REAL ESTATE PROPERTIES (Details)		3 Months Ended		9 Months Ended
		Sep. 30, 2020 USD ($)	Sep. 30, 2019 USD ($)	Sep. 30, 2020 USD ($) Integer	Sep. 30, 2019 USD ($)	Dec. 31, 2019 USD ($)	Jun. 30, 2019 USD ($)	Jan. 01, 2019 USD ($)
Real Estate Properties [Line Items]
Number of Reporting Units | Integer				1
Depreciation Expense During the Period		$ 24,087,000	$ 21,384,000	$ 70,989,000	$ 63,650,000
Percentage of occupancy to qualify as value-add property				75.00%
Percentage of acquisition price to be spent on capital items to qualify as value-add property				20.00%
Real Estate Properties
Land		488,698,000		$ 488,698,000		$ 452,698,000
Building and building improvements		2,080,785,000		2,080,785,000		1,907,963,000
Tenant and other improvements		517,032,000		517,032,000		471,909,000
Right of use assets - Ground leases (operating)	[1]	11,303,000		11,303,000		11,997,000
Development and value-add properties	[2]	324,841,000		324,841,000		419,999,000
Real estate, development and value-add properties		3,422,659,000		3,422,659,000		3,264,566,000
Less accumulated depreciation		(940,223,000)		(940,223,000)		(871,139,000)
Real estate, net		2,482,436,000		$ 2,482,436,000		$ 2,393,427,000
Ground Leases Disclosures [Abstract]
Incremental borrowing rate used in determining the present value of lease payments								7.30%
Building [Member]
Real Estate Properties [Line Items]
Property, Plant and Equipment, Useful Life				40 years
Minimum [Member] | Improvements [Member]
Real Estate Properties [Line Items]
Property, Plant and Equipment, Useful Life				3 years
Maximum [Member] | Improvements [Member]
Real Estate Properties [Line Items]
Property, Plant and Equipment, Useful Life				15 years
Accounting Standards Update 2016-02 [Member]
Real Estate Properties
Right of use assets - Ground leases (operating)								$ 10,226,000
Ground leases [Member]
Ground Leases Disclosures [Abstract]
Leases terms minimum				40 years
Leases terms maximum				50 years
Renewal period option minimum				15 years
Renewal period option maximum				35 years
Total ground lease expenditures for continuing and discontinued operations		266,000	$ 261,000	$ 789,000	$ 705,000
Payment increase interval minimum				3 years
Payment increase interval maximum				10 years
Weighted Average term for ground leases				43 years
Operating Leases, Future Minimum Payments Due, Next Twelve Months		242,000		$ 242,000
Operating Leases, Future Minimum Payments, Due in Two Years		970,000		970,000
Operating Leases, Future Minimum Payments, Due in Three Years		970,000		970,000
Operating Leases, Future Minimum Payments, Due in Four Years		975,000		975,000
Operating Leases, Future Minimum Payments, Due in Five Years		999,000		999,000
Operating Leases, Future Minimum Payments, Due Thereafter		38,916,000		38,916,000
Operating leases, future minimum payments due, total		43,072,000		43,072,000
Imputed interest related to right of use assets for ground leases	[3]	(31,662,000)		(31,662,000)
Ground Leases, Net		$ 11,410,000		$ 11,410,000
Ground leases [Member] | FLORIDA
Ground Leases Disclosures [Abstract]
Properties subject to ground leases		2		2
Ground leases [Member] | TEXAS
Ground Leases Disclosures [Abstract]
Properties subject to ground leases		3		3
Ground leases [Member] | ARIZONA
Ground Leases Disclosures [Abstract]
Properties subject to ground leases		1		1
Logistics Center 6 & 7 [Member]
Real Estate Properties
Right of use assets - Ground leases (operating)							$ 2,679,000
Ground Leases Disclosures [Abstract]
Incremental borrowing rate used in determining the present value of lease payments							8.00%

[1] See below for information regarding the Company’s right of use assets for ground leases.

[2] Value-add properties are defined as properties that are either acquired but not stabilized or can be converted to a higher and better use.  Acquired properties meeting either of the following two conditions are considered value-add properties:  (1) Less than 75% occupied as of the acquisition date (or will be less than 75% occupied within one year of acquisition date based on near term lease roll), or (2) 20% or greater of the acquisition cost will be spent to redevelop the property. 

[3] As the Company’s leases do not provide an implicit rate, in order to calculate the present value of the remaining ground lease payments, the Company used its incremental borrowing rate, adjusted for a number of factors, including the long-term nature of the ground leases, the Company’s estimated borrowing costs, and the estimated fair value of the underlying land, to determine the imputed interest for its ground leases. The Company elected to use the portfolio approach as all of its ground leases in place as of January 1, 2019, have similar characteristics and determined 7.3% as the appropriate rate as of January 1, 2019, for all leases in place at that time. For the ground lease acquired during April 2019, the Company used its incremental borrowing rate, adjusted for the factors discussed above, which was determined to be 8.0%.