RETIREMENT BENEFITS - Discount Rate and Expected Rate of Return (Details) - USD ($) $ in Millions	1 Months Ended	3 Months Ended		12 Months Ended
	Dec. 31, 2017	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Defined Benefit Plans and Other Postretirement Benefit Plans
Expected return on assets (as a percent)	6.80%			6.70%	6.80%	6.80%
Expected return on plan assets				$ 1	$ 0	$ 0
Top 5 Non-US Countries
Defined Benefit Plans and Other Postretirement Benefit Plans
Discount rate established rounding convention				0.0005
All Other Countries
Defined Benefit Plans and Other Postretirement Benefit Plans
Discount rate established rounding convention				0.0025
U.S.
Defined Benefit Plans and Other Postretirement Benefit Plans
Expected return on assets (as a percent)		6.70%	6.80%
Pension and Postretirement Plan | U.S.
Defined Benefit Plans and Other Postretirement Benefit Plans
Expected return on assets (as a percent)					6.80%	7.00%
Actual rate of return (as a percent)				(3.40%)	10.90%	4.90%
Pension Plans | U.S.
Defined Benefit Plans and Other Postretirement Benefit Plans
Expected return on plan assets				$ 844	$ 865	$ 886
Pension Plans | Non-U.S.
Defined Benefit Plans and Other Postretirement Benefit Plans
Expected return on plan assets				291	$ 299	$ 287
Actual return on plan assets				$ (11)
VEBA Trust
Defined Benefit Plans and Other Postretirement Benefit Plans
Expected return on assets (as a percent)	3.00%			3.00%	3.00%	0.00%
Actual rate of return (as a percent)					0.00%	0.00%
VEBA Trust | U.S.
Defined Benefit Plans and Other Postretirement Benefit Plans
Expected return on assets (as a percent)	3.00%			3.00%	3.00%
Minimum | Pension and Postretirement Plan | U.S.
Defined Benefit Plans and Other Postretirement Benefit Plans
Expected return on assets (as a percent)				6.80%
Minimum | Pension Plans | U.S.
Defined Benefit Plans and Other Postretirement Benefit Plans
Expected return on assets (as a percent)				6.80%
Minimum | Pension Plans | Non-U.S.
Defined Benefit Plans and Other Postretirement Benefit Plans
Expected return on assets (as a percent)	0.00%			1.00%	0.00%
Expected return on assets (as a percent)				1.00%	1.60%	1.30%
Minimum | VEBA Trust
Defined Benefit Plans and Other Postretirement Benefit Plans
Actual rate of return (as a percent)				0.43%
Maximum | Pension and Postretirement Plan | U.S.
Defined Benefit Plans and Other Postretirement Benefit Plans
Expected return on assets (as a percent)				6.70%
Maximum | Pension Plans | U.S.
Defined Benefit Plans and Other Postretirement Benefit Plans
Expected return on assets (as a percent)				6.70%
Maximum | Pension Plans | Non-U.S.
Defined Benefit Plans and Other Postretirement Benefit Plans
Expected return on assets (as a percent)	11.50%			11.50%	11.50%
Expected return on assets (as a percent)				11.50%	11.50%	11.50%
Maximum | VEBA Trust
Defined Benefit Plans and Other Postretirement Benefit Plans
Actual rate of return (as a percent)				1.41%