Notes and Other Receivables - Allowance for Credit Loss (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	$ 751
Provision for credit losses	110	$ (100)
Ending balance	743
Mezzanine and Bridge Loans
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	751
Provision for credit losses	(8)
Ending balance	743
Mezzanine Loans
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	751
Provision for credit losses	(23)
Ending balance	728
Bridge Loans
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	0
Provision for credit losses	15
Ending balance	$ 15