Note 12 - Investments in Affiliates - Equity Method Investments (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019	Jun. 30, 2019
Total investments in affiliates	$ 74,511	$ 84,176	$ 82,109
Foreign Affiliates [Member]
Total investments in affiliates	45,487	55,335	55,563
Real Estate Entities [Member]
Total investments in affiliates	16,578	17,229	17,781
Asphalt Terminal Entity [Member]
Total investments in affiliates	$ 12,446	$ 11,612	$ 8,765