Consolidated Statements of Comprehensive Income - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Statement of Comprehensive Income [Abstract]
Net Earnings (Loss) Including Noncontrolling Interest	$ 45.9	$ 33.5	$ (6.2)
Other Comprehensive (Loss) Income:
Foreign currency translation adjustments	(4.5)	(16.2)	28.3
Pension and retiree medical benefits	(0.5)	1.7	5.9
Cash flow hedge	4.6	1.3	(7.7)
Income Taxes:
Foreign currency translation adjustments	0.1	0.2	0.3
Pension and retiree medical benefits	0.1	(0.5)	(2.1)
Cash flow hedge	(1.1)	(1.4)	2.9
Total Other Comprehensive (Loss) Income, net of tax	(1.3)	(14.9)	27.6
Total Comprehensive Income Including Noncontrolling Interest	44.6	18.6	21.4
Comprehensive Income Attributable to Noncontrolling Interest	0.1	0.1	0.0
Comprehensive Income Attributable to Tennant Company	$ 44.5	$ 18.5	$ 21.4