NATURE OF OPERATIONS AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Property and Equipment (Details)	12 Months Ended
	Dec. 31, 2020
Minimum | Buildings and improvements
Property and Equipment
Estimated useful lives	10 years
Minimum | Leasehold improvements
Property and Equipment
Estimated useful lives	5 years
Minimum | Revenue equipment - tractors, trailers and accessories
Property and Equipment
Estimated useful lives	5 years
Minimum | Assets leased and available for lease to owner operators
Property and Equipment
Estimated useful lives	1 year
Minimum | Vehicles
Property and Equipment
Estimated useful lives	5 years
Minimum | Furniture and fixtures
Property and Equipment
Estimated useful lives	5 years
Minimum | Office, computer equipment and capitalized software development
Property and Equipment
Estimated useful lives	5 years
Maximum | Buildings and improvements
Property and Equipment
Estimated useful lives	40 years
Maximum | Leasehold improvements
Property and Equipment
Estimated useful lives	20 years
Maximum | Revenue equipment - tractors, trailers and accessories
Property and Equipment
Estimated useful lives	15 years
Maximum | Assets leased and available for lease to owner operators
Property and Equipment
Estimated useful lives	5 years
Maximum | Vehicles
Property and Equipment
Estimated useful lives	7 years
Maximum | Furniture and fixtures
Property and Equipment
Estimated useful lives	7 years
Maximum | Office, computer equipment and capitalized software development
Property and Equipment
Estimated useful lives	5 years