Energy Services Accounts Receivable Securitization Facility (Details) (USD $) In Millions	12 Months Ended
	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2009
Energy services accounts receivable securitization facility (Additional Textual) [Abstract]
Receivables facility	$ 200
Energy Services Funding Corporation [Member]
Energy services accounts receivable securitization facility (Textual) [Abstract]
Sale of undivided interests in its trade receivables to the commercial paper conduit	88.0	254.6	596.9
Outstanding balance of trade receivables	52.1	44.0
Outstanding balance of trade receivables sold	14.3	12.1
Losses on sales of receivables to commercial paper conduit included in interest expenses	1.2
Losses on sale of receivables to the commercial paper		1.5	2.3
Energy Services [Member]
Energy services accounts receivable securitization facility (Textual) [Abstract]
Sale of trade receivables	$ 1,134.9	$ 1,147.3	$ 1,247.1