RETIREMENT BENEFIT PLANS - Assumptions used (Details)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Other postretirement employee benefits
Defined Benefit Plan, Weighted Average Assumptions Used in Calculating Net Periodic Benefit Cost [Abstract]
Discount rate	2.95%	4.05%
Effective interest rate on benefit obligation	2.50%	3.68%
United States | Pension benefits
Defined Benefit Plan, Weighted Average Assumptions Used in Calculating Benefit Obligation [Abstract]
Discount rate	2.31%	3.17%
Defined Benefit Plan, Weighted Average Assumptions Used in Calculating Net Periodic Benefit Cost [Abstract]
Discount rate	3.17%	4.24%
Effective interest rate on benefit obligation	2.73%	3.88%
Expected long-term rate of return on assets	6.00%	6.00%
United States | Other postretirement employee benefits
Defined Benefit Plan, Weighted Average Assumptions Used in Calculating Benefit Obligation [Abstract]
Discount rate	1.93%	2.95%
Non-U.S. | Pension benefits
Defined Benefit Plan, Weighted Average Assumptions Used in Calculating Benefit Obligation [Abstract]
Discount rate	1.44%	1.61%
Rate of compensation increase	3.23%	3.05%
Defined Benefit Plan, Weighted Average Assumptions Used in Calculating Net Periodic Benefit Cost [Abstract]
Discount rate	1.69%	2.28%
Effective interest rate on benefit obligation	2.19%	2.06%
Expected long-term rate of return on assets	4.75%	5.23%
Average rate of increase in compensation	3.10%	3.03%
United Kingdom
Defined Benefit Plan, Weighted Average Assumptions Used in Calculating Benefit Obligation [Abstract]
Discount rate	1.39%	1.97%
Defined Benefit Plan, Weighted Average Assumptions Used in Calculating Net Periodic Benefit Cost [Abstract]
Discount rate	1.82%	2.76%
Effective interest rate on benefit obligation	3.97%	5.00%