Regulatory Matters (Schedule Of Regulatory Assets And Liabilities) (Details) - USD ($) $ in Thousands		Sep. 30, 2020	Sep. 30, 2019
Regulatory Assets And Liabilities [Line Items]
Total Regulatory Assets	[1]	$ 303,322	$ 307,982
Less: Amounts Included in Other Current Assets	[1]	(16,609)	(11,460)
Total Long-Term Regulatory Assets		156,106	167,320
Total Regulatory Liabilities		804,838	784,918
Less: Amounts Included in Current and Accrued Liabilities		(55,678)	(54,349)
Total Long-Term Regulatory Liabilities		161,573	142,367
Cost Of Removal Regulatory Liability [Member]
Regulatory Assets And Liabilities [Line Items]
Total Regulatory Liabilities		230,079	221,699
Taxes Refundable To Customers [Member]
Regulatory Assets And Liabilities [Line Items]
Total Regulatory Liabilities		357,508	366,503
Post-Retirement Benefit Costs [Member]
Regulatory Assets And Liabilities [Line Items]
Total Regulatory Liabilities	[2]	146,474	126,577
Amounts Payable To Customers [Member]
Regulatory Assets And Liabilities [Line Items]
Total Regulatory Liabilities		10,788	4,017
Other [Member]
Regulatory Assets And Liabilities [Line Items]
Total Regulatory Liabilities	[3]	59,989	66,122
Total Long-Term Regulatory Liabilities		15,099	15,790
Non-Current Regulatory Liabilities [Member]
Regulatory Assets And Liabilities [Line Items]
Total Long-Term Regulatory Liabilities		749,160	730,569
Other Accruals and Current Liabilities [Member]
Regulatory Assets And Liabilities [Line Items]
Less: Amounts Included in Current and Accrued Liabilities		(44,890)	(50,332)
Pension Costs Asset [Member]
Regulatory Assets And Liabilities [Line Items]
Total Regulatory Assets	[1],[4]	107,010	114,509
Post-Retirement Benefit Costs [Member]
Regulatory Assets And Liabilities [Line Items]
Total Regulatory Assets	[1],[4]	18,863	18,236
Recoverable Future Taxes [Member]
Regulatory Assets And Liabilities [Line Items]
Total Regulatory Assets	[1]	118,310	115,197
Environmental Site Remediation Costs [Member]
Regulatory Assets And Liabilities [Line Items]
Total Regulatory Assets	[1],[4]	10,479	15,317
Asset Retirement Obligations [Member]
Regulatory Assets And Liabilities [Line Items]
Total Regulatory Assets	[1],[4]	16,245	15,696
Unamortized Debt Expense [Member]
Regulatory Assets And Liabilities [Line Items]
Total Regulatory Assets	[1]	12,297	14,005
Other [Member]
Regulatory Assets And Liabilities [Line Items]
Total Regulatory Assets	[1],[5]	20,118	15,022
Total Long-Term Regulatory Assets		3,509	3,562
Long-Term Regulatory Assets [Member]
Regulatory Assets And Liabilities [Line Items]
Total Long-Term Regulatory Assets	[1]	286,713	296,522
Other Current Assets [Member]
Regulatory Assets And Liabilities [Line Items]
Less: Amounts Included in Other Current Assets		$ (16,609)	$ (11,460)

[1] The Company recovers the cost of its regulatory assets but generally does not earn a return on them. There are a few exceptions to this rule. For example, the Company does earn a return on Unrecovered Purchased Gas Costs and, in the New York jurisdiction of its Utility segment, earns a return, within certain parameters, on the excess of cumulative funding to the pension plan over the cumulative amount collected in rates.

[2] Included in Other Regulatory Liabilities on the Consolidated Balance Sheets.

[3] $44,890 and $50,332 are included in Other Accruals and Current Liabilities on the Consolidated Balance Sheets at September 30, 2020 and 2019, respectively, since such amounts are expected to be recovered from ratepayers in the next 12 months. $15,099 and $15,790 are included in Other Regulatory Liabilities on the Consolidated Balance Sheets at September 30, 2020 and 2019, respectively.

[4] Included in Other Regulatory Assets on the Consolidated Balance Sheets.

[5] $16,609 and $11,460 are included in Other Current Assets on the Consolidated Balance Sheets at September 30, 2020 and 2019, respectively, since such amounts are expected to be recovered from ratepayers in the next 12 months. $3,509 and $3,562 are included in Other Regulatory Assets on the Consolidated Balance Sheets at September 30, 2020 and 2019, respectively.