PENSION PLANS AND OTHER POSTRETIREMENT BENEFITS (Net Periodic Benefit Cost and Other Changes in Plan Assets and Benefit Obligations Recognized in Other Comprehensive Income for All Significant 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, Net Periodic Benefit Cost (Credit), Gain (Loss) Due to Settlement and Curtailment	$ 19
Net periodic benefit cost		$ (332)	$ (103)	$ (205)
Defined Benefit Pension Plans
Defined Benefit Plan Disclosure [Line Items]
Service cost		387	399	396
Interest cost		594	767	921
Expected return on plan assets		(1,724)	(1,658)	(1,679)
Amortization of prior service credit		(22)	(19)	(20)
Amortization of unrecognized (gain) loss		822	773	574
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Gain (Loss) Due to Settlement and Curtailment		18	(9)	27
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Including Discontinued Operations		39	271	165
Net periodic benefit cost		39	271	144
Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss) Arising During Period, before Tax		1,980	(1,753)	(1,606)
Prior service cost (credit)		2	8	0
Amortization of prior service credit		22	19	20
Amortization of unrecognized gain (loss)		(822)	(773)	(574)
Curtailment/Settlement gain (loss)		18	(9)	27
Total recognized in other comprehensive (income) loss		(2,760)	998	967
Total recognized in net periodic benefit cost and other comprehensive (income) loss		(2,721)	1,269	1,132
Other Postretirement Benefit Plans
Defined Benefit Plan Disclosure [Line Items]
Service cost		7	7	8
Interest cost		23	40	49
Expected return on plan assets		0	0	0
Amortization of prior service credit		0	0	0
Amortization of unrecognized (gain) loss		(6)	(10)	(20)
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Gain (Loss) Due to Settlement and Curtailment		0	0	3
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Including Discontinued Operations		24	37	34
Net periodic benefit cost		24	37	34
Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss) Arising During Period, before Tax		98	(8)	(145)
Prior service cost (credit)		0	0	0
Amortization of prior service credit		0	0	0
Amortization of unrecognized gain (loss)		6	10	20
Curtailment/Settlement gain (loss)		0	0	3
Total recognized in other comprehensive (income) loss		(92)	18	168
Total recognized in net periodic benefit cost and other comprehensive (income) loss		(68)	55	202
Discontinued Operations [Member] | Defined Benefit Pension Plans
Defined Benefit Plan Disclosure [Line Items]
Net periodic benefit cost		0	0	21
Transfer of Business Under Common Control - Before Tax		0	0	(112)
Discontinued Operations [Member] | Other Postretirement Benefit Plans
Defined Benefit Plan Disclosure [Line Items]
Net periodic benefit cost		0	0	0
Transfer of Business Under Common Control - Before Tax		$ 0	$ 0	$ 0