GOODWILL - Roll Forward (Details) $ in Thousands	6 Months Ended
	Jun. 30, 2016 USD ($)
Goodwill [Roll Forward]
Balance as of January 1, 2016	$ 115,930
Effect of net foreign currency exchange rate changes	132
Balance as of June 30, 2016	110,668
North America
Goodwill [Roll Forward]
Balance as of January 1, 2016	81,464
Effect of net foreign currency exchange rate changes	142
Balance as of June 30, 2016	76,212
Europe
Goodwill [Roll Forward]
Balance as of January 1, 2016	34,466
Effect of net foreign currency exchange rate changes	(10)
Balance as of June 30, 2016	34,456
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	(8,014)
AGS | North America
Goodwill [Roll Forward]
Purchase accounting adjustments	(8,014)
AGS | Europe
Goodwill [Roll Forward]
Purchase accounting adjustments	0
Other Acquisitions
Goodwill [Roll Forward]
Acquisition	590
Other Acquisitions | North America
Goodwill [Roll Forward]
Acquisition	590
Other Acquisitions | Europe
Goodwill [Roll Forward]
Acquisition	$ 0