Condensed Consolidated Statements of Comprehensive Loss (unaudited) - (Parenthetical) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Stock-based compensation expenses	$ 7,004	$ 5,022	$ 13,099	$ 9,219
Cost of revenues
Stock-based compensation expenses	1,065	819	2,080	1,543
Sales and marketing
Stock-based compensation expenses	1,428	812	2,654	1,443
Research and development
Stock-based compensation expenses	1,566	1,033	2,922	1,978
General and administrative
Stock-based compensation expenses	$ 2,945	$ 2,358	$ 5,443	$ 4,255