Common Stock and Stockholders' Equity Common Stock and Stockholders’ Equity (Details 1) $ in Thousands	12 Months Ended
	Dec. 31, 2015 USD ($) vote shares	Dec. 31, 2014 USD ($) shares	Dec. 31, 2013 USD ($)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock, shares outstanding (in shares)	52,669,266	48,944,530
Common stock voting rights per share (vote) | vote	1
Proceeds from exercise of common stock options | $	$ 6,680	$ 2,233	$ 594
Common stock options outstanding	5,125,667	6,643,000
Total common shares reserved for future issuance	8,893,018
Common stock available for future grant under the 2012 Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock available for future grant under the 2012 Plan	1,549,163
Common stock available for future grant under the Inducement Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock available for future grant under the 2012 Plan	958,052
Employee Stock Purchase Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock available for future grant under the 2012 Plan	1,260,136
Common stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock, shares outstanding (in shares)	52,669,266