Investments - Debt Securities by Contractual Maturity Periods (Details) $ in Millions	Mar. 31, 2025 USD ($)
Amortized Cost
Due in one year or less	$ 622
Due after one year through five years	3,334
Due after five years through ten years	2,388
Due after ten years	2,036
Mortgage and other asset-backed securities	357
Total	8,737
Fair Value
Due in one year or less	555
Due after one year through five years	3,224
Due after five years through ten years	2,270
Due after ten years	1,837
Mortgage and other asset-backed securities	329
Total	$ 8,215