Non-debtor Entity Intercompany Balances (Details) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 25, 2020
Non-debtor Entity Intercompany Balances [Line Items]
Non-Debtor Intercompany Receivables	$ 119.1	$ 282.3
Non-Debtor Intercompany Payables	$ 112.9	$ 120.3

Non-Debtor Intercompany Receivables From Debtor Entities

No definition available.

Name:	mnk_NonDebtorIntercompanyReceivablesFromDebtorEntities
Namespace Prefix:	mnk_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant