Quarterly report pursuant to Section 13 or 15(d)

Stock Compensation - Additional Information (Detail)

v3.20.2
Stock Compensation - Additional Information (Detail) - USD ($)
$ in Thousands
3 Months Ended 6 Months Ended
Jun. 30, 2020
Jun. 30, 2019
Jun. 30, 2020
Jun. 30, 2019
Apr. 17, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]          
Share-based compensation expense $ 12,800 $ 10,600 $ 25,300 $ 19,500  
Stock redeemed, value   $ 7,767 5,659 $ 13,583  
Unrecognized compensation cost related to nonvested common shares $ 94,600   $ 94,600    
Weighted average period for recognition of cost     2 years 3 months 18 days    
Class A Common Stock [Member]          
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]          
Stock redeemed, shares   248,312 171,120 418,385  
Stock redeemed, value   $ 7,800 $ 5,700 $ 13,600  
2017 Plan [Member] | Class A Common Stock [Member]          
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]          
Number of shares reserved for issuance         10,000,000
2018 ESPP [Member]          
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]          
Maximum percentage of employee's compensation to purchase common stock 15.00%   15.00%    
Percentage of price of common stock purchased     85.00%    
2018 ESPP [Member] | Class A Common Stock [Member]          
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]          
Number of shares available for sale under employee stock purchase plan         5,000,000