Summary Of Significant Accounting Policies (Schedule Of Depreciable Plant By Segment) (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2012	Sep. 30, 2011
Summary Of Significant Accounting Policies [Line Items]
Depreciable plant	$ 6,171,894	$ 5,127,614
Utility [Member]
Summary Of Significant Accounting Policies [Line Items]
Depreciable plant	1,737,645	1,695,702
Pipeline And Storage [Member]
Summary Of Significant Accounting Policies [Line Items]
Depreciable plant	1,406,433	1,260,301
Exploration And Production [Member]
Summary Of Significant Accounting Policies [Line Items]
Depreciable plant	2,828,358	2,042,225
Energy Marketing [Member]
Summary Of Significant Accounting Policies [Line Items]
Depreciable plant	2,865	2,095
All Other And Corporate [Member]
Summary Of Significant Accounting Policies [Line Items]
Depreciable plant	$ 196,593	$ 127,291