Disclosures About Derivative Instruments and Hedging Activities (Details Textual) In Millions, unless otherwise specified				6 Months Ended				3 Months Ended
	Mar. 31, 2013 USD ($)	Sep. 30, 2012 USD ($)	Mar. 31, 2012 USD ($)	Mar. 31, 2013 Foreign Currency [Member] USD ($)	Mar. 31, 2012 Foreign Currency [Member] USD ($)	Mar. 31, 2013 Interest Rate Swaps [Member] EUR (€)	Mar. 31, 2012 Interest Rate Swaps [Member] EUR (€)	Mar. 31, 2012 Interest Rate Protection Agreements [Member] USD ($)	Mar. 31, 2013 Interest Rate Protection Agreements [Member] USD ($)	Mar. 31, 2012 Net Investment Hedges [Member] EUR (€)	Mar. 31, 2013 LPG (millions of gallons) [Member]	Mar. 31, 2013 Natural Gas (millions of dekatherms) [Member]	Mar. 31, 2013 Electricity (millions of kilowatt-hours) [Member] Forward Purchase Contracts [Member]	Mar. 31, 2013 Electricity (millions of kilowatt-hours) [Member] Forward Sales Contracts [Member]	Mar. 31, 2013 Electric transmission congestion - Electric Utility [Member] kWh	Mar. 31, 2012 Electric transmission congestion - Electric Utility [Member] kWh	Mar. 31, 2013 Gas Utility [Member] DTH	Mar. 31, 2012 Gas Utility [Member] DTH	Mar. 31, 2013 Midstream & Marketing [Member] Electric transmission congestion (excluding Electric Utility) [Member] kWh	Mar. 31, 2012 Midstream & Marketing [Member] Electric transmission congestion (excluding Electric Utility) [Member] kWh	Mar. 31, 2013 Electric Utility - Forward Contract [Member] USD ($) kWh	Mar. 31, 2012 Electric Utility - Forward Contract [Member] USD ($) kWh	Mar. 31, 2013 Midstream and Marketing Natural Gas [Member] DTH	Mar. 31, 2012 Midstream and Marketing Natural Gas [Member] DTH	Mar. 31, 2013 Midstream and Marketing Propane Storage [Member] gal	Mar. 31, 2012 Midstream and Marketing Propane Storage [Member] gal
Disclosures About Derivative Instruments Hedging Activities (Textual) [Abstract]
Notional amount (in units)															47,500,000	52,200,000	10,000,000	11,600,000	261,000,000	355,800,000	403,200,000	707,400,000	400,000	4,600,000	0	1,200,000
Maximum length of time hedged in price risk cash flow hedges (in months)				24 months							20 months	43 months	30 months	11 months			12 months		2 months		14 months
Derivative Liability, Fair Value, Gross Liability	$ 76.3		$ 136.5																		$ 5.5	$ 14.7
Underlying variable rate debt				92.7	63.9	441.2	442.6	173.0	173.0	14.5
Weighted Average Length if Time Hedged (in months)				13 months							7 months	11 months	9 months	5 months
Recorded loss amount included in Other Income, Net								0.7
Minimum approximate range of estimated dollar-denominated purchases of LPG (as a percent)				15.00%
Maximum approximate range of estimated dollar-denominated purchases of LPG (as a percent)				30.00%
Disclosures About Derivative Instruments Hedging Activities (Additional Textual) [Abstract]
Net losses associated with commodity price risk hedges expected to be reclassified into earnings during the next twelve months	5.9
Amount of net losses associated with interest rate hedges to be reclassified with interest rate hedges during the next 12 months	1.2
Amount of net gains associated with currency rate risk to be reclassified into earnings during the next 12 months	1.5
Restricted Cash in brokerage accounts	$ 2.8	$ 3.0	$ 16.8