Investment Activity - Schedule of Geographic Concentration of Properties (Details) $ in Thousands	12 Months Ended
Dec. 31, 2018 USD ($) Property	Dec. 31, 2017 USD ($) Property
Concentration Risk [Line Items]
Number of real estate properties \| Property	34	32
Gross Investment \| $	$ 598,052	$ 563,728
Percentage of Total Real Estate Property Investments	100.00%	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	17
Gross Investment \| $	$ 300,259	$ 300,206
Percentage of Total Real Estate Property Investments	50.20%	53.30%
Texas \| Geographic Concentration Risk \| Sales Revenue, Net
Concentration Risk [Line Items]
Percentage of Rental Income	48.00%	60.50%
California
Concentration Risk [Line Items]
Number of real estate properties \| Property	7	7
Gross Investment \| $	$ 154,726	$ 154,726
Percentage of Total Real Estate Property Investments	25.90%	27.40%
California \| Geographic Concentration Risk \| Sales Revenue, Net
Concentration Risk [Line Items]
Percentage of Rental Income	26.50%	23.80%
Nevada
Concentration Risk [Line Items]
Number of real estate properties \| Property	4	4
Gross Investment \| $	$ 68,134	$ 63,624
Percentage of Total Real Estate Property Investments	11.40%	11.30%
Nevada \| Geographic Concentration Risk \| Sales Revenue, Net
Concentration Risk [Line Items]
Percentage of Rental Income	14.30%	10.50%
South Carolina
Concentration Risk [Line Items]
Number of real estate properties \| Property	1	1
Gross Investment \| $	$ 20,000	$ 20,000
Percentage of Total Real Estate Property Investments	3.30%	3.50%
South Carolina \| Geographic Concentration Risk \| Sales Revenue, Net
Concentration Risk [Line Items]
Percentage of Rental Income	3.70%	3.30%
Indiana
Concentration Risk [Line Items]
Number of real estate properties \| Property	3	2
Gross Investment \| $	$ 38,415	$ 15,039
Percentage of Total Real Estate Property Investments	6.40%	2.70%
Indiana \| Geographic Concentration Risk \| Sales Revenue, Net
Concentration Risk [Line Items]
Percentage of Rental Income	5.30%	1.10%
Connecticut
Concentration Risk [Line Items]
Number of real estate properties \| Property	1	1
Gross Investment \| $	$ 10,133	$ 10,133
Percentage of Total Real Estate Property Investments	1.70%	1.80%
Connecticut \| Geographic Concentration Risk \| Sales Revenue, Net
Concentration Risk [Line Items]
Percentage of Rental Income	1.90%	0.80%
Tennessee
Concentration Risk [Line Items]
Number of real estate properties \| Property	1
Gross Investment \| $	$ 6,385
Percentage of Total Real Estate Property Investments	1.10%
Tennessee \| Geographic Concentration Risk \| Sales Revenue, Net
Concentration Risk [Line Items]
Percentage of Rental Income	0.30%

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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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
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- Definition

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

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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
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