Supplementary Information For Oil And Gas Producing Activities (Standardized Measure Of Discounted Future Net Cash Flows Relating To Proved Oil And Gas Reserves) (Details) - USD ($) $ in Thousands	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2013
Supplementary Information For Oil And Gas Producing Activities Unaudited [Abstract]
Future Cash Inflows	$ 3,768,463	$ 6,916,775	$ 10,001,545
Future Production Costs	1,994,916	2,854,142	2,795,657
Future Development Costs	375,152	761,922	790,033
Future Income Tax Expense at Applicable Statutory Rate	303,397	1,117,433	2,434,370
Future Net Cash Flows	1,094,998	2,183,278	3,981,485
10% Annual Discount for Estimated Timing of Cash Flows	452,470	860,244	1,914,607
Standardized Measure of Discounted Future Net Cash Flows	$ 642,528	$ 1,323,034	$ 2,066,878	$ 1,966,366