Condensed Consolidated Statement of Convertible and Redeemable Convertible Preferred Stock and Stockholders' Deficit - 6 months ended Jun. 30, 2015 - USD ($) $ in Thousands	Total	Common Stock [Member]	Additional Paid-In Capital [Member]	Accumulated Other Comprehensive Loss [Member]	Accumulated Deficit [Member]	Convertible Preferred Stock [Member]	Redeemable Convertible Preferred Stock [Member]
Stockholders Equity, Beginning Balance at Dec. 31, 2014	$ (107,815)	$ 2		$ (10)	$ (107,807)
Stockholders Equity, Beginning Balance, Shares at Dec. 31, 2014	1,588,701	1,588,701
Temporary Equity, Beginning Balance at Dec. 31, 2014	$ 144,375					$ 2,543	$ 141,832
Temporary Equity, Beginning Balance, Shares at Dec. 31, 2014	17,266,628					224,564	17,042,064
Issuance of common stock for exercise of stock options	$ 15		$ 15
Issuance of common stock for exercise of stock options, Shares		27,813
Stock-based compensation	600		600
Issuance of redeemable convertible preferred stock upon exercise of redeemable convertible preferred stock warrants for cash							$ 1,392
Issuance of redeemable convertible preferred stock upon exercise of redeemable convertible preferred stock warrants for cash, Shares							91,275
Adjustment to redemption value on redeemable convertible preferred stock	(151,885)		$ (615)		(151,270)		$ 151,885
Reclassification of other-than-temporary losses on short-term investments to net loss	10			$ 10
Net loss	(23,297)				(23,297)
Stockholders Equity, Ending Balance at Jun. 30, 2015	$ (282,372)	$ 2			$ (282,374)
Stockholders Equity, Ending Balance, Shares at Jun. 30, 2015	1,616,514	1,616,514
Temporary Equity, Ending Balance at Jun. 30, 2015	$ 297,652					$ 2,543	$ 295,109
Temporary Equity, Ending Balance, Shares at Jun. 30, 2015	17,357,903					224,564	17,133,339