RETIREMENT BENEFITS - Level 3 Roll Forward (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
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	25
Realized gains (losses)	0	0
Unrealized gains (losses)	0	(3)
Purchases, sales, and issuances	0	(21)
Transfers in and/or out of Level 3	0	0
Plan assets at fair value at end of period	1	1
U.S. | Non-U.S. equity
Defined Benefit Plan, Change in Fair Value of Plan Assets, Level 3 Reconciliation [Roll Forward]
Plan assets at fair value at beginning of period	773
Plan assets at fair value at end of period	926	773
U.S. | Non-U.S. equity | 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	4,142
Plan assets at fair value at end of period	4,461	4,142
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. | 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	4
Plan assets at fair value at end of period	22	4
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	4	149
Realized gains (losses)		8
Unrealized gains (losses)		(10)
Purchases, sales, and issuances	18	(143)
Transfers in and/or out of Level 3	0	0
Plan assets at fair value at end of period	22	4
U.S. | 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	639
Plan assets at fair value at end of period	726	639
U.S. | 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	0
Realized gains (losses)		(2)
Unrealized gains (losses)		2
Purchases, sales, and issuances		0
Transfers in and/or out of Level 3		0
Plan assets at fair value at end of period	0	0
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	7,192
Plan assets at fair value at end of period	7,925	7,192
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	5	174
Realized gains (losses)	0	6
Unrealized gains (losses)	0	(11)
Purchases, sales, and issuances	18	(164)
Transfers in and/or out of Level 3	0	0
Plan assets at fair value at end of period	23	5
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	9
Plan assets at fair value at end of period	10	9
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	8	8
Unrealized gains (losses)	1	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	9	8
Non-U.S. | Non-U.S. equity
Defined Benefit Plan, Change in Fair Value of Plan Assets, Level 3 Reconciliation [Roll Forward]
Plan assets at fair value at beginning of period	262
Plan assets at fair value at end of period	226	262
Non-U.S. | Non-U.S. equity | 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	47
Unrealized gains (losses)	0	(3)
Purchases, sales, and issuances	0	(2)
Transfers in and/or out of Level 3	0	(41)
Plan assets at fair value at end of period	1	1
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	4,619
Plan assets at fair value at end of period	5,561	4,619
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	7	5
Unrealized gains (losses)	0	0
Purchases, sales, and issuances	0	2
Transfers in and/or out of Level 3	0	0
Plan assets at fair value at end of period	7	7
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. | 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	188
Plan assets at fair value at end of period	215	188
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	187	196
Unrealized gains (losses)	31	0
Purchases, sales, and issuances	(4)	(9)
Transfers in and/or out of Level 3	0	0
Plan assets at fair value at end of period	214	187
Non-U.S. | 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	15
Plan assets at fair value at end of period	16	15
Non-U.S. | 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
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	7,913
Plan assets at fair value at end of period	12,331	7,913
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	204	257
Unrealized gains (losses)	32	(3)
Purchases, sales, and issuances	(4)	(9)
Transfers in and/or out of Level 3	0	(41)
Plan assets at fair value at end of period	$ 232	$ 204