Investments - Aggregate Contractual or Notional Amounts and Estimated Fair Values Related to Derivative Financial Instruments (Details) - Without hedge designation - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Futures | Options - purchased
Gross Estimated Fair Values of Derivative Positions [Abstract]
Contractual/Notional Amount	$ 202
Estimated Fair Value, Asset	1
Estimated Fair Value, Liability
Futures | Futures - short
Gross Estimated Fair Values of Derivative Positions [Abstract]
Contractual/Notional Amount	116	169
Estimated Fair Value, Asset
Estimated Fair Value, Liability
Warrants
Gross Estimated Fair Values of Derivative Positions [Abstract]
Contractual/Notional Amount	84	117
Estimated Fair Value, Asset	3	6
Estimated Fair Value, Liability
Interest rate swaps
Gross Estimated Fair Values of Derivative Positions [Abstract]
Contractual/Notional Amount	300	240
Estimated Fair Value, Asset	13	19
Estimated Fair Value, Liability
Currency forwards
Gross Estimated Fair Values of Derivative Positions [Abstract]
Contractual/Notional Amount	13	12
Estimated Fair Value, Asset
Estimated Fair Value, Liability	$ (1)	$ (1)