Loss And Loss Adjustment Expense Reserves (Schedule Of Financial Guarantees And Related Claim Liability) (Detail) $ in Millions		12 Months Ended
		Dec. 31, 2022 USD ($) issue policy		Dec. 31, 2021 USD ($) issue policy
Loss And Loss Adjustment Expense Reserves [Line Items]
Number of policies | policy		161		260
Number of issues | issue	[1]	99		106
Remaining weighted average contract period (in years)		6 years 4 months 24 days		7 years 4 months 24 days
Principal	[2]	$ 3,185		$ 4,091
Interest	[2]	2,508		3,082
Total	[2]	5,693		7,173
Gross claim liability	[3]	677		1,051
Less: Gross potential recoveries	[4]	198		1,498
Discount, net	[5]	179		(32)
Net claim liability (recoverable)		300		(415)
Unearned premium revenue		20		37
Reinsurance recoverable on paid and unpaid losses		$ 10	[6]	$ 7
Caution List Low [Member]
Loss And Loss Adjustment Expense Reserves [Line Items]
Number of policies | policy		57		55
Number of issues | issue	[1]	17		16
Remaining weighted average contract period (in years)		5 years 8 months 12 days		6 years 1 month 6 days
Principal	[2]	$ 1,723		$ 1,366
Interest	[2]	1,905		1,867
Total	[2]	3,628		3,233
Gross claim liability	[3]	0		0
Less: Gross potential recoveries	[4]	0		0
Discount, net	[5]	0		0
Net claim liability (recoverable)		0		0
Unearned premium revenue		$ 11		$ 8
Caution List Medium [Member]
Loss And Loss Adjustment Expense Reserves [Line Items]
Number of policies | policy		3		3
Number of issues | issue	[1]	2		2
Remaining weighted average contract period (in years)		2 years 4 months 24 days		2 years 7 months 6 days
Principal	[2]	$ 4		$ 6
Interest	[2]	1		1
Total	[2]	5		7
Gross claim liability	[3]	0		0
Less: Gross potential recoveries	[4]	0		0
Discount, net	[5]	0		0
Net claim liability (recoverable)		0		0
Unearned premium revenue		$ 0		$ 0
Caution List High [Member]
Loss And Loss Adjustment Expense Reserves [Line Items]
Number of policies | policy		0		0
Number of issues | issue	[1]	0		0
Remaining weighted average contract period (in years)		0 years		0 years
Principal	[2]	$ 0		$ 0
Interest	[2]	0		0
Total	[2]	0		0
Gross claim liability	[3]	0		0
Less: Gross potential recoveries	[4]	0		0
Discount, net	[5]	0		0
Net claim liability (recoverable)		0		0
Unearned premium revenue		$ 0		$ 0
Classified List [Member]
Loss And Loss Adjustment Expense Reserves [Line Items]
Number of policies | policy		101		202
Number of issues | issue	[1]	80		88
Remaining weighted average contract period (in years)		7 years 2 months 12 days		8 years 1 month 6 days
Principal	[2]	$ 1,458		$ 2,719
Interest	[2]	602		1,214
Total	[2]	2,060		3,933
Gross claim liability	[3]	677		1,051
Less: Gross potential recoveries	[4]	198		1,498
Discount, net	[5]	179		(32)
Net claim liability (recoverable)		300		(415)
Unearned premium revenue		$ 9		$ 29

[1] An “issue” represents the aggregate of financial guarantee policies that share the same revenue source for purposes of making debt service payments on the insured debt.

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

[3] The gross claim liability with respect to Puerto Rico exposures are net of expected recoveries for policies in a net payable position.

[4] Gross potential recoveries with respect to certain Puerto Rico exposures are net of the claim liability for policies in a net recoverable position.

[5] Represents discount related to Gross Claim Liability and Gross Potential Recoveries.

[6] Included in “Other assets” on the Company’s consolidated balance sheets.