Quarterly report pursuant to Section 13 or 15(d)

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

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Business and Credit Concentrations - Company's Top Five Manufacturers Produced (Detail) - Cost of Goods, Total [Member] - Supplier Concentration Risk [Member]
 3 Months Ended 6 Months Ended
Jun. 30, 2015
Jun. 30, 2014
Jun. 30, 2015
Jun. 30, 2014
Concentration Risk [Line Items]        
Percentage of total production 58.10% 57.70% 58.20% 57.90%
Manufacturer One [Member]        
Concentration Risk [Line Items]        
Percentage of total production 32.80% 35.80% 33.50% 36.30%
Manufacturer Two [Member]        
Concentration Risk [Line Items]        
Percentage of total production 7.50% 7.10% 7.90% 6.30%
Manufacturer Three [Member]        
Concentration Risk [Line Items]        
Percentage of total production 7.40% 6.00% 7.20% 5.70%
Manufacturer Four [Member]        
Concentration Risk [Line Items]        
Percentage of total production 6.90% 4.90% 5.70% 5.30%
Manufacturer Five [Member]        
Concentration Risk [Line Items]        
Percentage of total production 3.50% 3.90% 3.90% 4.30%