Mortgages Payable - Maturities (Details) - Mortgages Payable - USD ($)	Mar. 31, 2018	Dec. 31, 2017
Debt
Unamortized premium balance	$ 5,400,000
Remaining balance of deferred financing costs at period end	223,000	$ 236,000
Maturity of mortgages payable, excluding net premiums
2018	9,600,000
2019	20,700,000
2020	82,400,000
2021	67,000,000
2022	109,700,000
Thereafter	18,600,000
Totals	$ 308,000,000