Provision for Income Taxes (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014	Dec. 31, 2014
Provision for Income Taxes
Income tax provision	$ 2.3	$ 16.3	$ 7.1	$ 22.0
Effective tax rates (as a percent)	9.10%	49.20%	19.10%	45.10%
Unrecognized tax benefits, excluding penalties and interest	$ 30.3		$ 30.3		$ 27.0
Portion of unrecognized tax benefits, which if recognized, would result in a reduction of the effective tax rate	16.3		16.3		12.8
Accrued interest and penalties related to uncertain tax positions	4.7		4.7		$ 3.6
Penalties and interest expense relating to unrecognized tax benefits	$ 0.3	$ 0.0	$ 1.1	$ 0.0