Earnings Attributable to Tennant Company Per Share (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended	6 Months Ended
Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Numerator:
Net Earnings Attributable to Tennant Company	$ 14.3	$ 14.8	$ 19.5	$ 20.2
Denominator:
Basic - Weighted Average Shares Outstanding	18,347,189	18,082,492	18,317,003	18,062,591
Effect of dilutive securities:
Share-based compensation plans	237,504	312,373	297,524	304,793
Diluted - Weighted Average Shares Outstanding	18,584,693	18,394,865	18,614,527	18,367,384
Basic Earnings (Loss) per Share	$ 0.78	$ 0.82	$ 1.06	$ 1.12
Diluted Earnings (Loss) per Share	$ 0.77	$ 0.81	$ 1.05	$ 1.10
Anti-dilutive securities excluded from earnings per share calculation	818,912	688,545	532,564	664,311

Securities (including those issuable pursuant to contingent stock agreements) that could potentially dilute basic earnings per share (EPS) or earnings per unit (EPU) in the future that were not included in the computation of diluted EPS or EPU because to do so would increase EPS or EPU amounts or decrease loss per share or unit amounts for the period presented.

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