Note 3 - Revenue - Disaggregation of Revenue (Details) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
		Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Revenues	[1]	$ 308,789	$ 339,679	$ 904,433	$ 999,570
Fixed-price Contract [Member]
Revenues		194,070	212,602	547,035	641,004
Time-and-materials Contract [Member]
Revenues		91,890	101,917	288,506	294,979
Product Sales [Member]
Revenues		22,780	22,756	68,649	61,150
License Fees [Member]
Revenues		49	2,404	243	2,437
Infrastructure Solutions [Member]
Revenues		156,087	155,681	443,069	450,840
Infrastructure Solutions [Member] | Fixed-price Contract [Member]
Revenues		139,363	141,598	394,489	416,392
Infrastructure Solutions [Member] | Time-and-materials Contract [Member]
Revenues		0	0	0	0
Infrastructure Solutions [Member] | Product Sales [Member]
Revenues		16,675	11,679	48,337	32,011
Infrastructure Solutions [Member] | License Fees [Member]
Revenues		49	2,404	243	2,437
Corrosion Protection [Member]
Revenues		75,901	105,624	217,996	300,118
Corrosion Protection [Member] | Fixed-price Contract [Member]
Revenues		53,704	68,935	149,333	210,819
Corrosion Protection [Member] | Time-and-materials Contract [Member]
Revenues		16,092	25,612	48,351	60,160
Corrosion Protection [Member] | Product Sales [Member]
Revenues		6,105	11,077	20,312	29,139
Corrosion Protection [Member] | License Fees [Member]
Revenues		0	0	0	0
Energy Services [Member]
Revenues		76,801	78,374	243,368	248,612
Energy Services [Member] | Fixed-price Contract [Member]
Revenues		1,003	2,069	3,213	13,793
Energy Services [Member] | Time-and-materials Contract [Member]
Revenues		75,798	76,305	240,155	234,819
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		231,904	246,574	680,666	736,805
UNITED STATES | Infrastructure Solutions [Member]
Revenues		112,357	111,902	321,205	323,327
UNITED STATES | Corrosion Protection [Member]
Revenues		42,746	56,298	116,093	164,866
UNITED STATES | Energy Services [Member]
Revenues		76,801	78,374	243,368	248,612
CANADA
Revenues	[1]	32,124	35,920	89,584	95,185
CANADA | Infrastructure Solutions [Member]
Revenues		17,775	16,153	47,320	44,028
CANADA | Corrosion Protection [Member]
Revenues		14,349	19,767	42,264	51,157
CANADA | Energy Services [Member]
Revenues		0	0	0	0
Europe [Member]
Revenues	[1]	16,347	16,281	49,731	48,135
Europe [Member] | Infrastructure Solutions [Member]
Revenues		12,889	13,460	38,302	39,600
Europe [Member] | Corrosion Protection [Member]
Revenues		3,458	2,821	11,429	8,535
Europe [Member] | Energy Services [Member]
Revenues		0	0	0	0
Other Foreign Countries [Member]
Revenues	[1]	28,414	40,904	84,452	119,445
Other Foreign Countries [Member] | Infrastructure Solutions [Member]
Revenues		13,066	14,166	36,242	43,885
Other Foreign Countries [Member] | Corrosion Protection [Member]
Revenues		15,348	26,738	48,210	75,560
Other Foreign Countries [Member] | Energy Services [Member]
Revenues		$ 0	$ 0	$ 0	$ 0

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