Separate Financial Information of Guarantor Subsidiaries Condensed Consolidated Statements of Operations (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Revenues	$ 262.5	$ 272.8
Cost of Sales	154.3	163.7
Gross Profit	108.2	109.1
Operating Expense:
Research and Development Expense	7.2	8.0
Selling and Administrative Expense	90.2	90.7
Total Operating Expense	97.4	98.7
Profit from Operations	10.8	10.4
Other Income (Expense):
Equity in Earnings of Affiliates	0.0	0.0
Interest (Expense) Income, Net	(4.2)	(5.0)
Intercompany Interest Income (Expense)	0.0	0.0
Net Foreign Currency Transaction Gain (Loss)	0.2	(0.7)
Other Expense, Net	(0.2)	(0.3)
Total Other Expense, Net	(4.2)	(6.0)
Profit Before Income Taxes	6.6	4.4
Income Tax Expense	1.2	1.1
Net Earnings Including Noncontrolling Interest	5.4	3.3
Net Earnings Attributable to Tennant Company	5.4	3.3
Eliminations
Revenues	(135.7)	(129.7)
Cost of Sales	(134.0)	(128.4)
Gross Profit	(1.7)	(1.3)
Operating Expense:
Research and Development Expense	0.0	0.0
Selling and Administrative Expense	0.0	0.0
Total Operating Expense	0.0	0.0
Profit from Operations	(1.7)	(1.3)
Other Income (Expense):
Equity in Earnings of Affiliates	(2.5)	(7.5)
Interest (Expense) Income, Net	0.0	0.0
Intercompany Interest Income (Expense)	0.0	0.0
Net Foreign Currency Transaction Gain (Loss)	0.0	0.0
Other Expense, Net	0.0	0.0
Total Other Expense, Net	(2.5)	(7.5)
Profit Before Income Taxes	(4.2)	(8.8)
Income Tax Expense	(2.1)	(2.5)
Net Earnings Including Noncontrolling Interest	(2.1)	(6.3)
Net Earnings Attributable to Tennant Company	(2.1)	(6.3)
Parent
Revenues	116.5	113.7
Cost of Sales	76.5	77.2
Gross Profit	40.0	36.5
Operating Expense:
Research and Development Expense	5.6	6.1
Selling and Administrative Expense	27.2	29.1
Total Operating Expense	32.8	35.2
Profit from Operations	7.2	1.3
Other Income (Expense):
Equity in Earnings of Affiliates	0.3	4.4
Interest (Expense) Income, Net	(4.2)	(5.1)
Intercompany Interest Income (Expense)	3.5	3.7
Net Foreign Currency Transaction Gain (Loss)	0.0	0.4
Other Expense, Net	(0.2)	(0.3)
Total Other Expense, Net	(0.6)	3.1
Profit Before Income Taxes	6.6	4.4
Income Tax Expense	1.2	1.1
Net Earnings Including Noncontrolling Interest	5.4	3.3
Net Earnings Attributable to Tennant Company	5.4	3.3
Guarantor Subsidiaries
Revenues	148.4	148.4
Cost of Sales	123.0	123.1
Gross Profit	25.4	25.3
Operating Expense:
Research and Development Expense	0.2	0.2
Selling and Administrative Expense	19.0	19.7
Total Operating Expense	19.2	19.9
Profit from Operations	6.2	5.4
Other Income (Expense):
Equity in Earnings of Affiliates	0.8	0.5
Interest (Expense) Income, Net	0.0	0.0
Intercompany Interest Income (Expense)	(1.4)	(1.4)
Net Foreign Currency Transaction Gain (Loss)	0.0	0.0
Other Expense, Net	(0.4)	(0.6)
Total Other Expense, Net	(1.0)	(1.5)
Profit Before Income Taxes	5.2	3.9
Income Tax Expense	1.1	0.9
Net Earnings Including Noncontrolling Interest	4.1	3.0
Net Earnings Attributable to Tennant Company	4.1	3.0
Non-Guarantor Subsidiaries
Revenues	133.3	140.4
Cost of Sales	88.8	91.8
Gross Profit	44.5	48.6
Operating Expense:
Research and Development Expense	1.4	1.7
Selling and Administrative Expense	44.0	41.9
Total Operating Expense	45.4	43.6
Profit from Operations	(0.9)	5.0
Other Income (Expense):
Equity in Earnings of Affiliates	1.4	2.6
Interest (Expense) Income, Net	0.0	0.1
Intercompany Interest Income (Expense)	(2.1)	(2.3)
Net Foreign Currency Transaction Gain (Loss)	0.2	(1.1)
Other Expense, Net	0.4	0.6
Total Other Expense, Net	(0.1)	(0.1)
Profit Before Income Taxes	(1.0)	4.9
Income Tax Expense	1.0	1.6
Net Earnings Including Noncontrolling Interest	(2.0)	3.3
Net Earnings Attributable to Tennant Company	$ (2.0)	$ 3.3