Loss And Loss Adjustment Expense Reserves (Schedule OF Losses And Loss Adjustment Expenses Reserves and Recoveries) (Detail) - USD ($) $ in Millions		Dec. 31, 2016	Dec. 31, 2015		Dec. 31, 2014
Loss And Lae Reserves [Member]
Loss And Loss Adjustment Expense Reserves [Line Items]
Loss and loss adjustment expense reserves		$ 541	$ 516		$ 506
Insurance Loss Recoverable [Member]
Loss And Loss Adjustment Expense Reserves [Line Items]
Insurance Loss Recoverable		504	577		$ 533
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		97	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]	294	406
Loss and loss adjustment expense reserves		44	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		14	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		280	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]	53	93
Loss and loss adjustment expense reserves		23	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		0	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		53	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		300	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		74	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		29	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		45	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		15	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		18	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		4
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		14	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		87	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		154	0
Loss and loss adjustment expense reserves		155	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		13	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		$ 13	$ 0

[1] (1) -As of December 31, 2016 and 2015, $280 million and $382 million were included in “Insurance loss recoverable” and $14 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 December 31, 2016 and 2015, $53 million and $87 million were eliminated from "Insurance loss recoverable”. As of December 31, 2015, $6 million was 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 December 31, 2016 and 2015, $45 million and $34 million were included in “Insurance loss recoverable” and $29 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 December 31, 2016 and 2015, $14 million and $8 million were eliminated from “Insurance loss recoverable.” As of December 31, 2016, $4 million was eliminated from “Loss and loss adjustment expense reserves” on the Company’s consolidated balance sheets.