Regulatory Matters (Schedule Of Regulatory Assets And Liabilities) (Details) (USD $) In Thousands	Sep. 30, 2011		Sep. 30, 2010
Total Regulatory Assets	$ 724,111	[1]	$ 698,240	[1]
Total Regulatory Liabilities	311,686		321,060
Net Regulatory Position	412,425		377,180
Pension Costs Asset [Member]
Total Regulatory Assets	333,219	[1],[2]	308,822	[1],[2]
Post-Retirement Benefit Costs [Member]
Total Regulatory Assets	174,768	[1],[2]	159,498	[1],[2]
Recoverable Future Taxes [Member]
Total Regulatory Assets	144,377	[1]	149,712	[1]
Environmental Site Remediation Costs [Member]
Total Regulatory Assets	20,095	[1],[2]	20,491	[1],[2]
NYPSC Assessment [Member]
Total Regulatory Assets	15,063	[1],[2]	19,229	[1],[2]
Asset Retirement Obligations [Member]
Total Regulatory Assets	13,860	[1],[2]	12,529	[1],[2]
Unamortized Debt Expense [Member]
Total Regulatory Assets	5,090	[1]	5,727	[1]
Other Regulatory Assets [Member]
Total Regulatory Assets	17,639	[1],[2]	22,232	[1],[2]
Cost Of Removal Regulatory Liability [Member]
Total Regulatory Liabilities	135,940		124,032
Taxes Refundable To Customers [Member]
Total Regulatory Liabilities	65,543		69,585
Post-Retirement Benefit Costs [Member]
Total Regulatory Liabilities	50,409	[3]	42,461	[3]
Amounts Payable To Customers [Member]
Total Regulatory Liabilities	15,519		38,109
Pension Costs Liability [Member]
Total Regulatory Liabilities	13,313	[3]	16,171	[3]
Off-System Sales And Capacity Release Credits [Member]
Total Regulatory Liabilities	7,675	[3]	11,594	[3]
Other Regulatory Liabilities [Member]
Total Regulatory Liabilities	$ 23,287	[3]	$ 19,108	[3]

[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 Assets on the Consolidated Balance Sheets.

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