Mortgages Payable (Details)	Dec. 31, 2020 USD ($) property	Dec. 31, 2019 USD ($)
Debt Instrument [Line Items]
Accumulated amortization	$ 17,294,000	$ 15,574,000
Debt costs, net of accumulated amortization	(1,917,000)	(2,783,000)
Long-term Debt, Fiscal Year Maturity [Abstract]
Mortgages payable, including unamortized premium and net of unamortized debt costs	11,395,000	12,059,000
Mortgages
Debt Instrument [Line Items]
Debt costs	(147,000)	(147,000)
Accumulated amortization	108,000	90,000
Debt costs, net of accumulated amortization	(39,000)	(57,000)
Mortgages payable, including unamortized premium and net of unamortized debt costs	11,395,000	12,059,000
Long-term Debt, Fiscal Year Maturity [Abstract]
2021	716,000
2022	750,000
2023	9,968,000
Mortgages payable, including unamortized premium and net of unamortized debt costs	11,434,000
Mortgages | November 2014
Debt Instrument [Line Items]
Initial Balance	$ 15,151,000
Interest Rate	5.23%
Carrying Value of Encumbered Asset(s)	$ 19,458,000
Outstanding Principal Balance	$ 11,434,000	$ 12,116,000
Number of encumbered assets | property	5