Other Insurance Liabilities and Separate Accounts - Undiscounted Expected Gross Premiums and Expected Future Benefit Payments (Details) - USD ($) $ in Millions	Mar. 31, 2025	Mar. 31, 2024
Large Case Pensions
Liability for Future Policy Benefit, Activity [Line Items]
Expected future benefit payments	$ 2,973	$ 3,213
Expected gross premiums	0	0
Long-Term Care
Liability for Future Policy Benefit, Activity [Line Items]
Expected future benefit payments	3,170	3,215
Expected gross premiums	$ 390	$ 411