Condensed Consolidating Financial Statements (Schedule of Condensed Consolidating Balance Sheets) (Details) - USD ($) $ in Millions	Jun. 28, 2019	Mar. 29, 2019	Dec. 28, 2018	Jun. 29, 2018	Mar. 30, 2018	Dec. 29, 2017
Current Assets:
Cash and cash equivalents	$ 241.1		$ 348.9	$ 235.7
Accounts receivable, net	528.4		623.3
Inventories	337.4		322.3
Prepaid expenses and other current assets	112.5		132.7
Intercompany receivables	0.0		0.0
Total current assets	1,219.4		1,427.2
Property, plant and equipment, net	994.2		982.0
Intangible assets, net	7,721.1		8,282.8
Investment in subsidiaries	0.0		0.0
Intercompany loans receivable	0.0		0.0
Other assets	287.0		185.3
Total Assets	10,221.7		10,877.3
Current Liabilities:
Current maturities of long-term debt	717.9		22.4
Accounts payable	148.6		147.5
Accrued payroll and payroll-related costs	79.8		124.0
Accrued interest	45.9		77.6
Accrued and other current liabilities	565.3		572.2
Intercompany payables	0.0		0.0
Total current liabilities	1,557.5		943.7
Long-term debt	4,823.0		6,069.2
Pension and postretirement benefits	59.5		60.5
Environmental liabilities	60.5		59.7
Deferred income taxes	53.4		324.3
Other income tax liabilities	262.5		228.0
Intercompany loans payable	0.0		0.0
Other liabilities	330.1		304.6
Total Liabilities	7,146.5		7,990.0
Shareholders' Equity	3,075.2	$ 3,053.9	2,887.3	6,474.4	$ 6,461.3	$ 6,522.0
Total Liabilities and Shareholders' Equity	10,221.7		10,877.3
Mallinckrodt plc
Current Assets:
Cash and cash equivalents	0.1		0.4	0.6
Accounts receivable, net	0.0		0.0
Inventories	0.0		0.0
Prepaid expenses and other current assets	0.3		3.9
Intercompany receivables	134.1		131.1
Total current assets	134.5		135.4
Property, plant and equipment, net	0.0		0.0
Intangible assets, net	0.0		0.0
Investment in subsidiaries	2,673.5		2,481.6
Intercompany loans receivable	462.3		497.7
Other assets	0.0		0.0
Total Assets	3,270.3		3,114.7
Current Liabilities:
Current maturities of long-term debt	0.0		0.0
Accounts payable	0.0		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
Intercompany payables	194.3		226.7
Total current liabilities	195.1		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	195.1		227.4
Shareholders' Equity	3,075.2		2,887.3
Total Liabilities and Shareholders' Equity	3,270.3		3,114.7
Mallinckrodt International Finance S.A.
Current Assets:
Cash and cash equivalents	4.9		140.8	21.3
Accounts receivable, net	0.0		0.0
Inventories	0.0		0.0
Prepaid expenses and other current assets	0.3		0.2
Intercompany receivables	28.9		29.2
Total current assets	34.1		170.2
Property, plant and equipment, net	0.0		0.0
Intangible assets, net	0.0		0.0
Investment in subsidiaries	12,937.0		25,506.1
Intercompany loans receivable	0.0		0.0
Other assets	0.0		0.0
Total Assets	12,971.1		25,676.3
Current Liabilities:
Current maturities of long-term debt	0.0		22.1
Accounts payable	0.0		0.0
Accrued payroll and payroll-related costs	0.0		0.0
Accrued interest	4.0		48.7
Accrued and other current liabilities	0.2		0.4
Intercompany payables	5,638.9		827.8
Total current liabilities	5,643.1		899.0
Long-term debt	397.6		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	3,076.2		12,840.7
Other liabilities	4.9		7.6
Total Liabilities	9,121.8		17,314.2
Shareholders' Equity	3,849.3		8,362.1
Total Liabilities and Shareholders' Equity	12,971.1		25,676.3
Other Subsidiaries
Current Assets:
Cash and cash equivalents	236.1		207.7	213.8
Accounts receivable, net	528.4		623.3
Inventories	337.4		322.3
Prepaid expenses and other current assets	111.9		128.6
Intercompany receivables	5,885.7		1,087.9
Total current assets	7,099.5		2,369.8
Property, plant and equipment, net	994.2		982.0
Intangible assets, net	7,721.1		8,282.8
Investment in subsidiaries	3,849.3		8,362.1
Intercompany loans receivable	2,613.9		12,343.0
Other assets	287.0		185.3
Total Assets	22,565.0		32,525.0
Current Liabilities:
Current maturities of long-term debt	717.9		0.3
Accounts payable	148.6		147.4
Accrued payroll and payroll-related costs	79.8		124.0
Accrued interest	41.9		28.9
Accrued and other current liabilities	564.3		571.2
Intercompany payables	215.5		193.7
Total current liabilities	1,768.0		1,065.5
Long-term debt	4,425.4		2,502.3
Pension and postretirement benefits	59.5		60.5
Environmental liabilities	60.5		59.7
Deferred income taxes	53.4		324.3
Other income tax liabilities	262.5		228.0
Intercompany loans payable	0.0		0.0
Other liabilities	325.2		297.0
Total Liabilities	6,954.5		4,537.3
Shareholders' Equity	15,610.5		27,987.7
Total Liabilities and Shareholders' Equity	22,565.0		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
Intercompany receivables	(6,048.7)		(1,248.2)
Total current assets	(6,048.7)		(1,248.2)
Property, plant and equipment, net	0.0		0.0
Intangible assets, net	0.0		0.0
Investment in subsidiaries	(19,459.8)		(36,349.8)
Intercompany loans receivable	(3,076.2)		(12,840.7)
Other assets	0.0		0.0
Total Assets	(28,584.7)		(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
Intercompany payables	(6,048.7)		(1,248.2)
Total current liabilities	(6,048.7)		(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	(3,076.2)		(12,840.7)
Other liabilities	0.0		0.0
Total Liabilities	(9,124.9)		(14,088.9)
Shareholders' Equity	(19,459.8)		(36,349.8)
Total Liabilities and Shareholders' Equity	(28,584.7)		(50,438.7)
Ordinary A
Condensed Consolidating Financial Statements
Ordinary A shares	$ 0.0		$ 0.0