Investments - Investments by Category (Details) - USD ($) $ in Millions	Jun. 30, 2025	Dec. 31, 2024
Schedule of Investments [Line Items]
Current investments	$ 813	$ 665
Long-term investments	15,662	15,128
Total investments	16,475	$ 15,793
Debt securities
Schedule of Investments [Line Items]
Current investments	443
Long-term investments	7,946
Total investments	8,389
Equity securities
Schedule of Investments [Line Items]
Current investments	15
Long-term investments	561
Total investments	576
Commercial mortgage loans
Schedule of Investments [Line Items]
Current investments	105
Long-term investments	1,206
Total investments	1,311
Policy loans
Schedule of Investments [Line Items]
Current investments	0
Long-term investments	1,117
Total investments	1,117
Other long-term investments
Schedule of Investments [Line Items]
Current investments	0
Long-term investments	4,832
Total investments	4,832
Short-term investments
Schedule of Investments [Line Items]
Current investments	250
Long-term investments	0
Total investments	$ 250