Condensed Consolidating Financial Statements (Schedule of Condensed Consolidating Balance Sheets) (Details) - USD ($) $ in Millions	Sep. 27, 2019	Jun. 28, 2019	Mar. 29, 2019	Dec. 28, 2018	Sep. 28, 2018	Jun. 29, 2018	Mar. 30, 2018	Dec. 29, 2017
Current Assets:
Cash and cash equivalents	$ 498.8			$ 348.9	$ 290.7
Accounts receivable, net	538.8			623.3
Inventories	325.5			322.3
Prepaid expenses and other current assets	122.2			132.7
Assets held for sale	175.9			0.0
Intercompany receivables	0.0			0.0
Total current assets	1,661.2			1,427.2
Property, plant and equipment, net	894.7			982.0
Intangible assets, net	7,496.1			8,282.8
Investment in subsidiaries	0.0			0.0
Intercompany loans receivable	0.0			0.0
Other assets	304.1			185.3
Total Assets	10,356.1			10,877.3
Current Liabilities:
Current maturities of long-term debt	716.1			22.4
Accounts payable	100.9			147.5
Accrued payroll and payroll-related costs	83.7			124.0
Accrued interest	90.9			77.6
Accrued and other current liabilities	506.5			572.2
Liabilities held for sale	55.8			0.0
Intercompany payables	0.0			0.0
Total current liabilities	1,553.9			943.7
Long-term debt	5,048.7			6,069.2
Pension and postretirement benefits	58.6			60.5
Environmental liabilities	60.3			59.7
Deferred income taxes	22.0			324.3
Other income tax liabilities	253.5			228.0
Intercompany loans payable	0.0			0.0
Other liabilities	278.7			304.6
Total Liabilities	7,275.7			7,990.0
Shareholders' Equity	3,080.4	$ 3,075.2	$ 3,053.9	2,887.3	6,603.6	$ 6,474.4	$ 6,461.3	$ 6,522.0
Total Liabilities and Shareholders' Equity	10,356.1			10,877.3
Mallinckrodt plc
Current Assets:
Cash and cash equivalents	0.7			0.4	0.3
Accounts receivable, net	0.0			0.0
Inventories	0.0			0.0
Prepaid expenses and other current assets	11.8			3.9
Assets held for sale	0.0
Intercompany receivables	128.2			131.1
Total current assets	140.7			135.4
Property, plant and equipment, net	0.0			0.0
Intangible assets, net	0.0			0.0
Investment in subsidiaries	2,684.4			2,481.6
Intercompany loans receivable	447.9			497.7
Other assets	0.0			0.0
Total Assets	3,273.0			3,114.7
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
Accrued and other current liabilities	0.8			0.6
Liabilities held for sale	0.0
Intercompany payables	191.7			226.7
Total current liabilities	192.6			227.4
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
Intercompany loans payable	0.0			0.0
Other liabilities	0.0			0.0
Total Liabilities	192.6			227.4
Shareholders' Equity	3,080.4			2,887.3
Total Liabilities and Shareholders' Equity	3,273.0			3,114.7
Mallinckrodt International Finance S.A.
Current Assets:
Cash and cash equivalents	64.5			140.8	151.3
Accounts receivable, net	0.0			0.0
Inventories	0.0			0.0
Prepaid expenses and other current assets	0.2			0.2
Assets held for sale	0.0
Intercompany receivables	29.2			29.2
Total current assets	93.9			170.2
Property, plant and equipment, net	0.0			0.0
Intangible assets, net	0.0			0.0
Investment in subsidiaries	15,633.9			25,506.1
Intercompany loans receivable	0.0			0.0
Other assets	0.0			0.0
Total Assets	15,727.8			25,676.3
Current Liabilities:
Current maturities of long-term debt	696.7			22.1
Accounts payable	0.0			0.0
Accrued payroll and payroll-related costs	0.0			0.0
Accrued interest	8.1			48.7
Accrued and other current liabilities	0.2			0.4
Liabilities held for sale	0.0
Intercompany payables	5,732.8			827.8
Total current liabilities	6,437.8			899.0
Long-term debt	2,250.5			3,566.9
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
Intercompany loans payable	3,157.7			12,840.7
Other liabilities	4.8			7.6
Total Liabilities	11,850.8			17,314.2
Shareholders' Equity	3,877.0			8,362.1
Total Liabilities and Shareholders' Equity	15,727.8			25,676.3
Other Subsidiaries
Current Assets:
Cash and cash equivalents	433.6			207.7	139.1
Accounts receivable, net	538.8			623.3
Inventories	325.5			322.3
Prepaid expenses and other current assets	110.2			128.6
Assets held for sale	175.9
Intercompany receivables	5,980.2			1,087.9
Total current assets	7,564.2			2,369.8
Property, plant and equipment, net	894.7			982.0
Intangible assets, net	7,496.1			8,282.8
Investment in subsidiaries	3,877.0			8,362.1
Intercompany loans receivable	2,709.8			12,343.0
Other assets	304.1			185.3
Total Assets	22,845.9			32,525.0
Current Liabilities:
Current maturities of long-term debt	19.4			0.3
Accounts payable	100.8			147.4
Accrued payroll and payroll-related costs	83.7			124.0
Accrued interest	82.8			28.9
Accrued and other current liabilities	505.5			571.2
Liabilities held for sale	55.8
Intercompany payables	213.1			193.7
Total current liabilities	1,061.1			1,065.5
Long-term debt	2,798.2			2,502.3
Pension and postretirement benefits	58.6			60.5
Environmental liabilities	60.3			59.7
Deferred income taxes	22.0			324.3
Other income tax liabilities	253.5			228.0
Intercompany loans payable	0.0			0.0
Other liabilities	273.9			297.0
Total Liabilities	4,527.6			4,537.3
Shareholders' Equity	18,318.3			27,987.7
Total Liabilities and Shareholders' Equity	22,845.9			32,525.0
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
Assets held for sale	0.0
Intercompany receivables	(6,137.6)			(1,248.2)
Total current assets	(6,137.6)			(1,248.2)
Property, plant and equipment, net	0.0			0.0
Intangible assets, net	0.0			0.0
Investment in subsidiaries	(22,195.3)			(36,349.8)
Intercompany loans receivable	(3,157.7)			(12,840.7)
Other assets	0.0			0.0
Total Assets	(31,490.6)			(50,438.7)
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
Accrued and other current liabilities	0.0			0.0
Liabilities held for sale	0.0
Intercompany payables	(6,137.6)			(1,248.2)
Total current liabilities	(6,137.6)			(1,248.2)
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
Intercompany loans payable	(3,157.7)			(12,840.7)
Other liabilities	0.0			0.0
Total Liabilities	(9,295.3)			(14,088.9)
Shareholders' Equity	(22,195.3)			(36,349.8)
Total Liabilities and Shareholders' Equity	(31,490.6)			(50,438.7)
Ordinary A
Condensed Consolidating Financial Statements
Ordinary A shares	$ 0.0			$ 0.0