Supplementary Information On Natural Gas, Oil And NGL Reserves (Summary of Proved Undeveloped Reserves) (Details) - 12 months ended Sep. 30, 2020	Bcfe	Mcfe
Extractive Industries [Abstract]
Beginning proved undeveloped reserves	17.0	17,018,905
Proved undeveloped reserves transferred to proved developed	(0.4)	(399,894)
Revisions		(16,767,540)
Extensions and discoveries		2,405,590
Sales		(479,415)
Purchases		1,283,010
Ending proved undeveloped reserves		3,060,656