Rental Revenues of Reportable Segments (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended				6 Months Ended
	Jun. 30, 2013		Jun. 30, 2012		Jun. 30, 2013		Jun. 30, 2012
Segment Reporting Information [Line Items]
Rental revenues	$ 14,231		$ 13,609		$ 27,629		$ 26,996
Office real estate
Segment Reporting Information [Line Items]
Minimum rents	6,105		5,944		12,205		11,947
Percentage rents					104	[1]	109	[1]
Other	315	[2]	622	[2]	597	[2]	903	[2]
Rental revenues	6,420		6,566		12,906		12,959
Retail real estate
Segment Reporting Information [Line Items]
Minimum rents	4,609		4,366		8,974		8,696
Percentage rents	29	[1]	31	[1]	53	[1]	56	[1]
Other	745	[2]	790	[2]	1,361	[2]	1,535	[2]
Rental revenues	5,383		5,187		10,388		10,287
Multifamily residential real estate
Segment Reporting Information [Line Items]
Minimum rents	2,063		1,603		3,690		3,193
Percentage rents	21	[1]	25	[1]	63	[1]	63	[1]
Other	344	[2]	228	[2]	582	[2]	494	[2]
Rental revenues	$ 2,428		$ 1,856		$ 4,335		$ 3,750

[1] Percentage rents are based on tenants' sales.

[2] Other rental revenue includes cost reimbursements for real estate taxes, property insurance and common area maintenance as well as termination fees.