| Cover | May 17, 2021 |
| Cover [Abstract] | |
| Document Type | 8-K |
| Amendment Flag | false |
| Document Period End Date | May 17, 2021 |
| Current Fiscal Year End Date | --12-31 |
| Entity File Number | 001-35328 |
| Entity Registrant Name | AEGION CORPORATION |
| Entity Central Index Key | 0000353020 |
| Entity Tax Identification Number | 45-3117900 |
| Entity Incorporation, State or Country Code | DE |
| Entity Address, Address Line One | 17988 Edison Avenue |
| Entity Address, City or Town | Chesterfield |
| Entity Address, State or Province | MO |
| Entity Address, Postal Zip Code | 63005 |
| City Area Code | 636 |
| Local Phone Number | 530-8000 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Title of 12(b) Security | Class A Common Shares, $0.01 par value |
| Trading Symbol | AEGN |
| Security Exchange Name | NASDAQ |
| Entity Emerging Growth Company | false |
