Consolidated Statements of Comprehensive Income - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Statement of Comprehensive Income [Abstract]
Net income	$ 43.8	$ 83.7	$ 109.5
Other comprehensive income (loss):
Foreign currency translation adjustments (net of related tax benefit (expense) of $1.8, $(0.2), and $0.8, respectively)	41.3	(29.6)	8.3
Pension and postretirement medical benefits (net of related tax benefit (expense) of $0.5, $0.3, and $(0.3), respectively)	(1.7)	(0.9)	1.0
Derivative financial instruments (net of tax (expense) benefit of $(0.1), $0.0, and $0.4, respectively)	0.4	(0.1)	(1.4)
Unrealized (loss) gain on debt securities (net of tax benefit of $0.1, $0.1, and $0.0, respectively)	(0.5)	0.2	0.0
Total other comprehensive income (loss), net of tax	39.5	(30.4)	7.9
Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest	83.3	53.3	117.4
Comprehensive Income (Loss), Net of Tax, Attributable to Noncontrolling Interest	0.5	0.0	0.0
Comprehensive income attributable to Tennant Company	$ 82.8	$ 53.3	$ 117.4