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Financial Guarantees in Force - Summary of Financial Guarantee Portfolio Diversification by Type of Guaranteed Bond (Detail) - USD ($) $ in Millions | 12 Months Ended |
--- | --- | ---
Dec. 31, 2023 | Dec. 31, 2022
Guarantor Obligations [Line Items] |  |
Net Par Amount Outstanding | $ 19,541 | $ 22,613
Total Net Par Outstanding Does Not Exceed This Percentage in Any of the States in the US | 6.00% |
Highest single insured risk of aggregate net par amount guaranteed | 4.60% |
Public Finance [Member] |  |
Guarantor Obligations [Line Items] |  |
Net Par Amount Outstanding | $ 7,562 | 10,547
Public Finance [Member] | Lease and Tax-backed Revenue [Member] |  |
Guarantor Obligations [Line Items] |  |
Net Par Amount Outstanding | 1,542 | 1,979
Public Finance [Member] | General Obligation [Member] |  |
Guarantor Obligations [Line Items] |  |
Net Par Amount Outstanding | 1,051 | 1,301
Public Finance [Member] | Housing Revenue [Member] |  |
Guarantor Obligations [Line Items] |  |
Net Par Amount Outstanding | 3,443 | 5,491
Public Finance [Member] | Housing Revenue [Member] | Military Housing [Member] |  |
Guarantor Obligations [Line Items] |  |
Net Par Amount Outstanding | 3,371 | 5,400
Public Finance [Member] | Other [Member] |  |
Guarantor Obligations [Line Items] |  |
Net Par Amount Outstanding | 1,526 | 1,776
Structured Finance [Member] |  |
Guarantor Obligations [Line Items] |  |
Net Par Amount Outstanding | 3,315 | 3,612
Structured Finance [Member] | Mortgage-backed and Home Equity [Member] |  |
Guarantor Obligations [Line Items] |  |
Net Par Amount Outstanding | 1,712 | 1,930
Structured Finance [Member] | Investor-owned Utilities [Member] |  |
Guarantor Obligations [Line Items] |  |
Net Par Amount Outstanding | 1,077 | 1,103
Structured Finance [Member] | Other Structured Finance [Member] |  |
Guarantor Obligations [Line Items] |  |
Net Par Amount Outstanding | 526 | 579
International Finance [Member] |  |
Guarantor Obligations [Line Items] |  |
Net Par Amount Outstanding | 8,664 | 8,454
International Finance [Member] | Asset Backed and Other [Member] |  |
Guarantor Obligations [Line Items] |  |
Net Par Amount Outstanding | 862 | 1,083
International Finance [Member] | Investor-owned and Public Utilities [Member] |  |
Guarantor Obligations [Line Items] |  |
Net Par Amount Outstanding | 2,855 | 2,583
International Finance [Member] | Sovereign/Sub-sovereign [Member] |  |
Guarantor Obligations [Line Items] |  |
Net Par Amount Outstanding | 4,221 | 4,077
International Finance [Member] | Transportation [Member] |  |
Guarantor Obligations [Line Items] |  |
Net Par Amount Outstanding | $ 726 | $ 711

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