| Cover Page | Oct. 27, 2020 |
| Cover [Abstract] | |
| Document Type | 8-K |
| Document Period End Date | Oct. 27, 2020 |
| Entity Registrant Name | Systemax Inc. |
| Entity Incorporation, State or Country Code | DE |
| Entity File Number | 1-13792 |
| Entity Tax Identification Number | 11-3262067 |
| Entity Address, Address Line One | 11 Harbor Park Drive |
| Entity Address, City or Town | Port Washington |
| Entity Address, State or Province | NY |
| Entity Address, Postal Zip Code | 11050 |
| City Area Code | (516) |
| Local Phone Number | 608-7000 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Title of 12(b) Security | Common Stock ($.01 par value) |
| Trading Symbol | SYX |
| Security Exchange Name | NYSE |
| Entity Emerging Growth Company | false |
| Entity Central Index Key | 0000945114 |
| Amendment Flag | false |
