CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2026	Mar. 31, 2025
Statement of Comprehensive Income [Abstract]
Net income	$ 0.2	$ 13.1
Other comprehensive (loss) income:
Foreign currency translation adjustments (net of related tax (expense) benefit of $(0.3) and $0.2, respectively)	(4.8)	15.5
Pension and postretirement medical benefits (net of related tax expense of $0 and $0, respectively)	0.0	(0.1)
Derivative financial instruments (net of related tax (expense) benefit of $(0.2) and $0.0, respectively)	0.7	(0.1)
Total other comprehensive (loss) income, net of tax	(4.1)	15.3
Total comprehensive (loss) income including noncontrolling interest	(3.9)	28.4
Foreign currency translation adjustments attributable to noncontrolling interest	0.0	0.4
Comprehensive (loss) income attributable to Tennant Company	$ (3.9)	$ 28.0