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, 2023	Dec. 31, 2022	Dec. 31, 2021
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Gain (Loss) Due to Settlement and Curtailment	$ 19	$ (642)
Net periodic benefit cost		264	$ (358)	$ (332)
Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost		272	392	387
Interest cost		1,110	680	594
Expected return on plan assets		(1,539)	(1,686)	(1,724)
Amortization of prior service credit		(26)	(21)	(22)
Amortization of unrecognized (gain) loss		89	658	822
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Gain (Loss) Due to Settlement and Curtailment		(642)	0	18
Net periodic benefit cost		548	23	39
Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss) Arising During Period, before Tax		(1,395)	2,231	1,980
Prior service cost (credit)		6	(25)	2
Amortization of prior service credit		26	21	22
Amortization of unrecognized gain (loss)		(89)	(658)	(822)
Curtailment/Settlement gain (loss)		(642)	0	18
Total recognized in other comprehensive (income) loss		696	(2,893)	(2,760)
Total recognized in net periodic benefit cost and other comprehensive (income) loss		1,244	(2,870)	(2,721)
Other Postretirement Benefit Plans
Defined Benefit Plan Disclosure [Line Items]
Service cost		4	6	7
Interest cost		45	26	23
Expected return on plan assets		0	0	0
Amortization of prior service credit		0	0	0
Amortization of unrecognized (gain) loss		(57)	(15)	(6)
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Gain (Loss) Due to Settlement and Curtailment		0	0	0
Net periodic benefit cost		(8)	17	24
Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss) Arising During Period, before Tax		(64)	317	98
Prior service cost (credit)		0	0	0
Amortization of prior service credit		0	0	0
Amortization of unrecognized gain (loss)		57	15	6
Curtailment/Settlement gain (loss)		0	0	0
Total recognized in other comprehensive (income) loss		121	(302)	(92)
Total recognized in net periodic benefit cost and other comprehensive (income) loss		$ 113	$ (285)	$ (68)