Provision for Income Taxes (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013	Dec. 31, 2013
Provision for Income Taxes
Income tax provision	$ 2.7	$ 9.9	$ 24.7	$ 24.9
Effective tax rates (as a percent)	30.00%	36.90%	42.70%	35.20%
Unrecognized tax benefits, excluding penalties and interest	31.7		31.7		32.7
Portion of unrecognized tax benefits, which if recognized, would result in a reduction of the effective tax rate	13.8		13.8		14.1
Accrued interest and penalties related to uncertain tax positions	3.9		3.9		3.8
Penalties and interest expense relating to unrecognized tax benefits	$ 0.2	$ 0.3	$ 0.2	$ (0.1)