Note 2 - Accounting Policies (Details Textual) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020 USD ($) shares	Sep. 30, 2019 USD ($)	Sep. 30, 2020 USD ($) shares		Sep. 30, 2019 USD ($) shares	Dec. 31, 2019 USD ($)	Oct. 01, 2019
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Reclassification Adjustment from AOCI, Realized upon Sale or Liquidation, Net of Tax, Total			$ 1,500
Foreign Currency Transaction Gain (Loss), Realized			(420)		$ (370)
Goodwill, Impairment Loss	$ 39,430	$ 0	40,688	[1],[2]	$ 0
Goodwill, Ending Balance	$ 216,340		$ 216,340			$ 256,835
Energy Services [Member]
Reporting Unit, Percentage of Carrying Amount in Excess of Fair Value	31.30%		31.30%
Reporting Unit, Increase (Decrease) in Fair Value			$ (67,800)
Reporting Unit, Increase (Decrease) in Fair Value, Percentage			(44.00%)
Goodwill, Impairment Loss			$ 39,400
Goodwill, Ending Balance	$ 7,300		$ 7,300
Energy Services [Member] | Weighted Average Cost of Capital [Member]
Goodwill, Measurement Input	15.0		15.0				13.0
Energy Services [Member] | Measurement Input, Long-term Revenue Growth Rate [Member]
Goodwill, Measurement Input	3.2		3.2				3.4
Stock Options and Restricted and Deferred Stock Units [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount (in shares) | shares	501,802		484,712		497,192
Other Expense [Member]
Foreign Currency Transaction Gain (Loss), Realized	$ 700	$ 100	$ (400)		$ (400)

[1] During the second quarter of 2020, the Company recorded a $1.3 million goodwill impairment related to restructuring activities within Energy Services (see Note 4).

[2] During the third quarter of 2020, the Company recorded a $39.4 million goodwill impairment within Energy Services (see Note 2).