Income Taxes (Narrative) (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 27, 2019	Dec. 28, 2018	Dec. 29, 2017	Sep. 26, 2014	Nov. 04, 2019
Income Tax Contingency [Line Items]
Document Period End Date		Dec. 27, 2019
Effective Income Tax Rate Reconciliation, Foreign Income Tax Rate Differential, Amount	[1]	$ 206.3	$ 235.7	$ 219.9
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent		19.00%	19.00%	19.00%
Increase (Decrease) Tax Expense (Benefit), Change in Operating Income		$ 45.8	$ 4.7
Current Income Tax Expense (Benefit)		21.8	112.8	$ 38.1
Increase (Decrease) Tax Benefit, Jurisdiction Rate Difference		(29.4)	15.8
Deferred Tax Liabilities, Net			303.8
Income Taxes Paid, Net		30.7	12.4	73.4
Deferred Tax Liabilities, Intangible Assets		139.4	264.7
Deferred Tax Assets, Other		200.4	189.5
Tax loss and credit carryforwards		2,263.4	1,987.8
Operating Loss Carryforwards		782.0
Decrease in Unrecognized Tax Benefits is Reasonably Possible		99.5
Decrease in Interest and Penalties is Reasonably Possible		21.7
Unrecognized Tax Benefits, Interest on Income Taxes Accrued		32.9	37.1	7.1
Unrecognized Tax Benefits that Would Impact Effective Tax Rate		395.9	275.8	180.8
Unrecognized Tax Benefits, Interest on Income Taxes Expense		(14.4)	(30.0)	0.0
Unrecognized Tax Benefits, Interest on Income Taxes Release		18.6
Tax Credit Carryforward, Amount		64.3
Increase (Decrease) Deferred Tax Liability Resulting from Installment Note Payments		(69.0)
Increase (Decrease), Deferred Tax Liability Due to Amortization of Intangible Assets		(37.8)
Increase (Decrease) in Deferred Income Taxes		50.2
Tax Credit Carryforwards, Not Subject to Expiration		2.6
Increase (Decrease) Tax Expense (Benefit) Due to Divestiture		(20.2)	22.2
Increase (Decrease), Tax Expense (Benefit), Gain on Debt Repurchases		76.7
Increase (Decrease) Tax Expense (Benefit) due to opioid-related settlement charge		60.9
Increase (Decrease) Tax Expense (Benefit) Due to U.S. Tax Reform			80.2
Unrecognized Tax Benefits, Decrease Resulting from Acquisition			11.8
Increase (Decrease) Tax Benefit, Non-Restructuring Impairment Charges		101.0	(90.3)
Increase (Decrease) in Deferred Tax Liabilities, Opioid-related litigation settlement		211.9
Excess in Book over Tax Basis, Foreign Subsidiaries		17.0
Deferred Tax Liabilities, Undistributed Foreign Earnings		7.6
Deferred Income Tax Expense (Benefit)		(606.1)	(542.9)	(1,747.7)
Deferred Tax Liabilities Installment Sales		0.0	227.5
BioVectra Inc [Member]
Income Tax Contingency [Line Items]
Increase (Decrease) Deferred Tax Liability Resulting from Divestiture		3.1
Deferred Tax Liabilities, Property, Plant and Equipment						$ 2.7
Deferred Tax Liabilities, Intangible Assets						2.2
Deferred Tax Assets, Other						1.3
Tax loss and credit carryforwards						$ 0.5
Non-U.K.
Income Tax Contingency [Line Items]
Tax Credit Carryforward Utilization				5.6
Operating Loss Carry back				27.2
Operating Loss Carryforwards		0.9	13.7	57.2
Deferred Tax Assets, Operating Loss Carryforwards		2,084.0
Deferred Tax Assets, Operating Loss Carryforwards, Not Subject to Expiration		1,378.2
Deferred Tax Assets, Operating Loss Carryforwards, Subject to Expiration		705.8
U.K.
Income Tax Contingency [Line Items]
Operating Loss Carryforwards		1.2	$ 8.5	$ 14.3
Deferred Tax Assets, Operating Loss Carryforwards, Subject to Expiration		115.1
Intercompany Financing and Legal Entity Ownership Reorganization [Member]
Income Tax Contingency [Line Items]
Current Income Tax Expense (Benefit)		26.2
Increase (Decrease) Deferred Tax Liability Resulting From Legal Reorganization		239.0
Increase (Decrease) in Deferred Tax Liabilities, Other		29.7
Increase (Decrease) Deferred Tax Asset, Tax Loss and Credit Carryforwards		12.5
Deferred Income Tax Expense (Benefit)		(239.0)
Increase (decrease), deferred tax assets, excess interest carryforwrds		28.7
Discontinued Operations [Member]
Income Tax Contingency [Line Items]
Unrecognized Tax Benefits that Would Impact Effective Tax Rate		$ 20.0
Cadence Pharmaceuticals, Inc. [Member] | Internal Revenue Service (IRS) [Member]
Income Tax Contingency [Line Items]
Proposed Adjustment to Taxable Income					$ 871.0

[1] Includes the impact of certain recurring valuation allowances for U.K. and non-U.K. jurisdictions.