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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

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Period between issuance and maturity of long-term debt, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

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The number of units in a real estate property owned as of the balance sheet date.

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The cash outflow to repay long-term debt that is wholly or partially secured by collateral. Excludes repayments of tax exempt secured debt.

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MORTGAGE NOTES PAYABLE (Mortgage by property) (Details)		3 Months Ended
MORTGAGE NOTES PAYABLE (Mortgage by property) (Details)	Mar. 31, 2020 USD ($) property	Mar. 31, 2020 USD ($) property	Mar. 31, 2021 USD ($) property	Aug. 31, 2014	Dec. 31, 2005	Mar. 07, 2005 item
MORTGAGE NOTES PAYABLE
Repayment of loan		$ 1,000,000
Loan balance			$ 284,237,000
Hamilton Essex 81
MORTGAGE NOTES PAYABLE
Number of units	49	49	49			48
Loan balance			$ 10,000,000
Brookside Associates LLC Residential Apartments Woburn, Massachusetts
MORTGAGE NOTES PAYABLE
Loan amount	$ 6,175,000	$ 6,175,000
Repayment of loan	2,390,000
Closing Costs	$ 136,000
Interest rate (as a percent)	3.53%	3.53%
Mortgages payable \| Hamilton on Main Apartments, LLC
MORTGAGE NOTES PAYABLE
Interest rate (as a percent)				4.34%	5.18%
Amortization period of debt					30 years
Debt Instrument, Amortization Term					30 years
Mortgages payable \| Minimum
MORTGAGE NOTES PAYABLE
Interest rate (as a percent)			3.53%
Mortgages payable \| Maximum
MORTGAGE NOTES PAYABLE
Interest rate (as a percent)			5.66%