RETIREMENT AND POSTRETIREMENT BENEFIT PLANS - COMPONENTS OF NET PERIODIC BENEFIT COST (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Pension Benefits
Net periodic benefit costs:
Service cost — benefits earned during the period	$ 37	$ 47	$ 5
Interest cost on projected benefit obligation	52	40	15
Expected return on plan assets	(73)	(52)	(25)
Recognized actuarial loss	5	9	7
Recognized prior service credit	0	0	0
(Gain) loss due to curtailment	(124)	(91)	0
Gain due to settlement	(19)	0	0
Special termination benefits	22	49	0
Other costs and adjustments	1	(2)	1
Net periodic benefit cost	(99)	0	3
Postretirement Benefits
Net periodic benefit costs:
Service cost — benefits earned during the period	39	24	23
Interest cost on projected benefit obligation	37	36	34
Expected return on plan assets	0	0	0
Recognized actuarial loss	11	8	14
Recognized prior service credit	(8)	(8)	0
(Gain) loss due to curtailment	2	6	0
Gain due to settlement	0	0	0
Special termination benefits	0	0	0
Other costs and adjustments	0	0	(2)
Net periodic benefit cost	$ 81	$ 66	$ 69