ACQUISITIONS (Estimated Fair Values) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Sep. 30, 2016	Nov. 16, 2015	Jul. 10, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Oct. 31, 2014	Jun. 06, 2014	Apr. 30, 2014	Mar. 05, 2014
Business Acquisition [Line Items]
Goodwill	$ 109,289	$ 115,930						$ 57,417
2015 Acquisitions | NavigationArts
Business Acquisition [Line Items]
Adjustment to net assets acquired	1,797
Goodwill deductable for tax purposes					$ 23,794
2015 Acquisitions | AGS
Business Acquisition [Line Items]
Adjustment to net assets acquired	(140)
2015 Acquisitions | As Originally Reported | NavigationArts
Business Acquisition [Line Items]
Cash and cash equivalents					1,317
Accounts receivable and other current assets					3,920
Property and equipment and other long-term assets					230
Deferred tax assets					0
Acquired intangible assets					1,500
Goodwill					23,822
Total assets acquired					30,789
Accounts payable and accrued expenses					871
Bank loans and other long-term liabilities					0
Deferred revenue					50
Due to employees					596
Deferred tax liabilities					525
Total liabilities assumed					2,042
Net assets acquired					$ 28,747
2015 Acquisitions | As Originally Reported | AGS
Business Acquisition [Line Items]
Cash and cash equivalents				$ 1,727
Accounts receivable and other current assets				10,600
Property and equipment and other long-term assets				1,665
Deferred tax assets				4,996
Acquired intangible assets				10,000
Goodwill				33,815
Total assets acquired				62,803
Accounts payable and accrued expenses				3,087
Bank loans and other long-term liabilities				0
Deferred revenue				1,049
Due to employees				3,010
Deferred tax liabilities				3,800
Total liabilities assumed				10,946
Net assets acquired				$ 51,857
2015 Acquisitions | As Originally Reported | Total
Business Acquisition [Line Items]
Cash and cash equivalents		3,044
Accounts receivable and other current assets		14,520
Property and equipment and other long-term assets		1,895
Deferred tax assets		4,996
Acquired intangible assets		11,500
Goodwill		57,637
Total assets acquired		93,592
Accounts payable and accrued expenses		3,958
Bank loans and other long-term liabilities		0
Deferred revenue		1,099
Due to employees		3,606
Deferred tax liabilities		4,325
Total liabilities assumed		12,988
Net assets acquired		80,604
2015 Acquisitions | Final Valuation [Member] | NavigationArts
Business Acquisition [Line Items]
Cash and cash equivalents			$ 1,317
Accounts receivable and other current assets			3,920
Property and equipment and other long-term assets			230
Deferred tax assets			0
Acquired intangible assets			2,800
Goodwill			23,794
Total assets acquired			32,061
Accounts payable and accrued expenses			871
Bank loans and other long-term liabilities			0
Deferred revenue			50
Due to employees			596
Deferred tax liabilities			0
Total liabilities assumed			1,517
Net assets acquired			$ 30,544
2015 Acquisitions | Final Valuation [Member] | AGS
Business Acquisition [Line Items]
Cash and cash equivalents	1,727
Accounts receivable and other current assets	9,934
Property and equipment and other long-term assets	1,600
Deferred tax assets	5,722
Acquired intangible assets	22,700
Goodwill	24,454
Total assets acquired	66,137
Accounts payable and accrued expenses	2,760
Bank loans and other long-term liabilities	295
Deferred revenue	1,049
Due to employees	2,342
Deferred tax liabilities	7,974
Total liabilities assumed	14,420
Net assets acquired	51,717
2015 Acquisitions | Final Valuation [Member] | Total
Business Acquisition [Line Items]
Cash and cash equivalents	3,044
Accounts receivable and other current assets	13,854
Property and equipment and other long-term assets	1,830
Deferred tax assets	5,722
Acquired intangible assets	25,500
Goodwill	48,248
Total assets acquired	98,198
Accounts payable and accrued expenses	3,631
Bank loans and other long-term liabilities	295
Deferred revenue	1,099
Due to employees	2,938
Deferred tax liabilities	7,974
Total liabilities assumed	15,937
Net assets acquired	$ 82,261
2014 Acquisition | Netsoft
Business Acquisition [Line Items]
Adjustment to net assets acquired		(348)
Goodwill deductable for tax purposes												$ 924
2014 Acquisition | Jointech
Business Acquisition [Line Items]
Adjustment to net assets acquired		0
2014 Acquisition | GGA
Business Acquisition [Line Items]
Adjustment to net assets acquired		1,366
Goodwill deductable for tax purposes										$ 7,306
2014 Acquisition | Great Fridays
Business Acquisition [Line Items]
Adjustment to net assets acquired		(77)
2014 Acquisition | As Originally Reported | Netsoft
Business Acquisition [Line Items]
Cash and cash equivalents												0
Accounts receivable and other current assets												788
Property and equipment and other long-term assets												52
Deferred tax assets												351
Acquired intangible assets												1,700
Goodwill												2,776
Total assets acquired												5,667
Accounts payable and accrued expenses												69
Deferred revenue												0
Due to employees												0
Deferred tax liabilities												0
Total liabilities assumed												69
Net assets acquired												$ 5,598
2014 Acquisition | As Originally Reported | Jointech
Business Acquisition [Line Items]
Cash and cash equivalents											$ 871
Accounts receivable and other current assets											784
Property and equipment and other long-term assets											338
Deferred tax assets											0
Acquired intangible assets											25,744
Goodwill											11,033
Total assets acquired											38,770
Accounts payable and accrued expenses											728
Deferred revenue											0
Due to employees											1,254
Deferred tax liabilities											0
Total liabilities assumed											1,982
Net assets acquired											$ 36,788
2014 Acquisition | As Originally Reported | GGA
Business Acquisition [Line Items]
Cash and cash equivalents										0
Accounts receivable and other current assets										5,157
Property and equipment and other long-term assets										444
Deferred tax assets										4,463
Acquired intangible assets										10,959
Goodwill										6,496
Total assets acquired										27,519
Accounts payable and accrued expenses										2,593
Deferred revenue										0
Due to employees										0
Deferred tax liabilities										0
Total liabilities assumed										2,593
Net assets acquired										$ 24,926
2014 Acquisition | As Originally Reported | Great Fridays
Business Acquisition [Line Items]
Cash and cash equivalents									$ 259
Accounts receivable and other current assets									1,825
Property and equipment and other long-term assets									262
Deferred tax assets									0
Acquired intangible assets									5,747
Goodwill									6,947
Total assets acquired									15,040
Accounts payable and accrued expenses									872
Deferred revenue									317
Due to employees									624
Deferred tax liabilities									1,200
Total liabilities assumed									3,013
Net assets acquired									$ 12,027
2014 Acquisition | As Originally Reported | Total
Business Acquisition [Line Items]
Cash and cash equivalents								1,130
Accounts receivable and other current assets								8,554
Property and equipment and other long-term assets								1,096
Deferred tax assets								4,814
Acquired intangible assets								44,150
Goodwill								27,252
Total assets acquired								86,996
Accounts payable and accrued expenses								4,262
Deferred revenue								317
Due to employees								1,878
Deferred tax liabilities								1,200
Total liabilities assumed								7,657
Net assets acquired								$ 79,339
2014 Acquisition | Final Valuation [Member] | Netsoft
Business Acquisition [Line Items]
Cash and cash equivalents							$ 0
Accounts receivable and other current assets							788
Property and equipment and other long-term assets							52
Deferred tax assets							0
Acquired intangible assets							1,700
Goodwill							2,779
Total assets acquired							5,319
Accounts payable and accrued expenses							69
Deferred revenue							0
Due to employees							0
Deferred tax liabilities							0
Total liabilities assumed							69
Net assets acquired							$ 5,250
2014 Acquisition | Final Valuation [Member] | Jointech
Business Acquisition [Line Items]
Cash and cash equivalents						$ 871
Accounts receivable and other current assets						784
Property and equipment and other long-term assets						338
Deferred tax assets						0
Acquired intangible assets						15,312
Goodwill						23,758
Total assets acquired						41,063
Accounts payable and accrued expenses						728
Deferred revenue						0
Due to employees						1,254
Deferred tax liabilities						2,293
Total liabilities assumed						4,275
Net assets acquired						36,788
2014 Acquisition | Final Valuation [Member] | GGA
Business Acquisition [Line Items]
Cash and cash equivalents						0
Accounts receivable and other current assets						5,377
Property and equipment and other long-term assets						306
Deferred tax assets						0
Acquired intangible assets						16,000
Goodwill						7,306
Total assets acquired						28,989
Accounts payable and accrued expenses						2,593
Deferred revenue						104
Due to employees						0
Deferred tax liabilities						0
Total liabilities assumed						2,697
Net assets acquired						$ 26,292
2014 Acquisition | Final Valuation [Member] | Great Fridays
Business Acquisition [Line Items]
Cash and cash equivalents		259
Accounts receivable and other current assets		1,825
Property and equipment and other long-term assets		262
Deferred tax assets		0
Acquired intangible assets		200
Goodwill		11,262
Total assets acquired		13,808
Accounts payable and accrued expenses		807
Deferred revenue		317
Due to employees		624
Deferred tax liabilities		110
Total liabilities assumed		1,858
Net assets acquired		11,950
2014 Acquisition | Final Valuation [Member] | Total
Business Acquisition [Line Items]
Cash and cash equivalents		1,130
Accounts receivable and other current assets		8,774
Property and equipment and other long-term assets		958
Deferred tax assets		0
Acquired intangible assets		33,212
Goodwill		45,105
Total assets acquired		89,179
Accounts payable and accrued expenses		4,197
Deferred revenue		421
Due to employees		1,878
Deferred tax liabilities		2,403
Total liabilities assumed		8,899
Net assets acquired		$ 80,280