Investments and Cash - Net Realized Investment Gains (Losses) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Investments, Debt and Equity Securities [Abstract]
Gross realized gains on sales of available-for-sale securities	$ 3	$ 21	$ 3
Gross realized losses on sales available-for-sale securities	(12)	(19)	(45)
Net foreign currency gains (losses)	(2)	(1)	(4)
Change in credit impairment and intent to sell	18	(14)	(21)
Other net realized gains (losses)	2	(1)	11
Net realized investment gains (losses)	$ 9	$ (14)	$ (56)