Segments - Net Income of Reportable Segments (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Segment Reporting Information
Rental revenues	$ 47,378	$ 39,915	$ 93,119	$ 82,204
Rental expenses	11,292	8,309	22,124	17,684
Real estate taxes	5,465	4,233	10,771	8,566
Segment revenues	18,408	57,398	53,971	104,666
Gross profit	30,898	29,429	61,789	59,728
Office real estate
Segment Reporting Information
Rental revenues	11,756	10,494	23,391	20,686
Rental expenses	2,938	2,291	5,813	4,837
Real estate taxes	1,413	1,228	2,771	2,374
Gross profit	7,405	6,975	14,807	13,475
Retail real estate
Segment Reporting Information
Rental revenues	19,204	18,714	37,459	39,125
Rental expenses	3,013	2,458	5,849	5,478
Real estate taxes	2,180	2,007	4,207	4,173
Gross profit	14,011	14,249	27,403	29,474
Multifamily residential real estate
Segment Reporting Information
Rental revenues	16,418	10,707	32,269	22,393
Rental expenses	5,341	3,560	10,462	7,369
Real estate taxes	1,872	998	3,793	2,019
Gross profit	9,205	6,149	18,014	13,005
General contracting and real estate services | General contracting and real estate services
Segment Reporting Information
Segment revenues	18,408	57,398	53,971	104,666
Segment expenses	18,131	55,342	52,406	100,892
Gross profit	$ 277	$ 2,056	$ 1,565	$ 3,774