Business Segment Information (Narrative) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014 segment	Jun. 30, 2013
Segment Reporting Information [Line Items]
Number of reportable segments			5
Segment Profit: Net Income (Loss)	$ 64,520	$ 58,495	$ 241,983	$ 212,159
Energy Marketing [Member]
Segment Reporting Information [Line Items]
Segment Profit: Net Income (Loss)	602	963	5,971	5,741
Energy Marketing [Member] | Unbilled Revenues [Member]
Segment Reporting Information [Line Items]
Revenue from External Customers	(24,000)		9,700
Energy Marketing [Member] | Margin [Member]
Segment Reporting Information [Line Items]
Segment Profit: Net Income (Loss)	$ (500)		$ 300