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Stock Buy Back Plans - Additional Information (Detail) - USD ($)
 1 Months Ended 12 Months Ended
Jul. 31, 2019
Jun. 30, 2019
Dec. 31, 2019
Dec. 31, 2018
May 28, 2019
Equity Class Of Treasury Stock [Line Items]          
Purchase of treasury shares (in shares) 444,509 181,811 626,320    
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)     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     $ 4,000,000.0 $ 4,300,000  
Stock tendered for payments of withholding taxes (in shares)     98,260 87,381