Loss And Loss Adjustment Expense Reserves (Schedule OF Losses And Loss Adjustment Expenses Reserves and Recoveries) (Detail) - USD ($) $ in Millions		Sep. 30, 2016	Dec. 31, 2015
Loss And Lae Reserves [Member]
Loss And Loss Adjustment Expense Reserves [Line Items]
Loss and loss adjustment expense reserves		$ 513	$ 516
Insurance Loss Recoverable [Member]
Loss And Loss Adjustment Expense Reserves [Line Items]
Insurance Loss Recoverable		528	577
U S Public Finance Insurance [Member]
Loss And Loss Adjustment Expense Reserves [Line Items]
Insurance Loss Recoverable		174	4
Loss and loss adjustment expense reserves		72	45
International And Structured Finance Insurance [Member] | Second Lien Residential Mortgage Backed Securities And Reserves [Member]
Loss And Loss Adjustment Expense Reserves [Line Items]
Total excess spread recoveries	[1]	318	406
Loss and loss adjustment expense reserves		33	51
International And Structured Finance Insurance [Member] | Second Lien Residential Mortgage Backed Securities And Reserves [Member] | Excess Spread [Member] | Loss And Lae Reserves [Member]
Loss And Loss Adjustment Expense Reserves [Line Items]
Total excess spread recoveries		9	24
International And Structured Finance Insurance [Member] | Second Lien Residential Mortgage Backed Securities And Reserves [Member] | Excess Spread [Member] | Insurance Loss Recoverable [Member]
Loss And Loss Adjustment Expense Reserves [Line Items]
Total excess spread recoveries		309	382
International And Structured Finance Insurance [Member] | Second Lien Residential Mortgage Backed Securities And Reserves [Member] | Put-Back [Member]
Loss And Loss Adjustment Expense Reserves [Line Items]
Loan repurchase commitments		404	396
International And Structured Finance Insurance [Member] | Second Lien Residential Mortgage Backed Securities And Reserves [Member] | Variable Interest Entity Primary Beneficiary [Member]
Loss And Loss Adjustment Expense Reserves [Line Items]
Total excess spread recoveries	[2]	63	93
Loss and loss adjustment expense reserves		15	16
International And Structured Finance Insurance [Member] | Second Lien Residential Mortgage Backed Securities And Reserves [Member] | Variable Interest Entity Primary Beneficiary [Member] | Excess Spread [Member] | Loss And Lae Reserves [Member]
Loss And Loss Adjustment Expense Reserves [Line Items]
Total excess spread recoveries		1	6
International And Structured Finance Insurance [Member] | Second Lien Residential Mortgage Backed Securities And Reserves [Member] | Variable Interest Entity Primary Beneficiary [Member] | Excess Spread [Member] | Insurance Loss Recoverable [Member]
Loss And Loss Adjustment Expense Reserves [Line Items]
Total excess spread recoveries		62	87
International And Structured Finance Insurance [Member] | First Lien Rmbs [Member]
Loss And Loss Adjustment Expense Reserves [Line Items]
Loss and loss adjustment expense reserves		322	277
International And Structured Finance Insurance [Member] | First Lien Rmbs [Member] | Excess Spread [Member]
Loss And Loss Adjustment Expense Reserves [Line Items]
Total excess spread recoveries		77	80
International And Structured Finance Insurance [Member] | First Lien Rmbs [Member] | Excess Spread [Member] | Loss And Lae Reserves [Member]
Loss And Loss Adjustment Expense Reserves [Line Items]
Total excess spread recoveries		37	46
International And Structured Finance Insurance [Member] | First Lien Rmbs [Member] | Excess Spread [Member] | Insurance Loss Recoverable [Member]
Loss And Loss Adjustment Expense Reserves [Line Items]
Total excess spread recoveries		40	34
International And Structured Finance Insurance [Member] | First Lien Rmbs [Member] | Variable Interest Entity Primary Beneficiary [Member]
Loss And Loss Adjustment Expense Reserves [Line Items]
Loss and loss adjustment expense reserves		17	5
International And Structured Finance Insurance [Member] | First Lien Rmbs [Member] | Variable Interest Entity Primary Beneficiary [Member] | Excess Spread [Member]
Loss And Loss Adjustment Expense Reserves [Line Items]
Total excess spread recoveries		21	8
International And Structured Finance Insurance [Member] | First Lien Rmbs [Member] | Variable Interest Entity Primary Beneficiary [Member] | Excess Spread [Member] | Loss And Lae Reserves [Member]
Loss And Loss Adjustment Expense Reserves [Line Items]
Total excess spread recoveries		5
International And Structured Finance Insurance [Member] | First Lien Rmbs [Member] | Variable Interest Entity Primary Beneficiary [Member] | Excess Spread [Member] | Insurance Loss Recoverable [Member]
Loss And Loss Adjustment Expense Reserves [Line Items]
Total excess spread recoveries		16	8	[3],[4],[5]
International And Structured Finance Insurance [Member] | CDOs [Member]
Loss And Loss Adjustment Expense Reserves [Line Items]
Insurance Loss Recoverable		0	148
Loss and loss adjustment expense reserves		77	133
International And Structured Finance Insurance [Member] | CDOs [Member] | Variable Interest Entity Primary Beneficiary [Member]
Loss And Loss Adjustment Expense Reserves [Line Items]
Insurance Loss Recoverable		147	0
Loss and loss adjustment expense reserves		191	190
International And Structured Finance Insurance [Member] | All Other [Member]
Loss And Loss Adjustment Expense Reserves [Line Items]
Insurance Loss Recoverable		5	9
Loss and loss adjustment expense reserves		9	10
International And Structured Finance Insurance [Member] | All Other [Member] | Variable Interest Entity Primary Beneficiary [Member]
Loss And Loss Adjustment Expense Reserves [Line Items]
Insurance Loss Recoverable		0	0
Loss and loss adjustment expense reserves		$ 28	$ 0

[1] (1) -As of September 30, 2016 and December 31, 2015, $309 million and $382 million were included in “Insurance loss recoverable” and $9 million and $24 million were included in “Loss and loss adjustment expense reserves” on the Company’s consolidated balance sheets, respectively.

[2] (2) -As of September 30, 2016 and December 31, 2015, $62 million and $87 million were eliminated from "Insurance loss recoverable” and $1 million and $6 million were eliminated from “Loss and loss adjustment expense reserves” on the Company’s consolidated balance sheets, respectively.

[3] (3) - Reflected in “Loan repurchase commitments” presented under the heading “Assets of consolidated variable interest entities” on the Company’s consolidated balance sheets.

[4] (4) -As of September 30, 2016 and December 31, 2015, $40 million and $34 million were included in “Insurance loss recoverable” and $37 million and $46 million were included in “Loss and loss adjustment expense reserves” on the Company’s consolidated balance sheets, respectively.

[5] (5) -As of September 30, 2016 and December 31, 2015, $16 million and $8 million were eliminated from “Insurance loss recoverable.” As of September 30, 2016, $5 million was eliminated from “Loss and loss adjustment expense reserves” on the Company’s consolidated balance sheets.