Note 5 - Assets and Liabilities Held for Sale (Details Textual) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Impairment of Long-Lived Assets to be Disposed of	$ 11,946,000	$ 0	$ 11,946,000	$ 0
Insituform Australia [Member] | Infrastructure Solutions [Member]
Impairment of Long-Lived Assets to be Disposed of	5,100,000
Insituform Netherlands [Member] | Infrastructure Solutions [Member]
Impairment of Long-Lived Assets to be Disposed of	3,900,000
Corrpower [Member] | Corrosion Protection [Member]
Impairment of Long-Lived Assets to be Disposed of	1,100,000
United Mexico [Member] | Corrosion Protection [Member]
Impairment of Long-Lived Assets to be Disposed of	$ 1,800,000