| Document and Entity Information Document | Aug. 04, 2020 | May 05, 2020 |
| Document and Entity Information [Abstract] | ||
| Entity Central Index Key | 0001567892 | |
| Title of 12(b) Security | Ordinary shares, par value $0.20 per share | |
| Written Communications | false | |
| Entity Incorporation, State or Country Code | L2 | |
| Document Type | 8-K | |
| Document Period End Date | Aug. 4, 2020 | |
| Entity Registrant Name | Mallinckrodt plc | |
| Entity File Number | 001-35803 | |
| Entity Tax Identification Number | 98-1088325 | |
| Entity Address, Address Line One | College Business & Technology Park | |
| Entity Address, City or Town | Dublin | |
| Entity Address, Postal Zip Code | 15 | |
| Entity Address, Country | IE | |
| City Area Code | 1 | |
| Local Phone Number | 696 0000 | |
| Soliciting Material | false | |
| Pre-commencement Tender Offer | false | |
| Pre-commencement Issuer Tender Offer | false | |
| Trading Symbol | MNK | |
| Security Exchange Name | NYSE | |
| Entity Emerging Growth Company | false | |
| Amendment Flag | false | |
| Entity Address, Address Line Two | Cruiserath | |
| Entity Address, Address Line Three | Blanchardstown | |
| Country Region | 353 |
