Loss And Loss Adjustment Expense Reserves (Loss And LAE Activity) (Narrative) (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016	Dec. 31, 2016
Loss And Loss Adjustment Expense Reserves [Line Items]
Policyholder (Benefits) And Claims Incurred Net	$ 170	$ 77	$ 264	$ 99
Weighted average risk-free rate used to discount claim liability	2.07%
Insurance loss recoverable	$ 483		483		$ 504
Loss and loss adjustment expense reserves	714		714		541
Reinsurance Receivables Case Basis	8		8		6
Second Lien Residential Mortgage Backed Securities And Reserves [Member]
Loss And Loss Adjustment Expense Reserves [Line Items]
Policyholder (Benefits) And Claims Incurred Net	(18)	21	4	34
Lae [Member]
Loss And Loss Adjustment Expense Reserves [Line Items]
Policyholder (Benefits) And Claims Incurred Net	15	$ 20	27	$ 28
Loss and loss adjustment expense reserves	72		72		$ 60
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	$ 437		$ 437