Consolidated Statements Of Cash Flows (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
OPERATING ACTIVITIES
Net Income Available for Common Stock	$ 198,654	$ 88,908
Adjustments to Reconcile Net Income to Net Cash Provided by Operating Activities:
Depreciation, Depletion and Amortization	55,830	56,196
Deferred Income Taxes	(94,676)	44,852
Stock-Based Compensation	3,905	2,482
Other	3,678	3,607
Change in:
Hedging Collateral Deposits	(2,724)	1,484
Receivables and Unbilled Revenue	(83,357)	(67,395)
Gas Stored Underground and Materials and Supplies	10,337	10,597
Unrecovered Purchased Gas Costs	(3,164)	(1,257)
Other Current Assets	3,591	9,576
Accounts Payable	13,173	18,805
Amounts Payable to Customers	251	(16,306)
Customer Advances	2,697	(983)
Customer Security Deposits	2,131	673
Other Accruals and Current Liabilities	11,532	5,919
Other Assets	(5,275)	(8,389)
Other Liabilities	(21,775)	(4,122)
Net Cash Provided by Operating Activities	94,808	144,647
INVESTING ACTIVITIES
Capital Expenditures	(142,613)	(106,053)
Net Proceeds from Sale of Oil and Gas Producing Properties	0	5,759
Other	2,612	(4,297)
Net Cash Used in Investing Activities	(140,001)	(104,591)
Financing Activities
Reduction of Long-Term Debt	307,047	0
Dividends Paid on Common Stock	(35,500)	(34,473)
Net Proceeds from Issuance (Repurchase) of Common Stock	(1,501)	938
Net Cash Used in Financing Activities	(344,048)	(33,535)
Net Increase (Decrease) in Cash and Temporary Cash Investments	(389,241)	6,521
Cash and Temporary Cash Investments at October 1	555,530	129,972
Cash and Temporary Cash Investments at December 31	166,289	136,493
Supplemental Disclosure of Cash Flow Information, Non-Cash Investing Activities:
Non-Cash Capital Expenditures	56,116	48,965
Receivable from Sale of Oil and Gas Producing Properties	$ 17,310	$ 20,795