Notes Receivable and Current Expected Credit Losses (Schedule of Interest on the Mezzanine Loans) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Accounts, Notes, Loans and Financing Receivable [Line Items]
Interest income	$ 4,116	$ 7,226
Mezzanine Loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Interest income	4,013	7,203
Other Notes Receivable
Accounts, Notes, Loans and Financing Receivable [Line Items]
Interest income	103	23
The Residences at Annapolis Junction | Mezzanine Loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Interest income	0	2,468
Delray Beach Plaza | Mezzanine Loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Interest income	0	489
Nexton Square | Mezzanine Loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Interest income	0	391
Interlock Commercial | Mezzanine Loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Interest income	3,075	3,017
Solis Apartments at Interlock | Mezzanine Loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Interest income	$ 938	$ 838