Note 10 - Investments in Affiliates (Details Textual) $ in Thousands	12 Months Ended
Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)
Assets, Total	$ 2,379,996	$ 2,502,088
Equity Method Investment, Nonconsolidated Investee or Group of Investees [Member]
Assets, Total	$ 298,502	287,679
Asphalt Terminal Entity [Member]
Equity Method Investment, Ownership Percentage	50.00%
Assets, Total	$ 32,900
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%
Assets, Total	$ 100
Foreign Affiliates [Member] \| Maximum [Member]
Equity Method Investment, Ownership Percentage	50.00%
Assets, Total	$ 72,400
Real Estate Entities [Member]
Assets, Total		$ 13,600
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%
Real Estate Entities One [Member]
Assets, Total	$ 24,500
Real Estate Entities Two [Member]
Assets, Total	$ 42,900

Sum of the carrying amounts as of the balance sheet date of all assets that are recognized. Assets are probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

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