Investments - Aggregate Contractual or Notional Amounts and Estimated Fair Values Related to Derivative Financial Instruments (Details) - Without Hedge Designation - USD ($) $ in Millions	Mar. 31, 2024	Dec. 31, 2023
Futures | Options – purchased
Gross Estimated Fair Values of Derivative Positions [Abstract]
Contractual/Notional Amount	$ 235	$ 202
Estimated Fair Value, Asset	1	1
Estimated Fair Value, Liability
Futures | Futures – short
Gross Estimated Fair Values of Derivative Positions [Abstract]
Contractual/Notional Amount	127	116
Estimated Fair Value, Asset
Estimated Fair Value, Liability
Warrants
Gross Estimated Fair Values of Derivative Positions [Abstract]
Contractual/Notional Amount	84	84
Estimated Fair Value, Asset	3	3
Estimated Fair Value, Liability
Interest rate swaps
Gross Estimated Fair Values of Derivative Positions [Abstract]
Contractual/Notional Amount	300	300
Estimated Fair Value, Asset	12	13
Estimated Fair Value, Liability
Currency forwards
Gross Estimated Fair Values of Derivative Positions [Abstract]
Contractual/Notional Amount		13
Estimated Fair Value, Asset
Estimated Fair Value, Liability		$ (1)