Property Expenses 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 expenses	$ 3,840	$ 3,637	$ 10,468	$ 9,445
Real estate taxes	1,317	1,200	3,777	3,592
Property expenses	5,157	4,837	14,245	13,037
Office real estate
Segment Reporting Information [Line Items]
Rental expenses	1,536	1,740	4,341	4,303
Real estate taxes	545	531	1,626	1,618
Retail real estate
Segment Reporting Information [Line Items]
Rental expenses	1,230	1,134	3,593	3,239
Real estate taxes	515	484	1,461	1,385
Multifamily residential real estate
Segment Reporting Information [Line Items]
Rental expenses	1,074	761	2,534	1,896
Real estate taxes	257	185	690	557
Other
Segment Reporting Information [Line Items]
Rental expenses		2		7
Real estate taxes				$ 32