CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2025	Sep. 30, 2024
Statement of Comprehensive Income [Abstract]
Net income	$ 14.9	$ 20.8	$ 48.2	$ 77.1
Other comprehensive income (loss):
Foreign currency translation adjustments (net of related tax benefit of $0.0, $0.5, $1.9 and $0.4, respectively)	(0.7)	12.9	38.6	(2.4)
Pension and postretirement medical benefits (net of related tax expense of $0, $0, $0 and $0, respectively)	0.0	(0.2)	0.0	(0.2)
Derivative financial instruments (net of related tax (expense) benefit of $(0.1), $0.5, $0.0 and $0.1, respectively)	0.2	(1.7)	0.0	(0.4)
Total other comprehensive (loss) income, net of tax	(0.5)	11.0	38.6	(3.0)
Total comprehensive income including noncontrolling interest	14.4	31.8	86.8	74.1
Foreign currency translation adjustments attributable to noncontrolling interest	0.0	0.0	0.5	0.0
Comprehensive income attributable to Tennant Company	$ 14.4	$ 31.8	$ 86.3	$ 74.1