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Number of mortgage loan agreements entered into during the period.

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Amount of accumulated amortization of debt issuance costs.

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

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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.

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

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

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

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

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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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Weighted average interest rate of debt outstanding.

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

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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.

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

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

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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.

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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.

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DEBT - Narrative (Detail)					1 Months Ended
DEBT - Narrative (Detail)	Aug. 03, 2017 USD ($) swap	Jun. 23, 2017 USD ($)	May 30, 2017 USD ($)	Mar. 28, 2017 USD ($)	Jun. 30, 2016 USD ($) agreement	May 31, 2015 USD ($)	Sep. 30, 2014 USD ($) extension_option	Jul. 31, 2017 USD ($)	Jun. 30, 2017 USD ($)	Dec. 31, 2016 USD ($)	Nov. 02, 2015 USD ($)
Debt
Deferred loan costs, gross									$ 5,835,000	$ 7,122,000
Deferred loan costs, accumulated amortization									1,673,000	1,818,000
Accrued interest and unused commitment fee payable									2,765,000	3,133,000
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									89,000,000	200,000,000
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
Unused commitment fee							0.25%
Unsecured credit facilities
Debt
Gross debt									0	0
Mortgages Payable
Debt
Gross debt									$ 416,300,000	$ 532,437,000
Number of mortgage loan agreements entered into \| agreement					6
Amount of loan					$ 392,000,000
Unsecured Term Loan Facility Entered Into May 2015
Debt
Maximum borrowing capacity						$ 385,000,000
Unused commitment fee						0.20%
Amount of loan											$ 385,000,000
Prepayment fee						2.00%
Interest rate									2.65%	2.22%
Fixed interest rate									3.16%
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%
Unsecured term loan facility
Debt
Gross debt									$ 385,000,000	$ 385,000,000
Mortgage loan with a fixed interest of 6.65% per annum, due on July 15, 2018
Debt
Gross debt									0	$ 26,136,000
Fixed interest rate										6.65%
Mortgage loan with a fixed interest of 4.14% per annum, due on July 1, 2026
Debt
Gross debt									$ 370,300,000	$ 392,000,000
Fixed interest rate									4.14%
Mortgage loan with a fixed interest of 5.18% per annum, due on June 5, 2021
Debt
Gross debt									$ 0	$ 29,167,000
Fixed interest rate										5.18%
Disposal Group, Held-for-sale, Not Discontinued Operations \| Mortgage loan with a fixed interest of 4.14% per annum, due on July 1, 2026
Debt
Debt, gross									$ 21,700,000
Fixed interest rate									4.14%
Disposal Group, Held-for-sale, Not Discontinued Operations \| Mortgage loan with a fixed interest of 5.18% per annum, due on June 5, 2021
Debt
Fixed interest rate									5.18%
211 Main Street, San Francisco \| Disposal Group, Disposed of by Sale, Not Discontinued Operations
Debt
Payment of mortgages payable				$ 25,331,000
Mortgage prepayment penalty				$ 1,508,000
3636 McKinney Avenue and 3839 McKinney Avenue, Dallas, Texas \| Disposal Group, Disposed of by Sale, Not Discontinued Operations
Debt
Payment of mortgages payable			$ 15,448,000
Mortgage prepayment penalty			$ 1,901,000
4649 Cole Avenue, Dallas, Texas \| Disposal Group, Disposed of by Sale, Not Discontinued Operations
Debt
Payment of mortgages payable		$ 23,333,000
Mortgage prepayment penalty		$ 2,812,000
7083 Hollywood Boulevard \| Disposal Group, Held-for-sale, Not Discontinued Operations
Debt
Debt, gross									$ 21,700,000
4200 Scotland Street \| Disposal Group, Held-for-sale, Not Discontinued Operations
Debt
Debt, gross									$ 28,868,000
Subsequent Event
Debt
Number of swaps terminated \| swap	3
Notional amount of terminated swaps	$ 65,000,000
Payment of derivative fees and accrued interest	38,000
Subsequent Event \| Unsecured credit facility entered into in September 2014
Debt
Extension fee								$ 300,000
Subsequent Event \| Unsecured Term Loan Facility Entered Into May 2015
Debt
Repayments of debt	$ 65,000,000