Note 3 - Revenues - Disaggregation of Revenue (Details) - USD ($) $ in Thousands		3 Months Ended																12 Months Ended
		Dec. 31, 2019	[1]	Sep. 30, 2019	[2]	Jun. 30, 2019	[3]	Mar. 31, 2019	[4]	Dec. 31, 2018	[1]	Sep. 30, 2018	[2]	Jun. 30, 2018	[4]	Mar. 31, 2018	[4]	Dec. 31, 2019		Dec. 31, 2018		Dec. 31, 2017
Revenues		$ 309,502		$ 308,789		$ 318,740		$ 276,904		$ 333,998		$ 339,679		$ 335,030		$ 324,861		$ 1,213,935	[5]	$ 1,333,568	[5]	$ 1,359,019	[5]
Fixed-price Contract [Member]
Revenues																		727,633		868,993		932,406
Time-and-materials Contract [Member]
Revenues																		392,428		377,945		337,789
Product Sales [Member]
Revenues																		93,631		84,181		88,249
License Fees [Member]
Revenues																		243		2,449		575
Infrastructure Solutions [Member]
Revenues																		590,797		604,121		612,154
Infrastructure Solutions [Member] | Fixed-price Contract [Member]
Revenues																		523,042		556,642		569,701
Infrastructure Solutions [Member] | Time-and-materials Contract [Member]
Revenues																		0		0		0
Infrastructure Solutions [Member] | Product Sales [Member]
Revenues																		67,512		45,030		41,878
Infrastructure Solutions [Member] | License Fees [Member]
Revenues																		243		2,449		575
Corrosion Protection [Member]
Revenues																		295,090		393,740		456,139
Corrosion Protection [Member] | Fixed-price Contract [Member]
Revenues																		203,887		296,217		353,480
Corrosion Protection [Member] | Time-and-materials Contract [Member]
Revenues																		65,084		58,372		56,288
Corrosion Protection [Member] | Product Sales [Member]
Revenues																		26,119		39,151		46,371
Corrosion Protection [Member] | License Fees [Member]
Revenues																		0		0		0
Energy Services [Member]
Revenues																		328,048		335,707		290,726
Energy Services [Member] | Fixed-price Contract [Member]
Revenues																		704		16,134		9,225
Energy Services [Member] | Time-and-materials Contract [Member]
Revenues																		327,344		319,573		281,501
Energy Services [Member] | Product Sales [Member]
Revenues																		0		0		0
Energy Services [Member] | License Fees [Member]
Revenues																		0		0		0
UNITED STATES
Revenues	[5]																	914,676		966,291		1,028,313
UNITED STATES | Infrastructure Solutions [Member]
Revenues																		427,220		430,187		437,944
UNITED STATES | Corrosion Protection [Member]
Revenues																		159,408		200,397		299,643
UNITED STATES | Energy Services [Member]
Revenues																		328,048		335,707		290,726
CANADA
Revenues	[5]																	123,033		133,612		139,734
CANADA | Infrastructure Solutions [Member]
Revenues																		65,370		62,292		60,675
CANADA | Corrosion Protection [Member]
Revenues																		57,663		71,320		79,059
CANADA | Energy Services [Member]
Revenues																		0		0		0
Europe [Member]
Revenues	[5]																	64,278		66,794		71,839
Europe [Member] | Infrastructure Solutions [Member]
Revenues																		49,157		54,567		58,520
Europe [Member] | Corrosion Protection [Member]
Revenues																		15,121		12,227		13,319
Europe [Member] | Energy Services [Member]
Revenues																		0		0		0
Other Foreign Countries [Member]
Revenues	[5]																	111,948		166,871		119,133
Other Foreign Countries [Member] | Infrastructure Solutions [Member]
Revenues																		49,050		57,075		55,015
Other Foreign Countries [Member] | Corrosion Protection [Member]
Revenues																		62,898		109,796		64,118
Other Foreign Countries [Member] | Energy Services [Member]
Revenues																		$ 0		$ 0		$ 0

[1] Includes pre-tax expenses of $13.9 million related to our restructuring efforts (see Note 4).

[2] Includes pre-tax expenses of $7.4 million related to our restructuring efforts (see Note 4).

[3] Includes pre-tax expenses of $6.5 million related to our restructuring efforts (see Note 4).

[4] Includes pre-tax expenses of $5.2 million related to our restructuring efforts (see Note 4).

[5] Attributed to the country of origin.