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.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
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Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
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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
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (i)
-URI http://asc.fasb.org/extlink&oid=109197908&loc=d3e5070-113901

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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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Equity Compensation (Expense) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Stock options
Total stock-based compensation expense
Total stock-based compensation expense	$ 3,429	$ 3,028	$ 10,085	$ 9,191
Total unrecognized compensation cost related to non-vested stock option awards	1,000		$ 1,000
Weighted-average period over which unrecognized compensation cost will be recognized			6 months
Stock options \| Cost of revenue
Total stock-based compensation expense
Total stock-based compensation expense	59	66	$ 182	185
Stock options \| Research and development
Total stock-based compensation expense
Total stock-based compensation expense	1,115	1,031	3,233	3,210
Stock options \| Sales and marketing
Total stock-based compensation expense
Total stock-based compensation expense	941	883	2,877	2,831
Stock options \| General and administrative
Total stock-based compensation expense
Total stock-based compensation expense	1,314	$ 1,048	3,793	$ 2,965
Restricted stock units
Total stock-based compensation expense
Total unrecognized compensation cost related to non-vested restricted stock units	$ 13,400		$ 13,400
Weighted-average period over which unrecognized compensation cost will be recognized			1 year 9 months 18 days