Loss And Loss Adjustment Expense Reserves (Schedule Of Losses And Loss Adjustment Expenses) (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2013
Loss And Loss Adjustment Expense Reserves [Line Items]
Losses and LAE related to actual and expected payments	$ 4
Recoveries of actual and expected payments	(198)
Gross losses incurred	(194)
Reinsurance
Losses and LAE	(194)
Second-Lien RMBS Reserves [Member]
Loss And Loss Adjustment Expense Reserves [Line Items]
Losses and LAE related to actual and expected payments	67
Recoveries of actual and expected payments	(220)
Gross losses incurred	(153)
Reinsurance
Losses and LAE	(153)
First-Lien RMBS Reserves [Member]
Loss And Loss Adjustment Expense Reserves [Line Items]
Losses and LAE related to actual and expected payments	(12)
Recoveries of actual and expected payments	(4)
Gross losses incurred	(16)
Reinsurance
Losses and LAE	(16)
Other [Member]
Loss And Loss Adjustment Expense Reserves [Line Items]
Losses and LAE related to actual and expected payments	(51)	[1]
Recoveries of actual and expected payments	26	[1]
Gross losses incurred	(25)	[1]
Reinsurance		[1]
Losses and LAE	$ (25)	[1]

[1] Primarily financial guarantee ABS CDOs.