Summary Of Significant Accounting Policies (Narrative) (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2019
Summary Of Significant Accounting Policies [Line Items]
Capitalized Costs Oil And Gas Producing Activities Net	$ 1,947,535	$ 1,874,128
Full cost ceiling test discount factor	10.00%
Impairment of Oil and Gas Producing Properties	$ 0	76,152	$ 449,438
Amount full cost ceiling exceeds book value of oil and gas properties	3,200,000
Increase (decrease) estimated future net cash flows	(1,000,000)	(76,100)	180,000
Depreciation, Depletion and Amortization Expense for Oil and Gas Properties	202,418	177,055	166,759
Goodwill	5,476	5,476
Prior service cost	(400)	(700)
Other Post-Retirement Adjustment for Regulatory Proceeding	(7,351)	0	0
Other Post-Retirement Adjustment for Regulatory Proceeding After Tax	(5,807)
Retained Earnings (Accumulated Deficit)	1,587,085	1,191,175	$ 991,630	$ 1,272,601
Gas stored underground	32,364	33,669
Customer Advances	26,108	17,223
Customer Security Deposits	$ 24,283	$ 19,292
Antidilutive securities	2,858	320,222	411,890
Rate recovery period	1 year
Amount Exceeds LIFO Basis [Member]
Summary Of Significant Accounting Policies [Line Items]
Gas stored underground	$ 178,500
LIFO Method [Member]
Summary Of Significant Accounting Policies [Line Items]
Gas stored underground	32,400
Accumulated Losses [Member]
Summary Of Significant Accounting Policies [Line Items]
Accumulated losses	$ 53,200	$ 62,900
Unamortized Debt Expense [Member]
Summary Of Significant Accounting Policies [Line Items]
Rate recovery period	5 years