Note 4 - Restructuring - Pre-tax Restructuring Cost (Details) - USD ($) $ in Thousands		3 Months Ended								12 Months Ended
		Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019		Dec. 31, 2018		Dec. 31, 2017
Restructuring charges		$ 14,300	$ 8,600	$ 6,500	$ 2,900	$ 13,900	$ 7,400	$ 2,900	$ 5,200
Restructuring 2017 [Member]
Restructuring charges										$ 32,341		$ 29,486	[1]	$ 23,743	[2]
Restructuring 2017 [Member] | Cost of Revenues [Member]
Restructuring charges												1,881	[1]	45	[2]
Restructuring 2017 [Member] | Operating Expense [Member]
Restructuring charges												13,183	[1]	10,884	[2]
Restructuring 2017 [Member] | Restructuring and Related Charges [Member]
Restructuring charges												6,894	[1]	12,814	[2]
Restructuring 2017 [Member] | Other Expense [Member]
Restructuring charges	[1],[3]											3,970
Restructuring 2017 [Member] | Goodwill Impairment [Member]
Restructuring charges	[1]											1,389
Restructuring 2017 [Member] | Definite-lived Intangible Asset Impairment [Member]
Restructuring charges	[1]											2,169
Restructuring 2017 [Member] | Employee Severance [Member]
Restructuring charges										6,355		4,536
Restructuring 2017 [Member] | Contract Termination [Member]
Restructuring charges										2,022		2,174
Restructuring 2017 [Member] | Employee Relocation [Member]
Restructuring charges										653		184
Restructuring 2017 [Member] | Other Restructuring [Member]
Restructuring charges										23,311	[4]	22,592	[5]
Restructuring 2017 [Member] | Operating Segments [Member] | Infrastructure Solutions [Member]
Restructuring charges										15,371		18,532		17,279
Restructuring 2017 [Member] | Operating Segments [Member] | Infrastructure Solutions [Member] | Cost of Revenues [Member]
Restructuring charges												1,281		30
Restructuring 2017 [Member] | Operating Segments [Member] | Infrastructure Solutions [Member] | Operating Expense [Member]
Restructuring charges												7,291		8,404
Restructuring 2017 [Member] | Operating Segments [Member] | Infrastructure Solutions [Member] | Restructuring and Related Charges [Member]
Restructuring charges												5,221		8,845
Restructuring 2017 [Member] | Operating Segments [Member] | Infrastructure Solutions [Member] | Other Expense [Member]
Restructuring charges	[1],[3]											2,480
Restructuring 2017 [Member] | Operating Segments [Member] | Infrastructure Solutions [Member] | Goodwill Impairment [Member]
Restructuring charges												1,389
Restructuring 2017 [Member] | Operating Segments [Member] | Infrastructure Solutions [Member] | Definite-lived Intangible Asset Impairment [Member]
Restructuring charges												870
Restructuring 2017 [Member] | Operating Segments [Member] | Infrastructure Solutions [Member] | Employee Severance [Member]
Restructuring charges										938		3,038
Restructuring 2017 [Member] | Operating Segments [Member] | Infrastructure Solutions [Member] | Contract Termination [Member]
Restructuring charges										601		1,999
Restructuring 2017 [Member] | Operating Segments [Member] | Infrastructure Solutions [Member] | Employee Relocation [Member]
Restructuring charges										190		184
Restructuring 2017 [Member] | Operating Segments [Member] | Infrastructure Solutions [Member] | Other Restructuring [Member]
Restructuring charges										13,642	[4]	13,311	[5]
Restructuring 2017 [Member] | Operating Segments [Member] | Corrosion Protection [Member]
Restructuring charges										9,268		9,055		4,860
Restructuring 2017 [Member] | Operating Segments [Member] | Corrosion Protection [Member] | Cost of Revenues [Member]
Restructuring charges												600		15
Restructuring 2017 [Member] | Operating Segments [Member] | Corrosion Protection [Member] | Operating Expense [Member]
Restructuring charges												4,547		1,507
Restructuring 2017 [Member] | Operating Segments [Member] | Corrosion Protection [Member] | Restructuring and Related Charges [Member]
Restructuring charges												1,119		3,338
Restructuring 2017 [Member] | Operating Segments [Member] | Corrosion Protection [Member] | Other Expense [Member]
Restructuring charges	[1],[3]											1,490
Restructuring 2017 [Member] | Operating Segments [Member] | Corrosion Protection [Member] | Goodwill Impairment [Member]
Restructuring charges												0
Restructuring 2017 [Member] | Operating Segments [Member] | Corrosion Protection [Member] | Definite-lived Intangible Asset Impairment [Member]
Restructuring charges												1,299
Restructuring 2017 [Member] | Operating Segments [Member] | Corrosion Protection [Member] | Employee Severance [Member]
Restructuring charges										3,179		1,094
Restructuring 2017 [Member] | Operating Segments [Member] | Corrosion Protection [Member] | Contract Termination [Member]
Restructuring charges										1,089		25
Restructuring 2017 [Member] | Operating Segments [Member] | Corrosion Protection [Member] | Employee Relocation [Member]
Restructuring charges										408		0
Restructuring 2017 [Member] | Operating Segments [Member] | Corrosion Protection [Member] | Other Restructuring [Member]
Restructuring charges										4,592	[4]	7,936	[5]
Restructuring 2017 [Member] | Operating Segments [Member] | Energy Services [Member]
Restructuring charges										1,661		262
Restructuring 2017 [Member] | Operating Segments [Member] | Energy Services [Member] | Cost of Revenues [Member]
Restructuring charges												0
Restructuring 2017 [Member] | Operating Segments [Member] | Energy Services [Member] | Operating Expense [Member]
Restructuring charges												28
Restructuring 2017 [Member] | Operating Segments [Member] | Energy Services [Member] | Restructuring and Related Charges [Member]
Restructuring charges												234
Restructuring 2017 [Member] | Operating Segments [Member] | Energy Services [Member] | Other Expense [Member]
Restructuring charges	[1],[3]											0
Restructuring 2017 [Member] | Operating Segments [Member] | Energy Services [Member] | Goodwill Impairment [Member]
Restructuring charges												0
Restructuring 2017 [Member] | Operating Segments [Member] | Energy Services [Member] | Definite-lived Intangible Asset Impairment [Member]
Restructuring charges												0
Restructuring 2017 [Member] | Operating Segments [Member] | Energy Services [Member] | Employee Severance [Member]
Restructuring charges										553		234
Restructuring 2017 [Member] | Operating Segments [Member] | Energy Services [Member] | Contract Termination [Member]
Restructuring charges										234		0
Restructuring 2017 [Member] | Operating Segments [Member] | Energy Services [Member] | Employee Relocation [Member]
Restructuring charges										55		0
Restructuring 2017 [Member] | Operating Segments [Member] | Energy Services [Member] | Other Restructuring [Member]
Restructuring charges										819	[4]	28	[5]
Restructuring 2017 [Member] | Corporate, Non-Segment [Member]
Restructuring charges										6,041		1,637		1,604
Restructuring 2017 [Member] | Corporate, Non-Segment [Member] | Cost of Revenues [Member]
Restructuring charges												0		0
Restructuring 2017 [Member] | Corporate, Non-Segment [Member] | Operating Expense [Member]
Restructuring charges												1,317		973
Restructuring 2017 [Member] | Corporate, Non-Segment [Member] | Restructuring and Related Charges [Member]
Restructuring charges												320		631
Restructuring 2017 [Member] | Corporate, Non-Segment [Member] | Other Expense [Member]
Restructuring charges	[1],[3]											0
Restructuring 2017 [Member] | Corporate, Non-Segment [Member] | Goodwill Impairment [Member]
Restructuring charges												0
Restructuring 2017 [Member] | Corporate, Non-Segment [Member] | Definite-lived Intangible Asset Impairment [Member]
Restructuring charges												0
Restructuring 2017 [Member] | Corporate, Non-Segment [Member] | Employee Severance [Member]
Restructuring charges										1,685		170
Restructuring 2017 [Member] | Corporate, Non-Segment [Member] | Contract Termination [Member]
Restructuring charges										98		150
Restructuring 2017 [Member] | Corporate, Non-Segment [Member] | Employee Relocation [Member]
Restructuring charges										0		0
Restructuring 2017 [Member] | Corporate, Non-Segment [Member] | Other Restructuring [Member]
Restructuring charges										4,258	[4]	1,317	[5]
Restructuring 2016 [Member]
Restructuring charges										32,341	[6]	29,486		23,743
Restructuring 2016 [Member] | Cost of Revenues [Member]
Restructuring charges	[6],[7]									2,338
Restructuring 2016 [Member] | Operating Expense [Member]
Restructuring charges	[6]									10,743
Restructuring 2016 [Member] | Restructuring and Related Charges [Member]
Restructuring charges	[6]									9,030
Restructuring 2016 [Member] | Other Expense [Member]
Restructuring charges	[6],[7]									10,230
Restructuring 2016 [Member] | Employee Severance [Member]
Restructuring charges										6,355		4,536		7,345
Restructuring 2016 [Member] | Contract Termination [Member]
Restructuring charges										2,022		2,174		5,320
Restructuring 2016 [Member] | Employee Relocation [Member]
Restructuring charges										653		184		147
Restructuring 2016 [Member] | Other Restructuring [Member]
Restructuring charges										23,311		$ 22,592		10,931	[8]
Restructuring 2016 [Member] | Operating Segments [Member] | Infrastructure Solutions [Member]
Restructuring charges										15,371				17,279
Restructuring 2016 [Member] | Operating Segments [Member] | Infrastructure Solutions [Member] | Cost of Revenues [Member]
Restructuring charges										469
Restructuring 2016 [Member] | Operating Segments [Member] | Infrastructure Solutions [Member] | Operating Expense [Member]
Restructuring charges										5,349
Restructuring 2016 [Member] | Operating Segments [Member] | Infrastructure Solutions [Member] | Restructuring and Related Charges [Member]
Restructuring charges										1,729
Restructuring 2016 [Member] | Operating Segments [Member] | Infrastructure Solutions [Member] | Other Expense [Member]
Restructuring charges	[7]									7,824
Restructuring 2016 [Member] | Operating Segments [Member] | Infrastructure Solutions [Member] | Employee Severance [Member]
Restructuring charges														4,274
Restructuring 2016 [Member] | Operating Segments [Member] | Infrastructure Solutions [Member] | Contract Termination [Member]
Restructuring charges														4,545
Restructuring 2016 [Member] | Operating Segments [Member] | Infrastructure Solutions [Member] | Employee Relocation [Member]
Restructuring charges														26
Restructuring 2016 [Member] | Operating Segments [Member] | Infrastructure Solutions [Member] | Other Restructuring [Member]
Restructuring charges	[8]													8,434
Restructuring 2016 [Member] | Operating Segments [Member] | Corrosion Protection [Member]
Restructuring charges										9,268				4,860
Restructuring 2016 [Member] | Operating Segments [Member] | Corrosion Protection [Member] | Cost of Revenues [Member]
Restructuring charges										1,869
Restructuring 2016 [Member] | Operating Segments [Member] | Corrosion Protection [Member] | Operating Expense [Member]
Restructuring charges										1,131
Restructuring 2016 [Member] | Operating Segments [Member] | Corrosion Protection [Member] | Restructuring and Related Charges [Member]
Restructuring charges										4,676
Restructuring 2016 [Member] | Operating Segments [Member] | Corrosion Protection [Member] | Other Expense [Member]
Restructuring charges	[7]									1,592
Restructuring 2016 [Member] | Operating Segments [Member] | Corrosion Protection [Member] | Employee Severance [Member]
Restructuring charges														2,442
Restructuring 2016 [Member] | Operating Segments [Member] | Corrosion Protection [Member] | Contract Termination [Member]
Restructuring charges														775
Restructuring 2016 [Member] | Operating Segments [Member] | Corrosion Protection [Member] | Employee Relocation [Member]
Restructuring charges														121
Restructuring 2016 [Member] | Operating Segments [Member] | Corrosion Protection [Member] | Other Restructuring [Member]
Restructuring charges	[8]													1,522
Restructuring 2016 [Member] | Operating Segments [Member] | Energy Services [Member]
Restructuring charges										1,661
Restructuring 2016 [Member] | Operating Segments [Member] | Energy Services [Member] | Cost of Revenues [Member]
Restructuring charges										0
Restructuring 2016 [Member] | Operating Segments [Member] | Energy Services [Member] | Operating Expense [Member]
Restructuring charges										819
Restructuring 2016 [Member] | Operating Segments [Member] | Energy Services [Member] | Restructuring and Related Charges [Member]
Restructuring charges										842
Restructuring 2016 [Member] | Operating Segments [Member] | Energy Services [Member] | Other Expense [Member]
Restructuring charges	[7]									0
Restructuring 2016 [Member] | Corporate, Non-Segment [Member]
Restructuring charges										6,041
Restructuring 2016 [Member] | Corporate, Non-Segment [Member] | Cost of Revenues [Member]
Restructuring charges										0
Restructuring 2016 [Member] | Corporate, Non-Segment [Member] | Operating Expense [Member]
Restructuring charges										3,444
Restructuring 2016 [Member] | Corporate, Non-Segment [Member] | Restructuring and Related Charges [Member]
Restructuring charges										1,783
Restructuring 2016 [Member] | Corporate, Non-Segment [Member] | Other Expense [Member]
Restructuring charges	[7]									$ 814
Restructuring 2016 [Member] | Corporate, Non-Segment [Member] | Energy Services [Member]
Restructuring charges														1,604
Restructuring 2016 [Member] | Corporate, Non-Segment [Member] | Energy Services [Member] | Employee Severance [Member]
Restructuring charges														629
Restructuring 2016 [Member] | Corporate, Non-Segment [Member] | Energy Services [Member] | Contract Termination [Member]
Restructuring charges														0
Restructuring 2016 [Member] | Corporate, Non-Segment [Member] | Energy Services [Member] | Employee Relocation [Member]
Restructuring charges														0
Restructuring 2016 [Member] | Corporate, Non-Segment [Member] | Energy Services [Member] | Other Restructuring [Member]
Restructuring charges	[8]													$ 975

[1] 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.

[2] Total pre-tax restructuring charges include cash charges of $13.6 million and non-cash charges of $10.1 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] Includes charges related to the loss on disposal of restructured entities, including the release of cumulative currency translation adjustments resulting from those disposals.

[4] 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.

[5] 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.

[6] 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.

[7] Includes charges related to the loss on disposal of restructured entities, including the release of cumulative currency translation adjustments resulting from those disposals.

[8] Includes charges primarily related to exiting non-pipe-related applications for the Tyfo system in North America and right-sizing the cathodic protection services operation in Canada, inclusive of wind-down costs, professional fees, patent write offs, fixed asset disposals and certain other restructuring and related charges.