Loss And Loss Adjustment Expense Reserves (Schedule Of Losses And Loss Adjustment Expenses) (Detail) (USD $) In Millions, unless otherwise specified	6 Months Ended
	Jun. 30, 2012
Loss And Loss Adjustment Expense Reserves [Line Items]
Losses and LAE related to actual and expected payments	$ 278
Recoveries of actual and expected payments	(119)
Gross losses incurred	159
Reinsurance
Losses and LAE	159
Second-Lien RMBS Reserves [Member]
Loss And Loss Adjustment Expense Reserves [Line Items]
Losses and LAE related to actual and expected payments	134
Recoveries of actual and expected payments	(67)
Gross losses incurred	67
Reinsurance
Losses and LAE	67
Other [Member]
Loss And Loss Adjustment Expense Reserves [Line Items]
Losses and LAE related to actual and expected payments	144
Recoveries of actual and expected payments	(52)
Gross losses incurred	92
Reinsurance
Losses and LAE	$ 92