| Property Portfolio (Tables)
 | 6 Months Ended | 
| Jun. 30, 2020 | 
|---|
| Schedule of Properties Acquired | A rollforward of the gross investment in land, building, improvements, and acquired lease intangible assets as of June 30, 2020 resulting from these acquisitions is as follows:  
|  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  
|  |      |  |  |      |  |  |  | Site |      | Tenant |      | Acquired Lease |      | Gross Investment in |  
|  |  | Land |  | Building |  | Improvements |  | Improvements |  | Intangible Assets |  | Real Estate |  
| Balances as of December 31, 2019 |  | $ |  95,381 |  | $ |  693,533 |  | $ |  9,912 |  | $ |  33,909 |  | $ |  72,794 |  | $ |  905,529 |  
| Facility Acquired – Date Acquired: |  |   |    |  |   |    |  |   |    |  |   |    |  |   |    |  |   |    |  
| High Point – 2/13/20 |  |   |  1,749 |  |   |  20,367 |  |   |  440 |  |   |  869 |  |   |  1,656 |  |   |  25,081 |  
| Clinton – 2/27/20 |  |   |  664 |  |   |  6,551 |  |   |  342 |  |   |  1,578 |  |   |  2,484 |  |   |  11,619 |  
| West Allis – 3/4/20 |  |   |  974 |  |   |  7,687 |  |   |  137 |  |   |  98 |  |   |  461 |  |   |  9,357 |  
| Grand Rapids – 3/20/20 |  |   |  2,947 |  |   |  17,341 |  |   |  470 |  |   |  450 |  |   |  1,582 |  |   |  22,790 |  
| Dumfries– 4/27/20 |  |  |  2,597 |  |  |  10,047 |  |  |  289 |  |  |  4,815 |  |  |  4,292 |  |  |  22,040 |  
| Capitalized costs(1) |  |  |  4 |  |  |  281 |  |  |  3 |  |  |  172 |  |  |  — |  |  |  460 |  
| Total Additions: |  |   |  8,935 |  |   |  62,274 |  |   |  1,681 |  |   |  7,982 |  |   |  10,475 |  |   |  91,347 |  
| Balances as of June 30, 2020 |  | $ |  104,316 |  | $ |  755,807 |  | $ |  11,593 |  | $ |  41,891 |  | $ |  83,269 |  | $ |  996,876 |  
| (1) | Represents capital projects that were completed and placed in service during the six months ended June 30, 2020 related to the Company’s existing facilities. | 
 A rollforward of the gross investment in land, building, improvements, and acquired lease intangible assets as of December 31, 2019 resulting from these acquisitions is as follows:  
|  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  
|  |      |  |  |      |  |  |      | Site  |  | Tenant |  | Acquired Lease |      | Gross Investment in  |  
|  |  | Land |  | Building |  | Improvements |  | Improvements |  | Intangible Assets |  | Real Estate |  
| Balances as of December 31, 2018 |  | $ |  63,710 |  | $ |  518,451 |  | $ |  6,880 |  | $ |  15,357 |  | $ |  43,152 |  | $ |  647,550 |  
| Facility Acquired – Date Acquired: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  
| Zachary – 2/28/19 |  |   |  — |  |   |  3,336 |  |   |  103 |  |  |  409 |  |   |  835 |  |   |  4,683 |  
| Gilbert and Chandler – 3/19/19 |  |   |  4,616 |  |   |  11,643 |  |   |  — |  |  |  — |  |   |  — |  |   |  16,259 |  
| Las Vegas – 4/15/19 |  |  |  2,479 |  |  |  15,277 |  |  |  244 |  |  |  2,205 |  |  |  2,297 |  |  |  22,502 |  
| Oklahoma Northwest – 4/15/19 |  |  |  2,364 |  |  |  19,501 |  |  |  143 |  |  |  3,044 |  |  |  3,155 |  |  |  28,207 |  
| Mishawaka – 4/15/19 |  |  |  1,924 |  |  |  10,084 |  |  |  74 |  |  |  1,798 |  |  |  2,223 |  |  |  16,103 |  
| Surprise – 4/15/19 |  |  |  1,738 |  |  |  18,737 |  |  |  228 |  |  |  4,119 |  |  |  3,860 |  |  |  28,682 |  
|    San Marcos – 7/12/19 |  |  |  2,322 |  |  |  6,934 |  |  |  126 |  |  |  404 |  |  |  2,188 |  |  |  11,974 |  
|    Lansing – 8/1/19 |  |  |  1,202 |  |  |  7,681 |  |  |  185 |  |  |  667 |  |  |  1,633 |  |  |  11,368 |  
|    Bannockburn – 8/5/19 |  |  |  763 |  |  |  3,566 |  |  |  132 |  |  |  1,134 |  |  |  1,382 |  |  |  6,977 |  
|    Aurora – 8/6/19 |  |  |  1,521 |  |  |  7,446 |  |  |  308 |  |  |  603 |  |  |  2,679 |  |  |  12,557 |  
|    Livonia – 8/14/19 |  |  |  980 |  |  |  7,629 |  |  |  201 |  |  |  442 |  |  |  1,340 |  |  |  10,592 |  
|    Gilbert – 8/23/19 |  |  |  2,408 |  |  |  2,027 |  |  |  62 |  |  |  362 |  |  |  733 |  |  |  5,592 |  
|    Morgantown – 9/26/19 |  |  |  883 |  |  |  5,286 |  |  |  373 |  |  |  506 |  |  |  902 |  |  |  7,950 |  
|    Beaumont – 10/1/19 |  |  |  3,022 |  |  |  24,836 |  |  |  399 |  |  |  1,036 |  |  |  4,446 |  |  |  33,739 |  
|    Bastrop – 10/25/19 |  |  |  1,975 |  |  |  8,436 |  |  |  64 |  |  |  276 |  |  |  1,314 |  |  |  12,065 |  
|    Panama City – 10/31/19 |  |  |  1,559 |  |  |  8,682 |  |  |  220 |  |  |  1,036 |  |  |  1,479 |  |  |  12,976 |  
|    Jacksonville – 11/15/19 |  |  |  1,023 |  |  |  7,846 |  |  |  — |  |  |  — |  |  |  — |  |  |  8,869 |  
|    Greenwood – 12/17/19 |  |  |  892 |  |  |  4,956 |  |  |  — |  |  |  — |  |  |  — |  |  |  5,848 |  
| ASC Topic 842 Reclassification |  |  |  — |  |  |  — |  |  |  — |  |  |  — |  |  |  (824) |  |  |  (824) |  
| Capitalized costs(1) |  |  |  — |  |  |  1,179 |  |  |  170 |  |  |  511 |  |  |  — |  |  |  1,860 |  
| Total Additions: |  |   |  31,671 |  |   |  175,082 |  |   |  3,032 |  |  |  18,552 |  |  |  29,642 |  |   |  257,979 |  
| Balances as of December 31, 2019 |  | $ |  95,381 |  | $ |  693,533 |  | $ |  9,912 |  | $ |  33,909 |  | $ |  72,794 |  | $ |  905,529 |  
| (1) | Represents capital projects that were completed and placed in service during the year ended December 31, 2019 related to the Company’s existing facilities. | 
 | 
| Summary of Carrying amount of intangible assets and liabilities | The following is a summary of the carrying amount of intangible assets and liabilities as of the dates presented:  
|  |  |  |  |  |  |  |  |  |  |  
|  |  | As of June 30, 2020 |  
|  |  |  |  |  | Accumulated |  |  |  |  
|  |      | Cost |      | Amortization |      | Net |  
| Assets |  |  |  |  |  |  |  |  |  |  
| In-place leases |  | $ |  47,031 |  | $ |  (10,847) |  | $ |  36,184 |  
| Above market leases |  |   |  12,932 |  |   |  (3,144) |  |   |  9,788 |  
| Leasing costs |  |   |  23,306 |  |   |  (4,731) |  |   |  18,575 |  
|  |  | $ |  83,269 |  | $ |  (18,722) |  | $ |  64,547 |  
| Liability |  |  |  |  |  |  |  |  |  |  
| Below market leases |  | $ |  6,670 |  | $ |  (1,072) |  | $ |  5,598 |   
|  |  |  |  |  |  |  |  |  |  |  
|  |  | As of December 31, 2019 |  
|  |      |  |  |      | Accumulated |      |  |  |  
|  |  | Cost |  | Amortization |  | Net |  
| Assets |   |  |    |   |  |    |   |  |    |  
| In-place leases |  | $ |  39,429 |  | $ |  (7,851) |  | $ |  31,578 |  
| Above market leases |  |   |  12,246 |  |   |  (2,366) |  |   |  9,880 |  
| Leasing costs |  |   |  21,119 |  |   |  (3,458) |  |   |  17,661 |  
|  |  | $ |  72,794 |  | $ |  (13,675) |  | $ |  59,119 |  
| Liability |  |   |  |  |   |  |  |   |  |  
| Below market leases |  | $ |  3,861 |  | $ |  (697) |  | $ |  3,164 |  | 
| Summary of the acquired lease intangible amortization |  
|  |  |  |  |  |  |  |  |  |  |  |  |  |  
|  |  | Three Months Ended  |  | Six Months Ended  |  
|  |  | June 30,  |  | June 30,  |  
|  |      | 2020 |      | 2019 |      | 2020 |      | 2019 |  
| Amortization expense related to in-place leases |  | $ |  1,663 |  | $ |  852 |  | $ |  2,996 |  | $ |  1,529 |  
| Amortization expense related to leasing costs |  | $ |  685 |  | $ |  403 |  | $ |  1,273 |  | $ |  728 |  
| Decrease in rental revenue related to above market leases |  | $ |  403 |  | $ |  279 |  | $ |  778 |  | $ |  552 |  
| Increase in rental revenue related to below market leases |  | $ |  247 |  | $ |  89 |  | $ |  375 |  | $ |  147 |  | 
| Schedule of net amortization acquired lease intangible assets and liabilities | As of June 30, 2020, scheduled future aggregate net amortization of the acquired lease intangible assets and liabilities for each year ended December 31 is listed below:  
|  |  |  |  |  |  |  |  
|  |      | Net Decrease |      | Net Increase |  
|  |  | in Revenue |  | in Expenses |  
| 2020 (six months remaining) |  | $ |  (220) |  | $ |  4,848 |  
| 2021 |  |   |  (444) |  |   |  9,077 |  
| 2022 |  |   |  (462) |  |   |  8,654 |  
| 2023 |  |   |  (496) |  |   |  7,740 |  
| 2024 |  |   |  (302) |  |   |  6,444 |  
| Thereafter |  |   |  (2,266) |  |   |  17,996 |  
| Total |  | $ |  (4,190) |  | $ |  54,759 |  | 
| High Point Facility [Member] |  | 
| Schedule of tangible and intangible assets |  
|  |  |  |  |  
| Land and site improvements |      | $ |  2,189 |  
| Building and tenant improvements |  |   |  21,236 |  
| In-place leases |  |   |  1,207 |  
| Leasing costs |  |   |  449 |  
| Total purchase price |  | $ |  25,081 |  | 
| Clinton Facility [Member] |  | 
| Schedule of tangible and intangible assets |  
|  |  |  |  |  
| Land and site improvements |      | $ |  1,006 |  
| Building and tenant improvements |  |   |  8,129 |  
| In-place leases |  |   |  2,115 |  
| Leasing costs |  |   |  369 |  
| Total purchase price |  | $ |  11,619 |  | 
| West Allis Facility [Member] |  | 
| Schedule of tangible and intangible assets |  
|  |  |  |  |  
| Land and site improvements |      | $ |  1,111 |  
| Building and tenant improvements |  |   |  7,785 |  
| In-place leases |  |   |  263 |  
| Leasing costs |  |   |  198 |  
| Below-market lease intangibles |  |   |  (264) |  
| Total purchase price |  | $ |  9,093 |  | 
| Grand Rapids Facility [Member] |  | 
| Schedule of tangible and intangible assets |  
|  |  |  |  |  
| Land and site improvements |      | $ |  3,417 |  
| Building and tenant improvements |  |   |  17,791 |  
| In-place leases |  |   |  761 |  
| Above-market lease intangibles |  |   |  685 |  
| Leasing costs |  |   |  136 |  
| Below-market lease intangibles |  |   |  (125) |  
| Total purchase price |  | $ |  22,665 |  | 
| Dumfries Facility [Member] |  | 
| Schedule of tangible and intangible assets |  
|  |  |  |  |  
| Land and site improvements |      | $ |  2,886 |  
| Building and tenant improvements |   |  |  14,862 |  
| In-place leases |   |  |  3,255 |  
| Leasing costs |   |  |  1,037 |  
| Below-market lease intangibles |   |  |  (2,419) |  
|    Total purchase price |  | $ |  19,621 |  | 
| Zachary Facility [Member] |  | 
| Schedule of tangible and intangible assets |  
|  |  |  |  |  
| Land and site improvements |      | $ |  103 |  
| Building and tenant improvements |  |  |  3,745 |  
| In-place leases |  |  |  305 |  
| Above-market lease intangibles |  |  |  117 |  
| Leasing costs |  |  |  413 |  
| Below-market lease intangibles |  |  |  (34) |  
| Total purchase price |  | $ |  4,649 |  | 
| IRF Portfolio [Member] |  | 
| Schedule of tangible and intangible assets |  
|  |  |  |  |  |  |  |  |  |  |  |  |  |  
|  |      |  |  |      |  |  |      | Oklahoma |      |  |  |  
|  |  | Las Vegas |  | Surprise |  | City |  | Mishawaka |  
| Land and site improvements |  | $ |  2,723 |  | $ |  1,966 |  | $ |  2,507 |  | $ |  1,998 |  
| Building and tenant improvements |  |   |  17,482 |  |   |  22,856 |  |   |  22,545 |  |   |  11,882 |  
| In-place leases |  |   |  1,778 |  |   |  1,845 |  |   |  1,890 |  |   |  1,465 |  
| Above-market lease intangibles |  |   |  — |  |   |  938 |  |   |  367 |  |   |  236 |  
| Leasing costs |  |   |  519 |  |   |  1,077 |  |   |  898 |  |   |  522 |  
| Below-market lease intangibles |  |   |  (863) |  |   |  — |  |   |  — |  |   |  — |  
| Total purchase price |  | $ |  21,639 |  | $ |  28,682 |  | $ |  28,207 |  | $ |  16,103 |  | 
| San Marcos [Member] |  | 
| Schedule of tangible and intangible assets |  
|  |  |  |  |  
| Land and site improvements |      | $ |  2,448 |  
| Building and tenant improvements |  |   |  7,338 |  
| In-place leases |  |   |  698 |  
| Above-market lease intangibles |  |   |  1,101 |  
| Leasing costs |  |   |  389 |  
| Total purchase price |  | $ |  11,974 |  | 
| Lansing [Member] |  | 
| Schedule of tangible and intangible assets |  
|  |  |  |  |  
| Land and site improvements |      | $ |  1,387 |  
| Building and tenant improvements |  |   |  8,348 |  
| In-place leases |  |   |  953 |  
| Above-market lease intangibles |  |   |  130 |  
| Leasing costs |  |   |  550 |  
| Below-market lease intangibles |  |   |  (248) |  
| Total purchase price |  | $ |  11,120 |  | 
| Bannockburn [Member] |  | 
| Schedule of tangible and intangible assets |  
|  |  |  |  |  
| Land and site improvements |      | $ |  895 |  
| Building and tenant improvements |  |   |  4,700 |  
| In-place leases |  |   |  796 |  
| Above-market lease intangibles |  |   |  250 |  
| Leasing costs |  |   |  336 |  
| Below-market lease intangibles |  |   |  (144) |  
| Total purchase price |  | $ |  6,833 |  | 
| Aurora [Member] |  | 
| Schedule of tangible and intangible assets |  
|  |  |  |  |  
| Land and site improvements |      | $ |  1,829 |  
| Building and tenant improvements |  |   |  8,049 |  
| In-place leases |  |   |  1,417 |  
| Above-market lease intangibles |  |   |  861 |  
| Leasing costs |  |   |  401 |  
| Total purchase price |  | $ |  12,557 |  | 
| Livonia [Member] |  | 
| Schedule of tangible and intangible assets |  
|  |  |  |  |  
| Land and site improvements |      | $ |  1,181 |  
| Building and tenant improvements |  |   |  8,071 |  
| In-place leases |  |   |  1,252 |  
| Above-market lease intangibles |  |   |  53 |  
| Leasing costs |  |   |  35 |  
| Below-market lease intangibles |  |   |  (236) |  
| Total purchase price |  | $ |  10,356 |  | 
| Gilbert [Member] |  | 
| Schedule of tangible and intangible assets |  
|  |  |  |  |  
| Land and site improvements |      | $ |  2,470 |  
| Building and tenant improvements |  |   |  2,389 |  
| In-place leases |  |   |  121 |  
| Above-market lease intangibles |  |   |  300 |  
| Leasing costs |  |   |  312 |  
| Total purchase price |  | $ |  5,592 |  | 
| Morgantown [Member] |  | 
| Schedule of tangible and intangible assets |  
|  |  |  |  |  
| Land and site improvements |      | $ |  1,256 |  
| Building and tenant improvements |  |   |  5,792 |  
| In-place leases |  |   |  457 |  
| Leasing costs |  |   |  445 |  
| Total purchase price |  | $ |  7,950 |  | 
| Beaumont [Member] |  | 
| Schedule of tangible and intangible assets |  
|  |  |  |  |  
| Land and site improvements |      | $ |  3,421 |  
| Building and tenant improvements |  |  |  25,872 |  
| In-place leases |  |  |  3,304 |  
| Leasing costs |  |  |  1,142 |  
|    Total purchase price |  | $ |  33,739 |  | 
| Bastrop [Member] |  | 
| Schedule of tangible and intangible assets |  
|  |  |  |  |  
| Land and site improvements |      | $ |  2,039 |  
| Building and tenant improvements |  |  |  8,712 |  
| In-place leases |  |  |  990 |  
| Leasing costs |  |  |  324 |  
|    Total purchase price |  | $ |  12,065 |   | 
| Panama City [Member] |  | 
| Schedule of tangible and intangible assets |  
|  |  |  |  |  
| Land and site improvements |      | $ |  1,779 |  
| Building and tenant improvements |  |   |  9,718 |  
| In-place leases |  |   |  405 |  
| Leasing costs |  |   |  1,074 |  
|    Total purchase price |  | $ |  12,976 |  | 
| Jacksonville [Member] |  | 
| Schedule of tangible and intangible assets |  
|  |  |  |  |  
| Land and site improvements |      | $ |  1,023 |  
| Building and tenant improvements |  |  |  7,846 |  
|    Total purchase price |  | $ |  8,869 |  | 
| Greenwood [Member] |  | 
| Schedule of tangible and intangible assets |  
|  |  |  |  |  
| Land and site improvements |      | $ |  892 |  
| Building and tenant improvements |  |  |  4,956 |  
|    Total purchase price |  | $ |  5,848 |   |