Investments - Investments by Category (Details) - USD ($) $ in Millions	Mar. 31, 2025	Dec. 31, 2024
Schedule of Investments [Line Items]
Current investments	$ 727	$ 665
Long-term investments	15,350	15,128
Total investments	16,077	$ 15,793
Debt securities
Schedule of Investments [Line Items]
Current investments	454
Long-term investments	7,761
Total investments	8,215
Equity securities
Schedule of Investments [Line Items]
Current investments	11
Long-term investments	548
Total investments	559
Commercial mortgage loans
Schedule of Investments [Line Items]
Current investments	66
Long-term investments	1,228
Total investments	1,294
Policy loans
Schedule of Investments [Line Items]
Current investments	0
Long-term investments	1,128
Total investments	1,128
Other long-term investments
Schedule of Investments [Line Items]
Current investments	0
Long-term investments	4,685
Total investments	4,685
Short-term investments
Schedule of Investments [Line Items]
Current investments	196
Long-term investments	0
Total investments	$ 196