Segments - Net Income of Reportable Segments (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Segment Reporting Information
Rental revenues	$ 25,305	$ 21,303	$ 72,839	$ 59,401
Rental expenses	5,834	4,865	16,234	14,256
Real estate taxes	2,356	2,056	7,087	5,672
Segment revenues	38,552	53,822	108,555	129,959
Segment expenses	37,274	51,716	104,336	125,141
Operating income	6,858	8,010	19,567	19,930
Operating Segments
Segment Reporting Information
Operating income	18,393	16,488	53,737	44,291
Office real estate | Operating Segments
Segment Reporting Information
Rental revenues	5,277	8,092	16,097	23,847
Rental expenses	1,553	1,758	4,307	5,216
Real estate taxes	485	734	1,550	2,228
Operating income	3,239	5,600	10,240	16,403
Retail real estate | Operating Segments
Segment Reporting Information
Rental revenues	14,340	8,523	41,485	22,715
Rental expenses	2,264	1,478	6,820	4,223
Real estate taxes	1,339	810	3,953	2,080
Operating income	10,737	6,235	30,712	16,412
Multifamily residential real estate | Operating Segments
Segment Reporting Information
Rental revenues	5,688	4,688	15,257	12,839
Rental expenses	2,017	1,629	5,107	4,817
Real estate taxes	532	512	1,584	1,364
Operating income	3,139	2,547	8,566	6,658
General contracting and real estate services | Operating Segments
Segment Reporting Information
Segment revenues	38,552	53,822	108,555	129,959
Segment expenses	37,274	51,716	104,336	125,141
Operating income	$ 1,278	$ 2,106	$ 4,219	$ 4,818