ACQUIRED INTANGIBLE ASSETS, NET (Summary of Acquired Intangible Assets) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Finite-Lived Intangible Assets [Line Items]
Intangible Assets, Deletions			$ 26,700
Finite-lived Intangible Assets Acquired	$ 80,979		80,979		$ 116,893
Finite-Lived Intangible Assets, Accumulated Amortization	28,108		28,108		52,869
Finite-Lived Intangible Assets, Translation Adjustments			5,431		5,652
Impairment of intangible assets	(2,226)	$ (9,252)	(2,226)	$ (9,252)	(9,252)
Acquired intangible assets, net	47,440		47,440		49,120
Technology Equipment [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-lived Intangible Assets Acquired	5,228		5,228		10,308
Finite-Lived Intangible Assets, Accumulated Amortization	4,597		4,597		9,677
Finite-Lived Intangible Assets, Translation Adjustments			631		631
Impairment of intangible assets					0
Acquired intangible assets, net	0		0		0
Trademarks, Other [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-lived Intangible Assets Acquired	13,394		13,394		23,194
Finite-Lived Intangible Assets, Accumulated Amortization	8,436		8,436		14,379
Finite-Lived Intangible Assets, Translation Adjustments			2,185		2,286
Impairment of intangible assets					(3,168)
Acquired intangible assets, net	2,773		2,773		3,361
Customer Lists [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-lived Intangible Assets Acquired	14,500		14,500		28,473
Finite-Lived Intangible Assets, Accumulated Amortization	6,721		6,721		13,518
Finite-Lived Intangible Assets, Translation Adjustments			2,112		2,112
Impairment of intangible assets					(6,084)
Acquired intangible assets, net	5,667		5,667		6,759
Candidate Database [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-lived Intangible Assets Acquired	8,857		8,857		15,918
Finite-Lived Intangible Assets, Accumulated Amortization	8,354		8,354		15,295
Finite-Lived Intangible Assets, Translation Adjustments			503		623
Impairment of intangible assets					0
Acquired intangible assets, net	0		0		0
Trademarks [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-lived Intangible Assets Acquired	39,000		39,000		39,000
Finite-Lived Intangible Assets, Accumulated Amortization	0		0		0
Finite-Lived Intangible Assets, Translation Adjustments			0		0
Impairment of intangible assets					0
Acquired intangible assets, net	$ 39,000		$ 39,000		$ 39,000