Commitments and Contingencies (Details Textual) (Details) (USD $) In Millions, unless otherwise specified	1 Months Ended	12 Months Ended												12 Months Ended
	Jul. 31, 2011 Customer	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2012 Gas Utility [Member]	Sep. 30, 2012 Midstream and Marketing [Member]	Sep. 30, 2012 Partnership [Member]	Sep. 30, 2008 Partnership [Member] lb	Sep. 30, 2012 CPG MGP Properties [Member]	Sep. 30, 2012 PNG MGP Properties [Member]	Jun. 30, 2006 Key Span [Member]	Jun. 30, 2004 Key Span [Member]	Dec. 31, 2010 Antargaz Competition Authority [Member]	Sep. 30, 2012 Environmental Issue [Member]	Sep. 30, 2012 Minimum [Member]	Sep. 30, 2012 Maximum [Member]	Sep. 30, 2012 Maximum [Member] International Propane [Member] Partnership [Member]
Commitments and Contingencies [Line Items]
Aggregate rental expense for leases		$ 77.9	$ 69.8	$ 70.6
Term of contracts					1 year	2 years	4 years										4 years
Contract Terms, Subject to Annual Price And Quantity Adjustments (in years)															1 year	3 years
Environmental expenditures									1.8	1.1
Accrued liabilities for environmental investigation and remediation costs related to CPG-COA and PNG-COA		15.0	17.9
Base Year for Determination of Investigation and Remediation Cost (in years)														5 years
Approximate remediation cost spent by claimant												2.3
Environmental exit cost anticipated by claimant												11
Percentage of responsible for cleanup cost												50.00%
Environmental exit cost based on third party estimate											10
Additional environment exit cost based on claimant estimate											20
Amount of propane in cylinders being sold								17
Reduced amount of propane in cylinders being sold								15
Number of residential customer (in customers)	400
Reversal of Competition Authority Matter Accrual													$ 9.4