Note 6 - Assets and Liabilities Held for Sale - Assets and Liabilities Held for Sale (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019		Dec. 31, 2018		Dec. 31, 2017
Disposal Group, Including Discontinued Operation, Contract Assets, Current	$ 5,400		$ 1,800
Total current assets	16,092		7,792
Impairment of assets held for sale	(23,427)		0		$ 0
Disposal Group, Including Discontinued Operation, Contract Liabilities, Current	100		100
Total current liabilities	6,485		5,260
Disposal Group, Held-for-sale, Not Discontinued Operations [Member]
Receivables, net	4,136	[1]	1,309	[2]
Retainage	518	[1]	15	[2]
Disposal Group, Including Discontinued Operation, Contract Assets, Current	5,350	[1]	1,777	[2]
Inventories	2,097	[1]	2,123	[2]
Prepaid expenses and other current assets	799	[1]	300	[2]
Total current assets	12,900	[1]	5,524	[2]
Property, plant & equipment, less accumulated depreciation	10,962	[1]	2,268	[2]
Goodwill	4,224	[1]	0	[2]
Intangible assets, less accumulated amortization	1,528	[1]	0	[2]
Disposal Group, Including Discontinued Operation, Operating Lease, Right-of-Use Asset	326	[1]	0	[2]
Other non-current assets	130	[1]	0	[2]
Impairment of assets held for sale	(13,978)	[1]	0	[2]
Total assets held for sale	16,092	[1]	7,792	[2]
Accounts payable	2,174	[1]	1,331	[2]
Accrued expenses	3,961	[1]	3,891	[2]
Disposal Group, Including Discontinued Operation, Contract Liabilities, Current	122	[1]	38	[2]
Total current liabilities	6,257	[1]	5,260	[2]
Disposal Group, Including Discontinued Operation, Operating Lease, Liability, Noncurrent	174	[1]	0	[2]
Other non-current liabilities	54	[1]	0	[2]
Total liabilities held for sale	$ 6,485	[1]	$ 5,260	[2]

[1] Includes Insituform Australia, Insituform Spain, Environmental Techniques and land held at Corporate.

[2] Includes Insituform Australia.