Loss And Loss Adjustment Expense Reserves (Loss And LAE Activity) (Narrative) (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015	Dec. 31, 2015
Loss And Loss Adjustment Expense Reserves [Line Items]
Policyholder (Benefits) And Claims Incurred Net	$ 77	$ 46	$ 99	$ 40
Weighted average risk-free rate used to discount claim liability			1.18%
Insurance claim loss recoverable	363		$ 363		$ 571
Insurance loss recoverable	365		365		577
CDO Portfolio [Member]
Loss And Loss Adjustment Expense Reserves [Line Items]
Policyholder (Benefits) And Claims Incurred Net	9		(22)
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	8		20
Second Lien Residential Mortgage Backed Securities And Reserves [Member]
Loss And Loss Adjustment Expense Reserves [Line Items]
Policyholder (Benefits) And Claims Incurred Net	21	36	34	29
First Lien Residential Mortgage Backed Securities [Member]
Loss And Loss Adjustment Expense Reserves [Line Items]
Policyholder (Benefits) And Claims Incurred Net	35	(26)	61	(16)
Financial Guarantee [Member]
Loss And Loss Adjustment Expense Reserves [Line Items]
Aggregate CDO Loss And LAE Reserves	104		104		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	206		206		190
Loss And Lae Reserves [Member]
Loss And Loss Adjustment Expense Reserves [Line Items]
Reserves for expected future claim payments	637		637		616
Expected recoveries of future payments	91		91		100
Recoveries On Unpaid Losses [Member]
Loss And Loss Adjustment Expense Reserves [Line Items]
Expected recoveries of future payments	91		91		100
Insurance Loss Recoverable [Member]
Loss And Loss Adjustment Expense Reserves [Line Items]
Insurance loss recoverable	365		365		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	401		401		$ 396
Remedial Actions For Insured Obligations [Member]
Loss And Loss Adjustment Expense Reserves [Line Items]
Policyholder (Benefits) And Claims Incurred Net	$ 20	$ 7	$ 28	$ 5