GOODWILL AND INTANGIBLE ASSETS (Details) $ in Thousands	6 Months Ended
	Jun. 30, 2018 USD ($)
GOODWILL
Goodwill impairment	$ 0
Goodwill
Balance at the beginning of the period	302,702
Goodwill acquired and adjustments to previously recorded goodwill	(38,133)
Foreign currency translation adjustment	(544)
Balance at the end of the period	264,025
Flatbed
Goodwill
Balance at the beginning of the period	105,866
Goodwill acquired and adjustments to previously recorded goodwill	(23,955)
Balance at the end of the period	81,911
Specialized
Goodwill
Balance at the beginning of the period	196,836
Goodwill acquired and adjustments to previously recorded goodwill	(14,178)
Foreign currency translation adjustment	(544)
Balance at the end of the period	$ 182,114