Notes and Other Receivables (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Accounts, Notes, Loans and Financing Receivable [Line Items]
Notes receivable	$ 100,926	$ 40,970
Note receivable, secured, bearing interest at 10.00% due May 2021 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Notes receivable	$ 13,762	0
Stated interest rate (in hundredths)	10.00%
Note receivable, secured, bearing interest at 10.75%, due December 2020 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Notes receivable	$ 29,318	17,685
Stated interest rate (in hundredths)	10.75%
Related party note receivable, secured, bearing interest at 9.5%, due October 2019 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Notes receivable	$ 6,656	6,593
Stated interest rate (in hundredths)	9.50%
Secured Note Receivable, 3.5% Interest Rate, Due December 16, 2017 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Notes receivable	$ 29,500	0
Stated interest rate (in hundredths)	3.50%
Notes and other receivables from affiliates [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Notes receivable	$ 5,061	4,695
Other receivables [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Notes receivable	$ 16,629	$ 11,997