REAL ESTATE JOINT VENTURE AND DECONSOLIDATION OF MACARTHUR PARK (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012	Mar. 26, 2013 Macarthur Park Property - AmReit	Mar. 26, 2013 Macarthur Park Property - Goldman Sachs	Mar. 26, 2013 Macarthur Park Property
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Real estate investments at cost	$ 425,072	$ 387,525	$ 15,162	$ 35,379	$ 50,541
Less accumulated depreciation and amortization	(35,724)	(39,820)	(2,689)	(6,275)	(8,964)
Real estate investments at cost, net	389,348	347,705	12,473	29,104	41,577
Acquired lease intangibles, net	17,173	15,976	377	880	1,257
Tenant and accounts receivable, net			64	150	214
Loan costs and other assets	2,931	3,206	149	348	497
Notes payable	(200,271)	(218,579)	(1,977)	(4,613)	(6,590)
Accounts payable and other liabilities	(10,667)	(9,593)	(302)	(704)	(1,006)
Net assets and liabilities contributed			$ 10,784	$ 25,165	$ 35,949