Preferred Stock and Stockholders' Equity - Summary of Common Stock Reserved for Future Issuance (Details) - shares shares in Thousands	Dec. 31, 2016	Dec. 31, 2015
Class of Stock [Line Items]
Common stock, shares reserved for future issuance	6,315	5,367
Warrant [Member]
Class of Stock [Line Items]
Common stock, shares reserved for future issuance	1,975	1,975
Stock Options [Member]
Class of Stock [Line Items]
Common stock, shares reserved for future issuance	3,388	2,714
Employee Stock [Member]
Class of Stock [Line Items]
Common stock, shares reserved for future issuance	952	678