MORTGAGE NOTES PAYABLE AND UNSECURED TERM LOAN PAYABLE (Details) (USD $)	12 Months Ended
	Dec. 31, 2011 Percent	Dec. 31, 2010 Percent
Participating Mortgage Loans [Line Items]
Carrying Amount of Securing Real Estate	$ 606,366,000
Mortgage notes payable	628,170,000	644,424,000
Interest and related fees resulted in an effective interest rate (in hundredths)	1.65%	1.68%
Unsecured term loan	50,000,000	0
Fixed interest rate, unsecured term loan (in hundredths)	3.91%
Term period, unsecured term loan	seven-year
Payments of principal over the next five years [Abstract]
2012	68,673,000
2013	60,164,000
2014	96,993,000
2015	100,279,000
2016	90,626,000
Butterfield Trail, Glenmont I and II, Interstate I, II and III, Rojas, Stemmons Circle, Venture and West Loop I and II [Member]
Participating Mortgage Loans [Line Items]
Interest Rate (in hundredths)	7.25%
Monthly P and I Payment	325,263
Maturity Date	Repaid
Carrying Amount of Securing Real Estate	0
Mortgage notes payable	0	36,171,000
America Plaza, Central Green and World Houston 3-9 [Member]
Participating Mortgage Loans [Line Items]
Interest Rate (in hundredths)	7.92%
Monthly P and I Payment	191,519
Maturity Date	Repaid
Carrying Amount of Securing Real Estate	0
Mortgage notes payable	0	22,993,000
University Business Center (120 and 130 Cremona) [Member]
Participating Mortgage Loans [Line Items]
Interest Rate (in hundredths)	6.43%
Monthly P and I Payment	81,856
Maturity Date	05-15-12
Carrying Amount of Securing Real Estate	8,513,000
Mortgage notes payable	2,193,000	3,006,000
University Business Center (125 and 175 Cremona) [Member]
Participating Mortgage Loans [Line Items]
Interest Rate (in hundredths)	7.98%
Monthly P and I Payment	88,607
Maturity Date	06-01-12
Carrying Amount of Securing Real Estate	11,685,000
Mortgage notes payable	8,771,000	9,119,000
Oak Creek Distribution Center IV [Member]
Participating Mortgage Loans [Line Items]
Interest Rate (in hundredths)	5.68%
Monthly P and I Payment	31,253
Maturity Date	06-01-12
Carrying Amount of Securing Real Estate	6,022,000
Mortgage notes payable	3,506,000	3,676,000
Fifty First Avenue, Airport Distribution, Broadway I, III and IV, Chestnut, Interchange Business Park, Main Street, North Stemmons I land, Southpark, Southpointe, and World Houston 12 and 13 [Member]
Participating Mortgage Loans [Line Items]
Interest Rate (in hundredths)	6.86%
Monthly P and I Payment	279,149
Maturity Date	09-01-12
Carrying Amount of Securing Real Estate	36,204,000
Mortgage notes payable	32,204,000	33,304,000
Interstate Distribution Center - Jacksonville [Member]
Participating Mortgage Loans [Line Items]
Interest Rate (in hundredths)	5.64%
Monthly P and I Payment	31,645
Maturity Date	01-01-13
Carrying Amount of Securing Real Estate	6,115,000
Mortgage notes payable	4,234,000	4,367,000
Thirty Fifth Avenue, Beltway I, Broadway V, Lockwood, Northwest Point, Sunbelt, Techway Southwest I and World Houston 10, 11 and 14 [Member]
Participating Mortgage Loans [Line Items]
Interest Rate (in hundredths)	4.75%
Monthly P and I Payment	259,403
Maturity Date	09-05-13
Carrying Amount of Securing Real Estate	39,023,000
Mortgage notes payable	35,912,000	37,283,000
Airport Commerce Center I and II, Interchange Park, Ridge Creek Distribution Center, Southridge XII, Waterford Distribution Center and World Houston 24, 25 and 27 [Member]
Participating Mortgage Loans [Line Items]
Interest Rate (in hundredths)	5.75%
Monthly P and I Payment	414,229
Maturity Date	01-05-14
Carrying Amount of Securing Real Estate	66,489,000
Mortgage notes payable	54,001,000	55,810,000
Kyrene Distribution Center I [Member]
Participating Mortgage Loans [Line Items]
Interest Rate (in hundredths)	9.00%
Monthly P and I Payment	11,246
Maturity Date	07-01-14
Carrying Amount of Securing Real Estate	2,171,000
Mortgage notes payable	310,000	412,000
Americas Ten I, Kirby, Palm River North I, II and III, Shady Trail, Westlake I and II and World Houston 17 [Member]
Participating Mortgage Loans [Line Items]
Interest Rate (in hundredths)	5.68%
Monthly P and I Payment	175,479
Maturity Date	10-10-14
Carrying Amount of Securing Real Estate	25,367,000
Mortgage notes payable	27,996,000	28,496,000
Beltway II, III and IV, Commerce Park 1, Eastlake, Fairgrounds I-IV, Nations Ford I-IV, Techway Southwest III, Wetmore I-IV and World Houston 15 and 22 [Member]
Participating Mortgage Loans [Line Items]
Interest Rate (in hundredths)	5.50%
Monthly P and I Payment	536,552
Maturity Date	04-05-15
Carrying Amount of Securing Real Estate	68,917,000
Mortgage notes payable	67,188,000	69,844,000
Country Club I, Lake Pointe, Techway Southwest II and World Houston 19 and 20 [Member]
Participating Mortgage Loans [Line Items]
Interest Rate (in hundredths)	4.98%
Monthly P and I Payment	256,952
Maturity Date	12-05-15
Carrying Amount of Securing Real Estate	21,108,000
Mortgage notes payable	31,039,000	32,536,000
Huntwood and Wiegman Distribution Centers [Member]
Participating Mortgage Loans [Line Items]
Interest Rate (in hundredths)	5.68%
Monthly P and I Payment	265,275
Maturity Date	09-05-16
Carrying Amount of Securing Real Estate	21,950,000
Mortgage notes payable	31,748,000	33,087,000
Alamo Downs, Arion 1-15 and 17, Rampart I, II and III, Santan 10 and World Houston 16 [Member]
Participating Mortgage Loans [Line Items]
Interest Rate (in hundredths)	5.97%
Monthly P and I Payment	557,467
Maturity Date	11-05-16
Carrying Amount of Securing Real Estate	56,429,000
Mortgage notes payable	65,961,000	68,626,000
Arion 16, Broadway VI, Chino, East University I and II, Northpark I-IV, Santan 10 II, South 55th Avenue and World Houston 1 and 2, 21 and 23 [Member]
Participating Mortgage Loans [Line Items]
Interest Rate (in hundredths)	5.57%
Monthly P and I Payment	518,885
Maturity Date	09-05-17
Carrying Amount of Securing Real Estate	56,848,000
Mortgage notes payable	63,093,000	65,718,000
Dominguez, Industry I and III, Kingsview, Shaw, Walnut and Washington [Member]
Participating Mortgage Loans [Line Items]
Interest Rate (in hundredths)	7.50%
Monthly P and I Payment	539,747
Maturity Date	05-05-19
Carrying Amount of Securing Real Estate	49,588,000
Mortgage notes payable	62,875,000	64,567,000
Recourse liability	5,000,000
Blue Heron Distribution Center II [Member]
Participating Mortgage Loans [Line Items]
Interest Rate (in hundredths)	5.39%
Monthly P and I Payment	16,176
Maturity Date	02-29-20
Carrying Amount of Securing Real Estate	4,701,000
Mortgage notes payable	1,288,000	1,409,000
Fortieth Avenue, Beltway V, Centennial Park, Executive Airport, Ocean View, Techway Southwest IV, Wetmore V-VIII and World Houston 26, 28, 29 and 30 [Member]
Participating Mortgage Loans [Line Items]
Interest Rate (in hundredths)	4.39%
Monthly P and I Payment	463,778
Maturity Date	01-05-21
Carrying Amount of Securing Real Estate	77,986,000
Mortgage notes payable	71,837,000	74,000,000
America Plaza, Central Green, Glenmont I , II, Interstate I, II, III, Rojas, Stemmons Circle, Venture, West Loop I, II and World Houston 3 9 [Member]
Participating Mortgage Loans [Line Items]
Interest Rate (in hundredths)	4.75%
Monthly P and I Payment	420,045
Maturity Date	06-05-21
Carrying Amount of Securing Real Estate	47,250,000
Mortgage notes payable	$ 64,014,000	$ 0