Income Taxes - Reconciliation of Unrecognized Tax Benefits (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Unrecognized tax benefits, beginning balance	$ 15.1	$ 14.9	$ 13.8
Additions: Tax positions of current years	0.3	0.3	0.3
Additions: Tax positions of prior years	0.6	0.1	1.3
Reductions: Tax positions of prior years	(11.3)
Reductions: Settlements with taxing authorities	(0.2)	0	(0.2)
Reductions: Lapse of statute of limitations	(0.1)	(0.2)	(0.3)
Unrecognized tax benefits, ending balance	4.4	15.1	14.9
Unrecognized tax benefits that reduced income tax expenses but offset by increase of valuation allowance	10.5
Unrecognized tax benefits that would impact effective tax rate	4.4
Interest and penalties recorded (benefit) expense	(1.3)	(0.2)	0.5
Interest and penalties accrued	$ 0.3	$ 2.5	$ 2.6