Debt instrument maturity year.

No definition available.

Name:	mbi_DebtInstrumentMaturityYear
Namespace Prefix:	mbi_
Data Type:	xbrli:gYearItemType
Balance Type:	na
Period Type:	duration

- Definition

This element represents the liquidity position of the entity

+ References

No definition available.

+ Details

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

- Definition

This element represents disclosure of the aggregate cash dividends paid to the entity by consolidated subsidiaries.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 3
-Subparagraph (SX 210.12-04(b))
-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e24072-122690

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Contractual interest rate for funds borrowed, under the debt agreement.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22(a)(1))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Percentage price of original principal amount of debt at which debt can be redeemed by the issuer.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 470
-Section 50
-Paragraph 3
-Subparagraph e
-URI http://asc.fasb.org/extlink&oid=75038535&loc=d3e64711-112823

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Face (par) amount of the original debt instrument that was repurchased.

+ References

No definition available.

+ Details

Name:	us-gaap_DebtInstrumentRepurchasedFaceAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount of right to receive securities collateral under master netting arrangements that have not been offset against derivative liabilities.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 20
-Section 55
-Paragraph 13
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-URI http://asc.fasb.org/extlink&oid=51824906&loc=SL20225862-175312

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Fair value of financial instrument held by the entity for its own account (proprietary securities) for trading or investment purposes that are carried at fair value and pledged to counterparties as collateral for financing transactions.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 30
-Section 50
-Paragraph 1A
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-URI http://asc.fasb.org/extlink&oid=66007379&loc=d3e113888-111728

+ Details

Name:	us-gaap_SecurityOwnedAndPledgedAsCollateralFairValue
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Details

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- Details

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Namespace Prefix:
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- Details

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- Details

Name:	srt_ConsolidatedEntitiesAxis=mbi_NationalMember
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Schedule II - (Notes to Condensed Financial Statements) (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Long-term debt principal amount purchased		$ 44
Fair value of securities pledged as collateral	$ 313	314
Securities posted as collateral to derivative counterparties	$ 181	205
MBIA Inc. Senior Notes [Member]
Long-term debt, interest rate	5.70%
Long-term debt, maturity year	2034
Mbia Inc. Debentures [Member]
Long-term debt, interest rate	7.00%
Long-term debt, maturity year	2025
6.400% Senior Notes due 2022 [Member]
Long-term debt principal amount purchased	$ 150
Long-term debt principal amount purchased, par value	100.00%
Long-term debt, interest rate	6.40%
Long-term debt, maturity year	2022
National Public Finance Guarantee Holdings, Inc. [Member]
Dividends from subsidiaries		1	$ 118
MBIA Inc. [Member]
Liquid assets	$ 375
Fair value of securities pledged as collateral	313	314
Securities posted as collateral to derivative counterparties	181	205
National [Member]
Dividends from subsidiaries	134	108
National [Member] \| MBIA Inc. Senior Notes [Member]
Long-term debt principal amount purchased	44
National [Member] \| Mbia Inc. Debentures [Member]
Long-term debt principal amount purchased	10	$ 10
MBIA Capital Corp. [Member]
Dividends from subsidiaries	$ 3