Debt Instrument, Weight Average Life

No definition available.

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- Definition

All in-rate of derivative that includes the fixed rate and credit spread. The credit spread is based on the entity's certain threshold, for instance, leverage ratio.

+ References

No definition available.

+ Details

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Period Type:	instant

- Definition

Represents the amount of accrued interest and unused commitment fee payable as of the balance sheet date.

+ References

No definition available.

+ Details

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- Definition

Represents the period that the credit facility may be extended under certain circumstances.

+ References

No definition available.

+ Details

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- Definition

Number of extensions of a contract.

+ References

No definition available.

+ Details

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- Definition

Number of mortgage loan agreements entered into during the period.

+ References

No definition available.

+ Details

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- Definition

Aggregate notional amount specified by the derivative(s). Expressed as an absolute value.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Article 12
-Section 13
-Sentence Column B

+ Details

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Period Type:	instant

- Definition

Amount of accumulated amortization of debt issuance costs.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=64930785&loc=d3e28555-108399

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 210.5-02.17)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

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

- Definition

Percentage points added to the reference rate to compute the variable rate on the debt instrument.

+ References

No definition available.

+ Details

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Data Type:	num:percentItemType
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Period Type:	duration

- Definition

Amount, before unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but is not limited to, notes payable, bonds payable, commercial loans, mortgage loans, convertible debt, subordinated debt and other types of debt.

+ 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(22))
-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 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(16))
-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

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(16))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

+ Details

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

- Definition

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

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 55
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=64930739&loc=d3e28878-108400

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=64930785&loc=d3e28551-108399

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of the fee that accompanies borrowing money under the debt instrument.

+ References

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Effective interest rate for the funds borrowed under the debt agreement considering interest compounding and original issue discount or premium.

+ References

+ Details

Name:	us-gaap_DebtInstrumentInterestRateEffectivePercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
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

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Balance Type:	na
Period Type:	duration

- Definition

Amount, before accumulated amortization, of debt issuance costs. Includes, but is not limited to, legal, accounting, underwriting, printing, and registration costs.

+ References

+ Details

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

- Definition

Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

+ References

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of borrowing capacity currently available under the credit facility (current borrowing capacity less the amount of borrowings outstanding).

+ References

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The fee, expressed as a percentage of the line of credit facility, for available but unused credit capacity under the credit facility.

+ References

No definition available.

+ Details

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

- Definition

Amount of cash outflow for cost from early extinguishment and prepayment of debt. Includes, but is not limited to, third-party cost, premium paid, and other fee paid to lender directly for debt extinguishment or debt prepayment. Excludes accrued interest.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 15
-Subparagraph (g)
-URI http://asc.fasb.org/extlink&oid=98514028&loc=d3e3291-108585

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The cash inflow from a borrowing supported by a written promise to pay an obligation.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 14
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=98514028&loc=d3e3255-108585

+ Details

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

- Definition

The cash outflow during the period from the repayment of aggregate short-term and long-term debt. Excludes payment of capital lease obligations.

+ References

No definition available.

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The cash outflow from the repayment of a long-term debt instrument issued, secured by a first mortgage deed of trust, containing a pledge of real property. The lender has the highest claim on the property in case of default.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 15
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=98514028&loc=d3e3291-108585

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Write-off of amounts previously capitalized as debt issuance cost in an extinguishment of debt.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 225
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03.8)
-URI http://asc.fasb.org/extlink&oid=63488584&loc=d3e20235-122688

+ Details

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Data Type:	xbrli:monetaryItemType
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- Details

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- Details

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- Details

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- Details

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DEBT - Narrative (Details)							1 Months Ended			6 Months Ended
DEBT - Narrative (Details)	May 30, 2018 USD ($)	Nov. 29, 2017 USD ($)	Aug. 03, 2017 USD ($)	Jun. 23, 2017 USD ($)	May 30, 2017 USD ($)	Mar. 28, 2017 USD ($)	Jun. 30, 2016 USD ($) agreement	May 31, 2015 USD ($)	Sep. 30, 2014 USD ($) extension_option	Jun. 30, 2018 USD ($)	Jun. 30, 2017 USD ($)	Dec. 31, 2017 USD ($)	Aug. 31, 2017 USD ($)	Aug. 13, 2015 USD ($)
Debt
Deferred loan costs, gross										$ 4,914,000		$ 3,843,000
Deferred loan costs, accumulated amortization										1,491,000		1,105,000
Issuance of notes										38,200,000	$ 0
Accrued interest and unused commitment fee payable										2,139,000		$ 2,098,000
Disposal Group, Disposed of by Sale, Not Discontinued Operations \| 211 Main Street, San Francisco, CA
Debt
Payment of mortgages payable						$ 25,331,000
Mortgage prepayment penalty						$ 1,508,000
Disposal Group, Disposed of by Sale, Not Discontinued Operations \| 3636 McKinney Avenue and 3839 McKinney Avenue, Dallas, TX
Debt
Payment of mortgages payable					$ 15,448,000
Mortgage prepayment penalty					$ 1,901,000
Disposal Group, Disposed of by Sale, Not Discontinued Operations \| 4649 Cole Avenue, Dallas, TX
Debt
Payment of mortgages payable				$ 23,333,000
Mortgage prepayment penalty				$ 2,812,000
Interest Rate Swap
Debt
Total notional amount														$ 385,000,000
Interest Rate Swap \| Designated as Hedging Instrument \| Cash Flow Hedges
Debt
Total notional amount										$ 170,000,000
Weighted Average \| Interest Rate Swap \| Designated as Hedging Instrument \| Cash Flow Hedges
Debt
All-in rate										3.16%		3.16%
Unsecured credit facility entered into in September 2014
Debt
Maximum borrowing capacity									$ 850,000,000
Number of extension options \| extension_option									2
Line of credit facility extension option term									1 year
Amount available for future borrowings										$ 200,000,000		$ 200,000,000
Extension fee													$ 300,000
Unsecured credit facility entered into in September 2014, revolver
Debt
Maximum borrowing capacity									$ 450,000,000	200,000,000
Unsecured credit facility entered into in September 2014, revolver \| Minimum
Debt
Interest rate margin									0.20%
Unused commitment fee									0.15%
Unsecured credit facility entered into in September 2014, revolver \| Maximum
Debt
Interest rate margin									1.00%
Unused commitment fee									0.25%
Unsecured credit facility entered into in September 2014, revolver \| LIBOR \| Minimum
Debt
Interest rate margin									1.20%
Unsecured credit facility entered into in September 2014, revolver \| LIBOR \| Maximum
Debt
Interest rate margin									2.00%
Unsecured credit facility entered into in September 2014, term loan
Debt
Maximum borrowing capacity									$ 325,000,000
Unsecured credit facility entered into in September 2014, term loan \| LIBOR \| Minimum
Debt
Interest rate margin									1.15%
Unsecured credit facility entered into in September 2014, term loan \| LIBOR \| Maximum
Debt
Interest rate margin									1.95%
Unsecured credit facility entered into in September 2014, term loan \| Base rate \| Minimum
Debt
Interest rate margin									0.15%
Unsecured credit facility entered into in September 2014, term loan \| Base rate \| Maximum
Debt
Interest rate margin									0.95%
Unsecured credit facility entered into in September 2014, delayed-draw term loan
Debt
Maximum borrowing capacity									$ 75,000,000
Mortgages Payable
Debt
Number of mortgage loan agreements entered into \| agreement							6
Amount of loan							$ 392,000,000
Gross debt										416,300,000		416,300,000
Unsecured credit facilities
Debt
Gross debt										0		0
Unsecured Term Loan Facility Entered Into May 2015
Debt
Deferred loan costs, accumulated amortization		$ 512,000	$ 193,000
Maximum borrowing capacity								$ 385,000,000
Amount of loan										$ 170,000,000		$ 170,000,000
Interest rate										3.58%		2.96%
Repayments of debt		150,000,000	65,000,000
Write off of deferred loan costs		$ 1,387,000	$ 601,000
Unsecured Term Loan Facility Entered Into May 2015 \| LIBOR \| Minimum
Debt
Interest rate margin								1.60%
Unsecured Term Loan Facility Entered Into May 2015 \| LIBOR \| Maximum
Debt
Interest rate margin								2.25%
Unsecured Term Loan Facility Entered Into May 2015 \| Base rate \| Minimum
Debt
Interest rate margin								0.60%
Unsecured Term Loan Facility Entered Into May 2015 \| Base rate \| Maximum
Debt
Interest rate margin								1.25%
Loan backed notes
Debt
Gross debt										$ 37,603,000		$ 0
Issuance of notes	$ 38,200,000
Weighted average life of notes	3 years
Loan backed notes \| LIBOR
Debt
Interest rate margin	1.40%									1.40%
Loan backed notes \| Prime rate
Debt
Interest rate margin	(1.08%)									(1.08%)