Income Tax Uncertainties (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Dec. 31, 2012
Income Tax Uncertainties
Unrecognized tax benefits, including penalties and interest that if recognized would impact effective tax rate	$ 11.2	$ 10.8
Unrecognized tax benefits, including penalties and interest, net of federal tax benefit that if recognized would affect effective tax rate	7.7	7.5
Accrued interest and penalties related to uncertain tax positions	2.5	2.5
Accrued interest and penalties related to uncertain tax positions, net of federal benefit	2.0	2.0
Total expense of interest and penalties, net of federal benefit related to uncertain tax positions	$ 0.1