Income Taxes - Components of Income Tax (Expense) Benefit (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Income Tax Disclosure [Abstract]
Current Federal Tax (Expense) Benefit	$ 0	$ 0	$ 21.2
Current State and Local Tax (Expense) Benefit	(4.0)	(3.5)	2.3
Current Income Tax (Expense) Benefit	(4.0)	(3.5)	23.5
Deferred Federal Income Tax (Expense) Benefit	(0.9)	1.5	(14.9)
Deferred State and Local Income Tax (Expense) Benefit	0.2	(0.3)	3.1
Deferred Income Tax (Expense) Benefit	(0.7)	1.2	(11.8)
Federal Income Tax (Expense) Benefit, Continuing Operations	(0.9)	1.5	6.3
State and Local Income Tax (Expense) Benefit, Continuing Operations	(3.8)	(3.8)	5.4
Income tax (expense) benefit from continuing operations	$ (4.7)	$ (2.3)	$ 11.7