Supplementary Information On Oil, NGL And Natural Gas Reserves (Summary of Proved Undeveloped Reserves) (Details)	12 Months Ended
	Sep. 30, 2017 Mcfe
Extractive Industries [Abstract]
Beginning proved undeveloped reserves	42,634,659
Proved undeveloped reserves transferred to proved developed	(15,670,848)
Revisions	819,338
Extensions and discoveries	29,097,406
Ending proved undeveloped reserves	56,880,555