Investments - Investments by Category (Details) - USD ($) $ in Millions	Sep. 30, 2023	Dec. 31, 2022
Schedule of Investments [Line Items]
Current investments	$ 1,046	$ 905	[1]
Long-term investments	18,974	16,288	[1]
Total investments	20,020	17,193
Debt securities
Schedule of Investments [Line Items]
Current investments	612	654
Long-term investments	8,927	9,218
Total investments	9,539	9,872
Equity securities
Schedule of Investments [Line Items]
Current investments	31	45
Long-term investments	3,345	577
Total investments	3,376	622
Commercial mortgage loans
Schedule of Investments [Line Items]
Current investments	215	67
Long-term investments	1,402	1,547
Total investments	1,617	1,614
Policy loans
Schedule of Investments [Line Items]
Current investments	0	0
Long-term investments	1,224	1,218
Total investments	1,224	1,218
Other long-term investments
Schedule of Investments [Line Items]
Current investments	0	0
Long-term investments	4,076	3,728
Total investments	4,076	3,728
Short-term investments
Schedule of Investments [Line Items]
Current investments	188	139
Long-term investments	0	0
Total investments	$ 188	$ 139

[1] Amounts have been restated to reflect the adoption of Targeted Improvements to the Accounting for Long-Duration Contracts in 2023. See Note 2 to the Consolidated Financial Statements for further information.