Mortgages Payable - Summary of Mortgages Payable (Details) - Mortgages Payable $ in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2020 USD ($) property mortgage	Dec. 31, 2019 USD ($) mortgage property
Debt
Number of Properties | property	91	92
Weighted Average Stated Interest Rate (as a percent)	4.90%	4.90%
Weighted Average Effective Interest Rate (as a percent)	4.60%	4.60%
Weighted Average Remaining Years Until Maturity	2 years 8 months 12 days	3 years 1 month 6 days
Remaining Principal Balance	$ 393,690	$ 408,419
Unamortized Premium and Deferred Finance Costs Balance, net	1,126	1,700
Net payable amount	$ 394,816	$ 410,119
Number of mortgages | mortgage	26	27
Minimum
Debt
Weighted Average Effective Interest Rate (as a percent)	3.80%	3.80%
Stated interest rate (as a percent)	3.80%	3.80%
Maximum
Debt
Weighted Average Effective Interest Rate (as a percent)	7.60%	7.60%
Stated interest rate (as a percent)	6.90%	6.90%
Variable rate mortgages
Debt
Number of Properties | property	1	1
Remaining Principal Balance	$ 7,000	$ 7,100
Number of mortgages | mortgage	1	1