Note 3 - Revenues - Disaggregation of Revenue (Details) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
		Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Revenues	[1]	$ 275,884	$ 308,789	$ 808,276	$ 904,433
Fixed-price Contract [Member]
Revenues		175,500	194,070	494,986	547,035
Time-and-materials Contract [Member]
Revenues		70,489	91,890	233,548	288,506
Product Sales [Member]
Revenues		29,847	22,780	79,694	68,649
License Fees [Member]
Revenues		48	49	48	243
Infrastructure Solutions [Member]
Revenues		152,102	156,087	419,738	443,069
Infrastructure Solutions [Member] | Fixed-price Contract [Member]
Revenues		130,685	139,363	364,591	394,489
Infrastructure Solutions [Member] | Time-and-materials Contract [Member]
Revenues		0	0	0	0
Infrastructure Solutions [Member] | Product Sales [Member]
Revenues		21,369	16,675	55,099	48,337
Infrastructure Solutions [Member] | License Fees [Member]
Revenues		48	49	48	243
Corrosion Protection [Member]
Revenues		60,986	75,901	182,545	217,996
Corrosion Protection [Member] | Fixed-price Contract [Member]
Revenues		43,812	53,704	126,449	149,333
Corrosion Protection [Member] | Time-and-materials Contract [Member]
Revenues		8,696	16,092	31,501	48,351
Corrosion Protection [Member] | Product Sales [Member]
Revenues		8,478	6,105	24,595	20,312
Corrosion Protection [Member] | License Fees [Member]
Revenues		0	0	0	0
Energy Services [Member]
Revenues		62,796	76,801	205,993	243,368
Energy Services [Member] | Fixed-price Contract [Member]
Revenues		1,003	1,003	3,946	3,213
Energy Services [Member] | Time-and-materials Contract [Member]
Revenues		61,793	75,798	202,047	240,155
Energy Services [Member] | Product Sales [Member]
Revenues		0	0	0	0
Energy Services [Member] | License Fees [Member]
Revenues		0	0	0	0
UNITED STATES
Revenues	[1]	212,407	231,904	643,074	680,666
UNITED STATES | Infrastructure Solutions [Member]
Revenues		119,334	112,357	337,457	321,205
UNITED STATES | Corrosion Protection [Member]
Revenues		30,277	42,746	99,624	116,093
UNITED STATES | Energy Services [Member]
Revenues		62,796	76,801	205,993	243,368
CANADA
Revenues	[1]	34,325	32,124	81,175	89,584
CANADA | Infrastructure Solutions [Member]
Revenues		20,864	17,775	46,092	47,320
CANADA | Corrosion Protection [Member]
Revenues		13,461	14,349	35,083	42,264
CANADA | Energy Services [Member]
Revenues		0	0	0	0
Europe [Member]
Revenues	[1]	9,957	16,347	27,820	49,731
Europe [Member] | Infrastructure Solutions [Member]
Revenues		5,727	12,889	17,500	38,302
Europe [Member] | Corrosion Protection [Member]
Revenues		4,230	3,458	10,320	11,429
Europe [Member] | Energy Services [Member]
Revenues		0	0	0	0
Other Foreign Countries [Member]
Revenues	[1]	19,195	28,414	56,207	84,452
Other Foreign Countries [Member] | Infrastructure Solutions [Member]
Revenues		6,177	13,066	18,689	36,242
Other Foreign Countries [Member] | Corrosion Protection [Member]
Revenues		13,018	15,348	37,518	48,210
Other Foreign Countries [Member] | Energy Services [Member]
Revenues		$ 0	$ 0	$ 0	$ 0

[1] Revenues and gross profit are attributed to the country of origin