Quarterly report pursuant to Section 13 or 15(d)

Business and Credit Concentrations - Company's Top Five Manufacturers Produced (Detail)

v3.8.0.1
Business and Credit Concentrations - Company's Top Five Manufacturers Produced (Detail) - Cost of Goods, Total [Member] - Supplier Concentration Risk [Member]
3 Months Ended 9 Months Ended
Sep. 30, 2017
Sep. 30, 2016
Sep. 30, 2017
Sep. 30, 2016
Concentration Risk [Line Items]        
Percentage of total production 47.90% 45.00% 49.80% 52.20%
Manufacturer One [Member]        
Concentration Risk [Line Items]        
Percentage of total production 17.00% 19.00% 19.80% 23.80%
Manufacturer Two [Member]        
Concentration Risk [Line Items]        
Percentage of total production 10.40% 9.50% 10.80% 10.00%
Manufacturer Three [Member]        
Concentration Risk [Line Items]        
Percentage of total production 9.80% 8.30% 9.00% 9.50%
Manufacturer Four [Member]        
Concentration Risk [Line Items]        
Percentage of total production 5.60% 4.20% 5.90% 5.00%
Manufacturer Five [Member]        
Concentration Risk [Line Items]        
Percentage of total production 5.10% 4.00% 4.30% 3.90%