Note 5 - Assets and Liabilities Held for Sale - Assets and Liabilities Held for Sale (Details) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2020		Dec. 31, 2019
Disposal Group, Including Discontinued Operation, Contract Assets, Current	$ 1,800		$ 5,400
Total current assets	11,715		16,092
Disposal Group, Including Discontinued Operation, Contract Liabilities, Current	100		100
Total current liabilities	1,648		6,485
Disposal Group, Held-for-sale, Not Discontinued Operations [Member]
Receivables, net	543	[1]	4,136	[2]
Retainage	535	[1]	518	[2]
Disposal Group, Including Discontinued Operation, Contract Assets, Current	1,830	[1]	5,350	[2]
Inventories	124	[1]	2,097	[2]
Prepaid expenses and other current assets	115	[1]	799	[2]
Total current assets	3,147	[1]	12,900	[2]
Property, plant & equipment, less accumulated depreciation	7,178	[1]	10,962	[2]
Goodwill	2,640	[1]	4,224	[2]
Intangible assets, less accumulated amortization	1,434	[1]	1,528	[2]
Disposal Group, Including Discontinued Operation, Operating Lease, Right-of-Use Asset	55	[1]	326	[2]
Other non-current assets	122	[1]	130	[2]
Impairment of assets held for sale	(2,861)	[1]	(13,978)	[2]
Total assets held for sale	11,715	[1]	16,092	[2]
Accounts payable	707	[1]	2,174	[2]
Accrued expenses	882	[1]	3,961	[2]
Disposal Group, Including Discontinued Operation, Contract Liabilities, Current	7	[1]	122	[2]
Total current liabilities	1,596	[1]	6,257	[2]
Disposal Group, Including Discontinued Operation, Operating Lease, Liability, Noncurrent	12	[1]	174	[2]
Other non-current liabilities	40	[1]	54	[2]
Total liabilities held for sale	$ 1,648	[1]	$ 6,485	[2]

[1] Includes Environmental Techniques and land held at Corporate.

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