Summary Of Significant Accounting Policies (Narrative) (Details) - USD ($) $ in Thousands	1 Months Ended	12 Months Ended
	Oct. 31, 2017	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017	Oct. 01, 2019
Summary Of Significant Accounting Policies [Line Items]
Customer Security Deposits		$ 16,210	$ 25,703
Customer Advances		13,044	13,609
Pension and Postretirement Benefit Costs in Other Income and Deductions		27,300	32,600	$ 40,900
Capitalized Costs Oil And Gas Producing Activities Net		$ 1,664,553	1,314,300
Full cost ceiling test discount factor		10.00%
Amount full cost ceiling exceeds book value of oil and gas properties		$ 381,200
Increase (decrease) estimated future net cash flows		(17,700)	(25,100)	30,500
Net Proceeds from Sale of Oil and Gas Producing Properties		0	55,506	26,554
Depreciation, Depletion and Amortization Expense for Oil and Gas Properties		149,881	119,946	$ 108,471
Prior service cost		(1,000)	(1,000)
Goodwill		5,476	5,476
Gas stored underground		$ 36,632	$ 37,813
Antidilutive securities		242,302	317,899	157,649
Amount Exceeds LIFO Basis [Member]
Summary Of Significant Accounting Policies [Line Items]
Gas stored underground		$ 19,800
LIFO Method [Member]
Summary Of Significant Accounting Policies [Line Items]
Gas stored underground		29,600
Seneca [Member]
Summary Of Significant Accounting Policies [Line Items]
Net Proceeds from Sale of Oil and Gas Producing Properties			$ 17,300	$ 26,600
Accumulated Losses [Member]
Summary Of Significant Accounting Policies [Line Items]
Accumulated losses		$ 85,800	45,600
Unamortized Debt Expense [Member]
Summary Of Significant Accounting Policies [Line Items]
Regulated Reacquisition of Debt Cost Weighted Average Amortization Period		7 years
Sespe Field [Member]
Summary Of Significant Accounting Policies [Line Items]
Oil and Gas Producing Properties Purchase and Sale Agreement Price	$ 43,000
Net Proceeds from Sale of Oil and Gas Producing Properties			$ 38,200
Guidance for Reclassification of Stranded Tax Effects [Member]
Summary Of Significant Accounting Policies [Line Items]
Cumulative Effect of Adoption of Authoritative Guidance		$ 10,400
Guidance for Recognition and Measurement of Financial Assets and Liabilities [Member]
Summary Of Significant Accounting Policies [Line Items]
Cumulative Effect of Adoption of Authoritative Guidance		$ 7,400
Guidance for Leases [Member] | Forecast [Member]
Summary Of Significant Accounting Policies [Line Items]
Operating Lease Liability					$ 20,000
Right-of-Use Asset					20,000
Guidance for Hedge Accounting [Member] | Forecast [Member]
Summary Of Significant Accounting Policies [Line Items]
Cumulative Effect of Adoption of Authoritative Guidance					$ (1,000)