Summary Of Significant Accounting Policies (Components Of Other Current Assets) (Details) - USD ($) $ in Thousands		Sep. 30, 2017	Sep. 30, 2016
Summary Of Significant Accounting Policies [Line Items]
Prepayments		$ 10,927	$ 10,919
Prepaid Property and Other Taxes		13,974	13,138
Fair Values of Firm Commitments		1,031	3,962
Regulatory Assets	[1]	15,884	15,616
Other Current Assets		51,505	59,354
Federal [Member]
Summary Of Significant Accounting Policies [Line Items]
Income Taxes Receivable		0	11,758
State [Member]
Summary Of Significant Accounting Policies [Line Items]
Income Taxes Receivable		$ 9,689	$ 3,961

[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.