QUARTERLY OPERATIONS Quarterly Operations (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Quarterly Financial Information Disclosure [Abstract]
Asset Impairment Charges									$ 0	$ 12	$ 0
Operating revenues	$ 145	$ 132	$ 126	$ 144	$ 146	$ 135	$ 139	$ 158	547	578	574
Operating income	52	55	52	58	62	41	52	76	217	231	203
Net income (loss)	$ 44	$ 44	$ 43	$ 40	$ 33	$ 475	$ 31	$ 50	$ 171	$ 589	$ 108