Income Taxes - Uncertain Tax Positions (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010
Income Tax Disclosure [Abstract]
Unrecognized tax benefits that would impact effective tax rate	$ 3.0
Interest related to unrecognized tax benefits	0.1
Cumulative interest accrued	0.7
Significant change in unrecognized tax benefits estimated range of change, lower bound	0
Significant change in unrecognized tax benefits estimated range of change, upper bound	4.0
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Unrecognized tax benefits beginning balance	8.2	19.5
Gross increases - tax positions in prior periods	1.0	0
Gross decreases - tax positions in prior periods	(0.1)	(8.3)
Gross increases (decreases) - tax positions in current period	0	(0.6)
Statute of limitation expirations	(1.6)	(2.4)
Unrecognized tax benefits ending balance	$ 7.7	$ 8.2