Goodwill and Intangible Assets (Schedule Of Intangible Assets) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 26, 2021	Mar. 27, 2020	Dec. 25, 2020
Goodwill and Intangible Assets Disclosure [Abstract]
Non-restructuring impairment charges	$ 64.5	$ 0.0
Schedule of Intangible Asset by Major Class [Line Items]
Amortizable intangible assets, gross	10,592.4		$ 10,592.4
Accumulated amortization	4,833.5		4,688.2
Intangible assets, net	5,974.7		6,184.5
Non-Amortizable intangible assets, gross	215.8		280.3
Non-restructuring impairment charges	64.5	$ 0.0
Trademarks
Schedule of Intangible Asset by Major Class [Line Items]
Non-Amortizable intangible assets, gross	35.0		35.0
In-process Research and Development
Schedule of Intangible Asset by Major Class [Line Items]
Non-Amortizable intangible assets, gross	180.8		245.3
Completed Technology
Schedule of Intangible Asset by Major Class [Line Items]
Amortizable intangible assets, gross	10,394.6		10,394.6
Accumulated amortization	4,730.0		4,586.6
Trademarks
Schedule of Intangible Asset by Major Class [Line Items]
Amortizable intangible assets, gross	77.7		77.7
Accumulated amortization	24.4		23.5
Licensing Agreements [Member]
Schedule of Intangible Asset by Major Class [Line Items]
Amortizable intangible assets, gross	120.1		120.1
Accumulated amortization	79.1		78.1
Terlipressin [Member]
Schedule of Intangible Asset by Major Class [Line Items]
Intangible assets, net	81.0		$ 81.0
MNK-6105 [Member]
Goodwill and Intangible Assets Disclosure [Abstract]
Non-restructuring impairment charges	64.5
Schedule of Intangible Asset by Major Class [Line Items]
Non-restructuring impairment charges	$ 64.5