Summary Of Significant Accounting Policies (Narrative) (Details) - USD ($) $ in Thousands	3 Months Ended				12 Months Ended
	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015	Jun. 13, 2016
Summary Of Significant Accounting Policies [Line Items]
Full cost ceiling test discount factor					10.00%
Amount full cost ceiling exceeds book value of oil and gas properties					$ 286,400
Increase estimated future net cash flows					30,500	$ 215,300	$ 194,500
Net Proceeds from Sale of Oil and Gas Producing Properties					26,554	137,316	$ 0
Goodwill	$ 5,476				5,476	5,476
Prior service (cost) credit	(1,300)				(1,200)	(1,300)
Gas stored underground	34,332				35,689	34,332
Customer Advances	14,762				15,701	14,762
Customer Security Deposits	16,019				$ 20,372	$ 16,019
Antidilutive securities					157,649	431,408	709,063
Cumulative Effect of Adoption of Authoritative Guidance for Stock-Based Compensation					$ 31,900
Impairment of Oil and Gas Producing Properties	32,700	$ 82,700	$ 397,400	$ 435,500	0	$ 948,307	$ 1,126,257
Receivable from Sale of Oil and Gas Producing Properties					0	19,543	$ 0
Amount Exceeds LIFO Basis [Member]
Summary Of Significant Accounting Policies [Line Items]
Gas stored underground					17,100
LIFO Method [Member]
Summary Of Significant Accounting Policies [Line Items]
Gas stored underground					26,700
Seneca [Member]
Summary Of Significant Accounting Policies [Line Items]
Cumulative Net Proceeds from Sale of Oil and Gas Producing Properties					163,900
Reduction in Property, Plant and Equipment					163,900
Net Proceeds from Sale of Oil and Gas Producing Properties					26,600	137,300
IOG-CRV Marcellus, LLC [Member]
Summary Of Significant Accounting Policies [Line Items]
Partner Working Interest In Joint Wells								80.00%
Internal Rate of Return								15.00%
Accumulated Losses [Member]
Summary Of Significant Accounting Policies [Line Items]
Accumulated losses	$ 75,200				$ 57,300	$ 75,200
Unamortized Debt Expense [Member]
Summary Of Significant Accounting Policies [Line Items]
Regulated Reacquisition of Debt Cost Weighted Average Amortization Period					2 years
26 Percent Net Revenue Interest [Member] | Seneca [Member]
Summary Of Significant Accounting Policies [Line Items]
Wells to be Developed								56
After Achieved Internal Rate of Return [Member] | Seneca [Member]
Summary Of Significant Accounting Policies [Line Items]
Partner Working Interest In Joint Wells								85.00%
Extended Agreement [Member] | Seneca [Member]
Summary Of Significant Accounting Policies [Line Items]
Partner Working Interest In Joint Wells								20.00%
Royalty Interest								7.50%
Partner Net Revenue Interest in Joint Wells								26.00%
Partner Working and Net Revenue Interest In Joint Wells								20.00%
Extended Agreement [Member] | IOG-CRV Marcellus, LLC [Member]
Summary Of Significant Accounting Policies [Line Items]
Wells to be Developed								75
Partner Commitment to Develop Joint Wells								$ 325,000
Partner Amount Funded to Develop Joint Wells					$ 262,600
20 Percent Net Revenue Interest [Member] | Seneca [Member]
Summary Of Significant Accounting Policies [Line Items]
Wells to be Developed								19