POSTRETIREMENT BENEFIT PLANS - Components of Net Periodic Expense (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Defined Benefit Plan Disclosure [Line Items]
Non-operating	$ (94)	$ (1)	$ (332)	$ (4)
Defined benefit plans
Defined Benefit Plan Disclosure [Line Items]
Service cost – Operating	14	4	43	14
Interest cost	290	4	872	13
Expected return on plan assets	(357)	(7)	(1,070)	(21)
Amortization of net loss (gain)	(28)	2	(89)	5
Amortization of prior service cost (credit)	1	(1)	(1)	(3)
Curtailment loss (gain)	17	0	17	0
Non-operating	(77)	(2)	(271)	(6)
Net periodic expense (income)	(63)	2	(228)	8
Other postretirement plans
Defined Benefit Plan Disclosure [Line Items]
Service cost – Operating	2	0	6	0
Interest cost	15	0	45	0
Expected return on plan assets	0	0	0	0
Amortization of net loss (gain)	(16)	0	(48)	0
Amortization of prior service cost (credit)	(22)	0	(66)	0
Curtailment loss (gain)	0	0	0	0
Non-operating	(23)	0	(69)	0
Net periodic expense (income)	$ (21)	$ 0	$ (63)	$ 0