Condensed Consolidated Statements of Stockholders' Equity - USD ($) $ in Millions	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Treasury Shares [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Total stock holder's Equity of UCT [Member]	Noncontrolling Interests [Member]
Beginning balance at Dec. 28, 2018	$ 451.0	$ 0.1	$ 290.4	$ (3.3)	$ 149.7	$ (0.6)	$ 436.3	$ 14.7
Beginning balance, Shares at Dec. 28, 2018		39.1		0.6
Issuance under employee stock plans, Shares		0.3
Stock-based compensation expense	2.9		2.9				2.9
Taxes paid related to net share settlement of equity awards	(0.9)		(0.9)				(0.9)
Taxes paid related to net share settlement of equity awards, Shares		(0.1)
Net income	1.4				0.6		0.6	0.8
Other comprehensive loss	(0.9)					(0.9)	(0.9)
Ending balance at Mar. 29, 2019	453.5	$ 0.1	292.4	$ (3.3)	150.3	(1.5)	438.0	15.5
Ending balance, Shares at Mar. 29, 2019		39.3		0.6
Beginning balance at Dec. 28, 2018	451.0	$ 0.1	290.4	$ (3.3)	149.7	(0.6)	436.3	14.7
Beginning balance, Shares at Dec. 28, 2018		39.1		0.6
Net income	1.1
Ending balance at Jun. 28, 2019	454.5	$ 0.1	294.9	$ (3.3)	150.1	(2.7)	439.1	15.4
Ending balance, Shares at Jun. 28, 2019		39.5		0.6
Beginning balance at Mar. 29, 2019	453.5	$ 0.1	292.4	$ (3.3)	150.3	(1.5)	438.0	15.5
Beginning balance, Shares at Mar. 29, 2019		39.3		0.6
Issuance under employee stock plans	0.1		0.1				0.1
Issuance under employee stock plans, Shares		0.3
Stock-based compensation expense	2.9		2.9				2.9
Taxes paid related to net share settlement of equity awards	(0.5)		(0.5)				(0.5)
Taxes paid related to net share settlement of equity awards, Shares		(0.1)
Net income	(0.3)				(0.2)		(0.2)	(0.1)
Other comprehensive loss	(1.2)					(1.2)	(1.2)
Ending balance at Jun. 28, 2019	454.5	$ 0.1	294.9	$ (3.3)	150.1	(2.7)	439.1	15.4
Ending balance, Shares at Jun. 28, 2019		39.5		0.6
Beginning balance at Dec. 27, 2019	452.5	$ 0.1	300.9	$ (3.3)	140.3	(1.3)	436.7	15.8
Beginning balance, Shares at Dec. 27, 2019		39.9		0.6
Stock-based compensation expense	3.1		3.1				3.1
Net income	10.5				9.4		9.4	1.1
Other comprehensive loss	(3.3)					(3.3)	(3.3)
Ending balance at Mar. 27, 2020	462.8	$ 0.1	304.0	$ (3.3)	149.7	(4.6)	445.9	16.9
Ending balance, Shares at Mar. 27, 2020		39.9		0.6
Beginning balance at Dec. 27, 2019	452.5	$ 0.1	300.9	$ (3.3)	140.3	(1.3)	436.7	15.8
Beginning balance, Shares at Dec. 27, 2019		39.9		0.6
Net income	32.6
Ending balance at Jun. 26, 2020	488.2	$ 0.1	306.0	$ (3.3)	171.0	(3.3)	470.5	17.7
Ending balance, Shares at Jun. 26, 2020		40.3		0.6
Beginning balance at Mar. 27, 2020	462.8	$ 0.1	304.0	$ (3.3)	149.7	(4.6)	445.9	16.9
Beginning balance, Shares at Mar. 27, 2020		39.9		0.6
Issuance under employee stock plans	0.3		0.3				0.3
Issuance under employee stock plans, Shares		0.5
Stock-based compensation expense	3.1		3.1				3.1
Taxes paid related to net share settlement of equity awards	(1.4)		(1.4)				(1.4)
Taxes paid related to net share settlement of equity awards, Shares		(0.1)
Net income	22.1				21.3		21.3	0.8
Other comprehensive loss	1.3					1.3	1.3
Ending balance at Jun. 26, 2020	$ 488.2	$ 0.1	$ 306.0	$ (3.3)	$ 171.0	$ (3.3)	$ 470.5	$ 17.7
Ending balance, Shares at Jun. 26, 2020		40.3		0.6