Loss And Loss Adjustment Expense Reserves (Schedule Of Losses And Loss Adjustment Expenses) (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Loss And Loss Adjustment Expense Reserves [Line Items]
Policyholder Benefits And Claims Incurred Net	$ 39	$ 20	$ 79	$ 82
U S Public Finance Insurance [Member]
Loss And Loss Adjustment Expense Reserves [Line Items]
Policyholder Benefits And Claims Incurred Net	(7)	(8)	(5)	(5)
Second-Lien RMBS [Member]
Loss And Loss Adjustment Expense Reserves [Line Items]
Policyholder Benefits And Claims Incurred Net	24	16	52	88
First-Lien RMBS [Member]
Loss And Loss Adjustment Expense Reserves [Line Items]
Policyholder Benefits And Claims Incurred Net	18	12	2	39
Other [Member]
Loss And Loss Adjustment Expense Reserves [Line Items]
Policyholder Benefits And Claims Incurred Net	$ 4	$ 0	$ 30	$ (40)