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DERIVATIVE INSTRUMENTS (Schedule of Notional Amounts of Outstanding Derivatives) (Details) gal in Millions, MMcf in Millions | Jun. 30, 2019 gal MMcf | Dec. 31, 2018 gal MMcf
--- | --- | ---
Natural Gas [Member] |  |
Derivative [Line Items] |  |
Investment Contract Volume | MMcf | 9.0 | 1.8
Diesel [Member] |  |
Derivative [Line Items] |  |
Investment Contract Volume | gal | 5.0 | 11.0

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- Details
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