Segments - Property Expenses of Reportable Segments (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Segment Reporting Information [Line Items]
Rental expenses	$ 4,414	$ 3,840	$ 12,230	$ 10,468
Real estate taxes	1,480	1,317	4,231	3,777
Property expenses	5,894	5,157	16,461	14,245
Office Real Estate [Member]
Segment Reporting Information [Line Items]
Rental expenses	1,742	1,536	4,756	4,341
Real estate taxes	609	545	1,697	1,626
Property expenses	2,351	2,081	6,453	5,967
Retail Real Estate [Member]
Segment Reporting Information [Line Items]
Rental expenses	1,255	1,230	3,764	3,593
Real estate taxes	540	515	1,546	1,461
Property expenses	1,795	1,745	5,310	5,054
Multifamily Residential Real Estate [Member]
Segment Reporting Information [Line Items]
Rental expenses	1,417	1,074	3,710	2,534
Real estate taxes	331	257	988	690
Property expenses	$ 1,748	$ 1,331	$ 4,698	$ 3,224