PENSION PLANS AND OTHER POSTRETIREMENT BENEFITS (Defined Benefit Pension Plans) (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2021	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss)	$ 1,268
Increase (Decrease) in Obligation, Pension Benefits	345
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Gain (Loss) Due to Settlement and Curtailment	19
Qualified Plan
Defined Benefit Plan Disclosure [Line Items]
Employer contributions	$ 1,000
Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss)		$ 820	$ (3,021)
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Gain (Loss) Due to Settlement and Curtailment		18	(9)	$ 27
Employer contributions		1,219	$ 299
Expected pension contributions		$ 180
Defined Benefit Plan, Assumptions Used in Calculations [Abstract]
Discount rate - benefit obligations		2.57%	2.20%	2.81%
Discount rate - net periodic costs		2.40%	2.81%	3.50%
Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Weighted-Average Interest Crediting Rate		3.57%	3.55%
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Weighted-Average Interest Crediting Rate		3.55%	3.51%	3.72%
Rate of compensation increase - benefit obligations		3.94%	3.91%
Rate of compensation increase - net periodic costs		3.91%	3.92%	3.92%
Expected return on plan assets - net periodic costs		6.86%	7.00%	7.11%
UNITED STATES
Defined Benefit Plan, Assumptions Used in Calculations [Abstract]
Discount rate - benefit obligations		3.04%	2.71%
Discount rate - net periodic costs		3.03%	3.41%	4.15%
Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Weighted-Average Interest Crediting Rate		4.50%	4.50%
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Weighted-Average Interest Crediting Rate		4.50%	4.50%	4.50%
Rate of compensation increase - benefit obligations		4.25%	4.25%
Rate of compensation increase - net periodic costs		4.25%	4.25%	4.25%
Expected return on plan assets - net periodic costs		7.96%	7.95%	7.92%