Income Taxes - Allocation of Total Income Taxes (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Income Tax Expenses [Line Items]
Income tax benefit on loss before income taxes	$ 225.5	$ 77.7	$ 502.9	$ 271.2
Income tax expense on discontinued operations	(1.8)	(7.2)	(18.0)	(22.7)
Accumulated other comprehensive loss	(4.1)	14.2	(8.7)	14.0
Goodwill		(5.3)		(5.3)
Accumulated deficit				(6.0)
Additional paid-in capital	$ 2.1		$ 2.1