Note 12 - Investments in Affiliates (Details Textual) $ in Thousands	3 Months Ended
	Mar. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)	Mar. 31, 2019 USD ($)
Assets, Total	$ 2,384,375	$ 2,502,088	$ 2,358,603
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]
Equity Method Investment, Ownership Percentage	25.00%
Foreign Affiliates [Member] | Maximum [Member]
Equity Method Investment, Ownership Percentage	50.00%
Real Estate Entities [Member]
Number of Entities	3
Real Estate Entities [Member] | Minimum [Member]
Equity Method Investment, Ownership Percentage	18.00%
Real Estate Entities [Member] | Maximum [Member]
Equity Method Investment, Ownership Percentage	47.00%
Equity Method Investment, Nonconsolidated Investee or Group of Investees [Member]
Assets, Total	$ 275,878	287,679	316,418
Foreign Affiliates [Member] | Minimum [Member]
Assets, Total	200
Foreign Affiliates [Member] | Maximum [Member]
Assets, Total	62,500
Real Estate Entities [Member]
Assets, Total	13,300	$ 13,600	$ 13,100
Real Estate Entities [Member] | Minimum [Member]
Assets, Total	8,200
Real Estate Entities [Member] | Maximum [Member]
Assets, Total	33,600
Asphalt Terminal Entity [Member]
Assets, Total	$ 25,900