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v3.10.0.1

Segment Information (Narrative) (Details) | 12 Months Ended
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Dec. 29, 2018 item segment
Segment Information [Abstract] |
Number of reportable segments | segment | 1
Geographic regions | 2
Sub-geographical regions | 3

X
- Definition Number of segments reported by the entity. A reportable segment is a component of an entity for which there is an accounting requirement to report separate financial information on that component in the entity's financial statements. + References No definition available. + Details
Name: | us-gaap_NumberOfReportableSegments
Namespace Prefix: | us-gaap_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | duration

X
- References No definition available. + Details
Name: | us-gaap_SegmentReportingAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Number Of Geographic Regions + References No definition available. + Details
Name: | usna_NumberOfGeographicRegions
Namespace Prefix: | usna_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | duration

X
- Definition Number Of Sub Geographical Regions + References No definition available. + Details
Name: | usna_NumberOfSubGeographicalRegions
Namespace Prefix: | usna_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | duration