PENSION PLANS AND OTHER POSTRETIREMENT BENEFITS (Change in Projected Benefit Obligation, Plan Assets and Funded Status) (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, Plan Assets, Amount		$ 3,600	$ 3,100
Defined Benefit Plan, Plan Assets, Contributions by Employer		549
Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Benefit Obligation		3,940	4,229	$ 4,097
Defined Benefit Plan, Service Cost		26	35	34
Defined Benefit Plan, Interest Cost		80	112	145
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss)	$ (87)	(112)	393
Defined Benefit Plan, Benefit Obligation, Benefits Paid		(263)	(281)
Defined Benefit Plan, Benefit Obligation, Increase (Decrease) for Other Change		(20)	(127)
Defined Benefit Plan, Plan Assets, Amount		3,611	3,095	3,148
Defined Benefit Plan, Plan Assets, Increase (Decrease) for Actual Return (Loss)		236	344
Defined Benefit Plan, Plan Assets, Contributions by Employer		549	2
Defined Benefit Plan, Plan Assets, Increase (Decrease) for Assets Transferred to (from) Plan		(8)	(10)
Defined Benefit Plan, Plan Assets, Benefits Paid		(263)	(281)
Defined Benefit Plan, Plan Assets, Period Increase (Decrease)		(2)	108
Defined Benefit Plan, Funded (Unfunded) Status of Plan		(329)	(1,134)
Liability, Defined Benefit Plan, Current		(2)	(2)
Liability, Defined Benefit Plan, Noncurrent		(327)	(1,132)
Defined Benefit Plan, Amounts for Asset (Liability) Recognized in Statement of Financial Position		(329)	(1,134)
Defined Benefit Plan, Accumulated Other Comprehensive Income (Loss), Gain (Loss), before Tax		2,007	2,267
Defined Benefit Plan, Accumulated Other Comprehensive (Income) Loss, Prior Service Cost (Credit), before Tax		(1)	(9)
Defined Benefit Plan, Accumulated Other Comprehensive (Income) Loss, before Tax		2,006	2,258
Other Postretirement Benefits Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Benefit Obligation		174	220	220
Defined Benefit Plan, Service Cost		1	1	1
Defined Benefit Plan, Interest Cost		3	5	7
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss)		(37)	2
Defined Benefit Plan, Benefit Obligation, Benefits Paid		(13)	(8)
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, Plan Assets, Period Increase (Decrease)		0	0
Defined Benefit Plan, Funded (Unfunded) Status of Plan		(174)	(220)
Liability, Defined Benefit Plan, Current		(13)	(15)
Liability, Defined Benefit Plan, Noncurrent		(161)	(205)
Defined Benefit Plan, Amounts for Asset (Liability) Recognized in Statement of Financial Position		(174)	(220)
Defined Benefit Plan, Accumulated Other Comprehensive Income (Loss), Gain (Loss), before Tax		(84)	(52)
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		$ (84)	$ (52)