ACQUIRED INTANGIBLE ASSETS, NET (Summary of Acquired Intangible Assets) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Finite-Lived Intangible Assets [Line Items]
Intangible Assets, Deletions	$ 44,100
Finite-lived Intangible Assets Acquired	116,893	$ 160,988
Finite-Lived Intangible Assets, Accumulated Amortization	52,869	86,883
Finite-Lived Intangible Assets, Translation Adjustments	5,652	8,813
Impairment of intangible assets	(9,252)	0	$ 0
Acquired intangible assets, net	49,120	65,292
Technology Equipment [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-lived Intangible Assets Acquired	10,308	10,308
Finite-Lived Intangible Assets, Accumulated Amortization	9,677	8,831
Finite-Lived Intangible Assets, Translation Adjustments	631	615
Impairment of intangible assets	0
Acquired intangible assets, net	0	862
Trademarks, Other [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-lived Intangible Assets Acquired	23,194	23,419
Finite-Lived Intangible Assets, Accumulated Amortization	14,379	13,156
Finite-Lived Intangible Assets, Translation Adjustments	2,286	2,238
Impairment of intangible assets	(3,168)
Acquired intangible assets, net	3,361	8,025
Customer Lists [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-lived Intangible Assets Acquired	28,473	63,373
Finite-Lived Intangible Assets, Accumulated Amortization	13,518	42,808
Finite-Lived Intangible Assets, Translation Adjustments	2,112	5,068
Impairment of intangible assets	(6,084)
Acquired intangible assets, net	6,759	15,497
Candidate Database [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-lived Intangible Assets Acquired	15,918	24,888
Finite-Lived Intangible Assets, Accumulated Amortization	15,295	22,088
Finite-Lived Intangible Assets, Translation Adjustments	623	892
Impairment of intangible assets	0
Acquired intangible assets, net	0	1,908
Trademarks [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-lived Intangible Assets Acquired	39,000	39,000
Finite-Lived Intangible Assets, Accumulated Amortization	0	0
Finite-Lived Intangible Assets, Translation Adjustments	0	0
Impairment of intangible assets	0
Acquired intangible assets, net	$ 39,000	$ 39,000