Income Taxes (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Dec. 31, 2011
Unrecognized tax benefits
Uncertain income tax positions not recognized, if percentage is less than, likelihood of being sustained	50.00%
Decrease in income tax liability due to resolution of uncertain tax positions in the U.S.	$ 0.2
Decrease in deferred tax assets due to uncertain tax positions	0.1
Reconciliation of unrecognized tax benefits and interest related to unrecognized tax benefits
Unrecognized tax benefits	15.1	14.5
Accrued interest expense related to unrecognized tax benefits, gross of tax	$ 1.7	$ 1.6