Note 4 - Restructuring (Details Textual) $ in Thousands	3 Months Ended	12 Months Ended							41 Months Ended
	Dec. 31, 2019	Dec. 31, 2020 USD ($)		Dec. 31, 2019 USD ($)		Dec. 31, 2018 USD ($)		Dec. 31, 2017 USD ($)	Dec. 31, 2020 USD ($)	Dec. 31, 2020 USD ($)
Expected Restructuring Cash Charges Related to COVID-19		$ 2,000							$ 2,000	$ 2,000
Restructuring Charges, Non-Cash		1,202		$ 12,717		$ 13,814
Restructuring 2017 [Member]
Restructuring Charges Pre Tax										188,700
Restructuring Charges, Net of Tax										171,600
Payments for Restructuring		16,016	[1]	13,845	[1]	14,800	[1]			57,300
Restructuring Reserve, Settled without Cash		4,801	[2]	$ 12,782	[2]	17,372	[2]			$ 131,400
Restructuring and Related Cost, Number of Positions Eliminated									830
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		45,000
Severance, Other Termination Benefit Costs and Contract Termination Costs [Member] | Restructuring 2017 [Member]
Restructuring and Related Costs, Incurred Cost, Total		4,200		$ 8,200		6,700
Restructuring 2017 [Member]
Restructuring Charges, Cash		12,000		19,500		12,100
Restructuring Charges, Non-Cash		4,700		12,800		17,400
Restructuring Cost Related to Discontinued Operations [Member]
Restructuring Reserve, Settled without Cash		$ 3,600		$ 100		$ 0

[1] Refers to cash utilized to settle charges during the year.

[2] Includes non-cash charges from discontinued operations of $3.6 million, $0.1 million and zero in 2020, 2019 and 2018, respectively.