GOODWILL AND INTANGIBLE ASSETS - NET (Goodwill Roll Forward) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Goodwill [Roll Forward]
Balance beginning of period	$ 109,289	$ 115,930
Effect of currency translation	3,695	(2,373)
Balance end of period	119,531	109,289
North America
Goodwill [Roll Forward]
Balance beginning of period	76,812	81,464
Effect of currency translation	564	(120)
Balance end of period	77,290	76,812
Europe
Goodwill [Roll Forward]
Balance beginning of period	32,477	34,466
Effect of currency translation	3,131	(2,253)
Balance end of period	42,241	32,477
Russia
Goodwill [Roll Forward]
Balance beginning of period	0	0
Balance end of period	0	0
Other
Goodwill [Roll Forward]
Balance beginning of period	0	0
Balance end of period	0	0
NavigationArts
Goodwill [Roll Forward]
Purchase accounting adjustments		2,030
NavigationArts | North America
Goodwill [Roll Forward]
Purchase accounting adjustments		2,030
NavigationArts | Europe
Goodwill [Roll Forward]
Purchase accounting adjustments		0
AGS
Goodwill [Roll Forward]
Purchase accounting adjustments		(9,361)
AGS | North America
Goodwill [Roll Forward]
Purchase accounting adjustments		(9,361)
AGS | Europe
Goodwill [Roll Forward]
Purchase accounting adjustments		0
Other Acquisitions
Goodwill [Roll Forward]
Acquisition	4,732	2,581
Purchase accounting adjustments	1,815	482
Other Acquisitions | North America
Goodwill [Roll Forward]
Acquisition	199	2,404
Purchase accounting adjustments	(285)	395
Other Acquisitions | Europe
Goodwill [Roll Forward]
Acquisition	4,533	177
Purchase accounting adjustments	$ 2,100	$ 87