Investments - Summary of Amounts Included in Net Realized (Losses) Gains and Other-Than-Temporary Impairments (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022	Dec. 31, 2022
Investment [Line Items]
Foreign exchange (losses) gains			$ (2)	$ 14
Debt Securities, Available-for-sale, Allowance for Credit Loss, Not to Sell before Recovery, Credit Loss, Previously Recorded, Expense (Reversal)	$ (1)	$ 0	(2)	0
Debt Securities, Available-for-sale, Allowance for Credit Loss, Sell before Recovery	0	0	0	0
Realized Investment Gains (Losses)	1	14	(7)	31
Fair Value of Securities Deposited in Connection wtih Letter of Credit	1		1		$ 1
Debt Securities, Available-for-sale, Realized Gain	0	6
Debt Securities, Available-for-sale, Realized Loss	1	1
Gross realized gains on securities			1	29
Available-for-sale Securities, Gross Realized Losses			(4)	(17)
Net realized (losses) gains			(7)	31
Gain (Loss) on Investments [Member]
Investment [Line Items]
Foreign exchange (losses) gains	$ 2	$ 9	$ (2)	$ 20

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Amount of expense (reversal of expense) for allowance for credit loss on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), not intended to be sold and not more likely than not will be required to sell before recovery of amortized cost basis, with previously recorded allowance.

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Amount of realized gain on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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