Commitments and Contingencies - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023
Loss Contingencies [Line Items]
Loss Contingency, Range of Possible Loss, Portion Not Accrued	$ 0
Loss Contingency, Undiscounted Amount of Insurance-related Assessment Liability	2	$ 0
Loss Contingency Accrual, Insurance-related Assessment, Premium Tax Offset	18	8
Securities Loaned
Loss Contingencies [Line Items]
Securities Owned and Pledged as Collateral	133	153
Loan Purchase Commitments
Loss Contingencies [Line Items]
Long-term Purchase Commitment, Amount	189
Investment Purchase Commitment
Loss Contingencies [Line Items]
Long-term Purchase Commitment, Amount	1,149
Federal Home Loan Bank of Boston | Line of Credit
Loss Contingencies [Line Items]
Line of Credit Facility, Fair Value of Amount Outstanding	$ 721	$ 671