Note 4 - Restructuring - Pre Tax Restructuring Cost (Details) - Restructuring 2017 [Member] - USD ($) $ in Thousands	3 Months Ended				9 Months Ended
	Sep. 30, 2020		Sep. 30, 2019		Sep. 30, 2020		Sep. 30, 2019
Restructuring charges	$ 4,243	[1]	$ 8,607	[2]	$ 12,699	[3]	$ 17,989	[4]
Cost of Revenues [Member]
Restructuring charges	1,830	[1]	(33)	[2]	2,074	[3]	437	[4]
Operating Expense [Member]
Restructuring charges	1,546	[1]	1,860	[2]	5,893	[3]	5,595	[4]
Restructuring and Related Charges [Member]
Restructuring charges	2,335	[1]	1,435	[2]	4,287	[3]	5,495	[4]
Goodwill Impairment [Member]
Restructuring charges					1,258	[3]	0	[4]
Other Expense [Member]
Restructuring charges	(1,468)	[1]	5,345	[2]	(1,770)	[3]	6,462	[4]
Definite-lived Intangible Asset Impairment [Member]
Restructuring charges					957	[3]	0	[4]
Employee Severance [Member]
Restructuring charges	2,038		1,147		3,526		3,774
Contract Termination [Member]
Restructuring charges	274		209		601		1,447
Employee Relocation [Member]
Restructuring charges	23		79		160		274
Other Restructuring [Member]
Restructuring charges	1,908	[5]	7,172	[5]	8,412	[6]	12,494	[6]
Operating Segments [Member] | Infrastructure Solutions [Member]
Restructuring charges	(1,475)		5,904		(1,159)		10,561
Operating Segments [Member] | Infrastructure Solutions [Member] | Cost of Revenues [Member]
Restructuring charges	0		(30)		69		(122)
Operating Segments [Member] | Infrastructure Solutions [Member] | Operating Expense [Member]
Restructuring charges	(87)		748		229		3,070
Operating Segments [Member] | Infrastructure Solutions [Member] | Restructuring and Related Charges [Member]
Restructuring charges	(89)		490		65		1,707
Operating Segments [Member] | Infrastructure Solutions [Member] | Goodwill Impairment [Member]
Restructuring charges					0		0
Operating Segments [Member] | Infrastructure Solutions [Member] | Other Expense [Member]
Restructuring charges	(1,299)		4,696		(1,522)		5,906
Operating Segments [Member] | Infrastructure Solutions [Member] | Definite-lived Intangible Asset Impairment [Member]
Restructuring charges					0		0
Operating Segments [Member] | Infrastructure Solutions [Member] | Employee Severance [Member]
Restructuring charges	(89)		210		29		1,043
Operating Segments [Member] | Infrastructure Solutions [Member] | Contract Termination [Member]
Restructuring charges	0		201		36		534
Operating Segments [Member] | Infrastructure Solutions [Member] | Employee Relocation [Member]
Restructuring charges	0		79		0		130
Operating Segments [Member] | Infrastructure Solutions [Member] | Other Restructuring [Member]
Restructuring charges	(1,386)	[5]	5,414	[5]	(1,224)	[6]	8,854	[6]
Operating Segments [Member] | Corrosion Protection [Member]
Restructuring charges	4,488		918		6,868		4,343
Operating Segments [Member] | Corrosion Protection [Member] | Cost of Revenues [Member]
Restructuring charges	1,830		(3)		2,005		559
Operating Segments [Member] | Corrosion Protection [Member] | Operating Expense [Member]
Restructuring charges	527		315		2,169		583
Operating Segments [Member] | Corrosion Protection [Member] | Restructuring and Related Charges [Member]
Restructuring charges	2,163		455		3,464		3,151
Operating Segments [Member] | Corrosion Protection [Member] | Goodwill Impairment [Member]
Restructuring charges					0		0
Operating Segments [Member] | Corrosion Protection [Member] | Other Expense [Member]
Restructuring charges	(32)		151		(770)		50
Operating Segments [Member] | Corrosion Protection [Member] | Definite-lived Intangible Asset Impairment [Member]
Restructuring charges					0		0
Operating Segments [Member] | Corrosion Protection [Member] | Employee Severance [Member]
Restructuring charges	1,952		447		2,921		2,192
Operating Segments [Member] | Corrosion Protection [Member] | Contract Termination [Member]
Restructuring charges	188		8		417		815
Operating Segments [Member] | Corrosion Protection [Member] | Employee Relocation [Member]
Restructuring charges	23		0		126		144
Operating Segments [Member] | Corrosion Protection [Member] | Other Restructuring [Member]
Restructuring charges	2,325	[5]	463	[5]	3,404	[6]	1,192	[6]
Operating Segments [Member] | Energy Services [Member]
Restructuring charges	869		139		4,419		179
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	611		65		1,781		65
Operating Segments [Member] | Energy Services [Member] | Restructuring and Related Charges [Member]
Restructuring charges	258		74		423		114
Operating Segments [Member] | Energy Services [Member] | Goodwill Impairment [Member]
Restructuring charges					1,258		0
Operating Segments [Member] | Energy Services [Member] | Other Expense [Member]
Restructuring charges	0		0		0		0
Operating Segments [Member] | Energy Services [Member] | Definite-lived Intangible Asset Impairment [Member]
Restructuring charges					957		0
Operating Segments [Member] | Energy Services [Member] | Employee Severance [Member]
Restructuring charges	172		74		241		114
Operating Segments [Member] | Energy Services [Member] | Contract Termination [Member]
Restructuring charges	86		0		148		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	611	[5]	65	[5]	3,996	[6]	65	[6]
Corporate, Non-Segment [Member]
Restructuring charges	361		1,646		2,571		2,906
Corporate, Non-Segment [Member] | Cost of Revenues [Member]
Restructuring charges	0		0		0		0
Corporate, Non-Segment [Member] | Operating Expense [Member]
Restructuring charges	495		732		1,714		1,877
Corporate, Non-Segment [Member] | Restructuring and Related Charges [Member]
Restructuring charges	3		416		335		523
Corporate, Non-Segment [Member] | Goodwill Impairment [Member]
Restructuring charges					0		0
Corporate, Non-Segment [Member] | Other Expense [Member]
Restructuring charges	(137)		498		522		506
Corporate, Non-Segment [Member] | Definite-lived Intangible Asset Impairment [Member]
Restructuring charges					0		0
Corporate, Non-Segment [Member] | Employee Severance [Member]
Restructuring charges	3		416		335		425
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	$ 358	[5]	$ 1,230	[5]	$ 2,236	[6]	$ 2,383	[6]

[1] Total pre-tax restructuring charges for the quarter ended September 30, 2020 include cash charges of $3.7 million and non-cash charges of $0.5 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 September 30, 2019 include cash charges of $3.1 million and non-cash charges of $5.5 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 nine months ended September 30, 2020 include cash charges of $9.5 million and non-cash charges of $3.2 million. Cash charges consist of charges incurred during the quarter that will be settled in cash, either during the current period or future periods.

[4] Total pre-tax restructuring charges for the nine months ended September 30, 2019 include cash charges of $11.6 million and non-cash charges of $6.4 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 September 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, disposing of certain international businesses and other cost savings initiatives. For the quarter ended September 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 nine months ended September 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 nine months ended September 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.