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, 2020	Sep. 30, 2019	Sep. 30, 2018
Defined Benefit Plan Disclosure [Line Items]
Non-Current Assets		$ 76,035	$ 60,517
Amortization period		10 years
Retirement Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Benefit Obligation at Beginning of Period		$ 1,097,625	985,690	$ 1,054,826
Service Cost		9,318	8,482	9,921
Interest Cost		29,930	38,378	33,006
Plan Participants' Contributions		0	0	0
Retiree Drug Subsidy Receipts		0	0	0
Actuarial (Gain) Loss		65,908	127,748	(50,218)
Benefits Paid		(63,676)	(62,673)	(61,845)
Benefit Obligation at End of Period		1,139,105	1,097,625	985,690
Fair Value of Assets at Beginning of Period		968,449	924,506	910,719
Actual Return on Plan Assets		87,402	77,401	42,652
Employer Contributions		24,621	29,215	32,980
Plan Participants' Contributions		0	0	0
Benefits Paid		(63,676)	(62,673)	(61,845)
Fair Value of Assets at End of Period		1,016,796	968,449	924,506
Net Amount Recognized at End of Period (Funded Status)		(122,309)	(129,176)	(61,184)
Non-Current Liabilities		(122,309)	(129,176)	(61,184)
Non-Current Assets		0	0	0
Accumulated Benefit Obligation		$ 1,096,427	$ 1,053,914	$ 946,763
Discount Rate		2.66%	3.15%	4.30%
Rate of Compensation Increase		4.70%	4.70%	4.70%
Expected Return on Plan Assets		$ (60,063)	$ (62,368)	$ (61,715)
Amortization of Prior Service Cost (Credit)		729	826	938
Recognition of Actuarial Loss	[1]	39,384	32,096	37,205
Net Amortization and Deferral for Regulatory Purposes		5,359	2,493	9,027
Net Periodic Benefit Cost		$ 24,657	$ 19,907	$ 28,382
Effective Discount Rate for Benefit Obligations		3.15%	4.30%	3.77%
Effective Rate for Interest on Benefit Obligations		2.81%	4.03%	3.23%
Effective Discount Rate for Service Cost		3.31%	4.40%	4.00%
Effective Rate for Interest on Service Cost		3.12%	4.29%	3.73%
Expected Return on Plan Assets		6.40%	6.75%	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		$ 468,163	$ 435,986	$ 462,619
Service Cost		1,609	1,519	1,830
Interest Cost		12,913	17,145	14,801
Plan Participants' Contributions		3,058	2,930	2,894
Retiree Drug Subsidy Receipts		1,411	1,855	1,545
Actuarial (Gain) Loss		16,396	34,401	(21,039)
Benefits Paid		(26,828)	(25,673)	(26,664)
Benefit Obligation at End of Period		476,722	468,163	435,986
Fair Value of Assets at Beginning of Period		524,127	513,800	514,017
Actual Return on Plan Assets		44,448	30,006	20,657
Employer Contributions		3,080	3,064	2,896
Plan Participants' Contributions		3,058	2,930	2,894
Benefits Paid		(26,828)	(25,673)	(26,664)
Fair Value of Assets at End of Period		547,885	524,127	513,800
Net Amount Recognized at End of Period (Funded Status)		71,163	55,964	77,814
Non-Current Liabilities		(4,872)	(4,553)	(4,919)
Non-Current Assets		$ 76,035	$ 60,517	$ 82,733
Discount Rate		2.71%	3.17%	4.31%
Rate of Compensation Increase		4.70%	4.70%	4.70%
Expected Return on Plan Assets		$ (29,232)	$ (30,157)	$ (31,482)
Amortization of Prior Service Cost (Credit)		(429)	(429)	(429)
Recognition of Actuarial Loss	[1]	535	5,962	10,558
Net Amortization and Deferral for Regulatory Purposes		25,596	16,481	15,028
Net Periodic Benefit Cost		$ 10,992	$ 10,521	$ 10,306
Effective Discount Rate for Benefit Obligations		3.17%	4.31%	3.81%
Effective Rate for Interest on Benefit Obligations		2.84%	4.05%	3.29%
Effective Discount Rate for Service Cost		3.39%	4.43%	4.10%
Effective Rate for Interest on Service Cost		3.30%	4.39%	3.98%
Expected Return on Plan Assets		5.70%	6.00%	6.25%
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.