Condensed Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 29, 2019	Mar. 30, 2018
Income Statement [Abstract]
Revenues	$ 260,141	$ 314,842
Cost of goods sold	215,344	266,038
Gross profit	44,797	48,804
Operating expenses:
Research and development	3,431	3,029
Sales and marketing	5,395	3,805
General and administrative	27,791	15,062
Total operating expenses	36,617	21,896
Income from operations	8,180	26,908
Interest and other income (expense), net	(5,319)	326
Income before provision for income taxes	2,861	27,234
Income tax provision	1,507	2,493
Net income	1,354	24,741
Net income attributable to noncontrolling interest	749
Net income attributable to Ultra Clean Holdings, Inc.	$ 605	$ 24,741
Net income per share attributable to Ultra Clean Holdings, Inc. common stockholders:
Basic	$ 0.02	$ 0.67
Diluted	$ 0.02	$ 0.66
Shares used in computing net income per share:
Basic	39,122	36,723
Diluted	39,448	37,491