Segments - Net Income of Reportable Segments (Details) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2019	Mar. 31, 2018
Segment Reporting Information
Rental revenues	$ 30,909	$ 28,699
Rental expenses	6,725	6,424
Real estate taxes	3,128	2,813
General contracting and real estate services
Segment Reporting Information
Segment revenues	17,036	23,050
Segment expenses	16,286	22,414
Operating Segments
Segment Reporting Information
Gross profit	21,806	20,098
Operating Segments \| Office real estate
Segment Reporting Information
Rental revenues	5,556	5,100
Rental expenses	1,486	1,446
Real estate taxes	526	502
Gross profit	3,544	3,152
Operating Segments \| Retail real estate
Segment Reporting Information
Rental revenues	17,257	16,711
Rental expenses	2,600	2,657
Real estate taxes	1,811	1,683
Gross profit	12,846	12,371
Operating Segments \| Multifamily residential real estate
Segment Reporting Information
Rental revenues	8,096	6,888
Rental expenses	2,639	2,321
Real estate taxes	791	628
Gross profit	4,666	3,939
Operating Segments \| General contracting and real estate services \| General contracting and real estate services
Segment Reporting Information
Segment revenues	17,036	23,050
Segment expenses	16,286	22,414
Gross profit	$ 750	$ 636

The aggregate costs related to goods produced and sold and services rendered by an entity during the reporting period. This excludes costs incurred during the reporting period related to financial services rendered and other revenue generating activities.

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Amount of expense incurred and directly related to generating revenue from leased and rented property or equipment.

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Aggregate revenue less cost of goods and services sold or operating expenses directly attributable to the revenue generation activity.

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The total amount of revenue recognized for the period from operating leases, including minimum lease revenue, contingent revenue, percentage revenue and sublease revenue.

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A tax based on the assessed value of real estate by the local government. The tax is usually based on the value of property (including the land).

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