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Investments and Cash - Net Investment Income (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Net Investment Income
Gross investment income	$ 345	$ 370	$ 274
Investment expenses	(5)	(5)	(5)
Net investment income	340	365	269
Fair value gains (losses) on trading securities	52	74	(34)
Equity in earnings (losses) of investees	62	28	(39)
Fair value of gain (loss) on trading securities still held	$ 15	31	(29)
Fair Value, Asset (Liability), Recurring Basis, Still Held, Unrealized Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	Fair value gains (losses) on trading securities
Fixed-maturity securities. available-for-sale
Net Investment Income
Gross investment income	$ 261	294	258
Short-term investments
Net Investment Income
Gross investment income	83	73	15
Other
Net Investment Income
Gross investment income	1	3	1
Sound Point
Net Investment Income
Equity in earnings (losses) of investees	6	5	0
Equity Funds
Net Investment Income
Equity in earnings (losses) of investees	56	23	(39)
Loss mitigation securities
Net Investment Income
Gross investment income	$ 28	$ 55	$ 31

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Amount of unrealized gain (loss) on investment in debt security measured at fair value with change in fair value recognized in net income (trading).

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