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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, 2017 USD ($) MMBTU MWh gal | Mar. 31, 2016 USD ($) MMBTU MWh gal
Realized Gain (Loss) on Derivatives, Net |  |
Gains (Losses) | $ 2.2 | $ (31.6)
Natural gas contracts |  |
Realized Gain (Loss) on Derivatives, Net |  |
Gains (Losses) | $ (0.3) | $ (33.5)
Notional Sales Volumes |  |
Notional sales volumes (Dth or MWh) | MMBTU | 34.1 | 50.1
Petroleum products contracts |  |
Realized Gain (Loss) on Derivatives, Net |  |
Gains (Losses) | $ (0.5) | $ (1.1)
Notional Sales Volumes |  |
Notional sales volumes (gallons) | gal | 4.9 | 3.0
FTRs |  |
Realized Gain (Loss) on Derivatives, Net |  |
Gains (Losses) | $ 3.0 | $ 3.0
Notional Sales Volumes |  |
Notional sales volumes (Dth or MWh) | MWh | 9.2 | 7.6

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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/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 4A -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=64837297&loc=SL5618551-113959 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 4C -Subparagraph (a),(c),(d),(e) -URI http://asc.fasb.org/extlink&oid=64837297&loc=SL5624171-113959 + Details
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