Quarterly report pursuant to Section 13 or 15(d)

Stock Compensation - Additional Information (Detail)

v3.19.1
Stock Compensation - Additional Information (Detail) - USD ($)
$ in Thousands
3 Months Ended
Mar. 31, 2019
Mar. 31, 2018
Apr. 17, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Share-based compensation expense $ 8,900 $ 8,700  
Stock redeemed, value 5,816 $ 8,718  
Unrecognized compensation cost related to nonvested common shares $ 108,200    
Weighted average period for recognition of cost 2 years 8 months 12 days    
Class A Common Stock [Member]      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Stock redeemed, shares 170,073 212,930  
Stock redeemed, value $ 5,800 $ 8,700  
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%    
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