Note 4 - Restructuring - Pre Tax Restructuring Cost (Details) - USD ($)	3 Months Ended				6 Months Ended
	Jun. 30, 2019		Jun. 30, 2018		Jun. 30, 2019		Jun. 30, 2018
Restructuring charges	$ 3,000,000.0		$ 1,500,000		$ 4,100,000		$ 3,300,000
Restructuring 2017 [Member]
Restructuring charges	6,516,000	[1]	2,913,000	[2]	9,382,000	[3]	8,157,000	[4]
Restructuring 2017 [Member] | Cost of Revenues [Member]
Restructuring charges	396,000	[1]	0	[2]	470,000	[3]	0	[4]
Restructuring 2017 [Member] | Operating Expense [Member]
Restructuring charges	2,205,000	[1]	1,373,000	[2]	3,735,000	[3]	4,828,000	[4]
Restructuring 2017 [Member] | Restructuring and Related Charges [Member]
Restructuring charges	2,974,000	[1]	1,540,000	[2]	4,060,000	[3]	3,329,000	[4]
Restructuring 2017 [Member] | Other Expense [Member]
Restructuring charges	941,000	[1]	0	[2]	1,117,000	[3]	0	[4]
Restructuring 2017 [Member] | Employee Severance [Member]
Restructuring charges	2,132,000		1,197,000		2,627,000		2,268,000
Restructuring 2017 [Member] | Contract Termination [Member]
Restructuring charges	698,000		309,000		1,238,000		987,000
Restructuring 2017 [Member] | Employee Relocation [Member]
Restructuring charges	144,000		34,000		195,000		74,000
Restructuring 2017 [Member] | Other Restructuring [Member]
Restructuring charges	3,542,000	[5]	1,373,000	[5]	5,322,000	[6]	4,828,000	[6]
Restructuring 2017 [Member] | Operating Segments [Member] | Infrastructure Solutions [Member]
Restructuring charges	2,155,000		2,530,000		4,657,000		5,746,000
Restructuring 2017 [Member] | Operating Segments [Member] | Infrastructure Solutions [Member] | Cost of Revenues [Member]
Restructuring charges	(67,000)		0		(92,000)		0
Restructuring 2017 [Member] | Operating Segments [Member] | Infrastructure Solutions [Member] | Operating Expense [Member]
Restructuring charges	976,000		1,186,000		2,322,000		3,054,000
Restructuring 2017 [Member] | Operating Segments [Member] | Infrastructure Solutions [Member] | Restructuring and Related Charges [Member]
Restructuring charges	459,000		1,344,000		1,217,000		2,692,000
Restructuring 2017 [Member] | Operating Segments [Member] | Infrastructure Solutions [Member] | Other Expense [Member]
Restructuring charges	787,000		0		1,210,000		0
Restructuring 2017 [Member] | Operating Segments [Member] | Infrastructure Solutions [Member] | Employee Severance [Member]
Restructuring charges	551,000		1,001,000		833,000		1,781,000
Restructuring 2017 [Member] | Operating Segments [Member] | Infrastructure Solutions [Member] | Contract Termination [Member]
Restructuring charges	(92,000)		309,000		333,000		837,000
Restructuring 2017 [Member] | Operating Segments [Member] | Infrastructure Solutions [Member] | Employee Relocation [Member]
Restructuring charges	0		34,000		51,000		74,000
Restructuring 2017 [Member] | Operating Segments [Member] | Infrastructure Solutions [Member] | Other Restructuring [Member]
Restructuring charges	1,696,000	[6]	1,186,000	[5]	3,440,000	[6]	3,054,000	[6]
Restructuring 2017 [Member] | Operating Segments [Member] | Corrosion Protection [Member]
Restructuring charges	3,449,000		335,000		3,425,000		1,800,000
Restructuring 2017 [Member] | Operating Segments [Member] | Corrosion Protection [Member] | Cost of Revenues [Member]
Restructuring charges	463,000		0		562,000		0
Restructuring 2017 [Member] | Operating Segments [Member] | Corrosion Protection [Member] | Operating Expense [Member]
Restructuring charges	331,000		139,000		268,000		1,483,000
Restructuring 2017 [Member] | Operating Segments [Member] | Corrosion Protection [Member] | Restructuring and Related Charges [Member]
Restructuring charges	2,509,000		196,000		2,696,000		317,000
Restructuring 2017 [Member] | Operating Segments [Member] | Corrosion Protection [Member] | Other Expense [Member]
Restructuring charges	146,000		0		(101,000)		0
Restructuring 2017 [Member] | Operating Segments [Member] | Corrosion Protection [Member] | Employee Severance [Member]
Restructuring charges	1,575,000		196,000		1,745,000		317,000
Restructuring 2017 [Member] | Operating Segments [Member] | Corrosion Protection [Member] | Contract Termination [Member]
Restructuring charges	790,000		0		807,000		0
Restructuring 2017 [Member] | Operating Segments [Member] | Corrosion Protection [Member] | Employee Relocation [Member]
Restructuring charges	144,000		0		144,000		0
Restructuring 2017 [Member] | Operating Segments [Member] | Corrosion Protection [Member] | Other Restructuring [Member]
Restructuring charges	940,000	[5]	139,000	[5]	729,000	[6]	1,483,000	[6]
Restructuring 2017 [Member] | Operating Segments [Member] | Energy Services [Member]
Restructuring charges	6,000				40,000
Restructuring 2017 [Member] | Operating Segments [Member] | Energy Services [Member] | Cost of Revenues [Member]
Restructuring charges	0				0
Restructuring 2017 [Member] | Operating Segments [Member] | Energy Services [Member] | Operating Expense [Member]
Restructuring charges	0				0
Restructuring 2017 [Member] | Operating Segments [Member] | Energy Services [Member] | Restructuring and Related Charges [Member]
Restructuring charges	6,000				40,000
Restructuring 2017 [Member] | Operating Segments [Member] | Energy Services [Member] | Other Expense [Member]
Restructuring charges	0				0
Restructuring 2017 [Member] | Operating Segments [Member] | Energy Services [Member] | Employee Severance [Member]
Restructuring charges	6,000				40,000
Restructuring 2017 [Member] | Operating Segments [Member] | Energy Services [Member] | Contract Termination [Member]
Restructuring charges	0				0
Restructuring 2017 [Member] | Operating Segments [Member] | Energy Services [Member] | Employee Relocation [Member]
Restructuring charges	0				0
Restructuring 2017 [Member] | Operating Segments [Member] | Energy Services [Member] | Other Restructuring [Member]
Restructuring charges	0	[5]			0	[6]
Restructuring 2017 [Member] | Corporate, Non-Segment [Member]
Restructuring charges	906,000		48,000		1,260,000		611,000
Restructuring 2017 [Member] | Corporate, Non-Segment [Member] | Cost of Revenues [Member]
Restructuring charges	0		0		0		0
Restructuring 2017 [Member] | Corporate, Non-Segment [Member] | Operating Expense [Member]
Restructuring charges	898,000		48,000		1,145,000		291,000
Restructuring 2017 [Member] | Corporate, Non-Segment [Member] | Restructuring and Related Charges [Member]
Restructuring charges	0		0		107,000		320,000
Restructuring 2017 [Member] | Corporate, Non-Segment [Member] | Other Expense [Member]
Restructuring charges	8,000		0		8,000		0
Restructuring 2017 [Member] | Corporate, Non-Segment [Member] | Employee Severance [Member]
Restructuring charges	0		0		9,000		170,000
Restructuring 2017 [Member] | Corporate, Non-Segment [Member] | Contract Termination [Member]
Restructuring charges	0		0		98,000		150,000
Restructuring 2017 [Member] | Corporate, Non-Segment [Member] | Employee Relocation [Member]
Restructuring charges	0		0		0		0
Restructuring 2017 [Member] | Corporate, Non-Segment [Member] | Other Restructuring [Member]
Restructuring charges	$ 906,000	[5]	$ 48,000	[5]	$ 1,153,000	[6]	$ 291,000	[6]

[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] 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.

[6] 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.