Note 12 - Segment Reporting - Summary of Revenues (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
Gross profit	[1]	66,792	72,673	182,524	205,230
Total operating income (loss)		14,649	13,009	14,334	30,649
Interest expense		(3,446)	(3,870)	(10,602)	(13,236)
Interest income		268	130	814	239
Other	[2]	(5,236)	(9,281)	(6,925)	(10,049)
Total other expense		(8,414)	(13,021)	(16,713)	(23,046)
Income (loss) before taxes on income		6,235	(12)	(2,379)	7,603
UNITED STATES
Revenues		231,904	246,574	680,666	736,805
Gross profit	[1]	48,331	46,586	130,950	137,071
CANADA
Revenues	[1]	32,124	35,920	89,584	95,185
Gross profit	[1]	6,424	7,265	14,906	17,494
Europe [Member]
Revenues	[1]	16,347	16,281	49,731	48,135
Gross profit	[1]	4,309	2,931	11,139	5,467
Other Foreign Countries [Member]
Revenues	[1]	28,414	40,904	84,452	119,445
Gross profit	[1]	7,728	15,891	25,529	45,198
Infrastructure Solutions [Member]
Revenues		156,087	155,681	443,069	450,840
Infrastructure Solutions [Member] | UNITED STATES
Revenues		112,357	111,902	321,205	323,327
Infrastructure Solutions [Member] | CANADA
Revenues		17,775	16,153	47,320	44,028
Infrastructure Solutions [Member] | Europe [Member]
Revenues		12,889	13,460	38,302	39,600
Infrastructure Solutions [Member] | Other Foreign Countries [Member]
Revenues		13,066	14,166	36,242	43,885
Corrosion Protection [Member]
Revenues		75,901	105,624	217,996	300,118
Corrosion Protection [Member] | UNITED STATES
Revenues		42,746	56,298	116,093	164,866
Corrosion Protection [Member] | CANADA
Revenues		14,349	19,767	42,264	51,157
Corrosion Protection [Member] | Europe [Member]
Revenues		3,458	2,821	11,429	8,535
Corrosion Protection [Member] | Other Foreign Countries [Member]
Revenues		15,348	26,738	48,210	75,560
Energy Services [Member]
Revenues		76,801	78,374	243,368	248,612
Energy Services [Member] | UNITED STATES
Revenues		76,801	78,374	243,368	248,612
Energy Services [Member] | CANADA
Revenues		0	0	0	0
Energy Services [Member] | Europe [Member]
Revenues		0	0	0	0
Energy Services [Member] | Other Foreign Countries [Member]
Revenues		0	0	0	0
Operating Segments [Member] | Infrastructure Solutions [Member]
Revenues		156,087	155,681	443,069	450,840
Gross profit		39,569	38,135	105,026	100,793
Total operating income (loss)	[3]	18,376	13,088	33,211	29,241
Operating Segments [Member] | Corrosion Protection [Member]
Revenues		75,901	105,624	217,996	300,118
Gross profit		17,232	26,411	46,797	74,524
Total operating income (loss)	[4]	2,362	8,299	(3,261)	20,214
Operating Segments [Member] | Energy Services [Member]
Revenues		76,801	78,374	243,368	248,612
Gross profit		9,991	8,127	30,701	29,913
Total operating income (loss)		2,257	456	7,479	6,081
Corporate, Non-Segment [Member]
Total operating income (loss)	[5]	$ (8,346)	$ (8,834)	$ (23,095)	$ (24,887)

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

[2] Other expense in the third quarter and first nine months of 2019 includes $5.3 million and $6.5 million, respectively, of 2017 Restructuring charges (see Note 4). Other expense for the third quarter and first nine months of 2018 includes charges of $8.7 million related to the loss on the sale of Bayou (see Note 1) and $0.2 million related to 2017 restructuring charges (see Note 4).

[3] Operating income in the third quarter of 2019 and 2018 includes $1.2 million and $5.9 million, respectively, of 2017 Restructuring charges (see Note 4) and $0.5 million and $0.1 million, respectively, of costs primarily related to the planned divestiture of certain international operations. Operating income in the first nine months of 2019 and 2018 includes $4.7 million and $11.7 million, respectively, of 2017 Restructuring charges and $1.0 million and $0.4 million, respectively, of divestiture costs. Additionally, operating income in the first nine months of 2019 includes $9.0 million of impairment charges to assets held for sale (see Note 5).

[4] Operating income in the third quarter of 2019 and 2018 includes $0.8 million and $1.0 million, respectively, of 2017 Restructuring charges (see Note 4) and less than $0.1 million and $1.6 million, respectively, of costs primarily related to the planned divestiture of certain international operations in 2019 and the divestiture of Bayou in 2018. Operating income in the first nine months of 2019 and 2018 includes $4.3 million and $2.8 million, respectively, of 2017 Restructuring charges, and $0.1 million and $1.8 million, respectively, of divestiture costs. Additionally, operating income in the first nine months of 2019 includes $2.9 million of impairment charges to assets held for sale (see Note 5).

[5] Operating loss in the third quarter of 2019 and 2018 includes $1.1 and $0.3 million, respectively, of 2017 Restructuring charges (see Note 4), and $1.3 million and $3.1 million, respectively of costs primarily related to the planned divestiture of certain international operations in 2019 and the divestiture of Bayou in 2018. Operating loss in the first nine months of 2019 and 2018 includes $2.4 million and $0.9 million, respectively, of 2017 Restructuring charges and $1.6 million and $3.9 million, respectively of divestiture costs.