Supplementary Information For Oil And Gas Producing Activities (Results Of Operations For Producing Activities) (Details) - USD ($)		12 Months Ended
		Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2013
Reserve Quantities [Line Items]
Operating Revenues	[1]	$ 506,721,000	$ 813,259,000	$ 663,073,000
Production/Lifting Costs		167,800,000	165,534,000	119,243,000
Franchise/Ad Valorem Taxes		20,167,000	20,765,000	17,200,000
Purchased Emission Allowance Expense		3,089,000	0	0
Accretion Expense		6,186,000	6,192,000	3,929,000
Depreciation, Depletion and Amortization ($1.49, $1.82 and $1.98 per Mcfe of production)		234,480,000	291,651,000	238,467,000
Impairment of Oil and Gas Producing Properties		1,126,257,000	0	0
Income Tax Expense		(444,393,000)	140,484,000	120,431,000
Results of Operations for Producing Activities (excluding corporate overheads and interest charges)		(606,865,000)	188,633,000	163,803,000
Revenues from sales to affiliates		1,000	1,000	1,000
Depreciation, Depletion and Amortization, per Mcfe of Production		1.49	1.82	1.98
Results of Operations, Sales or Transfers to Entity's Other Operations		1,946,000	2,145,000	612,000
Natural Gas [Member]
Reserve Quantities [Line Items]
Natural Gas (includes revenues from sales to affiliates of $1 for all years presented and transfers to operations of $1,946, $2,145 and $612, respectively)		350,673,000	515,080,000	371,311,000
Oil, Condensate And Other Liquids [Member]
Reserve Quantities [Line Items]
Operating Revenues		$ 156,048,000	$ 298,179,000	$ 291,762,000

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