Quarterly report pursuant to Section 13 or 15(d)

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

v3.10.0.1
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, 2018
Sep. 30, 2017
Sep. 30, 2018
Sep. 30, 2017
Concentration Risk [Line Items]        
Percentage of total production 40.30% 47.90% 41.90% 49.80%
Manufacturer One [Member]        
Concentration Risk [Line Items]        
Percentage of total production 11.10% 17.00% 11.30% 19.80%
Manufacturer Two [Member]        
Concentration Risk [Line Items]        
Percentage of total production 10.10% 10.40% 10.70% 10.80%
Manufacturer Three [Member]        
Concentration Risk [Line Items]        
Percentage of total production 6.80% 9.80% 9.10% 9.00%
Manufacturer Four [Member]        
Concentration Risk [Line Items]        
Percentage of total production 6.70% 5.60% 5.40% 5.90%
Manufacturer Five [Member]        
Concentration Risk [Line Items]        
Percentage of total production 5.60% 5.10% 5.40% 4.30%