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Stock Repurchase Plans - Additional Information (Detail) - USD ($)
 1 Months Ended 12 Months Ended
Dec. 31, 2020
Nov. 30, 2020
Oct. 31, 2020
Sep. 30, 2020
Aug. 31, 2020
Jul. 31, 2020
Jun. 30, 2020
May 31, 2020
Apr. 30, 2020
Feb. 28, 2020
Jan. 31, 2020
Dec. 31, 2020
Dec. 31, 2019
Dec. 31, 2018
May 23, 2019
Equity Class Of Treasury Stock [Line Items]                              
Purchase of treasury shares (in shares) 68,433 1,883 435 126 123 1,647 389 1,318 2,171 2,571 69,146 148,242      
Purchase of treasury shares                         $ 24,998,000    
Class A Common Stock [Member]                              
Equity Class Of Treasury Stock [Line Items]                              
Stock repurchase program, authorized amount                             $ 100,000,000
Purchase of treasury shares (in shares)                       0 626,320    
Purchase of treasury shares                         $ 25,000,000.0    
Class A Common Stock [Member] | Employee Restricted Stock Plan [Member]                              
Equity Class Of Treasury Stock [Line Items]                              
Purchase of treasury shares                       $ 8,000,000.0 $ 4,000,000.0 $ 4,300,000  
Stock tendered for payments of withholding taxes (in shares)                       148,242 98,260 87,381