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Consolidated Statements of Common Stockholders' Equity (Deficit) (FirstEnergy Solutions Corp.) (Parenthetical) - USD ($) $ in Millions | 12 Months Ended
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Dec. 31, 2017 | Dec. 31, 2016 | Dec. 31, 2015
Unrealized gain (loss) on derivative hedges, taxes | $ 4 | $ 3 | $ 1
Unrealized gain (loss) on investment, taxes | 7 | 21 | 4
Pension and OPEB, taxes | (32) | (23) | (44)
FES |  |  |
Unrealized gain (loss) on derivative hedges, taxes | 1 | 0 | (1)
Unrealized gain (loss) on investment, taxes | 10 | 20 | (4)
Pension and OPEB, taxes | $ (5) | $ (5) | $ (2)

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