Note 4 - Restructuring - Pre Tax Restructuring Cost (Details) - Restructuring 2017 [Member] - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2020		Mar. 31, 2019
Restructuring charges		$ 3,623	[1]	$ 2,866	[2]
Cost of Revenues [Member]
Restructuring charges		323	[1]	74	[2]
Operating Expense [Member]
Restructuring charges		1,381	[1]	1,530	[2]
Restructuring and Related Charges [Member]
Restructuring charges		1,288	[1]	1,086	[2]
Other Expense [Member]
Restructuring charges		631	[1]	176	[2]
Employee Severance [Member]
Restructuring charges		1,138		495
Contract Termination [Member]
Restructuring charges		116		540
Employee Relocation [Member]
Restructuring charges		34		51
Other Restructuring [Member]
Restructuring charges	[3]	2,335		1,780
Operating Segments [Member] | Infrastructure Solutions [Member]
Restructuring charges		361		2,502
Operating Segments [Member] | Infrastructure Solutions [Member] | Cost of Revenues [Member]
Restructuring charges		17		(25)
Operating Segments [Member] | Infrastructure Solutions [Member] | Operating Expense [Member]
Restructuring charges		449		1,346
Operating Segments [Member] | Infrastructure Solutions [Member] | Restructuring and Related Charges [Member]
Restructuring charges		0		758
Operating Segments [Member] | Infrastructure Solutions [Member] | Other Expense [Member]
Restructuring charges		(105)		423
Operating Segments [Member] | Infrastructure Solutions [Member] | Employee Severance [Member]
Restructuring charges		0		282
Operating Segments [Member] | Infrastructure Solutions [Member] | Contract Termination [Member]
Restructuring charges		0		425
Operating Segments [Member] | Infrastructure Solutions [Member] | Employee Relocation [Member]
Restructuring charges		0		51
Operating Segments [Member] | Infrastructure Solutions [Member] | Other Restructuring [Member]
Restructuring charges	[3]	361		1,744
Operating Segments [Member] | Corrosion Protection [Member]
Restructuring charges		1,896		(24)
Operating Segments [Member] | Corrosion Protection [Member] | Cost of Revenues [Member]
Restructuring charges		306		99
Operating Segments [Member] | Corrosion Protection [Member] | Operating Expense [Member]
Restructuring charges		551		(63)
Operating Segments [Member] | Corrosion Protection [Member] | Restructuring and Related Charges [Member]
Restructuring charges		917		187
Operating Segments [Member] | Corrosion Protection [Member] | Other Expense [Member]
Restructuring charges		122		(247)
Operating Segments [Member] | Corrosion Protection [Member] | Employee Severance [Member]
Restructuring charges		863		170
Operating Segments [Member] | Corrosion Protection [Member] | Contract Termination [Member]
Restructuring charges		54		17
Operating Segments [Member] | Corrosion Protection [Member] | Employee Relocation [Member]
Restructuring charges		0		0
Operating Segments [Member] | Corrosion Protection [Member] | Other Restructuring [Member]
Restructuring charges	[3]	979		(211)
Operating Segments [Member] | Energy Services [Member]
Restructuring charges		96		34
Operating Segments [Member] | Energy Services [Member] | Cost of Revenues [Member]
Restructuring charges		0		0
Operating Segments [Member] | Energy Services [Member] | Operating Expense [Member]
Restructuring charges		0		0
Operating Segments [Member] | Energy Services [Member] | Restructuring and Related Charges [Member]
Restructuring charges		96		34
Operating Segments [Member] | Energy Services [Member] | Other Expense [Member]
Restructuring charges		0		0
Operating Segments [Member] | Energy Services [Member] | Employee Severance [Member]
Restructuring charges		0		34
Operating Segments [Member] | Energy Services [Member] | Contract Termination [Member]
Restructuring charges		62		0
Operating Segments [Member] | Energy Services [Member] | Employee Relocation [Member]
Restructuring charges		34		0
Operating Segments [Member] | Energy Services [Member] | Other Restructuring [Member]
Restructuring charges	[3]	0		0
Corporate, Non-Segment [Member]
Restructuring charges		1,270		354
Corporate, Non-Segment [Member] | Cost of Revenues [Member]
Restructuring charges		0		0
Corporate, Non-Segment [Member] | Operating Expense [Member]
Restructuring charges		381		247
Corporate, Non-Segment [Member] | Restructuring and Related Charges [Member]
Restructuring charges		275		107
Corporate, Non-Segment [Member] | Other Expense [Member]
Restructuring charges		614		0
Corporate, Non-Segment [Member] | Employee Severance [Member]
Restructuring charges		275		9
Corporate, Non-Segment [Member] | Contract Termination [Member]
Restructuring charges		0		98
Corporate, Non-Segment [Member] | Employee Relocation [Member]
Restructuring charges		0		0
Corporate, Non-Segment [Member] | Other Restructuring [Member]
Restructuring charges	[3]	$ 995		$ 247

[1] Total pre-tax restructuring charges for the quarter ended March 31, 2020, include cash charges of $3.1 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 March 31, 2019, include cash charges of $3.1 million and non-cash charges of (0.2) million. Cash charges consist of charges incurred during the quarter that will be settled in cash, either during the current period or future periods.

[3] For the quarter ended March 31, 2020, charges primarily related to certain wind-down costs, 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. For the quarter ended March 31, 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 the UK, exiting the cathodic protection operations in the Middle East and other cost savings initiatives.