Inventories (Details) - USD ($) $ in Millions	Dec. 31, 2024	Sep. 30, 2024	Dec. 31, 2023
Inventory
Total inventories	$ 381	$ 411	$ 441
Non-utility LPG and natural gas
Inventory
Total inventories	184	195	217
Gas Utility natural gas
Inventory
Total inventories	42	50	46
Energy certificates
Inventory
Total inventories	59	69	71
Materials, supplies and other
Inventory
Total inventories	$ 96	$ 97	$ 107