SEGMENT REPORTING Net Real Estate and Secured Note Payable Balances (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013		Dec. 31, 2012
Segment Reporting Information [Line Items]
Net Real Estate	$ 1,665,789		$ 1,668,182
Secured Notes Payable	1,054,930	[1]	1,057,680	[1]
Unamortized fair value adjustment	10,813		12,998
Total Retail
Segment Reporting Information [Line Items]
Net Real Estate	655,569		669,177
Secured Notes Payable	395,677	[1]	397,732	[1]
Total Office
Segment Reporting Information [Line Items]
Net Real Estate	774,775		759,203
Secured Notes Payable	427,499	[1]	428,194	[1]
Total Multifamily
Segment Reporting Information [Line Items]
Net Real Estate	35,757		36,391
Secured Notes Payable	101,444	[1]	101,444	[1]
Total Mixed-Use
Segment Reporting Information [Line Items]
Net Real Estate	199,688		203,411
Secured Notes Payable	$ 130,310	[1]	$ 130,310	[1]

[1] Excludes unamortized fair market value adjustments of $10.8 million and $13.0 million as of September 30, 2013 and December 31, 2012, respectively.