Warrants (Details)		1 Months Ended	12 Months Ended
	Nov. 20, 2014 $ / shares shares	Jul. 31, 2015 shares	Dec. 31, 2015 $ / shares shares	Apr. 30, 2014 $ / shares shares	Apr. 30, 2013 $ / shares	Dec. 31, 2009 $ / shares shares	Dec. 31, 2007 $ / shares shares
Class of Stock [Line Items]
Warrants outstanding (in shares)							24,538
Warrants exercise price (in dollars per share) | $ / shares							$ 0.0978
Secured Loan Arrangement
Class of Stock [Line Items]
Warrants outstanding (in shares)				376,691
Warrants exercise price (in dollars per share) | $ / shares				$ 2.3229	$ 2.3229
B
Class of Stock [Line Items]
Warrants outstanding (in shares)						33,742
Warrants exercise price (in dollars per share) | $ / shares						$ 1.8908
E
Class of Stock [Line Items]
Warrants outstanding (in shares)	429,440
Warrants exercise price (in dollars per share) | $ / shares	$ 0.0163
Liquidation preference change (as a percent)	2
Common stock
Class of Stock [Line Items]
Closing price (in dollars per share) | $ / shares			$ 11.57
Conversion into common shares (in shares)			31,397,000
Common stock | B
Class of Stock [Line Items]
Common stock issued for each warrant (in shares)		1	28,227
Common stock | E
Class of Stock [Line Items]
Conversion into common shares (in shares)		429,042