Acquisitions and License Agreements (Schedule of Fair Value of Identifiable Assets Acquired and Liabilities Assumed) (Details) - USD ($) $ in Millions						3 Months Ended		12 Months Ended
		Feb. 13, 2018	Dec. 11, 2017		Sep. 25, 2017	Dec. 27, 2019	Jun. 28, 2019	Dec. 27, 2019	Dec. 28, 2018	Dec. 29, 2017
Business Combination, Recognized Identifiable Assets Acquired, Goodwill, and Liabilities Assumed, Less Noncontrolling Interest [Abstract]
Non-restructuring impairment charges								$ 388.0	$ 3,893.1	$ 63.7
Sucampo [Member]
Business Combination, Recognized Identifiable Assets Acquired, Goodwill, and Liabilities Assumed, Less Noncontrolling Interest [Abstract]
Cash		$ 149.6
Receivables		35.7
Inventory		153.2
Intangible assets		919.5
Goodwill, Acquired During Period	[1]	248.6
Other assets, current and non-current		25.8
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Assets		1,532.4
Current liabilities		109.4
Other liabilities (non-current)		33.3
Deferred tax liabilities, net (non-current)		175.8
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Noncurrent Liabilities		0.0
Contingent consideration (non-current)		0.0
Total Debt		366.3
Total liabilities assumed		684.8
Total consideration		847.6
Ocera [Member]
Business Combination, Recognized Identifiable Assets Acquired, Goodwill, and Liabilities Assumed, Less Noncontrolling Interest [Abstract]
Cash	[2],[3]		$ 1.0
Receivables	[3]		0.0
Inventory	[3]		0.0
Goodwill, Acquired During Period	[1],[3]		18.0
Other assets, current and non-current	[3]		0.4
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Assets	[3]		83.9
Current liabilities	[3]		12.0
Other liabilities (non-current)	[3]		0.0
Deferred tax liabilities, net (non-current)	[3]		16.7
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Non-Current Contingent Consideration	[3]		12.8
Contingent consideration (non-current)	[2]		22.0
Total Debt	[3]		0.0
Total liabilities assumed	[3]		41.5
Total consideration			64.4	[2]					1.9	$ 40.5
InfaCare [Member]
Business Combination, Recognized Identifiable Assets Acquired, Goodwill, and Liabilities Assumed, Less Noncontrolling Interest [Abstract]
Cash	[4]				$ 1.3
Receivables	[4]				0.0
Inventory	[4]				0.0
Goodwill, Acquired During Period	[1],[4]				11.4
Other assets, current and non-current	[4]				0.1
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Assets	[4]				126.3
Current liabilities	[4]				14.5
Other liabilities (non-current)	[4]				0.0
Deferred tax liabilities, net (non-current)	[4]				8.7
Contingent consideration (non-current)	[4]				35.0
Total Debt	[4]				30.0
Total liabilities assumed	[4]				88.2
Total consideration					73.1
VTS-270 [Member] | Sucampo [Member]
Business Combination, Recognized Identifiable Assets Acquired, Goodwill, and Liabilities Assumed, Less Noncontrolling Interest [Abstract]
Indefinite lived intangible assets acquired		$ 274.5
Non-restructuring impairment charges						$ 274.5
MNK-6105 [Member] | Ocera [Member]
Business Combination, Recognized Identifiable Assets Acquired, Goodwill, and Liabilities Assumed, Less Noncontrolling Interest [Abstract]
Indefinite lived intangible assets acquired	[3]		$ 64.5
Stannsoporfin [Member] | InfaCare [Member]
Business Combination, Recognized Identifiable Assets Acquired, Goodwill, and Liabilities Assumed, Less Noncontrolling Interest [Abstract]
Non-restructuring impairment charges							$ 113.5
Stannsoporfin [Member] | InfaCare [Member]
Business Combination, Recognized Identifiable Assets Acquired, Goodwill, and Liabilities Assumed, Less Noncontrolling Interest [Abstract]
Indefinite lived intangible assets acquired	[4]				$ 113.5
Fair Value, Measurements, Recurring
Business Combination, Recognized Identifiable Assets Acquired, Goodwill, and Liabilities Assumed, Less Noncontrolling Interest [Abstract]
Contingent consideration (non-current)						69.3		69.3	151.4
Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 3
Business Combination, Recognized Identifiable Assets Acquired, Goodwill, and Liabilities Assumed, Less Noncontrolling Interest [Abstract]
Contingent consideration (non-current)						69.3		69.3	151.4
Fair Value, Measurements, Recurring | MNK-6105 [Member] | Fair Value, Inputs, Level 3 | Ocera [Member]
Business Combination, Recognized Identifiable Assets Acquired, Goodwill, and Liabilities Assumed, Less Noncontrolling Interest [Abstract]
Contingent consideration (non-current)						$ 15.8		15.8	$ 21.5
Fair Value, Measurements, Recurring | Stannsoporfin [Member] | Fair Value, Inputs, Level 3 | InfaCare [Member]
Business Combination, Recognized Identifiable Assets Acquired, Goodwill, and Liabilities Assumed, Less Noncontrolling Interest [Abstract]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Period Increase (Decrease)								$ (35.0)

[1] Refer to Note 13 for further information relating to the full goodwill impairment recorded in fiscal 2018.

[2] $1.9 million of the total consideration, net of cash was paid in fiscal 2018, subsequent to the Company's December 11, 2017 acquisition date.

[3] Of the $42.4 million net assets acquired for Ocera, $40.5 million and $1.9 million was paid in fiscal 2017 and 2018, respectively.

[4] During fiscal 2019, the Company recognized a full impairment of the IPR&D asset related to stannsoporfin of $113.5 million. During fiscal 2018, the Company reduced the contingent consideration liability related to this acquisition to zero through the recognition of a $35.0 million fair value adjustment. Refer to Note 13 and 21 for further information.