Notes Receivable and Current Expected Credit Losses (Schedule of Interest on the Mezzanine Loans) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Accounts, Notes, Loans and Financing Receivable [Line Items]
Interest income	$ 6,746	$ 4,412	$ 10,862	$ 11,638
Mezzanine Loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Interest income	6,639	4,400	10,650	11,604
Other Notes Receivable
Accounts, Notes, Loans and Financing Receivable [Line Items]
Interest income	107	12	212	34
The Residences at Annapolis Junction | Mezzanine Loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Interest income	0	0	0	2,468
Delray Beach Plaza | Mezzanine Loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Interest income	0	0	0	489
Nexton Multifamily | Mezzanine Loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Interest income	261	0	261	0
Nexton Square | Mezzanine Loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Interest income	0	405	0	797
Interlock Commercial | Mezzanine Loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Interest income	3,310	3,157	6,384	6,175
Solis Apartments at Interlock
Accounts, Notes, Loans and Financing Receivable [Line Items]
Prepayment premium received			2,400
Solis Apartments at Interlock | Mezzanine Loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Interest income	$ 3,068	$ 838	$ 4,005	$ 1,675