Loss And Loss Adjustment Expense Reserves (Loss And LAE Activity) (Narrative) (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015	Dec. 31, 2015
Loss And Loss Adjustment Expense Reserves [Line Items]
Policyholder (Benefits) And Claims Incurred Net	$ 22	$ (6)
Weighted average risk-free rate used to discount claim liability	1.46%
Insurance claim loss recoverable	$ 407		$ 571
Insurance loss recoverable	409		577
CDO Portfolio [Member]
Loss And Loss Adjustment Expense Reserves [Line Items]
Policyholder (Benefits) And Claims Incurred Net	(31)
CDO Portfolio [Member] | Variable Interest Entity Primary Beneficiary [Member]
Loss And Loss Adjustment Expense Reserves [Line Items]
Elimination Of Loss And LAE Expense (Benefit) As Result Of Consolidating VIEs	13
Second Lien Residential Mortgage Backed Securities And Reserves [Member]
Loss And Loss Adjustment Expense Reserves [Line Items]
Policyholder (Benefits) And Claims Incurred Net	12	(8)
First Lien Residential Mortgage Backed Securities [Member]
Loss And Loss Adjustment Expense Reserves [Line Items]
Policyholder (Benefits) And Claims Incurred Net	26	9
Financial Guarantee [Member]
Loss And Loss Adjustment Expense Reserves [Line Items]
Aggregate CDO Loss And LAE Reserves	102		133
Financial Guarantee [Member] | CDO Portfolio [Member] | Variable Interest Entity Primary Beneficiary [Member]
Loss And Loss Adjustment Expense Reserves [Line Items]
Elimination Of Loss And Lae Reserves As Result Of Consolidating VIEs	199		190
Loss And Lae Reserves [Member]
Loss And Loss Adjustment Expense Reserves [Line Items]
Reserves for expected future claim payments	626		616
Expected recoveries of future payments	101		100
Recoveries On Unpaid Losses [Member]
Loss And Loss Adjustment Expense Reserves [Line Items]
Expected recoveries of future payments	101		100
Insurance Loss Recoverable [Member]
Loss And Loss Adjustment Expense Reserves [Line Items]
Insurance loss recoverable	409		577
Insurance Loss Recoverable [Member] | Classified [Member]
Loss And Loss Adjustment Expense Reserves [Line Items]
Insurance claim loss recoverable	407		571
Insurance loss recoverable	409		577
Loan Repurchase Commitments [Member] | Second Lien Residential Mortgage Backed Securities And Reserves [Member] | Ineligible Loan Recoveries [Member]
Loss And Loss Adjustment Expense Reserves [Line Items]
Total estimated insurance recoveries	399		$ 396
Remedial Actions For Insured Obligations [Member]
Loss And Loss Adjustment Expense Reserves [Line Items]
Policyholder (Benefits) And Claims Incurred Net	$ 8	$ (2)