RETIREMENT BENEFITS - Net (Benefit) Expense (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
U.S. | Pension Plans
Amortization of unrecognized
Total net (benefit) expense	$ (39)	$ (32)	$ (108)	$ (100)
U.S. | Postretirement Benefit Plans
Amortization of unrecognized
Total net (benefit) expense	7	4	15	11
U.S. | Qualified plans | Pension Plans
Service-related expense
Benefits earned during the period	0	1	1	2
Interest cost on benefit obligation	124	126	384	399
Expected return on plan assets	(217)	(224)	(650)	(660)
Amortization of unrecognized
Prior service benefit	0	0	0	0
Net actuarial loss	43	43	122	118
Curtailment loss (gain)	1	10	4	10
Settlement loss	0	0	0	0
Total net (benefit) expense	(49)	(44)	(139)	(131)
U.S. | Qualified plans | Postretirement Benefit Plans
Service-related expense
Benefits earned during the period	0	0	0	0
Interest cost on benefit obligation	9	6	20	19
Expected return on plan assets	(2)	(2)	(5)	(7)
Amortization of unrecognized
Prior service benefit	0	0	0	0
Net actuarial loss	0	0	0	(1)
Curtailment loss (gain)	0	0	0	0
Settlement loss	0	0	0	0
Total net (benefit) expense	7	4	15	11
U.S. | Nonqualified plans | Pension Plans
Amortization of unrecognized
Total net (benefit) expense	10	12	31	31
U.S. | Nonqualified plans | Postretirement Benefit Plans
Amortization of unrecognized
Total net (benefit) expense	0	0	0	0
Non-U.S. plans | Pension Plans
Amortization of unrecognized
Total net (benefit) expense	55	55	161	171
Non-U.S. plans | Postretirement Benefit Plans
Amortization of unrecognized
Total net (benefit) expense	12	10	34	31
Non-U.S. plans | Qualified plans | Pension Plans
Service-related expense
Benefits earned during the period	38	39	112	116
Interest cost on benefit obligation	76	70	221	216
Expected return on plan assets	(77)	(71)	(223)	(217)
Amortization of unrecognized
Prior service benefit	(1)	0	(3)	(1)
Net actuarial loss	15	19	46	58
Curtailment loss (gain)	0	0	0	(3)
Settlement loss	4	(2)	8	2
Total net (benefit) expense	55	55	161	171
Non-U.S. plans | Qualified plans | Postretirement Benefit Plans
Service-related expense
Benefits earned during the period	3	1	7	7
Interest cost on benefit obligation	27	24	76	72
Expected return on plan assets	(24)	(22)	(67)	(65)
Amortization of unrecognized
Prior service benefit	(2)	(1)	(7)	(7)
Net actuarial loss	8	8	25	24
Curtailment loss (gain)	0	0	0	0
Settlement loss	0	0	0	0
Total net (benefit) expense	12	10	34	31
Non-U.S. plans | Nonqualified plans | Pension Plans
Amortization of unrecognized
Total net (benefit) expense	0	0	0	0
Non-U.S. plans | Nonqualified plans | Postretirement Benefit Plans
Amortization of unrecognized
Total net (benefit) expense	$ 0	$ 0	$ 0	$ 0