| Document And Entity Information | Aug. 12, 2019 |
| Document And Entity Information [Abstract] | |
| Document Type | 8-K |
| Amendment Flag | false |
| Document Period End Date | Aug. 12, 2019 |
| Entity Registrant Name | INSIGHT ENTERPRISES INC |
| Entity Central Index Key | 0000932696 |
| Entity Emerging Growth Company | false |
| Entity File Number | 0-25092 |
| Entity Incorporation, State or Country Code | DE |
| Entity Tax Identification Number | 86-0766246 |
| Entity Address, Address Line One | 6820 South Harl Avenue |
| Entity Address, City or Town | Tempe |
| Entity Address, State or Province | AZ |
| Entity Address, Postal Zip Code | 85283 |
| City Area Code | 480 |
| Local Phone Number | 333-3000 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Title of 12(b) Security | Common stock, par value $0.01 |
| Trading Symbol | NSIT |
| Security Exchange Name | NASDAQ |
