Condensed Consolidating and Combining Financial Statements (Schedule of Condensed Consolidating and Combining Statements of Cash Flows) (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 25, 2016	Sep. 30, 2016	Sep. 25, 2015	Sep. 26, 2014
Cash Flows From Operating Activities:
Net cash (used in) provided by operating activities		$ 1,184.6	$ 896.4	$ 373.4
Cash Flows From Investing Activities:
Capital expenditures		(182.9)	(148.0)	(127.8)
Acquisitions and intangibles, net of cash acquired		(245.4)	(2,154.7)	(2,793.8)
Proceeds from Divestiture of Businesses, Net of Cash Divested		267.0	0.0	0.0
Intercompany Loan Investment		0.0	0.0	0.0
Subsidiary dividend proceeds				0.0
Investment in subsidiary		0.0	0.0	0.0
Proceeds from Divestiture of Subsidiary		0.0
Payments to Acquire Subsidiary		0.0
Restricted cash	$ 21.1	47.3	3.1	4.1
Other		6.0	3.0	26.7
Net cash used in investing activities		(108.0)	(2,296.6)	(2,890.8)
Cash Flows From Financing Activities:
Issuance of external debt		98.3	3,010.0	3,043.2
Repayment of capital leases		(568.6)	(1,848.4)	(34.8)
Excess tax benefit from share-based compensation		0.0	34.1	8.9
Debt financing costs		(0.1)	(39.9)	(71.7)
Proceeds from exercise of share options		14.0	34.4	25.8
Cash Dividends Paid to Parent Company by Consolidated Subsidiaries				0.0
Intercompany loan borrowings		0.0	0.0	0.0
Capital contribution		0.0	0.0	0.0
Repurchase of ordinary shares, value		(652.9)	(92.2)	(17.5)
Other		(53.0)	(28.1)	0.0
Net cash provided by financing activities		(1,162.3)	1,069.9	2,953.9
Effect of currency rate changes on cash		0.3	(11.6)	(4.2)
Net (decrease) increase in cash and cash equivalents		(85.4)	(341.9)	432.3
Cash and cash equivalents at beginning of period		365.9	707.8	275.5
Cash and cash equivalents at end of period		280.5	365.9	707.8
Mallinckrodt plc
Cash Flows From Operating Activities:
Net cash (used in) provided by operating activities		17.9	207.0	18.2
Cash Flows From Investing Activities:
Capital expenditures		0.0	0.0	0.0
Acquisitions and intangibles, net of cash acquired		0.0	0.0	0.0
Proceeds from Divestiture of Businesses, Net of Cash Divested		0.0
Intercompany Loan Investment		0.0	(149.4)	(25.0)
Subsidiary dividend proceeds				0.0
Investment in subsidiary		0.0	0.0	0.0
Proceeds from Divestiture of Subsidiary		3.4
Payments to Acquire Subsidiary		0.0
Restricted cash		0.0	0.0	0.0
Other		0.0	0.0	0.0
Net cash used in investing activities		3.4	(149.4)	(25.0)
Cash Flows From Financing Activities:
Issuance of external debt		0.0	0.0	0.0
Repayment of capital leases		0.0	0.0	0.0
Excess tax benefit from share-based compensation		0.0	0.0	0.0
Debt financing costs		0.0	0.0	0.0
Proceeds from exercise of share options		14.0	34.4	25.8
Cash Dividends Paid to Parent Company by Consolidated Subsidiaries				0.0
Intercompany loan borrowings		(617.8)	0.0	(2.4)
Capital contribution		0.0	0.0	0.0
Repurchase of ordinary shares, value		652.9	92.2	(17.5)
Other		0.0	0.0	0.0
Net cash provided by financing activities		(21.1)	(57.8)	5.9
Effect of currency rate changes on cash		0.0	0.0	0.0
Net (decrease) increase in cash and cash equivalents		0.2	(0.2)	(0.9)
Cash and cash equivalents at beginning of period		0.1	0.3	1.2
Cash and cash equivalents at end of period		0.3	0.1	0.3
Mallinckrodt International Finance S.A.
Cash Flows From Operating Activities:
Net cash (used in) provided by operating activities		(47.4)	(148.2)	(65.0)
Cash Flows From Investing Activities:
Capital expenditures		0.0	0.0	0.0
Acquisitions and intangibles, net of cash acquired		0.0	0.0	0.0
Proceeds from Divestiture of Businesses, Net of Cash Divested		234.0
Intercompany Loan Investment		(175.2)	0.0	(298.1)
Subsidiary dividend proceeds				(300.5)
Investment in subsidiary		(861.2)	(3,014.4)	(3,735.5)
Proceeds from Divestiture of Subsidiary		0.0
Payments to Acquire Subsidiary		0.0
Restricted cash		0.0	0.0	0.0
Other		0.0	0.0	0.0
Net cash used in investing activities		(802.4)	(3,014.4)	(3,733.1)
Cash Flows From Financing Activities:
Issuance of external debt		0.0	2,890.0	2,893.3
Repayment of capital leases		(549.2)	(258.3)	(3.3)
Excess tax benefit from share-based compensation		0.0	0.0	0.0
Debt financing costs		0.0	(39.1)	(70.7)
Proceeds from exercise of share options		0.0	0.0	0.0
Cash Dividends Paid to Parent Company by Consolidated Subsidiaries				0.0
Intercompany loan borrowings		(1,271.9)	(703.6)	(940.8)
Capital contribution		0.0	0.0	0.0
Repurchase of ordinary shares, value		0.0	0.0	0.0
Other		0.0	0.0	0.0
Net cash provided by financing activities		722.7	3,296.2	3,760.1
Effect of currency rate changes on cash		0.0	0.0	0.0
Net (decrease) increase in cash and cash equivalents		(127.1)	133.6	(38.0)
Cash and cash equivalents at beginning of period		152.1	18.5	56.5
Cash and cash equivalents at end of period		25.0	152.1	18.5
Other Subsidiaries
Cash Flows From Operating Activities:
Net cash (used in) provided by operating activities		1,214.1	837.6	420.2
Cash Flows From Investing Activities:
Capital expenditures		(182.9)	(148.0)	(127.8)
Acquisitions and intangibles, net of cash acquired		(245.4)	(2,154.7)	(2,793.8)
Proceeds from Divestiture of Businesses, Net of Cash Divested		33.0
Intercompany Loan Investment		(1,714.5)	(554.2)	(915.8)
Subsidiary dividend proceeds				0.0
Investment in subsidiary		0.0	0.0	0.0
Proceeds from Divestiture of Subsidiary		0.0
Payments to Acquire Subsidiary		3.4
Restricted cash		47.3	3.1	4.1
Other		6.0	3.0	26.7
Net cash used in investing activities		(2,059.9)	(2,850.8)	(3,806.6)
Cash Flows From Financing Activities:
Issuance of external debt		98.3	120.0	149.9
Repayment of capital leases		(19.4)	(1,590.1)	(31.5)
Excess tax benefit from share-based compensation		0.0	34.1	8.9
Debt financing costs		(0.1)	(0.8)	(1.0)
Proceeds from exercise of share options		0.0	0.0	0.0
Cash Dividends Paid to Parent Company by Consolidated Subsidiaries				(300.5)
Intercompany loan borrowings		0.0	0.0	(300.5)
Capital contribution		861.2	3,014.4	3,735.5
Repurchase of ordinary shares, value		0.0	0.0	0.0
Other		(53.0)	(28.1)	0.0
Net cash provided by financing activities		887.0	1,549.5	3,861.8
Effect of currency rate changes on cash		0.3	(11.6)	(4.2)
Net (decrease) increase in cash and cash equivalents		41.5	(475.3)	471.2
Cash and cash equivalents at beginning of period		213.7	689.0	217.8
Cash and cash equivalents at end of period		255.2	213.7	689.0
Eliminations
Cash Flows From Operating Activities:
Net cash (used in) provided by operating activities		0.0	0.0	0.0
Cash Flows From Investing Activities:
Capital expenditures		0.0	0.0	0.0
Acquisitions and intangibles, net of cash acquired		0.0	0.0	0.0
Proceeds from Divestiture of Businesses, Net of Cash Divested		0.0
Intercompany Loan Investment		(1,889.7)	(703.6)	(1,238.9)
Subsidiary dividend proceeds				300.5
Investment in subsidiary		861.2	3,014.4	3,735.5
Proceeds from Divestiture of Subsidiary		(3.4)
Payments to Acquire Subsidiary		(3.4)
Restricted cash		0.0	0.0	0.0
Other		0.0	0.0	0.0
Net cash used in investing activities		2,750.9	3,718.0	4,673.9
Cash Flows From Financing Activities:
Issuance of external debt		0.0	0.0	0.0
Repayment of capital leases		0.0	0.0	0.0
Excess tax benefit from share-based compensation		0.0	0.0	0.0
Debt financing costs		0.0	0.0	0.0
Proceeds from exercise of share options		0.0	0.0	0.0
Cash Dividends Paid to Parent Company by Consolidated Subsidiaries				300.5
Intercompany loan borrowings		1,889.7	703.6	1,238.9
Capital contribution		(861.2)	(3,014.4)	(3,735.5)
Repurchase of ordinary shares, value		0.0	0.0	0.0
Other		0.0	0.0	0.0
Net cash provided by financing activities		(2,750.9)	(3,718.0)	(4,673.9)
Effect of currency rate changes on cash		0.0	0.0	0.0
Net (decrease) increase in cash and cash equivalents		0.0	0.0	0.0
Cash and cash equivalents at beginning of period		0.0	0.0	0.0
Cash and cash equivalents at end of period		$ 0.0	$ 0.0	$ 0.0