Condensed Consolidating Financial Statements (Schedule of Condensed Consolidating Statements of Cash Flows) (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 28, 2018	Sep. 29, 2017
Cash Flows From Operating Activities:
Net cash from operating activities	$ 481.1	$ 448.5
Cash Flows From Investing Activities:
Capital expenditures	(93.3)	(151.3)
Acquisitions, net of cash acquired	(699.9)	(35.9)
Proceeds from divestitures, net of cash	313.2	576.9
Intercompany loan investment, net	0.0	0.0
Investment in subsidiary	0.0	0.0
Other	28.8	0.5
Net cash from investing activities	(451.2)	390.2
Cash Flows From Financing Activities:
Issuance of external debt	657.2	540.0
Repayment of external debt and capital lease obligation	(1,563.4)	(887.5)
Debt financing costs	(12.0)	(12.7)
Proceeds from exercise of share options	1.0	4.0
Repurchase of shares	(57.4)	(437.7)
Intercompany loan borrowings, net	0.0	0.0
Payment of Subsidiary Dividend	0.0	0.0
Capital contribution	0.0	0.0
Other	(24.3)	(18.6)
Net cash from financing activities	(998.9)	(812.5)
Effect of currency rate changes on cash	(0.9)	2.7
Net change in cash, cash equivalents and restricted cash	(969.9)	28.9
Cash and cash equivalents, end of period	290.7	371.8
Restricted Cash and Investments, Noncurrent	18.5	18.2
Cash and Cash Equivalents and Restricted Cash	1,279.1	361.1
Cash and Cash Equivalents, Including Restricted Cash, Period End	309.2	390.0
Mallinckrodt plc
Cash Flows From Operating Activities:
Net cash from operating activities	447.6	1,172.0
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	(393.6)	(741.3)
Investment in subsidiary	0.0	0.0
Other	0.0	0.0
Net cash from investing activities	(393.6)	(741.3)
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	1.0	4.0
Repurchase of shares	(57.4)	(437.7)
Intercompany loan borrowings, net	0.0	0.0
Payment of Subsidiary Dividend	0.0	0.0
Capital contribution	0.0	0.0
Other	2.0	3.2
Net cash from financing activities	(54.4)	(430.5)
Effect of currency rate changes on cash	0.0	0.0
Net change in cash, cash equivalents and restricted cash	(0.4)	0.2
Cash and cash equivalents, end of period	0.3	0.7
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	0.3	0.7
Mallinckrodt International Finance S.A.
Cash Flows From Operating Activities:
Net cash from operating activities	43.0	1,233.7
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	(168.3)	(1,412.5)
Other	0.0	0.0
Net cash from investing activities	(253.5)	(1,412.5)
Cash Flows From Financing Activities:
Issuance of external debt	600.0	500.0
Repayment of external debt and capital lease obligation	(1,166.8)	(759.9)
Debt financing costs	(12.0)	(12.7)
Proceeds from exercise of share options	0.0	0.0
Repurchase of shares	0.0	0.0
Intercompany loan borrowings, net	846.0	1,614.5
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	(547.0)	171.9
Effect of currency rate changes on cash	0.0	0.0
Net change in cash, cash equivalents and restricted cash	(757.5)	(6.9)
Cash and cash equivalents, end of period	151.3	37.6
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	151.3	37.6
Other Subsidiaries
Cash Flows From Operating Activities:
Net cash from operating activities	1,420.5	1,963.0
Cash Flows From Investing Activities:
Capital expenditures	(93.3)	(151.3)
Acquisitions, net of cash acquired	(699.9)	(35.9)
Proceeds from divestitures, net of cash	313.2	576.9
Intercompany loan investment, net	(367.2)	(920.8)
Investment in subsidiary	0.0	0.0
Other	28.8	0.5
Net cash from investing activities	(818.4)	(530.6)
Cash Flows From Financing Activities:
Issuance of external debt	57.2	40.0
Repayment of external debt and capital lease obligation	(396.6)	(127.6)
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	47.6
Payment of Subsidiary Dividend	(615.8)	(2,750.2)
Capital contribution	168.3	1,412.5
Other	(26.3)	(21.8)
Net cash from financing activities	(813.2)	(1,399.5)
Effect of currency rate changes on cash	(0.9)	2.7
Net change in cash, cash equivalents and restricted cash	(212.0)	35.6
Cash and cash equivalents, end of period	139.1	333.5
Restricted Cash and Investments, Noncurrent	18.5	18.2
Cash and Cash Equivalents and Restricted Cash	369.6	316.1
Cash and Cash Equivalents, Including Restricted Cash, Period End	157.6	351.7
Eliminations
Cash Flows From Operating Activities:
Net cash from operating activities	(1,430.0)	(3,920.2)
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	846.0	1,662.1
Investment in subsidiary	168.3	1,412.5
Other	0.0	0.0
Net cash from investing activities	1,014.3	3,074.6
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	(846.0)	(1,662.1)
Payment of Subsidiary Dividend	1,430.0	3,920.2
Capital contribution	(168.3)	(1,412.5)
Other	0.0	0.0
Net cash from financing activities	415.7	845.6
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