Represents the amount of quarterly fee for asset management consulting services.

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Revenue derived from construction, architectural services and supervision of capital projects provided under contracts or arrangements with clients.

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Represents the amount aggregate cost of construction, architectural services and supervision of capital projects during the reporting period.

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Represents the expenses incurred for attendance and participation in Advisory Committee meeting.

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Represents the number of limited partnerships and limited liability companies in which the entity has made investments which are accounted for using the equity method of consolidation.

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This element represents the amount of management fee incurred for payment to a management company during the reporting period.

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Represents the number of Advisory Committee meeting held during the reporting period.

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Represents the number of Audit Committee meeting held during the period.

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Number of employees, excluding President, having ownership interest in the investment properties.

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The amount of revenue derived from managing real estate properties and from providing other services which may include construction, architectural services, supervision of capital projects, repairs and maintenance, and administrative services.

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The percentage of ownership of common stock or equity participation in the investee by related party.

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Represents the amount of expense charged to entity for bookkeeping and accounting services under terms of agreement with related parties, included within administrative costs.

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Represents the management fee expressed as a percentage of rental revenues from properties owned.

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Represents the number of employees who perform accounting and bookkeeping functions.

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Amounts charged by related party for services provided during the financial reporting period, excluding management fee. Services may include legal, accounting, administrative, repairs and maintenance, construction, rental and architectural services and supervision of capital projects.

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Amount of revenue from providing administrative services, including, but not limited to, accounting, tax, legal, regulatory filing, and share registration activities of managed funds and investment accounts of independent third parties and related and affiliated entities.

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The aggregate costs related to asset management during the reporting period.

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The aggregate costs of keeping the property in good condition but that do not appreciably prolong the life or increase the value of the property.

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Face (par) amount of debt instrument at time of issuance.

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Contractual interest rate for funds borrowed, under the debt agreement.

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Amount of cost for defined contribution plan.

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The percentage of ownership of common stock or equity participation in the investee accounted for under the equity method of accounting.

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The aggregate total of expenses of managing and administering the affairs of an entity, including affiliates of the reporting entity, which are not directly or indirectly associated with the manufacture, sale or creation of a product or product line.

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Amount of the cost of borrowed funds accounted for as interest expense.

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Revenue derived from maintenance services provided under contracts or arrangements with clients. For example, it may include the maintenance of software, plant and equipment, and facilities.

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The amount of cash paid for brokerage fees during the current period. This element is intended to represent the brokerage fees paid by and between financial industry participants.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
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The percentage charged for managing real estate properties.

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The amount of revenue derived from managing real estate properties.

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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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RELATED PARTY TRANSACTIONS (Details)	12 Months Ended
RELATED PARTY TRANSACTIONS (Details)	Dec. 31, 2017 USD ($) item	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)	Sep. 29, 2017 USD ($)	Jul. 16, 2017 USD ($)	Jul. 06, 2017 USD ($)
RELATED PARTY TRANSACTIONS
Management fee	$ 2,159,458	$ 2,029,171	$ 1,869,977
Repairs and maintenance	8,378,639	8,258,263	6,998,592
Administrative expense	$ 2,008,107	2,102,812	2,096,290
Number of advisory committee meetings \| item	4
Expenses incurred for advisory committee meeting	$ 19,000
Number of audit committee meetings held \| item	4
Expenses incurred for audit committee meeting	$ 12,000
Interest expense	$ 11,114,146	10,200,393	9,980,359
Majority of Partnership Properties, Excluding Linewt
RELATED PARTY TRANSACTIONS
Management fee as percentage of gross receipts rental revenue	4.00%
Hamilton Linewt LLC Commercial-1031 Exchange Newton, Massachusetts
RELATED PARTY TRANSACTIONS
Management fee as percentage of gross receipts rental revenue	3.00%
Woodland Park Apartments LLC Newton Massachusetts
RELATED PARTY TRANSACTIONS
Loan amount					$ 22,250,000	$ 16,000,000	$ 16,000,000
Interest rate (as a percent)					3.79%	4.75%
Interest expense	$ 182,000
Investment Properties
RELATED PARTY TRANSACTIONS
Number of limited partnerships and limited liability companies in which the entity has invested \| item	9
Investment Properties \| Minimum
RELATED PARTY TRANSACTIONS
Ownership interest (as a percent)	40.00%
Investment Properties \| Maximum
RELATED PARTY TRANSACTIONS
Ownership interest (as a percent)	50.00%
Hamilton Company/Management Company
RELATED PARTY TRANSACTIONS
Employer contributions in 401K plan		0	0	$ 0
Number of accounting staff of related party providing bookkeeping and accounting functions \| item	14
Number of employees having ownership interest in the investment properties \| item	5
Hamilton Company/Management Company, Related Party
RELATED PARTY TRANSACTIONS
Management fee	$ 2,159,000	2,029,000	1,870,000
Related Party Transaction, Services, Excluding Management Fee	882,000	1,069,000	994,000
Repairs and maintenance	295,000
Administrative expense	359,000
Construction, architectural services and supervision of capital projects	227,000
Commercial brokerage fees	1,000
Reimbursement to related party for payroll transfers	3,463,000	3,076,000	2,958,000
Fees for accounting and bookkeeping services		125,000	125,000	125,000
Investment Properties \| Hamilton Company/Management Company
RELATED PARTY TRANSACTIONS
Property Management Fee Revenue And Other Service Revenue	1,377,000
Amount received for management fees	673,000
Amount received for construction, architectural services and supervision of capital projects	620,000
Amount received for maintenance	44,000
Amount received for administrative services	$ 40,000
Number of employees having ownership interest in the investment properties \| item	5
Investment Properties, Excluding Dexter Park \| Hamilton Company/Management Company
RELATED PARTY TRANSACTIONS
Property management fee received (as a percent)	4.00%
Dexter Park \| Hamilton Company/Management Company
RELATED PARTY TRANSACTIONS
Property management fee received (as a percent)	2.00%
President of Management Company
RELATED PARTY TRANSACTIONS
Quarterly fee for asset management consulting services		18,750	18,750	18,750
Fee for asset management consulting services		$ 75,000	$ 75,000	$ 75,000
Harold Brown \| Investment Properties \| Minimum
RELATED PARTY TRANSACTIONS
Ownership interest of related party (as a percent)	43.20%
Harold Brown \| Investment Properties \| Maximum
RELATED PARTY TRANSACTIONS
Ownership interest of related party (as a percent)	56.00%
Residential and mixed-use properties \| Partially owned properties \| Minimum
RELATED PARTY TRANSACTIONS
Ownership interest (as a percent)	40.00%
Residential and mixed-use properties \| Partially owned properties \| Investment Properties \| Minimum
RELATED PARTY TRANSACTIONS
Ownership interest (as a percent)	40.00%
Residential and mixed-use properties \| Partially owned properties \| Investment Properties \| Maximum
RELATED PARTY TRANSACTIONS
Ownership interest (as a percent)	50.00%