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
 6 Months Ended 12 Months Ended
Jun. 30, 2021
Dec. 31, 2020
Mar. 31, 2021
Jun. 30, 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 11,635 8,242        
Restricted stock units unvested 19,877          
Common stock, shares outstanding 9,669,760 9,650,692 9,658,000 9,520,000 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 170,854          
Class of share exchangeable to another class one-for-one basis          
Common stock, shares outstanding 4,781,844 4,721,646 4,770,000 4,852,000 4,855,000 5,031,000