Inventories (Details) - USD ($) $ in Millions	Jun. 30, 2024	Sep. 30, 2023	Jun. 30, 2023
Inventory
Total inventories	$ 379	$ 433	$ 410
Non-utility LPG and natural gas
Inventory
Total inventories	186	212	189
Gas Utility natural gas
Inventory
Total inventories	29	55	37
Energy certificates
Inventory
Total inventories	60	64	68
Materials, supplies and other
Inventory
Total inventories	$ 104	$ 102	$ 116