Supplementary Information On Natural Gas, Oil And NGL Reserves (Summary of Net Quantities of Proved, Developed and Undeveloped Natural Gas Oil and NGL Reserves) (Details)	12 Months Ended
	Sep. 30, 2021 Bcfe bbl Mcf	Sep. 30, 2020 Bcfe bbl Mcf	Sep. 30, 2019 Bcfe bbl Mcf
Reserve Quantities [Line Items]
Proved Natural Gas and Oil Reserves, Beginning Balance | Bcfe	57.7	106.4	173.6
Revisions of previous estimates | Bcfe	26.0	(45.9)	(60.6)
Acquisitions (divestitures) | Bcfe	7.7	1.7	(3.0)
Extensions, discoveries and other additions | Bcfe	0.7	4.1	6.8
Production | Bcfe	(9.1)	(8.6)	(10.4)
Proved Natural Gas and Oil Reserves, Ending Balance | Bcfe	83.0	57.7	106.4
Natural Gas [Member]
Reserve Quantities [Line Items]
Proved Natural Gas and Oil Reserves, Beginning Balance | Mcf	42,372,773	80,273,906	120,062,036
Revisions of previous estimates | Mcf	21,930,522	(34,666,426)	(35,644,135)
Acquisitions (divestitures) | Mcf	6,994,423	911,853	(948,496)
Extensions, discoveries and other additions | Mcf	354,670	1,816,144	3,891,262
Production | Mcf	(6,699,720)	(5,962,704)	(7,086,761)
Proved Natural Gas and Oil Reserves, Ending Balance | Mcf	64,952,668	42,372,773	80,273,906
Oil [Member]
Reserve Quantities [Line Items]
Proved Natural Gas and Oil Reserves, Beginning Balance	1,333,657	2,380,090	5,984,422
Revisions of previous estimates	287,961	(1,094,923)	(3,266,351)
Acquisitions (divestitures)	79,576	57,721	(322,023)
Extensions, discoveries and other additions	28,125	260,555	313,241
Production	(224,479)	(269,786)	(329,199)
Proved Natural Gas and Oil Reserves, Ending Balance	1,504,840	1,333,657	2,380,090
NGL [Member]
Reserve Quantities [Line Items]
Proved Natural Gas and Oil Reserves, Beginning Balance	1,219,857	1,973,280	2,934,190
Revisions of previous estimates	389,825	(774,214)	(890,046)
Acquisitions (divestitures)	36,911	70,933	(18,881)
Extensions, discoveries and other additions	26,748	118,480	164,276
Production	(171,488)	(168,622)	(216,259)
Proved Natural Gas and Oil Reserves, Ending Balance	1,501,853	1,219,857	1,973,280