Investments - Aggregate Contractual or Notional Amounts and Estimated Fair Values Related to Derivative Financial Instruments (Details) - Without hedge designation - USD ($) $ in Millions	Dec. 31, 2024	Dec. 31, 2023
Futures | Options - purchased
Gross Estimated Fair Values of Derivative Positions [Abstract]
Contractual/Notional Amount	$ 268	$ 202
Estimated Fair Value, Asset	2	1
Estimated Fair Value, Liability
Futures | Futures - short
Gross Estimated Fair Values of Derivative Positions [Abstract]
Contractual/Notional Amount	167	116
Estimated Fair Value, Asset	1
Estimated Fair Value, Liability
Warrants
Gross Estimated Fair Values of Derivative Positions [Abstract]
Contractual/Notional Amount	1	84
Estimated Fair Value, Asset	1	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	4	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)
Credit default swap index - purchased
Gross Estimated Fair Values of Derivative Positions [Abstract]
Contractual/Notional Amount	2,000
Estimated Fair Value, Asset
Estimated Fair Value, Liability