Income Taxes - Uncertain Tax Positions (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011
Income Tax Disclosure [Abstract]
Unrecognized tax benefits that would impact effective tax rate	$ 4.0
Interest related to unrecognized tax benefits	0.1
Cumulative interest accrued	0.8
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]
Balance as of January 1	7.7	8.2
Gross increases - tax positions in prior periods	1.5	1.0
Gross decreases - tax positions in prior periods	0	(0.1)
Gross increases - tax positions in current period	0	0.2
Statute of limitation expirations	0	(1.6)
Balance as of December 31	$ 9.4	$ 7.7