Note 14 - Segment and Geographic Information - Summary of Revenues (Details) - USD ($) $ in Thousands		3 Months Ended																12 Months Ended
		Dec. 31, 2019		Sep. 30, 2019	[2]	Jun. 30, 2019	[3]	Mar. 31, 2019	[4]	Dec. 31, 2018		Sep. 30, 2018	[2]	Jun. 30, 2018	[4]	Mar. 31, 2018	[4]	Dec. 31, 2019		Dec. 31, 2018		Dec. 31, 2017
Revenues		$ 309,502	[1]	$ 308,789		$ 318,740		$ 276,904		$ 333,998	[1]	$ 339,679		$ 335,030		$ 324,861		$ 1,213,935	[5]	$ 1,333,568	[5]	$ 1,359,019	[5]
Gross profit		63,711	[1]	66,792		67,437		48,295		61,696	[1]	72,673		71,053		61,504		246,235	[5]	266,926	[5]	284,812	[5]
Operating income (loss)		(3,361)	[1]	$ 14,649		$ 459		$ (774)		(1,002)	[1]	$ 13,009		$ 14,459		$ 3,181		10,973	[5]	29,647	[5]	(43,520)	[5]
Interest expense																		(14,002)		(17,327)		(16,001)
Interest income																		1,038		516		145
Other	[6]																	(10,893)		(9,881)		(2,201)
Total other expense																		(23,857)		(26,692)		(18,057)
Income (loss) before taxes on income																		(12,884)		2,955		(61,577)
Total assets		995,513								992,417								995,513		992,417		1,107,099
Capital expenditures																		28,772		30,514		30,830
Depreciation and amortization																		36,163		37,855		44,419
Long-lived assets	[5],[7]	101,091								128,660								101,091		128,660		125,309
UNITED STATES
Revenues	[5]																	914,676		966,291		1,028,313
Gross profit	[5]																	175,705		178,024		226,026
Operating income (loss)	[5]																	6,212		174		(33,583)
Long-lived assets	[5],[7]	80,910								105,978								80,910		105,978		93,472
CANADA
Revenues	[5]																	123,033		133,612		139,734
Gross profit	[5]																	22,183		22,823		31,173
Operating income (loss)	[5]																	7,460		9,482		12,220
Long-lived assets	[5],[7]	7,462								7,725								7,462		7,725		8,816
Europe [Member]
Revenues	[5]																	64,278		66,794		71,839
Gross profit	[5]																	14,849		8,379		11,997
Operating income (loss)	[5]																	(11,363)		(10,599)		(3,771)
Long-lived assets	[5],[7]	2,499								8,295								2,499		8,295		13,435
Other Foreign Countries [Member]
Revenues	[5]																	111,948		166,871		119,133
Gross profit	[5]																	33,498		57,700		15,616
Operating income (loss)	[5]																	8,664		30,590		(18,386)
Long-lived assets	[5],[7]	10,220								6,662								10,220		6,662		9,586
Infrastructure Solutions [Member]
Revenues																		590,797		604,121		612,154
Infrastructure Solutions [Member] | UNITED STATES
Revenues																		427,220		430,187		437,944
Infrastructure Solutions [Member] | CANADA
Revenues																		65,370		62,292		60,675
Infrastructure Solutions [Member] | Europe [Member]
Revenues																		49,157		54,567		58,520
Infrastructure Solutions [Member] | Other Foreign Countries [Member]
Revenues																		49,050		57,075		55,015
Corrosion Protection [Member]
Revenues																		295,090		393,740		456,139
Corrosion Protection [Member] | UNITED STATES
Revenues																		159,408		200,397		299,643
Corrosion Protection [Member] | CANADA
Revenues																		57,663		71,320		79,059
Corrosion Protection [Member] | Europe [Member]
Revenues																		15,121		12,227		13,319
Corrosion Protection [Member] | Other Foreign Countries [Member]
Revenues																		62,898		109,796		64,118
Energy Services [Member]
Revenues																		328,048		335,707		290,726
Energy Services [Member] | UNITED STATES
Revenues																		328,048		335,707		290,726
Energy Services [Member] | CANADA
Revenues																		0		0		0
Energy Services [Member] | Europe [Member]
Revenues																		0		0		0
Energy Services [Member] | Other Foreign Countries [Member]
Revenues																		0		0		0
Operating Segments [Member] | Infrastructure Solutions [Member]
Revenues																		590,797		604,121		612,154
Gross profit																		144,074		132,411		140,823
Operating income (loss)	[8]																	42,079		37,509		(47,316)
Total assets		508,226								500,977								508,226		500,977		531,746
Capital expenditures																		10,679		12,730		16,680
Depreciation and amortization																		13,773		16,758		18,731
Operating Segments [Member] | Corrosion Protection [Member]
Revenues																		295,090		393,740		456,139
Gross profit																		60,927		92,968		108,240
Operating income (loss)	[9]																	(5,635)		16,283		32,222
Total assets		278,694								279,106								278,694		279,106		329,848
Capital expenditures																		11,437		9,754		8,603
Depreciation and amortization																		12,487		11,874		15,598
Operating Segments [Member] | Energy Services [Member]
Revenues																		328,048		335,707		290,726
Gross profit																		41,234		41,547		35,749
Operating income (loss)	[10]																	9,740		9,638		7,736
Total assets		161,165								163,109								161,165		163,109		152,416
Capital expenditures																		3,437		3,053		2,713
Depreciation and amortization																		7,490		7,111		6,726
Corporate, Non-Segment [Member]
Operating income (loss)	[11]																	(35,211)		(33,783)		(36,162)
Total assets		31,336								41,432								31,336		41,432		22,775
Capital expenditures																		3,219		4,977		2,834
Depreciation and amortization																		2,413		2,112		3,364
Segment Reconciling Items [Member]
Total assets		$ 16,092								$ 7,793								$ 16,092		$ 7,793		$ 70,314

[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.

[6] Other expense for 2019 includes $10.2 million of restructuring charges (see Note 4). Other expense for 2018 includes charges of $7.0 million related to the loss on the sale of Bayou (see Note 1) and $4.0 million of restructuring charges (see Note 4).

[7] Long-lived assets do not include goodwill, intangible assets, operating lease assets or deferred tax assets.

[8] Operating income for 2019 includes: (i) $7.5 million of restructuring charges (see Note 4); (ii) $1.0 million of costs primarily related to the planned divestiture of certain international operations; and (iii) $17.6 million of impairment charges to assets held for sale (see Note 6). Operating income for 2018 includes: (i) $16.1 million of restructuring charges (see Note 4); and (ii) $0.4 million of cost incurred related to the disposition of Denmark. Operating loss for 2017 includes: (i) $17.5 million of restructuring charges (see Note 4); (ii) $45.4 million of goodwill impairment charges (see Note 2); (iii) $41.0 million of definite-lived intangible asset impairment charges (see Note 2); and (iv) $0.1 million of costs incurred related to the acquisition of Environmental Techniques.

[9] Operating loss for 2019 includes: (i) $7.7 million of restructuring charges (see Note 4); (ii) $0.1 million of divestiture costs; and (iii) $2.9 million of impairment charges to assets held for sale (see Note 6). Operating income for 2018 includes: (i) $7.6 million of restructuring charges (see Note 4); and (ii) $2.5 million of costs incurred related to the divestiture of Bayou. Operating income for 2017 includes $4.9 million of restructuring charges (see Note 4) and (ii) $1.6 million of costs incurred related to the planned divestiture of Bayou.

[10] Operating income for 2019 includes $1.7 million of restructuring charges (see Note 4). Operating income for 2018 includes $0.3 million of restructuring charges (see Note 4).

[11] Operating loss for 2019 includes: (i) $5.2 million of restructuring charges (see Note 4); (ii) $2.2 million of costs primarily related to the planned divestiture of certain international operations; and (iii) $2.9 million of impairment charges to assets held for sale (see Note 6). Operating loss for 2018 includes $1.6 million of restructuring charges (see Note 4) and $4.1 million of divestiture costs. Operating loss for 2017 includes $1.6 million of restructuring charges (see Note 4) and $1.2 million of divestiture costs.