Quarterly report pursuant to Section 13 or 15(d)

Equity - Class A Common Stock (Detail)

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Equity - Class A Common Stock (Detail) - Class A Common Stock - shares
1 Months Ended
May 31, 2017
Apr. 30, 2017
Mar. 31, 2017
Jun. 30, 2017
Dec. 31, 2016
Jun. 30, 2016
Dec. 31, 2015
Class Of Stock [Line Items]              
Common stock, shares outstanding       8,107,101 8,074,197 8,028,000 7,990,000
Issuance of Class A common stock upon conversion of Class B units to Class A common stock 2,000   26,008        
Issuance of Class B shares, Shares 3,896 1,000          
Common stock conversion date May 31, 2017   Mar. 31, 2017        
Stock issued upon vesting of stock units 2017-05 2017-04