Income Taxes (Narrative) (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2021	Dec. 25, 2020	Dec. 27, 2019
Income Tax Contingency [Line Items]
Effective Income Tax Rate Reconciliation, Foreign Income Tax Rate Differential, Amount	[1]	$ 224.9	$ 315.3	$ 206.3
Increase (Decrease) Tax Expense (Benefit), Change in Operating Income		92.9	30.0
Current Income Tax Expense (Benefit)		(46.4)	(375.3)	21.8
Increase (Decrease) Tax Benefit, Jurisdiction Rate Difference		(90.4)	(109.0)
Deferred income taxes		20.9	80.6
Income Taxes Paid, Net		160.0	(39.9)	(30.7)
Deferred Tax Liabilities, Intangible Assets		108.5	191.2
Deferred Tax Assets, Other		292.2	294.9
Tax loss and credit carryforward		4,147.5	4,026.0
Decrease in Unrecognized Tax Benefits is Reasonably Possible		139.2
Decrease in Interest and Penalties is Reasonably Possible		17.2
Unrecognized Tax Benefits, Interest on Income Taxes Accrued		18.9	16.7	32.9
Unrecognized Tax Benefits that Would Impact Effective Tax Rate		77.0	85.9	395.9
Unrecognized Tax Benefits, Interest on Income Taxes Expense		(6.4)	(16.2)	(4.2)
Unrecognized Tax Benefits, Interest on Income Taxes Release		4.2
Tax Credit Carryforward, Amount		83.9
Tax Credit Carryforwards, Not Subject to Expiration		2.3
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
Excess in Book over Tax Basis, Foreign Subsidiaries		12.1
Deferred Income Tax Expense (Benefit)		(59.9)	384.2	(606.1)
(Benefit) expense from income taxes		(106.3)	8.9	$ (584.3)
Deferred Tax Assets, Capital Loss Carryforwards		1,605.0	1,600.1
Increase (Decrease) Tax Benefit, Medicaid Lawsuit		48.9	48.9
Increase (Decrease) Tax Expense (Benefit) due to reorganization items, net		27.6
Valuation Allowance Tax Expense		189.7	618.2
Increase (Decrease) Valuation Allowance Tax Expense		428.5
Increase (Decrease) Valuation Allowance Tax Expense (Benefit), Operational Activity		288.9
Increase (Decrease) Valuation Allowance Tax Expense (Benefit), deferred tax assets		204.9
Increase (Decrease) Valuation Allowance Tax Expense (Benefit), tax rate changes		65.3
Increase (Decrease) Tax Expense (Benefit), Non-restructuring Impairment Charges		13.2
Deferred Tax Liabilities, Gross		$ (175.6)	$ (310.8)
UNITED KINGDOM
Income Tax Contingency [Line Items]
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent				19.00%
IRELAND
Income Tax Contingency [Line Items]
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent		12.50%	12.50%
Nuclear Imaging
Income Tax Contingency [Line Items]
(Benefit) expense from income taxes		$ 5.1	$ 18.1
Non-U.K.
Income Tax Contingency [Line Items]
Operating Loss Carryforwards		1.2	33.4	$ 0.9
Deferred Tax Assets, Operating Loss Carryforwards		4,024.0
Deferred Tax Assets, Operating Loss Carryforwards, Not Subject to Expiration		1,851.3
Deferred Tax Assets, Operating Loss Carryforwards, Subject to Expiration		2,172.7
Deferred Tax Assets, Capital Loss Carryforwards		184.7
Ireland
Income Tax Contingency [Line Items]
Operating Loss Carryforwards		2.2	0.2	$ 1.2
Deferred Tax Assets, Operating Loss Carryforwards, Subject to Expiration		39.5
Deferred Tax Assets, Capital Loss Carryforwards		969.5
Other Noncurrent Liabilities
Income Tax Contingency [Line Items]
Deferred Tax Liabilities, Gross		(20.9)	$ (80.6)
CARES Act
Income Tax Contingency [Line Items]
Proceeds from Income Tax Refunds		178.8
Operational activity
Income Tax Contingency [Line Items]
Income Taxes Paid, Net		(18.8)
Discontinued Operations [Member]
Income Tax Contingency [Line Items]
Unrecognized Tax Benefits that Would Impact Effective Tax Rate		$ 20.0

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