Note 7 - Goodwill and Intangible Assets - Reconciliation Goodwill (Details) - USD ($) $ in Thousands		9 Months Ended
		Sep. 30, 2019	Dec. 31, 2018
Goodwill, gross		$ 397,376	$ 402,408
Accumulated impairment losses		(141,775)	(141,775)
Goodwill, net		255,601	260,633
Foreign currency translation		(808)
Reclassification to assets held for sale (1)	[1]	(4,224)
Infrastructure Solutions [Member]
Goodwill, gross		239,213	244,521
Accumulated impairment losses		(62,848)	(62,848)
Goodwill, net		176,365	181,673
Foreign currency translation		(1,084)
Reclassification to assets held for sale (1)	[1]	(4,224)
Corrosion Protection [Member]
Goodwill, gross		76,659	76,383
Accumulated impairment losses		(45,400)	(45,400)
Goodwill, net		31,259	30,983
Foreign currency translation		276
Reclassification to assets held for sale (1)	[1]	0
Energy Services [Member]
Goodwill, gross		81,504	81,504
Accumulated impairment losses		(33,527)	(33,527)
Goodwill, net		47,977	$ 47,977
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.