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Stockholders' Equity - Summary of Stockholders' Equity (Detail) - shares
 12 Months Ended
Dec. 31, 2018
Dec. 31, 2017
Dec. 31, 2016
Class A Common Stock      
Class Of Stock [Line Items]      
Common stock, shares outstanding, beginning balance 2,426,107 2,419,107  
Share conversion 10,000,000    
Issued 9,450 7,000 8,000
Common stock, shares outstanding, ending balance 12,435,557 2,426,107 2,419,107
Class B Common Stock      
Class Of Stock [Line Items]      
Common stock, shares outstanding, beginning balance 10,000,000 10,000,000  
Share conversion (10,000,000)    
Common stock, shares outstanding, ending balance 10,000,000 10,000,000