Stock-Based Awards - Compensation (Details) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2020	Mar. 31, 2019
Stock-based compensation expense
Stock-based compensation expense	$ 3,453	$ 4,272
Unrecognized stock-based compensation cost, options	10,292
Unrecognized compensation, RSUs	10,689
Cost of revenue.
Stock-based compensation expense
Stock-based compensation expense	260	206
Research and development
Stock-based compensation expense
Stock-based compensation expense	816	1,594
General and administrative
Stock-based compensation expense
Stock-based compensation expense	$ 2,377	$ 2,472
Options to purchase common stock
Stock-based compensation expense
Weighted average recognition period unrecognized stock-based compensation cost (in years)	1 year 8 months 19 days
Restricted stock unit awards
Stock-based compensation expense
Weighted average recognition period unrecognized stock-based compensation cost (in years)	2 years 3 months 7 days

Amount of expense for award under share-based payment arrangement. Excludes amount capitalized.

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