Supplementary Information On Oil, NGL And Natural Gas Reserves (Summary of Proved Developed and Undeveloped Reserves) (Details)	Sep. 30, 2018 bbl Mcf	Sep. 30, 2017 bbl Mcf	Sep. 30, 2016 bbl Mcf
Oil [Member]
Reserve Quantities [Line Items]
Proved Developed Reserves (Volume)	2,334,587	2,201,528	1,980,519
Proved Undeveloped Reserves (Volume)	3,649,835	3,308,139	3,445,571
Natural Gas Liquids [Member]
Reserve Quantities [Line Items]
Proved Developed Reserves (Volume)	2,085,706	1,768,425	1,095,256
Proved Undeveloped Reserves (Volume)	848,484	616,274	527,447
Natural Gas [Member]
Reserve Quantities [Line Items]
Proved Developed Reserves (Volume) | Mcf	83,151,954	87,861,043	62,929,047
Proved Undeveloped Reserves (Volume) | Mcf	36,910,082	33,334,077	18,796,551