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Investments - Summary of Net Investment Income (Detail) - USD ($) $ in Millions | 12 Months Ended
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Dec. 31, 2022 | Dec. 31, 2021 | Dec. 31, 2020
Investment [Line Items] |  |  |
Net Realized and Unrealized Gain (Loss) on Trading Securities | $ (48) | $ 23 | $ 0
Trading Securities, Realized Gain (Loss) | (26) | 1 | (18)
Fixed income securities |  | 78 | 103
Investment expense | (6) | (6) | (6)
Securities available-for-sale and short-term | 66 | 74 | 103
Net investment income | 17 | 139 | 122
Gains (losses) on securities held as of reporting date [Member] |  |  |
Investment [Line Items] |  |  |
Other Investments Income | (22) | 22 | 18
Available-for-sale Securities [Member] |  |  |
Investment [Line Items] |  |  |
Fixed income securities | 61 |  |
Short-term Investments [Member] |  |  |
Investment [Line Items] |  |  |
Fixed income securities | 11 | 0 | 5
Financing Receivable [Member] |  |  |
Investment [Line Items] |  |  |
Fixed income securities | 1 | 0 | 1
Other Investments [Member] |  |  |
Investment [Line Items] |  |  |
Fixed income securities | (26) | $ 66 | $ 19
Debt Securities, Trading |  |  |
Investment [Line Items] |  |  |
Fixed income securities | $ (23) |  |

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