FAIR VALUE MEASUREMENTS 3 (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance at beginning of period	$ 102	$ 95	$ 107	$ 99
Realized and unrealized gains (losses)	(60)	5	(54)	6
Allocated transmission instruments	1	0	1	1
Settlements	(1)	(15)	(12)	(21)
Balance at end of period	42	85	42	85
Change in unrealized gains (losses) relating to instruments still held at period end	45	0	46	0
CRR Auction Rate Per MWh, Minimum	(16)	(6)	(16)	(6)
CRR Auction Rate Per MWh, Maximum	$ 8	$ 12	$ 8	$ 12