Represents the expense recognized during the period arising from equity-based compensation arrangements (for example, shares of stock, unit, stock options or other equity instruments) with employees, directors and certain consultants qualifying for treatment as employees.

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

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- Definition

Weighted average period over which unrecognized compensation is expected to be recognized for equity-based compensation plans, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
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-Topic 718
-SubTopic 10
-Section 50
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- Definition

Unrecognized cost of unvested share-based awards, other than options, awarded to employees as compensation.

+ References

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- Definition

Unrecognized cost of unvested options awarded to employees as compensation.

+ References

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Stock-Based Awards - Compensation (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Stock-based compensation expense
Stock-based compensation expense	$ 4,024	$ 3,947	$ 12,894	$ 12,412
Unrecognized stock-based compensation cost, options	17,068		17,068
Unrecognized compensation, RSUs	11,506		11,506
Cost of revenue.
Stock-based compensation expense
Stock-based compensation expense	25	194	454	560
Research and development
Stock-based compensation expense
Stock-based compensation expense	1,418	1,433	4,733	4,916
General and administrative
Stock-based compensation expense
Stock-based compensation expense	$ 2,581	$ 2,320	$ 7,707	$ 6,936
Options to purchase common stock
Stock-based compensation expense
Weighted average recognition period unrecognized stock-based compensation cost (in years)			1 year 11 months 16 days
Restricted stock unit awards
Stock-based compensation expense
Weighted average recognition period unrecognized stock-based compensation cost (in years)			2 years 10 months 24 days