Note 3 - Revenues - Disaggregation of Revenue (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Revenues	[1]	$ 807,764	$ 885,887	$ 997,861
Fixed-price Contract [Member]
Revenues		675,521	726,929	852,859
Time-and-materials Contract [Member]
Revenues		52,713	65,084	58,372
Product Sales [Member]
Revenues		79,499	93,631	84,181
License Fees [Member]
Revenues		31	243	2,449
Infrastructure Solutions [Member]
Revenues		562,571	590,797	604,121
Infrastructure Solutions [Member] | Fixed-price Contract [Member]
Revenues		513,187	523,042	556,642
Infrastructure Solutions [Member] | Time-and-materials Contract [Member]
Revenues		0	0	0
Infrastructure Solutions [Member] | Product Sales [Member]
Revenues		49,353	67,512	45,030
Infrastructure Solutions [Member] | License Fees [Member]
Revenues		31	243	2,449
Corrosion Protection [Member]
Revenues		245,193	295,090	393,740
Corrosion Protection [Member] | Fixed-price Contract [Member]
Revenues		162,334	203,887	296,217
Corrosion Protection [Member] | Time-and-materials Contract [Member]
Revenues		52,713	65,084	58,372
Corrosion Protection [Member] | Product Sales [Member]
Revenues		30,146	26,119	39,151
Corrosion Protection [Member] | License Fees [Member]
Revenues		0	0	0
UNITED STATES
Revenues	[1]	572,729	586,628	630,584
UNITED STATES | Infrastructure Solutions [Member]
Revenues		443,196	427,220	430,187
UNITED STATES | Corrosion Protection [Member]
Revenues		129,533	159,408	200,397
CANADA
Revenues	[1]	118,253	123,033	133,612
CANADA | Infrastructure Solutions [Member]
Revenues		69,190	65,370	62,292
CANADA | Corrosion Protection [Member]
Revenues		49,063	57,663	71,320
Europe [Member]
Revenues	[1]	37,251	64,278	66,794
Europe [Member] | Infrastructure Solutions [Member]
Revenues		23,782	49,157	54,567
Europe [Member] | Corrosion Protection [Member]
Revenues		13,469	15,121	12,227
Other Foreign Countries [Member]
Revenues	[1]	79,531	111,948	166,871
Other Foreign Countries [Member] | Infrastructure Solutions [Member]
Revenues		26,403	49,050	57,075
Other Foreign Countries [Member] | Corrosion Protection [Member]
Revenues		$ 53,128	$ 62,898	$ 109,796

[1] Attributed to the country of origin.