Investments - Schedule of Securities Pledged by Contractual Maturity (Details) - USD ($) $ in Millions	Mar. 31, 2026	Dec. 31, 2025
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Securities pledged under securities lending agreements	$ 183	$ 145
Total gross secured borrowings	183	145
Corporate bonds
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Securities pledged under securities lending agreements	175	130
Foreign government bonds
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Securities pledged under securities lending agreements	4	5
Equity securities
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Securities pledged under securities lending agreements	4	10
Overnight and Continuous
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Total gross secured borrowings	183	145
Overnight and Continuous | Corporate bonds
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Securities pledged under securities lending agreements	175	130
Overnight and Continuous | Foreign government bonds
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Securities pledged under securities lending agreements	4	5
Overnight and Continuous | Equity securities
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Securities pledged under securities lending agreements	4	10
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 | Foreign government 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 | 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 | Foreign government bonds
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Securities pledged under securities lending agreements	0	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 | Foreign government 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 | Equity securities
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Securities pledged under securities lending agreements	$ 0	$ 0