Condensed Consolidating Financial Statements (Schedule of Condensed Consolidating Statements of Cash Flows) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 29, 2019	Mar. 30, 2018
Cash Flows From Operating Activities:
Net cash from operating activities	$ 164.5	$ 17.8
Cash Flows From Investing Activities:
Capital expenditures	(39.8)	(34.3)
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	0.4	8.3
Net cash from investing activities	(39.4)	(427.6)
Cash Flows From Financing Activities:
Issuance of external debt	200.0	626.8
Repayment of external debt and capital lease obligation	(448.7)	(902.2)
Debt financing costs	0.0	(12.0)
Proceeds from exercise of share options	0.3	0.0
Repurchase of shares	(0.5)	(46.6)
Intercompany loan borrowings, net	0.0	0.0
Payment of Subsidiary Dividend	0.0	0.0
Capital contribution	0.0	0.0
Other	0.5	(4.8)
Net cash from financing activities	(248.4)	(338.8)
Effect of currency rate changes on cash	0.3	(0.3)
Net change in cash, cash equivalents and restricted cash	(123.0)	(748.9)
Cash and cash equivalents, end of period	225.8	511.9
Restricted Cash and Investments, Noncurrent	18.7	18.3
Cash and Cash Equivalents and Restricted Cash	367.5	1,279.1
Cash and Cash Equivalents, Including Restricted Cash, Period End	244.5	530.2
Mallinckrodt plc
Cash Flows From Operating Activities:
Net cash from operating activities	(6.6)	459.0
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	31.3	(412.2)
Investment in subsidiary	0.0	0.0
Other	0.0	0.0
Net cash from investing activities	31.3	(412.2)
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	0.3	0.0
Repurchase of shares	(0.5)	(46.6)
Intercompany loan borrowings, net	(24.9)	0.0
Payment of Subsidiary Dividend	0.0	0.0
Capital contribution	0.0	0.0
Other	0.5	0.5
Net cash from financing activities	(24.6)	(46.1)
Effect of currency rate changes on cash	0.0	0.0
Net change in cash, cash equivalents and restricted cash	0.1	0.7
Cash and cash equivalents, end of period	0.5	1.4
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	0.5	1.4
Mallinckrodt International Finance S.A.
Cash Flows From Operating Activities:
Net cash from operating activities	75.2	201.1
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	(85.3)
Investment in subsidiary	(480.8)	(121.8)
Other	0.0	0.0
Net cash from investing activities	(480.8)	(207.1)
Cash Flows From Financing Activities:
Issuance of external debt	0.0	600.0
Repayment of external debt and capital lease obligation	(39.0)	(530.6)
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	331.0	66.8
Payment of Subsidiary Dividend	0.0	(814.2)
Capital contribution	0.0	0.0
Other	0.0	0.0
Net cash from financing activities	292.0	(690.0)
Effect of currency rate changes on cash	0.0	0.0
Net change in cash, cash equivalents and restricted cash	(113.6)	(696.0)
Cash and cash equivalents, end of period	27.2	212.8
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	27.2	212.8
Other Subsidiaries
Cash Flows From Operating Activities:
Net cash from operating activities	95.9	776.5
Cash Flows From Investing Activities:
Capital expenditures	(39.8)	(34.3)
Acquisitions, net of cash	0.0	(699.9)
Proceeds from divestitures, net of cash	0.0	298.3
Intercompany loan investment, net	(337.4)	430.7
Investment in subsidiary	0.0	0.0
Other	0.4	8.3
Net cash from investing activities	(376.8)	3.1
Cash Flows From Financing Activities:
Issuance of external debt	200.0	26.8
Repayment of external debt and capital lease obligation	(409.7)	(371.6)
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
Payment of Subsidiary Dividend	0.0	(604.6)
Capital contribution	480.8	121.8
Other	0.0	(5.3)
Net cash from financing activities	271.1	(832.9)
Effect of currency rate changes on cash	0.3	(0.3)
Net change in cash, cash equivalents and restricted cash	(9.5)	(53.6)
Cash and cash equivalents, end of period	198.1	297.7
Restricted Cash and Investments, Noncurrent	18.7	18.3
Cash and Cash Equivalents and Restricted Cash	226.3	369.6
Cash and Cash Equivalents, Including Restricted Cash, Period End	216.8	316.0
Eliminations
Cash Flows From Operating Activities:
Net cash from operating activities	0.0	(1,418.8)
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	306.1	66.8
Investment in subsidiary	480.8	121.8
Other	0.0	0.0
Net cash from investing activities	786.9	188.6
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	(306.1)	(66.8)
Payment of Subsidiary Dividend	0.0	1,418.8
Capital contribution	(480.8)	(121.8)
Other	0.0	0.0
Net cash from financing activities	(786.9)	1,230.2
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