Debt Obligations - Credit Facility (Details) - USD ($)		3 Months Ended		6 Months Ended
	Apr. 18, 2019	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Apr. 30, 2021	Dec. 31, 2020
Debt Instrument [Line Items]
Deferred costs		$ 740,000		$ 740,000			$ 880,000
Line of Credit | Valley National Bank | Credit Facility, Maturing April 2021 | Secured Debt
Debt Instrument [Line Items]
Debt assumed, face value	$ 15,000,000
Effective interest rate		4.25%		4.25%
Amortization of deferred fees and unused fees		$ 19,000	$ 47,000
Interest expense				$ 36,000	$ 62,000
Deferred costs		30,000		30,000			$ 12,000
Unused borrowing capacity fee, percentage	0.25%
Facility amount drawn		$ 0		$ 0		$ 0
Line of Credit | Valley National Bank | Credit Facility, Maturing April 2021 | Secured Debt | Prime Rate
Debt Instrument [Line Items]
Basis spread on variable rate	0.50%
Line of Credit | Valley National Bank | Credit Facility, Maturing April 2021 | Secured Debt | Floor
Debt Instrument [Line Items]
Basis spread on variable rate	4.25%