Condensed Consolidated Statements of Stockholders' Equity - USD ($) $ in Millions	Total	Total Stockholders’ Equity of UCT	Common Stock	Additional Paid-in Capital	Treasury shares	Retained Earnings	Accumulated Other Comprehensive Income (Loss)	Noncontrolling Interests
Common stock, shares, beginning balance (in shares) at Dec. 29, 2023			44,600,000
Treasury stock, shares, beginning balance (in shares) at Dec. 29, 2023					1,500,000
Beginning balance at Dec. 29, 2023	$ 897.2	$ 838.9	$ 0.1	$ 541.5	$ (45.0)	$ 346.7	$ (4.4)	$ 58.3
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance under employee stock plans (in shares)			500,000
Issuance under employee stock plans	0.9	0.9		0.9
Employees' taxes paid upon vesting of restricted stock units (in shares)			(100,000)
Employees' taxes paid upon vesting of restricted stock units	(2.2)	(2.2)		(2.2)
Stock-based compensation expense	8.0	8.0		8.0
Repurchase of shares (in shares)			0
Dividend payments to a joint venture shareholder	(0.1)							(0.1)
Net income (loss)	14.2	9.7				9.7		4.5
Other comprehensive income (loss)	(6.3)	(3.0)					(3.0)	(3.3)
Common stock, shares, ending balance (in shares) at Jun. 28, 2024			45,000,000.0
Treasury stock, shares, ending balance (in shares) at Jun. 28, 2024					1,500,000
Ending balance at Jun. 28, 2024	911.7	852.3	$ 0.1	548.2	$ (45.0)	356.4	(7.4)	59.4
Common stock, shares, beginning balance (in shares) at Mar. 29, 2024			44,600,000
Treasury stock, shares, beginning balance (in shares) at Mar. 29, 2024					1,500,000
Beginning balance at Mar. 29, 2024	889.1	830.9	$ 0.1	545.0	$ (45.0)	337.3	(6.5)	58.2
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance under employee stock plans (in shares)			500,000
Issuance under employee stock plans	0.9	0.9		0.9
Employees' taxes paid upon vesting of restricted stock units (in shares)			(100,000)
Employees' taxes paid upon vesting of restricted stock units	(2.2)	(2.2)		(2.2)
Stock-based compensation expense	4.5	4.5		4.5
Repurchase of shares (in shares)			0
Dividend payments to a joint venture shareholder	(0.1)							(0.1)
Net income (loss)	21.5	19.1				19.1		2.4
Other comprehensive income (loss)	(2.0)	(0.9)					(0.9)	(1.1)
Common stock, shares, ending balance (in shares) at Jun. 28, 2024			45,000,000.0
Treasury stock, shares, ending balance (in shares) at Jun. 28, 2024					1,500,000
Ending balance at Jun. 28, 2024	$ 911.7	852.3	$ 0.1	548.2	$ (45.0)	356.4	(7.4)	59.4
Common stock, shares, beginning balance (in shares) at Dec. 27, 2024	45,100,000		45,100,000
Treasury stock, shares, beginning balance (in shares) at Dec. 27, 2024	1,500,000				1,500,000
Beginning balance at Dec. 27, 2024	$ 935.8	873.6	$ 0.1	558.4	$ (45.0)	370.4	(10.3)	62.2
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance under employee stock plans (in shares)			400,000
Issuance under employee stock plans	1.1	1.1		1.1
Employees' taxes paid upon vesting of restricted stock units	(0.7)	(0.7)		(0.7)
Stock-based compensation expense	10.0	10.0		10.0
Repurchase of shares (in shares)			(200,000)		200,000
Repurchase of shares	(3.4)	(3.4)			$ (3.4)
Dividend payments to a joint venture shareholder	(0.1)							(0.1)
Net income (loss)	(162.9)	(167.0)				(167.0)		4.1
Other comprehensive income (loss)	$ 10.0	5.8					5.8	4.2
Common stock, shares, ending balance (in shares) at Jun. 27, 2025	45,300,000		45,300,000
Treasury stock, shares, ending balance (in shares) at Jun. 27, 2025	1,700,000				1,700,000
Ending balance at Jun. 27, 2025	$ 789.8	719.4	$ 0.1	568.8	$ (48.4)	203.4	(4.5)	70.4
Common stock, shares, beginning balance (in shares) at Mar. 28, 2025			45,100,000
Treasury stock, shares, beginning balance (in shares) at Mar. 28, 2025					1,500,000
Beginning balance at Mar. 28, 2025	936.8	872.0	$ 0.1	561.3	$ (45.0)	365.4	(9.8)	64.8
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance under employee stock plans (in shares)			400,000
Issuance under employee stock plans	1.1	1.1		1.1
Employees' taxes paid upon vesting of restricted stock units	(0.7)	(0.7)		(0.7)
Stock-based compensation expense	7.1	7.1		7.1
Repurchase of shares (in shares)			(200,000)		200,000
Repurchase of shares	(3.4)	(3.4)			$ (3.4)
Dividend payments to a joint venture shareholder	(0.1)							(0.1)
Net income (loss)	(160.5)	(162.0)				(162.0)		1.5
Other comprehensive income (loss)	$ 9.5	5.3					5.3	4.2
Common stock, shares, ending balance (in shares) at Jun. 27, 2025	45,300,000		45,300,000
Treasury stock, shares, ending balance (in shares) at Jun. 27, 2025	1,700,000				1,700,000
Ending balance at Jun. 27, 2025	$ 789.8	$ 719.4	$ 0.1	$ 568.8	$ (48.4)	$ 203.4	$ (4.5)	$ 70.4