Notes and Other Receivables - Allowance for Credit Loss (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	$ 751
Provision for credit losses	107	$ (97)
Ending balance	740
Mezzanine Loans
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	751
Provision for credit losses	(37)
Ending balance	714
Bridge Loans
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	0
Provision for credit losses	26
Ending balance	26
Mezzanine and Bridge Loans
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	751
Provision for credit losses	(11)
Ending balance	$ 740