Condensed Consolidating Financial Statements (Schedule of Condensed Consolidating Statements of Comprehensive Income) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 28, 2018	Sep. 29, 2017	Sep. 28, 2018	Sep. 29, 2017
Condensed Consolidating Financial Statements
Net sales	$ 640.0	$ 600.6	$ 1,844.3	$ 1,760.7
Cost of sales	326.2	268.0	936.7	808.3
Gross profit	313.8	332.6	907.6	952.4
Selling, general and administrative expenses	164.0	186.3	520.7	618.5
Research and development expenses	78.5	46.9	223.9	144.2
Restructuring charges, net	14.7	15.4	96.5	26.3
Losses (gains) on divestiture and license	0.6	0.4	0.6	(56.6)
Operating income	56.0	83.6	65.9	220.0
Interest expense	(93.6)	(92.6)	(280.1)	(279.0)
Interest income	2.0	1.3	6.6	2.8
Other income (expense), net	13.4	3.0	17.5	(70.6)
Intercompany Interest And Fees	0.0	0.0	0.0	0.0
Income (Loss) from Equity Method Investments	0.0	0.0	0.0	0.0
Loss from continuing operations before income taxes	(22.2)	(4.7)	(190.1)	(126.8)
Income tax benefit	(125.2)	(57.8)	(222.0)	(153.4)
Income (Loss) from Continuing Operations	103.0	53.1	31.9	26.6
(Loss) income from discontinued operations, net of income taxes	10.8	10.6	79.5	499.1
Net Income (Loss)	113.8	63.7	111.4	525.7
Other Comprehensive Income (Loss), Net of Tax	3.0	(5.1)	(4.3)	59.4
Comprehensive Income (Loss)	116.8	58.6	107.1	585.1
Mallinckrodt plc
Condensed Consolidating Financial Statements
Net sales	0.0	0.0	0.0	0.0
Cost of sales	0.7	0.9	1.6	1.8
Gross profit	(0.7)	(0.9)	(1.6)	(1.8)
Selling, general and administrative expenses	12.4	13.4	30.1	46.7
Research and development expenses	1.6	1.8	3.8	3.6
Restructuring charges, net	0.0	0.0	0.0	0.0
Losses (gains) on divestiture and license	0.0	0.0	0.0	0.0
Operating income	(14.7)	(16.1)	(35.5)	(52.1)
Interest expense	(1.6)	(3.3)	(6.2)	(10.0)
Interest income	2.4	2.2	6.8	5.3
Other income (expense), net	2.3	1.4	9.0	19.0
Intercompany Interest And Fees	(3.5)	(4.3)	(12.0)	(13.3)
Income (Loss) from Equity Method Investments	127.8	82.4	145.9	572.1
Loss from continuing operations before income taxes	112.7	62.3	108.0	521.0
Income tax benefit	(1.1)	(1.4)	(3.4)	(4.7)
Income (Loss) from Continuing Operations	113.8	63.7	111.4	525.7
(Loss) income from discontinued operations, net of income taxes	0.0	0.0	0.0	0.0
Net Income (Loss)	113.8	63.7	111.4	525.7
Other Comprehensive Income (Loss), Net of Tax	3.0	(5.1)	(4.3)	59.4
Comprehensive Income (Loss)	116.8	58.6	107.1	585.1
Mallinckrodt International Finance S.A.
Condensed Consolidating Financial Statements
Net sales	0.0	0.0	0.0	0.0
Cost of sales	0.0	0.0	0.0	0.0
Gross profit	0.0	0.0	0.0	0.0
Selling, general and administrative expenses	0.1	0.2	0.5	0.6
Research and development expenses	0.0	0.0	0.0	0.0
Restructuring charges, net	0.0	0.0	0.0	0.0
Losses (gains) on divestiture and license	0.0	0.0	0.0	0.0
Operating income	(0.1)	(0.2)	(0.5)	(0.6)
Interest expense	(112.0)	(90.9)	(323.2)	(264.9)
Interest income	249.6	0.4	251.6	1.0
Other income (expense), net	(156.8)	1.7	(154.0)	(1.6)
Intercompany Interest And Fees	(0.1)	0.0	(0.1)	0.0
Income (Loss) from Equity Method Investments	238.9	261.8	647.2	1,113.5
Loss from continuing operations before income taxes	219.5	172.8	421.0	847.4
Income tax benefit	(2.4)	(2.1)	(4.4)	(2.6)
Income (Loss) from Continuing Operations	221.9	174.9	425.4	850.0
(Loss) income from discontinued operations, net of income taxes	0.0	(0.2)	0.0	(1.9)
Net Income (Loss)	221.9	174.7	425.4	848.1
Other Comprehensive Income (Loss), Net of Tax	3.0	(5.1)	(4.3)	59.4
Comprehensive Income (Loss)	224.9	169.6	421.1	907.5
Other Subsidiaries
Condensed Consolidating Financial Statements
Net sales	640.0	600.6	1,844.3	1,760.7
Cost of sales	325.5	267.1	935.1	806.5
Gross profit	314.5	333.5	909.2	954.2
Selling, general and administrative expenses	151.5	172.7	490.1	571.2
Research and development expenses	76.9	45.1	220.1	140.6
Restructuring charges, net	14.7	15.4	96.5	26.3
Losses (gains) on divestiture and license	0.6	0.4	0.6	(56.6)
Operating income	70.8	99.9	101.9	272.7
Interest expense	(257.4)	(19.0)	(272.2)	(57.9)
Interest income	27.4	19.3	69.7	50.3
Other income (expense), net	167.9	(0.1)	162.5	(88.0)
Intercompany Interest And Fees	3.6	4.3	12.1	13.3
Income (Loss) from Equity Method Investments	221.9	174.7	425.4	848.1
Loss from continuing operations before income taxes	234.2	279.1	499.4	1,038.5
Income tax benefit	(121.7)	(54.3)	(214.2)	(146.1)
Income (Loss) from Continuing Operations	355.9	333.4	713.6	1,184.6
(Loss) income from discontinued operations, net of income taxes	10.8	10.8	79.5	501.0
Net Income (Loss)	366.7	344.2	793.1	1,685.6
Other Comprehensive Income (Loss), Net of Tax	5.8	(10.5)	(9.3)	117.9
Comprehensive Income (Loss)	372.5	333.7	783.8	1,803.5
Eliminations
Condensed Consolidating Financial Statements
Net sales	0.0	0.0	0.0	0.0
Cost of sales	0.0	0.0	0.0	0.0
Gross profit	0.0	0.0	0.0	0.0
Selling, general and administrative expenses	0.0	0.0	0.0	0.0
Research and development expenses	0.0	0.0	0.0	0.0
Restructuring charges, net	0.0	0.0	0.0	0.0
Losses (gains) on divestiture and license	0.0	0.0	0.0	0.0
Operating income	0.0	0.0	0.0	0.0
Interest expense	277.4	20.6	321.5	53.8
Interest income	(277.4)	(20.6)	(321.5)	(53.8)
Other income (expense), net	0.0	0.0	0.0	0.0
Intercompany Interest And Fees	0.0	0.0	0.0	0.0
Income (Loss) from Equity Method Investments	(588.6)	(518.9)	(1,218.5)	(2,533.7)
Loss from continuing operations before income taxes	(588.6)	(518.9)	(1,218.5)	(2,533.7)
Income tax benefit	0.0	0.0	0.0	0.0
Income (Loss) from Continuing Operations	(588.6)	(518.9)	(1,218.5)	(2,533.7)
(Loss) income from discontinued operations, net of income taxes	0.0	0.0	0.0	0.0
Net Income (Loss)	(588.6)	(518.9)	(1,218.5)	(2,533.7)
Other Comprehensive Income (Loss), Net of Tax	(8.8)	15.6	13.6	(177.3)
Comprehensive Income (Loss)	$ (597.4)	$ (503.3)	$ (1,204.9)	$ (2,711.0)