Derivatives - Schedule of Effect of Derivative Instruments on Consolidated Statements of Earnings (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2025	Sep. 30, 2024
Foreign Currency Fair Value Hedge Derivative [Line Items]
Net foreign currency transaction (loss) gain	$ 0.0	$ (0.4)	$ (1.0)	$ 0.1
Net gain (loss) recognized in other comprehensive (loss) income, net of tax	0.2	(1.7)	0.0	(0.4)
Derivatives designated as cash flow hedges: \| Derivatives designated as cash flow hedges:
Foreign Currency Fair Value Hedge Derivative [Line Items]
Interest expense, net	(2.4)	(2.7)	(6.9)	(7.5)
Net foreign currency transaction (loss) gain	0.0	(0.4)	(1.0)	0.1
Derivatives designated as cash flow hedges: \| Derivatives designated as cash flow hedges: \| Interest expense, net
Foreign Currency Fair Value Hedge Derivative [Line Items]
Gain (Loss) on Hedging	0.1	0.3	0.2	0.9
Derivatives designated as cash flow hedges: \| Derivatives designated as cash flow hedges: \| Net foreign currency transaction (loss) gain
Foreign Currency Fair Value Hedge Derivative [Line Items]
Gain (Loss) on Hedging	0.0	0.0	0.0	0.0
Derivatives designated as cash flow hedges: \| Derivatives designated as cash flow hedges: \| Foreign Exchange Option
Foreign Currency Fair Value Hedge Derivative [Line Items]
Net gain (loss) recognized in other comprehensive (loss) income, net of tax	0.1	(1.7)	(0.3)	0.4
Net gain reclassified from accumulated other comprehensive income (loss) into income, net of tax, effective portion to interest expense, net	0.1	0.3	0.2	0.9
Derivatives designated as cash flow hedges: \| Derivatives designated as fair value hedges:
Foreign Currency Fair Value Hedge Derivative [Line Items]
Interest expense, net	(2.4)	(2.7)	(6.9)	(7.5)
Net foreign currency transaction (loss) gain	0.0	(0.4)	(1.0)	0.1
Derivatives designated as cash flow hedges: \| Derivatives designated as fair value hedges: \| Interest expense, net
Foreign Currency Fair Value Hedge Derivative [Line Items]
Gain (Loss) on Hedging	0.3	0.2	0.8	0.8
Derivatives designated as cash flow hedges: \| Derivatives designated as fair value hedges: \| Net foreign currency transaction (loss) gain
Foreign Currency Fair Value Hedge Derivative [Line Items]
Gain (Loss) on Hedging	0.4	(2.5)	(7.9)	(0.6)
Derivatives designated as cash flow hedges: \| Derivatives designated as fair value hedges: \| Foreign Exchange Option
Foreign Currency Fair Value Hedge Derivative [Line Items]
Net gain (loss) recognized in other comprehensive (loss) income, net of tax	3.1	0.6	1.2	0.9
Net gain reclassified from accumulated other comprehensive income (loss) into income, net of tax, effective portion to interest expense, net	2.9	0.3	0.7	0.8
Derivatives designated as cash flow hedges: \| Derivatives designated as net investment hedges:
Foreign Currency Fair Value Hedge Derivative [Line Items]
Interest expense, net	(2.4)	(2.7)	(6.9)	(7.5)
Derivatives designated as cash flow hedges: \| Derivatives designated as net investment hedges: \| Interest expense, net
Foreign Currency Fair Value Hedge Derivative [Line Items]
Gain (Loss) on Hedging	0.2	0.2	0.7	0.7
Derivatives designated as cash flow hedges: \| Derivatives designated as net investment hedges: \| Foreign Exchange Option
Foreign Currency Fair Value Hedge Derivative [Line Items]
Net gain (loss) recognized in other comprehensive (loss) income, net of tax	(2.1)	(1.8)	(6.3)	0.2
Net gain reclassified from accumulated other comprehensive income (loss) into income, net of tax, effective portion to interest expense, net	(2.5)	0.2	0.7	0.7
Derivatives not designated as hedging instruments: \| Foreign Exchange Option
Foreign Currency Fair Value Hedge Derivative [Line Items]
Net gain recognized in income	$ (0.2)	$ (1.9)	$ (8.3)	$ 1.0

TENNANT CO 10-Q