Condensed Consolidating Financial Statements (Schedule of Condensed Consolidating Statements of Cash Flows) (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 29, 2018	Jun. 30, 2017
Cash Flows From Operating Activities:
Net cash from operating activities	$ 261.8	$ 222.5
Cash Flows From Investing Activities:
Capital expenditures	(67.1)	(101.6)
Acquisitions, net of cash acquired	(699.9)	0.0
Proceeds from divestitures, net of cash	298.3	576.9
Intercompany loan investment, net	0.0	0.0
Investment in subsidiary	0.0	0.0
Other	12.4	(9.9)
Net cash from investing activities	(456.3)	465.4
Cash Flows From Financing Activities:
Issuance of external debt	657.2	40.0
Repayment of external debt and capital lease obligation	(1,392.8)	(332.8)
Debt financing costs	(12.0)	(13.0)
Proceeds from exercise of share options	0.0	3.9
Repurchase of shares	(56.8)	(380.8)
Intercompany loan borrowings, net	0.0	0.0
Payment of Subsidiary Dividend	0.0	0.0
Capital contribution	0.0	0.0
Other	(24.9)	(19.5)
Net cash from financing activities	(829.3)	(702.2)
Effect of currency rate changes on cash	(1.2)	1.6
Net change in cash, cash equivalents and restricted cash	(1,025.0)	(12.7)
Cash and cash equivalents, end of period	235.7	330.2
Restricted Cash and Investments, Noncurrent	18.4	18.2
Cash and Cash Equivalents and Restricted Cash	1,279.1	361.1
Cash and Cash Equivalents, Including Restricted Cash, Period End	254.1	348.4
Mallinckrodt plc
Cash Flows From Operating Activities:
Net cash from operating activities	453.6	1,177.0
Cash Flows From Investing Activities:
Capital expenditures	0.0	0.0
Acquisitions, net of cash acquired	0.0	0.0
Proceeds from divestitures, net of cash	0.0	0.0
Intercompany loan investment, net	(398.3)	(801.7)
Investment in subsidiary	0.0	0.0
Other	0.0	0.0
Net cash from investing activities	(398.3)	(801.7)
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	3.9
Repurchase of shares	(56.8)	(380.8)
Intercompany loan borrowings, net	0.0	0.0
Payment of Subsidiary Dividend	0.0	0.0
Capital contribution	0.0	0.0
Other	1.4	2.0
Net cash from financing activities	(55.4)	(374.9)
Effect of currency rate changes on cash	0.0	0.0
Net change in cash, cash equivalents and restricted cash	(0.1)	0.4
Cash and cash equivalents, end of period	0.6	0.9
Restricted Cash and Investments, Noncurrent	0.0	0.0
Cash and Cash Equivalents and Restricted Cash	0.7	0.5
Cash and Cash Equivalents, Including Restricted Cash, Period End	0.6	0.9
Mallinckrodt International Finance S.A.
Cash Flows From Operating Activities:
Net cash from operating activities	102.3	175.8
Cash Flows From Investing Activities:
Capital expenditures	0.0	0.0
Acquisitions, net of cash acquired	0.0	0.0
Proceeds from divestitures, net of cash	0.0	0.0
Intercompany loan investment, net	(85.2)	0.0
Investment in subsidiary	(163.1)	(307.9)
Other	0.0	0.0
Net cash from investing activities	(248.3)	(307.9)
Cash Flows From Financing Activities:
Issuance of external debt	600.0	0.0
Repayment of external debt and capital lease obligation	(1,011.2)	(242.1)
Debt financing costs	(12.0)	(12.5)
Proceeds from exercise of share options	0.0	0.0
Repurchase of shares	0.0	0.0
Intercompany loan borrowings, net	495.9	1,662.1
Payment of Subsidiary Dividend	(814.2)	(1,170.0)
Capital contribution	0.0	0.0
Other	0.0	0.0
Net cash from financing activities	(741.5)	237.5
Effect of currency rate changes on cash	0.0	0.0
Net change in cash, cash equivalents and restricted cash	(887.5)	105.4
Cash and cash equivalents, end of period	21.3	149.9
Restricted Cash and Investments, Noncurrent	0.0	0.0
Cash and Cash Equivalents and Restricted Cash	908.8	44.5
Cash and Cash Equivalents, Including Restricted Cash, Period End	21.3	149.9
Other Subsidiaries
Cash Flows From Operating Activities:
Net cash from operating activities	1,135.9	1,487.0
Cash Flows From Investing Activities:
Capital expenditures	(67.1)	(101.6)
Acquisitions, net of cash acquired	(699.9)	0.0
Proceeds from divestitures, net of cash	298.3	576.9
Intercompany loan investment, net	(12.4)	(860.4)
Investment in subsidiary	41.3	0.0
Other	12.4	(9.9)
Net cash from investing activities	(427.4)	(395.0)
Cash Flows From Financing Activities:
Issuance of external debt	57.2	40.0
Repayment of external debt and capital lease obligation	(381.6)	(90.7)
Debt financing costs	0.0	(0.5)
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
Payment of Subsidiary Dividend	(615.8)	(1,447.3)
Capital contribution	121.8	307.9
Other	(26.3)	(21.5)
Net cash from financing activities	(844.7)	(1,212.1)
Effect of currency rate changes on cash	(1.2)	1.6
Net change in cash, cash equivalents and restricted cash	(137.4)	(118.5)
Cash and cash equivalents, end of period	213.8	179.4
Restricted Cash and Investments, Noncurrent	18.4	18.2
Cash and Cash Equivalents and Restricted Cash	369.6	316.1
Cash and Cash Equivalents, Including Restricted Cash, Period End	232.2	197.6
Eliminations
Cash Flows From Operating Activities:
Net cash from operating activities	(1,430.0)	(2,617.3)
Cash Flows From Investing Activities:
Capital expenditures	0.0	0.0
Acquisitions, net of cash acquired	0.0	0.0
Proceeds from divestitures, net of cash	0.0	0.0
Intercompany loan investment, net	495.9	1,662.1
Investment in subsidiary	121.8	307.9
Other	0.0	0.0
Net cash from investing activities	617.7	1,970.0
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	(495.9)	(1,662.1)
Payment of Subsidiary Dividend	1,430.0	2,617.3
Capital contribution	(121.8)	(307.9)
Other	0.0	0.0
Net cash from financing activities	812.3	647.3
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