Loss And Loss Adjustment Expense Reserves (Schedule Of Losses And Loss Adjustment Expenses) (Detail) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Loss And Loss Adjustment Expense Reserves [Line Items]
Policyholder Benefits And Claims Incurred Net		$ 123	$ 133	$ 117
U S Public Finance Insurance [Member]
Loss And Loss Adjustment Expense Reserves [Line Items]
Policyholder Benefits And Claims Incurred Net		5	(10)	105
Second-Lien RMBS [Member]
Loss And Loss Adjustment Expense Reserves [Line Items]
Policyholder Benefits And Claims Incurred Net		63	70	(2)
First-Lien RMBS [Member]
Loss And Loss Adjustment Expense Reserves [Line Items]
Policyholder Benefits And Claims Incurred Net		34	65	(70)
Other [Member]
Loss And Loss Adjustment Expense Reserves [Line Items]
Policyholder Benefits And Claims Incurred Net	[1]	$ 21	$ 8	$ 84

[1] Includes CDOs, non-U.S. public finance and other issues.