Supplementary Information For Oil And Gas Producing Activities (Capitalized Costs Relating To Oil And Gas Producing Activities) (Details) - USD ($) $ in Thousands		Sep. 30, 2021	Sep. 30, 2020
Supplementary Information For Oil And Gas Producing Activities Unaudited [Abstract]
Proved Properties	[1]	$ 6,652,341	$ 6,238,830
Unproved Properties		103,759	148,075
Capitalized Costs, Oil and Gas Producing Activities, Gross, Total		6,756,100	6,386,905
Less - Accumulated Depreciation, Depletion and Amortization		4,881,972	4,628,765
Capitalized Costs Oil And Gas Producing Activities Net		1,874,128	1,758,140
Asset retirement costs		$ 152,800	$ 132,600

[1] Includes asset retirement costs of $152.8 million and $132.6 million at September 30, 2021 and 2020, respectively.