Loss And Loss Adjustment Expense Reserves (Schedule Of Losses And Loss Adjustment Expenses) (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Loss And Loss Adjustment Expense Reserves [Line Items]
Policyholder Benefits And Claims Incurred Net	$ 46	$ 12	$ 40	$ 62
U S Public Finance Insurance [Member]
Loss And Loss Adjustment Expense Reserves [Line Items]
Policyholder Benefits And Claims Incurred Net	8	17	2	3
Second-Lien RMBS [Member]
Loss And Loss Adjustment Expense Reserves [Line Items]
Policyholder Benefits And Claims Incurred Net	36	47	29	72
First-Lien RMBS [Member]
Loss And Loss Adjustment Expense Reserves [Line Items]
Policyholder Benefits And Claims Incurred Net	(26)	(3)	(16)	27
Other [Member]
Loss And Loss Adjustment Expense Reserves [Line Items]
Policyholder Benefits And Claims Incurred Net	$ 28	$ (49)	$ 25	$ (40)