PENSION PLANS AND OTHER POSTRETIREMENT BENEFITS (Change in Projected Benefit Obligation, Plan Assets and Funded Status) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	$ 3,100	$ 3,100
Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Benefit Obligation	4,229	4,097	$ 3,786
Defined Benefit Plan, Service Cost	35	34	39
Defined Benefit Plan, Interest Cost	112	145	128
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss)	393	453
Defined Benefit Plan, Benefit Obligation, Benefits Paid	(281)	(280)
Defined Benefit Plan, Benefit Obligation, Increase (Decrease) for Other Change	(127)	(41)
Defined Benefit Plan, Plan Assets, Amount	3,095	3,148	$ 3,005
Defined Benefit Plan, Plan Assets, Increase (Decrease) for Actual Return (Loss)	344	464
Defined Benefit Plan, Plan Assets, Contributions by Employer	2	2
Defined Benefit Plan, Plan Assets, Increase (Decrease) for Assets Transferred to (from) Plan	(10)	(43)
Defined Benefit Plan, Plan Assets, Benefits Paid	(281)	(280)
Defined Benefit Plan, Funded (Unfunded) Status of Plan	(1,134)	(949)
Liability, Defined Benefit Plan, Current	(2)	(2)
Liability, Defined Benefit Plan, Noncurrent	(1,132)	(947)
Defined Benefit Plan, Amounts for Asset (Liability) Recognized in Statement of Financial Position	(1,134)	(949)
Defined Benefit Plan, Accumulated Other Comprehensive Income (Loss), Gain (Loss), before Tax	2,267	2,137
Defined Benefit Plan, Accumulated Other Comprehensive (Income) Loss, Prior Service Cost (Credit), before Tax	(9)	(10)
Defined Benefit Plan, Accumulated Other Comprehensive (Income) Loss, before Tax	$ 2,258	$ 2,127
Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Discount Rate	2.53%	3.29%	4.32%
Defined Benefit Plan, Plan Assets, Payment for Settlement	$ (108)	$ 0
Other Postretirement Benefits Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Benefit Obligation	220	220	$ 215
Defined Benefit Plan, Service Cost	1	1	1
Defined Benefit Plan, Interest Cost	5	7	6
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss)	2	12
Defined Benefit Plan, Benefit Obligation, Benefits Paid	(8)	(15)
Defined Benefit Plan, Benefit Obligation, Increase (Decrease) for Other Change	0	0
Defined Benefit Plan, Plan Assets, Amount	0	0	$ 0
Defined Benefit Plan, Plan Assets, Increase (Decrease) for Actual Return (Loss)	0	0
Defined Benefit Plan, Plan Assets, Contributions by Employer	0	0
Defined Benefit Plan, Plan Assets, Increase (Decrease) for Assets Transferred to (from) Plan	0	0
Defined Benefit Plan, Plan Assets, Benefits Paid	0	0
Defined Benefit Plan, Funded (Unfunded) Status of Plan	(220)	(220)
Liability, Defined Benefit Plan, Current	(15)	(17)
Liability, Defined Benefit Plan, Noncurrent	(205)	(203)
Defined Benefit Plan, Amounts for Asset (Liability) Recognized in Statement of Financial Position	(220)	(220)
Defined Benefit Plan, Accumulated Other Comprehensive Income (Loss), Gain (Loss), before Tax	(52)	(60)
Defined Benefit Plan, Accumulated Other Comprehensive (Income) Loss, Prior Service Cost (Credit), before Tax	0	0
Defined Benefit Plan, Accumulated Other Comprehensive (Income) Loss, before Tax	$ (52)	$ (60)
Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Discount Rate	2.34%	3.17%
Defined Benefit Plan, Plan Assets, Payment for Settlement	$ 0	$ 0