GOODWILL (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Goodwill and Intangible Assets Disclosure [Abstract]
Carrying amount of goodwill in foreign countries	$ 46,300	$ 42,700
Changes in the carrying amount of goodwill
Goodwill balance at the beginning of the period	255,665	249,939
Goodwill acquired	87,261	8,613
Goodwill adjustments due to currency translation	3,588	(2,887)
Goodwill balance at the end of the period	$ 346,514	$ 255,665