Supplementary Information for Oil and Gas Producing Activities - Principal Sources of Change in the Standardized Measure of Discounted Future Net Cash Flows (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021
Standardized Measure of Discounted Future Net Cash Flows [Roll Forward]
Standardized Measure of Discounted Future Net Cash Flows at Beginning of Year	$ 5,448,330	$ 2,353,572	$ 1,222,470
Sales, Net of Production Costs	(767,487)	(1,572,402)	(626,132)
Net Changes in Prices, Net of Production Costs	(3,918,392)	4,132,889	1,478,995
Extensions and Discoveries	237,057	1,355,257	462,040
Changes in Estimated Future Development Costs	(222,233)	(32,160)	48,247
Purchases of Minerals in Place	34,346	0	0
Sales of Minerals in Place	0	(311,308)	0
Previously Estimated Development Costs Incurred	342,024	154,253	81,239
Net Change in Income Taxes at Applicable Statutory Rate	959,728	(1,180,349)	(415,993)
Revisions of Previous Quantity Estimates	33,192	3,316	(52,383)
Accretion of Discount and Other	425,543	545,262	155,089
Standardized Measure of Discounted Future Net Cash Flows at End of Year	$ 2,572,108	$ 5,448,330	$ 2,353,572