AmeriGas Merger, Acquisitions and Dispositions - Components of the Preliminary Mountaineer Purchase Price Allocation (Details) - USD ($) $ in Millions	Sep. 30, 2021	Sep. 01, 2021	Sep. 30, 2020	Sep. 30, 2019
Liabilities assumed:
Goodwill	$ 3,770		$ 3,518	$ 3,456
Mountaineer
Assets acquired:
Cash and cash equivalents		$ 3
Accounts receivable		14
Inventories		41
Other current assets		21
Property, plant and equipment		397
Other noncurrent assets		48
Total assets acquired		524
Liabilities assumed:
Short-term borrowings		55
Accounts payable		20
Other current liabilities		52
Long-term debt		164
Pension and other postretirement benefit obligation		33
Deferred income taxes		26
Other noncurrent liabilities		29
Total liabilities assumed		379
Goodwill		255
Net consideration transferred (including working capital adjustments)		$ 400