FAIR VALUE MEASUREMENTS AND DERIVATIVE INSTRUMENTS (Level 3 Fair Value Measurements) (Details) - Level 3 - Forward Power Contracts $ in Millions	Dec. 31, 2018 USD ($) $ / megawatt_hour	Dec. 31, 2017 USD ($) $ / megawatt_hour
Fair Value Inputs Assets Liabilities Quantitative Information [Line Items]
Derivative Assets \| $	$ 3	$ 3
Derivative Liabilities \| $	$ (2)	$ (1)
Minimum
Fair Value Inputs Assets Liabilities Quantitative Information [Line Items]
Market Price \| $ / megawatt_hour	16.80	17.65
Maximum
Fair Value Inputs Assets Liabilities Quantitative Information [Line Items]
Market Price \| $ / megawatt_hour	47.05	34.60

Fair Value Inputs Assets Liabilities Quantitative Information [Line Items]

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Value of input used to measure net derivative asset (liability).

+ References

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-Publisher FASB
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-SubTopic 10
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Fair value, after the effects of master netting arrangements, of a financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes assets not subject to a master netting arrangement and not elected to be offset.

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Fair value, after the effects of master netting arrangements, of a financial liability or contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes liabilities not subject to a master netting arrangement and not elected to be offset.

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