Supplementary Information for Oil and Gas Producing Activities - Capitalized Costs Relating to Oil and Gas Producing Activities (Details) - USD ($) $ in Thousands		Sep. 30, 2023	Sep. 30, 2022
Supplementary Information for Oil and Gas Producing Activities Unaudited [Abstract]
Proved Properties	[1]	$ 6,555,088	$ 5,915,807
Unproved Properties		161,097	65,994
Capitalized costs relating to oil and gas producing activities, gross		6,716,185	5,981,801
Less — Accumulated Depreciation, Depletion and Amortization		4,269,959	4,034,266
Capitalized costs relating to oil and gas producing activities, net		2,446,226	1,947,535
Asset retirement costs		$ 129,200	$ 120,800

[1] Includes asset retirement costs of $129.2 million and $120.8 million at September 30, 2023 and 2022, respectively.