Quarterly report pursuant to Section 13 or 15(d)

Stockholders' Equity - Additional Information (Detail)

v3.20.2
Stockholders' Equity - Additional Information (Detail) - USD ($)
3 Months Ended 6 Months Ended 12 Months Ended
Feb. 28, 2020
Jan. 03, 2020
Jul. 18, 2019
Feb. 25, 2019
Jun. 30, 2020
Jun. 30, 2020
Jun. 30, 2019
Dec. 31, 2017
Dec. 31, 2019
Jul. 31, 2019
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]                    
Authorized capital stock         520,000,000 520,000,000        
Common stock, par value         $ 0.0001 $ 0.0001     $ 0.0001  
Common stock, shares authorized         500,000,000 500,000,000     500,000,000  
Preferred stock, par value         $ 0.0001 $ 0.0001        
Preferred stock, shares authorized         20,000,000 20,000,000        
Preferred stock, shares outstanding         0 0     0  
Proceeds from sale of common stock, net           $ 24,172,000 $ 7,630,000      
Stock option granted description terms           the exercise price of an option granted to a 10% shareholder cannot be less than 110% of the estimated fair value of the shares on the date of grant. Options granted generally vest over four years and expire in seven to ten years.        
Ownership percent           10.00%        
Shares of common stock, reserved for issuance         16,335,544 16,335,544        
2014 Equity Incentive Plan                    
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]                    
Shares of common stock, reserved for issuance         14,127,804 14,127,804        
Aggregate number of awards available for grant to be issued         2,213,656 2,213,656        
Outstanding options and RSUs         11,914,148 11,914,148        
Inducement Plan                    
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]                    
Shares of common stock, reserved for issuance         1,141,086 1,141,086        
Aggregate number of awards available for grant to be issued         170,773 170,773        
Outstanding options and RSUs         970,313 970,313        
Restricted Stock Units (RSUs)                    
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]                    
Unrecognized stock-based compensation expense         $ 54,000,000.0 $ 54,000,000.0        
Unrecognized stock-based compensation weighted average recognition period           2 years 8 months 12 days        
Restricted Stock Units (RSUs) | From Date Of Grant                    
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]                    
Share based compensation, vesting period           4 years        
Employees And Non Employees                    
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]                    
Share based compensation, vesting period           4 years        
Vested and Unvested Options                    
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]                    
Unrecognized stock-based compensation weighted average recognition period           2 years 10 months 24 days        
Stock options, issued               275,000    
Unrecognized stock-based compensation         $ 63,300,000 $ 63,300,000        
Maximum | Employees And Non Employees                    
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]                    
Share based compensation award expiration period           10 years        
Minimum                    
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]                    
Percentage of employees purchase price of common stock           100.00%        
Minimum | 10% Shareholder                    
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]                    
Percentage of employees purchase price of common stock           110.00%        
Minimum | Employees And Non Employees                    
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]                    
Share based compensation award expiration period           7 years        
Underwritten Public Offering                    
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]                    
Common stock, shares issued         12,633,039          
Shares issued, price per share         $ 11.32 $ 11.32        
Option price to purchase shares         $ 11.32 $ 11.32        
Proceeds from sale of common stock, gross         $ 201,800,000          
Net proceeds from sale of common stock         $ 189,300,000          
Exercise of warrants           $ 0        
Common stock, shares issued         12,633,039          
Proceeds from sale of common stock, gross         $ 201,800,000          
Underwritten Public Offering | 2020 Warrants                    
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]                    
Warrants outstanding         2,866,961 2,866,961        
Underwritten Public Offering | 2019 Warrants                    
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]                    
Number of warrants issued                   2,945,026
Warrants outstanding         2,888,526 2,888,526        
Underwritten Public Offering | Maximum                    
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]                    
Additional shares of our common stock         2,325,000          
Underwritten Public Offering | Warrant                    
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]                    
Number of warrants issued         2,866,961 2,866,961        
Warrant, price per share         $ 11.3199 $ 11.3199        
Number of securities called by each warrant     1              
Warrants, exercise price     $ 0.0001              
Warrants, term     7 years              
Maximum ownership Percentage     9.99%              
Underwritten Public Offering | Warrant | Maximum                    
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]                    
Maximum ownership Percentage     19.99%              
Underwritten Public Offering | Warrant | Minimum                    
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]                    
Prior notice period     61 days              
At The Market Offering | Cowen                    
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]                    
Common stock, shares issued         0 1,528,216        
Proceeds from sale of common stock, gross           $ 23,700,000        
Common stock, shares issued         0 1,528,216        
Common stock average price           $ 15.50        
Proceeds from sale of common stock, gross           $ 23,700,000        
Proceeds from sale of common stock, net   $ 1,200,000       23,000,000.0        
At The Market Offering | Maximum | Cowen                    
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]                    
Common stock aggregate offering price $ 100,000,000.0     $ 100,000,000.0            
Percentage of commission to be paid on gross sales proceeds of common stock sold 3.00%     3.00%            
2019 ATM Facility | Cowen                    
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]                    
Common stock value remaining to be sold         $ 25,900,000 25,900,000        
2020 ATM Facility | Cowen                    
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]                    
Common stock value remaining to be sold         $ 100,000,000.0 $ 100,000,000.0