Derivative Instruments - Additional Information (Detail) (USD $)				1 Months Ended			1 Months Ended
	Dec. 31, 2013 Counterparty	May 31, 2013	Dec. 31, 2012 Counterparty	Jun. 30, 2013 Put Option	Jun. 30, 2013 Put Option Minimum	Jun. 30, 2013 Put Option Maximum	Jun. 30, 2013 Call options gal	May 31, 2013 Call options gal	May 31, 2012 Call options gal	Dec. 31, 2012 Call options	Dec. 31, 2013 Call options Minimum	Dec. 31, 2013 Call options Maximum	Dec. 31, 2013 Mark To Market Energy Assets Forward Contracts	Dec. 31, 2012 Mark To Market Energy Assets Forward Contracts	Dec. 31, 2012 Mark To Market Energy Assets Put Option	Dec. 31, 2013 Mark To Market Energy Assets Call options	Dec. 31, 2012 Mark To Market Energy Assets Call options	Dec. 31, 2013 Derivatives designated as fair value hedges Mark To Market Energy Assets Put Option	Dec. 31, 2013 Derivatives designated as fair value hedges Mark To Market Energy Assets Call options	Dec. 31, 2012 Derivatives designated as fair value hedges Mark To Market Energy Assets Call options
Derivative [Line Items]
Number Of Counterparties With Master Repurchase Agreements	2		2
Accounts Receivable Subject To Master Netting Arrangement	$ 2,800,000		$ 1,200,000
Accounts Payable Subject To Master Netting Arrangement	3,200,000		511,000
Derivatives asset not designated as hedging instruments													196,000	182,000			0
Purchase quantity for propane price cap							1,300,000	630,000	1,260,000
Strike price of put option		0.9750			0.8300	0.8600					0.905	0.990
Payment to purchase call options								72,000	139,000
Fair value of call options	169,000									28,000						169,000
Amount paid to purchase put option				120,000
Derivative Asset Fair Value Net	$ 385,000		$ 210,000												$ 0			$ 20,000	$ 0	$ 28,000