Note 4 - Restructuring - Pre Tax Restructuring Cost (Details) - Restructuring 2017 [Member] - USD ($) $ in Thousands	3 Months Ended				6 Months Ended
	Jun. 30, 2020		Jun. 30, 2019		Jun. 30, 2020		Jun. 30, 2019
Restructuring charges	$ 4,833	[1]	$ 6,516	[2]	$ 8,456	[3]	$ 9,382	[4]
Cost of Revenues [Member]
Restructuring charges	(79)	[1]	396	[2]	244	[3]	470	[4]
Operating Expense [Member]
Restructuring charges	2,966	[1]	2,205	[2]	4,347	[3]	3,735	[4]
Goodwill Impairment [Member]
Restructuring charges	1,258	[1]	0	[2]	1,258	[3]	0	[4]
Definite-lived Intangible Asset Impairment [Member]
Restructuring charges	957	[1]	0	[2]	957	[3]	0	[4]
Restructuring and Related Charges [Member]
Restructuring charges	664	[1]	2,974	[2]	1,952	[3]	4,060	[4]
Other Expense [Member]
Restructuring charges	(933)	[1]	941	[2]	(302)	[3]	1,117	[4]
Employee Severance [Member]
Restructuring charges	350		2,132		1,488		2,627
Contract Termination [Member]
Restructuring charges	211		698		327		1,238
Employee Relocation [Member]
Restructuring charges	103		144		137		195
Other Restructuring [Member]
Restructuring charges	4,169	[5]	3,542	[5]	6,504	[6]	5,322	[6]
Operating Segments [Member] | Infrastructure Solutions [Member]
Restructuring charges	(45)		2,155		316		4,657
Operating Segments [Member] | Infrastructure Solutions [Member] | Cost of Revenues [Member]
Restructuring charges	52		(67)		69		(92)
Operating Segments [Member] | Infrastructure Solutions [Member] | Operating Expense [Member]
Restructuring charges	(133)		976		316		2,322
Operating Segments [Member] | Infrastructure Solutions [Member] | Goodwill Impairment [Member]
Restructuring charges	0		0		0		0
Operating Segments [Member] | Infrastructure Solutions [Member] | Definite-lived Intangible Asset Impairment [Member]
Restructuring charges	0		0		0		0
Operating Segments [Member] | Infrastructure Solutions [Member] | Restructuring and Related Charges [Member]
Restructuring charges	154		459		154		1,217
Operating Segments [Member] | Infrastructure Solutions [Member] | Other Expense [Member]
Restructuring charges	(118)		787		(223)		1,210
Operating Segments [Member] | Infrastructure Solutions [Member] | Employee Severance [Member]
Restructuring charges	118		551		118		833
Operating Segments [Member] | Infrastructure Solutions [Member] | Contract Termination [Member]
Restructuring charges	36		(92)		36		333
Operating Segments [Member] | Infrastructure Solutions [Member] | Employee Relocation [Member]
Restructuring charges	0		0		0		51
Operating Segments [Member] | Infrastructure Solutions [Member] | Other Restructuring [Member]
Restructuring charges	(199)	[5]	1,696	[5]	162	[6]	3,440	[6]
Operating Segments [Member] | Corrosion Protection [Member]
Restructuring charges	484		3,449		2,380		3,425
Operating Segments [Member] | Corrosion Protection [Member] | Cost of Revenues [Member]
Restructuring charges	(131)		463		175		562
Operating Segments [Member] | Corrosion Protection [Member] | Operating Expense [Member]
Restructuring charges	1,091		331		1,642		268
Operating Segments [Member] | Corrosion Protection [Member] | Goodwill Impairment [Member]
Restructuring charges	0		0		0		0
Operating Segments [Member] | Corrosion Protection [Member] | Definite-lived Intangible Asset Impairment [Member]
Restructuring charges	0		0		0		0
Operating Segments [Member] | Corrosion Protection [Member] | Restructuring and Related Charges [Member]
Restructuring charges	384		2,509		1,301		2,696
Operating Segments [Member] | Corrosion Protection [Member] | Other Expense [Member]
Restructuring charges	(860)		146		(738)		(101)
Operating Segments [Member] | Corrosion Protection [Member] | Employee Severance [Member]
Restructuring charges	106		1,575		969		1,745
Operating Segments [Member] | Corrosion Protection [Member] | Contract Termination [Member]
Restructuring charges	175		790		229		807
Operating Segments [Member] | Corrosion Protection [Member] | Employee Relocation [Member]
Restructuring charges	103		144		103		144
Operating Segments [Member] | Corrosion Protection [Member] | Other Restructuring [Member]
Restructuring charges	100	[5]	940	[5]	1,079	[6]	729	[6]
Operating Segments [Member] | Energy Services [Member]
Restructuring charges	3,454		6		3,550		40
Operating Segments [Member] | Energy Services [Member] | Cost of Revenues [Member]
Restructuring charges	0		0		0		0
Operating Segments [Member] | Energy Services [Member] | Operating Expense [Member]
Restructuring charges	1,170		0		1,170		0
Operating Segments [Member] | Energy Services [Member] | Goodwill Impairment [Member]
Restructuring charges	1,258		0		1,258		0
Operating Segments [Member] | Energy Services [Member] | Definite-lived Intangible Asset Impairment [Member]
Restructuring charges	957		0		957		0
Operating Segments [Member] | Energy Services [Member] | Restructuring and Related Charges [Member]
Restructuring charges	69		6		165		40
Operating Segments [Member] | Energy Services [Member] | Other Expense [Member]
Restructuring charges	0		0		0		0
Operating Segments [Member] | Energy Services [Member] | Employee Severance [Member]
Restructuring charges	69		6		69		40
Operating Segments [Member] | Energy Services [Member] | Contract Termination [Member]
Restructuring charges	0		0		62		0
Operating Segments [Member] | Energy Services [Member] | Employee Relocation [Member]
Restructuring charges	0		0		34		0
Operating Segments [Member] | Energy Services [Member] | Other Restructuring [Member]
Restructuring charges	3,385	[5]	0	[5]	3,385	[6]	0	[6]
Corporate, Non-Segment [Member]
Restructuring charges	940		906		2,210		1,260
Corporate, Non-Segment [Member] | Cost of Revenues [Member]
Restructuring charges	0		0		0		0
Corporate, Non-Segment [Member] | Operating Expense [Member]
Restructuring charges	838		898		1,219		1,145
Corporate, Non-Segment [Member] | Goodwill Impairment [Member]
Restructuring charges	0		0		0		0
Corporate, Non-Segment [Member] | Definite-lived Intangible Asset Impairment [Member]
Restructuring charges	0		0		0		0
Corporate, Non-Segment [Member] | Restructuring and Related Charges [Member]
Restructuring charges	57		0		332		107
Corporate, Non-Segment [Member] | Other Expense [Member]
Restructuring charges	45		8		659		8
Corporate, Non-Segment [Member] | Employee Severance [Member]
Restructuring charges	57		0		332		9
Corporate, Non-Segment [Member] | Contract Termination [Member]
Restructuring charges	0		0		0		98
Corporate, Non-Segment [Member] | Employee Relocation [Member]
Restructuring charges	0		0		0		0
Corporate, Non-Segment [Member] | Other Restructuring [Member]
Restructuring charges	$ 883	[5]	$ 906	[5]	$ 1,878	[6]	$ 1,153	[6]

[1] Total pre-tax restructuring charges for the quarter ended June 30, 2020, include cash charges of $2.6 million and non-cash charges of $2.2 million. Cash charges consist of charges incurred during the quarter that will be settled in cash, either during the current period or future periods.

[2] Total pre-tax restructuring charges for the quarter ended June 30, 2019, include cash charges of $5.4 million and non-cash charges of $1.1 million. Cash charges consist of charges incurred during the quarter that will be settled in cash, either during the current period or future periods.

[3] Total pre-tax restructuring charges for the six months ended June 30, 2020, include cash charges of $5.8 million and non-cash charges of $2.7 million. Cash charges consist of charges incurred during the quarter that will be settled in cash, either during the current period or future periods.

[4] Total pre-tax restructuring charges for the six months ended June 30, 2019, include cash charges of $8.5 million and non-cash charges of $0.9 million. Cash charges consist of charges incurred during the quarter that will be settled in cash, either during the current period or future periods.

[5] For the quarter ended June 30, 2020, charges primarily related to certain wind-down costs, allowances for accounts receivable, fixed asset disposals, release of cumulative currency translation adjustments and other restructuring-related costs in connection with optimizing the cathodic protection operations in North America, exiting the CIPP operations in Europe, disposing of certain international businesses and other cost savings initiatives. Amounts also include goodwill and definite-lived intangible asset impairments related to the exiting P2S. For the quarter ended June 30, 2019, charges primarily related to certain wind-down costs, allowances for accounts receivable, fixed asset disposals, and other restructuring-related costs in connection with exiting the CIPP operations in Europe, exiting the cathodic protection operations in the Middle East and other cost savings initiatives.

[6] For the six months ended June 30, 2020, charges primarily related to certain wind-down costs, allowances for accounts receivable, fixed asset disposals, release of cumulative currency translation adjustments and other restructuring-related costs in connection with optimizing the cathodic protection operations in North America, exiting the CIPP operations in Europe, disposing of certain international businesses and other cost savings initiatives. Amounts also include goodwill and definite-lived intangible asset impairments related to the exiting P2S. For the six months ended June 30, 2019, charges primarily related to certain wind-down costs, allowances for accounts receivable, fixed asset disposals and other restructuring-related costs in connection with exiting the CIPP operations in Europe, exiting the cathodic protection operations in the Middle East and other cost savings initiatives.