Separate Financial Information of Guarantor Subsidiaries Condensed Consolidated Balance Sheets (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Current Assets:
Cash and Cash Equivalents	$ 53,901	$ 58,398
Restricted Cash	543	653
Net Receivables	215,323	209,516
Intercompany Receivables	0	0
Inventories	139,406	127,694
Prepaid Expenses	27,382	19,351
Other Current Assets	8,707	7,503
Total Current Assets	445,262	423,115
Property, Plant and Equipment	381,607	382,768
Accumulated Depreciation	(212,625)	(202,750)
Property, Plant and Equipment, Net	168,982	180,018
Deferred Income Taxes	13,721	11,134
Investment in Affiliates	0	0
Intercompany Loans	0	0
Goodwill	185,715	186,044
Intangible Assets, Net	157,674	172,347
Other Assets	14,730	21,319
Total Assets	986,084	993,977
Current Liabilities:
Current Portion of Long-Term Debt	30,969	30,883
Accounts Payable	103,602	96,082
Intercompany Payables	0	0
Employee Compensation and Benefits	41,289	37,257
Income Taxes Payable	2,809	2,838
Other Current Liabilities	66,753	69,447
Total Current Liabilities	245,422	236,507
Long-Term Liabilities:
Long-Term Debt	328,699	345,956
Intercompany Loans	0	0
Employee-Related Benefits	22,583	23,867
Deferred Income Taxes	50,444	53,225
Other Liabilities	36,739	35,948
Total Long-Term Liabilities	438,465	458,996
Total Liabilities	683,887	695,503
Common Stock	6,778	6,705
Additional Paid-In Capital	22,273	15,089
Retained Earnings	306,667	297,032
Accumulated Other Comprehensive Loss	(35,391)	(22,323)
Total Tennant Company Shareholders' Equity	300,327	296,503
Noncontrolling Interest	1,870	1,971
Total Equity	302,197	298,474
Total Liabilities and Total Equity	986,084	993,977
Eliminations
Current Assets:
Cash and Cash Equivalents	0	0
Restricted Cash	0	0
Net Receivables	0	0
Intercompany Receivables	(172,830)	(187,222)
Inventories	(10,210)	(8,993)
Prepaid Expenses	0	0
Other Current Assets	0	0
Total Current Assets	(183,040)	(196,215)
Property, Plant and Equipment	0	0
Accumulated Depreciation	0	0
Property, Plant and Equipment, Net	0	0
Deferred Income Taxes	0	0
Investment in Affiliates	(428,611)	(424,570)
Intercompany Loans	(308,120)	(309,805)
Goodwill	0	0
Intangible Assets, Net	0	0
Other Assets	0	0
Total Assets	(919,771)	(930,590)
Current Liabilities:
Current Portion of Long-Term Debt	0	0
Accounts Payable	0	0
Intercompany Payables	(172,830)	(187,222)
Employee Compensation and Benefits	0	0
Income Taxes Payable	0	0
Other Current Liabilities	0	0
Total Current Liabilities	(172,830)	(187,222)
Long-Term Liabilities:
Long-Term Debt	0	0
Intercompany Loans	(308,120)	(309,805)
Employee-Related Benefits	0	0
Deferred Income Taxes	0	0
Other Liabilities	0	0
Total Long-Term Liabilities	(308,120)	(309,805)
Total Liabilities	(480,950)	(497,027)
Common Stock	(11,131)	(11,131)
Additional Paid-In Capital	(462,011)	(456,943)
Retained Earnings	(19,535)	(2,578)
Accumulated Other Comprehensive Loss	55,726	39,060
Total Tennant Company Shareholders' Equity	(436,951)	(431,592)
Noncontrolling Interest	(1,870)	(1,971)
Total Equity	(438,821)	(433,563)
Total Liabilities and Total Equity	(919,771)	(930,590)
Parent
Current Assets:
Cash and Cash Equivalents	18,998	18,469
Restricted Cash	0	0
Net Receivables	763	683
Intercompany Receivables	38,717	53,444
Inventories	37,145	29,450
Prepaid Expenses	16,567	8,774
Other Current Assets	4,790	4,030
Total Current Assets	116,980	114,850
Property, Plant and Equipment	226,599	225,064
Accumulated Depreciation	(153,143)	(146,320)
Property, Plant and Equipment, Net	73,456	78,744
Deferred Income Taxes	1,970	1,308
Investment in Affiliates	398,205	392,486
Intercompany Loans	304,630	304,822
Goodwill	12,869	12,869
Intangible Assets, Net	2,842	2,105
Other Assets	4,872	10,363
Total Assets	915,824	917,547
Current Liabilities:
Current Portion of Long-Term Debt	29,611	29,413
Accounts Payable	43,558	39,927
Intercompany Payables	134,113	133,778
Employee Compensation and Benefits	12,399	8,311
Income Taxes Payable	347	366
Other Current Liabilities	22,317	20,183
Total Current Liabilities	242,345	231,978
Long-Term Liabilities:
Long-Term Debt	326,948	344,147
Intercompany Loans	3,490	0
Employee-Related Benefits	12,197	11,160
Deferred Income Taxes	0	0
Other Liabilities	28,647	31,788
Total Long-Term Liabilities	371,282	387,095
Total Liabilities	613,627	619,073
Common Stock	6,778	6,705
Additional Paid-In Capital	22,273	15,089
Retained Earnings	306,667	297,032
Accumulated Other Comprehensive Loss	(35,391)	(22,323)
Total Tennant Company Shareholders' Equity	300,327	296,503
Noncontrolling Interest	1,870	1,971
Total Equity	302,197	298,474
Total Liabilities and Total Equity	915,824	917,547
Guarantor Subsidiaries
Current Assets:
Cash and Cash Equivalents	1,858	507
Restricted Cash	0	0
Net Receivables	92,295	88,629
Intercompany Receivables	134,113	133,778
Inventories	16,372	12,695
Prepaid Expenses	677	1,172
Other Current Assets	333	0
Total Current Assets	245,648	236,781
Property, Plant and Equipment	12,581	12,155
Accumulated Depreciation	(6,280)	(6,333)
Property, Plant and Equipment, Net	6,301	5,822
Deferred Income Taxes	3,236	2,669
Investment in Affiliates	11,674	11,273
Intercompany Loans	0	0
Goodwill	1,739	1,739
Intangible Assets, Net	2,791	2,898
Other Assets	0	0
Total Assets	271,389	261,182
Current Liabilities:
Current Portion of Long-Term Debt	0	0
Accounts Payable	4,248	3,018
Intercompany Payables	2,311	1,963
Employee Compensation and Benefits	11,553	10,355
Income Taxes Payable	0	0
Other Current Liabilities	13,174	15,760
Total Current Liabilities	31,286	31,096
Long-Term Liabilities:
Long-Term Debt	0	0
Intercompany Loans	128,000	128,000
Employee-Related Benefits	1,972	3,992
Deferred Income Taxes	0	0
Other Liabilities	2,715	2,483
Total Long-Term Liabilities	132,687	134,475
Total Liabilities	163,973	165,571
Common Stock	0	0
Additional Paid-In Capital	77,551	72,483
Retained Earnings	31,024	23,797
Accumulated Other Comprehensive Loss	(1,159)	(669)
Total Tennant Company Shareholders' Equity	107,416	95,611
Noncontrolling Interest	0	0
Total Equity	107,416	95,611
Total Liabilities and Total Equity	271,389	261,182
Non-Guarantor Subsidiaries
Current Assets:
Cash and Cash Equivalents	33,045	39,422
Restricted Cash	543	653
Net Receivables	122,265	120,204
Intercompany Receivables	0	0
Inventories	96,099	94,542
Prepaid Expenses	10,138	9,405
Other Current Assets	3,584	3,473
Total Current Assets	265,674	267,699
Property, Plant and Equipment	142,427	145,549
Accumulated Depreciation	(53,202)	(50,097)
Property, Plant and Equipment, Net	89,225	95,452
Deferred Income Taxes	8,515	7,157
Investment in Affiliates	18,732	20,811
Intercompany Loans	3,490	4,983
Goodwill	171,107	171,436
Intangible Assets, Net	152,041	167,344
Other Assets	9,858	10,956
Total Assets	718,642	745,838
Current Liabilities:
Current Portion of Long-Term Debt	1,358	1,470
Accounts Payable	55,796	53,137
Intercompany Payables	36,406	51,481
Employee Compensation and Benefits	17,337	18,591
Income Taxes Payable	2,462	2,472
Other Current Liabilities	31,262	33,504
Total Current Liabilities	144,621	160,655
Long-Term Liabilities:
Long-Term Debt	1,751	1,809
Intercompany Loans	176,630	181,805
Employee-Related Benefits	8,414	8,715
Deferred Income Taxes	50,444	53,225
Other Liabilities	5,377	1,677
Total Long-Term Liabilities	242,616	247,231
Total Liabilities	387,237	407,886
Common Stock	11,131	11,131
Additional Paid-In Capital	384,460	384,460
Retained Earnings	(11,489)	(21,219)
Accumulated Other Comprehensive Loss	(54,567)	(38,391)
Total Tennant Company Shareholders' Equity	329,535	335,981
Noncontrolling Interest	1,870	1,971
Total Equity	331,405	337,952
Total Liabilities and Total Equity	$ 718,642	$ 745,838