Annual report pursuant to Section 13 and 15(d)

Equity - Additional Information (Detail)

v3.10.0.1
Equity - Additional Information (Detail) - USD ($)
$ / shares in Units, $ in Millions
 1 Months Ended 12 Months Ended
Mar. 31, 2018
Dec. 31, 2018
Dec. 31, 2017
Equity [Line Items]      
Ownership percentage of common stock shares outstanding of chairman   82.00%  
Class B Common Stock Converted Into Class A Common Stock [Member]      
Equity [Line Items]      
Stock conversion ratio   100.00%  
Class B Common Stock [Member]      
Equity [Line Items]      
Common stock, shares outstanding   5,400,000 5,400,000
Common stock voting rights   ten votes on all matters submitted to a vote of shareholders.  
Class B Common Stock [Member] | Board of Directors Chairman [Member]      
Equity [Line Items]      
Ownership percentage of common stock shares outstanding of chairman   100.00%  
Common stock, shares outstanding   5,400,000  
Class A Common Stock [Member]      
Equity [Line Items]      
Common stock, shares outstanding   12,500,139 9,752,531
Common stock voting rights   one vote for each share held on all matters submitted to a vote of shareholders.  
Class A Common Stock [Member] | Underwritten Public Offering [Member]      
Equity [Line Items]      
Common stock shares issued 2,683,333    
Public offering price per share $ 15.00    
Net proceeds from issuance of shares $ 37.1    
Class A Common Stock [Member] | Over-Allotment Option [Member] | Underwriters [Member]      
Equity [Line Items]      
Common stock shares issued 350,000    
Class A Common Stock [Member] | Board of Directors Chairman [Member]      
Equity [Line Items]      
Common stock, shares outstanding   366,682