Reportable Segments - Summary of Segment Description (Detail)	6 Months Ended
Jun. 28, 2019
SPS [Member]
Segment Reporting Information [Line Items]
Product or Services	Assembly Weldments Machining Fabrication
Markets Served	Semiconductor
Geographic Areas	United States Asia Europe
SSB [Member]
Segment Reporting Information [Line Items]
Product or Services	Cleaning Analytics
Markets Served	Semiconductor
Geographic Areas	United States Asia Europe

Basis for attributing revenues from external customers to individual countries.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 38
-URI http://asc.fasb.org/extlink&oid=115929826&loc=d3e9003-108599

+ Details

Name:	us-gaap_BasisForAttributingRevenuesFromExternalCustomersToIndividualCountries
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Description of the types of products and services from which the reportable segment derives its revenue.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 21
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=115929826&loc=d3e8721-108599

+ Details

Name:	us-gaap_DescriptionOfTypesOfProductsAndServicesFromWhichEachReportableSegmentDerivesItsRevenues
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Description of the factors used to identify reportable segments, including the basis of organization (for example, whether management has chosen to organize the enterprise around differences in products and services, geographic areas, regulatory environments, or a combination of factors and whether operating segments have been aggregated to reportable segments).

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 21
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=115929826&loc=d3e8721-108599

+ Details

Name:	us-gaap_FactorsUsedToIdentifyEntitysReportableSegments
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

Name:	us-gaap_SegmentReportingInformationLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	us-gaap_StatementBusinessSegmentsAxis=uctt_SemiconductorProductsAndSolutionsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementBusinessSegmentsAxis=uctt_SemiconductorServicesBusinessMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: