FAIR VALUE MEASUREMENTS (Schedule of Activity for Debt and Equity Securities) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Fair Value Disclosures [Abstract]
Proceeds from sales and maturities of nuclear decommissioning trust investments	$ 308	$ 324	$ 802	$ 794
Gross realized gains on securities	11	13	48	42
Gross realized losses on securities	$ (5)	$ (3)	$ (9)	$ (8)