PENSION AND POSTRETIREMENT BENEFIT PLANS - Cost (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Pension Benefits
Net periodic benefit costs:
Service cost—benefits earned during the period	$ 1	$ 1	$ 1
Interest cost on projected benefit obligation	2	2	2
Expected return on plan assets	(2)	(3)	(3)
Cost of special termination benefits	0	0	0
Amortization of net actuarial loss	1	2	2
Settlement costs	9	4	5
Net periodic benefit cost	11	6	7
Amounts recognized in other comprehensive income (loss):
Net actuarial (loss) gain	(6)	(3)	(4)
Settlement costs	9	4	5
Amortization of net actuarial gain/loss	1	2	2
Total recognized in other comprehensive income (loss)	4	3	3
Postretirement Benefits
Net periodic benefit costs:
Service cost—benefits earned during the period	4	4	3
Interest cost on projected benefit obligation	4	4	4
Expected return on plan assets	0	0	0
Cost of special termination benefits	6	0	0
Amortization of net actuarial loss	0	0	0
Settlement costs	0	0	0
Net periodic benefit cost	14	8	7
Amounts recognized in other comprehensive income (loss):
Net actuarial (loss) gain	(19)	14	(12)
Settlement costs	(2)	0	0
Amortization of net actuarial gain/loss	0	0	0
Total recognized in other comprehensive income (loss)	$ (21)	$ 14	$ (12)