Note 11 - Investments in Affiliates (Details Textual) $ in Thousands	9 Months Ended
	Sep. 30, 2020 USD ($)	Sep. 30, 2021 USD ($)	Dec. 31, 2020 USD ($)
Assets, Total	$ 2,488,273	$ 2,561,756	$ 2,379,996
Equity Method Investment, Other than Temporary Impairment	9,600
Foreign Affiliates [Member]
Number of Entities		13
Equity Method Investment, Other than Temporary Impairment	9,600
Foreign Affiliates [Member] | Minimum [Member]
Assets, Total		$ 100
Equity Method Investment, Ownership Percentage		25.00%
Foreign Affiliates [Member] | Maximum [Member]
Assets, Total		$ 84,400
Equity Method Investment, Ownership Percentage		50.00%
Real Estate Entities [Member]
Assets, Total	13,200	$ 75,500
Number of Entities		2
Real Estate Entities [Member] | Minimum [Member]
Equity Method Investment, Ownership Percentage		10.00%
Real Estate Entities [Member] | Maximum [Member]
Equity Method Investment, Ownership Percentage		25.00%
Asphalt Terminal Entity [Member]
Assets, Total		$ 33,400
Equity Method Investment, Nonconsolidated Investee or Group of Investees [Member]
Assets, Total	$ 282,004	$ 324,203	$ 298,502