Investment Activity - Schedule of Geographic Concentration of Properties (Details) $ in Thousands	6 Months Ended
Jun. 30, 2018 USD ($) Property	Jun. 30, 2017
Concentration Risk [Line Items]
Number of real estate properties \| Property	33
Gross Investment \| $	$ 587,857
Percentage of Total Real Estate Property Investments	100.00%
Geographic Concentration Risk \| Sales Revenue, Net
Concentration Risk [Line Items]
Percentage of Rental Income	100.00%	100.00%
Texas
Concentration Risk [Line Items]
Number of real estate properties \| Property	17
Gross Investment \| $	$ 300,259
Percentage of Total Real Estate Property Investments	51.20%
Texas \| Geographic Concentration Risk \| Sales Revenue, Net
Concentration Risk [Line Items]
Percentage of Rental Income	59.80%	62.40%
California
Concentration Risk [Line Items]
Number of real estate properties \| Property	7
Gross Investment \| $	$ 154,726
Percentage of Total Real Estate Property Investments	26.30%
California \| Geographic Concentration Risk \| Sales Revenue, Net
Concentration Risk [Line Items]
Percentage of Rental Income	21.50%	24.70%
Nevada
Concentration Risk [Line Items]
Number of real estate properties \| Property	4
Gross Investment \| $	$ 64,350
Percentage of Total Real Estate Property Investments	10.90%
Nevada \| Geographic Concentration Risk \| Sales Revenue, Net
Concentration Risk [Line Items]
Percentage of Rental Income	11.60%	9.40%
South Carolina
Concentration Risk [Line Items]
Number of real estate properties \| Property	1
Gross Investment \| $	$ 20,000
Percentage of Total Real Estate Property Investments	3.40%
South Carolina \| Geographic Concentration Risk \| Sales Revenue, Net
Concentration Risk [Line Items]
Percentage of Rental Income	3.10%	3.50%
Indiana
Concentration Risk [Line Items]
Number of real estate properties \| Property	3
Gross Investment \| $	$ 38,389
Percentage of Total Real Estate Property Investments	6.50%
Indiana \| Geographic Concentration Risk \| Sales Revenue, Net
Concentration Risk [Line Items]
Percentage of Rental Income	2.50%
Connecticut
Concentration Risk [Line Items]
Number of real estate properties \| Property	1
Gross Investment \| $	$ 10,133
Percentage of Total Real Estate Property Investments	1.70%
Connecticut \| Geographic Concentration Risk \| Sales Revenue, Net
Concentration Risk [Line Items]
Percentage of Rental Income	1.50%	0.00%

Percentage of real estate property investment.

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

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- Definition

For an entity that discloses a concentration risk in relation to quantitative amount, which serves as the "benchmark" (or denominator) in the equation, this concept represents the concentration percentage derived from the division.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 275
-SubTopic 10
-Section 50
-Paragraph 18
-URI http://asc.fasb.org/extlink&oid=99393423&loc=d3e6351-108592

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 20
-URI http://asc.fasb.org/extlink&oid=109250915&loc=d3e13531-108611

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 21
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=109250915&loc=d3e13537-108611

Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 275
-SubTopic 10
-Section 50
-Paragraph 20
-URI http://asc.fasb.org/extlink&oid=99393423&loc=d3e6404-108592

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- Definition

The number of real estate properties owned as of the balance sheet date.

+ References

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- Definition

Amount of real estate investment property which may include the following: (1) land available-for-sale; (2) land available-for-development; (3) investments in building and building improvements; (4) tenant allowances; (5) developments in-process; (6) rental properties; and (7) other real estate investments.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03.1(d))
-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

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