Net Loss Per Share	6 Months Ended
Jun. 30, 2019
Earnings Per Share [Abstract]
Net Loss Per Share	3. Net Loss Per Share Basic net loss per share is computed by dividing the net loss by the weighted average number of common shares outstanding for the period, without consideration for potentially dilutive securities. Diluted net loss per share is computed by dividing the net loss by the weighted average number of common shares and dilutive common share equivalents outstanding for the period determined using the treasury-stock and if-converted methods. For purposes of this calculation, convertible preferred stock, stock options, employee stock purchase rights, and unvested common stock subject to repurchase are considered to be common stock equivalents but are not included in the calculations of diluted net loss per share for the periods presented as their effect would be antidilutive. The Company incurred net losses for all periods presented and there were no reconciling items for potentially dilutive securities. More specifically, at June 30, 2019 and 2018, convertible preferred stock, stock options, employee stock purchase rights, and unvested common stock subject to repurchase totaling approximately 4,800,000 shares and 17,500,000 shares, respectively, were excluded from the calculation of diluted net loss per share because to do so would be anti-dilutive.

Net Loss Per Share

6 Months Ended

Jun. 30, 2019

3. Net Loss Per Share

Basic net loss per share is computed by dividing the net loss by the weighted average number of common shares outstanding for the period, without consideration for potentially dilutive securities. Diluted net loss per share is computed by dividing the net loss by the weighted average number of common shares and dilutive common share equivalents outstanding for the period determined using the treasury-stock and if-converted methods. For purposes of this calculation, convertible preferred stock, stock options, employee stock purchase rights, and unvested common stock subject to repurchase are considered to be common stock equivalents but are not included in the calculations of diluted net loss per share for the periods presented as their effect would be antidilutive. The Company incurred net losses for all periods presented and there were no reconciling items for potentially dilutive securities. More specifically, at June 30, 2019 and 2018, convertible preferred stock, stock options, employee stock purchase rights, and unvested common stock subject to repurchase totaling approximately 4,800,000 shares and 17,500,000 shares, respectively, were excluded from the calculation of diluted net loss per share because to do so would be anti-dilutive.