QUARTERLY OPERATIONS Quarterly Operations (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Quarterly Financial Information Disclosure [Abstract]
Asset Impairment Charges									$ 12	$ 0	$ 389
Operating revenues	$ 146	$ 135	$ 139	$ 158	$ 154	$ 137	$ 134	$ 149	578	574	480
Operating income	62	41	52	76	56	41	42	64	231	203	(266)
Net income (loss)	$ 33	$ 475	$ 31	$ 50	$ 29	$ 23	$ 22	$ 34	$ 589	$ 108	$ (45)