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, 2015	Jun. 30, 2015	Mar. 31, 2015	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2014	Jun. 13, 2016	Dec. 01, 2015
Summary Of Significant Accounting Policies [Line Items]
Reclassification of Current Assets					$ 137,200				$ 137,200
Full cost ceiling test discount factor	10.00%							10.00%
Impairment of Oil and Gas Producing Properties	$ 32,700	$ 82,700	$ 397,400	$ 435,500	417,200	$ 588,700	$ 120,300	$ 948,307	1,126,257	$ 0
Increase (decrease) estimated future net cash flows								215,300	194,500	(33,600)
Net Proceeds from Sale of Oil and Gas Producing Properties								137,316	0	0
Receivable from Sale of Oil and Gas Producing Properties								19,543	0	$ 0
Goodwill	5,476				5,476			5,476	5,476
Prior service (cost) credit	(1,300)				(1,500)			(1,300)	(1,500)
Gas stored underground	34,332				34,252			34,332	34,252
Customer Advances	14,762				16,236			14,762	16,236
Customer Security Deposits	16,019				16,490			$ 16,019	$ 16,490
Antidilutive securities								431,408	709,063	1,007
Amount Exceeds LIFO Basis [Member]
Summary Of Significant Accounting Policies [Line Items]
Gas stored underground	7,000							$ 7,000
LIFO Method [Member]
Summary Of Significant Accounting Policies [Line Items]
Gas stored underground	27,600							27,600
Accumulated Losses [Member]
Summary Of Significant Accounting Policies [Line Items]
Accumulated losses	75,200				$ 68,300			$ 75,200	$ 68,300
Unamortized Debt Expense [Member]
Summary Of Significant Accounting Policies [Line Items]
Regulated Reacquisition of Debt Cost Weighted Average Amortization Period								3 years
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%
Seneca [Member]
Summary Of Significant Accounting Policies [Line Items]
Net Proceeds from Sale of Oil and Gas Producing Properties								$ 137,300
Receivable from Sale of Oil and Gas Producing Properties								19,600
Reduction in Property, Plant and Equipment	$ 156,900							156,900
Impairment of Oil and Gas Producing Properties [Member]
Summary Of Significant Accounting Policies [Line Items]
Deferred Income Tax Benefit								$ 398,300
Maximum [Member] | IOG-CRV Marcellus, LLC [Member]
Summary Of Significant Accounting Policies [Line Items]
Wells to be Developed											82
Initial Participation [Member] | IOG-CRV Marcellus, LLC [Member]
Summary Of Significant Accounting Policies [Line Items]
Wells to be Developed												42
26 Percent Net Revenue Interest [Member] | Seneca [Member]
Summary Of Significant Accounting Policies [Line Items]
Wells to be Developed											56
Additional Option to Participate [Member] | IOG-CRV Marcellus, LLC [Member]
Summary Of Significant Accounting Policies [Line Items]
Wells to be Developed											7
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] | 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
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%
20 Percent Net Revenue Interest [Member] | Seneca [Member]
Summary Of Significant Accounting Policies [Line Items]
Wells to be Developed											19