Supplementary Information For Oil And Gas Producing Activities (Costs Incurred In Oil And Gas Property Acquisition, Exploration And Development Activities) (Details) - USD ($) $ in Thousands		12 Months Ended
		Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
Supplementary Information For Oil And Gas Producing Activities Unaudited [Abstract]
Proved		$ 8,908	$ 1,342	$ 1,767
Unproved		262	2,165	19,998
Exploration Costs	[1]	40,975	27,561	53,222
Development Costs	[2]	200,639	219,386	454,605
Asset Retirement Costs		(9,175)	(49,653)	37,595
Total Property Acquisition Costs		241,609	200,801	567,187
Capitalized interest included in exploration costs		300	300	400
Capitalized interest included in development costs		$ 200	$ 200	$ 500

[1] Amounts for 2017, 2016 and 2015 include capitalized interest of $0.3 million, $0.3 million and $0.4 million, respectively.

[2] Amounts for 2017, 2016 and 2015 include capitalized interest of $0.2 million, $0.2 million and $0.5 million, respectively.