Derivative Instruments - Effects of Gains and Losses from Derivative Instruments (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on derivatives	$ (352)	$ 18	$ 116
Cost of Sales [Member] | Derivatives designated as fair value hedges [Member] | Put Option [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on derivatives	27
Cost of Sales [Member] | Derivatives not designated as hedging instruments [Member] | Put Option [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on derivatives			(168)
Propane Inventory [Member] | Derivatives designated as fair value hedges [Member] | Put/Call Option [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on derivatives	(40)	(23)
Revenue [Member] | Forward Contracts [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on derivatives	(339)	41	284
Revenue [Member] | Derivatives not designated as hedging instruments [Member] | Forward Contracts [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on derivatives	$ (339)	$ 41	$ 284