Loss And Loss Adjustment Expense Reserves (Schedule Of Company's Second-Lien RMBS Exposure, Gross Undiscounted Claim Liability And Potential Recoveries, Before The Elimination Of Amounts Related To Consolidated VIE's) (Detail) (USD $) In Millions, unless otherwise specified	Jun. 30, 2014		Dec. 31, 2013
Loss And Loss Adjustment Expense Reserves [Line Items]
Outstanding Gross Principal	$ 15,595	[1]	$ 14,264	[1]
Gross Interest	9,273	[1]	8,632	[1]
Gross Undiscounted Claim Liability	984		1,235
Potential Recoveries	950		1,085
Insured Issues Designated As Classified List [Member] | Non Variable Interest Entities [Member]
Loss And Loss Adjustment Expense Reserves [Line Items]
Issues	24
Outstanding Gross Principal	3,200
Gross Interest	1,100
Gross Undiscounted Claim Liability	100
Potential Recoveries	600
Insured Issues Designated As Classified List [Member] | Variable Interest Entity Primary Beneficiary [Member]
Loss And Loss Adjustment Expense Reserves [Line Items]
Issues	11
Outstanding Gross Principal	1,600
Gross Interest	600
Gross Undiscounted Claim Liability	0
Potential Recoveries	$ 600

[1] Represents contractual principal and interest payments due by the issuer of the obligations insured by MBIA.