Note 4 - Restructuring (Details Textual) $ in Thousands	3 Months Ended			6 Months Ended				12 Months Ended		35 Months Ended
	Jun. 30, 2020 USD ($)	Dec. 31, 2019	Jun. 30, 2019 USD ($)	Jun. 30, 2020 USD ($)		Jun. 30, 2019 USD ($)		Dec. 31, 2019	Dec. 31, 2017 USD ($)	Jun. 30, 2020 USD ($)
Restructuring Charges, Non-Cash				$ 503		$ 1,409
Minimum [Member]
Expected Restructuring Cash Charges Related to COVID-19	$ 3,000			3,000						$ 3,000
Maximum [Member]
Expected Restructuring Cash Charges Related to COVID-19	5,000			5,000						5,000
Restructuring 2017 [Member]
Restructuring Charges Pre Tax										180,400
Restructuring Charges, Net of Tax										162,600
Payments for Restructuring				9,681	[1]	5,942	[2]			51,100
Restructuring Reserve, Settled without Cash										$ 129,300
Restructuring and Related Cost, Number of Positions Eliminated										745
Restructuring Charges, Cash	2,600		$ 5,400	5,800		8,500
Restructuring Charges, Non-Cash	2,200		1,100	2,700		900
Downsize Operation in US [Member]
Restructuring and Related Cost, Number of Office Closed		3
Restructuring and Related Cost, Number of Offices Exiting Capital Intensive Drilling Activities		4
Restructuring and Related Cost, Number of Positions Eliminated, Period Percent								20.00%
Restructuring and Related Cost, Contributed To Cathodic Protection Domestic Revenue, Percentage								20.00%
Restructuring Charges Related to Goodwill and Long-lived Asset Impairment Charges [Member] | Restructuring 2017 [Member]
Restructuring Reserve, Settled without Cash									$ 86,400
Allowance, Write-offs and Long-lived Assets, Impairment of Intangible Assets and Net Losses On Disposal of Entities [Member] | Restructuring 2017 [Member]
Restructuring Reserve, Settled without Cash									$ 42,900
Severance, Other Termination Benefit Costs and Contract Termination Costs [Member] | Restructuring 2017 [Member]
Restructuring and Related Costs, Incurred Cost, Total	$ 700		$ 3,000	$ 2,000		$ 4,100

[1] Refers to cash utilized to settle charges during the first six months of 2020.

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