Quarterly report pursuant to Section 13 or 15(d)

Share Repurchase Program - Additional Information (Detail)

v3.19.3
Share Repurchase Program - Additional Information (Detail) - USD ($)
$ / shares in Units, $ in Millions
9 Months Ended
Sep. 30, 2019
Dec. 31, 2018
Feb. 06, 2018
Class of Stock [Line Items]      
Stock repurchase program expiration date Feb. 06, 2021    
Class A Common Stock [Member]      
Class of Stock [Line Items]      
Common Stock, par value $ 0.001 $ 0.001  
Stock repurchase program authorized amount     $ 150.0
Stock repurchase program remaining authorized repurchase amount $ 20.0    
Class A Common Stock [Member] | Share Repurchase Program [Member]      
Class of Stock [Line Items]      
Common Stock, par value     $ 0.001