Restructuring and Related Charges (Schedule of Net Restructuring and Related Charges) (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Dec. 30, 2016	Dec. 29, 2017	Sep. 30, 2016	Sep. 25, 2015
Restructuring Cost and Reserve [Line Items]
Total restructuring and related charges	$ 5.3	$ 36.4	$ 38.2	$ 45.3
Less: non-cash charges, including impairments and accelerated share based compensation expense	(1.5)	(5.2)	(4.9)	(10.1)
Total charges expected to be settled in cash	3.8	31.2	33.3	35.2
2016 Mallinckrodt Program
Restructuring Cost and Reserve [Line Items]
Total restructuring and related charges	5.2	36.2	8.3	0.0
2013 Mallinckrodt program
Restructuring Cost and Reserve [Line Items]
Total restructuring and related charges	0.0	0.7	26.2	12.0
Acquisition programs
Restructuring Cost and Reserve [Line Items]
Total restructuring and related charges	0.1	0.9	3.7	33.6
Other programs
Restructuring Cost and Reserve [Line Items]
Total restructuring and related charges	$ 0.0	$ 0.0	$ 0.0	$ 0.3