Supplementary Information for Exploration and Production Activities - Standardized Measure of Discounted Future Net Cash Flows Relating to Proved Oil and Gas Reserves (Details) - USD ($) $ in Thousands	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2022
Supplementary Information for Exploration and Production Activities Unaudited [Abstract]
Future Cash Inflows	$ 12,243,757	$ 8,514,126	$ 11,947,345
Less:
Future Production Costs	3,823,175	3,672,901	3,538,389
Future Development Costs	1,239,386	1,191,708	1,095,096
Future Income Tax Expense at Applicable Statutory Rate	1,719,387	826,094	1,867,457
Future Net Cash Flows	5,461,809	2,823,423	5,446,403
Less:
10% Annual Discount for Estimated Timing of Cash Flows	2,707,425	1,486,968	2,874,295
Standardized Measure of Discounted Future Net Cash Flows	$ 2,754,384	$ 1,336,455	$ 2,572,108	$ 5,448,330