Document And Entity Information - USD ($)	12 Months Ended
	Dec. 31, 2021	Jan. 28, 2022	Jun. 30, 2021
Document Information [Line Items]
Entity Central Index Key	0000097134
Entity Registrant Name	TENNANT CO
Amendment Flag	false
Current Fiscal Year End Date	--12-31
Document Fiscal Period Focus	FY
Document Fiscal Year Focus	2021
Document Type	10-K
Document Annual Report	true
Document Period End Date	Dec. 31, 2021
Document Transition Report	false
Entity File Number	001-16191
Entity Incorporation, State or Country Code	MN
Entity Tax Identification Number	41-0572550
Entity Address, Address Line One	10400 Clean Street
Entity Address, City or Town	Eden Prairie
Entity Address, State or Province	MN
Entity Address, Postal Zip Code	55344
City Area Code	763
Local Phone Number	540-1200
Title of 12(b) Security	Common Stock, par value $0.375 per share
Trading Symbol	TNC
Security Exchange Name	NYSE
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Public Float			$ 1,476,042,920
Entity Common Stock, Shares Outstanding		18,525,725
Auditor Name	Deloitte & Touche LLP
Auditor Location	Minneapolis, Minnesota
Auditor Firm ID	34
ICFR Auditor Attestation Flag	true
KPMG LLP [Member]
Document Information [Line Items]
Auditor Name	KPMG LLP
Auditor Location	Minneapolis, Minnesota
Auditor Firm ID	185