Segment Information (Schedule Of Revenue Percentage By Product) (Details)	3 Months Ended		9 Months Ended
	Sep. 28, 2019	Sep. 29, 2018	Sep. 28, 2019	Sep. 29, 2018
USANA Nutritionals [Member]
Revenue from External Customer [Line Items]
Percentage of product revenue	81.00%	83.00%	83.00%	82.00%
USANA Foods [Member]
Revenue from External Customer [Line Items]
Percentage of product revenue	9.00%	9.00%	8.00%	9.00%
Personal Care and Skincare [Member]
Revenue from External Customer [Line Items]
Percentage of product revenue	9.00%	7.00%	8.00%	8.00%
All Other [Member]
Revenue from External Customer [Line Items]
Percentage of product revenue	1.00%	1.00%	1.00%	1.00%