Income Taxes (Narrative) (Details) - USD ($) $ in Millions		1 Months Ended	6 Months Ended		11 Months Ended	12 Months Ended
	Jun. 16, 2022	Dec. 29, 2023	Dec. 30, 2022	Jun. 16, 2022	Nov. 14, 2023	Dec. 27, 2024	Dec. 29, 2023	Dec. 30, 2022	Dec. 31, 2021
Income Tax Contingency [Line Items]
Effective Income Tax Rate Reconciliation, Foreign Income Tax Rate Differential, Amount		$ 2.2	$ 4.7	$ (226.5)	$ (56.6)	$ (35.1)
Increase (Decrease) Tax Expense (Benefit), Change in Operating Income		(1.4)	(30.2)	(12.8)	(35.0)	(28.3)
Current Income Tax Expense (Benefit)		(1.4)	(27.1)	(23.9)	41.3	(20.8)
Income Taxes Paid, Net		(0.3)	(3.0)	(3.0)	128.0	(25.7)
Deferred Tax Assets, Other		326.4				306.9	$ 326.4
Tax loss and credit carryforward		3,600.7				3,529.8	3,600.7
Unrecognized Tax Benefits, Interest on Income Taxes Accrued		4.2				5.9	4.2
Unrecognized Tax Benefits that Would Impact Effective Tax Rate	$ 24.8	30.1	24.8	24.8	30.1	30.9	30.1	$ 24.8
Unrecognized Tax Benefits, Interest on Income Taxes Expense		0.0	(0.6)	(16.7)	(1.4)	(1.7)
Tax Credit Carryforward, Amount						0.4
Excess in Book over Tax Basis, Foreign Subsidiaries						9.7
Deferred Income Tax Expense (Benefit)		(6.6)	(24.9)	(473.4)	(319.1)	158.7
Income tax expense (benefit)		(8.0)	(52.0)	(497.3)	(277.8)	137.9
Deferred Tax Assets, Capital Loss Carryforwards		983.5				188.1	983.5
Increase (Decrease) Tax Expense (Benefit) due to reorganization items, net					48.9
Increase (Decrease) Tax Expense (Benefit), Non-restructuring Impairment Charges					11.6
Deferred Tax Liabilities, Gross		(97.3)				(90.6)	(97.3)
Increase (Decrease) Tax (Benefit), Inventory Step-Up Amortization		3.7	19.7
Increase (Decrease) Tax Expense (Benefit), Settlement liabilities accretion expense		0.2	8.9
Increase (Decrease) Tax Expense (Benefit), Debt accretion expense			6.3
Increase (Decrease) Tax Benefit, Fresh-Start adjustments				128.9
Increase (Decrease) Tax Expense (Benefit), Gain on LSTC adjustments				103.4
Increase (Decrease) Tax Expense (Benefit), Professional & Lender Fees				18.6
Increase (Decrease) Tax Expense Benefit, Fresh-Start Accounting Revaluation of DTA	1,202.0				242.8
Increase (Decrease) Income Tax Expense (Benefit), Release of UTP	285.3
Increase (Decrease) Tax Expense (Benefit), NOL carryforward reduction	1,209.8
Increase (Decrease) Tax Expense (Benefit), Permanently nondeductible impacts	191.9				139.1
Increase (Decrease) Tax Expense (Benefit), Prepaid income taxes	54.0
Unrecognized Tax Benefits, Period Increase (Decrease)				306.1
Deferred income taxes		801.0				651.8	801.0
Deferred income taxes		0.0				(0.1)	0.0
Deferred income tax asset (liability), net		(801.0)				(651.7)	(801.0)
Increase (Decrease) Deferred Tax Assets, Other						76.1
Permanently nondeductible and nontaxable items		(0.2)	3.1	(1.7)	3.2	12.6
Increase (Decrease) Tax Expense (Benefit), Therakos Divestiture						10.4
Net Deferred Tax Assets, before Valuation Allowances		5,384.8				4,409.0	5,384.8
Valuation allowances	(5,129.7)	(4,583.8)	(4,992.9)	(5,129.7)	(4,584.8)	(3,757.3)	$ (4,583.8)	$ (4,992.9)	$ (6,344.2)
Increase (Decrease) Deferred Tax Assets, Capital Tax Loss Carryforwards						795.5
Increase (Decrease) Deferred Tax Assets, Therakos Divestiture						104.2
Income Tax Expense (Benefit), Continuing Operations, Discontinued Operations		0.0	$ 0.0	$ 0.0	0.0	0.0
Increase (Decrease) Income Tax Expense (Benefit), Fresh-Start Accounting						3.6
IRELAND
Income Tax Contingency [Line Items]
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent			12.50%	12.50%			12.50%	12.50%
Non-U.K.
Income Tax Contingency [Line Items]
Operating Loss Carryforwards	0.1	6.9	$ 61.0	$ 0.1	259.6	55.1	$ 6.9	$ 61.0
Deferred Tax Assets, Operating Loss Carryforwards						3,481.3
Deferred Tax Assets, Operating Loss Carryforwards, Not Subject to Expiration						1,303.3
Deferred Tax Assets, Operating Loss Carryforwards, Subject to Expiration						2,178.0
Deferred Tax Assets, Capital Loss Carryforwards						15.1
Ireland
Income Tax Contingency [Line Items]
Operating Loss Carryforwards	4.1	$ 0.0	$ 7.9	$ 4.1	2.9	0.0	$ 0.0	$ 7.9
Deferred Tax Assets, Operating Loss Carryforwards, Not Subject to Expiration						48.1
Deferred Tax Assets, Capital Loss Carryforwards						173.0
CARES Act
Income Tax Contingency [Line Items]
Proceeds from Income Tax Refunds					141.6
Chapter 11 Emergence
Income Tax Contingency [Line Items]
Income tax expense (benefit)	$ 31.6				$ 103.7
Nondeductible Employee Compensation
Income Tax Contingency [Line Items]
Permanently nondeductible and nontaxable items						$ 6.1