Provision for Income Taxes (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Provision for Income Taxes
Income tax provision	$ 5.7	$ 2.6
Effective tax rates (as a percent)	36.30%	31.30%
Unrecognized tax benefits	34.2	32.7
Portion of unrecognized tax benefits, which if recognized, would result in a reduction of the effective tax rate	14.7	14.1
Accrued interest and penalties related to uncertain tax positions	4.0	3.8
Penalties and interest expense relating to unrecognized tax benefits	$ 0	$ 0.3