Supplementary Information On Oil, NGL And Natural Gas Reserves (Summary of Proved Undeveloped Reserves) (Details)	12 Months Ended
	Sep. 30, 2018 Mcfe
Extractive Industries [Abstract]
Beginning proved undeveloped reserves	56,880,555
Proved undeveloped reserves transferred to proved developed	(2,158,716)
Revisions	(12,456,931)
Extensions and discoveries	20,413,545
Purchases	1,221,543
Ending proved undeveloped reserves	63,899,996