Condensed Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 28, 2018	Sep. 29, 2017	Sep. 28, 2018	Sep. 29, 2017
Statement of Comprehensive Income [Abstract]
Net income (loss) including noncontrolling interests	$ (6,440)	$ 19,716	$ 37,261	$ 54,236
Other comprehensive income (loss):
Change in cumulative translation adjustment	(193)	312	(656)	1,001
Cash flow hedges:
Change in fair value of derivatives	39	333	(24)	1,026
Adjustment for net gain (loss) realized and included in net income	(337)	(100)	(1,247)	(93)
Total change in unrealized gain (loss) on derivative instruments	(298)	233	(1,271)	933
Total Other comprehensive income (loss), net of tax	(491)	545	(1,927)	1,934
Other comprehensive income (loss), net of tax, attributable to noncontrolling interest	(37)		(37)
Comprehensive income (loss) attributable to Ultra Clean Holdings, Inc.	$ (6,894)	$ 20,261	$ 35,371	$ 56,170