RETIREMENT BENEFITS - Assumptions Used (Details)	3 Months Ended		12 Months Ended
	Mar. 31, 2019	Jun. 30, 2018	Dec. 31, 2018	Mar. 31, 2018
U.S. | Postretirement Benefit Plans
Plan Assumptions - During the year
Discount rate	4.20%		4.20%
Plan Assumptions - At year end
Discount rate	3.80%		4.20%	3.90%
Non-U.S. plans | Pension Plans | Weighted Average
Plan Assumptions - During the year
Discount rate	5.09%		5.08%
Plan Assumptions - At year end
Discount rate	4.74%		5.09%	4.88%
Non-U.S. plans | Pension Plans | Minimum
Plan Assumptions - During the year
Discount rate	0.75%	0.95%
Plan Assumptions - At year end
Discount rate	0.45%		0.75%	0.75%
Non-U.S. plans | Pension Plans | Maximum
Plan Assumptions - During the year
Discount rate	10.75%	10.75%
Plan Assumptions - At year end
Discount rate	10.30%		10.75%	9.90%
Non-U.S. plans | Postretirement Benefit Plans
Plan Assumptions - During the year
Discount rate	10.75%		10.10%
Plan Assumptions - At year end
Discount rate	10.30%		10.75%	9.50%
Qualified plans | U.S. | Pension Plans
Plan Assumptions - During the year
Discount rate	4.25%		4.30%
Plan Assumptions - At year end
Discount rate	3.85%		4.25%	3.95%
Nonqualified plans | U.S. | Pension Plans
Plan Assumptions - During the year
Discount rate	4.25%		4.30%
Plan Assumptions - At year end
Discount rate	3.90%		4.25%	3.95%