Mortgages Payable (Details) - USD ($)	Dec. 31, 2017	Dec. 31, 2016
Debt Instrument [Line Items]
Accumulated amortization	$ 12,667,000	$ 11,268,000
Debt costs, net of accumulated amortization	(5,380,000)	(2,715,000)
Long-term Debt, Fiscal Year Maturity [Abstract]
Mortgages payable, including unamortized premium and net of unamortized debt costs	13,300,000	13,878,000
Mortgages
Debt Instrument [Line Items]
Debt costs	(147,000)	(147,000)
Accumulated amortization	55,000	38,000
Debt costs, net of accumulated amortization	(92,000)	(109,000)
Mortgages payable, including unamortized premium and net of unamortized debt costs	13,300,000	13,878,000
Long-term Debt, Fiscal Year Maturity [Abstract]
2018	623,000
2019	652,000
2020	682,000
2021	716,000
2022	750,000
Thereafter	9,969,000
Mortgages payable, including unamortized premium and net of unamortized debt costs	13,392,000
Mortgages | November 2014
Debt Instrument [Line Items]
Initial Balance	$ 15,151,000
Interest Rate	5.23%
Carrying Value of Encumbered Asset(s)	$ 20,917,000
Outstanding Principal Balance	$ 13,392,000	$ 13,987,000