XML 72 R56.htm IDEA: XBRL DOCUMENT
v3.20.2

Fair Value Measurements - Summary of Carrying Amount and Fair Value of Ambac's Financial Assets and Liabilities (Details) - USD ($) $ in Millions | Sep. 30, 2020 | Dec. 31, 2019
--- | --- | ---
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items] |  |
Fixed income securities, at fair value | $ 3,048 |
Financial assets: |  |
Derivative assets | 95 | $ 75
Other assets | 2 | 3
Long-term Debt | 2,737 | 2,822
Financial liabilities: |  |
Derivative liabilities | 126 | 90
Short-term Investments [Member] |  |
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items] |  |
Fixed income securities, at fair value | 586 | 653
Total Fair Value [Member] |  |
Financial assets: |  |
Cash | 48 | 79
Reported Value Measurement [Member] |  |
Financial assets: |  |
Other investments | 60 | 136
Cash | 48 | 79
Loans | 3 | 10
Other assets | 2 | 3
Total financial assets | 9,696 | 10,242
Financial liabilities: |  |
Liabilities for net financial guarantees written | (744) | (863)
Long-term debt | 3,236 | 3,262
Total financial liabilities | 8,558 | 8,699
Reported Value Measurement [Member] | Short-term Investments [Member] |  |
Financial assets: |  |
Short term investments | 586 | 653
Reported Value Measurement [Member] | Other Debt Obligations [Member] |  |
Financial assets: |  |
Other investments | 502 | 478
Reported Value Measurement [Member] | Interest Rate Swap [Member] |  |
Financial liabilities: |  |
Derivative liabilities | 125 | 89
Reported Value Measurement [Member] | Other Credit Derivatives [Member] |  |
Financial liabilities: |  |
Derivative liabilities | 1 |
Other Assets [Member] | Reported Value Measurement [Member] | Interest Rate Swap [Member] |  |
Financial assets: |  |
Derivative assets | 95 | 75
Level 1 [Member] |  |
Financial assets: |  |
Cash | 39 | 70
Total financial assets | 965 | 1,091
Financial liabilities: |  |
Liabilities for net financial guarantees written | 0 | 0
Long-term debt | 0 | 0
Total financial liabilities | 0 | 0
Level 1 [Member] | Short-term Investments [Member] |  |
Financial assets: |  |
Short term investments | 509 | 598
Level 1 [Member] | Equity Method Investments [Member] |  |
Financial assets: |  |
Other assets | 0 | 0
Level 1 [Member] | Loans Receivable [Member] |  |
Financial assets: |  |
Loans | 0 | 0
Level 1 [Member] | Other Debt Obligations [Member] |  |
Financial assets: |  |
Other investments | 62 | 136
Level 1 [Member] | Interest Rate Swap [Member] |  |
Financial liabilities: |  |
Derivative liabilities | 0 | 0
Level 1 [Member] | Other Credit Derivatives [Member] |  |
Financial liabilities: |  |
Derivative liabilities | 0 |
Level 1 [Member] | Other Assets [Member] | Interest Rate Swap [Member] |  |
Financial assets: |  |
Derivative assets | 0 | 0
Level 2 [Member] |  |
Financial assets: |  |
Cash | 9 | 9
Total financial assets | 2,312 | 2,593
Financial liabilities: |  |
Liabilities for net financial guarantees written | 0 | 0
Long-term debt | 2,679 | 2,829
Total financial liabilities | 8,601 | 8,983
Level 2 [Member] | Short-term Investments [Member] |  |
Financial assets: |  |
Short term investments | 77 | 55
Level 2 [Member] | Equity Method Investments [Member] |  |
Financial assets: |  |
Other assets | 0 | 0
Level 2 [Member] | Loans Receivable [Member] |  |
Financial assets: |  |
Loans | 0 | 0
Level 2 [Member] | Other Debt Obligations [Member] |  |
Financial assets: |  |
Other investments | 0 | 0
Level 2 [Member] | Interest Rate Swap [Member] |  |
Financial liabilities: |  |
Derivative liabilities | 125 | 89
Level 2 [Member] | Other Credit Derivatives [Member] |  |
Financial liabilities: |  |
Derivative liabilities | 0 |
Level 2 [Member] | Other Assets [Member] | Interest Rate Swap [Member] |  |
Financial assets: |  |
Derivative assets | 9 | 8
Level 3 [Member] |  |
Financial assets: |  |
Cash | 0 | 0
Total financial assets | 6,013 | 6,281
Financial liabilities: |  |
Liabilities for net financial guarantees written | 436 | 284
Long-term debt | 377 | 445
Total financial liabilities | 968 | 889
Level 3 [Member] | Short-term Investments [Member] |  |
Financial assets: |  |
Short term investments | 0 | 0
Level 3 [Member] | Equity Method Investments [Member] |  |
Financial assets: |  |
Other assets | 2 | 3
Level 3 [Member] | Loans Receivable [Member] |  |
Financial assets: |  |
Loans | 3 | 13
Level 3 [Member] | Other Debt Obligations [Member] |  |
Financial assets: |  |
Other investments | 35 | 61
Level 3 [Member] | Interest Rate Swap [Member] |  |
Financial liabilities: |  |
Derivative liabilities | 0 | 0
Level 3 [Member] | Other Credit Derivatives [Member] |  |
Financial liabilities: |  |
Derivative liabilities | 1 |
Level 3 [Member] | Other Assets [Member] | Interest Rate Swap [Member] |  |
Financial assets: |  |
Derivative assets | 86 | 67
Commercial Mortgage Backed Securities [Member] | Reported Value Measurement [Member] |  |
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items] |  |
Fixed income securities, at fair value |  | 50
Municipal Bonds [Member] | Reported Value Measurement [Member] |  |
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items] |  |
Fixed income securities, at fair value | 351 | 215
Corporate Debt Securities [Member] | Reported Value Measurement [Member] |  |
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items] |  |
Fixed income securities, at fair value | 1,091 | 1,430
Debt Security, Government, Non-US [Member] | Reported Value Measurement [Member] |  |
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items] |  |
Fixed income securities, at fair value | 77 | 44
US Government Debt Securities [Member] | Reported Value Measurement [Member] |  |
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items] |  |
Fixed income securities, at fair value | 122 | 156
Residential Mortgage-Backed Securities [Member] | Reported Value Measurement [Member] |  |
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items] |  |
Fixed income securities, at fair value | 296 | 248
Collateralized Debt Obligations [Member] | Reported Value Measurement [Member] |  |
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items] |  |
Fixed income securities, at fair value | 73 | 146
Asset-backed Securities [Member] | Reported Value Measurement [Member] |  |
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items] |  |
Fixed income securities, at fair value | 300 | 287
Fair Value, Recurring [Member] |  |
Financial assets: |  |
Total financial assets | 9,682 | 10,260
Financial liabilities: |  |
Liabilities for net financial guarantees written | 436 | 284
Long-term debt | 3,056 | 3,274
Total financial liabilities | 9,569 | 9,872
Fair Value, Recurring [Member] | Commercial Mortgage Backed Securities [Member] |  |
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items] |  |
Fixed income securities, at fair value |  | 50
Fair Value, Recurring [Member] | Short-term Investments [Member] |  |
Financial assets: |  |
Short term investments | 586 | 653
Fair Value, Recurring [Member] | Equity Method Investments [Member] |  |
Financial assets: |  |
Other assets | 2 | 3
Fair Value, Recurring [Member] | Loans Receivable [Member] |  |
Financial assets: |  |
Loans | 3 | 13
Fair Value, Recurring [Member] | Other Debt Obligations [Member] |  |
Financial assets: |  |
Other investments | 488 | 493
Fair Value, Recurring [Member] | Asset-backed Securities [Member] |  |
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items] |  |
Fixed income securities, at fair value | 300 | 287
Fair Value, Recurring [Member] | Collateralized Debt Obligations [Member] |  |
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items] |  |
Fixed income securities, at fair value | 73 | 146
Fair Value, Recurring [Member] | Residential Mortgage-Backed Securities [Member] |  |
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items] |  |
Fixed income securities, at fair value | 296 | 248
Fair Value, Recurring [Member] | US Government Debt Securities [Member] |  |
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items] |  |
Fixed income securities, at fair value | 122 | 156
Fair Value, Recurring [Member] | Debt Security, Government, Non-US [Member] |  |
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items] |  |
Fixed income securities, at fair value | 77 | 44
Fair Value, Recurring [Member] | Corporate Debt Securities [Member] |  |
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items] |  |
Fixed income securities, at fair value | 1,091 | 1,430
Fair Value, Recurring [Member] | Municipal Bonds [Member] |  |
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items] |  |
Fixed income securities, at fair value | 351 | 215
Fair Value, Recurring [Member] | Interest Rate Swap [Member] |  |
Financial liabilities: |  |
Derivative liabilities | 125 | 89
Fair Value, Recurring [Member] | Other Credit Derivatives [Member] |  |
Financial liabilities: |  |
Derivative liabilities | 1 |
Fair Value, Recurring [Member] | Other Assets [Member] | Interest Rate Swap [Member] |  |
Financial assets: |  |
Derivative assets | 95 | 75
Fair Value, Recurring [Member] | Level 1 [Member] | Commercial Mortgage Backed Securities [Member] |  |
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items] |  |
Fixed income securities, at fair value |  | 0
Fair Value, Recurring [Member] | Level 1 [Member] | Asset-backed Securities [Member] |  |
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items] |  |
Fixed income securities, at fair value | 0 | 0
Fair Value, Recurring [Member] | Level 1 [Member] | Collateralized Debt Obligations [Member] |  |
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items] |  |
Fixed income securities, at fair value | 0 | 0
Fair Value, Recurring [Member] | Level 1 [Member] | Residential Mortgage-Backed Securities [Member] |  |
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items] |  |
Fixed income securities, at fair value | 0 | 0
Fair Value, Recurring [Member] | Level 1 [Member] | US Government Debt Securities [Member] |  |
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items] |  |
Fixed income securities, at fair value | 122 | 156
Fair Value, Recurring [Member] | Level 1 [Member] | Debt Security, Government, Non-US [Member] |  |
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items] |  |
Fixed income securities, at fair value | 77 | 44
Fair Value, Recurring [Member] | Level 1 [Member] | Corporate Debt Securities [Member] |  |
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items] |  |
Fixed income securities, at fair value | 2 | 0
Fair Value, Recurring [Member] | Level 1 [Member] | Municipal Bonds [Member] |  |
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items] |  |
Fixed income securities, at fair value | 0 | 0
Fair Value, Recurring [Member] | Level 2 [Member] | Commercial Mortgage Backed Securities [Member] |  |
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items] |  |
Fixed income securities, at fair value |  | 50
Fair Value, Recurring [Member] | Level 2 [Member] | Asset-backed Securities [Member] |  |
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items] |  |
Fixed income securities, at fair value | 225 | 215
Fair Value, Recurring [Member] | Level 2 [Member] | Collateralized Debt Obligations [Member] |  |
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items] |  |
Fixed income securities, at fair value | 73 | 146
Fair Value, Recurring [Member] | Level 2 [Member] | Residential Mortgage-Backed Securities [Member] |  |
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items] |  |
Fixed income securities, at fair value | 296 | 248
Fair Value, Recurring [Member] | Level 2 [Member] | US Government Debt Securities [Member] |  |
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items] |  |
Fixed income securities, at fair value | 0 | 0
Fair Value, Recurring [Member] | Level 2 [Member] | Debt Security, Government, Non-US [Member] |  |
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items] |  |
Fixed income securities, at fair value | 0 | 0
Fair Value, Recurring [Member] | Level 2 [Member] | Corporate Debt Securities [Member] |  |
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items] |  |
Fixed income securities, at fair value | 1,089 | 1,430
Fair Value, Recurring [Member] | Level 2 [Member] | Municipal Bonds [Member] |  |
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items] |  |
Fixed income securities, at fair value | 351 | 215
Fair Value, Recurring [Member] | Level 3 [Member] | Commercial Mortgage Backed Securities [Member] |  |
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items] |  |
Fixed income securities, at fair value |  | 0
Fair Value, Recurring [Member] | Level 3 [Member] | Asset-backed Securities [Member] |  |
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items] |  |
Fixed income securities, at fair value | 75 | 72
Fair Value, Recurring [Member] | Level 3 [Member] | Collateralized Debt Obligations [Member] |  |
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items] |  |
Fixed income securities, at fair value | 0 | 0
Fair Value, Recurring [Member] | Level 3 [Member] | Residential Mortgage-Backed Securities [Member] |  |
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items] |  |
Fixed income securities, at fair value | 0 | 0
Fair Value, Recurring [Member] | Level 3 [Member] | US Government Debt Securities [Member] |  |
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items] |  |
Fixed income securities, at fair value | 0 | 0
Fair Value, Recurring [Member] | Level 3 [Member] | Debt Security, Government, Non-US [Member] |  |
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items] |  |
Fixed income securities, at fair value | 0 | 0
Fair Value, Recurring [Member] | Level 3 [Member] | Corporate Debt Securities [Member] |  |
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items] |  |
Fixed income securities, at fair value | 0 | 0
Fair Value, Recurring [Member] | Level 3 [Member] | Municipal Bonds [Member] |  |
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items] |  |
Fixed income securities, at fair value | 0 | 0
Collateral Pledged [Member] | Short-term Investments [Member] |  |
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items] |  |
Fixed income securities, at fair value |  | 85
Collateral Pledged [Member] | Short-term Investments [Member] | Reported Value Measurement [Member] |  |
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items] |  |
Fixed income securities, at fair value | 152 | 85
Collateral Pledged [Member] | Fair Value, Recurring [Member] | Short-term Investments [Member] |  |
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items] |  |
Fixed income securities, at fair value | 152 | 85
Collateral Pledged [Member] | Fair Value, Recurring [Member] | Level 1 [Member] | Short-term Investments [Member] |  |
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items] |  |
Fixed income securities, at fair value | 152 | 85
Collateral Pledged [Member] | Fair Value, Recurring [Member] | Level 2 [Member] | Short-term Investments [Member] |  |
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items] |  |
Fixed income securities, at fair value | 0 | 0
Collateral Pledged [Member] | Fair Value, Recurring [Member] | Level 3 [Member] | Short-term Investments [Member] |  |
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items] |  |
Fixed income securities, at fair value | 0 | 0
Variable Interest Entity, Primary Beneficiary [Member] |  |
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items] |  |
Fixed income securities, at fair value | 3,160 | 3,121
Financial assets: |  |
Loans | 2,783 | 3,108
Derivative assets | 53 | 52
Long-term Debt | 4,169 | 4,554
Financial liabilities: |  |
Derivative liabilities | 1,771 | 1,657
Long-term debt | 4,002 | 4,351
Variable Interest Entity, Primary Beneficiary [Member] | Corporate Debt Securities [Member] |  |
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items] |  |
Fixed income securities, at fair value | 3,029 | 2,957
Variable Interest Entity, Primary Beneficiary [Member] | Municipal Bonds [Member] |  |
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items] |  |
Fixed income securities, at fair value | 131 | 164
Variable Interest Entity, Primary Beneficiary [Member] | Reported Value Measurement [Member] |  |
Financial assets: |  |
Restricted Cash and Cash Equivalents, Current | 2 | 2
Loans | 2,783 | 3,108
Financial liabilities: |  |
Long-term debt | 4,169 | 4,554
Variable Interest Entity, Primary Beneficiary [Member] | Reported Value Measurement [Member] | Corporate Debt Securities [Member] |  |
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items] |  |
Fixed income securities, at fair value | 3,029 | 2,957
Variable Interest Entity, Primary Beneficiary [Member] | Reported Value Measurement [Member] | Municipal Bonds [Member] |  |
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items] |  |
Fixed income securities, at fair value | 131 | 164
Variable Interest Entity, Primary Beneficiary [Member] | Reported Value Measurement [Member] | Interest Rate Swap [Member] |  |
Financial liabilities: |  |
Derivative liabilities | 1,771 | 1,657
Variable Interest Entity, Primary Beneficiary [Member] | Reported Value Measurement [Member] | Currency Swaps [Member] |  |
Financial assets: |  |
Derivative assets | 53 | 52
Variable Interest Entity, Primary Beneficiary [Member] | Level 1 [Member] |  |
Financial assets: |  |
Restricted Cash and Cash Equivalents, Current | 2 | 2
Loans | 0 | 0
Financial liabilities: |  |
Long-term debt | 0 | 0
Variable Interest Entity, Primary Beneficiary [Member] | Level 1 [Member] | Corporate Debt Securities [Member] |  |
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items] |  |
Fixed income securities, at fair value | 0 | 0
Variable Interest Entity, Primary Beneficiary [Member] | Level 1 [Member] | Municipal Bonds [Member] |  |
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items] |  |
Fixed income securities, at fair value | 0 | 0
Variable Interest Entity, Primary Beneficiary [Member] | Level 1 [Member] | Interest Rate Swap [Member] |  |
Financial liabilities: |  |
Derivative liabilities | 0 | 0
Variable Interest Entity, Primary Beneficiary [Member] | Level 1 [Member] | Currency Swaps [Member] |  |
Financial assets: |  |
Derivative assets | 0 | 0
Variable Interest Entity, Primary Beneficiary [Member] | Level 2 [Member] |  |
Financial assets: |  |
Restricted Cash and Cash Equivalents, Current | 0 | 0
Loans | 0 | 0
Financial liabilities: |  |
Long-term debt | 4,026 | 4,408
Variable Interest Entity, Primary Beneficiary [Member] | Level 2 [Member] | Corporate Debt Securities [Member] |  |
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items] |  |
Fixed income securities, at fair value | 0 | 0
Variable Interest Entity, Primary Beneficiary [Member] | Level 2 [Member] | Municipal Bonds [Member] |  |
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items] |  |
Fixed income securities, at fair value | 131 | 164
Variable Interest Entity, Primary Beneficiary [Member] | Level 2 [Member] | Interest Rate Swap [Member] |  |
Financial liabilities: |  |
Derivative liabilities | 1,771 | 1,657
Variable Interest Entity, Primary Beneficiary [Member] | Level 2 [Member] | Currency Swaps [Member] |  |
Financial assets: |  |
Derivative assets | 53 | 52
Variable Interest Entity, Primary Beneficiary [Member] | Level 3 [Member] |  |
Financial assets: |  |
Restricted Cash and Cash Equivalents, Current | 0 | 0
Loans | 2,783 | 3,108
Financial liabilities: |  |
Long-term debt | 153 | 159
Variable Interest Entity, Primary Beneficiary [Member] | Level 3 [Member] | Corporate Debt Securities [Member] |  |
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items] |  |
Fixed income securities, at fair value | 3,029 | 2,957
Variable Interest Entity, Primary Beneficiary [Member] | Level 3 [Member] | Municipal Bonds [Member] |  |
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items] |  |
Fixed income securities, at fair value | 0 | 0
Variable Interest Entity, Primary Beneficiary [Member] | Level 3 [Member] | Interest Rate Swap [Member] |  |
Financial liabilities: |  |
Derivative liabilities | 0 | 0
Variable Interest Entity, Primary Beneficiary [Member] | Level 3 [Member] | Currency Swaps [Member] |  |
Financial assets: |  |
Derivative assets | 0 | 0
Variable Interest Entity, Primary Beneficiary [Member] | Fair Value, Recurring [Member] |  |
Financial assets: |  |
Restricted Cash and Cash Equivalents, Current | 2 | 2
Loans | 2,783 | 3,108
Financial liabilities: |  |
Long-term debt | 4,179 | 4,567
Variable Interest Entity, Primary Beneficiary [Member] | Fair Value, Recurring [Member] | Corporate Debt Securities [Member] |  |
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items] |  |
Fixed income securities, at fair value | 3,029 | 2,957
Variable Interest Entity, Primary Beneficiary [Member] | Fair Value, Recurring [Member] | Municipal Bonds [Member] |  |
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items] |  |
Fixed income securities, at fair value | 131 | 164
Variable Interest Entity, Primary Beneficiary [Member] | Fair Value, Recurring [Member] | Interest Rate Swap [Member] |  |
Financial liabilities: |  |
Derivative liabilities | 1,771 | 1,657
Variable Interest Entity, Primary Beneficiary [Member] | Fair Value, Recurring [Member] | Currency Swaps [Member] |  |
Financial assets: |  |
Derivative assets | $ 53 | $ 52

X
- Definition Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items] + References No definition available. + Details
Name: | ambc_FairValueOfAssetsAndLiabilitiesMeasuredOnNonRecurringBasisLineItems
Namespace Prefix: | ambc_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Fair value portion of probable future economic benefits obtained or controlled by an entity as a result of past transactions or events. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=117815213&loc=d3e19207-110258 + Details
Name: | us-gaap_AssetsFairValueDisclosure
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale). + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 30 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=118942338&loc=SL82898722-210454 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 45 -Paragraph 1 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=118954083&loc=d3e26610-111562 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (aa) -URI http://asc.fasb.org/extlink&oid=118939692&loc=d3e27161-111563 + Details
Name: | us-gaap_AvailableForSaleSecuritiesDebtSecurities
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Fair value portion of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates. + References No definition available. + Details
Name: | us-gaap_CashAndCashEquivalentsFairValueDisclosure
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Fair value, before effects of master netting arrangements, of a financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes assets elected not to be offset. Excludes assets not subject to a master netting arrangement. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 20 -Section 55 -Paragraph 7 -URI http://asc.fasb.org/extlink&oid=99393222&loc=SL20226000-175313 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 860 -SubTopic 20 -Section 50 -Paragraph 4D -Subparagraph (c)(2) -URI http://asc.fasb.org/extlink&oid=118948506&loc=SL51823488-111719 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 20 -Section 50 -Paragraph 3 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=51824906&loc=SL20225862-175312 Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 4B -Subparagraph (a),(c) -URI http://asc.fasb.org/extlink&oid=109980867&loc=SL5624163-113959 + Details
Name: | us-gaap_DerivativeFairValueOfDerivativeAsset
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Fair value, before effects of master netting arrangements, of a financial liability or contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes liabilities elected not to be offset. Excludes liabilities not subject to a master netting arrangement. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 860 -SubTopic 20 -Section 50 -Paragraph 4D -Subparagraph (c)(2) -URI http://asc.fasb.org/extlink&oid=118948506&loc=SL51823488-111719 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 4B -Subparagraph (a),(c) -URI http://asc.fasb.org/extlink&oid=109980867&loc=SL5624163-113959 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 20 -Section 50 -Paragraph 3 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=51824906&loc=SL20225862-175312 Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 20 -Section 55 -Paragraph 7 -URI http://asc.fasb.org/extlink&oid=99393222&loc=SL20226000-175313 + Details
Name: | us-gaap_DerivativeFairValueOfDerivativeLiability
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Fair value portion of investments accounted under the equity method. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 323 -SubTopic 10 -Section 25 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=117311354&loc=d3e32014-111567 + Details
Name: | us-gaap_EquityMethodInvestmentsFairValueDisclosure
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- References No definition available. + Details
Name: | us-gaap_FinancialInstrumentsFinancialAssetsBalanceSheetGroupingsAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- References No definition available. + Details
Name: | us-gaap_FinancialInstrumentsFinancialLiabilitiesBalanceSheetGroupingsAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Fair value portion of guarantee, including, but not limited to, financial standby letter of credit, fair value guarantee, guarantee of collection of scheduled contractual cash flows from financial assets, and contracts that contingently require the guarantor to make payments or perform services. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 460 -SubTopic 10 -Section 50 -Paragraph 5 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=118943654&loc=d3e12201-110248 + Details
Name: | us-gaap_GuaranteesFairValueDisclosure
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Fair value of financial and nonfinancial obligations. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=117815213&loc=d3e19207-110258 + Details
Name: | us-gaap_LiabilitiesFairValueDisclosure
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Fair value portion of loan receivable, including, but not limited to, mortgage loans held for investment, finance receivables held for investment, policy loans on insurance contracts. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -URI http://asc.fasb.org/subtopic&trid=2196772 + Details
Name: | us-gaap_LoansReceivableFairValueDisclosure
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 470 -SubTopic 20 -Section 50 -Paragraph 4 -Subparagraph (b)(3) -URI http://asc.fasb.org/extlink&oid=109500613&loc=SL6031897-161870 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-03(a)(16)) -URI http://asc.fasb.org/extlink&oid=119400593&loc=d3e572229-122910 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-03(16)) -URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878 Reference 4: 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)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
Name: | us-gaap_LongTermDebt
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition The fair value amount of long-term debt whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission. + References No definition available. + Details
Name: | us-gaap_LongTermDebtFairValue
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Amount, after allowance for credit loss, of financing receivable. Excludes financing receivable covered under loss sharing agreement. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 20 -Section 50 -Paragraph 5 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=119407570&loc=SL82919230-210447 Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02(3)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 45 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=118952595&loc=d3e4428-111522 + Details
Name: | us-gaap_NotesReceivableNet
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount of investments classified as other. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-03.1(f,g)) -URI http://asc.fasb.org/extlink&oid=119400593&loc=d3e572229-122910 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.12) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
Name: | us-gaap_OtherInvestments
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount of short-term investments classified as other. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-03.1(g)) -URI http://asc.fasb.org/extlink&oid=119400593&loc=d3e572229-122910 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.8) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-03.5) -URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878 + Details
Name: | us-gaap_OtherShortTermInvestments
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount of cash and cash equivalents restricted as to withdrawal or usage, classified as current. Cash includes, but is not limited to, currency on hand, demand deposits with banks or financial institutions, and other accounts with general characteristics of demand deposits. Cash equivalents include, but are not limited to, short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section 45 -Paragraph 1 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=118951113&loc=d3e6676-107765 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 4 -URI http://asc.fasb.org/extlink&oid=118932676&loc=d3e3044-108585 Reference 3: 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(1)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 50 -Paragraph 8 -URI http://asc.fasb.org/extlink&oid=98513485&loc=SL98516268-108586 + Details
Name: | us-gaap_RestrictedCashAndCashEquivalentsAtCarryingValue
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Details
Name: | us-gaap_FinancialInstrumentAxis=us-gaap_ShortTermInvestmentsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FairValueByMeasurementBasisAxis=us-gaap_EstimateOfFairValueFairValueDisclosureMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FairValueByMeasurementBasisAxis=us-gaap_CarryingReportedAmountFairValueDisclosureMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancialInstrumentAxis=us-gaap_OtherDebtSecuritiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancialInstrumentAxis=us-gaap_InterestRateSwapMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancialInstrumentAxis=us-gaap_OtherCreditDerivativesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_BalanceSheetLocationAxis=us-gaap_OtherAssetsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FairValueByFairValueHierarchyLevelAxis=us-gaap_FairValueInputsLevel1Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancialInstrumentAxis=us-gaap_EquityMethodInvestmentsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancialInstrumentAxis=us-gaap_LoansReceivableMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FairValueByFairValueHierarchyLevelAxis=us-gaap_FairValueInputsLevel2Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FairValueByFairValueHierarchyLevelAxis=us-gaap_FairValueInputsLevel3Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FairValueByAssetClassAxis=us-gaap_CommercialMortgageBackedSecuritiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FairValueByAssetClassAxis=us-gaap_MunicipalBondsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FairValueByAssetClassAxis=us-gaap_CorporateDebtSecuritiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FairValueByAssetClassAxis=us-gaap_ForeignGovernmentDebtSecuritiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FairValueByAssetClassAxis=us-gaap_USGovernmentDebtSecuritiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FairValueByAssetClassAxis=us-gaap_ResidentialMortgageBackedSecuritiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FairValueByAssetClassAxis=us-gaap_CollateralizedDebtObligationsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FairValueByAssetClassAxis=us-gaap_AssetBackedSecuritiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FairValueByMeasurementFrequencyAxis=us-gaap_FairValueMeasurementsRecurringMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancialInstrumentAxis=us-gaap_CommercialMortgageBackedSecuritiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancialInstrumentAxis=us-gaap_AssetBackedSecuritiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancialInstrumentAxis=us-gaap_CollateralizedDebtObligationsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancialInstrumentAxis=us-gaap_ResidentialMortgageBackedSecuritiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancialInstrumentAxis=us-gaap_USGovernmentDebtSecuritiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancialInstrumentAxis=us-gaap_ForeignGovernmentDebtSecuritiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancialInstrumentAxis=us-gaap_CorporateDebtSecuritiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancialInstrumentAxis=us-gaap_MunicipalBondsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_CollateralAxis=us-gaap_CollateralPledgedMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FairValueByAssetClassAxis=us-gaap_ShortTermInvestmentsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_ConsolidatedEntitiesAxis=us-gaap_VariableInterestEntityPrimaryBeneficiaryMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancialInstrumentAxis=us-gaap_CurrencySwapMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |