Derivative Instruments - Additional Information (Detail) (USD $)				1 Months Ended					6 Months Ended
	Jun. 30, 2013 Counterparty	May 31, 2013	Dec. 31, 2012	Jun. 30, 2013 Call options [Member] gal	May 31, 2013 Call options [Member] gal	May 31, 2012 Call options [Member] gal	May 31, 2013 Call options [Member] Minimum [Member]	May 31, 2013 Call options [Member] Maximum [Member]	Jun. 30, 2013 Put Option [Member]	Jun. 30, 2013 Put Option [Member] Minimum [Member]	Jun. 30, 2013 Put Option [Member] Maximum [Member]	Jun. 30, 2013 Mark To Market Energy Assets [Member] Call options [Member]	Dec. 31, 2012 Mark To Market Energy Assets [Member] Call options [Member]	Jun. 30, 2013 Designated as Hedging Instrument [Member] Mark To Market Energy Assets [Member] Call options [Member]		Dec. 31, 2012 Designated as Hedging Instrument [Member] Mark To Market Energy Assets [Member] Call options [Member]		Jun. 30, 2013 Designated as Hedging Instrument [Member] Mark To Market Energy Assets [Member] Put Option [Member]		Dec. 31, 2012 Designated as Hedging Instrument [Member] Mark To Market Energy Assets [Member] Put Option [Member]
Derivative [Line Items]
Purchase quantity for propane price cap				1,260,000	630,000	1,260,000
Strike price of put option		0.9750					0.905	0.990		0.8300	0.8600
Payment to purchase put option									$ 120,000
Derivative asset, fair value, net	248,000		210,000											0	[1]	28,000	[1]	105,000	[2]	0	[2]
Payment to purchase call options					72,000	139,000,000
Fair value of call options	64,000											64,000	0
Ineffective portion of this fair value hedge	0
Number of counterparties under master netting agreements	2
Rights to offset accounts receivable	5,800,000		1,200,000
Rights to offset accounts payable	$ 516,000		$ 511,000

[1] We purchased call options for the propane price cap program in May 2012. The call options expired in March 2013.

[2] As a fair value hedge with no ineffective portion, the unrealized gains and losses associated with these put options are recorded in cost of sales, offset by the corresponding change in the value of propane inventory (hedged item), which is also recorded in cost of sales. The amounts in cost of sales offset to zero and the unrealized gains and losses of this call option effectively changed the value of propane inventory.