Derivative Instruments - Additional Information (Detail) (USD $)	9 Months Ended			9 Months Ended	1 Months Ended		9 Months Ended
	Sep. 30, 2014 Counterparty	Dec. 31, 2013 Counterparty	May 31, 2013	Sep. 30, 2014 Propane Swap Agreement [Member] gal	Jun. 30, 2013 Call options [Member] gal	May 31, 2013 Call options [Member] gal	Sep. 30, 2014 Call options [Member] gal	Sep. 30, 2014 Put Option [Member] gal	Sep. 30, 2013 Put Option [Member]	Sep. 30, 2013 Put Option [Member] Minimum [Member]	Sep. 30, 2013 Put Option [Member] Maximum [Member]	Sep. 30, 2014 Mark To Market Energy Assets [Member] Propane Swap Agreement [Member]	Sep. 30, 2014 Mark To Market Energy Assets [Member] Call options [Member]	Dec. 31, 2013 Mark To Market Energy Assets [Member] Call options [Member]	Sep. 30, 2014 Mark To Market Energy Liabilities [Member] Propane Swap Agreement [Member]	Sep. 30, 2014 Designated as Hedging Instrument [Member] Mark To Market Energy Assets [Member] Put Option [Member]	Dec. 31, 2013 Designated as Hedging Instrument [Member] Mark To Market Energy Assets [Member] Put Option [Member]	Sep. 30, 2014 Strike Price 1 [Member] Propane Swap Agreement [Member]	Sep. 30, 2014 Strike Price 2 [Member] Propane Swap Agreement [Member]	Sep. 30, 2014 Strike Price 3 [Member] Propane Swap Agreement [Member]	Sep. 30, 2014 Put Option Strike Price 1 [Member] Put Option [Member]	Sep. 30, 2014 Put Option Strike Price 2 [Member] Put Option [Member]	Sep. 30, 2014 Put Option Strike Price 3 [Member] Put Option [Member]
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount, Volume					1,300,000	630,000	630,000	630,000
Gallons Of Propane Associated With The Swap Agreement				630,000
Cash Flow Hedge Derivative Instrument Assets at Fair Value												$ 13,000	$ 35,000
Cash Flow Hedge Derivative Instrument Liabilities at Fair Value															60,000
Strike Price Per Gallon For The Propane Swap Agreements																		1.1350	1.0975	1.0475
Document Period End Date	Sep. 30, 2014
Strike price of put option			0.9750				1.0875			0.8300	0.8600										0.9475	0.9975	1.0350
Payment to purchase put option								128,000	120,000
Derivative asset, fair value, net																56,000	20,000
Payment to purchase call options						72,000	52,000
Fair value of call options													0	169,000
Number of counterparties under master netting agreements	2	2
Rights to offset accounts receivable	2,200,000	2,800,000
Rights to offset accounts payable	1,600,000	3,155,000
Gain (Loss) on Sale of Derivatives							$ 209,000