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DERIVATIVE INSTRUMENTS - GAINS (LOSSES) AND NOTIONAL VOLUMES (Details) gal in Millions, MWh in Millions, MMBTU in Millions, $ in Millions | 3 Months Ended
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Mar. 31, 2019 USD ($) MMBTU MWh gal | Mar. 31, 2018 USD ($) MMBTU MWh gal
Realized Gain (Loss) on Derivatives, Net |  |
Gains (Losses) | $ 1.8 | $ (1.0)
Natural gas contracts |  |
Realized Gain (Loss) on Derivatives, Net |  |
Gains (Losses) | $ (0.5) | $ (5.2)
Notional Sales Volumes |  |
Notional sales volumes | MMBTU | 56.1 | 48.1
Petroleum products contracts |  |
Realized Gain (Loss) on Derivatives, Net |  |
Gains (Losses) | $ 0.0 | $ 0.5
Notional Sales Volumes |  |
Notional sales volumes (gallons) | gal | 0.0 | 2.1
FTRs |  |
Realized Gain (Loss) on Derivatives, Net |  |
Gains (Losses) | $ 2.3 | $ 3.7
Notional Sales Volumes |  |
Notional sales volumes | MWh | 8.1 | 8.2

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- Definition Amount of increase (decrease) in the fair value of derivatives recognized in the income statement. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 4A -Subparagraph (b)(1) -URI http://asc.fasb.org/extlink&oid=109980867&loc=SL5618551-113959 + Details
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