Condensed Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 28, 2019	Jun. 29, 2018	Jun. 28, 2019	Jun. 29, 2018
Income Statement [Abstract]
Revenues	$ 265,367	$ 290,213	$ 525,508	$ 605,055
Cost of goods sold	217,198	244,148	432,542	510,186
Gross profit	48,169	46,065	92,966	94,869
Operating expenses:
Research and development	3,921	2,915	7,352	5,944
Sales and marketing	5,366	3,630	10,761	7,435
General and administrative	29,911	16,856	57,702	31,918
Total operating expenses	39,198	23,401	75,815	45,297
Income from operations	8,971	22,664	17,151	49,572
Interest and other income (expense), net	(6,390)	(809)	(11,709)	(483)
Income before income tax provision	2,581	21,855	5,442	49,089
Income tax provision	2,835	2,895	4,342	5,388
Net income (loss)	(254)	18,960	1,100	43,701
Net income (loss) attributable to noncontrolling interest	(52)		697
Net income (loss) attributable to Ultra Clean Holdings, Inc.	$ (202)	$ 18,960	$ 403	$ 43,701
Net income (loss) per share attributable to Ultra Clean Holdings, Inc. common stockholders:
Basic	$ (0.01)	$ 0.49	$ 0.01	$ 1.16
Diluted	$ (0.01)	$ 0.48	$ 0.01	$ 1.14
Shares used in computing net income (loss) per share:
Basic	39,399	38,802	39,261	37,763
Diluted	39,399	39,297	39,556	38,418