Inventories (Details) - USD ($) $ in Millions	Sep. 30, 2021	Sep. 30, 2020
Public Utilities, Inventory
Total inventories	$ 469	$ 241
Non-utility LPG and natural gas
Public Utilities, Inventory
Total inventories	278	164
Utility natural gas
Public Utilities, Inventory
Total inventories	68	20
Energy certificates
Public Utilities, Inventory
Total inventories	53	3
Materials, supplies and other
Public Utilities, Inventory
Total inventories	$ 70	$ 54