EMPLOYEE BENEFIT PLANS - Benefit Obligations, Fair Value of Plan Assets and Funded Status (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Pension Benefits
Change in Benefit Obligation
Benefit obligation at beginning of period	$ 15,811	$ 21,073
Service cost	95	0	$ 0
Interest cost	855	611	582
Actuarial loss/(gain)	351	(4,599)
Benefits paid, including lump sums and annuities	(1,201)	(1,274)
Plan amendments	0	0
Participant contributions	0	0
Benefit obligation at end of period	15,911	15,811	21,073
Change in Fair Value of Plan Assets
Fair value of plan assets at beginning of period	15,721	19,502
Actual gain/(loss) on plan assets	1,142	(2,517)
Employer contributions	104	10
Participant contributions	0	0
Benefits paid, including lump sums and annuities	(1,201)	(1,274)
Fair value of plan assets at end of period	15,766	15,721	19,502
Funded Status of Plan
Funded status at end of period	(145)	(90)
Other Postretirement and Postemployment Benefits
Change in Benefit Obligation
Benefit obligation at beginning of period	3,664	4,605
Service cost	71	70	86
Interest cost	200	128	117
Actuarial loss/(gain)	24	(710)
Benefits paid, including lump sums and annuities	(485)	(447)
Plan amendments	11	0
Participant contributions	18	18
Benefit obligation at end of period	3,503	3,664	4,605
Change in Fair Value of Plan Assets
Fair value of plan assets at beginning of period	71	357
Actual gain/(loss) on plan assets	3	(73)
Employer contributions	426	216
Participant contributions	18	18
Benefits paid, including lump sums and annuities	(485)	(447)
Fair value of plan assets at end of period	33	71	$ 357
Funded Status of Plan
Funded status at end of period	$ (3,470)	$ (3,593)