agency and commitment fees	$ (3.0)	$ (2.0)	$ (1.9)
Interest income	11.5	18.4	20.2
Other income, net	$ 8.5	$ 16.4	$ 18.3