Income Taxes (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Income Tax Disclosure [Abstract]
Effective tax rate (as a percent)	36.20%	38.00%	37.20%	37.90%
Federal statutory rate (as a percent)	35.00%	35.00%	35.00%	35.00%
Unrecognized tax benefits	$ 20.1		$ 20.1
Unrecognized tax benefits that would impact effective tax rate	15.0		15.0
Unrecognized Tax Benefits, Reduction Resulting from Lapse of Applicable Statute of Limitations	1.9
Maximum reduction in unrecognized tax benefits due to expiration of statutes of limitation and audit settlements in next 12 months	$ 4.8		$ 4.8