Consolidated Statements of Equity (Unaudited) - USD ($) $ in Millions	Total	Tennant Company Shareholders' Equity	Common Stock	Additional Paid-in Capital	Retained Earnings	Accumulated Other Comprehensive Loss	Noncontrolling Interest
Beginning balance (in shares) at Dec. 31, 2020			18,503,805
Beginning balance at Dec. 31, 2020	$ 406.1	$ 404.8	$ 6.9	$ 54.7	$ 363.3	$ (20.1)	$ 1.3
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	25.7	25.7			25.7
Other comprehensive (loss) income	(10.7)	(10.7)				(10.7)
Issue stock for directors, employee benefit and stock plans, net of related tax withholdings and repurchases (in shares)			102,681
Issue stock for directors, employee benefit and stock plans, net of related tax withholdings of 3,305 shares	1.4	1.4	$ 0.1	1.3
Share-based compensation	3.1	3.1		3.1
Dividends paid per common share	(4.2)	(4.2)			(4.2)
Ending balance (in shares) at Mar. 31, 2021			18,606,486
Ending balance at Mar. 31, 2021	421.4	420.1	$ 7.0	59.1	384.8	(30.8)	1.3
Beginning balance (in shares) at Dec. 31, 2020			18,503,805
Beginning balance at Dec. 31, 2020	406.1	404.8	$ 6.9	54.7	363.3	(20.1)	1.3
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	57.0
Ending balance (in shares) at Sep. 30, 2021			18,583,237
Ending balance at Sep. 30, 2021	443.1	441.8	$ 7.0	60.8	407.4	(33.4)	1.3
Beginning balance (in shares) at Mar. 31, 2021			18,606,486
Beginning balance at Mar. 31, 2021	421.4	420.1	$ 7.0	59.1	384.8	(30.8)	1.3
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	9.8	9.8			9.8
Other comprehensive (loss) income	4.9	4.9				4.9
Issue stock for directors, employee benefit and stock plans, net of related tax withholdings and repurchases (in shares)			58,579
Issue stock for directors, employee benefit and stock plans, net of related tax withholdings of 3,305 shares	1.9	1.9		1.9
Share-based compensation	3.9	3.9		3.9
Dividends paid per common share	(4.4)	(4.4)			(4.4)
Ending balance (in shares) at Jun. 30, 2021			18,665,065
Ending balance at Jun. 30, 2021	437.5	436.2	$ 7.0	64.9	390.2	(25.9)	1.3
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	21.5	21.5			21.5
Other comprehensive (loss) income	(7.5)	(7.5)				(7.5)
Issue stock for directors, employee benefit and stock plans, net of related tax withholdings and repurchases (in shares)			20,401
Issue stock for directors, employee benefit and stock plans, net of related tax withholdings of 3,305 shares	0.9	0.9		0.9
Share-based compensation	2.5	2.5		2.5
Dividends paid per common share	(4.3)	(4.3)			(4.3)
Repurchases of common stock (in shares)			(102,229)
Repurchases of common stock	(7.5)	(7.5)		(7.5)
Ending balance (in shares) at Sep. 30, 2021			18,583,237
Ending balance at Sep. 30, 2021	$ 443.1	441.8	$ 7.0	60.8	407.4	(33.4)	1.3
Beginning balance (in shares) at Dec. 31, 2021	18,535,116		18,535,116
Beginning balance at Dec. 31, 2021	$ 435.1	433.8	$ 7.0	54.1	410.6	(37.9)	1.3
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	10.3	10.3			10.3
Other comprehensive (loss) income	(4.0)	(4.0)				(4.0)
Issue stock for directors, employee benefit and stock plans, net of related tax withholdings and repurchases (in shares)			44,700
Issue stock for directors, employee benefit and stock plans, net of related tax withholdings of 3,305 shares	(1.3)	(1.3)		(1.3)
Share-based compensation	1.8	1.8		1.8
Dividends paid per common share	(4.6)	(4.6)			(4.6)
Ending balance (in shares) at Mar. 31, 2022			18,579,816
Ending balance at Mar. 31, 2022	$ 437.3	436.0	$ 7.0	54.6	416.3	(41.9)	1.3
Beginning balance (in shares) at Dec. 31, 2021	18,535,116		18,535,116
Beginning balance at Dec. 31, 2021	$ 435.1	433.8	$ 7.0	54.1	410.6	(37.9)	1.3
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	$ 42.5
Ending balance (in shares) at Sep. 30, 2022	18,596,389		18,596,389
Ending balance at Sep. 30, 2022	$ 426.5	425.2	$ 7.0	57.3	439.1	(78.2)	1.3
Beginning balance (in shares) at Mar. 31, 2022			18,579,816
Beginning balance at Mar. 31, 2022	437.3	436.0	$ 7.0	54.6	416.3	(41.9)	1.3
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	16.6	16.6			16.6
Other comprehensive (loss) income	(16.1)	(16.1)				(16.1)
Issue stock for directors, employee benefit and stock plans, net of related tax withholdings and repurchases (in shares)			9,859
Issue stock for directors, employee benefit and stock plans, net of related tax withholdings of 3,305 shares	(0.1)	(0.1)		(0.1)
Share-based compensation	0.9	0.9		0.9
Dividends paid per common share	(4.6)	(4.6)			(4.6)
Ending balance (in shares) at Jun. 30, 2022			18,589,675
Ending balance at Jun. 30, 2022	434.0	432.7	$ 7.0	55.4	428.3	(58.0)	1.3
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	15.6	15.6			15.6
Other comprehensive (loss) income	(20.2)	(20.2)				(20.2)
Issue stock for directors, employee benefit and stock plans, net of related tax withholdings and repurchases (in shares)			6,714
Issue stock for directors, employee benefit and stock plans, net of related tax withholdings of 3,305 shares	0.2	0.2		0.2
Share-based compensation	1.7	1.7		1.7
Dividends paid per common share	$ (4.8)	(4.8)			(4.8)
Ending balance (in shares) at Sep. 30, 2022	18,596,389		18,596,389
Ending balance at Sep. 30, 2022	$ 426.5	$ 425.2	$ 7.0	$ 57.3	$ 439.1	$ (78.2)	$ 1.3