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Significant Accounting Policies - Additional Information (Detail)
12 Months Ended
Sep. 30, 2016
USD ($)
Segment
Sep. 30, 2015
USD ($)
Sep. 30, 2014
USD ($)
Apr. 15, 2016
USD ($)
Significant Accounting Policies [Line Items]        
Inventories market valuation allowance $ 1,000,000 $ 1,800,000    
Goodwill 9,900,000      
Impairment charges 0      
Total advertising and promotional expenses 13,500,000 10,500,000 $ 9,500,000  
Net of related co-op assistance $ 730,000 $ 737,000 $ 473,000  
Number of reporting segment | Segment 1      
Russo Marine [Member]        
Significant Accounting Policies [Line Items]        
Goodwill       $ 8,800,000