Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Millions	3 Months Ended		6 Months Ended		9 Months Ended		12 Months Ended
	Sep. 26, 2024	Sep. 28, 2023	Jun. 27, 2024	Jun. 29, 2023	Sep. 26, 2024	Sep. 28, 2023	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Operating activities
Net loss	$ (476.9)	$ (204.1)	$ (1,032.0)	$ (487.5)	$ (1,508.9)	$ (691.6)	$ 616.2	$ 545.7	$ 540.8
Adjustments to reconcile net loss to net cash used in operating activities
Depreciation and amortization expense					232.9	236.9
Amortization of deferred financing fees					8.9	5.2
Accretion of customer supply agreement					1.8	1.8
Employee Benefit and Share-based Payment Arrangement, Noncash					30.8	29.3
Loss on Derivative Instruments, Pretax					(2.9)	(1.7)
Loss (gain) from foreign currency transactions					27.1	(4.0)
Gain (Loss) on Disposition of Property Plant Equipment, Excluding Oil and Gas Property and Timber Property					(1.3)	(0.9)
Deferred taxes					6.9	(3.8)
Increase (Decrease) in Obligation, Pension and Other Postretirement Benefits					(8.9)	61.8
Grant liability amortization					(0.9)	(0.9)
Unrealized Gain (Loss) on Investments					(0.2)	0.2
Increase (Decrease) in Forward Provision					524.9	(50.7)
Changes in assets and liabilities
Accounts receivable, net					31.8	(127.0)
Inventory, net					(245.8)	(227.0)
Accounts payable and accrued liabilities					65.4	222.2
Profit sharing/deferred compensation					37.6	(22.5)
Advance payments					5.2	87.4
Income taxes receivable/payable					5.5	1.1
Pension plans employer contributions					(0.7)	67.4
Other					7.9	19.7
Net cash used in operating activities					(1,257.5)	(339.5)	225.8	394.6	$ 63.2
Investing activities
Purchase of property, plant, and equipment					(106.8)	(76.5)
Payments for (Proceeds from) Other Investing Activities					0.1	0.0
Net cash used in investing activities					(106.7)	(76.5)
Financing activities
Proceeds from Lines of Credit					0.0	1.6
Proceeds from Issuance of Senior Long-term Debt					359.2	12.7
Principal payments of debt					(46.5)	(47.2)
Repayments of Debt					(3.0)	(3.0)
Payment, Tax Withholding, Share-based Payment Arrangement	(0.3)	(0.3)	(5.1)	(5.8)	(5.4)	(6.1)
Proceeds from Stock Plans					3.8	2.6
Debt issuance and financing costs					(10.8)	(0.5)
Proceeds from Other Debt					509.4	180.0	180.0
Proceeds from (Payments for) Other Financing Activities					(1.9)	0.0
Net cash provided by financing activities					764.8	134.1
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Period Increase (Decrease), Including Exchange Rate Effect					(599.1)	(281.9)
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Beginning Balance			$ 845.9	$ 678.4	845.9	678.4	678.4
Cash, cash equivalents, and restricted cash, end of period	246.8	396.5			246.8	396.5	845.9	678.4
Cash and Cash Equivalents, at Carrying Value, Ending Balance	217.6	374.1			217.6	374.1	823.5	658.6
Reconciliation of Cash, Cash Equivalents, and Restricted Cash [Abstract]
Restricted Cash, Current	0.0	0.2			0.0	0.2	0.1	0.2
Restricted Cash, Noncurrent	29.2	22.2			29.2	22.2	22.3	$ 19.6
Increase (Decrease) in Income Taxes Payable					5.5	1.1
Increase (Decrease) in Contract with Customer, Liability					88.4	(3.9)
Defined Benefit Plan, Plan Assets, Increase (Decrease) for Assets Transferred to (from) Plan					(2.2)	178.0
Proceeds from Issuance of Senior Long-term Debt					359.2	12.7
Proceeds from (Payments for) Other Financing Activities					(1.9)	0.0
Proceeds from Other Debt					509.4	180.0	$ 180.0
Increase (Decrease) in Contract with Customer, Asset					557.3	114.5
Effect of Exchange Rate on Cash, Cash Equivalents, Restricted Cash, and Restricted Cash Equivalents, Continuing Operations					0.3	0.0
Gain (Loss) on Contract Termination					(1.2)	(1.4)
Asset Impairment Charges					0.2	0.0
Business Combination, Contingent Consideration Arrangements, Change in Amount of Contingent Consideration, Liability		0.0			0.0	(2.4)
Increase (Decrease) in Deferred Liabilities					(0.7)	67.4
Proceeds from Lines of Credit					0.0	1.6
Increase (Decrease) in Customer Advances					5.2	87.4
Asset Acquisition, Consideration Transferred					0.0	(6.0)
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	$ (476.6)	$ (203.9)			(1,508.3)	(691.6)
Gain (Loss) on Sale of Other Loans and Leases					(5.7)	0.0
Repayments of Other Debt					$ (40.0)	$ 0.0