USANA Health Sciences, Inc. Quarterly report pursuant to Section 13 or 15(d)

Segment Information (Schedule Of Revenues From External Customers By Geographical Areas) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 30, 2019	Mar. 31, 2018
Revenues from External Customers and Long-Lived Assets [Line Items]
Net Sales to External Customers	$ 272,990	$ 291,998
Greater China [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Net Sales to External Customers	144,153	157,808
Southeast Asia Pacific [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Net Sales to External Customers	54,515	56,228
North Asia [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Net Sales to External Customers	22,228	18,084
Asia Pacific [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Net Sales to External Customers	220,896	232,120
Americas And Europe [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Net Sales to External Customers	$ 52,094	$ 59,878