Supplementary Information for Exploration and Production Activities - Capitalized Costs Relating to Exploration and Production Activities (Details) - USD ($) $ in Thousands		Sep. 30, 2025	Sep. 30, 2024
Supplementary Information for Exploration and Production Activities Unaudited [Abstract]
Proved Properties	[1]	$ 7,719,339	$ 7,079,903
Unproved Properties		112,432	200,986
Capitalized costs relating to exploration and production activities, gross		7,831,771	7,280,889
Less — Accumulated Depreciation, Depletion and Amortization		5,374,360	5,004,299
Capitalized costs relating to exploration and production activities, net		2,457,411	2,276,590
Asset retirement costs		$ 233,900	$ 175,200

[1] Includes asset retirement costs of $233.9 million and $175.2 million at September 30, 2025 and 2024, respectively.