Notes and Other Receivables (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2018	Dec. 31, 2017
Accounts, Notes, Loans and Financing Receivable [Line Items]
Notes receivable	$ 68,386	$ 100,926
Secured Note Receivable, 10.00% Interest Rate, Due May 2021 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Notes receivable	$ 14,470	13,762
Stated interest rate	10.00%
Secured Note Receivable, 10.75% Interest Rate, Due September 2020 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Notes receivable	$ 30,926	29,318
Stated interest rate	10.75%
Secured Note Receivable, 9.5% Interest Rate, Due October 2019 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Notes receivable	$ 6,610	6,656
Stated interest rate	9.50%
Secured Note Receivable, 3.5% Interest Rate, Due December 16, 2017 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Notes receivable	$ 0	29,500
Stated interest rate	3.50%
Notes and Other Receivables from Affiliates [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Notes receivable	$ 4,234	5,061
Other Receivables [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Notes receivable	$ 12,146	$ 16,629