Other Insurance Liabilities and Separate Accounts - Undiscounted Expected Gross Premiums and Expected Future Benefit Payments (Details) - USD ($) $ in Millions	Sep. 30, 2024	Sep. 30, 2023
Large Case Pensions
Liability for Future Policy Benefit, Activity [Line Items]
Expected future benefit payments	$ 3,091	$ 3,337
Expected gross premiums	0	0
Long-Term Care
Liability for Future Policy Benefit, Activity [Line Items]
Expected future benefit payments	3,198	3,237
Expected gross premiums	$ 402	$ 419