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Financial Guarantee Insurance Contracts - Additional Information (Detail) € in Millions, £ in Millions, $ in Millions | 12 Months Ended |  |  |  |
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Dec. 31, 2022 USD ($) | Dec. 31, 2021 USD ($) | Dec. 31, 2020 USD ($) | Dec. 31, 2022 GBP (£) | Dec. 31, 2022 EUR (€) | Dec. 31, 2021 GBP (£) | Dec. 31, 2021 EUR (€) | Dec. 31, 2020 GBP (£) | Dec. 31, 2020 EUR (€) | Dec. 31, 2019 USD ($)
Insurance [Line Items] |  |  |  |  |  |  |  |  |  |
Ceded Loss And Loss Expenses Paid Not Yet Recovered |  | $ 0 | $ 0 |  |  |  |  |  |  |
Net par amount of financial guarantees | $ 22,613 | $ 28,020 |  |  |  |  |  |  |  |
Estimated Future Premium Payments Weighted Average Discounted Rate | 3.00% | 2.20% |  | 3.00% | 3.00% | 2.20% | 2.20% |  |  |
Financial Guarantee Insurance Contracts, Premium Receivable | $ 254 | $ 320 | 370 |  |  |  |  |  |  | $ 416
Amount Of Insured Par Outstanding Ceded To Reinsurer | $ 2,187 |  |  |  |  |  |  |  |  |
Ceded Principal Outstanding Major Reinsurer Percentage | 7.90% |  |  |  |  |  |  |  |  |
Reinsurance Payable | $ 39 | $ 33 |  |  |  |  |  |  |  |
Weighted average period of future premiums | 8 years | 8 years |  |  |  |  |  |  |  |
Uncollectable premium receivables | $ 5 | $ 9 |  |  |  |  |  |  |  |
Accelerated premium revenue for retired obligations | 8 | 1 | 12 |  |  |  |  |  |  |
Reinsurance recoveries of losses included in losses and loss expenses | (41) | 5 | (7) |  |  |  |  |  |  |
Losses and loss expense reserves ceded to reinsurers |  | 24 |  |  |  |  |  |  |  |
Subrogation recoveries, net of reinsurance | (140) | (1,704) |  |  |  |  |  |  |  |
Amortization of intangible assets | 47 | 55 | 57 |  |  |  |  |  |  |
Intangible assets | 326 | 362 |  |  |  |  |  |  |  |
Financial Guarantee Outstanding Principal Ceded To Third Parties | 4,938 |  |  |  |  |  |  |  |  |
Premiums Receivable, Gross | 259 | 329 |  |  |  |  |  |  |  |
Allowance for Doubtful Accounts, Premiums and Other Receivables | 5 | 9 | 17 |  |  |  |  |  |  |
Premium Receivable, Credit Loss Expense (Reversal) | (4) | (6) |  |  |  |  |  |  |  |
Premium Receivable, Allowance for Credit Loss, Writeoff | 0 | (2) |  |  |  |  |  |  |  |
Reinsurance Recoverable, Allowance for Credit Loss | 0 | 0 |  |  |  |  |  |  |  |
Net Incurred RMBS Subrogation Recoveries | (123) | 20 | (23) |  |  |  |  |  |  |
Reinsurance Recoverables, Gross | 115 |  |  |  |  |  |  |  |  |
Net unsecured reinsurance recoverable | 60 |  |  |  |  |  |  |  |  |
Reinsurance Recoverable, Gross, All Other | 18 |  |  |  |  |  |  |  |  |
Unsecured Reinsurance Recoverable, All Other | 7 |  |  |  |  |  |  |  |  |
Specialty Property & Casualty Program [Domain] |  |  |  |  |  |  |  |  |  |
Insurance [Line Items] |  |  |  |  |  |  |  |  |  |
Premiums Receivable, Gross | $ 16 | 2 |  |  |  |  |  |  |  |
Property and Casualty, Commercial Insurance |  |  |  |  |  |  |  |  |  |
Insurance [Line Items] |  |  |  |  |  |  |  |  |  |
Reinsurance, Reinsured Risk, Percentage | 70.00% |  |  |  |  |  |  |  |  |
Financial Guarantee |  |  |  |  |  |  |  |  |  |
Insurance [Line Items] |  |  |  |  |  |  |  |  |  |
Ceded Loss And Loss Expenses Paid Not Yet Recovered | $ 0 |  |  |  |  |  |  |  |  |
Losses and loss expense reserves ceded to reinsurers | 33 |  |  |  |  |  |  |  |  |
Financial Guarantee | Assured Guaranty Re Ltd [Member] |  |  |  |  |  |  |  |  |  |
Insurance [Line Items] |  |  |  |  |  |  |  |  |  |
Reinsurance Recoverables, Gross | 30 |  |  |  |  |  |  |  |  |
Net unsecured reinsurance recoverable | 0 |  |  |  |  |  |  |  |  |
Property and Casualty, Commercial Insurance | QBE Insurance Corporation |  |  |  |  |  |  |  |  |  |
Insurance [Line Items] |  |  |  |  |  |  |  |  |  |
Reinsurance Recoverables, Gross | 41 |  |  |  |  |  |  |  |  |
Net unsecured reinsurance recoverable | 41 |  |  |  |  |  |  |  |  |
Property and Casualty, Commercial Insurance | General Reinsurance Company |  |  |  |  |  |  |  |  |  |
Insurance [Line Items] |  |  |  |  |  |  |  |  |  |
Reinsurance Recoverables, Gross | 25 |  |  |  |  |  |  |  |  |
Net unsecured reinsurance recoverable | 11 |  |  |  |  |  |  |  |  |
Surveillance Category One [Member] |  |  |  |  |  |  |  |  |  |
Insurance [Line Items] |  |  |  |  |  |  |  |  |  |
Premiums Receivable, Gross | 217 | 277 |  |  |  |  |  |  |  |
IA [Member] |  |  |  |  |  |  |  |  |  |
Insurance [Line Items] |  |  |  |  |  |  |  |  |  |
Premiums Receivable, Gross | 10 | 12 |  |  |  |  |  |  |  |
II [Member] |  |  |  |  |  |  |  |  |  |
Insurance [Line Items] |  |  |  |  |  |  |  |  |  |
Premiums Receivable, Gross | 5 | 6 |  |  |  |  |  |  |  |
III [Member] |  |  |  |  |  |  |  |  |  |
Insurance [Line Items] |  |  |  |  |  |  |  |  |  |
Premiums Receivable, Gross | 16 | 22 |  |  |  |  |  |  |  |
IV [Member] |  |  |  |  |  |  |  |  |  |
Insurance [Line Items] |  |  |  |  |  |  |  |  |  |
Premiums Receivable, Gross | $ 11 | $ 12 |  |  |  |  |  |  |  |
Maximum [Member] | Furniture and Fixtures [Member] |  |  |  |  |  |  |  |  |  |
Insurance [Line Items] |  |  |  |  |  |  |  |  |  |
Finite-Lived Intangible Asset, Useful Life | 5 years |  |  |  |  |  |  |  |  |
Loss Reserves [Member] |  |  |  |  |  |  |  |  |  |
Insurance [Line Items] |  |  |  |  |  |  |  |  |  |
Weighted average risk-free rate used to discount loss reserves | 3.90% | 1.20% |  |  |  |  |  |  |  |
United Kingdom, Pounds |  |  |  |  |  |  |  |  |  |
Insurance [Line Items] |  |  |  |  |  |  |  |  |  |
Financial Guarantee Insurance Contracts, Premium Receivable | $ 71 | $ 108 | 117 | £ 59 |  | £ 80 |  | £ 86 |  |
Euro Member Countries, Euro |  |  |  |  |  |  |  |  |  |
Insurance [Line Items] |  |  |  |  |  |  |  |  |  |
Financial Guarantee Insurance Contracts, Premium Receivable | 14 | 16 | $ 19 |  | € 13 |  | € 14 |  | € 16 |
Public Finance [Member] |  |  |  |  |  |  |  |  |  |
Insurance [Line Items] |  |  |  |  |  |  |  |  |  |
Net par amount of financial guarantees | 10,547 | 12,360 |  |  |  |  |  |  |  |
Premiums Receivable, Gross | 150 | 159 |  |  |  |  |  |  |  |
Public Finance [Member] | Surveillance Category One [Member] |  |  |  |  |  |  |  |  |  |
Insurance [Line Items] |  |  |  |  |  |  |  |  |  |
Premiums Receivable, Gross | 142 | 151 |  |  |  |  |  |  |  |
Public Finance [Member] | IA [Member] |  |  |  |  |  |  |  |  |  |
Insurance [Line Items] |  |  |  |  |  |  |  |  |  |
Premiums Receivable, Gross | 3 | 3 |  |  |  |  |  |  |  |
Public Finance [Member] | II [Member] |  |  |  |  |  |  |  |  |  |
Insurance [Line Items] |  |  |  |  |  |  |  |  |  |
Premiums Receivable, Gross | 5 | 5 |  |  |  |  |  |  |  |
Public Finance [Member] | III [Member] |  |  |  |  |  |  |  |  |  |
Insurance [Line Items] |  |  |  |  |  |  |  |  |  |
Premiums Receivable, Gross | 0 | 0 |  |  |  |  |  |  |  |
Public Finance [Member] | IV [Member] |  |  |  |  |  |  |  |  |  |
Insurance [Line Items] |  |  |  |  |  |  |  |  |  |
Premiums Receivable, Gross | 0 | 0 |  |  |  |  |  |  |  |
Structured Finance [Member] |  |  |  |  |  |  |  |  |  |
Insurance [Line Items] |  |  |  |  |  |  |  |  |  |
Net par amount of financial guarantees | 3,612 | 4,904 |  |  |  |  |  |  |  |
Premiums Receivable, Gross | 24 | 45 |  |  |  |  |  |  |  |
Structured Finance [Member] | Surveillance Category One [Member] |  |  |  |  |  |  |  |  |  |
Insurance [Line Items] |  |  |  |  |  |  |  |  |  |
Premiums Receivable, Gross | 5 | 19 |  |  |  |  |  |  |  |
Structured Finance [Member] | IA [Member] |  |  |  |  |  |  |  |  |  |
Insurance [Line Items] |  |  |  |  |  |  |  |  |  |
Premiums Receivable, Gross | 1 | 1 |  |  |  |  |  |  |  |
Structured Finance [Member] | II [Member] |  |  |  |  |  |  |  |  |  |
Insurance [Line Items] |  |  |  |  |  |  |  |  |  |
Premiums Receivable, Gross | 0 | 1 |  |  |  |  |  |  |  |
Structured Finance [Member] | III [Member] |  |  |  |  |  |  |  |  |  |
Insurance [Line Items] |  |  |  |  |  |  |  |  |  |
Premiums Receivable, Gross | 7 | 12 |  |  |  |  |  |  |  |
Structured Finance [Member] | IV [Member] |  |  |  |  |  |  |  |  |  |
Insurance [Line Items] |  |  |  |  |  |  |  |  |  |
Premiums Receivable, Gross | 11 | 12 |  |  |  |  |  |  |  |
International Finance [Member] |  |  |  |  |  |  |  |  |  |
Insurance [Line Items] |  |  |  |  |  |  |  |  |  |
Net par amount of financial guarantees | 8,454 | 10,756 |  |  |  |  |  |  |  |
Premiums Receivable, Gross | 85 | 125 |  |  |  |  |  |  |  |
International Finance [Member] | Surveillance Category One [Member] |  |  |  |  |  |  |  |  |  |
Insurance [Line Items] |  |  |  |  |  |  |  |  |  |
Premiums Receivable, Gross | 70 | 107 |  |  |  |  |  |  |  |
International Finance [Member] | IA [Member] |  |  |  |  |  |  |  |  |  |
Insurance [Line Items] |  |  |  |  |  |  |  |  |  |
Premiums Receivable, Gross | 7 | 8 |  |  |  |  |  |  |  |
International Finance [Member] | II [Member] |  |  |  |  |  |  |  |  |  |
Insurance [Line Items] |  |  |  |  |  |  |  |  |  |
Premiums Receivable, Gross | 0 | 0 |  |  |  |  |  |  |  |
International Finance [Member] | III [Member] |  |  |  |  |  |  |  |  |  |
Insurance [Line Items] |  |  |  |  |  |  |  |  |  |
Premiums Receivable, Gross | 9 | 11 |  |  |  |  |  |  |  |
International Finance [Member] | IV [Member] |  |  |  |  |  |  |  |  |  |
Insurance [Line Items] |  |  |  |  |  |  |  |  |  |
Premiums Receivable, Gross | 0 | 0 |  |  |  |  |  |  |  |
Housing Revenue [Member] | Public Finance [Member] |  |  |  |  |  |  |  |  |  |
Insurance [Line Items] |  |  |  |  |  |  |  |  |  |
Net par amount of financial guarantees | 5,491 | 5,610 |  |  |  |  |  |  |  |
Premiums Receivable, Gross | 148 | 157 |  |  |  |  |  |  |  |
Housing Revenue [Member] | Public Finance [Member] | Surveillance Category One [Member] |  |  |  |  |  |  |  |  |  |
Insurance [Line Items] |  |  |  |  |  |  |  |  |  |
Premiums Receivable, Gross | 140 | 149 |  |  |  |  |  |  |  |
Housing Revenue [Member] | Public Finance [Member] | IA [Member] |  |  |  |  |  |  |  |  |  |
Insurance [Line Items] |  |  |  |  |  |  |  |  |  |
Premiums Receivable, Gross | 3 | 3 |  |  |  |  |  |  |  |
Housing Revenue [Member] | Public Finance [Member] | II [Member] |  |  |  |  |  |  |  |  |  |
Insurance [Line Items] |  |  |  |  |  |  |  |  |  |
Premiums Receivable, Gross | 5 | 5 |  |  |  |  |  |  |  |
Housing Revenue [Member] | Public Finance [Member] | III [Member] |  |  |  |  |  |  |  |  |  |
Insurance [Line Items] |  |  |  |  |  |  |  |  |  |
Premiums Receivable, Gross | 0 | 0 |  |  |  |  |  |  |  |
Housing Revenue [Member] | Public Finance [Member] | IV [Member] |  |  |  |  |  |  |  |  |  |
Insurance [Line Items] |  |  |  |  |  |  |  |  |  |
Premiums Receivable, Gross | 0 | 0 |  |  |  |  |  |  |  |
Housing Revenue [Member] | Military Housing [Member] | Public Finance [Member] |  |  |  |  |  |  |  |  |  |
Insurance [Line Items] |  |  |  |  |  |  |  |  |  |
Net par amount of financial guarantees | 5,400 | 5,490 |  |  |  |  |  |  |  |
Other Public Finance Sectors [Member] | Public Finance [Member] |  |  |  |  |  |  |  |  |  |
Insurance [Line Items] |  |  |  |  |  |  |  |  |  |
Premiums Receivable, Gross | 2 | 2 |  |  |  |  |  |  |  |
Other Public Finance Sectors [Member] | Public Finance [Member] | Surveillance Category One [Member] |  |  |  |  |  |  |  |  |  |
Insurance [Line Items] |  |  |  |  |  |  |  |  |  |
Premiums Receivable, Gross | 2 | 2 |  |  |  |  |  |  |  |
Other Public Finance Sectors [Member] | Public Finance [Member] | IA [Member] |  |  |  |  |  |  |  |  |  |
Insurance [Line Items] |  |  |  |  |  |  |  |  |  |
Premiums Receivable, Gross | 0 | 0 |  |  |  |  |  |  |  |
Other Public Finance Sectors [Member] | Public Finance [Member] | II [Member] |  |  |  |  |  |  |  |  |  |
Insurance [Line Items] |  |  |  |  |  |  |  |  |  |
Premiums Receivable, Gross | 0 | 0 |  |  |  |  |  |  |  |
Other Public Finance Sectors [Member] | Public Finance [Member] | III [Member] |  |  |  |  |  |  |  |  |  |
Insurance [Line Items] |  |  |  |  |  |  |  |  |  |
Premiums Receivable, Gross | 0 | 0 |  |  |  |  |  |  |  |
Other Public Finance Sectors [Member] | Public Finance [Member] | IV [Member] |  |  |  |  |  |  |  |  |  |
Insurance [Line Items] |  |  |  |  |  |  |  |  |  |
Premiums Receivable, Gross | 0 | 0 |  |  |  |  |  |  |  |
Mortgage-backed and Home Equity [Member] | Structured Finance [Member] |  |  |  |  |  |  |  |  |  |
Insurance [Line Items] |  |  |  |  |  |  |  |  |  |
Net par amount of financial guarantees | 1,930 | 2,724 |  |  |  |  |  |  |  |
Premiums Receivable, Gross | 11 | 16 |  |  |  |  |  |  |  |
Mortgage-backed and Home Equity [Member] | Structured Finance [Member] | Surveillance Category One [Member] |  |  |  |  |  |  |  |  |  |
Insurance [Line Items] |  |  |  |  |  |  |  |  |  |
Premiums Receivable, Gross | 0 | 1 |  |  |  |  |  |  |  |
Mortgage-backed and Home Equity [Member] | Structured Finance [Member] | IA [Member] |  |  |  |  |  |  |  |  |  |
Insurance [Line Items] |  |  |  |  |  |  |  |  |  |
Premiums Receivable, Gross | 0 | 0 |  |  |  |  |  |  |  |
Mortgage-backed and Home Equity [Member] | Structured Finance [Member] | II [Member] |  |  |  |  |  |  |  |  |  |
Insurance [Line Items] |  |  |  |  |  |  |  |  |  |
Premiums Receivable, Gross | 0 | 1 |  |  |  |  |  |  |  |
Mortgage-backed and Home Equity [Member] | Structured Finance [Member] | III [Member] |  |  |  |  |  |  |  |  |  |
Insurance [Line Items] |  |  |  |  |  |  |  |  |  |
Premiums Receivable, Gross | 0 | 2 |  |  |  |  |  |  |  |
Mortgage-backed and Home Equity [Member] | Structured Finance [Member] | IV [Member] |  |  |  |  |  |  |  |  |  |
Insurance [Line Items] |  |  |  |  |  |  |  |  |  |
Premiums Receivable, Gross | 11 | 12 |  |  |  |  |  |  |  |
Structured Insurance [Member] | Structured Finance [Member] |  |  |  |  |  |  |  |  |  |
Insurance [Line Items] |  |  |  |  |  |  |  |  |  |
Premiums Receivable, Gross | 0 | 10 |  |  |  |  |  |  |  |
Structured Insurance [Member] | Structured Finance [Member] | Surveillance Category One [Member] |  |  |  |  |  |  |  |  |  |
Insurance [Line Items] |  |  |  |  |  |  |  |  |  |
Premiums Receivable, Gross | 0 | 10 |  |  |  |  |  |  |  |
Structured Insurance [Member] | Structured Finance [Member] | IA [Member] |  |  |  |  |  |  |  |  |  |
Insurance [Line Items] |  |  |  |  |  |  |  |  |  |
Premiums Receivable, Gross | 0 | 0 |  |  |  |  |  |  |  |
Structured Insurance [Member] | Structured Finance [Member] | II [Member] |  |  |  |  |  |  |  |  |  |
Insurance [Line Items] |  |  |  |  |  |  |  |  |  |
Premiums Receivable, Gross | 0 | 0 |  |  |  |  |  |  |  |
Structured Insurance [Member] | Structured Finance [Member] | III [Member] |  |  |  |  |  |  |  |  |  |
Insurance [Line Items] |  |  |  |  |  |  |  |  |  |
Premiums Receivable, Gross | 0 | 0 |  |  |  |  |  |  |  |
Structured Insurance [Member] | Structured Finance [Member] | IV [Member] |  |  |  |  |  |  |  |  |  |
Insurance [Line Items] |  |  |  |  |  |  |  |  |  |
Premiums Receivable, Gross | 0 | 0 |  |  |  |  |  |  |  |
Student Loan [Member] | Structured Finance [Member] |  |  |  |  |  |  |  |  |  |
Insurance [Line Items] |  |  |  |  |  |  |  |  |  |
Premiums Receivable, Gross | 8 | 12 |  |  |  |  |  |  |  |
Student Loan [Member] | Structured Finance [Member] | Surveillance Category One [Member] |  |  |  |  |  |  |  |  |  |
Insurance [Line Items] |  |  |  |  |  |  |  |  |  |
Premiums Receivable, Gross | 1 | 1 |  |  |  |  |  |  |  |
Student Loan [Member] | Structured Finance [Member] | IA [Member] |  |  |  |  |  |  |  |  |  |
Insurance [Line Items] |  |  |  |  |  |  |  |  |  |
Premiums Receivable, Gross | 1 | 1 |  |  |  |  |  |  |  |
Student Loan [Member] | Structured Finance [Member] | II [Member] |  |  |  |  |  |  |  |  |  |
Insurance [Line Items] |  |  |  |  |  |  |  |  |  |
Premiums Receivable, Gross | 0 | 0 |  |  |  |  |  |  |  |
Student Loan [Member] | Structured Finance [Member] | III [Member] |  |  |  |  |  |  |  |  |  |
Insurance [Line Items] |  |  |  |  |  |  |  |  |  |
Premiums Receivable, Gross | 7 | 9 |  |  |  |  |  |  |  |
Student Loan [Member] | Structured Finance [Member] | IV [Member] |  |  |  |  |  |  |  |  |  |
Insurance [Line Items] |  |  |  |  |  |  |  |  |  |
Premiums Receivable, Gross | 0 | 0 |  |  |  |  |  |  |  |
Other Structured Finance [Member] | Structured Finance [Member] |  |  |  |  |  |  |  |  |  |
Insurance [Line Items] |  |  |  |  |  |  |  |  |  |
Net par amount of financial guarantees | 579 | 624 |  |  |  |  |  |  |  |
Premiums Receivable, Gross | 4 | 7 |  |  |  |  |  |  |  |
Other Structured Finance [Member] | Structured Finance [Member] | Surveillance Category One [Member] |  |  |  |  |  |  |  |  |  |
Insurance [Line Items] |  |  |  |  |  |  |  |  |  |
Premiums Receivable, Gross | 4 | 7 |  |  |  |  |  |  |  |
Other Structured Finance [Member] | Structured Finance [Member] | IA [Member] |  |  |  |  |  |  |  |  |  |
Insurance [Line Items] |  |  |  |  |  |  |  |  |  |
Premiums Receivable, Gross | 0 | 0 |  |  |  |  |  |  |  |
Other Structured Finance [Member] | Structured Finance [Member] | II [Member] |  |  |  |  |  |  |  |  |  |
Insurance [Line Items] |  |  |  |  |  |  |  |  |  |
Premiums Receivable, Gross | 0 | 0 |  |  |  |  |  |  |  |
Other Structured Finance [Member] | Structured Finance [Member] | III [Member] |  |  |  |  |  |  |  |  |  |
Insurance [Line Items] |  |  |  |  |  |  |  |  |  |
Premiums Receivable, Gross | 0 | 0 |  |  |  |  |  |  |  |
Other Structured Finance [Member] | Structured Finance [Member] | IV [Member] |  |  |  |  |  |  |  |  |  |
Insurance [Line Items] |  |  |  |  |  |  |  |  |  |
Premiums Receivable, Gross | 0 | 0 |  |  |  |  |  |  |  |
Sovereign/Sub-sovereign [Member] | International Finance [Member] |  |  |  |  |  |  |  |  |  |
Insurance [Line Items] |  |  |  |  |  |  |  |  |  |
Net par amount of financial guarantees | 4,077 | 5,141 |  |  |  |  |  |  |  |
Premiums Receivable, Gross | 64 | 93 |  |  |  |  |  |  |  |
Sovereign/Sub-sovereign [Member] | International Finance [Member] | Surveillance Category One [Member] |  |  |  |  |  |  |  |  |  |
Insurance [Line Items] |  |  |  |  |  |  |  |  |  |
Premiums Receivable, Gross | 49 | 74 |  |  |  |  |  |  |  |
Sovereign/Sub-sovereign [Member] | International Finance [Member] | IA [Member] |  |  |  |  |  |  |  |  |  |
Insurance [Line Items] |  |  |  |  |  |  |  |  |  |
Premiums Receivable, Gross | 7 | 8 |  |  |  |  |  |  |  |
Sovereign/Sub-sovereign [Member] | International Finance [Member] | II [Member] |  |  |  |  |  |  |  |  |  |
Insurance [Line Items] |  |  |  |  |  |  |  |  |  |
Premiums Receivable, Gross | 0 | 0 |  |  |  |  |  |  |  |
Sovereign/Sub-sovereign [Member] | International Finance [Member] | III [Member] |  |  |  |  |  |  |  |  |  |
Insurance [Line Items] |  |  |  |  |  |  |  |  |  |
Premiums Receivable, Gross | 9 | 11 |  |  |  |  |  |  |  |
Sovereign/Sub-sovereign [Member] | International Finance [Member] | IV [Member] |  |  |  |  |  |  |  |  |  |
Insurance [Line Items] |  |  |  |  |  |  |  |  |  |
Premiums Receivable, Gross | 0 | 0 |  |  |  |  |  |  |  |
Investor-owned and Public Utilities [Member] | International Finance [Member] |  |  |  |  |  |  |  |  |  |
Insurance [Line Items] |  |  |  |  |  |  |  |  |  |
Net par amount of financial guarantees | 2,583 | 3,283 |  |  |  |  |  |  |  |
Premiums Receivable, Gross | 18 | 28 |  |  |  |  |  |  |  |
Investor-owned and Public Utilities [Member] | International Finance [Member] | Surveillance Category One [Member] |  |  |  |  |  |  |  |  |  |
Insurance [Line Items] |  |  |  |  |  |  |  |  |  |
Premiums Receivable, Gross | 18 | 28 |  |  |  |  |  |  |  |
Investor-owned and Public Utilities [Member] | International Finance [Member] | IA [Member] |  |  |  |  |  |  |  |  |  |
Insurance [Line Items] |  |  |  |  |  |  |  |  |  |
Premiums Receivable, Gross | 0 | 0 |  |  |  |  |  |  |  |
Investor-owned and Public Utilities [Member] | International Finance [Member] | II [Member] |  |  |  |  |  |  |  |  |  |
Insurance [Line Items] |  |  |  |  |  |  |  |  |  |
Premiums Receivable, Gross | 0 | 0 |  |  |  |  |  |  |  |
Investor-owned and Public Utilities [Member] | International Finance [Member] | III [Member] |  |  |  |  |  |  |  |  |  |
Insurance [Line Items] |  |  |  |  |  |  |  |  |  |
Premiums Receivable, Gross | 0 | 0 |  |  |  |  |  |  |  |
Investor-owned and Public Utilities [Member] | International Finance [Member] | IV [Member] |  |  |  |  |  |  |  |  |  |
Insurance [Line Items] |  |  |  |  |  |  |  |  |  |
Premiums Receivable, Gross | 0 | 0 |  |  |  |  |  |  |  |
Other International [Member] | International Finance [Member] |  |  |  |  |  |  |  |  |  |
Insurance [Line Items] |  |  |  |  |  |  |  |  |  |
Premiums Receivable, Gross | 2 | 5 |  |  |  |  |  |  |  |
Other International [Member] | International Finance [Member] | Surveillance Category One [Member] |  |  |  |  |  |  |  |  |  |
Insurance [Line Items] |  |  |  |  |  |  |  |  |  |
Premiums Receivable, Gross | 2 | 5 |  |  |  |  |  |  |  |
Other International [Member] | International Finance [Member] | IA [Member] |  |  |  |  |  |  |  |  |  |
Insurance [Line Items] |  |  |  |  |  |  |  |  |  |
Premiums Receivable, Gross | 0 | 0 |  |  |  |  |  |  |  |
Other International [Member] | International Finance [Member] | II [Member] |  |  |  |  |  |  |  |  |  |
Insurance [Line Items] |  |  |  |  |  |  |  |  |  |
Premiums Receivable, Gross | 0 | 0 |  |  |  |  |  |  |  |
Other International [Member] | International Finance [Member] | III [Member] |  |  |  |  |  |  |  |  |  |
Insurance [Line Items] |  |  |  |  |  |  |  |  |  |
Premiums Receivable, Gross | 0 | 0 |  |  |  |  |  |  |  |
Other International [Member] | International Finance [Member] | IV [Member] |  |  |  |  |  |  |  |  |  |
Insurance [Line Items] |  |  |  |  |  |  |  |  |  |
Premiums Receivable, Gross | $ 0 | $ 0 |  |  |  |  |  |  |  |

X
- Definition Amount of insured par outstanding ceded to reinsurer. + References No definition available. + Details
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Namespace Prefix: | ambc_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition This element represents the reduction to gross claim liability for subrogation on insured RMBS financial obligations with credit deterioration, net of reinsurance. + References No definition available. + Details
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Namespace Prefix: | ambc_
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Balance Type: | debit
Period Type: | instant

X
- Definition Ceded Loss And Loss Expenses Paid Not Yet Recovered + References No definition available. + Details
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Namespace Prefix: | ambc_
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Balance Type: | debit
Period Type: | instant

X
- Definition Ceded Principal Outstanding Major Reinsurer Percentage. + References No definition available. + Details
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Namespace Prefix: | ambc_
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Balance Type: | na
Period Type: | duration

X
- Definition Weighted average discounted rate of estimated future premium payments to be paid by the VIEs. + References No definition available. + Details
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Namespace Prefix: | ambc_
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Balance Type: | na
Period Type: | instant

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- Definition Financial Guarantee Outstanding Principal Ceded to third parties. + References No definition available. + Details
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Balance Type: | debit
Period Type: | instant

X
- Definition Insurance [Line Items] + References No definition available. + Details
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Balance Type: | na
Period Type: | duration

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- Definition The known and estimated amount recoverable as of the balance sheet date from reinsurers for claims expected to be paid or incurred by the ceding insurer. + References No definition available. + Details
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Balance Type: | debit
Period Type: | instant

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- Definition Net Incurred RMBS Subrogation Recoveries + References No definition available. + Details
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Balance Type: | debit
Period Type: | duration

X
- Definition Reinsurance Recoverable, Gross, All Other + References No definition available. + Details
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Namespace Prefix: | ambc_
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Balance Type: | debit
Period Type: | instant

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- Definition Unsecured Reinsurance Recoverable, All Other + References No definition available. + Details
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Balance Type: | debit
Period Type: | instant

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- Definition Represents reinsurance recoverables on paid and unpaid losses and deferred ceded premiums, net of ceded premiums payables due to reinsurers, letters of credit, and collateral posted for the benefit of the cedant. + References No definition available. + Details
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Period Type: | instant

X
- Definition The valuation allowance as of the balance sheet date to reduce the gross amount of receivables to estimated net realizable value, which would be presented in parentheses on the face of the balance sheet. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 4 -URI https://asc.fasb.org/extlink&oid=123577603&loc=d3e5074-111524 + Details
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- Definition The aggregate expense charged against earnings to allocate the cost of intangible assets (nonphysical assets not used in production) in a systematic and rational manner to the periods expected to benefit from such assets. As a noncash expense, this element is added back to net income when calculating cash provided by or used in operations using the indirect method. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (b) -URI https://asc.fasb.org/extlink&oid=126954810&loc=d3e3602-108585 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 350 -SubTopic 30 -Section 50 -Paragraph 2 -Subparagraph (a)(2) -URI https://asc.fasb.org/extlink&oid=66006027&loc=d3e16323-109275 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 350 -SubTopic 30 -Section 45 -Paragraph 2 -URI https://asc.fasb.org/extlink&oid=6388964&loc=d3e16225-109274 + Details
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- Definition This element represents the amount of premium revenue on financial guarantee insurance contracts recognized during the period that was accelerated for revenue recognition purposes. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 605 -Section 50 -Paragraph 4 -Subparagraph (a) -URI https://asc.fasb.org/extlink&oid=6933581&loc=SL5749298-161291 + Details
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- Definition This element represents the weighted average risk free rate used to discount the claim liability related to financial guarantee insurance contracts. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 40 -Section 50 -Paragraph 9 -Subparagraph (a)(1) -URI https://asc.fasb.org/extlink&oid=99382878&loc=SL5749324-161292 + Details
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X
- Definition Amount of the premium receivable for financial guarantee insurance contracts reported in the statement of financial position. This element primarily would consist of those financial guarantee insurance contracts which premiums are to be collected over the contract period, but may, on occasion, include premiums which are to be collected in full at inception, but which straddle a financial reporting period. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 310 -Section 50 -Paragraph 3 -Subparagraph (c)(1),(5) -URI https://asc.fasb.org/extlink&oid=6933075&loc=SL5748726-161290 + Details
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X
- Definition Weighted average period over which premium receivable for financial guarantee insurance contracts is collected where premium is received over the contract period, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 310 -Section 50 -Paragraph 3 -Subparagraph (a)(5) -URI https://asc.fasb.org/extlink&oid=6933075&loc=SL5748726-161290 + Details
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- Definition Useful life of finite-lived intangible assets, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. + References No definition available. + Details
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Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

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- Definition Sum of the carrying amounts of all intangible assets, excluding goodwill, as of the balance sheet date, net of accumulated amortization and impairment charges. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 350 -SubTopic 30 -Section 50 -Paragraph 2 -Subparagraph ((a)(1),(b)) -URI https://asc.fasb.org/extlink&oid=66006027&loc=d3e16323-109275 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 350 -SubTopic 30 -Section 45 -Paragraph 1 -URI https://asc.fasb.org/extlink&oid=6388964&loc=d3e16212-109274 + Details
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Balance Type: | debit
Period Type: | instant

X
- Definition Amount of participating insurance in force. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 50 -Section 50 -Paragraph 1 -Subparagraph (a) -URI https://asc.fasb.org/extlink&oid=6483535&loc=d3e16392-158451 + Details
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Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Amount of expense (reversal of expense) for expected credit loss on premium receivable. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 20 -Section 50 -Paragraph 13 -Subparagraph (b) -URI https://asc.fasb.org/extlink&oid=124255953&loc=SL82919249-210447 + Details
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Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition The carrying value as of the balance sheet date of the estimated valuation allowance to reduce gross premiums receivable to net realizable value. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-03(5)) -URI https://asc.fasb.org/extlink&oid=126734703&loc=d3e572229-122910 Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 20 -Section 50 -Paragraph 13 -Subparagraph (a) -URI https://asc.fasb.org/extlink&oid=124255953&loc=SL82919249-210447 Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 20 -Section 50 -Paragraph 13 -Subparagraph (f) -URI https://asc.fasb.org/extlink&oid=124255953&loc=SL82919249-210447 Reference 4: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 11B -Subparagraph (b) -URI https://asc.fasb.org/extlink&oid=123577603&loc=SL6953423-111524 Reference 5: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 4 -URI https://asc.fasb.org/extlink&oid=123577603&loc=d3e5074-111524 + Details
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Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Amount of writeoff of premium receivable, charged against allowance for credit loss. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 20 -Section 50 -Paragraph 13 -Subparagraph (d) -URI https://asc.fasb.org/extlink&oid=124255953&loc=SL82919249-210447 Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 11B -Subparagraph (c)(3) -URI https://asc.fasb.org/extlink&oid=123577603&loc=SL6953423-111524 + Details
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X
- Definition Gross amount, as of the balance sheet date, due the entity from (a) agents and insureds, (b) uncollected premiums and (c) others, before deducting the allowance for doubtful accounts. + 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 210.7-03.5) -URI https://asc.fasb.org/extlink&oid=126734703&loc=d3e572229-122910 + Details
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Balance Type: | debit
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X
- Definition Amount of reduction of provision for policy benefits and costs incurred for policies ceded. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 20 -Section 50 -Paragraph 3 -URI https://asc.fasb.org/extlink&oid=99397103&loc=d3e6811-158387 + Details
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Period Type: | duration

X
- Definition The carrying amount as of the balance sheet date of the known and estimated amounts owed to insurers under reinsurance treaties or other arrangements. + References No definition available. + Details
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Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Amount of allowance for credit loss on reinsurance recoverable. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 20 -Section 50 -Paragraph 13 -Subparagraph (a) -URI https://asc.fasb.org/extlink&oid=124255953&loc=SL82919249-210447 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 20 -Section 50 -Paragraph 13 -Subparagraph (f) -URI https://asc.fasb.org/extlink&oid=124255953&loc=SL82919249-210447 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 20 -Section 45 -Paragraph 1 -URI https://asc.fasb.org/extlink&oid=124255206&loc=SL82895884-210446 + Details
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- Definition Amount before valuation allowance recoverable under reinsurance contracts. Examples include, but are not limited to, settled and unsettled claims, incurred but not reported losses, loss adjustment expense, premium paid, policy benefits and policy reserves. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 20 -Section 50 -Paragraph 14 -URI https://asc.fasb.org/extlink&oid=124255953&loc=SL82919253-210447 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 7A -URI https://asc.fasb.org/extlink&oid=123577603&loc=SL6953401-111524 + Details
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- Definition Percentage of risk undertaken originally by insurer ceded to reinsurer. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 20 -Section 50 -Paragraph 3 -URI https://asc.fasb.org/extlink&oid=99397103&loc=d3e6811-158387 + Details
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- Details
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- Details
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