Summary Of Significant Accounting Policies (Schedule Of Other Accruals And Current Liabilities) (Details) (USD $) In Thousands, unless otherwise specified	6 Months Ended		12 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Sep. 30, 2012	Sep. 30, 2011
Segment Reporting Information [Line Items]
Accrued Capital Expenditures	$ 77,093	$ 149,550	$ 67,503	$ 125,115
Regulatory Liabilities	11,802		18,289
Reserve for Gas Replacement	(14,443)		(49,795)
Other	21,896		24,350
Total Other Accruals and Current Liabilities	140,056		79,099
Other Accruals [Member]
Segment Reporting Information [Line Items]
Accrued Capital Expenditures	59,395		36,460
Reserve For Gas Replacement [Member]
Segment Reporting Information [Line Items]
Reserve for Gas Replacement	$ 46,963		$ 0