Quarterly report pursuant to Section 13 or 15(d)

Equity - Summary of Authorized and Outstanding Equity (Parenthetical) (Detail)

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Equity - Summary of Authorized and Outstanding Equity (Parenthetical) (Detail) - $ / shares
 3 Months Ended 12 Months Ended
Mar. 31, 2021
Dec. 31, 2020
Mar. 31, 2020
Dec. 31, 2019
Class Of Stock [Line Items]        
Preferred stock, par value $ 0.01 $ 0.01    
Class A Common Stock        
Class Of Stock [Line Items]        
Common stock, par value $ 0.01 $ 0.01    
Common stock, voting rights one vote for each share      
Common stockholders rights percentage 100.00%      
Restricted stock units granted 0 8,242    
Restricted stock units unvested 8,242      
Common stock, shares outstanding 9,658,297 9,650,692 9,506,000 9,330,000
Class B Common Stock        
Class Of Stock [Line Items]        
Common stock, par value $ 0.01 $ 0.01    
Common stock, voting rights one vote for each share      
Restricted stock units granted 74,907      
Class of share exchangeable to another class one-for-one basis      
Common stock, shares outstanding 4,769,835 4,721,646 4,855,000 5,031,000