Common Stock Reserved for Future Issuance (Details) - shares	Sep. 30, 2015	Dec. 31, 2014
Stockholders' equity
Shares reserved for future issuance (in shares)	2,814,716	9,445,451
Series A Convertible Preferred Stock
Stockholders' equity
Shares reserved for future issuance (in shares)		5,356,996
Series B Convertible Preferred Stock
Stockholders' equity
Shares reserved for future issuance (in shares)		2,655,992
Warrants for the purchase of Preferred Stock
Stockholders' equity
Shares reserved for future issuance (in shares)		12,283
Warrants for the purchase of Common Stock
Stockholders' equity
Shares reserved for future issuance (in shares)	59,405	34,839
Options to purchase Common Stock
Stockholders' equity
Shares reserved for future issuance (in shares)	2,572,959	1,385,341
Employee Stock Purchase Plan
Stockholders' equity
Shares reserved for future issuance (in shares)	182,352