Condensed Consolidated Statements of Comprehensive Income (loss) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 25, 2020	Sep. 27, 2019	Sep. 25, 2020	Sep. 27, 2019
Statement Of Income And Comprehensive Income [Abstract]
Net income	$ 25.1	$ 0.9	$ 57.7	$ 2.0
Other comprehensive income (loss):
Change in cumulative translation adjustment	2.0	(1.6)		(3.8)
Change in fair value of derivatives		(0.1)
Total other comprehensive income (loss)	2.0	(1.7)		(3.8)
Other comprehensive income, attributable to noncontrolling interests	0.7	0.4	2.6	1.1
Comprehensive income (loss) attributable to UCT	$ 26.4	$ (1.2)	$ 55.1	$ (2.9)