Summary Of Significant Accounting Policies (Component Of Other Accruals And Current Liabilities) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Sep. 30, 2012	Sep. 30, 2011
Segment Reporting Information [Line Items]
Accrued Capital Expenditures	$ 86,144	$ 154,960	$ 67,503	$ 125,115
Regulatory Liabilities	16,207		18,289
Reserve for Gas Replacement	(44,485)		(49,795)
Other	26,318		24,350
Total Other Accruals and Current Liabilities	103,582		79,099
Other Accruals [Member]
Segment Reporting Information [Line Items]
Accrued Capital Expenditures	54,339		36,460
Reserve For Gas Replacement [Member]
Segment Reporting Information [Line Items]
Reserve for Gas Replacement	$ 6,718		$ 0