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)
 3 Months Ended 6 Months Ended
Jun. 30, 2013
Jun. 30, 2012
Jun. 30, 2013
Jun. 30, 2012
Concentration Risk [Line Items]        
Total manufacturers produced 60.40% 64.60% 58.60% 62.50%
Company's top five manufacturers produced [Member]
        
Concentration Risk [Line Items]        
Manufacturer #1 34.50% 34.60% 33.20% 34.70%
Manufacturer #2 7.40% 9.30% 7.90% 9.10%
Manufacturer #3 7.30% 8.00% 6.70% 6.70%
Manufacturer #4 6.60% 6.40% 5.90% 6.40%
Manufacturer #5 4.60% 6.30% 4.90% 5.60%