Disclosures About Derivative Instruments and Hedging Activities (Details)	Jun. 30, 2011 Gallons	Jun. 30, 2010 Gallons
LPG [Member]
Outstanding derivative commodity instruments volumes
Outstanding derivative commodity instruments volumes	145,000,000	150,500,000
Natural Gas [Member]
Outstanding derivative commodity instruments volumes
Outstanding derivative commodity instruments volumes	21,200,000	33,300,000
Electricity (millions of kilowatt-hours)
Outstanding derivative commodity instruments volumes
Outstanding derivative commodity instruments volumes	1,200,800,000	928,000,000