| Document and Entity Information | Feb. 25, 2021 |
| Cover [Abstract] | |
| Document Type | 8-K |
| Amendment Flag | false |
| Document Period End Date | Feb. 25, 2021 |
| Entity Registrant Name | Olympic Steel, Inc. |
| Entity Incorporation, State or Country Code | OH |
| Entity File Number | 000-23320 |
| Entity Tax Identification Number | 34-1245650 |
| Entity Address, Address Line One | 5096 Richmond Road |
| Entity Address, City or Town | Bedford Heights |
| Entity Address, State or Province | OH |
| Entity Address, Postal Zip Code | 44146 |
| City Area Code | 216 |
| Local Phone Number | 292-3800 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Entity Emerging Growth Company | false |
| Entity Central Index Key | 0000917470 |
| Title of 12(b) Security | Common stock, without par value |
| Trading Symbol | ZEUS |
| Security Exchange Name | NASDAQ |
