Annual report pursuant to Section 13 and 15(d)

Stockholders' Equity - Summary of Stock-based Compensation Expense Recognized in Income Statement (Details)

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Stockholders' Equity - Summary of Stock-based Compensation Expense Recognized in Income Statement (Details) - USD ($)
$ in Thousands
 12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Class Of Stock [Line Items]      
Stock-based compensation expense $ 9,640 $ 7,294 $ 3,640
Cost of Revenue      
Class Of Stock [Line Items]      
Stock-based compensation expense 845 639 433
Research and Development      
Class Of Stock [Line Items]      
Stock-based compensation expense 1,015 776 431
Sales and Marketing      
Class Of Stock [Line Items]      
Stock-based compensation expense 1,558 1,142 1,009
General and Administrative      
Class Of Stock [Line Items]      
Stock-based compensation expense $ 6,222 $ 4,737 $ 1,767