Inventories (Details) - USD ($) $ in Millions	Sep. 30, 2024	Sep. 30, 2023
Public Utilities, Inventory
Total inventories	$ 411	$ 433
Non-utility LPG and natural gas
Public Utilities, Inventory
Total inventories	195	212
Gas Utility natural gas
Public Utilities, Inventory
Total inventories	50	55
Energy certificates
Public Utilities, Inventory
Total inventories	69	64
Materials, supplies and other
Public Utilities, Inventory
Total inventories	$ 97	$ 102