Income Taxes (Details) (USD $) In Millions, unless otherwise specified	9 Months Ended
	Sep. 30, 2011	Dec. 31, 2010
Income Taxes
Percentage of likelihood of realization that the tax position must exceed in order for the amount to be recognized (as a percent)	50.00%
Decrease in income tax liability due to resolution of uncertain tax positions in the U.S.	$ 1.7
Decrease in deferred tax assets due to uncertain tax positions	0.3
Unrecognized tax benefits	13.6	12.4
Tax benefits	0.9
Accrued interest expense, net of tax, related to unrecognized tax benefits	$ 1.5	$ 1.2