Investments in Affiliates - Investments in Affiliates (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018	Mar. 31, 2018
Investments In And Advances To Affiliates [Line Items]
Investments in affiliates	$ 81,034	$ 84,354	$ 38,682
Joint Venture Unconsolidated [Member]
Investments In And Advances To Affiliates [Line Items]
Investments in affiliates	81,034	84,354	38,682
Joint Venture Unconsolidated [Member] | Foreign [Member]
Investments In And Advances To Affiliates [Line Items]
Investments in affiliates	56,082	55,715	0
Joint Venture Unconsolidated [Member] | Real Estate [Member]
Investments In And Advances To Affiliates [Line Items]
Investments in affiliates	16,433	19,676	29,829
Joint Venture Unconsolidated [Member] | Asphalt Terminal [Member]
Investments In And Advances To Affiliates [Line Items]
Investments in affiliates	$ 8,519	$ 8,963	$ 8,853