Real Estate - Additional Information (Details) $ in Thousands, ft² in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020 USD ($) ft² property	Jun. 30, 2019 USD ($) ft² property	Jun. 30, 2020 USD ($) ft² property	Jun. 30, 2019 USD ($) ft² property	Dec. 31, 2019 ft² property
Subsidiary of Limited Liability Company or Limited Partnership [Line Items]
Depreciation | $	$ 4,355	$ 3,908	$ 8,672	$ 8,221
Amortization expense of in-place lease value intangible | $	2,665	2,726	5,330	5,443
Asset management fees paid to Advisor | $	$ 440	$ 880	$ 440	$ 880
Texas
Subsidiary of Limited Liability Company or Limited Partnership [Line Items]
Number of commercial properties	43	43	43	43	43
Area of real estate property (in sq ft) | ft²	6.7	6.7	6.7	6.7	6.7
Number of real estate properties	3	3	3	3	3
Richardson, Arlington And Dallas, Texas
Subsidiary of Limited Liability Company or Limited Partnership [Line Items]
Number of real estate properties	15	15	15	15
Houston, Texas
Subsidiary of Limited Liability Company or Limited Partnership [Line Items]
Number of real estate properties	25	25	25	25
San Antonio, Texas
Subsidiary of Limited Liability Company or Limited Partnership [Line Items]
Number of real estate properties	3	3	3	3