Percentage of value used for fair value of non-controlling interest estimates.

No definition available.

Name:	uctt_PercentageOfValueUsedForFairValueOfNonControllingInterestEstimates
Namespace Prefix:	uctt_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Purchase obligation maturity period.

+ References

No definition available.

+ Details

Name:	uctt_PurchaseObligationMaturityPeriod
Namespace Prefix:	uctt_
Data Type:	xbrli:gYearMonthItemType
Balance Type:	na
Period Type:	duration

- Definition

Stock purchase obligation, fair value.

+ References

No definition available.

+ Details

Name:	uctt_StockPurchaseObligationFairValue
Namespace Prefix:	uctt_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

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

- Definition

Percentage of voting equity interests acquired at the acquisition date in the business combination.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=79982066&loc=d3e1392-128463

+ Details

Name:	us-gaap_BusinessAcquisitionPercentageOfVotingInterestsAcquired
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

The equity interest of noncontrolling shareholders, partners or other equity holders in consolidated entity.

+ References

No definition available.

+ Details

Name:	us-gaap_MinorityInterestOwnershipPercentageByNoncontrollingOwners
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

The parent entity's interest in net assets of the subsidiary, expressed as a percentage.

+ References

No definition available.

+ Details

Name:	us-gaap_MinorityInterestOwnershipPercentageByParent
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Details

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Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_BusinessAcquisitionAxis=uctt_QuantumGlobalTechnologiesLLCMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	dei_LegalEntityAxis=uctt_CinosCoLtdAndCinosXianCleanTechnologyLtdMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_OwnershipAxis=uctt_QuantumGlobalTechnologiesLLCMember
Namespace Prefix:
Data Type:	na
Balance Type:
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- Details

Name:	srt_OwnershipAxis=uctt_CincosCoLtdMember
Namespace Prefix:
Data Type:	na
Balance Type:
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- Details

Name:	dei_LegalEntityAxis=uctt_CinosXianCleanTechnologyLtdMember
Namespace Prefix:
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- Details

Name:	srt_OwnershipAxis=uctt_CinosCoLtdMember
Namespace Prefix:
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Noncontrolling interest - Additional Information (Detail) - USD ($) $ in Millions	Aug. 27, 2018	Jun. 28, 2019
Cinos Co., Ltd [Member]
Business Acquisition [Line Items]
Percentage of outstanding shares purchased	35.00%
Quantum Global Technologies, LLC [Member]
Business Acquisition [Line Items]
Stock purchase obligation, fair value	$ 8.5
Purchase obligation maturity period	2022-12
Cinos Co., Ltd. and Cinos Xian Clean Technology, Ltd. [Member]
Business Acquisition [Line Items]
Percentage of value used for fair value of non-controlling interest estimates	100.00%
Quantum Global Technologies, LLC [Member]
Business Acquisition [Line Items]
Percentage of outstanding shares purchased	35.00%
Noncontrolling interest, ownership percentage by parent	86.00%
Quantum Global Technologies, LLC [Member] \| Cinos Co., Ltd [Member]
Business Acquisition [Line Items]
Percentage of outstanding shares purchased	51.00%
Cincos Co., Ltd [Member] \| Cinos Xian Clean Technology, Ltd [Member]
Business Acquisition [Line Items]
Noncontrolling interest, ownership percentage by parent	60.00%
Cinos Co., Ltd [Member]
Business Acquisition [Line Items]
Noncontrolling interest, ownership percentage by parent		86.00%
Percentage of non-controlling interest	14.00%
China Joint Venture [Member]
Business Acquisition [Line Items]
Percentage of non-controlling interest	40.00%