FAIR VALUE MEASUREMENTS (Schedule of Activity for Debt and Equity Securities) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Fair Value Disclosures [Abstract]
Proceeds from sales and maturities of nuclear decommissioning trust investments	$ 319	$ 249	$ 1,121	$ 1,043
Gross realized gains on securities	3	8	51	50
Gross realized losses on securities	$ (5)	$ 0	$ (14)	$ (8)