Note 4 - Restructuring - Recognized Cost Restructuring Activities (Details) - Restructuring 2017 [Member] - USD ($) $ in Thousands		12 Months Ended						41 Months Ended
		Dec. 31, 2020		Dec. 31, 2019		Dec. 31, 2018		Dec. 31, 2020
Restructuring reserve, balance		$ 8,088		$ 2,412		$ 5,189
Restructuring charges		16,737	[1]	32,341	[2]	29,486	[3]
Restructuring reserve, foreign currency translation		(1)		(38)		(91)
Restructuring reserve, settled with cash		16,016	[4]	13,845	[4]	14,800	[4]	$ 57,300
Restructuring reserve, settled without cash		4,801	[5]	12,782	[5]	17,372	[5]	131,400
Restructuring reserve, balance		4,007		8,088		2,412		4,007
Employee Severance [Member]
Restructuring reserve, balance		4,389		1,742		3,864
Restructuring charges		4,597		6,355		4,536
Restructuring reserve, foreign currency translation		(30)		(11)		(69)
Restructuring reserve, settled with cash	[4]	7,179		3,697		6,589
Restructuring reserve, settled without cash	[5]	0		0		0
Restructuring reserve, balance		1,777		4,389		1,742		1,777
Contract Termination [Member]
Restructuring reserve, balance		953		359		650
Restructuring charges		99		2,022		2,174
Restructuring reserve, foreign currency translation		(7)		(20)		(19)
Restructuring reserve, settled with cash	[4]	1,020		1,408		2,446
Restructuring reserve, settled without cash	[5]	0		0		0
Restructuring reserve, balance		25		953		359		25
Employee Relocation [Member]
Restructuring reserve, balance		367		0		0
Restructuring charges		270		653		184
Restructuring reserve, foreign currency translation		1		(3)		0
Restructuring reserve, settled with cash	[4]	515		283		184
Restructuring reserve, settled without cash	[5]	0		0		0
Restructuring reserve, balance		123		367		0		123
Other Restructuring [Member]
Restructuring reserve, balance		2,379		311		675
Restructuring charges		11,771	[6]	23,311	[7]	22,592	[8]
Restructuring reserve, foreign currency translation		35		(4)		(3)
Restructuring reserve, settled with cash	[4]	7,302		8,457		5,581
Restructuring reserve, settled without cash	[5]	4,801		12,782		17,372
Restructuring reserve, balance		$ 2,082		$ 2,379		$ 311		$ 2,082

[1] Total pre-tax restructuring charges include cash charges of $12.0 million and non-cash charges of $4.7 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 $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.

[3] 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.

[4] Refers to cash utilized to settle charges during the year.

[5] Includes non-cash charges from discontinued operations of $3.6 million, $0.1 million and zero in 2020, 2019 and 2018, respectively.

[6] Includes 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 exiting a small business in discontinued operations.

[7] 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.

[8] 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.