Retirement Plan And Other Post-Retirement Benefits (Schedule Of Benefit Obligations, Plan Assets And Funded Status) (Details) - USD ($) $ in Thousands		12 Months Ended
		Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017
Defined Benefit Plan Disclosure [Line Items]
Non-Current Assets		$ 60,517	$ 82,733
Amortization period		10 years
Retirement Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Benefit Obligation at Beginning of Period		$ 985,690	1,054,826	$ 1,097,421
Service Cost		8,482	9,921	11,969
Interest Cost		38,378	33,006	38,383
Plan Participants' Contributions		0	0	0
Retiree Drug Subsidy Receipts		0	0	0
Actuarial (Gain) Loss		127,748	(50,218)	(32,466)
Benefits Paid		(62,673)	(61,845)	(60,481)
Benefit Obligation at End of Period		1,097,625	985,690	1,054,826
Fair Value of Assets at Beginning of Period		924,506	910,719	869,775
Actual Return on Plan Assets		77,401	42,652	84,279
Employer Contributions		29,215	32,980	17,146
Plan Participants' Contributions		0	0	0
Benefits Paid		(62,673)	(61,845)	(60,481)
Fair Value of Assets at End of Period		968,449	924,506	910,719
Net Amount Recognized at End of Period (Funded Status)		(129,176)	(61,184)	(144,107)
Non-Current Liabilities		(129,176)	(61,184)	(144,107)
Non-Current Assets		0	0	0
Accumulated Benefit Obligation		$ 1,053,914	$ 946,763	$ 1,010,179
Discount Rate		3.15%	4.30%	3.77%
Rate of Compensation Increase		4.70%	4.70%	4.70%
Expected Return on Plan Assets		$ (62,368)	$ (61,715)	$ (59,718)
Amortization of Prior Service Cost (Credit)		826	938	1,058
Recognition of Actuarial Loss	[1]	32,096	37,205	42,687
Net Amortization and Deferral for Regulatory Purposes		2,493	9,027	469
Net Periodic Benefit Cost		$ 19,907	$ 28,382	$ 34,848
Effective Discount Rate for Benefit Obligations		4.30%	3.77%	3.60%
Effective Rate for Interest on Benefit Obligations		4.03%	3.23%	3.60%
Effective Discount Rate for Service Cost		4.40%	4.00%	3.60%
Effective Rate for Interest on Service Cost		4.29%	3.73%	3.60%
Expected Return on Plan Assets		6.75%	7.00%	7.00%
Rate of Compensation Increase		4.70%	4.70%	4.70%
Other Post-Retirement Benefit Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Benefit Obligation at Beginning of Period		$ 435,986	$ 462,619	$ 526,138
Service Cost		1,519	1,830	2,449
Interest Cost		17,145	14,801	19,007
Plan Participants' Contributions		2,930	2,894	2,717
Retiree Drug Subsidy Receipts		1,855	1,545	1,553
Actuarial (Gain) Loss		34,401	(21,039)	(62,215)
Benefits Paid		(25,673)	(26,664)	(27,030)
Benefit Obligation at End of Period		468,163	435,986	462,619
Fair Value of Assets at Beginning of Period		513,800	514,017	494,320
Actual Return on Plan Assets		30,006	20,657	40,157
Employer Contributions		3,064	2,896	3,853
Plan Participants' Contributions		2,930	2,894	2,717
Benefits Paid		(25,673)	(26,664)	(27,030)
Fair Value of Assets at End of Period		524,127	513,800	514,017
Net Amount Recognized at End of Period (Funded Status)		55,964	77,814	51,398
Non-Current Liabilities		(4,553)	(4,919)	(4,972)
Non-Current Assets		$ 60,517	$ 82,733	$ 56,370
Discount Rate		3.17%	4.31%	3.81%
Rate of Compensation Increase		4.70%	4.70%	4.70%
Expected Return on Plan Assets		$ (30,157)	$ (31,482)	$ (31,458)
Amortization of Prior Service Cost (Credit)		(429)	(429)	(429)
Recognition of Actuarial Loss	[1]	5,962	10,558	18,415
Net Amortization and Deferral for Regulatory Purposes		16,481	15,028	6,108
Net Periodic Benefit Cost		$ 10,521	$ 10,306	$ 14,092
Effective Discount Rate for Benefit Obligations		4.31%	3.81%	3.70%
Effective Rate for Interest on Benefit Obligations		4.05%	3.29%	3.70%
Effective Discount Rate for Service Cost		4.43%	4.10%	3.70%
Effective Rate for Interest on Service Cost		4.39%	3.98%	3.70%
Expected Return on Plan Assets		6.00%	6.25%	6.50%
Rate of Compensation Increase		4.70%	4.70%	4.70%

[1] Distribution Corporation’s New York jurisdiction calculates the amortization of the actuarial loss on a vintage year basis over 10 years, as mandated by the NYPSC. All the other subsidiaries of the Company utilize the corridor approach.