Supplementary Information For Oil And Gas Producing Activities (Summary Of Capitalized Costs Of Unproved Properties Excluded From Amortization) (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2013
Capitalized Costs of Unproved Properties Excluded from Amortization [Line Items]
Acquisition Costs	$ 0	$ 0	$ 7,057
Development Costs	40,597	7,911	1,436
Exploration Costs	17,340	9,482	0
Capitalized Interest	339	151	0
Capitalized Costs of Unproved Properties Excluded from Amortization, Total	58,276	$ 17,544	$ 8,493
Capitalized Costs Of Unproved Properties Cumulative Balance [Member]
Capitalized Costs of Unproved Properties Excluded from Amortization [Line Items]
Acquisition Costs	55,193
Development Costs	52,780
Exploration Costs	26,822
Capitalized Interest	490
Capitalized Costs of Unproved Properties Excluded from Amortization, Total	$ 135,285
Costs Incurred Prior To Fiscal 2014 [Member]
Capitalized Costs of Unproved Properties Excluded from Amortization [Line Items]
Acquisition Costs				$ 48,136
Development Costs				2,836
Exploration Costs				0
Capitalized Interest				0
Capitalized Costs of Unproved Properties Excluded from Amortization, Total				$ 50,972