Annual report pursuant to Section 13 and 15(d)

Commitments And Contingencies (Narrative) (Details)

v2.4.1.9
Commitments And Contingencies (Narrative) (Details) (USD $)
In Thousands, unless otherwise specified
 12 Months Ended
Jan. 03, 2015
Dec. 28, 2013
Dec. 29, 2012
Commitments And Contingencies [Line Items]      
Total rent expense $ 11,129us-gaap_OperatingLeasesRentExpenseNet $ 9,254us-gaap_OperatingLeasesRentExpenseNet $ 6,452us-gaap_OperatingLeasesRentExpenseNet
Unconditional purchase obligations due in one year 15,746us-gaap_UnrecordedUnconditionalPurchaseObligationBalanceOnFirstAnniversary    
Unconditional purchase obligations due in two years 4,752us-gaap_UnrecordedUnconditionalPurchaseObligationBalanceOnSecondAnniversary    
Minimum employee age to partake in 401(k) 18 years    
Requisite service period to partake in 401(k) 1 month    
Employers' percentage match of employee's contribution percentage 100.00%usna_DefinedContributionPlanEmployerMatchingContributionMatchPercentage    
Percentage of employee's gross pay that is matched by the employer 1.00%us-gaap_DefinedContributionPlanEmployerMatchingContributionPercent    
Employers' percentage match of employee's contribution percentage over one percent 50.00%usna_DefinedContributionPlanEmployerMatchingContributionMatchPercentExceedingInitialMatch    
Employers' maximum contribution of employee's compensation 6.00%us-gaap_DefinedContributionPlanMaximumAnnualContributionsPerEmployeePercent    
Requisite service in order to cliff vest 2 years    
Contributions made by the Company $ 1,324usna_DefinedContributionPlanEmployerContributionAmount $ 1,149usna_DefinedContributionPlanEmployerContributionAmount $ 1,024usna_DefinedContributionPlanEmployerContributionAmount
Buildings [Member]      
Commitments And Contingencies [Line Items]      
Lease expiration date 2020    
Equipment [Member]      
Commitments And Contingencies [Line Items]      
Lease expiration date 2019