Document and Entity Information - USD ($)	12 Months Ended
	Dec. 31, 2020	Feb. 22, 2021	Jun. 30, 2020
Document And Entity Information
Document Type	10-K
Document Period End Date	Dec. 31, 2020
Document Annual Report	true
Document Transition Report	false
Entity Registrant Name	OneSpan Inc.
Entity File Number	000-24389
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	36-4169320
Entity Address, Address Line One	121 West Wacker Drive, 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
Title of 12(b) Security	Common Stock, par value $.001 per share
Trading Symbol	OSPN
Security Exchange Name	NASDAQ
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Emerging Growth Company	false
Entity Small Business	false
Entity Shell Company	false
Icfr Auditor Attestation Flag	true
Entity Common Stock, Shares Outstanding		40,391,202
Entity Central Index Key	0001044777
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	FY
Amendment Flag	false
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Public Float			$ 955,147,012