Organization and Significant Accounting Policies - Summary of Qualitative Information About Level 3 Fair Value Measurements (Details) - Significant Unobservable Inputs (Level 3) [Member] $ in Thousands	Jun. 28, 2019 USD ($)
Contingent Earn-out Liability [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Business Combination, Contingent Consideration, Liability, Valuation Technique [Extensible List]	uctt:ValuationTechniqueMonteCarloSimulationMember
Pension Obligation [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Business Combination, Contingent Consideration, Liability, Valuation Technique [Extensible List]	uctt:ValuationTechniqueProjectedUnitCreditMethodMember
Purchase Obligation [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Business Combination, Contingent Consideration, Liability, Valuation Technique [Extensible List]	us-gaap:ValuationTechniqueDiscountedCashFlowMember
Contingent Earn-out Liability [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Contingent consideration	$ 3,870
Contingent Earn-out Liability [Member] | Revenue Discount Rate [Member] | Minimum [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Range	0.100
Contingent Earn-out Liability [Member] | Internal Forecasts [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Range	0.075
Pension Obligation [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Contingent consideration	$ 3,293
Pension Obligation [Member] | Discount Rate [Member] | Minimum [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Range	0.0243
Pension Obligation [Member] | Discount Rate [Member] | Maximum [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Range	0.0274
Pension Obligation [Member] | Rate On Return [Member] | Minimum [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Range	0.0137
Pension Obligation [Member] | Rate On Return [Member] | Maximum [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Range	0.0178
Pension Obligation [Member] | Salary Increase Rate [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Range	0.0442
Purchase Obligation [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Contingent consideration	$ 8,500
Purchase Obligation [Member] | EBITDA Multiple [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Range	0.0621