REAL ESTATE PROPERTIES 3 (Details)		12 Months Ended
		Dec. 31, 2015 USD ($) ft²	Dec. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)
DEVELOPMENT [Abstract]
Interest costs capitalized on development properties		$ 5,257,000	$ 4,942,000	$ 5,064,000
Internal Development Costs Capitalized During Period		4,467,000	4,040,000	3,730,000
Improvements on developments transferred to real estate properties		7,879,000
Development costs incurred, for the period		95,032,000	97,696,000	$ 76,240,000
Development		170,441,000	$ 179,973,000
Future Minimum payments receivable [Abstract]
2016		176,082,000
2017		144,173,000
2018		110,845,000
2019		84,253,000
2020		58,448,000
Thereafter		87,841,000
Total minimum receipts		$ 661,642,000
Lease Up [Member]
DEVELOPMENT [Abstract]
Size (Unaudited) (Square feet) | ft²		895,000
Development Costs Transferred	[1]	$ 2,807,000
Development costs incurred, for the period		30,284,000
Development		56,723,000
Estimated Total Cumulative Development Costs	[2]	$ 65,600,000
Under construction [Member]
DEVELOPMENT [Abstract]
Size (Unaudited) (Square feet) | ft²		770,000
Development Costs Transferred	[1]	$ 9,325,000
Development costs incurred, for the period		13,657,000
Development		22,982,000
Estimated Total Cumulative Development Costs	[2]	$ 48,300,000
Prospective Development [Member]
DEVELOPMENT [Abstract]
Size (Unaudited) (Square feet) | ft²		5,335,000
Development Costs Transferred	[1]	$ (18,292,000)
Development costs incurred, for the period		22,941,000
Development		$ 90,736,000
Prospective Development [Member] | Phoenix Area [Member]
DEVELOPMENT [Abstract]
Size (Unaudited) (Square feet) | ft²		261,000
Development Costs Transferred	[1]	$ (3,168,000)
Development costs incurred, for the period		3,192,000
Development		$ 3,487,000
Prospective Development [Member] | Tucson [Member]
DEVELOPMENT [Abstract]
Size (Unaudited) (Square feet) | ft²		70,000
Development Costs Transferred	[1]	$ 0
Development costs incurred, for the period		0
Development		$ 417,000
Prospective Development [Member] | Fort Myers [Member]
DEVELOPMENT [Abstract]
Size (Unaudited) (Square feet) | ft²		663,000
Development Costs Transferred	[1]	$ 0
Development costs incurred, for the period		0
Development		$ 17,858,000
Prospective Development [Member] | Orlando [Member]
DEVELOPMENT [Abstract]
Size (Unaudited) (Square feet) | ft²		912,000
Development Costs Transferred	[1]	$ (5,015,000)
Development costs incurred, for the period		1,535,000
Development		$ 20,371,000
Prospective Development [Member] | Tampa [Member]
DEVELOPMENT [Abstract]
Size (Unaudited) (Square feet) | ft²		290,000
Development Costs Transferred	[1]	$ (2,255,000)
Development costs incurred, for the period		710,000
Development		$ 4,639,000
Prospective Development [Member] | Jackson area [Member]
DEVELOPMENT [Abstract]
Size (Unaudited) (Square feet) | ft²		28,000
Development Costs Transferred	[1]	$ 0
Development costs incurred, for the period		0
Development		$ 706,000
Prospective Development [Member] | Charlotte [Member]
DEVELOPMENT [Abstract]
Size (Unaudited) (Square feet) | ft²		281,000
Development Costs Transferred	[1]	$ (1,273,000)
Development costs incurred, for the period		711,000
Development		$ 4,421,000
Prospective Development [Member] | Dallas [Member]
DEVELOPMENT [Abstract]
Size (Unaudited) (Square feet) | ft²		519,000
Development Costs Transferred	[1]	$ 0
Development costs incurred, for the period		6,477,000
Development		$ 8,126,000
Prospective Development [Member] | El Paso [Member]
DEVELOPMENT [Abstract]
Size (Unaudited) (Square feet) | ft²		251,000
Development Costs Transferred	[1]	$ 0
Development costs incurred, for the period		0
Development		$ 2,444,000
Prospective Development [Member] | Houston [Member]
DEVELOPMENT [Abstract]
Size (Unaudited) (Square feet) | ft²		1,607,000
Development Costs Transferred	[1]	$ (2,581,000)
Development costs incurred, for the period		5,458,000
Development		$ 24,587,000
Prospective Development [Member] | San Antonio [Member]
DEVELOPMENT [Abstract]
Size (Unaudited) (Square feet) | ft²		453,000
Development Costs Transferred	[1]	$ (4,000,000)
Development costs incurred, for the period		4,858,000
Development		$ 3,680,000
Development completed and transferred to Real estate properties [Member]
DEVELOPMENT [Abstract]
Size (Unaudited) (Square feet) | ft²		1,419,000
Development Costs Transferred	[1]	$ 6,160,000
Development costs incurred, for the period		20,395,000
Development	[3]	$ 96,809,000
Development completed and transferred to Real estate properties [Member] | West Road I [Member]
DEVELOPMENT [Abstract]
Size (Unaudited) (Square feet) | ft²		63,000
Development Costs Transferred	[1]	$ 0
Development costs incurred, for the period		662,000
Development	[3]	$ 4,939,000
Conversion date (or anticipated conversion date, if property is in lease-up or under construction)		10/15
Development completed and transferred to Real estate properties [Member] | Kyrene 202 I [Member]
DEVELOPMENT [Abstract]
Size (Unaudited) (Square feet) | ft²		75,000
Development Costs Transferred	[1]	$ 0
Development costs incurred, for the period		195,000
Development	[3]	$ 6,134,000
Conversion date (or anticipated conversion date, if property is in lease-up or under construction)		11/15
Development completed and transferred to Real estate properties [Member] | Ten West Crossing 6 [Member]
DEVELOPMENT [Abstract]
Size (Unaudited) (Square feet) | ft²		64,000
Development Costs Transferred	[1]	$ 0
Development costs incurred, for the period		470,000
Development	[3]	$ 4,712,000
Conversion date (or anticipated conversion date, if property is in lease-up or under construction)		10/15
Development completed and transferred to Real estate properties [Member] | World Houston 41 [Member]
DEVELOPMENT [Abstract]
Size (Unaudited) (Square feet) | ft²		104,000
Development Costs Transferred	[1]	$ 0
Development costs incurred, for the period		603,000
Development	[3]	$ 5,949,000
Conversion date (or anticipated conversion date, if property is in lease-up or under construction)		08/15
Development completed and transferred to Real estate properties [Member] | Steele Creek III [Member]
DEVELOPMENT [Abstract]
Size (Unaudited) (Square feet) | ft²		108,000
Development Costs Transferred	[1]	$ 0
Development costs incurred, for the period		(179,000)
Development	[3]	$ 7,141,000
Conversion date (or anticipated conversion date, if property is in lease-up or under construction)		02/15
Development completed and transferred to Real estate properties [Member] | Horizon II [Member]
DEVELOPMENT [Abstract]
Size (Unaudited) (Square feet) | ft²		123,000
Development Costs Transferred	[1]	$ 0
Development costs incurred, for the period		232,000
Development	[3]	$ 7,892,000
Conversion date (or anticipated conversion date, if property is in lease-up or under construction)		09/15
Development completed and transferred to Real estate properties [Member] | Sky Harbor 6 [Member]
DEVELOPMENT [Abstract]
Size (Unaudited) (Square feet) | ft²		31,000
Development Costs Transferred	[1]	$ 0
Development costs incurred, for the period		1,352,000
Development	[3]	$ 2,972,000
Conversion date (or anticipated conversion date, if property is in lease-up or under construction)		10/15
Development completed and transferred to Real estate properties [Member] | Horizon IV [Member]
DEVELOPMENT [Abstract]
Size (Unaudited) (Square feet) | ft²		123,000
Development Costs Transferred	[1]	$ 2,616,000
Development costs incurred, for the period		6,276,000
Development	[3]	$ 8,892,000
Conversion date (or anticipated conversion date, if property is in lease-up or under construction)		12/15
Development completed and transferred to Real estate properties [Member] | Horizon I [Member]
DEVELOPMENT [Abstract]
Size (Unaudited) (Square feet) | ft²		109,000
Development Costs Transferred	[1]	$ 0
Development costs incurred, for the period		(16,000)
Development	[3]	$ 7,096,000
Conversion date (or anticipated conversion date, if property is in lease-up or under construction)		02/15
Development completed and transferred to Real estate properties [Member] | Kyrene 202 II [Member]
DEVELOPMENT [Abstract]
Size (Unaudited) (Square feet) | ft²		45,000
Development Costs Transferred	[1]	$ 0
Development costs incurred, for the period		61,000
Development	[3]	$ 3,470,000
Conversion date (or anticipated conversion date, if property is in lease-up or under construction)		02/15
Development completed and transferred to Real estate properties [Member] | Steele Creek II [Member]
DEVELOPMENT [Abstract]
Size (Unaudited) (Square feet) | ft²		71,000
Development Costs Transferred	[1]	$ 0
Development costs incurred, for the period		22,000
Development	[3]	$ 4,945,000
Conversion date (or anticipated conversion date, if property is in lease-up or under construction)		03/15
Development completed and transferred to Real estate properties [Member] | World Houston 39 [Member]
DEVELOPMENT [Abstract]
Size (Unaudited) (Square feet) | ft²		94,000
Development Costs Transferred	[1]	$ 0
Development costs incurred, for the period		420,000
Development	[3]	$ 5,476,000
Conversion date (or anticipated conversion date, if property is in lease-up or under construction)		06/15
Development completed and transferred to Real estate properties [Member] | Rampart IV [Member]
DEVELOPMENT [Abstract]
Size (Unaudited) (Square feet) | ft²		84,000
Development Costs Transferred	[1]	$ 0
Development costs incurred, for the period		1,178,000
Development	[3]	$ 8,125,000
Conversion date (or anticipated conversion date, if property is in lease-up or under construction)		11/15
Development completed and transferred to Real estate properties [Member] | Oak Creek VIII [Member]
DEVELOPMENT [Abstract]
Size (Unaudited) (Square feet) | ft²		108,000
Development Costs Transferred	[1]	$ 2,255,000
Development costs incurred, for the period		3,074,000
Development	[3]	$ 5,329,000
Conversion date (or anticipated conversion date, if property is in lease-up or under construction)		12/15
Development completed and transferred to Real estate properties [Member] | Steele Creek IV [Member]
DEVELOPMENT [Abstract]
Size (Unaudited) (Square feet) | ft²		57,000
Development Costs Transferred	[1]	$ 0
Development costs incurred, for the period		736,000
Development	[3]	$ 4,196,000
Conversion date (or anticipated conversion date, if property is in lease-up or under construction)		12/15
Development completed and transferred to Real estate properties [Member] | World Houston 42 [Member]
DEVELOPMENT [Abstract]
Size (Unaudited) (Square feet) | ft²		94,000
Development Costs Transferred	[1]	$ 1,289,000
Development costs incurred, for the period		3,733,000
Development	[3]	$ 5,022,000
Conversion date (or anticipated conversion date, if property is in lease-up or under construction)		07/15
Development completed and transferred to Real estate properties [Member] | Thousand Oaks 4 [Member]
DEVELOPMENT [Abstract]
Size (Unaudited) (Square feet) | ft²		66,000
Development Costs Transferred	[1]	$ 0
Development costs incurred, for the period		1,576,000
Development	[3]	$ 4,519,000
Conversion date (or anticipated conversion date, if property is in lease-up or under construction)		10/15
Lease Up Construction And Prospective Development [Member]
DEVELOPMENT [Abstract]
Size (Unaudited) (Square feet) | ft²		7,000,000
Development Costs Transferred	[1]	$ (6,160,000)
Development costs incurred, for the period		66,882,000
Development		170,441,000
Development obligations		12,000,000
Tenant improvement obligations		$ 4,300,000
Alamo Ridge I [Member] | Lease Up [Member]
DEVELOPMENT [Abstract]
Size (Unaudited) (Square feet) | ft²		96,000
Development Costs Transferred	[1]	$ 0
Development costs incurred, for the period		1,877,000
Development		7,352,000
Estimated Total Cumulative Development Costs	[2]	$ 8,500,000
Conversion date (or anticipated conversion date, if property is in lease-up or under construction)		02/16
Alamo Ridge II [Member] | Lease Up [Member]
DEVELOPMENT [Abstract]
Size (Unaudited) (Square feet) | ft²		62,000
Development Costs Transferred	[1]	$ 0
Development costs incurred, for the period		773,000
Development		4,139,000
Estimated Total Cumulative Development Costs	[2]	$ 4,700,000
Conversion date (or anticipated conversion date, if property is in lease-up or under construction)		02/16
Madison II & III [Member] | Lease Up [Member]
DEVELOPMENT [Abstract]
Size (Unaudited) (Square feet) | ft²		127,000
Development Costs Transferred	[1]	$ 0
Development costs incurred, for the period		3,737,000
Development		7,417,000
Estimated Total Cumulative Development Costs	[2]	$ 8,000,000
Conversion date (or anticipated conversion date, if property is in lease-up or under construction)		02/16
West Road III [Member] | Lease Up [Member]
DEVELOPMENT [Abstract]
Size (Unaudited) (Square feet) | ft²		78,000
Development Costs Transferred	[1]	$ 0
Development costs incurred, for the period		917,000
Development		4,782,000
Estimated Total Cumulative Development Costs	[2]	$ 5,000,000
Conversion date (or anticipated conversion date, if property is in lease-up or under construction)		03/16
Ten West Crossing 7 [Member] | Lease Up [Member]
DEVELOPMENT [Abstract]
Size (Unaudited) (Square feet) | ft²		68,000
Development Costs Transferred	[1]	$ 0
Development costs incurred, for the period		902,000
Development		4,072,000
Estimated Total Cumulative Development Costs	[2]	$ 4,900,000
Conversion date (or anticipated conversion date, if property is in lease-up or under construction)		04/16
ParkView 1-3 [Member] | Lease Up [Member]
DEVELOPMENT [Abstract]
Size (Unaudited) (Square feet) | ft²		276,000
Development Costs Transferred	[1]	$ 0
Development costs incurred, for the period		13,180,000
Development		17,256,000
Estimated Total Cumulative Development Costs	[2]	$ 19,600,000
Conversion date (or anticipated conversion date, if property is in lease-up or under construction)		10/16
Alamo Ridge III [Member] | Under construction [Member]
DEVELOPMENT [Abstract]
Size (Unaudited) (Square feet) | ft²		135,000
Development Costs Transferred	[1]	$ 2,120,000
Development costs incurred, for the period		260,000
Development		2,380,000
Estimated Total Cumulative Development Costs	[2]	$ 12,200,000
Conversion date (or anticipated conversion date, if property is in lease-up or under construction)		10/16
35th Avenue Distribution Center [Member] | Under construction [Member]
DEVELOPMENT [Abstract]
Size (Unaudited) (Square feet) | ft²	[4]	124,000
Development Costs Transferred	[1],[4]	$ 0
Development costs incurred, for the period	[4]	1,171,000
Development	[4]	1,171,000
Estimated Total Cumulative Development Costs	[2],[4]	$ 1,200,000
Conversion date (or anticipated conversion date, if property is in lease-up or under construction)	[4]	01/17
Eisenhauer Point 1 & 2 [Member] | Under construction [Member]
DEVELOPMENT [Abstract]
Size (Unaudited) (Square feet) | ft²		201,000
Development Costs Transferred	[1]	$ 1,880,000
Development costs incurred, for the period		4,880,000
Development		6,760,000
Estimated Total Cumulative Development Costs	[2]	$ 13,500,000
Conversion date (or anticipated conversion date, if property is in lease-up or under construction)		02/17
Horizon III [Member] | Under construction [Member]
DEVELOPMENT [Abstract]
Size (Unaudited) (Square feet) | ft²		109,000
Development Costs Transferred	[1]	$ 2,399,000
Development costs incurred, for the period		3,716,000
Development		6,115,000
Estimated Total Cumulative Development Costs	[2]	$ 7,800,000
Conversion date (or anticipated conversion date, if property is in lease-up or under construction)		02/17
Ten Sky Harbor [Member] | Under construction [Member]
DEVELOPMENT [Abstract]
Size (Unaudited) (Square feet) | ft²		64,000
Development Costs Transferred	[1]	$ 1,653,000
Development costs incurred, for the period		1,999,000
Development		3,652,000
Estimated Total Cumulative Development Costs	[2]	$ 6,000,000
Conversion date (or anticipated conversion date, if property is in lease-up or under construction)		03/17
Steele Creek VI [Member] | Under construction [Member]
DEVELOPMENT [Abstract]
Size (Unaudited) (Square feet) | ft²		137,000
Development Costs Transferred	[1]	$ 1,273,000
Development costs incurred, for the period		1,631,000
Development		2,904,000
Estimated Total Cumulative Development Costs	[2]	$ 7,600,000
Conversion date (or anticipated conversion date, if property is in lease-up or under construction)		05/17
West Road IV [Member] | Lease Up [Member]
DEVELOPMENT [Abstract]
Size (Unaudited) (Square feet) | ft²		65,000
Development Costs Transferred	[1]	$ 1,292,000
Development costs incurred, for the period		3,393,000
Development		4,685,000
Estimated Total Cumulative Development Costs	[2]	$ 5,400,000
Conversion date (or anticipated conversion date, if property is in lease-up or under construction)		08/16
Kyrene 202 VI [Member] | Lease Up [Member]
DEVELOPMENT [Abstract]
Size (Unaudited) (Square feet) | ft²		123,000
Development Costs Transferred	[1]	$ 1,515,000
Development costs incurred, for the period		5,505,000
Development		7,020,000
Estimated Total Cumulative Development Costs	[2]	$ 9,500,000
Conversion date (or anticipated conversion date, if property is in lease-up or under construction)		09/16

[1] Represents costs transferred from Prospective Development (primarily land) to Under Construction during the period. Negative amounts represent land inventory costs transferred to Under Construction.

[2] Included in these costs are development obligations of $12.0 million and tenant improvement obligations of $4.3 million on properties under development.

[3] Represents cumulative costs at the date of transfer.

[4] This property is a manufacturing building undergoing redevelopment to a multi-tenant use building.