Cover Page - shares	3 Months Ended
	Mar. 31, 2020	Apr. 30, 2020
Cover page.
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Mar. 31, 2020
Document Transition Report	false
Entity File Number	1-16191
Entity Registrant Name	TENNANT COMPANY
Entity Central Index Key	0000097134
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	Q1
Amendment Flag	false
Entity Incorporation, State or Country Code	MN
Entity Tax Identification Number	41-0572550
Entity Address, Address Line One	701 North Lilac Drive
Entity Address, Address Line Two	P.O. Box 1452
Entity Address, City or Town	Minneapolis
Entity Address, State or Province	MN
Entity Address, Postal Zip Code	55440
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 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 Common Stock, Shares Outstanding		18,442,501