PENSION PLANS AND OTHER POSTRETIREMENT BENEFITS (Fair Value Measurement of Level 3 Pension Plan Assets) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 24,900	$ 22,500
Defined Benefit Pension Plans
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	24,908	22,544	$ 23,401
Defined Benefit Pension Plans | Significant Unobservable Inputs (Level 3)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	40	41	56
Plan Assets Sold	(2)	4
Plan Assets Still Held	(13)	(7)
Purchases, sales and settlements, net	14	(12)
Equity securities | Defined Benefit Pension Plans
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	8,490	7,735
Equity securities | Defined Benefit Pension Plans | Significant Unobservable Inputs (Level 3)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	27	39	40
Plan Assets Sold	(2)	0
Plan Assets Still Held	1	(3)
Purchases, sales and settlements, net	(11)	2
Fixed Income Securities | Defined Benefit Pension Plans
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	8,759	7,770
Fixed Income Securities | Defined Benefit Pension Plans | Significant Unobservable Inputs (Level 3)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	2	1	16
Plan Assets Sold	0	4
Plan Assets Still Held	0	(4)
Purchases, sales and settlements, net	1	(15)
Alternative Investments | Defined Benefit Pension Plans
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	97	(35)
Alternative Investments | Defined Benefit Pension Plans | Significant Unobservable Inputs (Level 3)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	11	1	0
Plan Assets Sold	0	(1)
Plan Assets Still Held	(14)	0
Purchases, sales and settlements, net	24	2
Other Investments | Defined Benefit Pension Plans
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	411	380
Other Investments | Defined Benefit Pension Plans | Significant Unobservable Inputs (Level 3)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0	$ 0
Plan Assets Sold	0	1
Plan Assets Still Held	0	0
Purchases, sales and settlements, net	$ 0	$ (1)