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Investments - Summary of Net Investment Income (Detail) - USD ($) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2023 | Dec. 31, 2022 | Dec. 31, 2021
Investment [Line Items] |  |  |
Trading Securities, Realized Gain (Loss) | $ 18 | $ (26) | $ 1
Investment expense | (6) | (6) | (6)
Interest Income, Debt Securities, Available-for-Sale, Operating | 93 | 66 | 74
Net investment income | 140 | 17 | 139
Fixed income securities |  | 61 | 78
Gains (losses) on securities held as of reporting date [Member] |  |  |
Investment [Line Items] |  |  |
Other Investments Income | 7 | (22) | 22
Available-for-sale Securities [Member] |  |  |
Investment [Line Items] |  |  |
Fixed income securities | 76 |  |
Short-term Investments [Member] |  |  |
Investment [Line Items] |  |  |
Fixed income securities | 22 | 11 | 0
Financing Receivable [Member] |  |  |
Investment [Line Items] |  |  |
Fixed income securities | 0 | 1 | 0
Other Investments [Member] |  |  |
Investment [Line Items] |  |  |
Fixed income securities | 40 | (26) | 66
Debt Securities, Trading |  |  |
Investment [Line Items] |  |  |
Fixed income securities | $ 7 | $ (23) | $ 0

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