Consolidated Statements Of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2014
Operating Activities
Net Income (Loss) Available for Common Stock	$ (290,958)	$ (379,427)	$ 299,413
Adjustments to Reconcile Net Income (Loss) to Net Cash Provided by Operating Activities:
Impairment of Oil and Gas Producing Properties	948,307	1,126,257	0
Depreciation, Depletion and Amortization	249,417	336,158	383,781
Deferred Income Taxes	(246,794)	(357,587)	142,415
Excess Tax Benefits Associated with Stock-Based Compensation Awards	(1,868)	(9,064)	(4,641)
Stock-Based Compensation	5,755	3,208	11,763
Other	12,620	9,823	14,063
Change in:
Hedging Collateral Deposits	9,640	(8,390)	(1,640)
Receivables and Unbilled Revenue	(6,408)	51,638	(22,781)
Gas Stored Underground and Materials and Supplies	(3,532)	3,438	13,285
Unrecovered Purchased Gas Costs	(2,440)	0	12,408
Other Current Assets	3,179	3,150	(3,630)
Accounts Payable	(40,664)	34,687	15,149
Amounts Payable to Customers	(37,241)	23,033	20,917
Customer Advances	(1,474)	(2,769)	(2,954)
Customer Security Deposits	(471)	729	(422)
Other Accruals and Current Liabilities	3,453	(7,173)	6,872
Other Assets	1,941	2,696	18,513
Other Liabilities	(13,483)	23,173	6,879
Net Cash Provided by Operating Activities	588,979	853,580	909,390
Investing Activities
Capital Expenditures	(581,576)	(1,018,179)	(914,417)
Net Proceeds from Sale of Oil and Gas Producing Properties	137,316	0	0
Other	(9,236)	(6,611)	5,982
Net Cash Used in Investing Activities	(453,496)	(1,024,790)	(908,435)
Financing Activities
Change in Notes Payable to Banks and Commercial Paper	0	(85,600)	85,600
Excess Tax Benefits Associated with Stock-Based Compensation Awards	1,868	9,064	4,641
Net Proceeds from Issuance of Long-Term Debt	0	444,635	0
Net Proceeds from Issuance of Common Stock	13,849	10,540	7,474
Dividends Paid on Common Stock	(134,824)	(130,719)	(126,642)
Net Cash Provided By (Used in) Financing Activities	(119,107)	247,920	(28,927)
Net Increase (Decrease) in Cash and Temporary Cash Investments	16,376	76,710	(27,972)
Cash and Temporary Cash Investments At Beginning of Year	113,596	36,886	64,858
Cash and Temporary Cash Investments At End of Year	129,972	113,596	36,886
Supplemental Disclosure of Cash Flow Information
Cash Paid for Interest	119,563	90,747	91,927
Cash Paid for Income Taxes	34,240	18,657	40,944
Supplemental Disclosure of Cash Flow Information, Non-Cash Investing Activities
Non-Cash Capital Expenditures	60,434	118,959	136,628
Receivable from Sale of Oil and Gas Producing Properties	$ 19,543	$ 0	$ 0