Derivative Instruments - Additional Information (Detail) (USD $)	12 Months Ended	1 Months Ended
	Dec. 31, 2014 Counterparty	Jun. 30, 2013	May 31, 2013 gal	May 31, 2012 gal	Dec. 31, 2013 Counterparty	Jun. 30, 2014	Dec. 31, 2012
Derivative [Line Items]
Other Comprehensive Income Loss Adjustments AOCI Swap Agreements	$ (735,000)
Energy Marketing Contract Liabilities, Current	1,018,000				127,000
Number Of Counterparties With Master Repurchase Agreements	2				2
Accounts Receivable Subject To Master Netting Arrangement	1,600,000				2,800,000
Accounts Payable Subject To Master Netting Arrangement	1,200,000				3,200,000
Strike price of put option			0.975
Mark-to-market energy assets	1,055,000				385,000
Put Option
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount, Volume	630,000
Payment to purchase call options	128,000
Amount paid to purchase put option		120,000
Put Option | Minimum
Derivative [Line Items]
Strike price of put option						0.8300
Put Option | Maximum
Derivative [Line Items]
Strike price of put option						0.8600
Call options
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount, Volume	1,260,000	1,300,000	630,000
Purchase quantity for propane price cap				1,300,000
Payment to purchase call options	98,000		72,000	139,000
Fair value of call options							28,000
Derivative, Gain on Derivative	209,000
Call options | Minimum
Derivative [Line Items]
Strike price of put option							0.905
Call options | Maximum
Derivative [Line Items]
Strike price of put option							0.990
Propane Swap Agreement
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount, Volume	630,000
Mark To Market Energy Assets
Derivative [Line Items]
Mark-to-market energy assets					0
Mark To Market Energy Assets | Forward Contracts
Derivative [Line Items]
Mark-to-market energy assets	407,000				196,000
Mark To Market Energy Assets | CALL OPTION 2 [Member]
Derivative [Line Items]
Mark-to-market energy assets	0				169,000
Mark To Market Energy Assets | Put Option
Derivative [Line Items]
Mark-to-market energy assets	622,000				20,000
Mark To Market Energy Assets | Call options
Derivative [Line Items]
Mark-to-market energy assets	26,000
Mark-to-market energy liabilities | Forward Contracts
Derivative [Line Items]
Energy Marketing Contract Liabilities, Current	283,000				127,000
Mark-to-market energy liabilities | Propane Swap Agreement
Derivative [Line Items]
Energy Marketing Contract Liabilities, Current	$ 735,000				$ 0
Put Option Strike Price 1 [Member] | Put Option
Derivative [Line Items]
Strike price of put option	1.0350
Put Option Strike Price 2 [Member] | Put Option
Derivative [Line Items]
Strike price of put option	0.9975
Put Option Strike Price 3 [Member] | Put Option
Derivative [Line Items]
Strike price of put option	0.9475
Strike Price 1 [Member] | Call options
Derivative [Line Items]
Strike price of put option	1.0875
Strike Price 2 [Member] | Call options
Derivative [Line Items]
Strike price of put option	1.0650
Strike Price 1 [Member] | Propane Swap Agreement
Derivative [Line Items]
Strike Price Per Gallon For The Propane Swap Agreements	1.1350
Strike Price 2 [Member] | Propane Swap Agreement
Derivative [Line Items]
Strike Price Per Gallon For The Propane Swap Agreements	1.0975
Strike Price 3 [Member] | Propane Swap Agreement
Derivative [Line Items]
Strike Price Per Gallon For The Propane Swap Agreements	1.0475