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Investments Investments - Equity Investments (Details) - USD ($) $ in Millions | 3 Months Ended | 9 Months Ended |
--- | --- | --- | ---
Sep. 30, 2024 | Sep. 30, 2023 | Sep. 30, 2024 | Sep. 30, 2023 | Dec. 31, 2023
Schedule of Equity Method Investments [Line Items] |  |  |  |  |
Equity Securities Excluded From Fair Value Table | $ 26 |  | $ 26 |  | $ 13
Equity Securities, FV-NI, Realized Gain (Loss) | 1 | $ 0 |  |  |
Debt Securities, Available-for-sale, Allowance for Credit Loss | 1 | 2 | 1 | $ 2 | 3
Net Realized and Unrealized Gain (Loss) on Trading Securities |  | $ 0 |  |  |
Debt Securities, Trading, Realized Gain (Loss) | 10 |  |  |  |
Other than Temporary Impairment Losses, Investments |  |  | 1 |  |
Real Estate [Member] |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |
Other investments |  |  |  |  | 21
Hedge Funds, Multi-strategy [Member] |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |
Other investments | 87 |  | 87 |  | 112
Illiquid Investments [Member] |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |
Other investments | 84 |  | 84 |  | 84
Insurance Linked [Member] |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |
Other investments | 0 |  | 0 |  | 1
Private Equity Funds [Member] |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |
Other investments | 81 |  | 81 |  | 70
Equity investments in pooled funds [Member] |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |
Other investments | 535 |  | 535 |  | 463
Convertibles and Bonds with Warrants Attached |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |
Other investments | 26 |  | 26 |  | 0
Fixed Income Funds |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |
Other investments | 57 |  | 57 |  | 52
Equity Funds |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |
Other investments | 67 |  | 67 |  | 38
Real Estate Funds |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |
Other investments | 0 |  | 0 |  |
High Yield Fund |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |
Other investments | 134 |  | 134 |  | 85
Priced Through Pricing Vendors [Member] |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |
Other investments | 174 |  | 174 |  | 77
Priced Through Pricing Vendors [Member] | Interest Rate Contract [Member] |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |
Other investments | 82 |  | 82 |  | 39
Priced Through Pricing Vendors [Member] | Equity [Member] |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |
Other investments | 67 |  | 67 |  | 38
Priced Through Pricing Vendors [Member] | Convertibles and Bonds with Warrants Attached |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |
Other investments | 26 |  | 26 |  | $ 0
Gains (losses) on securities held as of reporting date [Member] |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |
Equity Securities, FV-NI, Realized Gain (Loss) |  |  | 8 | 10 |
Net Realized and Unrealized Gain (Loss) on Trading Securities |  |  | 23 | $ 16 |
Commitments [Member] | Private Equity Funds [Member] |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |
Other investments | $ 26 |  | $ 26 |  |

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