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]
Balance at Beginning of Year	$ 6.2	$ 7.8	$ 11.7
Reductions for Tax Positions of Current Period	0	(1.8)	(1.7)
Additions for Tax Positions of Prior Years	0.2	0.2	26.6
Reduction for Expiration of Federal Statute of Limitations	0	0	(28.8)
Balance at End of Year	6.4	6.2	7.8
Unrecognized Tax Benefit that Would Not Impact Effective Tax Rate, Tax Position with Uncertain Timing of Deductibility	3.5	3.7	5.7
Unrecognized Tax Benefits, Interest on Income Taxes Accrued	2.9	2.5	2.1
Unrecognized Tax Benefits, Interest Expense (Benefits) Net on Income Taxes			2.1
Unrecognized Tax Benefits, Interest on Income Taxes Expense	0.4	(0.4)	(0.7)
Expiration From All Other Years Including 2006 [Member]
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Unrecognized Tax Benefits, Interest Benefit on Income Taxes			$ 2.8