Investments and Cash - Net Realized Investment Gains (Losses) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Investments, Debt and Equity Securities [Abstract]
Gross realized gains on sales of available-for-sale securities	$ 21	$ 3	$ 20
Gross realized losses on sales available-for-sale securities	(19)	(45)	(5)
Net foreign currency gains (losses)	(1)	(4)	2
Change in credit impairment and intent to sell	(14)	(21)	(7)
Other net realized gains (losses)	(1)	11	5
Net realized investment gains (losses)	$ (14)	$ (56)	$ 15