REVENUE FROM CONTRACTS WITH CUSTOMERS - Narrative (Details) - Product Concentration Risk - Revenue	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Transportation services
Disaggregation of Revenue [Line Items]
Percentage of revenues attributable to services	91.00%	92.00%	91.00%
Sourcing
Disaggregation of Revenue [Line Items]
Percentage of revenues attributable to services	7.00%	6.00%	7.00%
Value-added logistics services
Disaggregation of Revenue [Line Items]
Percentage of revenues attributable to services	2.00%	2.00%	2.00%