CONTINGENCIES AND COMMITMENTS (Nuclear Insurance) (Details) $ in Millions	6 Months Ended
	Jun. 30, 2018 USD ($) nuclear_generating_unit
Long-term Purchase Commitment [Line Items]
Number of nuclear generating units (nuclear generating unit) | nuclear_generating_unit	2
Nuclear Electric Insurance Limited
Long-term Purchase Commitment [Line Items]
Potential premium obligation	$ 47
European Mutual Association for Nuclear Insurance
Long-term Purchase Commitment [Line Items]
Potential premium obligation	$ 3