Net Income Per Share - Basic and Diluted Net Income Per Share (Detail) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jul. 01, 2022	Jun. 30, 2023	Jul. 01, 2022
Numerator:
Net income (loss) attributable to UCT	$ (9.4)	$ (25.1)	$ (12.8)	$ 2.8
Shares used in computation — basic:
Weighted average common shares outstanding	44.7	45.2	44.8	45.1
Shares used in computation — diluted:
Weighted average common shares outstanding	44.7	45.2	44.8	45.1
Dilutive effect of common shares outstanding subject to repurchase	0	0	0	0.6
Shares used in computing diluted net income (loss) per share	44.7	45.2	44.8	45.7
Net income (loss) per share attributable to UCT - basic	$ (0.21)	$ (0.56)	$ (0.29)	$ 0.06
Net income (loss) per share attributable to UCT - diluted	$ (0.21)	$ (0.56)	$ (0.29)	$ 0.06