Income Taxes (Schedule of Reconciliation of Income Taxes at Statutory Rate and Tax Provision) (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2021	Dec. 25, 2020	Dec. 27, 2019
Income Taxes [Line Items]
Income tax expense (benefit), intercompany financing and legal entity reorganization		$ (59.9)	$ 384.2	$ (606.1)
Benefit for income taxes at domestic statutory income tax rate (1)	[1]	(103.7)	(120.1)	(302.4)
Adjustments to reconcile to income tax provision:
Rate difference between non-U.S. and U.S. jurisdictions	[2]	224.9	315.3	206.3
Valuation allowances (4)	[3]	189.7	618.2	61.7
Adjustments to accrued income tax liabilities and uncertain tax positions	[4]	(9.7)	16.7	(18.7)
Credits, principally research		(4.7)	(11.2)	(13.5)
Permanently nondeductible and nontaxable items	[3]	9.8	2.8	98.1
Effective Income Tax Rate Reconciliation, Disposition of Business, Amount	[5]	0.0	0.0	9.6
Income tax benefit, tax cut and jobs act	[6]	0.0	(281.5)	0.0
Other		0.3	0.1	0.0
Income tax benefit, Legal Reorganization		0.0	82.0	(212.8)
Effective Income Tax Rate Reconciliation, Separation Costs		0.0	8.4	0.0
Effective Income Tax Rate Reconciliation, Reorganization Items, net		36.9	8.8	0.0
Provision for (benefit from) income taxes		(106.3)	8.9	$ (584.3)
Increase (Decrease) Tax Benefit, Jurisdiction Rate Difference		90.4	109.0
Increase (Decrease), Tax Expense (Benefit), Gain on Debt Repurchases			79.0
Increase (Decrease) Tax Expense (Benefit) due to opioid-related settlement charge		10.6	60.9
Increase (Decrease) Tax Benefit, Change in Country Referenced Rate			137.3
Increase (Decrease) Tax Benefit, Recurring Valuation Allowances			92.7
Valuation Allowance, Deferred Tax Asset, Increase (Decrease), Amount			204.9
Increase (Decrease) Tax Benefit, Medicaid Lawsuit		48.9	48.9
Increase (Decrease) Tax Expense (Benefit), Change in Operating Income		92.9	$ 30.0
Increase (Decrease) Tax Expense (Benefit) due to reorganization items, net		27.6
Increase (Decrease) Tax Expense (Benefit), Non-restructuring Impairment Charges		$ 13.2
UNITED KINGDOM
Income Taxes [Line Items]
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent				19.00%
IRELAND
Income Taxes [Line Items]
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent		12.50%	12.50%

[1] The statutory tax rate reflects the Irish statutory tax rate of 12.5% for fiscal 2021 and 2020, and the U.K. statutory tax rate of 19.0% for fiscal 2019.

[2] For fiscal 2019, includes the impact of certain recurring valuation allowances for domestic and international jurisdictions.

[3] For fiscal 2021, the permanently nondeductible and nontaxable items were primarily driven by the opioid-related litigation settlement loss that is partially permanently nondeductible. For fiscal 2020, an expense of $204.9 million was included as a discrete valuation allowance on certain net deferred tax assets that were no longer more likely than not realizable due to the Company's substantial doubt about its ability to continue as a going concern, further explained within Note 1. For fiscal 2019, the valuation allowances and permanently nondeductible and nontaxable item were primarily driven by the impact from the opioid-related litigation settlement charge that is partially permanently nondeductible, further explained within Note 19. Additional valuation allowance impacts are netted within other line items, as referenced in the associated footnotes to this table.

[4] Includes interest and penalties on accrued income tax liabilities and uncertain tax positions.

[5] The Company completed the sale of its wholly-owned subsidiary BioVectra in November 2019.

[6] Associated unrecognized tax benefit and valuation allowance are netted within this line