Note 14 - Segment and Geographic Information (Details Textual) $ in Thousands		3 Months Ended								12 Months Ended
		Dec. 31, 2019 USD ($)	Sep. 30, 2019 USD ($)	Jun. 30, 2019 USD ($)	Mar. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Sep. 30, 2018 USD ($)	Jun. 30, 2018 USD ($)	Mar. 31, 2018 USD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)		Dec. 31, 2017 USD ($)
Number of Reportable Segments										3
Restructuring Charges, Total		$ 14,300	$ 8,600	$ 6,500	$ 2,900	$ 13,900	$ 7,400	$ 2,900	$ 5,200
Impairment of Long-Lived Assets to be Disposed of										$ 23,427	$ 0		$ 0
Goodwill, Impairment Loss										0	1,389	[1]	45,390
Corporate, Non-Segment [Member]
Impairment of Long-Lived Assets to be Disposed of		$ 2,900								2,900
Infrastructure Solutions [Member]
Impairment of Long-Lived Assets to be Disposed of										17,600
Goodwill, Impairment Loss											1,389	[1]	45,400
Impairment of Intangible Assets (Excluding Goodwill), Total													41,000
Infrastructure Solutions [Member] | Environmental Techniques [Member]
Business Combination, Acquisition Related Costs													100
Corrosion Protection [Member]
Impairment of Long-Lived Assets to be Disposed of										2,900
Goodwill, Impairment Loss	[1]										(0)
Energy Services [Member]
Goodwill, Impairment Loss	[1]										(0)
Restructuring 2017 [Member]
Restructuring Charges, Total										32,341	29,486	[2]	23,743	[3]
Restructuring 2017 [Member] | Corporate, Non-Segment [Member]
Restructuring Charges, Total										6,041	1,637		1,604
Restructuring 2017 [Member] | Operating Income (Loss) [Member] | Corporate, Non-Segment [Member]
Restructuring Charges, Total										5,200	1,600		1,600
Restructuring 2017 [Member] | Operating Income (Loss) [Member] | Divestiture of International Operations [Member] | Corporate, Non-Segment [Member]
Restructuring Charges, Total										2,200	4,100		1,200
Restructuring 2017 [Member] | Operating Income (Loss) [Member] | Infrastructure Solutions [Member]
Restructuring Charges, Total										7,500	16,100		17,500
Restructuring 2017 [Member] | Operating Income (Loss) [Member] | Infrastructure Solutions [Member] | Divestiture of International Operations [Member]
Restructuring Charges, Total										1,000	400
Restructuring 2017 [Member] | Operating Income (Loss) [Member] | Corrosion Protection [Member]
Restructuring Charges, Total										7,700	7,600		4,900
Restructuring 2017 [Member] | Operating Income (Loss) [Member] | Corrosion Protection [Member] | Divestiture of International Operations [Member]
Restructuring Charges, Total										100	2,500		1,600
Restructuring 2017 [Member] | Operating Income (Loss) [Member] | Energy Services [Member]
Restructuring Charges, Total										1,700	300
Restructuring 2017 [Member] | Other Nonoperating Income (Expense) [Member]
Restructuring Charges, Total										$ 10,200			$ 4,000
Restructuring 2017 [Member] | Other Nonoperating Income (Expense) [Member] | Bayou [Member]
Restructuring Charges, Total											$ 7,000

[1] During 2018, the Company recorded goodwill of $2.7 million and $1.3 million related to the acquisitions of Hebna and P2S, respectively (see Note 1).

[2] 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.

[3] 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.