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DERIVATIVE INSTRUMENTS - GAINS (LOSSES) AND NOTIONAL VOLUMES (Details) MWh in Millions, MMBTU in Millions, $ in Millions | 3 Months Ended | 9 Months Ended
--- | --- | ---
Sep. 30, 2021 USD ($) MWh MMBTU | Sep. 30, 2020 USD ($) MWh MMBTU | Sep. 30, 2021 USD ($) MWh MMBTU | Sep. 30, 2020 USD ($) MWh MMBTU
Realized gains (losses) |  |  |  |
Gains (losses) | $ 44.2 | $ (10.9) | $ 53.8 | $ (50.8)
Natural gas contracts |  |  |  |
Notional sales volumes |  |  |  |
Notional sales volumes | MMBTU | 39.4 | 36.2 | 147.1 | 139.3
Realized gains (losses) |  |  |  |
Gains (losses) | $ 41.2 | $ (12.0) | $ 38.5 | $ (53.9)
FTRs |  |  |  |
Notional sales volumes |  |  |  |
Notional sales volumes | MWh | 6.3 | 8.3 | 22.1 | 22.7
Realized gains (losses) |  |  |  |
Gains (losses) | $ 3.0 | $ 1.1 | $ 15.3 | $ 3.1

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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=125515794&loc=SL5618551-113959 + Details
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