Note 4 - Restructuring - Recognized Cost Restructuring Activities (Details) - USD ($)	3 Months Ended				6 Months Ended				23 Months Ended
	Jun. 30, 2019		Jun. 30, 2018		Jun. 30, 2019		Jun. 30, 2018		Jun. 30, 2019
Restructuring charges	$ 3,000,000.0		$ 1,500,000		$ 4,100,000		$ 3,300,000
Non-cash restructuring charges					1,409,000		2,980,000
Restructuring 2017 [Member]
Restructing reserve, balance					2,412,000		5,189,000
Restructuring charges	6,516,000	[1]	2,913,000	[2]	9,382,000	[3]	8,157,000	[4]
Restructing reserve, foreign currency translation					(27,000)		(18,000)
Restructing reserve, settled with cash					5,942,000	[5]	6,481,000	[6]	$ 34,300,000
Restructing reserve, settled without cash					1,409,000
Restructing reserve, balance	4,416,000		3,867,000		4,416,000		3,867,000		4,416,000
Non-cash restructuring charges	1,100,000		600,000		900,000		2,980,000
Employee Severance [Member] | Restructuring 2017 [Member]
Restructing reserve, balance					1,742,000		3,864,000
Restructuring charges	2,132,000		1,197,000		2,627,000		2,268,000
Restructing reserve, foreign currency translation					(10,000)		(9,000)
Restructing reserve, settled with cash					1,860,000	[5]	2,993,000	[6]
Restructing reserve, settled without cash					0
Restructing reserve, balance	2,499,000		3,130,000		2,499,000		3,130,000		2,499,000
Non-cash restructuring charges							0
Contract Termination [Member] | Restructuring 2017 [Member]
Restructing reserve, balance					359,000		650,000
Restructuring charges	698,000		309,000		1,238,000		987,000
Restructing reserve, foreign currency translation					(13,000)		(9,000)
Restructing reserve, settled with cash					606,000	[5]	1,041,000	[6]
Restructing reserve, settled without cash					0
Restructing reserve, balance	978		587,000		978		587,000		978
Non-cash restructuring charges							0
Employee Relocation [Member] | Restructuring 2017 [Member]
Restructing reserve, balance					0		0
Restructuring charges	144,000		34,000		195,000		74,000
Restructing reserve, foreign currency translation					(1,000)		0
Restructing reserve, settled with cash					26,000	[5]	74,000	[6]
Restructing reserve, settled without cash					0
Restructing reserve, balance	168,000		0		168,000		0		168,000
Non-cash restructuring charges							0
Other Restructuring [Member] | Restructuring 2017 [Member]
Restructing reserve, balance					311,000		675,000
Restructuring charges	3,542,000	[7]	1,373,000	[7]	5,322,000	[8]	4,828,000	[8]
Restructing reserve, foreign currency translation					(3,000)		0
Restructing reserve, settled with cash					3,450,000	[5]	2,373,000	[6]
Restructing reserve, settled without cash					1,409,000
Restructing reserve, balance	$ 771,000		$ 150,000		$ 771,000		150,000		$ 771,000
Non-cash restructuring charges							$ 2,980,000

[1] Total pre-tax restructuring charges for the quarter ended June 30, 2019, include cash charges of $5.4 million and non-cash charges of $1.1 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 June 30, 2018, include cash charges of $2.3 million and non-cash charges of $0.6 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] Total pre-tax restructuring charges include cash charges of $8.5 million and non-cash charges of $0.9 million. Cash charges consist of charges incurred during the quarter that will be settled in cash, either during the current period or future periods.

[4] Total pre-tax restructuring charges include cash charges of $5.2 million and non-cash charges of $3.0 million. Cash charges consist of charges incurred during the quarter that will be settled in cash, either during the current period or future periods.

[5] Refers to cash utilized to settle charges during the first six months of 2019.

[6] Refers to cash utilized to settle charges during the first six months of 2018.

[7] For the quarter ended June 30, 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 Europe, exiting the cathodic protection operations in the Middle East and other cost savings initiatives. For the quarter ended June 30, 2018, 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 applications for the Tyfo systems in North America and right-sizing the CIPP operations in Australia and Denmark.

[8] For the six months ended June 30, 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 Europe, exiting the cathodic protection operations in the Middle East and other cost savings initiatives. For the six months ended June 30, 2018, 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 applications for the Tyfo systems in North America and right-sizing the CIPP operations in Australia and Denmark.