Consolidated Statements Of Cash Flows (Unaudited) - USD ($) $ in Thousands	6 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
OPERATING ACTIVITIES
Net Income Available for Common Stock	$ 290,501	$ 178,191
Adjustments to Reconcile Net Income to Net Cash Provided by Operating Activities:
Depreciation, Depletion and Amortization	116,985	113,194
Deferred Income Taxes	(62,459)	63,781
Stock-Based Compensation	7,862	5,632
Other	8,052	7,713
Change in:
Hedging Collateral Deposits	(1,916)	(287)
Receivables and Unbilled Revenue	(123,954)	(92,155)
Gas Stored Underground and Materials and Supplies	28,004	24,476
Unrecovered Purchased Gas Costs	4,197	(2,241)
Other Current Assets	(8,819)	7,769
Accounts Payable	10,838	13,997
Amounts Payable to Customers	12,083	(71)
Customer Advances	(15,547)	(14,462)
Customer Security Deposits	(1,399)	1,493
Other Accruals and Current Liabilities	37,646	44,690
Other Assets	(9,541)	(32)
Other Liabilities	(5,767)	202
Net Cash Provided by Operating Activities	286,766	351,890
INVESTING ACTIVITIES
Capital Expenditures	(261,720)	(208,231)
Net Proceeds from Sale of Oil and Gas Producing Properties	17,310	26,554
Other	5,355	(3,225)
Net Cash Used in Investing Activities	(239,055)	(184,902)
Financing Activities
Reduction of Long-Term Debt	(307,047)	0
Dividends Paid on Common Stock	(71,091)	(69,017)
Net Proceeds from Issuance of Common Stock	2,891	3,230
Net Cash Used in Financing Activities	(375,247)	(65,787)
Net Increase (Decrease) in Cash and Temporary Cash Investments	(327,536)	101,201
Cash and Temporary Cash Investments at October 1	555,530	129,972
Cash and Temporary Cash Investments at March 31	227,994	231,173
Supplemental Disclosure of Cash Flow Information, Non-Cash Investing Activities:
Non-Cash Capital Expenditures	$ 51,939	$ 36,932