Business Segments (Details8) - USD ($) $ in Millions	12 Months Ended
	Dec. 29, 2024	Dec. 31, 2023	Jan. 01, 2023
Segment Reporting Reconciling Item For Operating Profit Loss From Segment To Consolidated [Line Items]
Segment EBITDA	$ 782.3	$ 710.2	$ 678.7
Corporate expenses	(64.0)	(62.3)	(60.3)
Closed operations and other income (expenses)	10.8	(13.3)	(5.6)
Depreciation and amortization	(151.5)	(146.1)	(142.9)
Interest expense, net	(108.2)	(92.8)	(87.4)
Restructuring and other credits (charges)	$ (22.1)	$ (31.4)	$ (23.7)
Defined Benefit Plan Net Periodic Benefit Cost Credit Excluding Service Cost Statement Of Income Or Comprehensive Income Extensible Enumeration, Not Disclosed Flag	Retirement benefit settlement loss (See Note 14)	Retirement benefit settlement loss (See Note 14)	Retirement benefit settlement loss (See Note 14)
Defined Benefit Plan Net Periodic Benefit Cost Credit Immediate Recognition Of Actuarial Gain Loss Statement Of Income Or Comprehensive Income Extensible List Not Disclosed Flag	Pension remeasurement gain (loss) (See Note 14)	Pension remeasurement gain (loss) (See Note 14)	Pension remeasurement gain (loss) (See Note 14)
Retirement benefit settlement gain (loss)	$ 0.0	$ (41.7)	$ 0.0
Pension remeasurement gain (loss)	(14.1)	(26.8)	100.3
Joint venture restructuring credit (charge)	0.0	0.0	0.9
Gain (loss) on asset sales and sale of business, net	52.9	(0.6)	(105.4)
Income (loss) before income taxes	486.1	295.2	354.6
Operating Segments
Segment Reporting Reconciling Item For Operating Profit Loss From Segment To Consolidated [Line Items]
Depreciation and amortization	(151.5)	(146.1)	(142.9)
Operating Segments | HPMC
Segment Reporting Reconciling Item For Operating Profit Loss From Segment To Consolidated [Line Items]
Allocated corporate overhead	65.7	60.1	37.9
Other segment items	1,999.1	1,808.3	1,474.4
Segment EBITDA	461.4	433.6	303.4
Depreciation and amortization	(71.6)	(71.1)	(68.3)
Operating Segments | AA&S
Segment Reporting Reconciling Item For Operating Profit Loss From Segment To Consolidated [Line Items]
Allocated corporate overhead	65.4	58.6	34.2
Other segment items	1,972.4	2,001.7	2,024.2
Segment EBITDA	320.9	276.6	375.3
Depreciation and amortization	$ (73.2)	$ (67.9)	$ (67.4)