Note 7 - Goodwill and Intangible Assets - Reconciliation Goodwill (Details) - USD ($)		6 Months Ended
		Jun. 30, 2019	Dec. 31, 2018
Goodwill, gross		$ 398,548,000	$ 402,408,000
Accumulated impairment losses		(141,775,000)	(141,775,000)
Goodwill, net		256,773,000	260,633,000
Foreign currency translation		364,000
Reclassification to assets held for sale (1)	[1]	(4,224,000)
Infrastructure Solutions [Member]
Goodwill, gross		240,280,000	244,521,000
Accumulated impairment losses		(62,848,000)	(62,848,000)
Goodwill, net		177,432,000	181,673,000
Foreign currency translation		(17,000)
Reclassification to assets held for sale (1)	[1]	(4,224,000)
Corrosion Protection [Member]
Goodwill, gross		76,764,000	76,383,000
Accumulated impairment losses		(45,400,000)	(45,400,000)
Goodwill, net		31,364,000	30,983,000
Foreign currency translation		381,000
Reclassification to assets held for sale (1)	[1]	0
Energy Services [Member]
Goodwill, gross		81,504,000	81,504,000
Accumulated impairment losses		(33,527,000)	(33,527,000)
Goodwill, net		47,977,000	$ 47,977,000
Foreign currency translation		0
Reclassification to assets held for sale (1)	[1]	$ 0

[1] During the second quarter of 2019, the Company classified certain assets of its CIPP contracting operation in Europe as held for sale. See Note 5.