Income Attributable to Tennant Company Per Share - Schedule of Computations of Basic and Diluted Earnings per Share (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2025	Sep. 30, 2024
Numerator:
Net income	$ 14.9	$ 20.8	$ 48.2	$ 77.1
Denominator:
Basic - weighted average shares outstanding (in shares)	18,314,488	18,810,267	18,507,222	18,790,824
Effect of dilutive securities (in shares)	233,236	283,606	215,031	329,631
Diluted - weighted average shares outstanding (in shares)	18,547,724	19,093,873	18,722,253	19,120,455
Basic earnings per share (in dollars per share)	$ 0.81	$ 1.11	$ 2.60	$ 4.10
Diluted earnings per share (in dollars per share)	$ 0.80	$ 1.09	$ 2.57	$ 4.03