RETIREMENT BENEFITS - Assumptions Used (Details)	3 Months Ended	12 Months Ended
	Mar. 31, 2021	Dec. 31, 2020	Mar. 31, 2020
U.S. | Postretirement Benefit Plans
Plan Assumptions - During the year
Discount rate	2.20%	2.35%
Plan Assumptions - At period end
Discount rate	2.85%	2.20%	3.20%
Non-U.S. plans | Pension Plans | Weighted Average
Plan Assumptions - During the year
Discount rate	3.60%	3.74%
Plan Assumptions - At period end
Discount rate	3.59%	3.60%	4.38%
Non-U.S. plans | Pension Plans | Minimum
Plan Assumptions - During the year
Discount rate	0.05%	0.05%
Plan Assumptions - At period end
Discount rate	0.25%	0.05%	0.45%
Non-U.S. plans | Pension Plans | Maximum
Plan Assumptions - During the year
Discount rate	8.15%	8.55%
Plan Assumptions - At period end
Discount rate	9.30%	8.15%	9.45%
Non-U.S. plans | Postretirement Benefit Plans
Plan Assumptions - During the year
Discount rate	8.55%	9.00%
Plan Assumptions - At period end
Discount rate	9.70%	8.55%	9.75%
Qualified plans | U.S. | Pension Plans
Plan Assumptions - During the year
Discount rate	2.45%	2.55%
Plan Assumptions - At period end
Discount rate	3.10%	2.45%	3.20%
Nonqualified plans | U.S. | Pension Plans
Plan Assumptions - During the year
Discount rate	2.35%	2.50%
Plan Assumptions - At period end
Discount rate	3.00%	2.35%	3.25%