Earnings Attributable to Tennant Company Per Share (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended
Mar. 31, 2019	Mar. 31, 2018
Numerator:
Net Earnings Attributable to Tennant Company	$ 5.4	$ 3.3
Denominator:
Basic - Weighted Average Shares Outstanding	18,042,468	17,790,989
Effect of dilutive securities:
Share-based compensation plans	302,743	454,370
Diluted - Weighted Average Shares Outstanding	18,345,211	18,245,359
Basic Earnings (Loss) per Share	$ 0.30	$ 0.18
Diluted Earnings (Loss) per Share	$ 0.29	$ 0.18
Anti-dilutive securities excluded from earnings per share calculation	646,491	291,622

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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