Separate Financial Information of Guarantor Subsidiaries Condensed Consolidated Balance Sheets (Details) - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019	Mar. 31, 2019	Dec. 31, 2018
Current Assets:
Cash, Cash Equivalents and Restricted Cash	$ 192.1	$ 74.6	$ 46.9	$ 86.1
Net Receivables	207.1	223.3
Intercompany Receivables	0.0	0.0
Inventories	155.2	150.1
Prepaid and Other Current Assets	30.8	33.0
Total Current Assets	585.2	481.0
Property, Plant and Equipment	416.0	412.5
Accumulated Depreciation	(242.1)	(239.2)
Property, Plant and Equipment, Net	173.9	173.3
Operating lease assets	42.8	46.6
Investment in Affiliates	0.0	0.0
Intercompany Loans	0.0	0.0
Goodwill	191.2	195.1
Intangible Assets, Net	129.6	137.7
Other Assets	27.5	29.2
Total Assets	1,150.2	1,062.9
Current Liabilities:
Current Portion of Long-Term Debt	1.1	31.3
Accounts Payable	95.8	94.1
Intercompany Payables	0.0	0.0
Employee Compensation and Benefits	40.2	63.5
Other Current Liabilities	88.0	86.0
Total Current Liabilities	225.1	274.9
Long-Term Liabilities:
Long-Term Debt	462.5	307.5
Intercompany Loans	0.0	0.0
Long-Term Operating Lease Liabilities	27.3	30.3
Employee-Related Benefits	18.6	19.4
Deferred Income Taxes	39.8	41.7
Other Liabilities	18.2	27.8
Total Long-Term Liabilities	566.4	426.7
Total Liabilities	791.5	701.6
Common Stock	6.9	6.9
Additional Paid-In Capital	49.4	45.5
Retained Earnings	347.1	346.0
Accumulated Other Comprehensive Loss	(46.1)	(38.5)
Total Tennant Company Shareholders' Equity	357.3	359.9
Noncontrolling Interest	1.4	1.4
Total Equity	358.7	361.3	320.2	316.3
Total Liabilities and Total Equity	1,150.2	1,062.9
Eliminations
Current Assets:
Cash, Cash Equivalents and Restricted Cash	0.0	0.0	0.0	0.0
Net Receivables	0.0	0.0
Intercompany Receivables	(153.5)	(173.4)
Inventories	(12.7)	(12.8)
Prepaid and Other Current Assets	0.2	0.0
Total Current Assets	(166.0)	(186.2)
Property, Plant and Equipment	0.0	0.0
Accumulated Depreciation	0.0	0.0
Property, Plant and Equipment, Net	0.0	0.0
Operating lease assets	0.0	0.0
Investment in Affiliates	(438.7)	(474.0)
Intercompany Loans	(295.5)	(298.2)
Goodwill	0.0	0.0
Intangible Assets, Net	0.0	0.0
Other Assets	0.0	0.0
Total Assets	(900.2)	(958.4)
Current Liabilities:
Current Portion of Long-Term Debt	0.0	0.0
Accounts Payable	0.0	0.0
Intercompany Payables	(153.5)	(173.4)
Employee Compensation and Benefits	0.0	0.0
Other Current Liabilities	0.2	0.0
Total Current Liabilities	(153.3)	(173.4)
Long-Term Liabilities:
Long-Term Debt	0.0	0.0
Intercompany Loans	(295.4)	(298.2)
Long-Term Operating Lease Liabilities	0.0	0.0
Employee-Related Benefits	0.0	0.0
Deferred Income Taxes	0.0	0.0
Other Liabilities	0.0	0.0
Total Long-Term Liabilities	(295.4)	(298.2)
Total Liabilities	(448.7)	(471.6)
Common Stock	(11.1)	(11.1)
Additional Paid-In Capital	(495.0)	(495.0)
Retained Earnings	(29.3)	(44.4)
Accumulated Other Comprehensive Loss	85.3	65.1
Total Tennant Company Shareholders' Equity	(450.1)	(485.4)
Noncontrolling Interest	(1.4)	(1.4)
Total Equity	(451.5)	(486.8)
Total Liabilities and Total Equity	(900.2)	(958.4)
Parent
Current Assets:
Cash, Cash Equivalents and Restricted Cash	150.3	27.7	9.8	24.8
Net Receivables	1.4	3.3
Intercompany Receivables	36.1	35.7
Inventories	38.5	39.1
Prepaid and Other Current Assets	14.7	17.8
Total Current Assets	241.0	123.6
Property, Plant and Equipment	252.1	246.7
Accumulated Depreciation	(167.3)	(164.3)
Property, Plant and Equipment, Net	84.8	82.4
Operating lease assets	4.9	5.2
Investment in Affiliates	393.3	420.7
Intercompany Loans	295.5	298.2
Goodwill	12.9	12.9
Intangible Assets, Net	3.0	3.2
Other Assets	4.9	4.9
Total Assets	1,040.3	951.1
Current Liabilities:
Current Portion of Long-Term Debt	0.0	30.0
Accounts Payable	40.0	39.4
Intercompany Payables	115.5	137.5
Employee Compensation and Benefits	9.6	19.3
Other Current Liabilities	29.4	24.9
Total Current Liabilities	194.5	251.1
Long-Term Liabilities:
Long-Term Debt	461.4	306.2
Intercompany Loans	2.9	2.1
Long-Term Operating Lease Liabilities	3.6	4.0
Employee-Related Benefits	10.1	10.4
Deferred Income Taxes	0.0	0.0
Other Liabilities	9.1	16.0
Total Long-Term Liabilities	487.1	338.7
Total Liabilities	681.6	589.8
Common Stock	6.9	6.9
Additional Paid-In Capital	49.4	45.5
Retained Earnings	347.1	346.0
Accumulated Other Comprehensive Loss	(46.1)	(38.5)
Total Tennant Company Shareholders' Equity	357.3	359.9
Noncontrolling Interest	1.4	1.4
Total Equity	358.7	361.3
Total Liabilities and Total Equity	1,040.3	951.1
Guarantor Subsidiaries
Current Assets:
Cash, Cash Equivalents and Restricted Cash	1.0	1.3	1.1	1.6
Net Receivables	95.5	99.7
Intercompany Receivables	117.4	137.7
Inventories	18.0	16.9
Prepaid and Other Current Assets	0.9	1.2
Total Current Assets	232.8	256.8
Property, Plant and Equipment	10.1	10.0
Accumulated Depreciation	(4.4)	(4.2)
Property, Plant and Equipment, Net	5.7	5.8
Operating lease assets	10.2	10.3
Investment in Affiliates	14.3	14.1
Intercompany Loans	0.0	0.0
Goodwill	1.7	1.7
Intangible Assets, Net	2.4	2.5
Other Assets	5.0	4.4
Total Assets	272.1	295.6
Current Liabilities:
Current Portion of Long-Term Debt	0.0	0.0
Accounts Payable	5.8	5.1
Intercompany Payables	0.0	0.0
Employee Compensation and Benefits	7.9	17.5
Other Current Liabilities	17.7	20.5
Total Current Liabilities	31.4	43.1
Long-Term Liabilities:
Long-Term Debt	0.0	0.0
Intercompany Loans	128.0	128.0
Long-Term Operating Lease Liabilities	5.2	5.3
Employee-Related Benefits	1.5	1.4
Deferred Income Taxes	0.0	0.0
Other Liabilities	2.9	3.0
Total Long-Term Liabilities	137.6	137.7
Total Liabilities	169.0	180.8
Common Stock	0.0	0.0
Additional Paid-In Capital	77.6	77.6
Retained Earnings	26.9	38.4
Accumulated Other Comprehensive Loss	(1.4)	(1.2)
Total Tennant Company Shareholders' Equity	103.1	114.8
Noncontrolling Interest	0.0	0.0
Total Equity	103.1	114.8
Total Liabilities and Total Equity	272.1	295.6
Non-Guarantor Subsidiaries
Current Assets:
Cash, Cash Equivalents and Restricted Cash	40.8	45.6	$ 36.0	$ 59.7
Net Receivables	110.2	120.3
Intercompany Receivables	0.0	0.0
Inventories	111.4	106.9
Prepaid and Other Current Assets	15.0	14.0
Total Current Assets	277.4	286.8
Property, Plant and Equipment	153.8	155.8
Accumulated Depreciation	(70.4)	(70.7)
Property, Plant and Equipment, Net	83.4	85.1
Operating lease assets	27.7	31.1
Investment in Affiliates	31.1	39.2
Intercompany Loans	0.0	0.0
Goodwill	176.6	180.5
Intangible Assets, Net	124.2	132.0
Other Assets	17.6	19.9
Total Assets	738.0	774.6
Current Liabilities:
Current Portion of Long-Term Debt	1.1	1.3
Accounts Payable	50.0	49.6
Intercompany Payables	38.0	35.9
Employee Compensation and Benefits	22.7	26.7
Other Current Liabilities	40.7	40.6
Total Current Liabilities	152.5	154.1
Long-Term Liabilities:
Long-Term Debt	1.1	1.3
Intercompany Loans	164.5	168.1
Long-Term Operating Lease Liabilities	18.5	21.0
Employee-Related Benefits	7.0	7.6
Deferred Income Taxes	39.8	41.7
Other Liabilities	6.2	8.8
Total Long-Term Liabilities	237.1	248.5
Total Liabilities	389.6	402.6
Common Stock	11.1	11.1
Additional Paid-In Capital	417.4	417.4
Retained Earnings	2.4	6.0
Accumulated Other Comprehensive Loss	(83.9)	(63.9)
Total Tennant Company Shareholders' Equity	347.0	370.6
Noncontrolling Interest	1.4	1.4
Total Equity	348.4	372.0
Total Liabilities and Total Equity	$ 738.0	$ 774.6