Note 4 - Restructuring (Details Textual) $ in Thousands	3 Months Ended	12 Months Ended
	Dec. 31, 2019 USD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)
Restructuring Charges, Non-Cash		$ 12,782	$ 13,814	$ 10,080
Restructuring 2017 [Member]
Restructuring Charges Pre Tax		171,900
Restructuring Charges, Net of Tax		155,700
Payments for Restructuring		45,300
Restructuring Reserve, Settled without Cash		$ 126,600
Restructuring and Related Cost, Expected Number of Additional Positions Eliminated		4
Restructuring Charges, Cash		$ 19,500	12,100	13,600
Restructuring Charges, Non-Cash		12,800	17,400	10,100
Restructuring 2017 [Member] | Minimum [Member]
Restructuring and Related Cost, Expected Cost, Total	$ 2,000	$ 2,000
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				40,200
Severance, Other Termination Benefit Costs and Contract Termination Costs [Member] | Restructuring 2017 [Member]
Restructuring and Related Costs, Incurred Cost, Total		$ 9,000	$ 6,900	$ 12,800