Net Income Per Share - Basic and Diluted Net Income Per Share (Detail) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 24, 2021	Sep. 25, 2020	Sep. 24, 2021	Sep. 25, 2020
Numerator:
Net income attributable to UCT	$ 31.9	$ 24.4	$ 74.0	$ 55.1
Shares used in computation — basic:
Weighted average common shares outstanding	44.8	40.4	42.8	40.1
Shares used in computation — diluted:
Weighted average common shares outstanding	44.8	40.4	42.8	40.1
Dilutive effect of common shares outstanding subject to repurchase	0.6	0.7	0.9	0.8
Shares used in computing diluted net income per share	45.4	41.1	43.7	40.9
Net income per share attributable to UCT — basic	$ 0.71	$ 0.60	$ 1.73	$ 1.37
Net income per share attributable to UCT — diluted	$ 0.70	$ 0.59	$ 1.69	$ 1.35