Notes and Other Receivables (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2018	Dec. 31, 2017
Accounts, Notes, Loans and Financing Receivable [Line Items]
Notes receivable	$ 69,166	$ 100,926
Secured Note Receivable, 10.00% Interest Rate, Due May 2021 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Notes receivable	$ 14,843	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	$ 31,776	29,318
Stated interest rate	10.75%
Secured Note Receivable, 9.50% Interest Rate, Due October 2019 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Notes receivable	$ 6,613	6,656
Stated interest rate	9.50%
Secured Note Receivable, 3.50% Interest Rate, Due March 2018 [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	$ 3,641	5,061
Other Receivables [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Notes receivable	$ 12,293	$ 16,629