RETIREMENT BENEFITS - Plan Assets (Details)	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
U.S. | Pension Plans
Defined Benefit Plan Disclosure
Weighted average allocation (as a percent)		100.00%	100.00%
U.S. | Postretirement Benefit Plans
Defined Benefit Plan Disclosure
Weighted average allocation (as a percent)		100.00%	100.00%
U.S. | Equity securities | Pension Plans
Defined Benefit Plan Disclosure
Weighted average allocation (as a percent)		17.00%	15.00%
U.S. | Equity securities | Postretirement Benefit Plans
Defined Benefit Plan Disclosure
Weighted average allocation (as a percent)		17.00%	15.00%
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)		58.00%	57.00%
U.S. | Debt securities | Postretirement Benefit Plans
Defined Benefit Plan Disclosure
Weighted average allocation (as a percent)		58.00%	57.00%
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)		4.00%	5.00%
U.S. | Real estate | Postretirement Benefit Plans
Defined Benefit Plan Disclosure
Weighted average allocation (as a percent)		4.00%	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)		18.00%	20.00%
U.S. | Other investments | Postretirement Benefit Plans
Defined Benefit Plan Disclosure
Weighted average allocation (as a percent)		18.00%	20.00%
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. | 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)		100.00%	66.00%
Non-U.S. | Equity securities | Maximum | Postretirement Benefit Plans
Defined Benefit Plan Disclosure
Target asset allocation (as a percent)		38.00%	41.00%
Non-U.S. | Equity securities | Weighted Average | Pension Plans
Defined Benefit Plan Disclosure
Weighted average allocation (as a percent)		13.00%	13.00%
Non-U.S. | Equity securities | Weighted Average | Postretirement Benefit Plans
Defined Benefit Plan Disclosure
Weighted average allocation (as a percent)		27.00%	35.00%
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)	100.00%
Non-U.S. | Equity securities | Forecast | Maximum | Postretirement Benefit Plans
Defined Benefit Plan Disclosure
Target asset allocation (as a percent)	38.00%
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)		57.00%	56.00%
Non-U.S. | Debt securities | Maximum | Pension Plans
Defined Benefit Plan Disclosure
Target asset allocation (as a percent)		100.00%	100.00%
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%	80.00%
Non-U.S. | Debt securities | Weighted Average | Postretirement Benefit Plans
Defined Benefit Plan Disclosure
Weighted average allocation (as a percent)		71.00%	62.00%
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)	56.00%
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)		15.00%	12.00%
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)		4.00%	3.00%
Non-U.S. | Other investments | Weighted Average | Pension Plans
Defined Benefit Plan Disclosure
Weighted average allocation (as a percent)		6.00%	6.00%
Non-U.S. | Other investments | Weighted Average | Postretirement Benefit Plans
Defined Benefit Plan Disclosure
Weighted average allocation (as a percent)		2.00%	3.00%
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%