Rental Revenues of Reportable Segments (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended				9 Months Ended
	Sep. 30, 2013		Sep. 30, 2012		Sep. 30, 2013		Sep. 30, 2012
Segment Reporting Information [Line Items]
Rental revenues	$ 14,899		$ 13,318		$ 42,528		$ 40,314
Office real estate
Segment Reporting Information [Line Items]
Minimum rents	6,059		5,972		18,264		17,919
Percentage rents					104	[1]	109	[1]
Other	304	[2]	222	[2]	901	[2]	1,125	[2]
Rental revenues	6,364		6,194		19,270		19,153
Retail real estate
Segment Reporting Information [Line Items]
Minimum rents	4,759		4,376		13,733		13,072
Percentage rents	35	[1]	40	[1]	88	[1]	96	[1]
Other	890	[2]	881	[2]	2,251	[2]	2,416	[2]
Rental revenues	5,683		5,297		16,071		15,584
Multifamily residential real estate
Segment Reporting Information [Line Items]
Minimum rents	2,370		1,621		6,060		4,814
Percentage rents	21	[1]	30	[1]	84	[1]	93	[1]
Other	461	[2]	176	[2]	1,043	[2]	670	[2]
Rental revenues	$ 2,852		$ 1,827		$ 7,187		$ 5,577

[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.