GOODWILL AND INTANGIBLE ASSETS (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2018 USD ($)
GOODWILL
Goodwill impairment	$ 0
Goodwill
Balance at the beginning of the period	302,702
Goodwill acquired and adjustments to previously recorded goodwill	12
Foreign currency translation adjustment	(175)
Balance at the end of the period	302,539
Flatbed
Goodwill
Balance at the beginning of the period	105,866
Balance at the end of the period	105,866
Specialized
Goodwill
Balance at the beginning of the period	196,836
Goodwill acquired and adjustments to previously recorded goodwill	12
Foreign currency translation adjustment	(175)
Balance at the end of the period	$ 196,673