RETIREMENT BENEFITS - Plan Assets (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2019
U.S. | Pension Plans
Defined Benefit Plan Disclosure
Weighted average allocation (as a percent)	100.00%	100.00%
Company contributions	$ 55	$ 105
U.S. | Postretirement Benefit Plans
Defined Benefit Plan Disclosure
Weighted average allocation (as a percent)	100.00%	100.00%
Company contributions	$ 150	$ 176
U.S. | Equity securities | Pension Plans
Defined Benefit Plan Disclosure
Weighted average allocation (as a percent)	15.00%	20.00%
U.S. | Equity securities | Postretirement Benefit Plans
Defined Benefit Plan Disclosure
Weighted average allocation (as a percent)	15.00%	20.00%
U.S. | Equity securities | Forecast | Minimum
Defined Benefit Plan Disclosure
Target asset allocation (as a percent)			0.00%
U.S. | Equity securities | Forecast | Maximum
Defined Benefit Plan Disclosure
Target asset allocation (as a percent)			26.00%
U.S. | Debt securities | Pension Plans
Defined Benefit Plan Disclosure
Weighted average allocation (as a percent)	57.00%	48.00%
U.S. | Debt securities | Postretirement Benefit Plans
Defined Benefit Plan Disclosure
Weighted average allocation (as a percent)	57.00%	48.00%
U.S. | Debt securities | Forecast | Minimum
Defined Benefit Plan Disclosure
Target asset allocation (as a percent)			35.00%
U.S. | Debt securities | Forecast | Maximum
Defined Benefit Plan Disclosure
Target asset allocation (as a percent)			82.00%
U.S. | Real estate | Pension Plans
Defined Benefit Plan Disclosure
Weighted average allocation (as a percent)	5.00%	5.00%
U.S. | Real estate | Postretirement Benefit Plans
Defined Benefit Plan Disclosure
Weighted average allocation (as a percent)	5.00%	5.00%
U.S. | Real estate | Forecast | Minimum
Defined Benefit Plan Disclosure
Target asset allocation (as a percent)			0.00%
U.S. | Real estate | Forecast | Maximum
Defined Benefit Plan Disclosure
Target asset allocation (as a percent)			7.00%
U.S. | Private equity | Pension Plans
Defined Benefit Plan Disclosure
Weighted average allocation (as a percent)	3.00%	3.00%
U.S. | Private equity | Postretirement Benefit Plans
Defined Benefit Plan Disclosure
Weighted average allocation (as a percent)	3.00%	3.00%
U.S. | Private equity | Forecast | Minimum
Defined Benefit Plan Disclosure
Target asset allocation (as a percent)			0.00%
U.S. | Private equity | Forecast | Maximum
Defined Benefit Plan Disclosure
Target asset allocation (as a percent)			10.00%
U.S. | Other investments | Pension Plans
Defined Benefit Plan Disclosure
Weighted average allocation (as a percent)	20.00%	24.00%
U.S. | Other investments | Postretirement Benefit Plans
Defined Benefit Plan Disclosure
Weighted average allocation (as a percent)	20.00%	24.00%
U.S. | Other investments | Forecast | Minimum
Defined Benefit Plan Disclosure
Target asset allocation (as a percent)			0.00%
U.S. | Other investments | Forecast | Maximum
Defined Benefit Plan Disclosure
Target asset allocation (as a percent)			30.00%
Non-U.S. | Pension Plans
Defined Benefit Plan Disclosure
Company contributions	$ 182	$ 135
Non-U.S. | Postretirement Benefit Plans
Defined Benefit Plan Disclosure
Company contributions	$ 9	$ 9
Non-U.S. | Weighted Average | Pension Plans
Defined Benefit Plan Disclosure
Weighted average allocation (as a percent)	100.00%	100.00%
Non-U.S. | Weighted Average | Postretirement Benefit Plans
Defined Benefit Plan Disclosure
Weighted average allocation (as a percent)	100.00%	100.00%
Non-U.S. | Equity securities | Minimum | Pension Plans
Defined Benefit Plan Disclosure
Target asset allocation (as a percent)	0.00%	0.00%
Non-U.S. | Equity securities | Minimum | Postretirement Benefit Plans
Defined Benefit Plan Disclosure
Target asset allocation (as a percent)	0.00%	0.00%
Non-U.S. | Equity securities | Maximum | Pension Plans
Defined Benefit Plan Disclosure
Target asset allocation (as a percent)	66.00%	67.00%
Non-U.S. | Equity securities | Maximum | Postretirement Benefit Plans
Defined Benefit Plan Disclosure
Target asset allocation (as a percent)	35.00%	38.00%
Non-U.S. | Equity securities | Weighted Average | Pension Plans
Defined Benefit Plan Disclosure
Weighted average allocation (as a percent)	13.00%	15.00%
Non-U.S. | Equity securities | Weighted Average | Postretirement Benefit Plans
Defined Benefit Plan Disclosure
Weighted average allocation (as a percent)	35.00%	38.00%
Non-U.S. | Equity securities | Forecast | Minimum | Pension Plans
Defined Benefit Plan Disclosure
Target asset allocation (as a percent)			0.00%
Non-U.S. | Equity securities | Forecast | Minimum | Postretirement Benefit Plans
Defined Benefit Plan Disclosure
Target asset allocation (as a percent)			0.00%
Non-U.S. | Equity securities | Forecast | Maximum | Pension Plans
Defined Benefit Plan Disclosure
Target asset allocation (as a percent)			63.00%
Non-U.S. | Equity securities | Forecast | Maximum | Postretirement Benefit Plans
Defined Benefit Plan Disclosure
Target asset allocation (as a percent)			30.00%
Non-U.S. | Debt securities | Minimum | Pension Plans
Defined Benefit Plan Disclosure
Target asset allocation (as a percent)	0.00%	0.00%
Non-U.S. | Debt securities | Minimum | Postretirement Benefit Plans
Defined Benefit Plan Disclosure
Target asset allocation (as a percent)	62.00%	58.00%
Non-U.S. | Debt securities | Maximum | Pension Plans
Defined Benefit Plan Disclosure
Target asset allocation (as a percent)	100.00%	99.00%
Non-U.S. | Debt securities | Maximum | Postretirement Benefit Plans
Defined Benefit Plan Disclosure
Target asset allocation (as a percent)	100.00%	100.00%
Non-U.S. | Debt securities | Weighted Average | Pension Plans
Defined Benefit Plan Disclosure
Weighted average allocation (as a percent)	80.00%	79.00%
Non-U.S. | Debt securities | Weighted Average | Postretirement Benefit Plans
Defined Benefit Plan Disclosure
Weighted average allocation (as a percent)	62.00%	58.00%
Non-U.S. | Debt securities | Forecast | Minimum | Pension Plans
Defined Benefit Plan Disclosure
Target asset allocation (as a percent)			0.00%
Non-U.S. | Debt securities | Forecast | Minimum | Postretirement Benefit Plans
Defined Benefit Plan Disclosure
Target asset allocation (as a percent)			64.00%
Non-U.S. | Debt securities | Forecast | Maximum | Pension Plans
Defined Benefit Plan Disclosure
Target asset allocation (as a percent)			100.00%
Non-U.S. | Debt securities | Forecast | Maximum | Postretirement Benefit Plans
Defined Benefit Plan Disclosure
Target asset allocation (as a percent)			100.00%
Non-U.S. | Real estate | Minimum | Pension Plans
Defined Benefit Plan Disclosure
Target asset allocation (as a percent)	0.00%	0.00%
Non-U.S. | Real estate | Maximum | Pension Plans
Defined Benefit Plan Disclosure
Target asset allocation (as a percent)	12.00%	18.00%
Non-U.S. | Real estate | Weighted Average | Pension Plans
Defined Benefit Plan Disclosure
Weighted average allocation (as a percent)	1.00%	1.00%
Non-U.S. | Real estate | Forecast | Minimum | Pension Plans
Defined Benefit Plan Disclosure
Target asset allocation (as a percent)			0.00%
Non-U.S. | Real estate | Forecast | Maximum | Pension Plans
Defined Benefit Plan Disclosure
Target asset allocation (as a percent)			15.00%
Non-U.S. | Other investments | Minimum | Pension Plans
Defined Benefit Plan Disclosure
Target asset allocation (as a percent)	0.00%	0.00%
Non-U.S. | Other investments | Minimum | Postretirement Benefit Plans
Defined Benefit Plan Disclosure
Target asset allocation (as a percent)	0.00%	0.00%
Non-U.S. | Other investments | Maximum | Pension Plans
Defined Benefit Plan Disclosure
Target asset allocation (as a percent)	100.00%	100.00%
Non-U.S. | Other investments | Maximum | Postretirement Benefit Plans
Defined Benefit Plan Disclosure
Target asset allocation (as a percent)	3.00%	4.00%
Non-U.S. | Other investments | Weighted Average | Pension Plans
Defined Benefit Plan Disclosure
Weighted average allocation (as a percent)	6.00%	5.00%
Non-U.S. | Other investments | Weighted Average | Postretirement Benefit Plans
Defined Benefit Plan Disclosure
Weighted average allocation (as a percent)	3.00%	4.00%
Non-U.S. | Other investments | Forecast | Minimum | Pension Plans
Defined Benefit Plan Disclosure
Target asset allocation (as a percent)			0.00%
Non-U.S. | Other investments | Forecast | Minimum | Postretirement Benefit Plans
Defined Benefit Plan Disclosure
Target asset allocation (as a percent)			0.00%
Non-U.S. | Other investments | Forecast | Maximum | Pension Plans
Defined Benefit Plan Disclosure
Target asset allocation (as a percent)			100.00%
Non-U.S. | Other investments | Forecast | Maximum | Postretirement Benefit Plans
Defined Benefit Plan Disclosure
Target asset allocation (as a percent)			6.00%