Condensed Consolidating Financial Statements (Schedule of Condensed Consolidating Statements of Cash Flows) (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 28, 2019	Jun. 29, 2018
Cash Flows From Operating Activities:
Net cash from operating activities	$ 467.4	$ 261.8
Cash Flows From Investing Activities:
Capital expenditures	(77.6)	(67.1)
Acquisitions, net of cash	0.0	(699.9)
Proceeds from divestitures, net of cash	0.0	298.3
Intercompany loan investment, net	0.0	0.0
Investment in subsidiary	0.0	0.0
Other	8.2	12.4
Net cash from investing activities	(69.4)	(456.3)
Cash Flows From Financing Activities:
Issuance of external debt	200.0	657.2
Repayment of external debt and capital lease obligation	(685.9)	(1,392.8)
Debt financing costs	0.0	(12.0)
Proceeds from exercise of share options	0.5	0.0
Repurchase of shares	(2.5)	(56.8)
Intercompany loan borrowings, net	0.0	0.0
Intercompany dividends	0.0	0.0
Capital contribution	0.0	0.0
Other	(18.5)	(24.9)
Net cash from financing activities	(506.4)	(829.3)
Effect of currency rate changes on cash	0.8	(1.2)
Net change in cash, cash equivalents and restricted cash	(107.6)	(1,025.0)
Cash and cash equivalents, end of period	241.1	235.7
Restricted Cash and Investments, Noncurrent	18.8	18.4
Cash and Cash Equivalents and Restricted Cash	367.5	1,279.1
Cash and Cash Equivalents, Including Restricted Cash, Period End	259.9	254.1
Mallinckrodt plc
Cash Flows From Operating Activities:
Net cash from operating activities	(16.2)	453.6
Cash Flows From Investing Activities:
Capital expenditures	0.0	0.0
Acquisitions, net of cash	0.0	0.0
Proceeds from divestitures, net of cash	0.0	0.0
Intercompany loan investment, net	40.9	(398.3)
Investment in subsidiary	0.0	0.0
Other	0.0	0.0
Net cash from investing activities	40.9	(398.3)
Cash Flows From Financing Activities:
Issuance of external debt	0.0	0.0
Repayment of external debt and capital lease obligation	0.0	0.0
Debt financing costs	0.0	0.0
Proceeds from exercise of share options	0.5	0.0
Repurchase of shares	(2.5)	(56.8)
Intercompany loan borrowings, net	(24.9)	0.0
Intercompany dividends	0.0	0.0
Capital contribution	0.0	0.0
Other	1.9	1.4
Net cash from financing activities	(25.0)	(55.4)
Effect of currency rate changes on cash	0.0	0.0
Net change in cash, cash equivalents and restricted cash	(0.3)	(0.1)
Cash and cash equivalents, end of period	0.1	0.6
Restricted Cash and Investments, Noncurrent	0.0	0.0
Cash and Cash Equivalents and Restricted Cash	0.4	0.7
Cash and Cash Equivalents, Including Restricted Cash, Period End	0.1	0.6
Mallinckrodt International Finance S.A.
Cash Flows From Operating Activities:
Net cash from operating activities	56.5	102.3
Cash Flows From Investing Activities:
Capital expenditures	0.0	0.0
Acquisitions, net of cash	0.0	0.0
Proceeds from divestitures, net of cash	0.0	0.0
Intercompany loan investment, net	0.0	(85.2)
Investment in subsidiary	(658.6)	(163.1)
Other	0.0	0.0
Net cash from investing activities	(658.6)	(248.3)
Cash Flows From Financing Activities:
Issuance of external debt	0.0	600.0
Repayment of external debt and capital lease obligation	(98.6)	(1,011.2)
Debt financing costs	0.0	(12.0)
Proceeds from exercise of share options	0.0	0.0
Repurchase of shares	0.0	0.0
Intercompany loan borrowings, net	564.8	495.9
Intercompany dividends	0.0	(814.2)
Capital contribution	0.0	0.0
Other	0.0	0.0
Net cash from financing activities	466.2	(741.5)
Effect of currency rate changes on cash	0.0	0.0
Net change in cash, cash equivalents and restricted cash	(135.9)	(887.5)
Cash and cash equivalents, end of period	4.9	21.3
Restricted Cash and Investments, Noncurrent	0.0	0.0
Cash and Cash Equivalents and Restricted Cash	140.8	908.8
Cash and Cash Equivalents, Including Restricted Cash, Period End	4.9	21.3
Other Subsidiaries
Cash Flows From Operating Activities:
Net cash from operating activities	430.8	1,135.9
Cash Flows From Investing Activities:
Capital expenditures	(77.6)	(67.1)
Acquisitions, net of cash	0.0	(699.9)
Proceeds from divestitures, net of cash	0.0	298.3
Intercompany loan investment, net	(580.8)	(12.4)
Investment in subsidiary	0.0	41.3
Other	8.2	12.4
Net cash from investing activities	(650.2)	(427.4)
Cash Flows From Financing Activities:
Issuance of external debt	200.0	57.2
Repayment of external debt and capital lease obligation	(587.3)	(381.6)
Debt financing costs	0.0	0.0
Proceeds from exercise of share options	0.0	0.0
Repurchase of shares	0.0	0.0
Intercompany loan borrowings, net	0.0	0.0
Intercompany dividends	(3.7)	(615.8)
Capital contribution	658.6	121.8
Other	(20.4)	(26.3)
Net cash from financing activities	247.2	(844.7)
Effect of currency rate changes on cash	0.8	(1.2)
Net change in cash, cash equivalents and restricted cash	28.6	(137.4)
Cash and cash equivalents, end of period	236.1	213.8
Restricted Cash and Investments, Noncurrent	18.8	18.4
Cash and Cash Equivalents and Restricted Cash	226.3	369.6
Cash and Cash Equivalents, Including Restricted Cash, Period End	254.9	232.2
Eliminations
Cash Flows From Operating Activities:
Net cash from operating activities	(3.7)	(1,430.0)
Cash Flows From Investing Activities:
Capital expenditures	0.0	0.0
Acquisitions, net of cash	0.0	0.0
Proceeds from divestitures, net of cash	0.0	0.0
Intercompany loan investment, net	539.9	495.9
Investment in subsidiary	658.6	121.8
Other	0.0	0.0
Net cash from investing activities	1,198.5	617.7
Cash Flows From Financing Activities:
Issuance of external debt	0.0	0.0
Repayment of external debt and capital lease obligation	0.0	0.0
Debt financing costs	0.0	0.0
Proceeds from exercise of share options	0.0	0.0
Repurchase of shares	0.0	0.0
Intercompany loan borrowings, net	(539.9)	(495.9)
Intercompany dividends	3.7	1,430.0
Capital contribution	(658.6)	(121.8)
Other	0.0	0.0
Net cash from financing activities	(1,194.8)	812.3
Effect of currency rate changes on cash	0.0	0.0
Net change in cash, cash equivalents and restricted cash	0.0	0.0
Cash and cash equivalents, end of period	0.0	0.0
Restricted Cash and Investments, Noncurrent	0.0	0.0
Cash and Cash Equivalents and Restricted Cash	0.0	0.0
Cash and Cash Equivalents, Including Restricted Cash, Period End	$ 0.0	$ 0.0