Income Taxes (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016
Income Taxes
Effective tax rate (as a percent)	31.40%	33.50%
Amount of unrecognized tax benefits	$ 16.3		$ 16.5
Decrease in unrecognized tax benefits	0.2
Gross accrued interest and penalties on unrecognized tax benefits	1.3		$ 1.8
Unrecognized income tax benefits that, if recognized, would affect the effective tax rates	16.8	$ 17.0
Unrecognized income tax benefits that, if recognized, would affect the effective tax rates , interest and penalties	0.9	$ 1.2
Significant changes to uncertain tax positions during the next twelve months	$ 0.0