Quarterly report pursuant to Section 13 or 15(d)

Equity - Schedule of Company's Outstanding Shares of Common Stock, Treasury Shares and Additional Paid-in Capital (Detail)

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Equity - Schedule of Company's Outstanding Shares of Common Stock, Treasury Shares and Additional Paid-in Capital (Detail) - USD ($)
$ in Thousands
 9 Months Ended
May 24, 2018
May 08, 2018
Jun. 30, 2018
Schedule Of Stockholders Equity [Line Items]      
Beginning balance     $ 152,181
Issuuance of restricted shares from treasury, Value     5
Cashless option exercise     (2,492)
Equity-based compensation expense     975
Ending balance     284,325
Additional Paid-in Capital [Member]      
Schedule Of Stockholders Equity [Line Items]      
Beginning balance     142,385
Issuuance of restricted shares from treasury, Value     $ (453)
Initial public offering of Class A common stock, net of offering costs     98,000
Cashless option exercise     $ 1,586
Equity-based compensation expense     975
Ending balance     242,493
Treasury Stock [Member]      
Schedule Of Stockholders Equity [Line Items]      
Beginning balance     $ (11,983)
Beginning balance, shares     (3,296,034)
Issuuance of restricted shares from treasury, share     126,000
Issuuance of restricted shares from treasury, Value     $ 458
Cashless option exercise     $ (4,078)
Cashless option exercise, share     247,082
Ending balance     $ (15,603)
Ending balance, shares     (2,922,952)
Common Stock Undefined [Member]      
Schedule Of Stockholders Equity [Line Items]      
Beginning balance     $ 45
Beginning balance, shares     44,987,575
Issuuance of restricted shares from treasury, share     126,000
Reclassification of common stock, shares     (44,987,575)
Ending balance, shares     0
Class A Common Stock [Member]      
Schedule Of Stockholders Equity [Line Items]      
Beginning balance, shares     0
Conversion of Class B common stock to Class A common stock in connection with initial public offering of Class A common stock,Shares     2,600,000
Conversion of Class B common stock to Class A common stock in connection with initial public offering of Class A common stock,Shares     (2,600,000)
Initial public offering of Class A common stock, net of offering costs 700,000 11,250,000 9,350,000
Ending balance     $ 12
Ending balance, shares     11,950,000
Class B Common Stock [Member]      
Schedule Of Stockholders Equity [Line Items]      
Beginning balance, shares     0
Reclassification of common stock, shares     44,987,571
Conversion of Class B common stock to Class A common stock in connection with initial public offering of Class A common stock,Shares     2,600,000
Conversion of Class B common stock to Class A common stock in connection with initial public offering of Class A common stock,Shares     (2,600,000)
Cashless option exercise, share     247,082
Ending balance     $ 42
Ending balance, shares 39,217,537 39,567,537 39,464,619