XML 62 R48.htm IDEA: XBRL DOCUMENT v3.19.3.a.u2
Stockholders' Equity - Summary of Common Stock Reserved for Future Issuance (Details) - shares
Dec. 31, 2019
Dec. 31, 2018
Dec. 31, 2017
Dec. 31, 2016
Stockholders Equity Note [Abstract]        
Stock options outstanding 16,664,640 15,264,607 13,462,964 11,845,376
Stock options available for grant 4,971,000      
Employee Stock Purchase Plan 370,000      
Warrants outstanding 508,000      
Shares of common stock underlying Convertible Notes outstanding (see Note 8) 8,960,000      
Total shares reserved for future issuance 31,474,000