Income Taxes (Details) (USD $) In Millions, unless otherwise specified	6 Months Ended	12 Months Ended
	Jun. 30, 2013	Dec. 31, 2012
Unrecognized tax benefits
Decrease in income tax liability due to resolution of uncertain tax positions	$ 0.5
Reduction in deferred tax assets due to uncertain tax positions	0.2
Tax benefits	13.9	13.7
Accrued interest expense related to unrecognized tax benefits, gross of tax	$ 2.0	$ 1.9