Consolidated Statements Of Cash Flows (Unaudited) - USD ($) $ in Thousands	6 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
OPERATING ACTIVITIES
Net Income (Loss) Available for Common Stock	$ 178,191	$ (336,796)
Adjustments to Reconcile Net Income (Loss) to Net Cash Provided by Operating Activities:
Impairment of Oil and Gas Producing Properties	0	832,894
Depreciation, Depletion and Amortization	113,194	134,498
Deferred Income Taxes	63,781	(283,912)
Excess Tax Benefits Associated with Stock-Based Compensation Awards	0	(226)
Stock-Based Compensation	5,632	2,518
Other	7,713	6,106
Change in:
Hedging Collateral Deposits	(287)	1,161
Receivables and Unbilled Revenue	(92,155)	(28,211)
Gas Stored Underground and Materials and Supplies	24,476	22,637
Unrecovered Purchased Gas Costs	(2,241)	(1,245)
Other Current Assets	7,769	4,177
Accounts Payable	13,997	(31,786)
Amounts Payable to Customers	(71)	(14,561)
Customer Advances	(14,462)	(16,203)
Customer Security Deposits	1,493	(389)
Other Accruals and Current Liabilities	44,690	22,420
Other Assets	(32)	3,754
Other Liabilities	202	(4,073)
Net Cash Provided by Operating Activities	351,890	312,763
INVESTING ACTIVITIES
Capital Expenditures	(208,231)	(358,981)
Net Proceeds from Sale of Oil and Gas Producing Properties	26,554	104,938
Other	(3,225)	(18,249)
Net Cash Used in Investing Activities	(184,902)	(272,292)
Financing Activities
Excess Tax Benefits Associated with Stock-Based Compensation Awards	0	226
Dividends Paid on Common Stock	(69,017)	(66,887)
Net Proceeds from Issuance of Common Stock	3,230	6,294
Net Cash Used in Financing Activities	(65,787)	(60,367)
Net Increase (Decrease) in Cash and Temporary Cash Investments	101,201	(19,896)
Cash and Temporary Cash Investments at October 1	129,972	113,596
Cash and Temporary Cash Investments at March 31	231,173	93,700
Supplemental Disclosure of Cash Flow Information, Non-Cash Investing Activities:
Non-Cash Capital Expenditures	36,932	66,058
Receivable from Sale of Oil and Gas Producing Properties	$ 0	$ 10,297