Disclosures About Derivative Instruments and Hedging Activities (Details Textual) In Millions, unless otherwise specified				3 Months Ended
	Dec. 31, 2012 USD ($)	Sep. 30, 2012 USD ($)	Dec. 31, 2011 USD ($)	Dec. 31, 2012 Foreign Currency [Member] USD ($)	Jun. 30, 2011 Foreign Currency [Member] USD ($)	Dec. 31, 2012 Interest Rate Swaps [Member] EUR (€)	Dec. 31, 2011 Interest Rate Swaps [Member] EUR (€)	Dec. 31, 2012 Interest Rate Protection Agreements [Member] USD ($)	Dec. 31, 2011 Interest Rate Protection Agreements [Member] USD ($)	Dec. 31, 2011 Net Investment Hedges [Member] EUR (€)	Dec. 31, 2012 LPG (millions of gallons) [Member]	Dec. 31, 2012 Natural Gas (millions of dekatherms) [Member]	Dec. 31, 2012 Electricity (millions of kilowatt-hours) [Member] Forward Purchase Contracts [Member]	Dec. 31, 2012 Electricity (millions of kilowatt-hours) [Member] Forward Sales Contracts [Member]	Dec. 31, 2012 Electric transmission congestion - Electric Utility [Member] kWh	Dec. 31, 2011 Electric transmission congestion - Electric Utility [Member] kWh	Dec. 31, 2012 Gas Utility [Member] DTH	Dec. 31, 2011 Gas Utility [Member] DTH	Dec. 31, 2012 Midstream & Marketing [Member] Electric transmission congestion (excluding Electric Utility) [Member] kWh	Dec. 31, 2011 Midstream & Marketing [Member] Electric transmission congestion (excluding Electric Utility) [Member] kWh	Dec. 31, 2012 Electric Utility - Forward Contract [Member] USD ($) kWh	Dec. 31, 2011 Electric Utility - Forward Contract [Member] USD ($) kWh	Dec. 31, 2012 Midstream and Marketing Natural Gas [Member] DTH	Dec. 31, 2011 Midstream and Marketing Natural Gas [Member] DTH	Dec. 31, 2012 Midstream and Marketing Propane Storage [Member] gal	Dec. 31, 2011 Midstream and Marketing Propane Storage [Member] gal
Disclosures About Derivative Instruments Hedging Activities (Textual) [Abstract]
Notional amount (in units)															118,200,000	130,000,000	13,000,000	9,100,000	677,500,000	882,100,000	482,300,000	816,000,000	2,400,000	3,900,000	2,000,000	3,500,000
Maximum length of time hedged in price risk cash flow hedges (in months)				27 months							23 months	41 months	33 months	12 months			9 months		5 months		17 months
Derivative Liability, Fair Value, Gross Liability	$ 121.1		$ 130.9																		$ 8.2	$ 13.5
Underlying variable rate debt				120.0	106.0	441.2	442.6	173.0	173.0	14.5
Weighted Average Length if Time Hedged (in months)				12 months							5 months	12 months	9 months	5 months
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	42.4
Amount of net losses associated with interest rate hedges to be reclassified with interest rate hedges during the next 12 months	1.0
Amount of net gains associated with currency rate risk to be reclassified into earnings during the next 12 months	1.1
Restricted Cash in brokerage accounts	$ 6.9	$ 3.0	$ 22.3