Note 2 - Revenues (Details Textual) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Revenue from Contract with Customer, Including Assessed Tax	$ 54,614	$ 46,138	$ 158,174	$ 128,967
Gearing [Member]
Contract with Customer, Asset, after Allowance for Credit Loss, Total	1,475		$ 1,475
Transferred over Time [Member]
Revenue from Contract with Customer, Including Assessed Tax		$ 0		$ 0
Transferred over Time [Member] | Gearing [Member]
Revenue from Contract with Customer, Including Assessed Tax	$ 1,475