| Document and Entity Information | Jan. 01, 2020 |
| Cover page. | |
| Document Type | 8-K |
| Document Period End Date | Jan. 1, 2020 |
| Entity Registrant Name | AmerisourceBergen Corp |
| Entity Central Index Key | 0001140859 |
| Amendment Flag | false |
| Entity Incorporation, State or Country Code | DE |
| Entity File Number | 1-6671 |
| Entity Tax Identification Number | 23-3079390 |
| Entity Address, Address Line One | 1300 Morris Drive |
| Entity Address, City or Town | Chesterbrook, |
| Entity Address, State or Province | PA |
| Entity Address, Postal Zip Code | 19087-5594 |
| City Area Code | 610 |
| Local Phone Number | 727-7000 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Title of 12(b) Security | Common stock |
| Trading Symbol | ABC |
| Security Exchange Name | NYSE |
| Entity Emerging Growth Company | false |
