Stock-Based Compensation - Summary of Reserved Shares Outstanding (Details) - shares	Dec. 31, 2015	Dec. 31, 2014
Stock-based compensation
Reserved shares of common stock	14,531,538	13,140,916
Warrant
Stock-based compensation
Reserved shares of common stock		90,000
Stock options to purchase common stock
Stock-based compensation
Reserved shares of common stock	11,312,218	10,480,891
RSUs
Stock-based compensation
Reserved shares of common stock	258,878	897,231
Shares available for future grant
Stock-based compensation
Reserved shares of common stock	2,960,442	1,672,794