Derivative Instruments - Additional Information (Detail)	1 Months Ended		12 Months Ended
	Jun. 30, 2013 USD ($) gal	May. 31, 2013 USD ($) $ / gal gal	Dec. 31, 2015 USD ($) dekatherm / d Counterparty $ / gal gal	Dec. 31, 2014 USD ($) Counterparty $ / gal gal	Jun. 30, 2014 $ / gal
Derivative [Line Items]
Other Comprehensive Income Loss Adjustments AOCI Swap Agreements			$ (735,000)
Energy Marketing Contract Liabilities, Current			$ 433,000	$ 1,018,000
Number Of Counterparties With Master Repurchase Agreements | Counterparty			2	2
Accounts Receivable Subject To Master Netting Arrangement				$ 1,600,000
Accounts Payable Subject To Master Netting Arrangement			$ 431,000	1,200,000
Strike price of put option | $ / gal		0.975
Mark-to-market energy assets			$ 153,000	$ 1,055,000
Put Option
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount, Volume | gal			2,500,000	630,000
Payment to purchase call options			$ 143,000	$ 128,000
Cash Received On Derivative Settlement			$ 868,000
Amount paid to purchase put option	$ 120,000
Put Option | Minimum
Derivative [Line Items]
Strike price of put option | $ / gal					0.8300
Put Option | Maximum
Derivative [Line Items]
Strike price of put option | $ / gal					0.8600
Call options
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount, Volume | gal	1,300,000	630,000	1,300,000
Payment to purchase call options		$ 72,000	$ 98,000
Derivative, Gain on Derivative			$ 209,000
Propane Swap Agreement
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount, Volume | gal			2,500,000	630,000
Cash Paid On Derivative Settlement			$ 1,100,000
Mark To Market Energy Assets | Future [Member]
Derivative [Line Items]
Natural Gas Futures Nonmonetary Notional Amount Volume | dekatherm / d			1,410
Energy Marketing Contract Liabilities, Current			$ 109,000
Mark To Market Energy Assets | Put Option
Derivative [Line Items]
Mark-to-market energy assets			152,000	$ 622,000
Mark To Market Energy Assets | Call options
Derivative [Line Items]
Mark-to-market energy assets			0	26,000
Mark-to-market energy liabilities | Future [Member]
Derivative [Line Items]
Energy Marketing Contract Liabilities, Current			109,000
Mark-to-market energy liabilities | Propane Swap Agreement
Derivative [Line Items]
Energy Marketing Contract Liabilities, Current			323,000	$ 735,000
Cash Flow Hedge Derivative Instrument Liabilities at Fair Value			323,000
Derivatives designated as fair value hedges | Mark To Market Energy Assets | Put Option
Derivative [Line Items]
Derivative Asset, Fair Value, Amount Not Offset Against Collateral			$ 152,000
Put Option Strike Price 1 [Member] | Put Option
Derivative [Line Items]
Strike price of put option | $ / gal			0.4950	1.0350
Put Option Strike Price 2 [Member] | Put Option
Derivative [Line Items]
Strike price of put option | $ / gal			0.4888	0.9975
Put Option Strike Price 3 [Member] | Put Option
Derivative [Line Items]
Strike price of put option | $ / gal			0.4500	0.9475
Put Option Strike Price 4 [Member] | Put Option
Derivative [Line Items]
Strike price of put option | $ / gal			0.4200
Strike Price 1 [Member] | Call options
Derivative [Line Items]
Strike price of put option | $ / gal			1.0875
Strike Price 2 [Member] | Call options
Derivative [Line Items]
Strike price of put option | $ / gal			1.0650
Strike Price 1 [Member] | Propane Swap Agreement
Derivative [Line Items]
Strike Price Per Gallon For The Propane Swap Agreements | $ / gal			0.5200	1.1350
Strike Price 2 [Member] | Propane Swap Agreement
Derivative [Line Items]
Strike Price Per Gallon For The Propane Swap Agreements | $ / gal			0.5950	1.0975
Strike Price 3 [Member] | Propane Swap Agreement
Derivative [Line Items]
Strike Price Per Gallon For The Propane Swap Agreements | $ / gal				1.0475