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Variable Interest Entities (Summary of Nonconsolidated VIEs Assets and Liabilities) (Detail) - USD ($) $ in Millions | Mar. 31, 2024 | Dec. 31, 2023
--- | --- | ---
Variable Interest Entity [Line Items] |  |
Maximum Exposure to Loss | $ 1,550 | $ 1,594
Carrying Value of VIE Assets | 2,488 | 2,606
Carrying Value of VIE Liabilities | 4,211 | 4,253
Investments [Member] |  |
Variable Interest Entity [Line Items] |  |
Carrying Value of VIE Assets | 19 | 19
Premiums Receivable [Member] |  |
Variable Interest Entity [Line Items] |  |
Carrying Value of VIE Assets | 11 | 11
Insurance Loss Recoverable [Member] |  |
Variable Interest Entity [Line Items] |  |
Carrying Value of VIE Assets | 29 | 31
Unearned Premium Revenue [Member] |  |
Variable Interest Entity [Line Items] |  |
Carrying Value of VIE Liabilities | 9 | 10
Loss And Loss Adjustment Expense Reserves [Member] |  |
Variable Interest Entity [Line Items] |  |
Carrying Value of VIE Liabilities | 235 | 242
Global Structured Finance [Member] |  |
Variable Interest Entity [Line Items] |  |
Maximum Exposure to Loss | 1,340 | 1,376
Global Structured Finance [Member] | Investments [Member] |  |
Variable Interest Entity [Line Items] |  |
Carrying Value of VIE Assets | 19 | 19
Global Structured Finance [Member] | Premiums Receivable [Member] |  |
Variable Interest Entity [Line Items] |  |
Carrying Value of VIE Assets | 7 | 7
Global Structured Finance [Member] | Insurance Loss Recoverable [Member] |  |
Variable Interest Entity [Line Items] |  |
Carrying Value of VIE Assets | 29 | 31
Global Structured Finance [Member] | Unearned Premium Revenue [Member] |  |
Variable Interest Entity [Line Items] |  |
Carrying Value of VIE Liabilities | 6 | 6
Global Structured Finance [Member] | Loss And Loss Adjustment Expense Reserves [Member] |  |
Variable Interest Entity [Line Items] |  |
Carrying Value of VIE Liabilities | 235 | 242
Global Structured Finance [Member] | Residential Mortgage Backed Securities [Member] |  |
Variable Interest Entity [Line Items] |  |
Maximum Exposure to Loss | 838 | 853
Global Structured Finance [Member] | Residential Mortgage Backed Securities [Member] | Investments [Member] |  |
Variable Interest Entity [Line Items] |  |
Carrying Value of VIE Assets | 19 | 19
Global Structured Finance [Member] | Residential Mortgage Backed Securities [Member] | Premiums Receivable [Member] |  |
Variable Interest Entity [Line Items] |  |
Carrying Value of VIE Assets | 5 | 5
Global Structured Finance [Member] | Residential Mortgage Backed Securities [Member] | Insurance Loss Recoverable [Member] |  |
Variable Interest Entity [Line Items] |  |
Carrying Value of VIE Assets | 21 | 23
Global Structured Finance [Member] | Residential Mortgage Backed Securities [Member] | Unearned Premium Revenue [Member] |  |
Variable Interest Entity [Line Items] |  |
Carrying Value of VIE Liabilities | 3 | 3
Global Structured Finance [Member] | Residential Mortgage Backed Securities [Member] | Loss And Loss Adjustment Expense Reserves [Member] |  |
Variable Interest Entity [Line Items] |  |
Carrying Value of VIE Liabilities | 232 | 239
Global Structured Finance [Member] | Consumer Asset Backed [Member] |  |
Variable Interest Entity [Line Items] |  |
Maximum Exposure to Loss | 111 | 121
Global Structured Finance [Member] | Consumer Asset Backed [Member] | Investments [Member] |  |
Variable Interest Entity [Line Items] |  |
Carrying Value of VIE Assets | 0 | 0
Global Structured Finance [Member] | Consumer Asset Backed [Member] | Premiums Receivable [Member] |  |
Variable Interest Entity [Line Items] |  |
Carrying Value of VIE Assets | 0 | 0
Global Structured Finance [Member] | Consumer Asset Backed [Member] | Insurance Loss Recoverable [Member] |  |
Variable Interest Entity [Line Items] |  |
Carrying Value of VIE Assets | 1 | 1
Global Structured Finance [Member] | Consumer Asset Backed [Member] | Unearned Premium Revenue [Member] |  |
Variable Interest Entity [Line Items] |  |
Carrying Value of VIE Liabilities | 0 | 0
Global Structured Finance [Member] | Consumer Asset Backed [Member] | Loss And Loss Adjustment Expense Reserves [Member] |  |
Variable Interest Entity [Line Items] |  |
Carrying Value of VIE Liabilities | 3 | 3
Global Structured Finance [Member] | Corporate Asset Backed [Member] |  |
Variable Interest Entity [Line Items] |  |
Maximum Exposure to Loss | 391 | 402
Global Structured Finance [Member] | Corporate Asset Backed [Member] | Investments [Member] |  |
Variable Interest Entity [Line Items] |  |
Carrying Value of VIE Assets | 0 | 0
Global Structured Finance [Member] | Corporate Asset Backed [Member] | Premiums Receivable [Member] |  |
Variable Interest Entity [Line Items] |  |
Carrying Value of VIE Assets | 2 | 2
Global Structured Finance [Member] | Corporate Asset Backed [Member] | Insurance Loss Recoverable [Member] |  |
Variable Interest Entity [Line Items] |  |
Carrying Value of VIE Assets | 7 | 7
Global Structured Finance [Member] | Corporate Asset Backed [Member] | Unearned Premium Revenue [Member] |  |
Variable Interest Entity [Line Items] |  |
Carrying Value of VIE Liabilities | 3 | 3
Global Structured Finance [Member] | Corporate Asset Backed [Member] | Loss And Loss Adjustment Expense Reserves [Member] |  |
Variable Interest Entity [Line Items] |  |
Carrying Value of VIE Liabilities | 0 | 0
Global Public Finance [Member] |  |
Variable Interest Entity [Line Items] |  |
Maximum Exposure to Loss | 210 | 218
Global Public Finance [Member] | Investments [Member] |  |
Variable Interest Entity [Line Items] |  |
Carrying Value of VIE Assets | 0 | 0
Global Public Finance [Member] | Premiums Receivable [Member] |  |
Variable Interest Entity [Line Items] |  |
Carrying Value of VIE Assets | 4 | 4
Global Public Finance [Member] | Insurance Loss Recoverable [Member] |  |
Variable Interest Entity [Line Items] |  |
Carrying Value of VIE Assets | 0 | 0
Global Public Finance [Member] | Unearned Premium Revenue [Member] |  |
Variable Interest Entity [Line Items] |  |
Carrying Value of VIE Liabilities | 3 | 4
Global Public Finance [Member] | Loss And Loss Adjustment Expense Reserves [Member] |  |
Variable Interest Entity [Line Items] |  |
Carrying Value of VIE Liabilities | $ 0 | $ 0

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