NATURE OF BUSINESS AND SIGNIFICANT ACCOUNTING POLICIES (Risks and Uncertainties) (Details) $ in Thousands	12 Months Ended
Dec. 31, 2015 USD ($) customer	Dec. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)
Concentration Risk [Line Items]
Revenues	$ 914,128	$ 730,027	$ 555,117
Customer Concentration Risk \| Sales Revenue, Net \| Top Five Customers
Concentration Risk [Line Items]
Concentration percentage	32.60%	32.80%	30.60%
Number of customers \| customer	5
Revenues	$ 298,063	$ 239,396	$ 169,987
Customer Concentration Risk \| Sales Revenue, Net \| Top Ten Customers
Concentration Risk [Line Items]
Concentration percentage	43.80%	43.90%	42.30%
Number of customers \| customer	10
Revenues	$ 400,250	$ 320,126	$ 234,955
CIS Countries \| Geographic Concentration Risk \| Assets, Total
Concentration Risk [Line Items]
Cash	103,700
Belarus \| Geographic Concentration Risk \| Assets, Total
Concentration Risk [Line Items]
Cash	$ 79,500

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+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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+ References

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