COMMITMENTS AND CONTINGENCIES (Details) - 62 Boylston Street in Boston, MA	12 Months Ended
Dec. 31, 2017 USD ($)	Nov. 19, 2016 item
Loss Contingencies [Line Items]
Number of apartments damaged \| item		24
Proceeds from Insurance \| $	$ 329,000

Amount of cash inflow for proceeds from settlement of insurance claim, classified as operating activities. Excludes insurance settlement classified as investing activities.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 21B
-URI http://asc.fasb.org/extlink&oid=98514028&loc=SL94080549-108585

Name:	us-gaap_ProceedsFromInsuranceSettlementOperatingActivities
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration