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Investments - Schedule of Payment Status of Mortgage Loans (Details) - Mortgage loans - USD ($) $ in Millions	Sep. 30, 2025	Dec. 31, 2024
Debt Securities, Available-for-Sale [Line Items]
Amortized cost before allowance	$ 849
Allowance	(18)
Total mortgage loans	831
Commercial
Debt Securities, Available-for-Sale [Line Items]
Amortized cost before allowance	697	$ 735
Allowance	(17)
Total mortgage loans	680
Residential
Debt Securities, Available-for-Sale [Line Items]
Amortized cost before allowance	152
Allowance	(1)
Total mortgage loans	151
Less than 90 days past due
Debt Securities, Available-for-Sale [Line Items]
Amortized cost before allowance	24
Less than 90 days past due \| Commercial
Debt Securities, Available-for-Sale [Line Items]
Amortized cost before allowance	23
Less than 90 days past due \| Residential
Debt Securities, Available-for-Sale [Line Items]
Amortized cost before allowance	1
90 days or greater past due
Debt Securities, Available-for-Sale [Line Items]
Amortized cost before allowance	0
90 days or greater past due \| Commercial
Debt Securities, Available-for-Sale [Line Items]
Amortized cost before allowance	0
90 days or greater past due \| Residential
Debt Securities, Available-for-Sale [Line Items]
Amortized cost before allowance	0
Total past due before allowance
Debt Securities, Available-for-Sale [Line Items]
Amortized cost before allowance	24
Total past due before allowance \| Commercial
Debt Securities, Available-for-Sale [Line Items]
Amortized cost before allowance	23
Total past due before allowance \| Residential
Debt Securities, Available-for-Sale [Line Items]
Amortized cost before allowance	1
Current before allowance
Debt Securities, Available-for-Sale [Line Items]
Amortized cost before allowance	825
Current before allowance \| Commercial
Debt Securities, Available-for-Sale [Line Items]
Amortized cost before allowance	674
Current before allowance \| Residential
Debt Securities, Available-for-Sale [Line Items]
Amortized cost before allowance	$ 151