Supplementary Information For Oil And Gas Producing Activities (Results Of Operations For Producing Activities) (Details) - USD ($)		12 Months Ended
		Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2014
Reserve Quantities [Line Items]
Operating Revenues	[1]	$ 386,152,000	$ 506,721,000	$ 813,259,000
Production/Lifting Costs		153,914,000	167,800,000	165,534,000
Franchise/Ad Valorem Taxes		13,794,000	20,167,000	20,765,000
Purchased Emission Allowance Expense		700,000	3,089,000	0
Accretion Expense		6,663,000	6,186,000	6,192,000
Depreciation, Depletion and Amortization ($0.85, $1.49 and $1.82 per Mcfe of production)		136,579,000	234,480,000	291,651,000
Impairment of Oil and Gas Producing Properties		948,307,000	1,126,257,000	0
Income Tax Expense (Benefit)		(368,940,000)	(444,393,000)	140,484,000
Results of Operations for Producing Activities (excluding corporate overheads and interest charges)		(504,865,000)	(606,865,000)	188,633,000
Revenues from sales to affiliates		2,000	1,000	1,000
Depreciation, Depletion and Amortization, per Mcfe of Production		0.85	1.49	1.82
Results of Operations, Sales or Transfers to Entity's Other Operations		1,765,000	1,946,000	2,145,000
Natural Gas [Member]
Reserve Quantities [Line Items]
Natural Gas (includes revenues from sales to affiliates of $2 (2016) and $1 (2015 and 2014) and transfers to operations of $1,765, $1,946 and $2,145, respectively)		282,619,000	350,673,000	515,080,000
Oil, Condensate And Other Liquids [Member]
Reserve Quantities [Line Items]
Operating Revenues		$ 103,533,000	$ 156,048,000	$ 298,179,000

[1] Exclusive of hedging gains and losses. See further discussion in Note G — Financial Instruments.