Investments in Affiliates - Additional Information (Details) - Joint Venture Unconsolidated - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017	Mar. 31, 2017
Investments In And Advances To Affiliates [Line Items]
Total assets	$ 123,562	$ 160,359	$ 150,637
Texas [Member]
Investments In And Advances To Affiliates [Line Items]
Equity Method Investments	24,600	24,300	21,800
Other Affiliates [Member]
Investments In And Advances To Affiliates [Line Items]
Equity Method Investments	38,682	$ 38,469	$ 36,410
Total assets	123,600
Variable Interest Entity, Not Primary Beneficiary [Member]
Investments In And Advances To Affiliates [Line Items]
Total assets	21,500
Minimum [Member] | Variable Interest Entity, Not Primary Beneficiary [Member] | Real Estate Entities [Member]
Investments In And Advances To Affiliates [Line Items]
Total assets	1,700
Maximum [Member] | Variable Interest Entity, Not Primary Beneficiary [Member] | Real Estate Entities [Member]
Investments In And Advances To Affiliates [Line Items]
Total assets	$ 65,400