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://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section S99
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Reference 2: http://www.xbrl.org/2003/role/presentationRef
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Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
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- Definition

Aggregate number of common shares reserved for future issuance.

+ References

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
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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

Number of options outstanding, including both vested and non-vested options.

+ References

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As of the balance sheet date, the weighted-average exercise price (at which grantees can acquire the shares reserved for issuance) for exercisable stock options that are fully vested or expected to vest.

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Stock Option and Incentive Plans - Incentive Plans (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Stock option and incentive plans
Total stock-based compensation expense	$ 738	$ 388	$ 1,476	$ 771
Research and development
Stock option and incentive plans
Total stock-based compensation expense	213	131	446	257
General and administrative
Stock option and incentive plans
Total stock-based compensation expense	$ 525	$ 257	$ 1,030	$ 514
Stock option
Stock option and incentive plans
Stock options outstanding	1,780,222		1,780,222
Weighted average exercise price (in dollars per share)	$ 7.91		$ 7.91
2005 Plan \| Stock option
Stock option and incentive plans
Stock options outstanding	430,922		430,922
Common stock reserved for issuance (in shares)	0		0
2014 Plan \| Stock option
Stock option and incentive plans
Stock options outstanding	1,349,300		1,349,300
Common stock reserved for issuance (in shares)	676,273		676,273