Quarterly report pursuant to Section 13 or 15(d)

Summary of Significant Accounting Policies and Nature of Operations - Additional Information (Detail)

v2.4.1.9
Summary of Significant Accounting Policies and Nature of Operations - Additional Information (Detail) (USD $)
 3 Months Ended 0 Months Ended
Apr. 04, 2015
warranty_service_level
segment
Mar. 29, 2014
Oct. 08, 2014
Jan. 03, 2015
Schedule Of Significant Accounting Policies [Line Items]        
Net (loss) income attributable to U.S. Auto Parts stockholders' $ (60,000)us-gaap_NetIncomeLoss $ 201,000us-gaap_NetIncomeLoss    
Other than temporary impairment charges on investments 0us-gaap_ImpairmentOfInvestments 0us-gaap_ImpairmentOfInvestments    
Inventory 48,347,000us-gaap_InventoryNet 48,362,000us-gaap_InventoryNet   48,362,000us-gaap_InventoryNet
Inventory in-transit 10,669,000us-gaap_OtherInventoryInTransit 12,155,000us-gaap_OtherInventoryInTransit    
Catalog amortization period 9 months      
Warranty coverage period 30 days      
Standard product warranty useful life, minimum 1 year      
Standard product warranty useful life, maximum 5 years      
Number of warranty service levels 3prts_ExtendedProductWarrantyNumberofWarrantyServiceLevels      
Five year unlimited product replacement, coverage period 5 years      
Five year one-time product replacement period, coverage period 5 years      
Three year one-time product replacement period, coverage period 3 years      
Advertising costs 4,977,000us-gaap_AdvertisingExpense 4,390,000us-gaap_AdvertisingExpense    
Number of reportable segments 2us-gaap_NumberOfReportableSegments      
Minimum        
Schedule Of Significant Accounting Policies [Line Items]        
Stock option, vesting period 3 years      
Minimum | Website and Software Development        
Schedule Of Significant Accounting Policies [Line Items]        
Useful life 2 years      
Maximum        
Schedule Of Significant Accounting Policies [Line Items]        
Stock option, vesting period 4 years      
Maximum | Website and Software Development        
Schedule Of Significant Accounting Policies [Line Items]        
Useful life 3 years      
AutoMD        
Schedule Of Significant Accounting Policies [Line Items]        
Number of subsidiary shares issued     7,000,000us-gaap_SaleOfStockNumberOfSharesIssuedInTransaction
/ us-gaap_StatementBusinessSegmentsAxis
= prts_AutoMdMember 		 
Percentage ownership after sale of shares     64.10%us-gaap_SaleOfStockPercentageOfOwnershipAfterTransaction
/ us-gaap_StatementBusinessSegmentsAxis
= prts_AutoMdMember 		 
Percentage ownership by noncontrolling owners     35.90%us-gaap_MinorityInterestOwnershipPercentageByNoncontrollingOwners
/ us-gaap_StatementBusinessSegmentsAxis
= prts_AutoMdMember 		 
Other Current Assets        
Schedule Of Significant Accounting Policies [Line Items]        
Deferred catalog expenses $ 516,000us-gaap_DeferredAdvertisingCosts
/ us-gaap_BalanceSheetLocationAxis
= us-gaap_OtherCurrentAssetsMember 		$ 590,000us-gaap_DeferredAdvertisingCosts
/ us-gaap_BalanceSheetLocationAxis
= us-gaap_OtherCurrentAssetsMember