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DERIVATIVE INSTRUMENTS - DERIVATIVE ASSETS AND LIABILITIES (Details) - USD ($) $ in Millions | Mar. 31, 2017 | Dec. 31, 2016
--- | --- | ---
Derivative Asset |  |
Other current derivative assets | $ 14.1 | $ 38.2
Other long-term derivative assets | 0.4 | 3.4
Derivative asset | 14.5 | 41.6
Derivative Liability |  |
Other current derivative liabilities | 2.8 | 1.9
Other long-term derivative liabilities | 1.4 | 0.5
Derivative liability | 4.2 | 2.4
Natural gas contracts |  |
Derivative Asset |  |
Other current derivative assets | 11.4 | 31.4
Other long-term derivative assets | 0.4 | 2.9
Derivative Liability |  |
Other current derivative liabilities | 0.7 | 0.4
Other long-term derivative liabilities | 0.2 | 0.0
Petroleum products contracts |  |
Derivative Asset |  |
Other current derivative assets | 0.0 | 0.2
Derivative Liability |  |
Other current derivative liabilities | 0.3 | 0.1
FTRs |  |
Derivative Asset |  |
Other current derivative assets | 1.7 | 5.1
Derivative Liability |  |
Other current derivative liabilities | 0.0 | 0.0
Coal contracts |  |
Derivative Asset |  |
Other current derivative assets | 1.0 | 1.5
Other long-term derivative assets | 0.0 | 0.5
Derivative Liability |  |
Other current derivative liabilities | 1.8 | 1.4
Other long-term derivative liabilities | $ 1.2 | $ 0.5

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