Property Expenses 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 expenses	$ 3,399	$ 2,944	$ 6,628	$ 5,808
Real estate taxes	1,248	1,209	2,460	2,392
Property expenses	4,647	4,153	9,088	8,200
Office real estate
Segment Reporting Information [Line Items]
Rental expenses	1,400	1,261	2,805	2,563
Real estate taxes	540	543	1,081	1,087
Retail real estate
Segment Reporting Information [Line Items]
Rental expenses	1,143	1,029	2,363	2,105
Real estate taxes	486	448	946	901
Multifamily residential real estate
Segment Reporting Information [Line Items]
Rental expenses	856	653	1,460	1,135
Real estate taxes	222	186	433	372
Other
Segment Reporting Information [Line Items]
Rental expenses		1		5
Real estate taxes		$ 32		$ 32