Separate Financial Information of Guarantor Subsidiaries Balance Sheets (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Current Assets:
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents	$ 74.6	$ 86.1	$ 59.0	$ 58.5
Restricted Cash	0.5
Net Receivables	223.3	216.2
Intercompany Receivables	0.0	0.0
Inventories	150.1	135.1
Prepaid Expense and Other Assets, Current	33.0	31.2
Total Current Assets	481.0	468.6
Property, Plant and Equipment	412.5	386.6
Accumulated Depreciation	(239.2)	(223.2)
Property, Plant and Equipment, Net	173.3	163.4
Operating Lease Assets	46.6	0.0
Investment in Affiliates	0.0	0.0
Intercompany Loans	0.0	0.0
Goodwill	195.1	182.7	186.0
Intangible Assets, Net	137.7	146.5
Deferred Income Taxes and Other Assets, Noncurrent	29.2	31.3
Total Assets	1,062.9	992.5
Current Liabilities:
Current Portion of Long-Term Debt	31.3	27.0
Accounts Payable	94.1	98.4
Intercompany Payables	0.0	0.0
Employee Compensation and Benefits	63.5	56.1
Other Current Liabilities	86.0	67.4
Total Current Liabilities	274.9	248.9
Long-Term Liabilities:
Long-Term Debt	307.5	328.1
Intercompany Loans	0.0	0.0
Long-Term Operating Lease Liability	30.3	0.0
Employee-Related Benefits	19.4	21.1
Deferred Income Taxes	41.7	46.0
Other Liabilities	27.8	32.1
Total Long-Term Liabilities	426.7	427.3
Total Liabilities	701.6	676.2
Common Stock	6.9	6.8
Additional Paid-In Capital	45.5	28.5
Retained Earnings	346.0	316.3
Accumulated Other Comprehensive Loss	(38.5)	(37.2)	(22.3)
Total Tennant Company Shareholders’ Equity	359.9	314.4
Noncontrolling Interest	1.4	1.9
Total Equity	361.3	316.3	298.5	278.5
Total Liabilities and Total Equity	1,062.9	992.5
Parent Company
Current Assets:
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents	27.7	24.8	18.4	38.4
Net Receivables	3.3	0.9
Intercompany Receivables	35.7	30.0
Inventories	39.1	37.1
Prepaid Expense and Other Assets, Current	17.8	17.5
Total Current Assets	123.6	110.3
Property, Plant and Equipment	246.7	229.8
Accumulated Depreciation	(164.3)	(159.4)
Property, Plant and Equipment, Net	82.4	70.4
Operating Lease Assets	5.2
Investment in Affiliates	420.7	421.0
Intercompany Loans	298.2	301.6
Goodwill	12.9	12.9
Intangible Assets, Net	3.2	4.0
Deferred Income Taxes and Other Assets, Noncurrent	4.9	11.0
Total Assets	951.1	931.2
Current Liabilities:
Current Portion of Long-Term Debt	30.0	21.8
Accounts Payable	39.4	41.0
Intercompany Payables	137.5	149.5
Employee Compensation and Benefits	19.3	14.4
Other Current Liabilities	24.9	22.8
Total Current Liabilities	251.1	249.5
Long-Term Liabilities:
Long-Term Debt	306.2	326.5
Intercompany Loans	2.1	3.3
Long-Term Operating Lease Liability	4.0
Employee-Related Benefits	10.4	11.0
Deferred Income Taxes	0.0	0.0
Other Liabilities	16.0	24.6
Total Long-Term Liabilities	338.7	365.4
Total Liabilities	589.8	614.9
Common Stock	6.9	6.8
Additional Paid-In Capital	45.5	28.5
Retained Earnings	346.0	316.3
Accumulated Other Comprehensive Loss	(38.5)	(37.2)
Total Tennant Company Shareholders’ Equity	359.9	314.4
Noncontrolling Interest	1.4	1.9
Total Equity	361.3	316.3
Total Liabilities and Total Equity	951.1	931.2
Guarantor Subsidiaries
Current Assets:
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents	1.3	1.6	0.5	0.2
Net Receivables	99.7	94.8
Intercompany Receivables	137.7	148.9
Inventories	16.9	13.4
Prepaid Expense and Other Assets, Current	1.2	1.2
Total Current Assets	256.8	259.9
Property, Plant and Equipment	10.0	12.7
Accumulated Depreciation	(4.2)	(6.9)
Property, Plant and Equipment, Net	5.8	5.8
Operating Lease Assets	10.3
Investment in Affiliates	14.1	12.1
Intercompany Loans	0.0	0.0
Goodwill	1.7	1.7
Intangible Assets, Net	2.5	2.7
Deferred Income Taxes and Other Assets, Noncurrent	4.4	3.1
Total Assets	295.6	285.3
Current Liabilities:
Current Portion of Long-Term Debt	0.0	0.0
Accounts Payable	5.1	5.0
Intercompany Payables	0.0	0.0
Employee Compensation and Benefits	17.5	17.2
Other Current Liabilities	20.5	17.6
Total Current Liabilities	43.1	39.8
Long-Term Liabilities:
Long-Term Debt	0.0	0.0
Intercompany Loans	128.0	128.1
Long-Term Operating Lease Liability	5.3
Employee-Related Benefits	1.4	2.0
Deferred Income Taxes	0.0	0.0
Other Liabilities	3.0	2.9
Total Long-Term Liabilities	137.7	133.0
Total Liabilities	180.8	172.8
Common Stock	0.0	0.0
Additional Paid-In Capital	77.6	77.5
Retained Earnings	38.4	36.6
Accumulated Other Comprehensive Loss	(1.2)	(1.6)
Total Tennant Company Shareholders’ Equity	114.8	112.5
Noncontrolling Interest	0.0	0.0
Total Equity	114.8	112.5
Total Liabilities and Total Equity	295.6	285.3
Non-Guarantor Subsidiaries
Current Assets:
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents	45.6	59.7	40.1	19.9
Net Receivables	120.3	120.5
Intercompany Receivables	0.0	0.0
Inventories	106.9	94.7
Prepaid Expense and Other Assets, Current	14.0	13.0
Total Current Assets	286.8	287.9
Property, Plant and Equipment	155.8	144.1
Accumulated Depreciation	(70.7)	(56.9)
Property, Plant and Equipment, Net	85.1	87.2
Operating Lease Assets	31.1
Investment in Affiliates	39.2	20.8
Intercompany Loans	0.0	3.2
Goodwill	180.5	168.1
Intangible Assets, Net	132.0	139.8
Deferred Income Taxes and Other Assets, Noncurrent	19.9	17.2
Total Assets	774.6	724.2
Current Liabilities:
Current Portion of Long-Term Debt	1.3	5.2
Accounts Payable	49.6	52.4
Intercompany Payables	35.9	29.5
Employee Compensation and Benefits	26.7	24.5
Other Current Liabilities	40.6	27.5
Total Current Liabilities	154.1	139.1
Long-Term Liabilities:
Long-Term Debt	1.3	1.6
Intercompany Loans	168.1	173.5
Long-Term Operating Lease Liability	21.0
Employee-Related Benefits	7.6	8.1
Deferred Income Taxes	41.7	46.0
Other Liabilities	8.8	4.6
Total Long-Term Liabilities	248.5	233.8
Total Liabilities	402.6	372.9
Common Stock	11.1	11.1
Additional Paid-In Capital	417.4	399.5
Retained Earnings	6.0	(2.5)
Accumulated Other Comprehensive Loss	(63.9)	(58.7)
Total Tennant Company Shareholders’ Equity	370.6	349.4
Noncontrolling Interest	1.4	1.9
Total Equity	372.0	351.3
Total Liabilities and Total Equity	774.6	724.2
Eliminations
Current Assets:
Operating Lease Assets	0.0
Long-Term Liabilities:
Long-Term Operating Lease Liability	0.0
Eliminations
Current Assets:
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents	0.0	0.0	$ 0.0	$ 0.0
Net Receivables	0.0	0.0
Intercompany Receivables	(173.4)	(178.9)
Inventories	(12.8)	(10.1)
Prepaid Expense and Other Assets, Current	0.0	(0.5)
Total Current Assets	(186.2)	(189.5)
Property, Plant and Equipment	0.0	0.0
Accumulated Depreciation	0.0	0.0
Property, Plant and Equipment, Net	0.0	0.0
Investment in Affiliates	(474.0)	(453.9)
Intercompany Loans	(298.2)	(304.8)
Goodwill	0.0	0.0
Intangible Assets, Net	0.0	0.0
Deferred Income Taxes and Other Assets, Noncurrent	0.0	0.0
Total Assets	(958.4)	(948.2)
Current Liabilities:
Current Portion of Long-Term Debt	0.0	0.0
Accounts Payable	0.0	0.0
Intercompany Payables	(173.4)	(179.0)
Employee Compensation and Benefits	0.0	0.0
Other Current Liabilities	0.0	(0.5)
Total Current Liabilities	(173.4)	(179.5)
Long-Term Liabilities:
Long-Term Debt	0.0	0.0
Intercompany Loans	(298.2)	(304.9)
Employee-Related Benefits	0.0	0.0
Deferred Income Taxes	0.0	0.0
Other Liabilities	0.0	0.0
Total Long-Term Liabilities	(298.2)	(304.9)
Total Liabilities	(471.6)	(484.4)
Common Stock	(11.1)	(11.1)
Additional Paid-In Capital	(495.0)	(477.0)
Retained Earnings	(44.4)	(34.1)
Accumulated Other Comprehensive Loss	65.1	60.3
Total Tennant Company Shareholders’ Equity	(485.4)	(461.9)
Noncontrolling Interest	(1.4)	(1.9)
Total Equity	(486.8)	(463.8)
Total Liabilities and Total Equity	$ (958.4)	$ (948.2)