| Document and Entity Information Document | Sep. 06, 2019 |
| Document And Entity Information [Abstract] | |
| Title of 12(b) Security | Ordinary shares, par value $0.20 per share |
| Trading Symbol | MNK |
| Written Communications | false |
| Soliciting Material | false |
| Security Exchange Name | NYSE |
| Pre-commencement Tender Offer | false |
| Entity Incorporation, State or Country Code | L2 |
| Entity File Number | 001-35803 |
| Entity Central Index Key | 0001567892 |
| Amendment Flag | false |
| Document Type | 8-K |
| Document Period End Date | Sep. 6, 2019 |
| Entity Registrant Name | Mallinckrodt plc |
| Entity Address, Address Line One | 3 Lotus Park, The Causeway |
| Entity Address, City or Town | Staines-Upon-Thames |
| Entity Address, Postal Zip Code | TW18 3AG |
| Entity Address, Country | GB |
| City Area Code | 017 |
| Local Phone Number | 8463 6700 |
| Entity Emerging Growth Company | false |
| Entity Tax Identification Number | 98-1088325 |
| Pre-commencement Issuer Tender Offer | false |
