Loss And Loss Adjustment Expense Reserves (Schedule Of Financial Guarantees And Related Claim Liability) (Detail) $ in Millions		3 Months Ended	12 Months Ended
		Mar. 31, 2022 USD ($) issue policy	Dec. 31, 2021 USD ($) issue policy
Loss And Loss Adjustment Expense Reserves [Line Items]
Number of policies | policy		232	260
Number of issues | issue	[1]	105	106
Remaining weighted average contract period (in years)		7 years 7 months 6 days	7 years 4 months 24 days
Principal	[2]	$ 3,652	$ 4,091
Interest	[2]	2,879	3,082
Total	[2]	6,531	7,173
Gross claim liability	[3]	1,118	1,051
Less: Gross potential recoveries	[4]	421	1,498
Discount, net	[5]	187	(32)
Net claim liability (recoverable)		510	(415)
Unearned premium revenue		33	37
Reinsurance recoverable on paid and unpaid losses	[6]	$ 14	$ 7
Caution List Low [Member]
Loss And Loss Adjustment Expense Reserves [Line Items]
Number of policies | policy		55	55
Number of issues | issue	[1]	16	16
Remaining weighted average contract period (in years)		6 years	6 years 1 month 6 days
Principal	[2]	$ 1,325	$ 1,366
Interest	[2]	1,825	1,867
Total	[2]	3,150	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		$ 8	$ 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 3 months 18 days	2 years 7 months 6 days
Principal	[2]	$ 6	$ 6
Interest	[2]	1	1
Total	[2]	7	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
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		174	202
Number of issues | issue	[1]	87	88
Remaining weighted average contract period (in years)		8 years 6 months	8 years 1 month 6 days
Principal	[2]	$ 2,321	$ 2,719
Interest	[2]	1,053	1,214
Total	[2]	3,374	3,933
Gross claim liability	[3]	1,118	1,051
Less: Gross potential recoveries	[4]	421	1,498
Discount, net	[5]	187	(32)
Net claim liability (recoverable)		510	(415)
Unearned premium revenue		$ 25	$ 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.