Quarterly report pursuant to Section 13 or 15(d)

Summary of Significant Accounting Policies - Summary of Outstanding Potentially Dilutive Securities Excluded in Calculation of Diluted Net Loss Per Share (Detail)

v3.19.2
Summary of Significant Accounting Policies - Summary of Outstanding Potentially Dilutive Securities Excluded in Calculation of Diluted Net Loss Per Share (Detail) - shares
shares in Thousands
6 Months Ended
Jun. 30, 2019
Jun. 30, 2018
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]    
Outstanding potentially dilutive securities 6,424 8,393
ESPP shares pending issuance [Member]    
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]    
Outstanding potentially dilutive securities 0 6
Warrants to purchase common stock [Member] | Common Stock [Member]    
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]    
Outstanding potentially dilutive securities 13 13
Common stock options issued and outstanding [Member]    
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]    
Outstanding potentially dilutive securities 6,411 5,528
Shares issuable upon conversion of convertible note payable [Member]    
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]    
Outstanding potentially dilutive securities 0 2,846