PENSIONS AND OTHER POSTRETIREMENT BENEFITS - Components Of Net Periodic Benefit Cost (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Defined Benefit Plan, Expected Amounts [Abstract]
Estimated net periodic benefit cost	$ (82)
Pension Plan [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	23	$ 17	$ 19
Interest cost	64	35	30
Expected return on plan assets	(140)	(55)	(60)
Amortization:
Net actuarial loss	27	24	21
Amortization of prior service cost (credit)	1	1	2
Settlements	(6)	0	1
Net periodic benefit cost (credit)	(31)	22	13
Defined Benefit Plan, Expected Amounts [Abstract]
Estimated net periodic benefit cost	(168)
Other Postretirement Benefits Plan [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	8	2	2
Interest cost	19	10	8
Expected return on plan assets	(20)	(17)	(18)
Amortization:
Net actuarial loss	3	5	5
Amortization of prior service cost (credit)	(2)	(2)	(3)
Settlements	0	0	0
Net periodic benefit cost (credit)	8	$ (2)	$ (6)
Defined Benefit Plan, Expected Amounts [Abstract]
Estimated net periodic benefit cost	$ 86