Quarterly report pursuant to Section 13 or 15(d)

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

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Stockholders' Equity - Summary of Stock-based Compensation Expense Recognized (Details) - USD ($)
$ in Thousands
3 Months Ended 9 Months Ended
Sep. 30, 2017
Sep. 30, 2016
Sep. 30, 2017
Sep. 30, 2016
Stock-based compensation expense by type of award:        
Stock-based compensation expense $ 2,523 $ 1,953 $ 6,630 $ 5,404
Stock Option Plan Awards        
Stock-based compensation expense by type of award:        
Stock-based compensation expense 2,012 1,858 5,811 5,063
Restricted stock units and restricted stock awards        
Stock-based compensation expense by type of award:        
Stock-based compensation expense 402   450  
Employee Stock Purchase Plan        
Stock-based compensation expense by type of award:        
Stock-based compensation expense $ 109 $ 95 $ 369 $ 341