Investments - Schedule of Securities Pledged by Contractual Maturity (Details) - USD ($) $ in Millions	Mar. 31, 2025	Dec. 31, 2024
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Securities pledged under securities lending agreements	$ 167	$ 157
Total gross secured borrowings	167	157
Corporate bonds
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Securities pledged under securities lending agreements	157	144
U.S. government bonds
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Securities pledged under securities lending agreements		1
Equity securities
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Securities pledged under securities lending agreements	10	12
Overnight and Continuous
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Total gross secured borrowings	167	157
Overnight and Continuous | Corporate bonds
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Securities pledged under securities lending agreements	157	144
Overnight and Continuous | U.S. government bonds
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Securities pledged under securities lending agreements		1
Overnight and Continuous | Equity securities
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Securities pledged under securities lending agreements	10	12
Up to 30 Days
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Total gross secured borrowings	0	0
Up to 30 Days | Corporate bonds
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Securities pledged under securities lending agreements	0	0
Up to 30 Days | U.S. government bonds
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Securities pledged under securities lending agreements		0
Up to 30 Days | Equity securities
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Securities pledged under securities lending agreements	0	0
30-90 Days
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Total gross secured borrowings	0	0
30-90 Days | Corporate bonds
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Securities pledged under securities lending agreements	0	0
30-90 Days | U.S. government bonds
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Securities pledged under securities lending agreements		0
30-90 Days | Equity securities
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Securities pledged under securities lending agreements	0	0
Greater Than 90 Days
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Total gross secured borrowings	0	0
Greater Than 90 Days | Corporate bonds
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Securities pledged under securities lending agreements	0	0
Greater Than 90 Days | U.S. government bonds
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Securities pledged under securities lending agreements		0
Greater Than 90 Days | Equity securities
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Securities pledged under securities lending agreements	$ 0	$ 0