Note 4 - Restructuring - Recognized Cost Restructuring Activities (Details) - USD ($) $ in Thousands		3 Months Ended								12 Months Ended
		Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019		Dec. 31, 2018	Dec. 31, 2017
Restructuring charges		$ 14,300	$ 8,600	$ 6,500	$ 2,900	$ 13,900	$ 7,400	$ 2,900	$ 5,200
Restructuring reserve, settled without cash										$ 12,782		$ 13,814	$ 10,080
Restructuring 2016 [Member]
Restructuring reserve, balance					2,412				5,189	2,412		5,189
Restructuring charges										32,341	[1]	29,486	23,743
Restructuring reserve, foreign currency translation										(38)		(91)
Restructuring reserve, settled with cash	[2]									13,845		14,800	8,474
Restructuring reserve, settled without cash										12,782		17,372	10,080
Restructuring reserve, balance		8,088				2,412				8,088		2,412	5,189
Employee Severance [Member] | Restructuring 2016 [Member]
Restructuring reserve, balance					1,742				3,864	1,742		3,864
Restructuring charges										6,355		4,536	7,345
Restructuring reserve, foreign currency translation										(11)		(69)
Restructuring reserve, settled with cash	[2]									3,697		6,589	3,481
Restructuring reserve, settled without cash										0		0	0
Restructuring reserve, balance		4,389				1,742				4,389		1,742	3,864
Contract Termination [Member] | Restructuring 2016 [Member]
Restructuring reserve, balance					359				650	359		650
Restructuring charges										2,022		2,174	5,320
Restructuring reserve, foreign currency translation										(20)		(19)
Restructuring reserve, settled with cash	[2]									1,408		2,446	2,706
Restructuring reserve, settled without cash										0		0	1,964
Restructuring reserve, balance		953				359				953		359	650
Employee Relocation [Member] | Restructuring 2016 [Member]
Restructuring reserve, balance					0				0	0		0
Restructuring charges										653		184	147
Restructuring reserve, foreign currency translation										(3)		0
Restructuring reserve, settled with cash	[2]									283		184	147
Restructuring reserve, settled without cash										0		0	0
Restructuring reserve, balance		367				0				367		0	0
Other Restructuring [Member] | Restructuring 2016 [Member]
Restructuring reserve, balance					$ 311				$ 675	311		675
Restructuring charges										23,311		22,592	10,931	[3]
Restructuring reserve, foreign currency translation										(4)		(3)
Restructuring reserve, settled with cash	[2]									8,457		5,581	2,140
Restructuring reserve, settled without cash										12,782		17,372	8,116
Restructuring reserve, balance		$ 2,379				$ 311				$ 2,379		$ 311	$ 675

[1] 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.

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

[3] Includes charges primarily related to exiting non-pipe-related applications for the Tyfo system in North America and right-sizing the cathodic protection services operation in Canada, inclusive of wind-down costs, professional fees, patent write offs, fixed asset disposals and certain other restructuring and related charges.