CONTINGENCIES AND COMMITMENTS (Nuclear Insurance) (Details) $ in Millions	6 Months Ended	9 Months Ended
	Jun. 30, 2018 nuclear_generating_unit	Sep. 30, 2018 USD ($)
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