Segment Reporting (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Schedule of segments operating activity
Segment profit	$ 19,120	$ 15,156	$ 53,703	$ 44,054
Total Retail [Member]
Schedule of segments operating activity
Property revenue	23,694	21,494	67,837	64,923
Property expense	(6,828)	(5,981)	(18,648)	(17,433)
Segment profit	16,866	15,513	49,189	47,490
Total Office [Member]
Schedule of segments operating activity
Property revenue	21,657	18,335	60,838	45,767
Property expense	(6,807)	(6,209)	(19,458)	(15,029)
Segment profit	14,850	12,126	41,380	30,738
Total Multifamily [Member]
Schedule of segments operating activity
Property revenue	3,906	3,803	10,957	10,588
Property expense	(1,558)	(1,387)	(4,437)	(3,974)
Segment profit	2,348	2,416	6,520	6,614
Total Mixed-Use [Member]
Schedule of segments operating activity
Property revenue	13,579	12,661	38,051	32,998
Property expense	(8,132)	(8,000)	(23,365)	(21,084)
Segment profit	$ 5,447	$ 4,661	$ 14,686	$ 11,914