Quarterly report pursuant to Section 13 or 15(d)

Equity - Class B Common Stock (Detail)

v3.8.0.1
Equity - Class B Common Stock (Detail) - Class B Common Stock - shares
1 Months Ended 3 Months Ended
Mar. 31, 2018
Jan. 31, 2018
Mar. 31, 2018
Mar. 31, 2017
Dec. 31, 2017
Dec. 31, 2016
Class Of Stock [Line Items]            
Common stock conversion date 2018-03 2018-01        
Common stock, shares outstanding 4,942,383   4,942,383 4,840,000 5,059,319 4,866,000
Cancellation of Class B common stock upon conversion of Class B units to Class A common stock     117,000 26,000    
Resale And Registration Rights Agreement            
Class Of Stock [Line Items]            
Cancellation of Class B common stock upon conversion of Class B units to Class A common stock (85,286) (31,650)