Financial Instruments and Fair Value Measurements (Narrative) (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 28, 2019	Dec. 28, 2018	Apr. 30, 2013
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Contingent Consideration, Liability, Current	$ 52.4
Contingent Consideration, Liability, Noncurrent	78.0
Senior Notes | 4.75% Senior Notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Stated interest rate			4.75%
Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Investments, Fair Value Disclosure	35.4	$ 33.1
Level 3 | Other Assets
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Cash surrender value of life insurance	66.6	66.4
Level 3 | Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Investments, Fair Value Disclosure	0.0	0.0
Level 3 | Recurring | Questcor Pharmaceuticals, Inc.
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Fair value of contingent liability	52.9	76.2
Level 3 | MNK-6105 [Member] | Recurring | Ocera [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Fair value of contingent consideration	$ 21.9	21.5
Level 2 | Debentures | 8.00% Debenture
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Stated interest rate	8.00%
Level 2 | Debentures | 9.50% Debenture
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Stated interest rate	9.50%
Level 2 | Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Investments, Fair Value Disclosure	$ 9.8	10.7
Level 1 | Senior Notes | 4.75% Senior Notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Stated interest rate	4.75%
Level 1 | Senior Notes | 5.75% Senior Notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Stated interest rate	5.75%
Level 1 | Senior Notes | 4.88% Senior Notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Stated interest rate	4.875%
Level 1 | Senior Notes | 5.50% Senior Notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Stated interest rate	5.50%
Level 1 | Unsecured Debt | 5.625% Senior Notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Stated interest rate	5.625%
Level 1 | Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Investments, Fair Value Disclosure	$ 25.6	22.4
Maximum | Synacthen | Questcor Pharmaceuticals, Inc.
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Milestone Payment	90.0
Nuclear Imaging | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Contingent Consideration, Equity Certificates	18.9	9.0
Indemnification Agreement | Mallinckrodt Baker | Level 1 | Other Assets
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Restricted Cash and Cash Equivalents	18.8	$ 18.6
Novartis 2015 and 2016 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Business Combination, Contingent Consideration, Annual Payments	$ 25.0