ACQUISITIONS (Narrative) (Details) $ in Thousands				12 Months Ended
	Apr. 30, 2019 USD ($)	Nov. 01, 2018 USD ($)	Mar. 15, 2018 USD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2017 USD ($)
Continuum
Business Acquisition [Line Items]
Acquisition date			Mar. 15, 2018
Cash consideration			$ 52,515
Maximum amount of earnout payable			$ 3,135
Estimated future operating results, period			12 months
Continuum | Design Consultant
Business Acquisition [Line Items]
Numbers of professionals acquired			125
Think
Business Acquisition [Line Items]
Acquisition date		Nov. 01, 2018
Cash consideration		$ 26,254
Maximum amount of earnout payable		$ 8,156
Estimated future operating results, period		12 months
test IO
Business Acquisition [Line Items]
Acquisition date	Apr. 30, 2019
Cash consideration	$ 17,323
Equity interest acquired	100.00%
Other 2019 Acquisitions
Business Acquisition [Line Items]
Cash consideration				$ 24,786
Maximum amount of earnout payable				$ 3,000
Number of completed acquisitions				4
Other 2019 Acquisitions | Minimum
Business Acquisition [Line Items]
Estimated future operating results, period				12 months
Other 2019 Acquisitions | Maximum
Business Acquisition [Line Items]
Estimated future operating results, period				24 months
2017 Acquisitions
Business Acquisition [Line Items]
Cash consideration					$ 6,980