Quarterly report pursuant to Section 13 or 15(d)

Company's Top Five Manufacturers Produced (Detail)

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Company's Top Five Manufacturers Produced (Detail)
 3 Months Ended 9 Months Ended
Sep. 30, 2012
Sep. 30, 2011
Sep. 30, 2012
Sep. 30, 2011
Concentration Risk [Line Items]        
Total Manufacturers Produced 64.20% 58.70% 63.10% 62.50%
Company's top five manufacturers produced
        
Concentration Risk [Line Items]        
Manufacturer #1 33.70% 24.50% 34.30% 29.50%
Manufacturer #2 11.00% 12.60% 9.80% 11.60%
Manufacturer #3 7.20% 9.00% 6.70% 8.10%
Manufacturer #4 6.50% 6.30% 6.60% 6.90%
Manufacturer #5 5.80% 6.30% 5.70% 6.40%