Investments in Affiliates - Additional Information (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017	Jun. 30, 2017
Asphalt Terminal Entity [Member] | Limited Liability Company [Member] | Nevada [Member]
Investments In And Advances To Affiliates [Line Items]
Equity interest acquired	50.00%
Joint Venture Unconsolidated [Member]
Investments In And Advances To Affiliates [Line Items]
Total assets	$ 310,337	$ 160,359	$ 156,969
Joint Venture Unconsolidated [Member] | Texas [Member]
Investments In And Advances To Affiliates [Line Items]
Equity Method Investments	24,000	24,300	22,200
Other Affiliates [Member] | Joint Venture Unconsolidated [Member]
Investments In And Advances To Affiliates [Line Items]
Equity Method Investments	99,495	$ 38,469	$ 37,170
Total assets	310,300
Variable Interest Entity, Not Primary Beneficiary [Member] | Joint Venture Unconsolidated [Member]
Investments In And Advances To Affiliates [Line Items]
Total assets	$ 20,400
Minimum [Member] | Foreign Affiliates [Member] | Joint Venture Unconsolidated [Member] | Equity Method Investment Directly Owned [Member]
Investments In And Advances To Affiliates [Line Items]
Ownership percentage	25.00%
Minimum [Member] | Variable Interest Entity, Not Primary Beneficiary [Member] | Real Estate Entities [Member] | Joint Venture Unconsolidated [Member]
Investments In And Advances To Affiliates [Line Items]
Total assets	$ 300
Minimum [Member] | Variable Interest Entity, Not Primary Beneficiary [Member] | Foreign Affiliates [Member] | Joint Venture Unconsolidated [Member]
Investments In And Advances To Affiliates [Line Items]
Total assets	$ 100
Maximum [Member] | Foreign Affiliates [Member] | Joint Venture Unconsolidated [Member] | Equity Method Investment Indirectly Owned [Member]
Investments In And Advances To Affiliates [Line Items]
Ownership percentage	50.00%
Maximum [Member] | Variable Interest Entity, Not Primary Beneficiary [Member] | Real Estate Entities [Member] | Joint Venture Unconsolidated [Member]
Investments In And Advances To Affiliates [Line Items]
Total assets	$ 68,200
Maximum [Member] | Variable Interest Entity, Not Primary Beneficiary [Member] | Foreign Affiliates [Member] | Joint Venture Unconsolidated [Member]
Investments In And Advances To Affiliates [Line Items]
Total assets	$ 64,600