Property, Plant and Equipment - Schedule of Property, Plant and Equipment (Details) - USD ($) $ in Millions	12 Months Ended
Sep. 30, 2021	Sep. 30, 2020
Property, Plant and Equipment
Utility	$ 5,022	$ 4,265
Non-utility	6,486	6,393
Total property, plant and equipment	11,508	10,658
Distribution
Property, Plant and Equipment
Utility	4,306	3,630
Transmission
Property, Plant and Equipment
Utility	111	111
General and other
Property, Plant and Equipment
Utility	507	425
Work in process
Property, Plant and Equipment
Utility	98	99
Non-utility	76	196
Land
Property, Plant and Equipment
Non-utility	186	191
Buildings and improvements
Property, Plant and Equipment
Non-utility	$ 436	431
Buildings and improvements \| Minimum
Property, Plant and Equipment
Estimated Useful Life	10 years
Buildings and improvements \| Maximum
Property, Plant and Equipment
Estimated Useful Life	40 years
Transportation equipment
Property, Plant and Equipment
Non-utility	$ 232	248
Transportation equipment \| Minimum
Property, Plant and Equipment
Estimated Useful Life	3 years
Transportation equipment \| Maximum
Property, Plant and Equipment
Estimated Useful Life	10 years
Equipment, primarily cylinders and tanks
Property, Plant and Equipment
Non-utility	$ 3,785	3,712
Equipment, primarily cylinders and tanks \| Minimum
Property, Plant and Equipment
Estimated Useful Life	5 years
Equipment, primarily cylinders and tanks \| Maximum
Property, Plant and Equipment
Estimated Useful Life	30 years
Electric generation
Property, Plant and Equipment
Non-utility	$ 211	211
Electric generation \| Minimum
Property, Plant and Equipment
Estimated Useful Life	25 years
Electric generation \| Maximum
Property, Plant and Equipment
Estimated Useful Life	40 years
Pipeline and related assets
Property, Plant and Equipment
Non-utility	$ 1,218	1,098
Pipeline and related assets \| Minimum
Property, Plant and Equipment
Estimated Useful Life	25 years
Pipeline and related assets \| Maximum
Property, Plant and Equipment
Estimated Useful Life	40 years
Other
Property, Plant and Equipment
Non-utility	$ 342	$ 306
Other \| Minimum
Property, Plant and Equipment
Estimated Useful Life	1 year
Other \| Maximum
Property, Plant and Equipment
Estimated Useful Life	12 years

Amount, before accumulated depreciation and amortization, of property, plant, and equipment and finance lease right-of-use asset.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 360
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=6391035&loc=d3e2868-110229

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(13))
-URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 842
-SubTopic 20
-Section 45
-Paragraph 1
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=123391704&loc=SL77918627-209977

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