Derivative Instruments - Effects of Gains and Losses from Derivative Instruments (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on derivatives	$ 1,084us-gaap_UnrealizedGainLossOnDerivatives	$ 1,313us-gaap_UnrealizedGainLossOnDerivatives	$ 2,343us-gaap_UnrealizedGainLossOnDerivatives
Call options
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, Gain on Derivative	209
Revenue \| Derivatives not designated as hedging instruments \| Forward Contracts
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, Gain on Derivative	1,423	1,127	2,695
Gain (Loss) on derivatives	57	217	(339)
Cost of Sales \| Derivatives designated as fair value hedges \| Put/Call Option
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, Gain (Loss) on Derivative, Net	235	(28)	27
Cost of Sales \| Derivatives designated as fair value hedges \| Call options
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, Gain (Loss) on Derivative, Net	(17)	0	0
Cost of Sales \| Derivatives designated as fair value hedges \| Propane Swap Agreement
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, Gain (Loss) on Derivative, Net	(341)	0	0
Cost of Sales \| Derivatives not designated as hedging instruments \| Call options
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, Gain on Derivative	0	97	0
Cost of Sales \| Derivatives not designated as hedging instruments \| Propane Swap Agreement
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, Gain on Derivative		0	0
Derivative, Gain (Loss) on Derivative, Net	(735)
Propane Inventory \| Derivatives designated as fair value hedges \| Put/Call Option
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on derivatives	517	(100)	(40)
Other Comprehensive Income (Loss) [Member] \| Derivatives designated as fair value hedges \| Call options
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on derivatives	$ (55)	$ 0	$ 0

Amount of increase (decrease) in the fair value of derivatives recognized in the income statement.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 815

-SubTopic 10

-Section 50

-Paragraph 4A

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=35706170&loc=SL5618551-113959

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 815

-SubTopic 10

-Section 50

-Paragraph 4C

-Subparagraph (a),(c),(d),(e)

-URI http://asc.fasb.org/extlink&oid=35706170&loc=SL5624171-113959

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Amount of increase in the fair value of derivatives recognized in the income statement.

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The net change in the difference between the fair value and the carrying value, or in the comparative fair values, of derivative instruments, including options, swaps, futures, and forward contracts, held at each balance sheet date, that was included in earnings for the period.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 28

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3602-108585

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