Contingencies - Additional Information (Detail) (USD $) In Millions, except Share data, unless otherwise specified	9 Months Ended		3 Months Ended		9 Months Ended
	Sep. 30, 2012	Oct. 08, 2009	Sep. 30, 2012 Litigation Related To 2009 Exchange Offer [Member]	Jun. 30, 2012 Litigation Related To 2009 Exchange Offer [Member]	Sep. 30, 2012 Litigation Related To 2009 Exchange Offer [Member]	Sep. 30, 2012 Litigation Related To 2009 Exchange Offer [Member] Fidelity Settlement [Member]	Sep. 30, 2012 Litigation Related To 2009 Exchange Offer [Member] Other Shareholder Settlement [Member]	Sep. 30, 2012 Litigation Related To 2009 Exchange Offer [Member] Settlement With Remaining Class [Member]
Loss Contingencies [Line Items]
Preferred stock, shares issued	9,336,905	9,336,905
Percentage of outstanding common stock to be held by parent company after merger	100.00%
Purported class actions filed			4		4
Fidelity Controlled Shares						6,111,879
Number of Shares Exchanged in Exchange Offer						6,933,526	310,690
Remaining Shares Permit To Participate In Settlement						821,647
Final Settlement Amount						$ 22.5	$ 1.0	$ 9.2
Additional payments for settlement					4.2	4.0
Additional charge to the estimated costs of resolving the pending litigations			2.2	6.7	8.9
Amount not covered by insurance	$ 5				$ 5