PENSION PLANS AND OTHER POSTRETIREMENT BENEFITS (Basis of Fair Value Measurements of Pension Plan Assets) (Details) - USD ($) $ in Millions	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
Subtotal	18,511	16,727
Investments measured at NAV	6,499	5,913
Pension Trust Receivables	70	29
Pension Trust Payables	(172)	(125)
Defined Benefit Pension Plans | Quoted Prices in Active Markets for Identical Items (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Subtotal	9,103	8,326
Defined Benefit Pension Plans | Significant Other Observable Inputs (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Subtotal	9,368	8,360
Defined Benefit Pension Plans | Significant Unobservable Inputs (Level 3)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	40	41	56
Subtotal	40	41
Cash and Cash Equivalents | Defined Benefit Pension Plans
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	754	877
Cash and Cash Equivalents | Defined Benefit Pension Plans | Quoted Prices in Active Markets for Identical Items (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	675	818
Cash and Cash Equivalents | Defined Benefit Pension Plans | Significant Other Observable Inputs (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	79	59
Cash and Cash Equivalents | Defined Benefit Pension Plans | Significant Unobservable Inputs (Level 3)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
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 | Quoted Prices in Active Markets for Identical Items (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	7,571	6,748
Equity securities | Defined Benefit Pension Plans | Significant Other Observable Inputs (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	892	948
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
Non-U.S. Equity [Member] | Defined Benefit Pension Plans
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	4,646	4,242
Non-U.S. Equity [Member] | Defined Benefit Pension Plans | Quoted Prices in Active Markets for Identical Items (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	3,819	3,497
Non-U.S. Equity [Member] | Defined Benefit Pension Plans | Significant Other Observable Inputs (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	801	707
Non-U.S. Equity [Member] | Defined Benefit Pension Plans | Significant Unobservable Inputs (Level 3)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	26	38
U.S. Equity [Member] | Defined Benefit Pension Plans
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	3,844	3,493
U.S. Equity [Member] | Defined Benefit Pension Plans | Quoted Prices in Active Markets for Identical Items (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	3,752	3,251
U.S. Equity [Member] | Defined Benefit Pension Plans | Significant Other Observable Inputs (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	91	241
U.S. Equity [Member] | Defined Benefit Pension Plans | Significant Unobservable Inputs (Level 3)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	1	1
Government debt | Defined Benefit Pension Plans
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	4,992	4,751
Government debt | Defined Benefit Pension Plans | Quoted Prices in Active Markets for Identical Items (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	197	285
Government debt | Defined Benefit Pension Plans | Significant Other Observable Inputs (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	4,795	4,466
Government debt | Defined Benefit Pension Plans | Significant Unobservable Inputs (Level 3)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Corporate bonds | Defined Benefit Pension Plans
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	3,697	2,929
Corporate bonds | Defined Benefit Pension Plans | Quoted Prices in Active Markets for Identical Items (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	607	411
Corporate bonds | Defined Benefit Pension Plans | Significant Other Observable Inputs (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	3,089	2,518
Corporate bonds | Defined Benefit Pension Plans | Significant Unobservable Inputs (Level 3)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	1	0
Debt - asset-backed | Defined Benefit Pension Plans
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	70	90
Debt - asset-backed | Defined Benefit Pension Plans | Quoted Prices in Active Markets for Identical Items (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Debt - asset-backed | Defined Benefit Pension Plans | Significant Other Observable Inputs (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	69	89
Debt - asset-backed | Defined Benefit Pension Plans | Significant Unobservable Inputs (Level 3)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	1	1
Total fixed income securities | Defined Benefit Pension Plans
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	8,759	7,770
Total fixed income securities | Defined Benefit Pension Plans | Quoted Prices in Active Markets for Identical Items (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	804	696
Total fixed income securities | Defined Benefit Pension Plans | Significant Other Observable Inputs (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	7,953	7,073
Total 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
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 | Quoted Prices in Active Markets for Identical Items (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	25	17
Alternative Investments | Defined Benefit Pension Plans | Significant Other Observable Inputs (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	61	(53)
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
Hedge Funds | Defined Benefit Pension Plans
Defined Benefit Plan Disclosure [Line Items]
Investments measured at NAV	1,595	1,637
Private Equity Funds | Defined Benefit Pension Plans
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	11	1
Investments measured at NAV	2,794	2,196
Private Equity Funds | Defined Benefit Pension Plans | Quoted Prices in Active Markets for Identical Items (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Private Equity Funds | Defined Benefit Pension Plans | Significant Other Observable Inputs (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Private Equity Funds | Defined Benefit Pension Plans | Significant Unobservable Inputs (Level 3)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	11	1
Real Estate | Defined Benefit Pension Plans
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	25	19
Investments measured at NAV	2,110	2,080
Real Estate | Defined Benefit Pension Plans | Quoted Prices in Active Markets for Identical Items (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	25	19
Real Estate | Defined Benefit Pension Plans | Significant Other Observable Inputs (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Real Estate | Defined Benefit Pension Plans | Significant Unobservable Inputs (Level 3)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Derivatives - asset position | Defined Benefit Pension Plans
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	574	451
Derivatives - asset position | Defined Benefit Pension Plans | Quoted Prices in Active Markets for Identical Items (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	2	17
Derivatives - asset position | Defined Benefit Pension Plans | Significant Other Observable Inputs (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	572	434
Derivatives - asset position | Defined Benefit Pension Plans | Significant Unobservable Inputs (Level 3)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Derivatives - liability position | Defined Benefit Pension Plans
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	(513)	(506)
Derivatives - liability position | Defined Benefit Pension Plans | Quoted Prices in Active Markets for Identical Items (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	(2)	(19)
Derivatives - liability position | Defined Benefit Pension Plans | Significant Other Observable Inputs (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	(511)	(487)
Derivatives - liability position | Defined Benefit Pension Plans | Significant Unobservable Inputs (Level 3)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
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 | Quoted Prices in Active Markets for Identical Items (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	28	47
Other Investments | Defined Benefit Pension Plans | Significant Other Observable Inputs (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	383	333
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