GOODWILL AND INTANGIBLE ASSETS - NET (Goodwill Roll Forward) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Goodwill [Roll Forward]
Balance beginning of period				$ 57,417				$ 22,268	$ 57,417	$ 22,268
Goodwill written-off	$ 0	$ 0	$ 0	0	$ (2,241)	$ 0	$ 0	0	0	(2,241)	$ 0
Net effect of foreign currency exchange rate changes									(2,785)	(1,825)
Balance end of period	115,930				57,417				115,930	57,417	22,268
North America
Goodwill [Roll Forward]
Balance beginning of period				31,078				16,438	31,078	16,438
Goodwill written-off										0
Net effect of foreign currency exchange rate changes									(416)	(224)
Balance end of period	81,464				31,078				81,464	31,078	16,438
Europe
Goodwill [Roll Forward]
Balance beginning of period				26,339				2,864	26,339	2,864
Goodwill written-off										0
Net effect of foreign currency exchange rate changes									(2,369)	(876)
Balance end of period	34,466				26,339				34,466	26,339	2,864
Russia
Goodwill [Roll Forward]
Balance beginning of period				$ 0				$ 2,966	0	2,966
Goodwill written-off										(2,241)
Net effect of foreign currency exchange rate changes									0	(725)
Balance end of period	$ 0				$ 0				0	0	$ 2,966
Netsoft
Goodwill [Roll Forward]
Acquisition										2,749
Goodwill, Purchase Accounting Adjustments									30
Netsoft | North America
Goodwill [Roll Forward]
Acquisition										2,749
Goodwill, Purchase Accounting Adjustments									30
Netsoft | Europe
Goodwill [Roll Forward]
Acquisition										0
Goodwill, Purchase Accounting Adjustments									0
Netsoft | Russia
Goodwill [Roll Forward]
Acquisition										0
Goodwill, Purchase Accounting Adjustments									0
Jointech
Goodwill [Roll Forward]
Acquisition										17,404
Goodwill, Purchase Accounting Adjustments									6,181
Jointech | North America
Goodwill [Roll Forward]
Acquisition										0
Goodwill, Purchase Accounting Adjustments									0
Jointech | Europe
Goodwill [Roll Forward]
Acquisition										17,404
Goodwill, Purchase Accounting Adjustments									6,181
Jointech | Russia
Goodwill [Roll Forward]
Acquisition										0
Goodwill, Purchase Accounting Adjustments									0
GGA
Goodwill [Roll Forward]
Acquisition										12,115
Goodwill, Purchase Accounting Adjustments									(4,807)
GGA | North America
Goodwill [Roll Forward]
Acquisition										12,115
Goodwill, Purchase Accounting Adjustments									(4,807)
GGA | Europe
Goodwill [Roll Forward]
Acquisition										0
Goodwill, Purchase Accounting Adjustments									0
GGA | Russia
Goodwill [Roll Forward]
Acquisition										0
Goodwill, Purchase Accounting Adjustments									0
Great Fridays
Goodwill [Roll Forward]
Acquisition										6,947
Goodwill, Purchase Accounting Adjustments									4,315
Great Fridays | North America
Goodwill [Roll Forward]
Acquisition										0
Goodwill, Purchase Accounting Adjustments									0
Great Fridays | Europe
Goodwill [Roll Forward]
Acquisition										6,947
Goodwill, Purchase Accounting Adjustments									4,315
Great Fridays | Russia
Goodwill [Roll Forward]
Acquisition										$ 0
Goodwill, Purchase Accounting Adjustments									0
NavigationArts
Goodwill [Roll Forward]
Acquisition									23,822
Goodwill, Purchase Accounting Adjustments									(2,058)
NavigationArts | North America
Goodwill [Roll Forward]
Acquisition									23,822
Goodwill, Purchase Accounting Adjustments									(2,058)
NavigationArts | Europe
Goodwill [Roll Forward]
Acquisition									0
Goodwill, Purchase Accounting Adjustments									0
NavigationArts | Russia
Goodwill [Roll Forward]
Acquisition									0
Goodwill, Purchase Accounting Adjustments									0
AGS
Goodwill [Roll Forward]
Acquisition									33,815
AGS | North America
Goodwill [Roll Forward]
Acquisition									33,815
AGS | Europe
Goodwill [Roll Forward]
Acquisition									0
AGS | Russia
Goodwill [Roll Forward]
Acquisition									$ 0