Quarterly Results of Operations - Unaudited Quarterly Results of Operations (Parenthetical) (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended			3 Months Ended		12 Months Ended	3 Months Ended	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Sep. 30, 2012 Litigation Related to 2009 Exchange Offer [Member]	Jun. 30, 2012 Litigation Related to 2009 Exchange Offer [Member]	Dec. 31, 2012 Litigation Related to 2009 Exchange Offer [Member]	Sep. 30, 2012 2012 Restructuring Program [Member]	Dec. 31, 2012 2012 Restructuring Program [Member]
Quarterly Results Of Operations [Line Items]
Additional charge to the estimated costs of resolving the pending litigations				$ 2.2	$ 6.7	$ 8.9
Restructuring charges	20.7		(0.3)				24.1	24.1
Non cash benefit due to release of deferred tax valuation allowance	$ 15.8	$ 16.9	$ 260.6