Disclosures About Derivative Instruments and Hedging Activities - Narrative (Details) In Millions, unless otherwise specified	9 Months Ended			0 Months Ended									0 Months Ended	9 Months Ended			0 Months Ended			0 Months Ended
	Jun. 30, 2014 USD ($)	Sep. 30, 2013 USD ($)	Jun. 30, 2013 USD ($)	Jun. 30, 2014 LPG (millions of gallons)	Jun. 30, 2014 LPG (millions of gallons) gal	Jun. 30, 2013 LPG (millions of gallons) gal	Jun. 30, 2014 Brokerage Accounts USD ($)	Jun. 30, 2013 Brokerage Accounts USD ($)	Jun. 30, 2014 Interest Rate Swaps EUR (€)	Jun. 30, 2013 Interest Rate Swaps EUR (€)	Jun. 30, 2014 Interest Rate Protection Agreements USD ($)	Jun. 30, 2013 Interest Rate Protection Agreements USD ($)	Jun. 30, 2014 Foreign Currency	Jun. 30, 2014 Foreign Currency USD ($)	Jun. 30, 2013 Foreign Currency USD ($)	Jun. 30, 2014 Cross Currency Interest Rate Contract USD ($)	Jun. 30, 2014 Gas Utility	Jun. 30, 2014 Gas Utility DTH	Jun. 30, 2013 Gas Utility DTH	Jun. 30, 2014 Electric Utility	Jun. 30, 2014 Electric Utility USD ($) kWh	Jun. 30, 2013 Electric Utility USD ($) kWh	Jun. 30, 2014 Midstream & Marketing Electric transmission congestion - Electric Utility kWh	Jun. 30, 2013 Midstream & Marketing Electric transmission congestion - Electric Utility kWh	Jun. 30, 2014 Midstream & Marketing Electric transmission congestion (excluding Electric Utility) kWh	Jun. 30, 2013 Midstream & Marketing Electric transmission congestion (excluding Electric Utility) kWh	Jun. 30, 2014 Midstream & Marketing Electricity (millions of kilowatt-hours) Forward Purchase Contracts kWh	Jun. 30, 2013 Midstream & Marketing Electricity (millions of kilowatt-hours) Forward Purchase Contracts kWh	Jun. 30, 2014 Midstream & Marketing Electricity (millions of kilowatt-hours) Forward Sales Contracts kWh	Jun. 30, 2013 Midstream & Marketing Electricity (millions of kilowatt-hours) Forward Sales Contracts kWh	Jun. 30, 2014 Midstream & Marketing Propane Storage (millions of dekatherms) Forward Sales Contracts gal	Jun. 30, 2013 Midstream & Marketing Propane Storage (millions of dekatherms) Forward Sales Contracts gal	Jun. 30, 2014 Midstream & Marketing Gas Utility Natural Gas Forward Purchase Contracts DTH	Jun. 30, 2013 Midstream & Marketing Gas Utility Natural Gas Forward Purchase Contracts DTH	Jun. 30, 2014 Midstream & Marketing Natural Gas Storage Forward Sales Contracts DTH	Jun. 30, 2013 Midstream & Marketing Natural Gas Storage Forward Sales Contracts DTH
Derivative
Outstanding derivative commodity instruments volumes					274,300,000	236,700,000												10,900,000	11,700,000		315,800,000	327,400,000	232,200,000	260,600,000	427,700,000	1,609,200,000	492,500,000	927,200,000	193,200,000	451,000,000	2,900,000	1,800,000	83,000,000	19,400,000	500,000	2,700,000
Maximum Length of Time Hedged in Price Risk Cash Flow Hedges				21 months									33 months				9 months			11 months
Derivative Liability, Fair Value, Gross Liability	$ 61.3	$ 57.5	$ 87.1																		$ 0.8	$ (6.1)
Weighted Average Length of Time Hedged in Price Risk Cash Flow Hedge				6 months									15 months
Net losses associated with commodity price risk hedges expected to be reclassified into earnings during the next twelve months	4.0
Notional amount									401.1	440.5	0	173.0		219.8	170.3	52.0
Amount of net losses associated with interest rate hedges to be reclassified with interest rate hedges during the next 12 months	2.7
Minimum Approximate Range of Estimated Purchases of Product														15.00%
Maximum approximate range of estimated dollar-denominated purchases of LPG (as a percent)														30.00%
Amount of net gains associated with currency rate risk to be reclassified into earnings during the next 12 months	3.6
Restricted cash	5.9	8.3	6.0				5.9	6.0
Derivative Instruments, Loss Reclassified from Accumulated OCI into Income, Effective Portion	$ 0