Common Stock - Summary of Reserved Common Stock for Future Issuances (Detail)	Dec. 31, 2014	Dec. 31, 2013
Class Of Stock [Line Items]
Common Stock, Capital Shares Reserved for Future Issuance	3,900,281	12,078,240
Convertible preferred stock [Member]
Class Of Stock [Line Items]
Common Stock, Capital Shares Reserved for Future Issuance		10,491,140
Stock Compensation Plan [Member]
Class Of Stock [Line Items]
Common Stock, Capital Shares Reserved for Future Issuance	991,401	9,533
Options to purchase common stock [Member]
Class Of Stock [Line Items]
Common Stock, Capital Shares Reserved for Future Issuance	2,723,366	1,403,655
Restricted Stock Units [Member]
Class Of Stock [Line Items]
Common Stock, Capital Shares Reserved for Future Issuance	185,514
Warrants to purchase convertible preferred stock [Member]
Class Of Stock [Line Items]
Common Stock, Capital Shares Reserved for Future Issuance		173,912