Income Taxes (Summary of Income Tax Contingencies) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Unrecognized income tax benefits at January 1	$ 5.2	$ 6.1	$ 12.0
Decreases for positions taken in current year	0	0	(0.1)
Decreases for positions taken in a prior year	0	(0.8)	(1.3)
Decreases for settlements with taxing authorities	(2.3)	0	(3.6)
Decreases for lapses in the applicable statute of limitations	0	(0.1)	(0.9)
Unrecognized income tax benefits at December 31	$ 2.9	$ 5.2	$ 6.1