| Cover | Nov. 05, 2019 |
| Document Information [Line Items] | |
| Document Type | 8-K |
| Amendment Flag | false |
| Document Period End Date | Nov. 5, 2019 |
| Entity File Number | 001-36867 |
| Entity Registrant Name | ALLERGAN PLC |
| Entity Central Index Key | 0001578845 |
| Entity Tax Identification Number | 98-1114402 |
| Entity Incorporation, State or Country Code | L2 |
| Entity Address, Address Line One | Clonshaugh Business and Technology Park |
| Entity Address, Address Line Two | Coolock |
| Entity Address, City or Town | Dublin |
| Entity Address, Country | IE |
| Entity Address, Postal Zip Code | D17 E400 |
| City Area Code | 862 |
| Local Phone Number | 261-7000 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Entity Emerging Growth Company | false |
| Ordinary Share Par Value 0.0001 Per Share | |
| Document Information [Line Items] | |
| Title of 12(b) Security | Ordinary Share, par value $0.0001 per share |
| Trading Symbol | AGN |
| Security Exchange Name | NYSE |
| Floating Rate Notes Due 2020 | |
| Document Information [Line Items] | |
| Title of 12(b) Security | Floating rate notes due 2020 |
| Trading Symbol | AGN20A |
| Security Exchange Name | NYSE |
| 0.500 Percent notes due 2021 | |
| Document Information [Line Items] | |
| Title of 12(b) Security | 0.500% notes due 2021 |
| Trading Symbol | AGN21 |
| Security Exchange Name | NYSE |
| 1.500 Percent notes due 2023 | |
| Document Information [Line Items] | |
| Title of 12(b) Security | 1.500% notes due 2023 |
| Trading Symbol | AGN23A |
| Security Exchange Name | NYSE |
| 1.250 Percent notes due 2024 | |
| Document Information [Line Items] | |
| Title of 12(b) Security | 1.250% notes due 2024 |
| Trading Symbol | AGN24A |
| Security Exchange Name | NYSE |
| 2.625 Percent notes due 2028 | |
| Document Information [Line Items] | |
| Title of 12(b) Security | 2.625% notes due 2028 |
| Trading Symbol | AGN28 |
| Security Exchange Name | NYSE |
| 2.125 Percent notes due 2029 | |
| Document Information [Line Items] | |
| Title of 12(b) Security | 2.125% notes due 2029 |
| Trading Symbol | AGN29 |
| Security Exchange Name | NYSE |
