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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 | 9 Months Ended
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Sep. 30, 2019 USD ($) MMBTU MWh gal | Sep. 30, 2018 USD ($) MMBTU MWh gal | Sep. 30, 2019 USD ($) MMBTU MWh gal | Sep. 30, 2018 USD ($) MMBTU MWh gal
Realized gains (losses) |  |  |  |
Gains (losses) | $ (5.6) | $ 8.0 | $ (3.9) | $ 8.9
Natural gas contracts |  |  |  |
Realized gains (losses) |  |  |  |
Gains (losses) | $ (13.2) | $ 0.4 | $ (16.8) | $ (7.1)
Notional sales volumes |  |  |  |
Notional sales volumes | MMBTU | 37.8 | 36.7 | 137.7 | 124.7
Petroleum products contracts |  |  |  |
Realized gains (losses) |  |  |  |
Gains (losses) | $ 0.0 | $ 0.5 | $ 0.0 | $ 1.3
Notional sales volumes |  |  |  |
Notional sales volumes (gallons) | gal | 0.0 | 1.3 | 0.0 | 5.1
FTRs |  |  |  |
Realized gains (losses) |  |  |  |
Gains (losses) | $ 7.6 | $ 7.1 | $ 12.9 | $ 14.7
Notional sales volumes |  |  |  |
Notional sales volumes | MWh | 7.8 | 7.9 | 23.9 | 22.9

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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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