Note 4 - Restructuring - Pre Tax Restructuring Cost (Details) - Restructuring 2017 [Member] - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2020		Dec. 31, 2019		Dec. 31, 2018
Restructuring charges		$ 16,737	[1]	$ 32,341	[2]	$ 29,486	[3]
Continuing Operations [Member]
Restructuring charges		11,279		30,680		29,224
Discontinued Operations [Member]
Restructuring charges		5,458		1,661		262
Discontinued Operations, Disposed of by Sale [Member]
Restructuring charges		5,458
Cost of Revenues [Member]
Restructuring charges		2,021	[1]	2,338	[2]	1,881	[3]
Cost of Revenues [Member] | Continuing Operations [Member]
Restructuring charges		2,021		2,338		1,881
Cost of Revenues [Member] | Discontinued Operations [Member]
Restructuring charges				0		0
Cost of Revenues [Member] | Discontinued Operations, Disposed of by Sale [Member]
Restructuring charges		0
Operating Expense [Member]
Restructuring charges		5,950	[1]	9,924	[2]	13,155	[3]
Operating Expense [Member] | Continuing Operations [Member]
Restructuring charges		5,950		9,924		13,155
Operating Expense [Member] | Discontinued Operations [Member]
Restructuring charges				0		0
Operating Expense [Member] | Discontinued Operations, Disposed of by Sale [Member]
Restructuring charges		0
Restructuring and Related Charges [Member]
Restructuring charges		4,162	[1]	8,188	[2]	6,660	[3]
Restructuring and Related Charges [Member] | Continuing Operations [Member]
Restructuring charges		4,162		8,188		6,660
Restructuring and Related Charges [Member] | Discontinued Operations [Member]
Restructuring charges				0		0
Restructuring and Related Charges [Member] | Discontinued Operations, Disposed of by Sale [Member]
Restructuring charges		0
Goodwill Impairment [Member]
Restructuring charges	[3]					1,389
Goodwill Impairment [Member] | Continuing Operations [Member]
Restructuring charges						1,389
Goodwill Impairment [Member] | Discontinued Operations [Member]
Restructuring charges						0
Other Expense [Member]
Restructuring charges		(854)	[1]	10,230	[2]	3,970	[3]
Other Expense [Member] | Continuing Operations [Member]
Restructuring charges		(854)		10,230		3,970
Other Expense [Member] | Discontinued Operations [Member]
Restructuring charges				0		0
Other Expense [Member] | Discontinued Operations, Disposed of by Sale [Member]
Restructuring charges		0
Definite-lived Intangible Asset Impairment [Member]
Restructuring charges	[3]					2,169
Definite-lived Intangible Asset Impairment [Member] | Continuing Operations [Member]
Restructuring charges						2,169
Definite-lived Intangible Asset Impairment [Member] | Discontinued Operations [Member]
Restructuring charges						0
Income (Loss) from Discontinued Operations [Member]
Restructuring charges		5,458	[1]	1,661	[2]	262	[3]
Income (Loss) from Discontinued Operations [Member] | Discontinued Operations [Member]
Restructuring charges				1,661		262
Income (Loss) from Discontinued Operations [Member] | Discontinued Operations, Disposed of by Sale [Member]
Restructuring charges		5,458
Employee Severance [Member]
Restructuring charges		4,597		6,355		4,536
Employee Severance [Member] | Continuing Operations [Member]
Restructuring charges		4,026		5,802		4,302
Employee Severance [Member] | Discontinued Operations [Member]
Restructuring charges		571		553		234
Contract Termination [Member]
Restructuring charges		99		2,022		2,174
Contract Termination [Member] | Continuing Operations [Member]
Restructuring charges		(100)		1,788		2,174
Contract Termination [Member] | Discontinued Operations [Member]
Restructuring charges		199		234		0
Employee Relocation [Member]
Restructuring charges		270		653		184
Employee Relocation [Member] | Continuing Operations [Member]
Restructuring charges		236		598		184
Employee Relocation [Member] | Discontinued Operations [Member]
Restructuring charges		34		55		0
Other Restructuring [Member]
Restructuring charges		11,771	[4]	23,311	[5]	22,592	[6]
Other Restructuring [Member] | Continuing Operations [Member]
Restructuring charges		7,117	[4]	22,492	[5]	22,564	[6]
Other Restructuring [Member] | Discontinued Operations [Member]
Restructuring charges		4,654	[4]	819	[5]	28	[6]
Corporate, Non-Segment [Member]
Restructuring charges		3,203		6,041		1,637
Corporate, Non-Segment [Member] | Cost of Revenues [Member]
Restructuring charges		0		0		0
Corporate, Non-Segment [Member] | Operating Expense [Member]
Restructuring charges		2,360		3,444		1,317
Corporate, Non-Segment [Member] | Restructuring and Related Charges [Member]
Restructuring charges		324		1,783		320
Corporate, Non-Segment [Member] | Goodwill Impairment [Member]
Restructuring charges						0
Corporate, Non-Segment [Member] | Other Expense [Member]
Restructuring charges		519		814		0
Corporate, Non-Segment [Member] | Definite-lived Intangible Asset Impairment [Member]
Restructuring charges						0
Corporate, Non-Segment [Member] | Employee Severance [Member]
Restructuring charges		324		1,685		170
Corporate, Non-Segment [Member] | Contract Termination [Member]
Restructuring charges		0		98		150
Corporate, Non-Segment [Member] | Employee Relocation [Member]
Restructuring charges		0		0		0
Corporate, Non-Segment [Member] | Other Restructuring [Member]
Restructuring charges		2,879	[4]	4,258	[5]	1,317	[6]
Infrastructure Solutions [Member] | Operating Segments [Member]
Restructuring charges		(1,432)		15,371		18,532
Infrastructure Solutions [Member] | Operating Segments [Member] | Cost of Revenues [Member]
Restructuring charges		69		469		1,281
Infrastructure Solutions [Member] | Operating Segments [Member] | Operating Expense [Member]
Restructuring charges		(357)		5,349		7,291
Infrastructure Solutions [Member] | Operating Segments [Member] | Restructuring and Related Charges [Member]
Restructuring charges		194		1,729		5,221
Infrastructure Solutions [Member] | Operating Segments [Member] | Goodwill Impairment [Member]
Restructuring charges						1,389
Infrastructure Solutions [Member] | Operating Segments [Member] | Other Expense [Member]
Restructuring charges		(1,338)		7,824		2,480
Infrastructure Solutions [Member] | Operating Segments [Member] | Definite-lived Intangible Asset Impairment [Member]
Restructuring charges						870
Infrastructure Solutions [Member] | Operating Segments [Member] | Employee Severance [Member]
Restructuring charges		29		938		3,038
Infrastructure Solutions [Member] | Operating Segments [Member] | Contract Termination [Member]
Restructuring charges		66		601		1,999
Infrastructure Solutions [Member] | Operating Segments [Member] | Employee Relocation [Member]
Restructuring charges		99		190		184
Infrastructure Solutions [Member] | Operating Segments [Member] | Other Restructuring [Member]
Restructuring charges		(1,626)	[4]	13,642	[5]	13,311	[6]
Corrosion Protection [Member] | Operating Segments [Member]
Restructuring charges		9,508		9,268		9,055
Corrosion Protection [Member] | Operating Segments [Member] | Cost of Revenues [Member]
Restructuring charges		1,952		1,869		600
Corrosion Protection [Member] | Operating Segments [Member] | Operating Expense [Member]
Restructuring charges		3,947		1,131		4,547
Corrosion Protection [Member] | Operating Segments [Member] | Restructuring and Related Charges [Member]
Restructuring charges		3,644		4,676		1,119
Corrosion Protection [Member] | Operating Segments [Member] | Goodwill Impairment [Member]
Restructuring charges						0
Corrosion Protection [Member] | Operating Segments [Member] | Other Expense [Member]
Restructuring charges		(35)		1,592		1,490
Corrosion Protection [Member] | Operating Segments [Member] | Definite-lived Intangible Asset Impairment [Member]
Restructuring charges						1,299
Corrosion Protection [Member] | Operating Segments [Member] | Employee Severance [Member]
Restructuring charges		3,673		3,179		1,094
Corrosion Protection [Member] | Operating Segments [Member] | Contract Termination [Member]
Restructuring charges		(166)		1,089		25
Corrosion Protection [Member] | Operating Segments [Member] | Employee Relocation [Member]
Restructuring charges		137		408		0
Corrosion Protection [Member] | Operating Segments [Member] | Other Restructuring [Member]
Restructuring charges		$ 5,864	[4]	$ 4,592	[5]	$ 7,936	[6]

[1] Total pre-tax restructuring charges include cash charges of $12.0 million and non-cash charges of $4.7 million. Cash charges consist of charges incurred during the year that will be settled in cash, either during the current period or future periods.

[2] Total pre-tax restructuring charges include cash charges of $19.5 million and non-cash charges of $12.8 million. Cash charges consist of charges incurred during the year that will be settled in cash, either during the current period or future periods.

[3] Total pre-tax restructuring charges include cash charges of $12.1 million and non-cash charges of $17.4 million. Cash charges consist of charges incurred during the year that will be settled in cash, either during the current period or future periods.

[4] Includes 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 exiting a small business in discontinued operations.

[5] Includes charges primarily related to certain wind-down costs, inventory obsolescence, fixed asset disposals, release of cumulative currency translation adjustments and other restructuring-related costs in connection with exiting or divesting the CIPP operations in Europe and Australia, exiting the cathodic protection operations in the Middle East and right-sizing the cathodic protection services operation in North America.

[6] Includes charges primarily related to certain wind-down costs, allowances for accounts receivable, fixed asset disposals and other restructuring-related costs in connection with exiting non-pipe-related contract applications for the Tyfo® system in North America, divesting the CIPP operations in Australia and Denmark, and exiting the cathodic protection operations in the Middle East. Amounts also include goodwill and definite-lived intangible asset impairments related to Denmark and definite-lived intangible asset impairments related to the cathodic protection operations in the Middle East.