| Cover | Apr. 26, 2021 |
| Cover [Abstract] | |
| Document Type | 8-K/A |
| Amendment Flag | true |
| Amendment Description | This Amendment to the Current Report on Form 8-K originally filed on April 26, 2021 (the "Original 8-K") by OneSpan Inc. (the "Company") is being filed for the purpose of including as an exhibit a copy of the letter to stockholders issued in connection with the Company's 2021 annual meeting of stockholders, a link to which was included in the press release. A copy of the letter was inadvertently omitted from the Original 8-K. |
| Document Period End Date | Apr. 26, 2021 |
| Entity File Number | 000-24389 |
| Entity Registrant Name | OneSpan Inc. |
| Entity Central Index Key | 0001044777 |
| Entity Tax Identification Number | 36-4169320 |
| Entity Incorporation, State or Country Code | DE |
| Entity Address, Address Line One | 121 West Wacker Drive |
| Entity Address, Address Line Two | Suite 2050 |
| Entity Address, City or Town | Chicago |
| Entity Address, State or Province | IL |
| Entity Address, Postal Zip Code | 60601 |
| City Area Code | (312) |
| Local Phone Number | 766-4001 |
| 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 $.001 per share |
| Trading Symbol | OSPN |
| Security Exchange Name | NASDAQ |
| Entity Emerging Growth Company | false |
