Earnings Attributable to Tennant Company Per Share (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Numerator:
Net Earnings Attributable to Tennant Company	$ 14.6	$ 9.7	$ 34.8	$ 25.7
Denominator:
Basic - Weighted Average Shares Outstanding	18,134,909	17,998,917	18,086,962	17,911,880
Effect of dilutive securities:
Share-based compensation plans	353,039	440,704	315,967	432,933
Diluted - Weighted Average Shares Outstanding	18,487,948	18,439,621	18,402,929	18,344,813
Basic Earnings (Loss) per Share	$ 0.81	$ 0.54	$ 1.93	$ 1.43
Diluted Earnings (Loss) per Share	$ 0.79	$ 0.52	$ 1.89	$ 1.40
Anti-dilutive securities excluded from earnings per share calculation	485,853	139,106	687,972	214,605