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, 2018	Sep. 30, 2017	Sep. 30, 2016
Defined Benefit Plan Disclosure [Line Items]
Non-Current Assets		$ 82,733	$ 56,370
Amortization period		10 years
Retirement Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Benefit Obligation at Beginning of Period		$ 1,054,826	1,097,421	$ 1,026,190
Service Cost		9,921	11,969	11,710
Interest Cost		33,006	38,383	42,315
Plan Participants' Contributions		0	0	0
Retiree Drug Subsidy Receipts		0	0	0
Actuarial (Gain) Loss		(50,218)	(32,466)	76,309
Benefits Paid		(61,845)	(60,481)	(59,103)
Benefit Obligation at End of Period		985,690	1,054,826	1,097,421
Fair Value of Assets at Beginning of Period		910,719	869,775	834,870
Actual Return on Plan Assets		42,652	84,279	87,008
Employer Contributions		32,980	17,146	7,000
Plan Participants' Contributions		0	0	0
Benefits Paid		(61,845)	(60,481)	(59,103)
Fair Value of Assets at End of Period		924,506	910,719	869,775
Net Amount Recognized at End of Period (Funded Status)		(61,184)	(144,107)	(227,646)
Non-Current Liabilities		(61,184)	(144,107)	(227,646)
Non-Current Assets		0	0	0
Accumulated Benefit Obligation		$ 946,763	$ 1,010,179	$ 1,039,408
Discount Rate		4.30%	3.77%	3.60%
Rate of Compensation Increase		4.70%	4.70%	4.70%
Expected Return on Plan Assets		$ (61,715)	$ (59,718)	$ (59,369)
Amortization of Prior Service Cost (Credit)		938	1,058	1,234
Recognition of Actuarial Loss	[1]	37,205	42,687	32,248
Net Amortization and Deferral for Regulatory Purposes		9,027	469	3,957
Net Periodic Benefit Cost		$ 28,382	$ 34,848	$ 32,095
Effective Discount Rate for Benefit Obligations		3.77%	3.60%	4.25%
Effective Rate for Interest on Benefit Obligations		3.23%	3.60%	4.25%
Effective Discount Rate for Service Cost		4.00%	3.60%	4.25%
Effective Rate for Interest on Service Cost		3.73%	3.60%	4.25%
Expected Return on Plan Assets		7.00%	7.00%	7.25%
Rate of Compensation Increase		4.70%	4.70%	4.75%
Other Post-Retirement Benefit Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Benefit Obligation at Beginning of Period		$ 462,619	$ 526,138	$ 464,987
Service Cost		1,830	2,449	2,331
Interest Cost		14,801	19,007	20,386
Plan Participants' Contributions		2,894	2,717	2,558
Retiree Drug Subsidy Receipts		1,545	1,553	1,925
Actuarial (Gain) Loss		(21,039)	(62,215)	60,402
Benefits Paid		(26,664)	(27,030)	(26,451)
Benefit Obligation at End of Period		435,986	462,619	526,138
Fair Value of Assets at Beginning of Period		514,017	494,320	477,959
Actual Return on Plan Assets		20,657	40,157	37,415
Employer Contributions		2,896	3,853	2,839
Plan Participants' Contributions		2,894	2,717	2,558
Benefits Paid		(26,664)	(27,030)	(26,451)
Fair Value of Assets at End of Period		513,800	514,017	494,320
Net Amount Recognized at End of Period (Funded Status)		77,814	51,398	(31,818)
Non-Current Liabilities		(4,919)	(4,972)	(49,467)
Non-Current Assets		$ 82,733	$ 56,370	$ 17,649
Discount Rate		4.31%	3.81%	3.70%
Rate of Compensation Increase		4.70%	4.70%	4.70%
Expected Return on Plan Assets		$ (31,482)	$ (31,458)	$ (31,535)
Amortization of Prior Service Cost (Credit)		(429)	(429)	(912)
Recognition of Actuarial Loss	[1]	10,558	18,415	5,530
Net Amortization and Deferral for Regulatory Purposes		15,028	6,108	17,123
Net Periodic Benefit Cost		$ 10,306	$ 14,092	$ 12,923
Effective Discount Rate for Benefit Obligations		3.81%	3.70%	4.50%
Effective Rate for Interest on Benefit Obligations		3.29%	3.70%	4.50%
Effective Discount Rate for Service Cost		4.10%	3.70%	4.50%
Effective Rate for Interest on Service Cost		3.98%	3.70%	4.50%
Expected Return on Plan Assets		6.25%	6.50%	6.75%
Rate of Compensation Increase		4.70%	4.70%	4.75%

[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.