RETIREMENT BENEFITS - Net (Benefit) Expense (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Defined Benefit Plan Disclosure
Percentage of the significant plans over global pension and postretirement liabilities, which utilize quarterly measurement policy	90.00%
Defined Benefit Plan, Net Periodic Benefit Cost
Interest cost on benefit obligation	$ 2	$ 2	$ 2
Expected return on plan assets	(1)	(1)	0
Amortization of unrecognized
Prior service cost (benefit)	0	(23)	(31)
Total net expense	9	(18)	3
U.S. | Pension Plans
Defined Benefit Plan, Net Periodic Benefit Cost
Benefits earned during the year	1	1	3
Interest cost on benefit obligation	469	514	533
Expected return on plan assets	(821)	(844)	(865)
Amortization of unrecognized
Prior service cost (benefit)	2	2	2
Net actuarial loss	200	165	173
Curtailment loss (gain)	1	1	6
Settlement loss	0	0	0
Total net expense	(148)	(161)	(148)
U.S. | Postretirement Benefit Plans
Defined Benefit Plan, Net Periodic Benefit Cost
Benefits earned during the year	0	0	0
Interest cost on benefit obligation	24	26	26
Expected return on plan assets	(18)	(14)	(6)
Amortization of unrecognized
Prior service cost (benefit)	0	0	0
Net actuarial loss	0	(1)	0
Curtailment loss (gain)	0	0	0
Settlement loss	0	0	0
Total net expense	6	11	20
Non-U.S. | Pension Plans
Defined Benefit Plan, Net Periodic Benefit Cost
Benefits earned during the year	146	146	153
Interest cost on benefit obligation	287	292	295
Expected return on plan assets	(281)	(291)	(299)
Amortization of unrecognized
Prior service cost (benefit)	(4)	(4)	(3)
Net actuarial loss	61	53	61
Curtailment loss (gain)	(6)	(1)	0
Settlement loss	6	7	12
Total net expense	209	202	219
Non-U.S. | Postretirement Benefit Plans
Defined Benefit Plan, Net Periodic Benefit Cost
Benefits earned during the year	8	9	9
Interest cost on benefit obligation	104	102	101
Expected return on plan assets	(84)	(88)	(89)
Amortization of unrecognized
Prior service cost (benefit)	(10)	(10)	(10)
Net actuarial loss	23	29	35
Curtailment loss (gain)	0	0	0
Settlement loss	0	0	0
Total net expense	$ 41	$ 42	$ 46