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Segment Information (Percentage Of Total Product Revenue Contributed By Company's Nutritional And Care Products) (Details)
 3 Months Ended
Apr. 04, 2015
Mar. 29, 2014
USANA Nutritionals [Member]    
Revenue from External Customer [Line Items]    
Percentage of product revenue 81.00%usna_PercentageOfProductRevenue
/ us-gaap_ProductOrServiceAxis
= usna_UsanaNutritionalsMember		 79.00%usna_PercentageOfProductRevenue
/ us-gaap_ProductOrServiceAxis
= usna_UsanaNutritionalsMember
USANA Foods [Member]    
Revenue from External Customer [Line Items]    
Percentage of product revenue 11.00%usna_PercentageOfProductRevenue
/ us-gaap_ProductOrServiceAxis
= usna_UsanaFoodsMember		 13.00%usna_PercentageOfProductRevenue
/ us-gaap_ProductOrServiceAxis
= usna_UsanaFoodsMember
Sense - Beautiful Science [Member]    
Revenue from External Customer [Line Items]    
Percentage of product revenue 7.00%usna_PercentageOfProductRevenue
/ us-gaap_ProductOrServiceAxis
= usna_SenseBeautifulScienceMember		 6.00%usna_PercentageOfProductRevenue
/ us-gaap_ProductOrServiceAxis
= usna_SenseBeautifulScienceMember