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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Aggregate number of common shares reserved for future issuance.

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Net number of share options (or share units) granted during the period.

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

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Stock Option and Incentive Plans (Details) (USD $) In Thousands, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Jan. 01, 2015
Stock option
2005 Stock option and incentive plans
Stock options outstanding	1,670,574	1,093,208	689,663
Total stock based compensation expense	$ 698	$ 236
Stock option \| Research and development
2005 Stock option and incentive plans
Total stock based compensation expense	137	15
Stock option \| General and administrative
2005 Stock option and incentive plans
Total stock based compensation expense	$ 561	$ 221
2005 Plan
2005 Stock option and incentive plans
Common stock reserved for issuance (in shares)	0
Stock options outstanding	970,574
2014 Plan
2005 Stock option and incentive plans
Common stock reserved for issuance (in shares)	0
Stock options outstanding	700,000
Options issued (in shares)	54,000
2014 Plan \| Subsequent event
2005 Stock option and incentive plans
Common stock reserved for issuance (in shares)				560,310