Restructuring and Related Charges (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 25, 2020	Dec. 27, 2019	Dec. 01, 2021	Feb. 01, 2018
Restructuring Cost and Reserve [Line Items]
Restructuring charges, net	$ 26.9	$ 37.5	$ (1.7)
2018 Program | Minimum
Restructuring Cost and Reserve [Line Items]
Mallinckrodt program expected cost range					$ 100.0
2018 Program | Maximum
Restructuring Cost and Reserve [Line Items]
Mallinckrodt program expected cost range					$ 125.0
Restructuring Fiscal 2021 Plan | Minimum
Restructuring Cost and Reserve [Line Items]
Mallinckrodt program expected cost range				$ 50.0
Restructuring Fiscal 2021 Plan | Maximum
Restructuring Cost and Reserve [Line Items]
Mallinckrodt program expected cost range				$ 100.0