Document and Entity Information - shares	6 Months Ended
	Jun. 26, 2020	Jul. 24, 2020
Cover [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Jun. 26, 2020
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	Q2
Trading Symbol	UCTT
Entity Registrant Name	Ultra Clean Holdings, Inc.
Entity Central Index Key	0001275014
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Current Fiscal Year End Date	--12-27
Entity Filer Category	Accelerated Filer
Entity Shell Company	false
Entity Small Business	false
Entity Emerging Growth Company	false
Document Quarterly Report	true
Document Transition Report	false
Title of 12(b) Security	Common stock, par value $0.001 per share
Entity Incorporation, State or Country Code	DE
Security Exchange Name	NASDAQ
Entity File Number	000-50646
Entity Tax Identification Number	61-1430858
Entity Address, Address Line One	26462 Corporate Avenue
Entity Address, City or Town	Hayward
Entity Address, State or Province	CA
Entity Address, Postal Zip Code	94545
City Area Code	510
Local Phone Number	576-4400
Entity Common Stock, Shares Outstanding		40,400,000