Basis of Presentation - Summary of Gain on Sale for Each Land Parcel (Details) $ in Thousands					3 Months Ended		6 Months Ended
	Mar. 16, 2018 USD ($) a Parcel		Apr. 28, 2017 USD ($) a Parcel	Jan. 30, 2017 USD ($) a Parcel	Jun. 30, 2018 USD ($) a Parcel	Jun. 30, 2017 USD ($)	Jun. 30, 2018 USD ($) a Parcel	Jun. 30, 2017 USD ($)
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Proceeds from the sale of properties							$ 16,771	$ 102,083
Gain on Sale					$ 2,837	$ 0	$ 2,859	$ 0
Land [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Number of Parcels | Parcel					2		2
Acreage of land | a					19.7		19.7
Sales Price					$ 15,056		$ 15,056
Proceeds from the sale of properties							14,921
Gain on Sale							1,446
Garza Ranch - Office [Member] | Land [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Number of Parcels | Parcel	1
Acreage of land | a	6.6
Sales Price	$ 14,571
Proceeds from the sale of properties	14,509
Gain on Sale	$ 1,424	[1]					1,424
Garza Ranch - Multifamily [Member] | Land [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Number of Parcels | Parcel			1
Acreage of land | a			8.4
Sales Price			$ 11,800
Proceeds from the sale of properties			$ 11,560
Gain on Sale							1,233
Garza Ranch - Hotel [Member] | Land [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Number of Parcels | Parcel				1
Acreage of land | a				1.7
Sales Price				$ 3,500
Proceeds from the sale of properties				$ 3,277
Gain on Sale							$ 180
Garza Ranch [Member] | Land [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Number of Parcels | Parcel					3		3
Acreage of land | a					16.7		16.7
Sales Price					$ 29,871		$ 29,871
Proceeds from the sale of properties							29,346
Gain on Sale							$ 2,837

[1] As of March 31, 2018, the Company had not transferred control to the buyer of this land parcel, or two other parcels at this site which were sold during 2017, because of a completion guarantee which required the Company, as developer, to complete certain infrastructure improvements on behalf of the buyers of the land parcels. The cash received at settlement was recorded as “Deferred income, gains and rent” on the Company’s consolidated balance sheets. During the three months ended June 30, 2018, the infrastructure improvements were substantially completed, at which time the Company transferred control of the land parcels. As a result, the Company then recognized the sale of the land parcels. See Note 2, “Basis of Presentation,” for further discussion of the infrastructure improvements and related revenue recognition.