Note 4 - Restructuring - Pre Tax Restructuring Cost (Details) - USD ($) $ in Thousands	3 Months Ended				9 Months Ended
	Sep. 30, 2019		Sep. 30, 2018		Sep. 30, 2019		Sep. 30, 2018
Restructuring charges	$ 1,400		$ 1,200		$ 5,500		$ 4,500
Restructuring 2017 [Member]
Restructuring charges	8,607	[1]	7,423	[2]	17,989	[3]	15,580	[4]
Restructuring 2017 [Member] | Cost of Revenues [Member]
Restructuring charges	(33)	[1]	705	[2]	437	[3]	705	[4]
Restructuring 2017 [Member] | Operating Expense [Member]
Restructuring charges	1,860	[1]	3,018	[2]	5,595	[3]	7,846	[4]
Restructuring 2017 [Member] | Goodwill Impairment [Member]
Restructuring charges	0		1,389		0		1,389
Restructuring 2017 [Member] | Definite-lived Intangible Asset Impairment [Member]
Restructuring charges	0		870		0		870
Restructuring 2017 [Member] | Restructuring and Related Charges [Member]
Restructuring charges	1,435	[1]	1,219	[2]	5,495	[3]	4,548	[4]
Restructuring 2017 [Member] | Other Expense [Member]
Restructuring charges	5,345	[1]	222	[2]	6,462	[3]	222	[4]
Restructuring 2017 [Member] | Employee Severance [Member]
Restructuring charges	1,147		949		3,774		3,217
Restructuring 2017 [Member] | Contract Termination [Member]
Restructuring charges	209		215		1,447		1,202
Restructuring 2017 [Member] | Employee Relocation [Member]
Restructuring charges	79		55		274		129
Restructuring 2017 [Member] | Other Restructuring [Member]
Restructuring charges	7,172	[5]	6,204	[5]	12,494	[6]	11,032	[6]
Restructuring 2017 [Member] | Operating Segments [Member] | Infrastructure Solutions [Member]
Restructuring charges	5,904		6,136		10,561		11,882
Restructuring 2017 [Member] | Operating Segments [Member] | Infrastructure Solutions [Member] | Cost of Revenues [Member]
Restructuring charges	(30)		138		(122)		138
Restructuring 2017 [Member] | Operating Segments [Member] | Infrastructure Solutions [Member] | Operating Expense [Member]
Restructuring charges	748		2,333		3,070		5,387
Restructuring 2017 [Member] | Operating Segments [Member] | Infrastructure Solutions [Member] | Goodwill Impairment [Member]
Restructuring charges	0		1,389		0		1,389
Restructuring 2017 [Member] | Operating Segments [Member] | Infrastructure Solutions [Member] | Definite-lived Intangible Asset Impairment [Member]
Restructuring charges	0		870		0		870
Restructuring 2017 [Member] | Operating Segments [Member] | Infrastructure Solutions [Member] | Restructuring and Related Charges [Member]
Restructuring charges	490		1,184		1,707		3,876
Restructuring 2017 [Member] | Operating Segments [Member] | Infrastructure Solutions [Member] | Other Expense [Member]
Restructuring charges	4,696		222		5,906		222
Restructuring 2017 [Member] | Operating Segments [Member] | Infrastructure Solutions [Member] | Employee Severance [Member]
Restructuring charges	210		914		1,043		2,695
Restructuring 2017 [Member] | Operating Segments [Member] | Infrastructure Solutions [Member] | Contract Termination [Member]
Restructuring charges	201		215		534		1,052
Restructuring 2017 [Member] | Operating Segments [Member] | Infrastructure Solutions [Member] | Employee Relocation [Member]
Restructuring charges	79		55		130		129
Restructuring 2017 [Member] | Operating Segments [Member] | Infrastructure Solutions [Member] | Other Restructuring [Member]
Restructuring charges	5,414	[5]	4,952	[5]	8,854	[6]	8,006	[6]
Restructuring 2017 [Member] | Operating Segments [Member] | Corrosion Protection [Member]
Restructuring charges	918		1,023		4,343		2,823
Restructuring 2017 [Member] | Operating Segments [Member] | Corrosion Protection [Member] | Cost of Revenues [Member]
Restructuring charges	(3)		567		559		567
Restructuring 2017 [Member] | Operating Segments [Member] | Corrosion Protection [Member] | Operating Expense [Member]
Restructuring charges	315		421		583		1,904
Restructuring 2017 [Member] | Operating Segments [Member] | Corrosion Protection [Member] | Goodwill Impairment [Member]
Restructuring charges	0		0		0		0
Restructuring 2017 [Member] | Operating Segments [Member] | Corrosion Protection [Member] | Definite-lived Intangible Asset Impairment [Member]
Restructuring charges	0		0		0		0
Restructuring 2017 [Member] | Operating Segments [Member] | Corrosion Protection [Member] | Restructuring and Related Charges [Member]
Restructuring charges	455		35		3,151		352
Restructuring 2017 [Member] | Operating Segments [Member] | Corrosion Protection [Member] | Other Expense [Member]
Restructuring charges	151		0		50		0
Restructuring 2017 [Member] | Operating Segments [Member] | Corrosion Protection [Member] | Employee Severance [Member]
Restructuring charges	447		35		2,192		352
Restructuring 2017 [Member] | Operating Segments [Member] | Corrosion Protection [Member] | Contract Termination [Member]
Restructuring charges	8		0		815		0
Restructuring 2017 [Member] | Operating Segments [Member] | Corrosion Protection [Member] | Employee Relocation [Member]
Restructuring charges	0		0		144		0
Restructuring 2017 [Member] | Operating Segments [Member] | Corrosion Protection [Member] | Other Restructuring [Member]
Restructuring charges	463	[5]	988	[5]	1,192	[6]	2,471	[6]
Restructuring 2017 [Member] | Operating Segments [Member] | Energy Services [Member]
Restructuring charges	139				179
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	65				65
Restructuring 2017 [Member] | Operating Segments [Member] | Energy Services [Member] | Goodwill Impairment [Member]
Restructuring charges	0				0
Restructuring 2017 [Member] | Operating Segments [Member] | Energy Services [Member] | Definite-lived Intangible Asset Impairment [Member]
Restructuring charges	0				0
Restructuring 2017 [Member] | Operating Segments [Member] | Energy Services [Member] | Restructuring and Related Charges [Member]
Restructuring charges	74				114
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	74				114
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	65	[5]			65	[6]
Restructuring 2017 [Member] | Corporate, Non-Segment [Member]
Restructuring charges	1,646		264		2,906		875
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	732		264		1,877		555
Restructuring 2017 [Member] | Corporate, Non-Segment [Member] | Goodwill Impairment [Member]
Restructuring charges	0		0		0		0
Restructuring 2017 [Member] | Corporate, Non-Segment [Member] | Definite-lived Intangible Asset Impairment [Member]
Restructuring charges	0		0		0		0
Restructuring 2017 [Member] | Corporate, Non-Segment [Member] | Restructuring and Related Charges [Member]
Restructuring charges	416		0		523		320
Restructuring 2017 [Member] | Corporate, Non-Segment [Member] | Other Expense [Member]
Restructuring charges	498		0		506		0
Restructuring 2017 [Member] | Corporate, Non-Segment [Member] | Employee Severance [Member]
Restructuring charges	416		0		425		170
Restructuring 2017 [Member] | Corporate, Non-Segment [Member] | Contract Termination [Member]
Restructuring charges	0		0		98		150
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	$ 1,230	[5]	$ 264	[5]	$ 2,383	[6]	$ 555	[6]

[1] Total pre-tax restructuring charges for the quarter ended September 30, 2019, include cash charges of $3.1 million and non-cash charges of $5.5 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 September 30, 2018, include cash charges of $2.3 million and non-cash charges of $5.1 million. Cash charges consist of charges incurred during the quarter that will be settled in cash, either during the current period or future periods.

[3] Total pre-tax restructuring charges include cash charges of $11.6 million and non-cash charges of $6.4 million. Cash charges consist of charges incurred during the period that will be settled in cash, either during the current period or future periods.

[4] Total pre-tax restructuring charges include cash charges of $7.4 million and non-cash charges of $8.2 million. Cash charges consist of charges incurred during the period that will be settled in cash, either during the current period or future periods.

[5] For the quarter ended September 30, 2019, 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 exiting the CIPP operations in Europe, exiting the cathodic protection operations in the Middle East, disposing of certain international businesses and other cost savings initiatives. For the quarter ended September 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 nine months ended September 30, 2019, 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 exiting the CIPP operations in Europe, exiting the cathodic protection operations in the Middle East, disposing of certain international businesses and other cost savings initiatives. For the nine months ended September 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.