v3.19.1
Redeemable Convertible Preferred Stock - Additional Information (Detail) - USD ($)
$ in Thousands
 1 Months Ended 12 Months Ended
Jul. 02, 2018
Apr. 30, 2017
Feb. 28, 2017
Dec. 31, 2018
Dec. 31, 2017
Class of Stock [Line Items]          
Increase (decrease) to additional paid-in capital and accumulated deficit       $ 37,415 $ 14,093
Series A Redeemable Convertible Preferred Stock [Member]          
Class of Stock [Line Items]          
Conversion of stock, shares converted     97,943    
Series B Redeemable Convertible Preferred Stock [Member]          
Class of Stock [Line Items]          
Conversion of stock, shares converted   132,749      
Series B-1 Preferred Stock [Member]          
Class of Stock [Line Items]          
Conversion of stock, common stock issued   132,749      
Series B and B-1 Redeemable Convertible Preferred Stock [Member]          
Class of Stock [Line Items]          
Adjustment to carrying value       $ 37,400 $ 14,100
Class B Common Stock [Member]          
Class of Stock [Line Items]          
Conversion of stock, shares converted       4,116,404 24,000
Conversion of stock, common stock issued 12,596,064        
Redeemable Preferred Stock [Member]          
Class of Stock [Line Items]          
Conversion of stock, shares converted 1,574,508        
Common Stock [Member]          
Class of Stock [Line Items]          
Conversion of stock, common stock issued     783,544    
Additional Paid-in Capital [Member]          
Class of Stock [Line Items]          
Increase (decrease) to additional paid-in capital and accumulated deficit       $ 2,633 $ 7,759
Additional Paid-in Capital [Member] | Series B and B-1 Redeemable Convertible Preferred Stock [Member]          
Class of Stock [Line Items]          
Increase (decrease) to additional paid-in capital and accumulated deficit       $ 37,400 $ 14,100