Condensed Consolidating Financial Statements (Schedule of Condensed Consolidating Balance Sheets) (Details) - USD ($) $ in Millions	Sep. 28, 2018	Dec. 29, 2017	Sep. 29, 2017
Current Assets:
Cash and cash equivalents	$ 290.7	$ 1,260.9	$ 371.8
Accounts receivable, net	349.6	275.4
Inventories	143.4	128.7
Prepaid expenses and other current assets	117.7	74.7
Notes receivable	0.0	154.0
Current assets held for sale	1,136.8	391.5
Intercompany receivables	0.0	0.0
Total current assets	2,038.2	2,285.2
Property, plant and equipment, net	439.3	413.2
Goodwill	3,675.4	3,482.7
Intangible assets, net	8,585.2	8,261.0
Long-term assets held for sale	0.0	742.7
Investment in subsidiaries	0.0	0.0
Intercompany loans receivable	0.0	0.0
Other assets	170.5	156.2
Total Assets	14,908.6	15,341.0
Current Liabilities:
Current maturities of long-term debt	16.7	313.7
Accounts payable	76.6	77.3
Accrued payroll and payroll-related costs	89.0	78.4
Accrued interest	77.0	57.0
Income taxes payable	43.4	15.5
Accrued and other current liabilities	437.5	368.5
Current liabilities held for sale	182.4	140.0
Intercompany payables	0.0	0.0
Total current liabilities	922.6	1,050.4
Long-term debt	6,174.0	6,420.9
Pension and postretirement benefits	65.2	67.1
Environmental liabilities	49.8	62.8
Deferred income taxes	668.9	749.1
Other income tax liabilities	127.6	94.1
Long-term liabilities held for sale	0.0	22.6
Intercompany loans payable	0.0	0.0
Other liabilities	296.9	352.0
Total Liabilities	8,305.0	8,819.0
Shareholders' Equity	6,603.6	6,522.0
Total Liabilities and Shareholders' Equity	14,908.6	15,341.0
Mallinckrodt plc
Current Assets:
Cash and cash equivalents	0.3	0.7	0.7
Accounts receivable, net	0.0	0.0
Inventories	0.0	0.0
Prepaid expenses and other current assets	3.3	1.0
Notes receivable	0.0	0.0
Current assets held for sale	0.0	0.0
Intercompany receivables	192.0	70.0
Total current assets	195.6	71.7
Property, plant and equipment, net	0.0	0.0
Goodwill	0.0	0.0
Intangible assets, net	0.0	0.0
Long-term assets held for sale		0.0
Investment in subsidiaries	6,194.4	6,551.6
Intercompany loans receivable	504.0	593.1
Other assets	0.0	0.0
Total Assets	6,894.0	7,216.4
Current Liabilities:
Current maturities of long-term debt	0.0	0.0
Accounts payable	0.1	0.1
Accrued payroll and payroll-related costs	0.0	0.0
Accrued interest	0.0	0.0
Income taxes payable	0.0	0.0
Accrued and other current liabilities	1.6	0.8
Current liabilities held for sale	0.0	0.0
Intercompany payables	288.7	693.5
Total current liabilities	290.4	694.4
Long-term debt	0.0	0.0
Pension and postretirement benefits	0.0	0.0
Environmental liabilities	0.0	0.0
Deferred income taxes	0.0	0.0
Other income tax liabilities	0.0	0.0
Long-term liabilities held for sale		0.0
Intercompany loans payable	0.0	0.0
Other liabilities	0.0	0.0
Total Liabilities	290.4	694.4
Shareholders' Equity	6,603.6	6,522.0
Total Liabilities and Shareholders' Equity	6,894.0	7,216.4
Mallinckrodt International Finance S.A.
Current Assets:
Cash and cash equivalents	151.3	908.8	37.6
Accounts receivable, net	0.0	0.0
Inventories	0.0	0.0
Prepaid expenses and other current assets	0.2	0.2
Notes receivable	0.0	0.0
Current assets held for sale	0.0	0.0
Intercompany receivables	52.2	173.4
Total current assets	203.7	1,082.4
Property, plant and equipment, net	0.0	0.0
Goodwill	0.0	0.0
Intangible assets, net	0.0	0.0
Long-term assets held for sale		0.0
Investment in subsidiaries	29,157.0	23,217.8
Intercompany loans receivable	0.0	0.0
Other assets	0.0	0.0
Total Assets	29,360.7	24,300.2
Current Liabilities:
Current maturities of long-term debt	16.5	313.5
Accounts payable	0.1	0.0
Accrued payroll and payroll-related costs	0.0	0.0
Accrued interest	76.2	53.0
Income taxes payable	0.0	0.0
Accrued and other current liabilities	0.4	0.4
Current liabilities held for sale	0.0	0.0
Intercompany payables	19.4	104.6
Total current liabilities	112.6	471.5
Long-term debt	3,698.3	6,206.8
Pension and postretirement benefits	0.0	0.0
Environmental liabilities	0.0	0.0
Deferred income taxes	0.0	0.0
Other income tax liabilities	0.0	0.0
Long-term liabilities held for sale		0.0
Intercompany loans payable	13,577.8	5,257.9
Other liabilities	7.8	7.8
Total Liabilities	17,396.5	11,944.0
Shareholders' Equity	11,964.2	12,356.2
Total Liabilities and Shareholders' Equity	29,360.7	24,300.2
Other Subsidiaries
Current Assets:
Cash and cash equivalents	139.1	351.4	333.5
Accounts receivable, net	349.6	275.4
Inventories	143.4	128.7
Prepaid expenses and other current assets	114.2	73.5
Notes receivable	0.0	154.0
Current assets held for sale	1,136.8	391.5
Intercompany receivables	353.5	831.4
Total current assets	2,236.6	2,205.9
Property, plant and equipment, net	439.3	413.2
Goodwill	3,675.4	3,482.7
Intangible assets, net	8,585.2	8,261.0
Long-term assets held for sale		742.7
Investment in subsidiaries	11,964.2	12,356.2
Intercompany loans receivable	13,073.8	4,664.8
Other assets	170.5	156.2
Total Assets	40,145.0	32,282.7
Current Liabilities:
Current maturities of long-term debt	0.2	0.2
Accounts payable	76.4	77.2
Accrued payroll and payroll-related costs	89.0	78.4
Accrued interest	0.8	4.0
Income taxes payable	43.4	15.5
Accrued and other current liabilities	435.5	367.3
Current liabilities held for sale	182.4	140.0
Intercompany payables	289.6	276.7
Total current liabilities	1,117.3	959.3
Long-term debt	2,475.7	214.1
Pension and postretirement benefits	65.2	67.1
Environmental liabilities	49.8	62.8
Deferred income taxes	668.9	749.1
Other income tax liabilities	127.6	94.1
Long-term liabilities held for sale		22.6
Intercompany loans payable	0.0	0.0
Other liabilities	289.1	344.2
Total Liabilities	4,793.6	2,513.3
Shareholders' Equity	35,351.4	29,769.4
Total Liabilities and Shareholders' Equity	40,145.0	32,282.7
Eliminations
Current Assets:
Cash and cash equivalents	0.0	0.0	$ 0.0
Accounts receivable, net	0.0	0.0
Inventories	0.0	0.0
Prepaid expenses and other current assets	0.0	0.0
Notes receivable	0.0	0.0
Current assets held for sale	0.0	0.0
Intercompany receivables	(597.7)	(1,074.8)
Total current assets	(597.7)	(1,074.8)
Property, plant and equipment, net	0.0	0.0
Goodwill	0.0	0.0
Intangible assets, net	0.0	0.0
Long-term assets held for sale		0.0
Investment in subsidiaries	(47,315.6)	(42,125.6)
Intercompany loans receivable	(13,577.8)	(5,257.9)
Other assets	0.0	0.0
Total Assets	(61,491.1)	(48,458.3)
Current Liabilities:
Current maturities of long-term debt	0.0	0.0
Accounts payable	0.0	0.0
Accrued payroll and payroll-related costs	0.0	0.0
Accrued interest	0.0	0.0
Income taxes payable	0.0	0.0
Accrued and other current liabilities	0.0	0.0
Current liabilities held for sale	0.0	0.0
Intercompany payables	(597.7)	(1,074.8)
Total current liabilities	(597.7)	(1,074.8)
Long-term debt	0.0	0.0
Pension and postretirement benefits	0.0	0.0
Environmental liabilities	0.0	0.0
Deferred income taxes	0.0	0.0
Other income tax liabilities	0.0	0.0
Long-term liabilities held for sale		0.0
Intercompany loans payable	(13,577.8)	(5,257.9)
Other liabilities	0.0	0.0
Total Liabilities	(14,175.5)	(6,332.7)
Shareholders' Equity	(47,315.6)	(42,125.6)
Total Liabilities and Shareholders' Equity	(61,491.1)	(48,458.3)
Ordinary A
Condensed Consolidating Financial Statements
Ordinary A shares	$ 0.0	$ 0.0