Investments - Narrative (Details) - USD ($) $ in Millions	Sep. 30, 2025	Dec. 31, 2024
Debt Securities, Available-for-Sale [Line Items]
Mortgage loans, net	$ 831	$ 784
Short-term investments	8,743	4,537
Accrued investment income	617	615
Residential
Debt Securities, Available-for-Sale [Line Items]
Mortgage loans, net	151	61
Fixed income securities
Debt Securities, Available-for-Sale [Line Items]
Accrued investment income	$ 561	$ 574