RETIREMENT BENEFITS - Level 3 Roll Forward (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
U.S. | Non-U.S. equities
Defined Benefit Plan, Change in Fair Value of Plan Assets, Level 3 Reconciliation [Roll Forward]
Plan assets at fair value at beginning of period	$ 481
Plan assets at fair value at end of period	553	$ 481
U.S. | Non-U.S. equities | Level 3
Defined Benefit Plan, Change in Fair Value of Plan Assets, Level 3 Reconciliation [Roll Forward]
Plan assets at fair value at beginning of period	0
Plan assets at fair value at end of period	0	0
U.S. | Debt securities
Defined Benefit Plan, Change in Fair Value of Plan Assets, Level 3 Reconciliation [Roll Forward]
Plan assets at fair value at beginning of period	4,789
Plan assets at fair value at end of period	5,580	4,789
U.S. | Debt securities | Level 3
Defined Benefit Plan, Change in Fair Value of Plan Assets, Level 3 Reconciliation [Roll Forward]
Plan assets at fair value at beginning of period	0
Plan assets at fair value at end of period	0	0
U.S. | Annuity contracts
Defined Benefit Plan, Change in Fair Value of Plan Assets, Level 3 Reconciliation [Roll Forward]
Plan assets at fair value at beginning of period	1
Plan assets at fair value at end of period	1	1
U.S. | Annuity contracts | Level 3
Defined Benefit Plan, Change in Fair Value of Plan Assets, Level 3 Reconciliation [Roll Forward]
Plan assets at fair value at beginning of period	1	1
Realized gains (losses)	0	0
Unrealized gains (losses)	0	0
Purchases, sales, and issuances	0	0
Transfers in and/or out of Level 3	0	0
Plan assets at fair value at end of period	1	1
U.S. | Other investments
Defined Benefit Plan, Change in Fair Value of Plan Assets, Level 3 Reconciliation [Roll Forward]
Plan assets at fair value at beginning of period	127
Plan assets at fair value at end of period	75	127
U.S. | Other investments | Level 3
Defined Benefit Plan, Change in Fair Value of Plan Assets, Level 3 Reconciliation [Roll Forward]
Plan assets at fair value at beginning of period	127	148
Realized gains (losses)	(7)	(2)
Unrealized gains (losses)	12	(18)
Purchases, sales, and issuances	(57)	(1)
Transfers in and/or out of Level 3	0	0
Plan assets at fair value at end of period	75	127
U.S. | Total investments
Defined Benefit Plan, Change in Fair Value of Plan Assets, Level 3 Reconciliation [Roll Forward]
Plan assets at fair value at beginning of period	7,850
Plan assets at fair value at end of period	8,893	7,850
U.S. | Total investments | Level 3
Defined Benefit Plan, Change in Fair Value of Plan Assets, Level 3 Reconciliation [Roll Forward]
Plan assets at fair value at beginning of period	128	149
Realized gains (losses)	(7)	(2)
Unrealized gains (losses)	12	(18)
Purchases, sales, and issuances	(57)	(1)
Transfers in and/or out of Level 3	0	0
Plan assets at fair value at end of period	76	128
Non-U.S. | Non-U.S. equities
Defined Benefit Plan, Change in Fair Value of Plan Assets, Level 3 Reconciliation [Roll Forward]
Plan assets at fair value at beginning of period	200
Plan assets at fair value at end of period	389	200
Non-U.S. | Non-U.S. equities | Level 3
Defined Benefit Plan, Change in Fair Value of Plan Assets, Level 3 Reconciliation [Roll Forward]
Plan assets at fair value at beginning of period	0	1
Unrealized gains (losses)		0
Purchases, sales, and issuances		0
Transfers in and/or out of Level 3		(1)
Plan assets at fair value at end of period	0	0
Non-U.S. | Debt securities
Defined Benefit Plan, Change in Fair Value of Plan Assets, Level 3 Reconciliation [Roll Forward]
Plan assets at fair value at beginning of period	6,654
Plan assets at fair value at end of period	5,932	6,654
Non-U.S. | Debt securities | Level 3
Defined Benefit Plan, Change in Fair Value of Plan Assets, Level 3 Reconciliation [Roll Forward]
Plan assets at fair value at beginning of period	9	7
Unrealized gains (losses)	1	(1)
Purchases, sales, and issuances	0	3
Transfers in and/or out of Level 3	0	0
Plan assets at fair value at end of period	10	9
Non-U.S. | Real estate
Defined Benefit Plan, Change in Fair Value of Plan Assets, Level 3 Reconciliation [Roll Forward]
Plan assets at fair value at beginning of period	4
Plan assets at fair value at end of period	4	4
Non-U.S. | Real estate | Level 3
Defined Benefit Plan, Change in Fair Value of Plan Assets, Level 3 Reconciliation [Roll Forward]
Plan assets at fair value at beginning of period	1	1
Unrealized gains (losses)	0	0
Purchases, sales, and issuances	0	0
Transfers in and/or out of Level 3	0	0
Plan assets at fair value at end of period	1	1
Non-U.S. | Annuity contracts
Defined Benefit Plan, Change in Fair Value of Plan Assets, Level 3 Reconciliation [Roll Forward]
Plan assets at fair value at beginning of period	11
Plan assets at fair value at end of period	5	11
Non-U.S. | Annuity contracts | Level 3
Defined Benefit Plan, Change in Fair Value of Plan Assets, Level 3 Reconciliation [Roll Forward]
Plan assets at fair value at beginning of period	10	9
Unrealized gains (losses)	0	(1)
Purchases, sales, and issuances	(5)	1
Transfers in and/or out of Level 3	0	1
Plan assets at fair value at end of period	5	10
Non-U.S. | Other investments
Defined Benefit Plan, Change in Fair Value of Plan Assets, Level 3 Reconciliation [Roll Forward]
Plan assets at fair value at beginning of period	211
Plan assets at fair value at end of period	275	211
Non-U.S. | Other investments | Level 3
Defined Benefit Plan, Change in Fair Value of Plan Assets, Level 3 Reconciliation [Roll Forward]
Plan assets at fair value at beginning of period	210	214
Unrealized gains (losses)	7	(3)
Purchases, sales, and issuances	57	(1)
Transfers in and/or out of Level 3	0	0
Plan assets at fair value at end of period	274	210
Non-U.S. | Total investments
Defined Benefit Plan, Change in Fair Value of Plan Assets, Level 3 Reconciliation [Roll Forward]
Plan assets at fair value at beginning of period	10,220
Plan assets at fair value at end of period	11,520	10,220
Non-U.S. | Total investments | Level 3
Defined Benefit Plan, Change in Fair Value of Plan Assets, Level 3 Reconciliation [Roll Forward]
Plan assets at fair value at beginning of period	230	232
Unrealized gains (losses)	8	(5)
Purchases, sales, and issuances	52	3
Transfers in and/or out of Level 3	0	0
Plan assets at fair value at end of period	$ 290	$ 230