Derivative Instruments - Additional Information (Detail) (USD $)		1 Months Ended	12 Months Ended	1 Months Ended
	Mar. 31, 2012	Aug. 30, 2011 Put Option [Member] gal	Dec. 31, 2012 Put Option [Member]	May 31, 2012 Call options [Member] gal	Dec. 31, 2012 Call options [Member]	Dec. 31, 2012 Call options [Member] Minimum [Member]	Dec. 31, 2012 Call options [Member] Maximum [Member]
Derivative [Line Items]
Purchase quantity for propane price cap		630,000		1,260,000
Strike price of put option	1.445		1.445			0.905	0.990
Payment to purchase call options				$ 139,000
Fair value of call options					28,000
Ineffective portion of this fair value hedge					0
Difference between market price and strike price			118,000
Amount paid to purchase put option			$ 91,000