Loss And Loss Adjustment Expense Reserves (Loss And LAE Activity) (Narrative) (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015	Dec. 31, 2015
Loss And Loss Adjustment Expense Reserves [Line Items]
Policyholder (Benefits) And Claims Incurred Net	$ 50	$ 39	$ 149	$ 79
Weighted average risk-free rate used to discount claim liability			1.31%
Addition to case basis reserves if losses remain at peak levels			$ 26
Reinsurance Receivables Case Basis	7		7		$ 6
Second Lien Residential Mortgage Backed Securities And Reserves [Member]
Loss And Loss Adjustment Expense Reserves [Line Items]
Policyholder (Benefits) And Claims Incurred Net	44	24	78	52
Lae [Member]
Loss And Loss Adjustment Expense Reserves [Line Items]
Policyholder (Benefits) And Claims Incurred Net	6	$ 5	34	$ 10
Insurance loss recoverable	1		1		6
Loss and loss adjustment expense reserves	54		54		$ 46
Ineligible Mortgage Loans [Member] | Second Lien Residential Mortgage Backed Securities And Reserves [Member]
Loss And Loss Adjustment Expense Reserves [Line Items]
Contract Claims On Ineligible Mortgage Loans Inception To Date Incurred Loss On Transactions	$ 432		$ 432