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, 2017	Sep. 30, 2016	Sep. 30, 2015
Defined Benefit Plan Disclosure [Line Items]
Non-Current Assets		$ 56,370	$ 17,649
Amortization period		10 years
Retirement Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Benefit Obligation at Beginning of Period		$ 1,097,421	1,026,190	$ 999,499
Service Cost		11,969	11,710	12,047
Interest Cost		38,383	42,315	41,217
Plan Participants' Contributions		0	0	0
Retiree Drug Subsidy Receipts		0	0	0
Amendments	[1]	0	0	7,752
Actuarial (Gain) Loss		(32,466)	76,309	23,426
Benefits Paid		(60,481)	(59,103)	(57,751)
Benefit Obligation at End of Period		1,054,826	1,097,421	1,026,190
Fair Value of Assets at Beginning of Period		869,775	834,870	869,791
Actual Return on Plan Assets		84,279	87,008	(13,370)
Employer Contributions		17,146	7,000	36,200
Plan Participants' Contributions		0	0	0
Benefits Paid		(60,481)	(59,103)	(57,751)
Fair Value of Assets at End of Period		910,719	869,775	834,870
Net Amount Recognized at End of Period (Funded Status)		(144,107)	(227,646)	(191,320)
Non-Current Liabilities		(144,107)	(227,646)	(191,320)
Non-Current Assets		0	0	0
Accumulated Benefit Obligation		$ 1,010,179	$ 1,039,408	$ 968,984
Discount Rate		3.77%	3.60%	4.25%
Rate of Compensation Increase		4.70%	4.70%	4.75%
Expected Return on Plan Assets		$ (59,718)	$ (59,369)	$ (59,615)
Amortization of Prior Service Cost (Credit)		1,058	1,234	183
Recognition of Actuarial Loss	[2]	42,687	32,248	36,129
Net Amortization and Deferral for Regulatory Purposes		469	3,957	7,739
Net Periodic Benefit Cost		$ 34,848	$ 32,095	$ 37,700
Discount Rate		3.60%	4.25%	4.25%
Expected Return on Plan Assets		7.00%	7.25%	7.50%
Rate of Compensation Increase		4.75%	4.75%	4.75%
Other Post-Retirement Benefit Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Benefit Obligation at Beginning of Period		$ 526,138	$ 464,987	$ 465,583
Service Cost		2,449	2,331	2,693
Interest Cost		19,007	20,386	19,285
Plan Participants' Contributions		2,717	2,558	2,242
Retiree Drug Subsidy Receipts		1,553	1,925	1,338
Amendments	[1]	0	0	0
Actuarial (Gain) Loss		(62,215)	60,402	(1,575)
Benefits Paid		(27,030)	(26,451)	(24,579)
Benefit Obligation at End of Period		462,619	526,138	464,987
Fair Value of Assets at Beginning of Period		494,320	477,959	497,601
Actual Return on Plan Assets		40,157	37,415	534
Employer Contributions		3,853	2,839	2,161
Plan Participants' Contributions		2,717	2,558	2,242
Benefits Paid		(27,030)	(26,451)	(24,579)
Fair Value of Assets at End of Period		514,017	494,320	477,959
Net Amount Recognized at End of Period (Funded Status)		51,398	(31,818)	12,972
Non-Current Liabilities		(4,972)	(49,467)	(11,487)
Non-Current Assets		$ 56,370	$ 17,649	$ 24,459
Discount Rate		3.81%	3.70%	4.50%
Rate of Compensation Increase		4.70%	4.70%	4.75%
Expected Return on Plan Assets		$ (31,458)	$ (31,535)	$ (34,089)
Amortization of Prior Service Cost (Credit)		(429)	(912)	(1,913)
Recognition of Actuarial Loss	[2]	18,415	5,530	4,148
Net Amortization and Deferral for Regulatory Purposes		6,108	17,123	20,322
Net Periodic Benefit Cost		$ 14,092	$ 12,923	$ 10,446
Discount Rate		3.70%	4.50%	4.25%
Expected Return on Plan Assets		6.50%	6.75%	7.00%
Rate of Compensation Increase		4.75%	4.75%	4.75%

[1] In fiscal 2015, the Company passed an amendment which updated the mortality table used in the Retirement Plan's definition of "actuarially equivalent" effective July 1, 2015. This increased the benefit obligation of the Retirement Plan.

[2] 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.