Other Insurance Liabilities and Separate Accounts - Undiscounted Expected Gross Premiums and Expected Future Benefit Payments (Details) - USD ($) $ in Millions	Mar. 31, 2024	Mar. 31, 2023
Large Case Pensions
Liability for Future Policy Benefit, Activity [Line Items]
Expected future benefit payments	$ 3,213	$ 3,463
Expected gross premiums	0	0
Long-Term Care
Liability for Future Policy Benefit, Activity [Line Items]
Expected future benefit payments	3,215	3,246
Expected gross premiums	$ 411	$ 428