Derivative Instruments - Additional Information (Detail) (USD $)	3 Months Ended	12 Months Ended
	Mar. 31, 2015 gal	Dec. 31, 2014 gal
Propane Swap Agreement [Member]
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount, Volume	630,000	630,000
Strike Price Per Gallon For The Propane Swap Agreements	0.595
Cash Paid On Derivative Settlement	$ 1,057,000
Other Comprehensive Income Loss Adjustments AOCI Swap Agreements		735,000
Call options [Member]
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount, Volume		1,260,000
Payments for Derivative Instrument, Financing Activities		98,000
Put Option [Member]
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount, Volume	630,000	630,000
Derivative, Price Risk Option Strike Price	0.4950
Payments for Derivative Instrument, Financing Activities	43,000	128,000
Cash Received On Derivative Settlement	868,000
Forward Contracts [Member]
Derivative [Line Items]
Number Of Counterparties With Master Repurchase Agreements	2	2
Accounts Receivable Subject To Master Netting Arrangement	1,900,000	1,600,000
Accounts Payable Subject To Master Netting Arrangement	2,300,000	1,235,000
Mark To Market Energy Liabilities [Member] | Propane Swap Agreement [Member]
Derivative [Line Items]
Cash Flow Hedge Derivative Instrument Liabilities at Fair Value	12,000
Designated as Hedging Instrument [Member] | Mark To Market Energy Assets [Member] | Put Option [Member]
Derivative [Line Items]
Derivative Asset, Fair Value, Amount Not Offset Against Collateral	$ 38,000
Strike Price 1 [Member] | Propane Swap Agreement [Member]
Derivative [Line Items]
Strike Price Per Gallon For The Propane Swap Agreements		1.1350
Strike Price 2 [Member] | Propane Swap Agreement [Member]
Derivative [Line Items]
Strike Price Per Gallon For The Propane Swap Agreements		1.0975
Strike Price 3 [Member] | Propane Swap Agreement [Member]
Derivative [Line Items]
Strike Price Per Gallon For The Propane Swap Agreements		1.0475
Put Option Strike Price 1 [Member] | Put Option [Member]
Derivative [Line Items]
Derivative, Price Risk Option Strike Price		1.0350
Put Option Strike Price 2 [Member] | Put Option [Member]
Derivative [Line Items]
Derivative, Price Risk Option Strike Price		0.9975
Put Option Strike Price 3 [Member] | Put Option [Member]
Derivative [Line Items]
Derivative, Price Risk Option Strike Price		0.9475
Strike Price 1 [Member] | Call options [Member]
Derivative [Line Items]
Derivative, Price Risk Option Strike Price	1.0875
Strike Price 2 [Member] | Call options [Member]
Derivative [Line Items]
Derivative, Price Risk Option Strike Price	1.0650