Mortgages Payable - Summary of Mortgages Payable (Details) - Mortgages Payable $ in Thousands	3 Months Ended	9 Months Ended
	Mar. 31, 2020	Sep. 30, 2020 USD ($) property mortgage	Dec. 31, 2019 USD ($) mortgage property
Debt
Number of Properties | property		72	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	3 years 1 month 6 days	2 years 10 months 24 days
Remaining Principal Balance		$ 334,709	$ 408,419
Unamortized Premium and Deferred Finance Costs Balance, net		885	1,700
Net payable amount		$ 335,594	$ 410,119
Number of mortgages | mortgage		22	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		$ 6,900	$ 7,100
Number of mortgages | mortgage		1	1