Net Income Per Share - Basic and Diluted Net Income Per Share (Detail) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended
	Mar. 26, 2021	Mar. 27, 2020
Numerator:
Net income attributable to UCT	$ 25.0	$ 9.4
Shares used in computation — basic:
Weighted average common shares outstanding	40.6	39.8
Shares used in computation — diluted:
Weighted average common shares outstanding	40.6	39.8
Dilutive effect of common shares outstanding subject to repurchase	1.0	0.9
Shares used in computing diluted net income per share	41.6	40.7
Net income per share attributable to UCT — basic	$ 0.62	$ 0.24
Net income per share attributable to UCT — diluted	$ 0.60	$ 0.23