XML 49 R42.htm IDEA: XBRL DOCUMENT v3.25.1

Loss and Loss Adjustment Expense Reserves (Schedule of Insurance Loss Recoverable) (Detail) - Insurance Loss Recoverable [Member] $ in Millions	3 Months Ended
	Mar. 31, 2025 USD ($)
Roll forward of Insurance Loss Recoverable [Line Items]
Gross Reserve beginning balance, Insurance loss recoverable	$ 185
Collections for Cases	(2)
Accretion of Recoveries	2
Changes in Discount Rates	(1)
Changes in Assumptions	5
Gross Reserve ending balance, Insurance loss recoverable	$ 191

X

- Definition

Cash receipts related to recoveries of previously paid claims

+ References

No definition available.

+ Details

Name:	mbi_CollectionsForCases
Namespace Prefix:	mbi_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

X

- Definition

Carrying amount as of the balance sheet date of paid insurance policy claims and LAE expense expected to be recovered.

+ References

No definition available.

+ Details

Name:	mbi_InsuranceLossRecoverable
Namespace Prefix:	mbi_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

X

- Definition

Insurance Loss Recoverable And Changes In Recoveries Of Unpaid Losses Accretion Of Recoveries

+ References

No definition available.

+ Details

Name:	mbi_InsuranceLossRecoverableAndChangesInRecoveriesOfUnpaidLossesAccretionOfRecoveries
Namespace Prefix:	mbi_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

X

- Definition

Insurance Loss Recoverable And Changes In Recoveries Of Unpaid Losses Change In Assumptions

+ References

No definition available.

+ Details

Name:	mbi_InsuranceLossRecoverableAndChangesInRecoveriesOfUnpaidLossesChangeInAssumptions
Namespace Prefix:	mbi_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

X

- Definition

Insurance Loss Recoverable And Changes In Recoveries Of Unpaid Losses Change In Discount Rate

+ References

No definition available.

+ Details

Name:	mbi_InsuranceLossRecoverableAndChangesInRecoveriesOfUnpaidLossesChangeInDiscountRate
Namespace Prefix:	mbi_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

X

- Definition

Roll forward of Insurance Loss Recoverable [Line Items]

+ References

No definition available.

+ Details

Name:	mbi_RollForwardOfInsuranceLossRecoverableLineItems
Namespace Prefix:	mbi_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

X

- Details

Name:	mbi_ClaimLiabilityAxis=mbi_InsuranceLossRecoverableMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: