Condensed Consolidating and Combining Financial Statements (Schedule of Condensed Consolidating and Combining Statements of Comprehensive Income) (Details) - USD ($) $ in Millions		3 Months Ended								12 Months Ended
		Sep. 30, 2016	Jun. 24, 2016	Mar. 25, 2016	Dec. 25, 2015	Sep. 25, 2015	Jun. 26, 2015	Mar. 27, 2015	Dec. 26, 2014	Sep. 30, 2016	Sep. 25, 2015	Sep. 26, 2014
Condensed Consolidating Financial Statements
Net sales		$ 887.2	$ 866.6	$ 815.8	$ 811.2	$ 778.8	$ 768.5	$ 709.5	$ 666.3	$ 3,380.8	$ 2,923.1	$ 1,650.3
Cost of sales										1,525.8	1,300.2	765.7
Gross profit		490.2	488.8	425.1	450.9	425.8	441.7	399.7	355.7	1,855.0	1,622.9	884.6
Selling, general and administrative expenses										925.3	1,023.8	611.0
Research and development expenses										262.2	203.3	140.5
Separation costs										0.0	0.0	9.6
Restructuring charges, net										33.3	45.0	68.0
Non-restructuring impairment charges										16.9	0.0	27.1
Gain on divestiture and license										0.0	(3.0)	(15.0)
Operating income (loss)										617.3	353.8	43.4
Interest expense										(384.6)	(255.6)	(82.6)
Interest income										1.3	1.0	1.5
Other income (expense), net										(0.6)	8.1	3.1
Intercompany interest and fees										0.0	0.0	0.0
Equity in net income of subsidiaries										0.0	0.0	0.0
Income (loss) from continuing operations before income taxes	[1]									233.4	107.3	(34.6)
Income Tax Expense (Benefit)	[1]									(255.6)	(129.3)	(12.6)
Income (loss) from continuing operations		110.0	176.7	98.5	103.8	73.1	34.6	55.3	73.6	489.0	236.6	(22.0)
Income (loss) from discontinued operations, net of income taxes		5.0	22.6	19.8	107.3	2.1	23.4	43.5	19.1	154.7	88.1	(297.3)
Net income (loss)		$ 115.0	$ 199.3	$ 118.3	$ 211.1	$ 75.2	$ 58.0	$ 98.8	$ 92.7	643.7	324.7	(319.3)
Other comprehensive loss, net of tax										(86.5)	(64.8)	(42.8)
Comprehensive income (loss)										557.2	259.9	(362.1)
Mallinckrodt plc
Condensed Consolidating Financial Statements
Net sales										0.0	0.0	0.0
Cost of sales										0.0	0.0	0.0
Gross profit										0.0	0.0	0.0
Selling, general and administrative expenses										51.3	116.3	37.7
Research and development expenses										0.0	0.0	0.0
Separation costs										0.0	0.0	2.5
Restructuring charges, net										0.0	9.8	35.3
Non-restructuring impairment charges										0.0	0.0	0.0
Gain on divestiture and license										0.0	0.0	0.0
Operating income (loss)										(51.3)	(126.1)	(75.5)
Interest expense										(230.3)	(96.4)	0.0
Interest income										0.0	0.0	0.0
Other income (expense), net										90.0	216.3	30.9
Intercompany interest and fees										16.1	14.7	9.0
Equity in net income of subsidiaries										820.8	330.6	(264.8)
Income (loss) from continuing operations before income taxes										613.1	309.7	(318.4)
Income Tax Expense (Benefit)										(30.6)	(15.9)	0.0
Income (loss) from continuing operations										643.7	325.6	(318.4)
Income (loss) from discontinued operations, net of income taxes										0.0	(0.9)	(0.9)
Net income (loss)										643.7	324.7	(319.3)
Other comprehensive loss, net of tax										(86.5)	(64.8)	(42.8)
Comprehensive income (loss)										557.2	259.9	(362.1)
Mallinckrodt International Finance S.A.
Condensed Consolidating Financial Statements
Net sales										0.0	0.0	0.0
Cost of sales										0.0	0.0	0.0
Gross profit										0.0	0.0	0.0
Selling, general and administrative expenses										0.8	15.7	7.3
Research and development expenses										0.0	0.0	0.0
Separation costs										0.0	0.0	0.0
Restructuring charges, net										0.0	0.0	0.0
Non-restructuring impairment charges										0.0	0.0	0.0
Gain on divestiture and license										0.0	0.0	0.0
Operating income (loss)										(0.8)	(15.7)	(7.3)
Interest expense										(327.0)	(230.2)	(86.3)
Interest income										0.5	0.1	0.0
Other income (expense), net										1.7	0.0	0.0
Intercompany interest and fees										0.0	0.0	0.0
Equity in net income of subsidiaries										1,327.2	496.3	(171.2)
Income (loss) from continuing operations before income taxes										1,001.6	250.5	(264.8)
Income Tax Expense (Benefit)										(18.1)	0.0	0.0
Income (loss) from continuing operations										1,019.7	250.5	(264.8)
Income (loss) from discontinued operations, net of income taxes										38.2	0.0	0.0
Net income (loss)										1,057.9	250.5	(264.8)
Other comprehensive loss, net of tax										(86.5)	(64.8)	(42.8)
Comprehensive income (loss)										971.4	185.7	(307.6)
Other Subsidiaries
Condensed Consolidating Financial Statements
Net sales										3,380.8	2,923.1	1,650.3
Cost of sales										1,525.8	1,300.2	765.7
Gross profit										1,855.0	1,622.9	884.6
Selling, general and administrative expenses										873.2	891.8	566.0
Research and development expenses										262.2	203.3	140.5
Separation costs										0.0	0.0	7.1
Restructuring charges, net										33.3	35.2	32.7
Non-restructuring impairment charges										16.9	0.0	27.1
Gain on divestiture and license										0.0	(3.0)	(15.0)
Operating income (loss)										669.4	495.6	126.2
Interest expense										(82.4)	(25.2)	0.0
Interest income										255.9	97.1	5.2
Other income (expense), net										(92.3)	(208.2)	(27.8)
Intercompany interest and fees										(16.1)	(14.7)	(9.0)
Equity in net income of subsidiaries										1,057.9	250.5	(300.2)
Income (loss) from continuing operations before income taxes										1,824.6	624.5	(187.6)
Income Tax Expense (Benefit)										(206.9)	(113.4)	(12.6)
Income (loss) from continuing operations										2,031.5	737.9	(175.0)
Income (loss) from discontinued operations, net of income taxes										116.5	89.0	(296.4)
Net income (loss)										2,148.0	826.9	(471.4)
Other comprehensive loss, net of tax										(173.5)	(69.9)	(84.1)
Comprehensive income (loss)										1,974.5	757.0	(555.5)
Eliminations
Condensed Consolidating Financial Statements
Net sales										0.0	0.0	0.0
Cost of sales										0.0	0.0	0.0
Gross profit										0.0	0.0	0.0
Selling, general and administrative expenses										0.0	0.0	0.0
Research and development expenses										0.0	0.0	0.0
Separation costs										0.0	0.0	0.0
Restructuring charges, net										0.0	0.0	0.0
Non-restructuring impairment charges										0.0	0.0	0.0
Gain on divestiture and license										0.0	0.0	0.0
Operating income (loss)										0.0	0.0	0.0
Interest expense										255.1	96.2	3.7
Interest income										(255.1)	(96.2)	(3.7)
Other income (expense), net										0.0	0.0	0.0
Intercompany interest and fees										0.0	0.0	0.0
Equity in net income of subsidiaries										(3,205.9)	(1,077.4)	736.2
Income (loss) from continuing operations before income taxes										(3,205.9)	(1,077.4)	736.2
Income Tax Expense (Benefit)										0.0	0.0	0.0
Income (loss) from continuing operations										(3,205.9)	(1,077.4)	736.2
Income (loss) from discontinued operations, net of income taxes										0.0	0.0	0.0
Net income (loss)										(3,205.9)	(1,077.4)	736.2
Other comprehensive loss, net of tax										260.0	134.7	126.9
Comprehensive income (loss)										$ (2,945.9)	$ (942.7)	$ 863.1

[1] Domestic reflects U.K. in fiscal 2016 and 2015, and U.S. federal and state in fiscal 2014.