Investments - Summary of Amounts Included in Net Realized (Losses) Gains and Other-Than-Temporary Impairments (Details) - USD ($) $ in Millions |
3 Months Ended | 6 Months Ended | |||
|---|---|---|---|---|---|
Jun. 30, 2024 |
Jun. 30, 2023 |
Jun. 30, 2024 |
Jun. 30, 2023 |
Dec. 31, 2023 |
|
| Investment [Line Items] | |||||
| Foreign exchange (losses) gains | $ (1) | $ (3) | |||
| Debt Securities, Available-for-sale, Allowance for Credit Loss, Not to Sell before Recovery, Credit Loss, Previously Recorded, Expense (Reversal) | $ (2) | $ 0 | (1) | (1) | |
| Debt Securities, Available-for-sale, Allowance for Credit Loss, Sell before Recovery | 0 | 0 | 0 | 0 | |
| Realized Investment Gains (Losses) | 4 | (3) | 4 | (8) | |
| Fair Value of Securities Deposited in Connection wtih Letter of Credit | 1 | 1 | $ 1 | ||
| Debt Securities, Available-for-sale, Realized Gain | 7 | 0 | 7 | 1 | |
| Debt Securities, Available-for-sale, Realized Loss | 1 | 2 | 1 | 3 | |
| Available-for-sale Securities, Gross Realized Losses | (1) | (2) | (1) | (3) | |
| Gain (Loss) on Investments [Member] | |||||
| Investment [Line Items] | |||||
| Foreign exchange (losses) gains | $ (1) | $ (2) | $ 0 | $ (4) | |