Business Segment Information (Narrative) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Dec. 31, 2012
Utility [Member]
Segment Reporting Information [Line Items]
Increase in segment assets	$ 29.9
Pipeline And Storage [Member]
Segment Reporting Information [Line Items]
Increase in segment assets	29.0
Exploration And Production [Member]
Segment Reporting Information [Line Items]
Increase in segment assets	98.3
All Other [Member]
Segment Reporting Information [Line Items]
Increase in segment assets	$ 16.4