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Derivative Instruments - Additional Information (Detail) gal in Thousands, Mcf in Thousands, $ in Thousands | 3 Months Ended | 12 Months Ended
--- | --- | ---
Mar. 31, 2018 USD ($) $ / gal gal Mcf | Dec. 31, 2017 USD ($) gal
Derivative [Line Items] |  |
Accounts Receivable Subject to Master Netting Arrangement | $ 2,092 | $ 2,391
Derivative, Nonmonetary Notional Amount, Volume | Mcf | 100 |
Energy Marketing Contracts Assets, Current | $ 208 | $ 1,286
Volume settled on hedges | gal |  | 20
Energy Marketing Contract Liabilities, Current | (2,359) | $ (6,247)
Accounts Payable Subject To Master Netting Arrangement | 2,092 | 2,391
Hedging Liability [Member] | Natural Gas Futures [Member] |  |
Derivative [Line Items] |  |
Energy Marketing Contract Liabilities, Current | (1,639) | (469)
Hedging Liability [Member] | Natural Gas Swaps [Member] |  |
Derivative [Line Items] |  |
Energy Marketing Contract Liabilities, Current | (404) | (2)
Designated as Hedging Instrument [Member] | Mark To Market Energy Assets [Member] | Propane Swap Agreement [Member] |  |
Derivative [Line Items] |  |
Energy Marketing Contracts Assets, Current | 204 |
Energy Marketing Contract Liabilities, Current | (16) | 0
Not Designated as Hedging Instrument [Member] | Mark To Market Energy Assets [Member] | Propane Swap Agreement [Member] |  |
Derivative [Line Items] |  |
Energy Marketing Contracts Assets, Current | 4 | 13
Not Designated as Hedging Instrument [Member] | Mark-to-market energy liabilities [Member] | Natural Gas Futures [Member] |  |
Derivative [Line Items] |  |
Energy Marketing Contract Liabilities, Current | $ (300) | $ (5,776)
PESCO [Member] | Natural Gas Futures [Member] |  |
Derivative [Line Items] |  |
Derivative, Nonmonetary Notional Amount, Volume | Mcf | 22,900 |
2017 [Member] |  |
Derivative [Line Items] |  |
Derivative, Nonmonetary Notional Amount, Volume | gal | 2,100 |
2017 [Member] | Natural Gas Swaps [Member] |  |
Derivative [Line Items] |  |
Derivative, Nonmonetary Notional Amount, Volume | Mcf | 702 |
2017 [Member] | Propane Swap Agreement [Member] |  |
Derivative [Line Items] |  |
Derivative, Nonmonetary Notional Amount, Volume | gal |  | 7,700
Derivative, Cash Received on Hedge | $ 3 |
2017 [Member] | Strike Price 4 [Member] | Propane Swap Agreement [Member] |  |
Derivative [Line Items] |  |
Strike Price Per Gallon For The Propane Swap Agreements | $ / gal | 0.5900 |
2018 [Member] | Propane Swap Agreement [Member] |  |
Derivative [Line Items] |  |
Derivative, Cash Received on Hedge | $ 464 |
Gross [Member] |  |
Derivative [Line Items] |  |
Accounts Receivable Subject to Master Netting Arrangement | 6,555 | $ 8,283
Accounts Payable Subject To Master Netting Arrangement | 13,912 | 16,643
Net [Member] |  |
Derivative [Line Items] |  |
Accounts Receivable Subject to Master Netting Arrangement | 4,463 | 5,892
Accounts Payable Subject To Master Netting Arrangement | $ 11,820 | $ 14,252

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- Definition Accounts Payable Subject To Master Netting Arrangement + References No definition available. + Details
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- Definition Accounts Receivable Subject to Master Netting Arrangement + References No definition available. + Details
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- Definition Strike Price Per Gallon For The Propane Swap Agreements + References No definition available. + Details
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- Definition Volume settled on hedges + References No definition available. + Details
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- Definition The amount of cash received during the period on settlement of a hedge. + References No definition available. + Details
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- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details
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- Definition Nominal volume used to calculate payments on a derivative instrument. + References No definition available. + Details
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- Definition Current liabilities attributable to energy marketing activities (trading activities). Current energy marketing (trading activities) are when entities engage in both financial and physical trading to increase profits, manage their commodity price risk and enhance system reliability. They may trade electricity, coal, natural gas and oil. These entities typically use a variety of financial instruments, including forward contracts, options and swaps. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.20) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
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- Definition Carrying amount as of the balance sheet date of the asset arising from energy trading activities that involves the purchase and sale of energy under forward contracts at fixed and variable prices and the buying and selling of financial energy contracts that include exchange futures and options and over the counter options and swaps, which are expected to be converted into cash or otherwise disposed of within a year or the normal operating cycle, if longer. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.2) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
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