Note 13 - Revenues (Details Textual) - USD ($) $ in Thousands	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018
Contract with Customer, Liability, Total	$ 3,652	$ 3,673	$ 3,949	$ 3,532	$ 3,715	$ 3,820