Energy Services Accounts Receivable Securitization Facility (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2010
Energy services accounts receivable securitization facility (Additional Textual) [Abstract]
Receivables facility	$ 200
Energy Services [Member]
Energy services accounts receivable securitization facility (Textual) [Abstract]
Sale of trade receivables	836.0	1,134.9	1,147.3
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	286.0	88.0	254.6
Outstanding balance of trade receivables	43.5	52.1
Outstanding balance of trade receivables sold		14.3
Losses on sales of receivables to commercial paper conduit included in interest expenses	1.0	1.2
Losses on sale of receivables to the commercial paper			$ 1.5