Income Taxes - Components of Income Tax Expense (Details 5) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Current:
Federal	$ 0	$ 0	$ (1.2)
State	1.0	(2.1)	(1.8)
Foreign	1.9	1.8	1.8
Noncontrolling interests	17.6	(2.8)	(1.1)
Deferred:
Federal	31.5	(84.9)	(36.5)
State	2.8	(6.0)	(5.0)
Change in valuation allowance on beginning-of-the-year deferred tax assets	735.2	0	0
Total income tax provision (benefit)	790.0	(94.0)	(43.8)
Income tax provision due to tax law changes	0	2.0	25.3
Other Postretirement Benefit Plans, Defined Benefit [Member]
Deferred:
Income tax provision due to tax law changes	0	0	25.3
State and Local Jurisdiction [Member]
Deferred:
Income tax provision due to tax law changes	$ 0	$ 2.0	$ 0