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, 2015	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2012
Supplementary Information For Oil And Gas Producing Activities Unaudited [Abstract]
Future Cash Inflows	$ 6,916,775	$ 10,001,545	$ 8,943,942
Future Production Costs	2,854,142	2,795,657	2,334,393
Future Development Costs	761,922	790,033	749,876
Future Income Tax Expense at Applicable Statutory Rate	1,117,433	2,434,370	2,113,101
Future Net Cash Flows	2,183,278	3,981,485	3,746,572
10% Annual Discount for Estimated Timing of Cash Flows	860,244	1,914,607	1,780,206
Standardized Measure of Discounted Future Net Cash Flows	$ 1,323,034	$ 2,066,878	$ 1,966,366	$ 1,469,791