Condensed Consolidating Financial Statements (Schedule of Condensed Consolidating Statements of Cash Flows) (Details) - USD ($) $ in Millions	3 Months Ended
	Dec. 30, 2016	Dec. 25, 2015
Cash Flows From Operating Activities:
Net cash provided by (used in) operating activities	$ 195.6	$ 311.4
Cash Flows From Investing Activities:
Capital expenditures	(65.2)	(49.0)
Proceeds from disposal of discontinued operations, net of cash	0.0	264.0
Cash paid with acquisition	(1.8)
Intercompany loan investment, net	0.0	0.0
Investment in subsidiary	0.0	0.0
Restricted cash	0.0	(0.1)
Other	(10.2)	0.7
Net cash used in investing activities	(77.2)	215.6
Cash Flows From Financing Activities:
Issuance of external debt	190.0	62.0
Repayment of external debt and capital leases	(86.7)	(129.6)
Debt financing costs	0.0	(0.1)
Excess tax benefit from share-based compensation		0.0
Proceeds from exercise of share options	0.4	3.6
Repurchase of shares	(158.8)	(275.4)
Intercompany loan borrowings, net	0.0	0.0
Capital contribution	0.0	0.0
Other	1.2	(30.0)
Net cash (used in) provided by financing activities	(53.9)	(369.5)
Effect of currency rate changes on cash	(3.0)	(1.5)
Net increase in cash and cash equivalents	61.5	156.0
Cash and cash equivalents at beginning of period	280.5	365.9
Cash and cash equivalents at end of period	342.0	521.9
Mallinckrodt plc
Cash Flows From Operating Activities:
Net cash provided by (used in) operating activities	17.4	39.2
Cash Flows From Investing Activities:
Capital expenditures	0.0	0.0
Proceeds from disposal of discontinued operations, net of cash	0.0	0.0
Cash paid with acquisition	0.0
Intercompany loan investment, net	0.0	0.0
Investment in subsidiary	0.0	0.0
Restricted cash	0.0	0.0
Other	0.0	0.0
Net cash used in investing activities	0.0	0.0
Cash Flows From Financing Activities:
Issuance of external debt	0.0	0.0
Repayment of external debt and capital leases	0.0	0.0
Debt financing costs	0.0	0.0
Excess tax benefit from share-based compensation		0.0
Proceeds from exercise of share options	0.4	3.6
Repurchase of shares	(158.8)	(275.4)
Intercompany loan borrowings, net	140.0	232.8
Capital contribution	0.0	0.0
Other	1.2	0.0
Net cash (used in) provided by financing activities	(17.2)	(39.0)
Effect of currency rate changes on cash	0.0	0.0
Net increase in cash and cash equivalents	0.2	0.2
Cash and cash equivalents at beginning of period	0.3	0.1
Cash and cash equivalents at end of period	0.5	0.3
Mallinckrodt International Finance S.A.
Cash Flows From Operating Activities:
Net cash provided by (used in) operating activities	(94.0)	51.9
Cash Flows From Investing Activities:
Capital expenditures	0.0	0.0
Proceeds from disposal of discontinued operations, net of cash	0.0	235.4
Cash paid with acquisition	0.0
Intercompany loan investment, net	0.0	(105.8)
Investment in subsidiary	(260.0)	(46.2)
Restricted cash	0.0	0.0
Other	0.0	0.0
Net cash used in investing activities	(260.0)	83.4
Cash Flows From Financing Activities:
Issuance of external debt	175.0	0.0
Repayment of external debt and capital leases	(86.2)	(128.9)
Debt financing costs	0.0	0.0
Excess tax benefit from share-based compensation		0.0
Proceeds from exercise of share options	0.0	0.0
Repurchase of shares	0.0	0.0
Intercompany loan borrowings, net	284.7	0.0
Capital contribution	0.0	0.0
Other	0.0	0.0
Net cash (used in) provided by financing activities	373.5	(128.9)
Effect of currency rate changes on cash	0.0	0.0
Net increase in cash and cash equivalents	19.5	6.4
Cash and cash equivalents at beginning of period	25.0	152.1
Cash and cash equivalents at end of period	44.5	158.5
Other Subsidiaries
Cash Flows From Operating Activities:
Net cash provided by (used in) operating activities	272.2	220.3
Cash Flows From Investing Activities:
Capital expenditures	(65.2)	(49.0)
Proceeds from disposal of discontinued operations, net of cash	0.0	28.6
Cash paid with acquisition	(1.8)
Intercompany loan investment, net	(424.7)	(127.0)
Investment in subsidiary	0.0	0.0
Restricted cash	0.0	(0.1)
Other	(10.2)	0.7
Net cash used in investing activities	(501.9)	(146.8)
Cash Flows From Financing Activities:
Issuance of external debt	15.0	62.0
Repayment of external debt and capital leases	(0.5)	(0.7)
Debt financing costs	0.0	(0.1)
Excess tax benefit from share-based compensation		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
Capital contribution	260.0	46.2
Other	0.0	(30.0)
Net cash (used in) provided by financing activities	274.5	77.4
Effect of currency rate changes on cash	(3.0)	(1.5)
Net increase in cash and cash equivalents	41.8	149.4
Cash and cash equivalents at beginning of period	255.2	213.7
Cash and cash equivalents at end of period	297.0	363.1
Eliminations
Cash Flows From Operating Activities:
Net cash provided by (used in) operating activities	0.0	0.0
Cash Flows From Investing Activities:
Capital expenditures	0.0	0.0
Proceeds from disposal of discontinued operations, net of cash	0.0	0.0
Cash paid with acquisition	0.0
Intercompany loan investment, net	424.7	232.8
Investment in subsidiary	260.0	46.2
Restricted cash	0.0	0.0
Other	0.0	0.0
Net cash used in investing activities	684.7	279.0
Cash Flows From Financing Activities:
Issuance of external debt	0.0	0.0
Repayment of external debt and capital leases	0.0	0.0
Debt financing costs	0.0	0.0
Excess tax benefit from share-based compensation		0.0
Proceeds from exercise of share options	0.0	0.0
Repurchase of shares	0.0	0.0
Intercompany loan borrowings, net	(424.7)	(232.8)
Capital contribution	(260.0)	(46.2)
Other	0.0	0.0
Net cash (used in) provided by financing activities	(684.7)	(279.0)
Effect of currency rate changes on cash	0.0	0.0
Net increase in cash and cash equivalents	0.0	0.0
Cash and cash equivalents at beginning of period	0.0	0.0
Cash and cash equivalents at end of period	$ 0.0	$ 0.0