ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS) - Realized gain/losses reclassified from AOCI (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Realized (Gains)/Losses Reclassified from Accumulated Other Comprehensive Income
Cost of revenues	$ (300,450)	$ (301,986)	$ (189,209)
General and administrative	(52,170)	(68,522)	(44,212)
Sales and marketing	(150,457)	(133,780)	(97,438)
Research and development	(365,878)	(322,620)	(252,175)
Other income, net	3,115	1,090	$ (524)
Realized (gains)/losses reclassified from accumulated other comprehensive income	(7,023)	(137)
Realized (gains) on derivatives designated as hedging instruments
Realized (Gains)/Losses Reclassified from Accumulated Other Comprehensive Income
Realized (gains)/losses reclassified from accumulated other comprehensive income	(7,034)	(623)
Realized losses on available-for-sale securities
Realized (Gains)/Losses Reclassified from Accumulated Other Comprehensive Income
Realized (gains)/losses reclassified from accumulated other comprehensive income	11	486
Realized (Gains)/Losses Reclassified from Accumulated Other Comprehensive Income \| Realized (gains) on derivatives designated as hedging instruments
Realized (Gains)/Losses Reclassified from Accumulated Other Comprehensive Income
Operating Costs and Expenses	(7,034)	(623)
Cost of revenues	(347)	(18)
General and administrative	(635)	(36)
Sales and marketing	(628)	(25)
Research and development	(5,424)	(544)
Realized (Gains)/Losses Reclassified from Accumulated Other Comprehensive Income \| Realized losses on available-for-sale securities
Realized (Gains)/Losses Reclassified from Accumulated Other Comprehensive Income
Other income, net	$ 11	$ 486

The aggregate cost of goods produced and sold and services rendered during the reporting period.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 225
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03.2)
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+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 225
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03.4)
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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 225
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03.9)
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Reference 1: http://www.xbrl.org/2003/role/presentationRef
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-SubTopic 10
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The aggregate costs incurred (1) in a planned search or critical investigation aimed at discovery of new knowledge with the hope that such knowledge will be useful in developing a new product or service, a new process or technique, or in bringing about a significant improvement to an existing product or process; or (2) to translate research findings or other knowledge into a plan or design for a new product or process or for a significant improvement to an existing product or process whether intended for sale or the entity's use, during the reporting period charged to research and development projects, including the costs of developing computer software up to the point in time of achieving technological feasibility, and costs allocated in accounting for a business combination to in-process projects deemed to have no alternative future use.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
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