Note 4 - Restructuring (Details Textual) $ in Thousands	3 Months Ended			9 Months Ended				12 Months Ended		38 Months Ended
	Sep. 30, 2020 USD ($)	Dec. 31, 2019	Sep. 30, 2019 USD ($)	Sep. 30, 2020 USD ($)		Sep. 30, 2019 USD ($)		Dec. 31, 2019	Dec. 31, 2017 USD ($)	Sep. 30, 2020 USD ($)
Expected Restructuring Cash Charges Related to COVID-19	$ 2,000			$ 2,000						$ 2,000
Restructuring Charges, Non-Cash				1,067		$ 6,419
Restructuring 2017 [Member]
Restructuring Charges Pre Tax										184,700
Restructuring Charges, Net of Tax										166,000
Payments for Restructuring				13,955	[1]	9,739	[2]			54,800
Restructuring Reserve, Settled without Cash										$ 129,900
Restructuring and Related Cost, Number of Positions Eliminated										804
Restructuring Charges, Cash	3,700		$ 3,100	9,500		11,600
Restructuring Charges, Non-Cash	500		5,500	3,200		6,400
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									$ 43,500
Severance, Other Termination Benefit Costs and Contract Termination Costs [Member] | Restructuring 2017 [Member]
Restructuring and Related Costs, Incurred Cost, Total	$ 2,300		$ 1,400	$ 4,300		$ 5,500

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

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