Supplementary Information for Exploration and Production Activities - Narrative (Details) $ in Millions, Bcf in Billions	12 Months Ended
	Sep. 30, 2024 USD ($) pUDLocation Bcf	Sep. 30, 2023 USD ($) pUDLocation Bcf	Sep. 30, 2022 USD ($) Bcf	Sep. 30, 2021	Sep. 30, 2020
Reserve Quantities [Line Items]
Amount spent for developing proved undeveloped reserves | $	$ 305.6	$ 342.0	$ 154.3
Proved undeveloped reserve volume (in Bcfe)	1,267	985	858
Percentage of PUD reserves to the total proved reserves	26.70%	21.70%	20.60%
Increase in PUD reserves (in Bcfe)	282	127
New PUD reserve additions (in Bcfe)	602	554
PUD reserves added back (in Bcfe)		14
Number of PUD wells added back | pUDLocation		1
PUD upward revisions (in Bcfe)	76	23
PUD conversions to developed reserves (in Bcfe)	291	402
Proved undeveloped reserves removed (in Bcfe)	105	62
Number of PUD well locations removed | pUDLocation	9	7
Investment made to convert proved undeveloped reserves to developed reserves | $	$ 306.0	$ 342.0
Conversion of undeveloped proved reserves to developed proved reserves after revisions (in Bcfe)	374	440
Conversion of PUD to developed to PUD reserves booked at end of prior year (as a percent)	30.00%	47.00%	45.00%	34.00%	36.00%
Arbitrary discount rate (as a percent)	10.00%
Total PUD Reserve Additions Estimated in the Next Fiscal Year
Reserve Quantities [Line Items]
Amount to be spent on developing proved undeveloped reserves | $	$ 300.0
Utica Shale
Reserve Quantities [Line Items]
Proved undeveloped reserve volume (in Bcfe)	925	873	503
PUD conversions to developed reserves (in Bcfe)		127
Marcellus Shale Fields
Reserve Quantities [Line Items]
Proved undeveloped reserve volume (in Bcfe)	342	112	355
PUD conversions to developed reserves (in Bcfe)		275
Appalachian Region
Reserve Quantities [Line Items]
Number of well locations developed with net PUD reserves | pUDLocation	20	39
Number of well locations to be developed with net PUD reserves | pUDLocation	73	77