Consolidated Statements Of Cash Flows (Unaudited) - USD ($) $ in Thousands	9 Months Ended
	Jun. 30, 2017	Jun. 30, 2016
OPERATING ACTIVITIES
Net Income (Loss) Available for Common Stock	$ 237,906	$ (328,510)
Adjustments to Reconcile Net Income (Loss) to Net Cash Provided by Operating Activities:
Impairment of Oil and Gas Producing Properties	0	915,552
Depreciation, Depletion and Amortization	168,812	193,300
Deferred Income Taxes	105,073	(269,248)
Excess Tax Benefits Associated with Stock-Based Compensation Awards	0	(1,786)
Stock-Based Compensation	8,857	3,138
Other	11,084	9,685
Change in:
Hedging Collateral Deposits	(658)	8,116
Receivables and Unbilled Revenue	(15,885)	(7,756)
Gas Stored Underground and Materials and Supplies	15,699	15,683
Unrecovered Purchased Gas Costs	(1,317)	(933)
Other Current Assets	8,502	15,334
Accounts Payable	5,046	(53,687)
Amounts Payable to Customers	(6,467)	(21,337)
Customer Advances	(14,538)	(16,198)
Customer Security Deposits	1,503	(396)
Other Accruals and Current Liabilities	25,423	3,375
Other Assets	(3,548)	3,775
Other Liabilities	5,638	(8,152)
Net Cash Provided by Operating Activities	551,130	459,955
INVESTING ACTIVITIES
Capital Expenditures	(314,774)	(481,781)
Net Proceeds from Sale of Oil and Gas Producing Properties	26,554	115,235
Other	(10,186)	(11,163)
Net Cash Used in Investing Activities	(298,406)	(377,709)
Financing Activities
Excess Tax Benefits Associated with Stock-Based Compensation Awards	0	1,786
Dividends Paid on Common Stock	(103,594)	(100,419)
Net Proceeds from Issuance of Common Stock	6,223	8,358
Net Cash Used in Financing Activities	(97,371)	(90,275)
Net Increase (Decrease) in Cash and Temporary Cash Investments	155,353	(8,029)
Cash and Temporary Cash Investments at October 1	129,972	113,596
Cash and Temporary Cash Investments at June 30	285,325	105,567
Supplemental Disclosure of Cash Flow Information, Non-Cash Investing Activities:
Non-Cash Capital Expenditures	47,508	44,380
Receivable from Sale of Oil and Gas Producing Properties	$ 0	$ 22,081