Note 12 - Segment Reporting (Details Textual) $ in Thousands	3 Months Ended
	Mar. 31, 2020 USD ($)		Mar. 31, 2019 USD ($)
Number of Reportable Segments	3
Restructuring 2017 [Member]
Restructuring Charges, Total	$ 3,623	[1]	$ 2,866	[2]
Restructuring 2017 [Member] | Corporate, Non-Segment [Member]
Restructuring Charges, Total	1,270		354
Restructuring 2017 [Member] | Operating Income (Loss) [Member] | Corporate, Non-Segment [Member]
Restructuring Charges, Total	700		400
Restructuring 2017 [Member] | Operating Income (Loss) [Member] | Divestiture of International Operations [Member] | Corporate, Non-Segment [Member]
Restructuring Charges, Total	700
Restructuring 2017 [Member] | Operating Income (Loss) [Member] | Infrastructure Solutions [Member]
Restructuring Charges, Total	500		2,100
Restructuring 2017 [Member] | Operating Income (Loss) [Member] | Infrastructure Solutions [Member] | Divestiture of International Operations [Member]
Restructuring Charges, Total	200		100
Restructuring 2017 [Member] | Operating Income (Loss) [Member] | Corrosion Protection [Member]
Restructuring Charges, Total	1,800		200
Restructuring 2017 [Member] | Other Expense [Member]
Restructuring Charges, Total	631	[1]	176	[2]
Restructuring 2017 [Member] | Other Expense [Member] | Corporate, Non-Segment [Member]
Restructuring Charges, Total	614		$ 0
Restructuring 2017 [Member] | Other Expense [Member] | Divestiture of International Operations [Member]
Restructuring Charges, Total	$ 400

[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.