Income Taxes - Allocation of Total Income Taxes (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Income Tax Disclosure [Abstract]
Income tax (benefit)/provision on (loss)/income before taxes	$ (870.5)	$ (534.7)	$ (492.5)
Discontinued operations	50.1	27.8	23.8
Accumulated other comprehensive income/(loss)	10.9	70.9	(10.5)
Retained earnings	0	6.0	0
Additional paid in capital	$ (2.1)	$ 11.6	$ 0