| Cover | May 25, 2021 |
| Cover [Abstract] | |
| Document Type | 8-K |
| Amendment Flag | false |
| Document Period End Date | May 25, 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 |
