Annual report pursuant to Section 13 and 15(d)

Summary Of Significant Accounting Policies (Narrative) (Details)

v2.4.1.9
Summary Of Significant Accounting Policies (Narrative) (Details) (USD $)
12 Months Ended
Jan. 03, 2015
item
Dec. 28, 2013
Dec. 29, 2012
Summary Of Significant Accounting Policies [Line Items]      
Geographical regions 2usna_NumberOfGeographicalRegions    
Sub-geographical regions 3usna_NumberOfSubGeographicalRegions    
Fair Value, Assets And Liabilities, Level 1 Between Level 2 Transfers, Amount $ 0usna_FairValueAssetsAndLiabilitiesLevel1BetweenLevel2TransfersAmount $ 0usna_FairValueAssetsAndLiabilitiesLevel1BetweenLevel2TransfersAmount  
Non-financial assets 0usna_NonfinancialAssetsFairValueDisclosure 0usna_NonfinancialAssetsFairValueDisclosure 0usna_NonfinancialAssetsFairValueDisclosure
Receivable from credit card processors 6,209,000us-gaap_OtherReceivables 5,490,000us-gaap_OtherReceivables  
Restricted cash 3,222,000us-gaap_RestrictedCashAndCashEquivalentsNoncurrent 3,296,000us-gaap_RestrictedCashAndCashEquivalentsNoncurrent  
Other-than-temporary impairments   0us-gaap_OtherThanTemporaryImpairmentLossesInvestmentsHeldtomaturitySecurities  
Estimated Fair Value 0us-gaap_HeldToMaturitySecuritiesFairValue 8,642,000us-gaap_HeldToMaturitySecuritiesFairValue  
Accumulated undistributed earnings of subsidiaries 12,296,000us-gaap_UndistributedEarningsOfForeignSubsidiaries    
Maturity date Feb. 01, 2024    
Credits on notes receivable 720,000us-gaap_NotesReduction 198,000us-gaap_NotesReduction  
Notes receivable 8,519,000us-gaap_AccountsAndNotesReceivableNet    
Impairment of goodwill 0us-gaap_GoodwillImpairmentLoss 0us-gaap_GoodwillImpairmentLoss 0us-gaap_GoodwillImpairmentLoss
Impairment of indefinite-lived intangible assets 0us-gaap_ImpairmentOfIntangibleAssetsIndefinitelivedExcludingGoodwill 0us-gaap_ImpairmentOfIntangibleAssetsIndefinitelivedExcludingGoodwill 0us-gaap_ImpairmentOfIntangibleAssetsIndefinitelivedExcludingGoodwill
Amount of individual claims before reimbursement 125,000usna_MaximumAmountOfIndividualClaimsBeforeInsuranceReimbursement    
Minimum percentage of projected aggregate claims before insurance reimbursement 100.00%usna_MinimumPercentageOfProjectedAggregateClaimsBeforeInsuranceReimbursement    
Self insurance program expense 7,019,000us-gaap_LiabilityForUnpaidClaimsAndClaimsAdjustmentExpenseClaimsPaid 5,281,000us-gaap_LiabilityForUnpaidClaimsAndClaimsAdjustmentExpenseClaimsPaid 4,518,000us-gaap_LiabilityForUnpaidClaimsAndClaimsAdjustmentExpenseClaimsPaid
Proceeds from Stock Options Exercised 10,970,000us-gaap_ProceedsFromStockOptionsExercised 454,000us-gaap_ProceedsFromStockOptionsExercised 309,000us-gaap_ProceedsFromStockOptionsExercised
Tax benefit from equity award activity 14,712,000usna_AdjustmentsToAdditionalPaidInCapitalTaxEffectFromShareBasedCompensationNetOfTaxImpact 7,075,000usna_AdjustmentsToAdditionalPaidInCapitalTaxEffectFromShareBasedCompensationNetOfTaxImpact 1,827,000usna_AdjustmentsToAdditionalPaidInCapitalTaxEffectFromShareBasedCompensationNetOfTaxImpact
Amount available to repurchase under the stock repurchase plan 61,181,000us-gaap_StockRepurchaseProgramAuthorizedAmount    
Repurchase of common stock 138,819,000us-gaap_PaymentsForRepurchaseOfCommonStock 18,085,000us-gaap_PaymentsForRepurchaseOfCommonStock 68,294,000us-gaap_PaymentsForRepurchaseOfCommonStock
Account renewal fee period 12 months    
Duration of product return for first order 30 days    
Duration of product return 1 year    
Percentage of sale refunded 100.00%usna_ProductReturnPolicyPercentageRefunded    
Restocking fee 10.00%usna_ProductReturnPolicyRestockingFeePercent    
Amount of returned product which could result in cancellation of distributorship 100usna_ProductReturnPolicyAmountOfReturnedProductWhichCouldResultInCancellationOfDistributorship    
Product return percentage of net sales 0.80%usna_ProductReturnPercentageOfNetSales 0.90%usna_ProductReturnPercentageOfNetSales 0.80%usna_ProductReturnPercentageOfNetSales
Advertising expense 4,942,000us-gaap_AdvertisingExpense 3,650,000us-gaap_AdvertisingExpense 3,942,000us-gaap_AdvertisingExpense
Research and development expense 5,128,000us-gaap_ResearchAndDevelopmentExpense 5,083,000us-gaap_ResearchAndDevelopmentExpense 4,664,000us-gaap_ResearchAndDevelopmentExpense
Manufacturing Credits [Member]      
Summary Of Significant Accounting Policies [Line Items]      
Credits on notes receivable $ 720,000us-gaap_NotesReduction
/ us-gaap_StatementScenarioAxis
= usna_ManufacturingCreditsMember
$ 198,000us-gaap_NotesReduction
/ us-gaap_StatementScenarioAxis
= usna_ManufacturingCreditsMember
 
LIBOR [Member]      
Summary Of Significant Accounting Policies [Line Items]      
Basis Points 4.00%us-gaap_DebtInstrumentBasisSpreadOnVariableRate1
/ us-gaap_VariableRateAxis
= us-gaap_LondonInterbankOfferedRateLIBORMember