Income Taxes - Allocation of Total Income Taxes (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Income Tax Disclosure [Abstract]
Income tax benefit on loss before income taxes	$ (115.7)	$ (105.9)	$ (406.0)	$ (264.2)
Income tax (benefit)/provision on discontinued operations	0	(3.9)	(2.8)	3.0
Accumulated other comprehensive (income)/loss	$ (0.3)	$ 1.7	$ 1.2	$ 4.6