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
Employees’ taxes paid upon vesting of restricted stock units	(0.9)		(0.9)				(0.9)
Employees' taxes paid upon vesting of restricted stock units, 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. 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