Inventories (Details) - USD ($) $ in Millions	Mar. 31, 2024	Sep. 30, 2023	Mar. 31, 2023
Inventory
Total inventories	$ 375	$ 433	$ 433
Non-utility LPG and natural gas
Inventory
Total inventories	196	212	230
Gas Utility natural gas
Inventory
Total inventories	8	55	20
Energy certificates
Inventory
Total inventories	63	64	76
Materials, supplies and other
Inventory
Total inventories	$ 108	$ 102	$ 107