SUMMARY OF BUSINESS AND BASIS OF PRESENTATION - Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Jan. 01, 2018
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Stockholders' equity beginning of period	$ 906	$ 746	$ 770
Pension and other postretirement adjustment, net	2	(19)	5
Net increase in other comprehensive income	2	(12)	5
Stockholders' equity end of period	1,013	906	746
Accumulated Other Comprehensive Income (Loss)
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Stockholders' equity beginning of period	120	132	127
Stockholders' equity end of period	$ 122	$ 120	$ 132
Accounting Standards Update 2018-02
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Reclassification of stranded tax effects (ASU 2018-02)				$ 0
Accounting Standards Update 2018-02 | Accumulated Other Comprehensive Income (Loss)
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Reclassification of stranded tax effects (ASU 2018-02)				$ 7