Regulatory Matters (Schedule Of Regulatory Assets And Liabilities) (Details) - USD ($) $ in Thousands		Sep. 30, 2015	Sep. 30, 2014
Regulatory Assets And Liabilities [Line Items]
Total Regulatory Assets	[1]	$ 469,097	$ 413,387
Less: Amounts Included in Other Current Assets	[1]	(20,438)	(22,719)
Total Long-Term Regulatory Assets		278,227	224,436
Total Regulatory Liabilities		445,096	397,904
Less: Amounts Included in Current and Accrued Liabilities		(62,124)	(51,817)
Total Long-Term Regulatory Liabilities		108,617	81,152
Cost Of Removal Regulatory Liability [Member]
Regulatory Assets And Liabilities [Line Items]
Total Regulatory Liabilities		184,907	173,199
Taxes Refundable To Customers [Member]
Regulatory Assets And Liabilities [Line Items]
Total Regulatory Liabilities		89,448	91,736
Post-Retirement Benefit Costs [Member]
Regulatory Assets And Liabilities [Line Items]
Total Regulatory Liabilities		60,013	53,650
Amounts Payable To Customers [Member]
Regulatory Assets And Liabilities [Line Items]
Total Regulatory Liabilities		56,778	33,745
Off-System Sales And Capacity Release Credits [Member]
Regulatory Assets And Liabilities [Line Items]
Total Regulatory Liabilities	[2]	21,027	12,805
Other Accruals and Current Liabilities [Member]
Regulatory Assets And Liabilities [Line Items]
Less: Amounts Included in Current and Accrued Liabilities		(5,346)	(5,267)
Other Regulatory Liabilities [Member]
Regulatory Assets And Liabilities [Line Items]
Total Regulatory Liabilities	[3]	32,923	32,769
Total Long-Term Regulatory Liabilities		27,577	27,502
Non-Current Regulatory Liabilities [Member]
Regulatory Assets And Liabilities [Line Items]
Total Long-Term Regulatory Liabilities		382,972	346,087
Pension Costs Asset [Member]
Regulatory Assets And Liabilities [Line Items]
Total Regulatory Assets	[1],[4]	202,781	164,804
Post-Retirement Benefit Costs [Member]
Regulatory Assets And Liabilities [Line Items]
Total Regulatory Assets	[1],[4]	34,217	17,128
Recoverable Future Taxes [Member]
Regulatory Assets And Liabilities [Line Items]
Total Regulatory Assets	[1]	168,214	163,485
Environmental Site Remediation Costs [Member]
Regulatory Assets And Liabilities [Line Items]
Total Regulatory Assets	[1],[4]	24,606	25,645
NYPSC Assessment [Member]
Regulatory Assets And Liabilities [Line Items]
Total Regulatory Assets	[1],[5]	13,916	12,730
Asset Retirement Obligations [Member]
Regulatory Assets And Liabilities [Line Items]
Total Regulatory Assets	[1],[4]	12,250	12,006
Unamortized Debt Expense [Member]
Regulatory Assets And Liabilities [Line Items]
Total Regulatory Assets	[1]	2,218	2,747
Other Regulatory Assets [Member]
Regulatory Assets And Liabilities [Line Items]
Total Regulatory Assets	[1],[6]	10,895	14,842
Total Long-Term Regulatory Assets		4,373	4,853
Other Current Assets [Member]
Regulatory Assets And Liabilities [Line Items]
Less: Amounts Included in Other Current Assets		(6,522)	(9,989)
Long-Term Regulatory Assets [Member]
Regulatory Assets And Liabilities [Line Items]
Total Long-Term Regulatory Assets	[1]	$ 448,659	$ 390,668

[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] The September 30, 2015 amount is included in Other Regulatory Liabilities on the Consolidated Balance Sheet at September 30, 2015. The September 30, 2014 amount is included in Other Accruals and Current Liabilities on the Consolidated Balance Sheet at September 30, 2014 since such amount is expected to be passed back to ratepayers in the next 12 months.

[3] $5,346 and $5,267 are included in Other Accruals and Current Liabilities on the Consolidated Balance Sheets at September 30, 2015 and 2014, respectively, since such amounts are expected to be recovered from ratepayers in the next 12 months. $27,577 and $27,502 are included in Other Regulatory Liabilities on the Consolidated Balance Sheets at September 30, 2015 and 2014, respectively.

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

[5] Amounts are included in Other Current Assets on the Consolidated Balance Sheets at September 30, 2015 and September 30, 2014 since such amounts are expected to be recovered from ratepayers in the next 12 months.

[6] $6,522 and $9,989 are included in Other Current Assets on the Consolidated Balance Sheets at September 30, 2015 and 2014, respectively, since such amounts are expected to be recovered from ratepayers in the next 12 months. $4,373 and $4,853 are included in Other Regulatory Assets on the Consolidated Balance Sheets at September 30, 2015 and 2014, respectively.