Represents the number of states in which the entity owns real estate properties as of the balance sheet date.

No definition available.

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- Definition

For an unclassified balance sheet, the amount due from customers or clients for goods or services that have been delivered or sold in the normal course of business, reduced to their estimated net realizable fair value by an allowance established by the entity of the amount it deems uncertain of collection.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(3))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(4))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(9))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(5))
-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

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.

+ References

No definition available.

+ Details

Name:	us-gaap_ConcentrationRiskLineItems
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Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

For an entity that discloses a concentration risk in relation to quantitative amount, which serves as the "benchmark" (or denominator) in the equation, this concept represents the concentration percentage derived from the division.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 275
-SubTopic 10
-Section 50
-Paragraph 18
-URI http://asc.fasb.org/extlink&oid=84177426&loc=d3e6351-108592

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 20
-URI http://asc.fasb.org/extlink&oid=77997519&loc=d3e13531-108611

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 275
-SubTopic 10
-Section 50
-Paragraph 20
-URI http://asc.fasb.org/extlink&oid=84177426&loc=d3e6404-108592

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 21
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=77997519&loc=d3e13537-108611

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

The number of real estate properties owned as of the balance sheet date.

+ References

No definition available.

+ Details

Name:	us-gaap_NumberOfRealEstateProperties
Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

CONCENTRATIONS (Details) $ in Thousands	12 Months Ended
CONCENTRATIONS (Details) $ in Thousands	Dec. 31, 2017 USD ($) property state	Dec. 31, 2016 USD ($) property state	Dec. 31, 2015 property state
Concentrations
Number of states in which properties are owned \| state	2	4	4
Office properties
Concentrations
Number of real estate properties owned	15	20	20
Multifamily properties
Concentrations
Number of real estate properties owned	0	5	5
Hotel properties
Concentrations
Number of real estate properties owned	1	1	3
Parking garages
Concentrations
Number of real estate properties owned	2	3	3
Development site
Concentrations
Number of real estate properties owned	2	2	2
Parking lot
Concentrations
Number of real estate properties owned	1	1	1
Revenues \| Tenant revenue concentrations \| Governmental Tenants
Concentrations
Concentration risk, percent	21.40%	19.90%	22.70%
Amount due from Governmental Tenants \| $	$ 5,130	$ 8,339
Revenues \| Geographical concentrations
Concentrations
Concentration risk, percent	100.00%	100.00%	100.00%
Revenues \| Geographical concentrations \| California
Concentrations
Concentration risk, percent	63.20%	63.40%	62.20%
Revenues \| Geographical concentrations \| Washington, D.C.
Concentrations
Concentration risk, percent	25.10%	21.30%	24.20%
Revenues \| Geographical concentrations \| Texas
Concentrations
Concentration risk, percent	6.90%	8.20%	7.80%
Revenues \| Geographical concentrations \| North Carolina
Concentrations
Concentration risk, percent	3.10%	5.20%	4.60%
Revenues \| Geographical concentrations \| New York
Concentrations
Concentration risk, percent	1.70%	1.90%	1.20%
Real estate investments \| Geographical concentrations
Concentrations
Concentration risk, percent	100.00%	100.00%
Real estate investments \| Geographical concentrations \| California
Concentrations
Concentration risk, percent	66.40%	50.80%
Real estate investments \| Geographical concentrations \| Washington, D.C.
Concentrations
Concentration risk, percent	31.20%	32.30%
Real estate investments \| Geographical concentrations \| Texas
Concentrations
Concentration risk, percent	2.40%	7.70%
Real estate investments \| Geographical concentrations \| North Carolina
Concentrations
Concentration risk, percent	0.00%	5.50%
Real estate investments \| Geographical concentrations \| New York
Concentrations
Concentration risk, percent	0.00%	3.70%