Earnings Attributable to Tennant Company Per Share (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Numerator:
Net Earnings Attributable to Tennant Company	$ 14.8	$ 12.7	$ 20.2	$ 16.0
Denominator:
Basic - Weighted Average Shares Outstanding	18,082,492	17,943,450	18,062,591	17,867,641
Effect of dilutive securities:
Share-based compensation plans	312,373	428,088	304,793	436,319
Diluted - Weighted Average Shares Outstanding	18,394,865	18,371,538	18,367,384	18,303,960
Basic Earnings (Loss) per Share	$ 0.82	$ 0.71	$ 1.12	$ 0.90
Diluted Earnings (Loss) per Share	$ 0.81	$ 0.69	$ 1.10	$ 0.88
Anti-dilutive securities excluded from earnings per share calculation	688,545	186,833	664,311	311,907