Regulatory Matters (Schedule Of Regulatory Assets And Liabilities) (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2012		Sep. 30, 2011
Regulatory Assets [Line Items]
Total Regulatory Assets	$ 731,515	[1]	$ 660,453	[1]
Less: Amounts Included in Other Current Assets	(29,726)	[1]	(26,589)	[1]
Total Long-Term Regulatory Assets	546,851		484,397
Total Regulatory Liabilities	265,270		248,028
Current regulatory liabilities	38,253		29,368
Total Long-Term Regulatory Liabilities	21,014		17,177
Cost Of Removal Regulatory Liability [Member]
Regulatory Assets [Line Items]
Total Regulatory Liabilities	139,611		135,940
Taxes Refundable To Customers [Member]
Regulatory Assets [Line Items]
Total Regulatory Liabilities	66,392		65,543
Amounts Payable To Customers [Member]
Regulatory Assets [Line Items]
Total Regulatory Liabilities	19,964		15,519
Off-System Sales And Capacity Release Credits [Member]
Regulatory Assets [Line Items]
Total Regulatory Liabilities	16,262	[2]	7,675	[2]
Other Accruals and Current Liabilities [Member]
Regulatory Assets [Line Items]
Current regulatory liabilities	2,027		6,174
Other Regulatory Liabilities [Member]
Regulatory Assets [Line Items]
Total Regulatory Liabilities	23,041	[3]	23,351	[3]
Total Long-Term Regulatory Liabilities	(21,014)		(17,177)
Non-Current Regulatory Liabilities [Member]
Regulatory Assets [Line Items]
Total Long-Term Regulatory Liabilities	227,017		218,660
Pension Costs Asset [Member]
Regulatory Assets [Line Items]
Total Regulatory Assets	344,228	[1],[4]	319,906	[1],[4]
Post-Retirement Benefit Costs [Member]
Regulatory Assets [Line Items]
Total Regulatory Assets	154,415	[1],[4]	124,423	[1],[4]
Recoverable Future Taxes [Member]
Regulatory Assets [Line Items]
Total Regulatory Assets	150,941	[1]	144,377	[1]
Environmental Site Remediation Costs [Member]
Regulatory Assets [Line Items]
Total Regulatory Assets	17,843	[1],[4]	20,095	[1],[4]
NYPSC Assessment [Member]
Regulatory Assets [Line Items]
Total Regulatory Assets	17,420	[1],[5]	15,063	[1],[5]
Asset Retirement Obligations [Member]
Regulatory Assets [Line Items]
Total Regulatory Assets	26,942	[1],[4]	13,860	[1],[4]
Unamortized Debt Expense [Member]
Regulatory Assets [Line Items]
Total Regulatory Assets	3,997	[1]	5,090	[1]
Other Regulatory Assets [Member]
Regulatory Assets [Line Items]
Total Regulatory Assets	15,729	[1],[6]	17,639	[1],[6]
Total Long-Term Regulatory Assets	3,423		6,113
Other Current Assets [Member]
Regulatory Assets [Line Items]
Less: Amounts Included in Other Current Assets	(12,306)		(11,526)
Long-Term Regulatory Assets [Member]
Regulatory Assets [Line Items]
Total Long-Term Regulatory Assets	$ 701,789	[1]	$ 633,864	[1]

[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] Amounts are included in Other Accruals and Current Liabilities on the Consolidated Balance Sheets at September 30, 2012 and September 30, 2011 since such amounts are expected to be passed back to ratepayers in the next 12 months.

[3] $2,027 and $6,174 are included in Other Accruals and Current Liabilities on the Consolidated Balance Sheets at September 30, 2012 and 2011, respectively, since such amounts are expected to be recovered from ratepayers in the next 12 months. $21,014 and $17,177 are included in Other Regulatory Liabilities on the Consolidated Balance Sheets at September 30, 2012 and 2011, 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, 2012 and September 30, 2011 since such amounts are expected to be recovered from ratepayers in the next 12 months.

[6] $12,306 and $11,526 are included in Other Current Assets on the Consolidated Balance Sheets at September 30, 2012 and 2011, respectively, since such amounts are expected to be recovered from ratepayers in the next 12 months. $3,423 and $6,113 are included in Other Regulatory Assets on the Consolidated Balance Sheets at September 30, 2012 and 2011, respectively.