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Fair Value of Financial Instruments (Quantitative Information Regarding The Significant Unobservable Inputs For Certain Assets And Liabilities Measured At Fair Value On A Recurring Basis) (Detail) - USD ($) $ in Millions | Mar. 31, 2025 | Dec. 31, 2024
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Discounted Cash Flow [Member] | Loans Carried at Fair Value [Member] | Discount Rate [Member] |  |  |  |
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items] |  |  |  |
Fair Value, assets | $ 14 | [1] | $ 15 | [2]
Discounted Cash Flow Type Certificate [Member] | Equity Investments [Member] | Discount Rate EBITDA Multiple EBITDA Royalty Share [Member] |  |  |  |
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items] |  |  |  |
Fair Value, assets | 52 | [1] | 52 | [2]
Variable Interest Entity Primary Beneficiary [Member] | Loans Receivable and Other Instruments at Fair Value [Member] | Impact Of Financial Guarantee [Member] | Market Prices of Similar Liabilities Adjusted for Financial Guarantees Provided to VIE Obligations [Member] |  |  |  |
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items] |  |  |  |
Fair Value, assets | $ 30 |  | $ 28 |
Variable Interest Entity Primary Beneficiary [Member] | Minimum [Member] | Loans Receivable and Other Instruments at Fair Value [Member] | Impact Of Financial Guarantee [Member] | Market Prices of Similar Liabilities Adjusted for Financial Guarantees Provided to VIE Obligations [Member] |  |  |  |
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items] |  |  |  |
Range percentage | 7.00% | [3] | 27.00% | [4]
Variable Interest Entity Primary Beneficiary [Member] | Maximum [Member] | Loans Receivable and Other Instruments at Fair Value [Member] | Impact Of Financial Guarantee [Member] | Market Prices of Similar Liabilities Adjusted for Financial Guarantees Provided to VIE Obligations [Member] |  |  |  |
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items] |  |  |  |
Range percentage | 7.00% | [3] | 27.00% | [4]
Variable Interest Entity Primary Beneficiary [Member] | Weighted Average [Member] | Loans Receivable and Other Instruments at Fair Value [Member] | Impact Of Financial Guarantee [Member] | Market Prices of Similar Liabilities Adjusted for Financial Guarantees Provided to VIE Obligations [Member] |  |  |  |
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items] |  |  |  |
Range percentage | 7.00% | [3] | 27.00% | [4]
[1] | Ranges for discount rate, EBITDA multiple and EBITDA royalty share are not meaningful.
[2] | Ranges for discount rate, EBITDA multiples, EBITDA royalty share are not meaningful.
[3] | Weighted average represents the total MBIA guarantees as a percentage of total instrument fair value.
[4] | Weighted average represents the total MBIA guarantees as a percentage of total instrument fair value.

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