| Property Portfolio - (Details)$ in Thousands
 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 1 Months Ended | 3 Months Ended | 6 Months Ended | 12 Months Ended |  | 
| Apr. 27, 2020  USD ($) | Mar. 20, 2020  USD ($) | Mar. 04, 2020  USD ($) | Feb. 27, 2020  USD ($) | Feb. 13, 2020  USD ($) | Dec. 17, 2019  USD ($) | Nov. 15, 2019  USD ($) | Oct. 31, 2019  USD ($) | Oct. 25, 2019  USD ($) | Oct. 01, 2019  USD ($) | Sep. 26, 2019  USD ($) | Aug. 23, 2019  USD ($) | Aug. 14, 2019  USD ($) | Aug. 06, 2019  USD ($) | Aug. 05, 2019  USD ($) | Aug. 01, 2019  USD ($) | Jul. 12, 2019  USD ($) | Apr. 15, 2019  USD ($) | Mar. 19, 2019  USD ($) | Feb. 28, 2018  USD ($) | Jun. 30, 2020  USD ($) | Jun. 30, 2019  USD ($) | Jun. 30, 2020  USD ($)  property | Jun. 30, 2019  USD ($) | Dec. 31, 2019  USD ($)  property | Feb. 28, 2019 | 
| Property, Plant and Equipment [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 
| Number of Properties Acquired | property |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 5 |  | 18 |  | 
| Depreciation, Total |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 6,593 | $ 4,608 | $ 12,429 | $ 8,475 |  |  | 
| Tenant Improvement Allowances Receivable |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 19,400 |  | 19,400 |  |  |  | 
| Capital Lease Obligations, Noncurrent |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 7,300 |  | 7,300 |  |  |  | 
| Property, Plant and Equipment, Additions |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 91,347 |  | $ 257,979 |  | 
| Debt Instrument, Term |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 3 years 3 months 7 days |  | 3 years 9 months 3 days |  | 
| Operating Lease, Weighted Average Remaining Lease Term |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 24 years |  | 24 years |  |  |  | 
| Commercial mortgage-backed securities (CMBS) |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 
| Property, Plant and Equipment [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 
| Debt Instrument, Face Amount | $ 12,100 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 
| Debt Instrument, Interest Rate, Stated Percentage | 4.68% |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 
| Debt Instrument, Term | 4 years |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 
| Revolving Credit Facility [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 
| Property, Plant and Equipment [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 
| Debt Instrument, Face Amount |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 500,000 |  | $ 500,000 |  |  |  | 
| Lease Intangibles Asset [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 
| Property, Plant and Equipment [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 
| Finite-Lived Intangible Asset, Useful Life |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 5 years 8 months 15 days |  |  |  | 
| Lease Intangibles Liability [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 
| Property, Plant and Equipment [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 
| Finite-Lived Intangible Asset, Useful Life |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 4 years 9 months 7 days |  |  |  | 
| Zachary Facility [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 
| Property, Plant and Equipment [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 
| Property, Plant and Equipment, Additions |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 4,600 |  |  |  |  |  |  | 
| Lessor, Operating Lease, Term of Contract |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 46 years | 
| Gilbert And Chandler Facility [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 
| Property, Plant and Equipment [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 
| Property, Plant and Equipment, Additions |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 16,300 |  |  |  |  |  |  |  | 
| Dobson Facility [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 
| Property, Plant and Equipment [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 
| Lessor, Operating Lease, Term of Contract |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 10 years 6 months |  |  |  |  |  |  |  | 
| IRF Portfolio [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 
| Property, Plant and Equipment [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 
| Property, Plant and Equipment, Additions |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 94,600 |  |  |  |  |  |  |  |  | 
| Operating Lease, Weighted Average Remaining Lease Term |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 8 years 3 months 18 days |  |  |  |  |  |  |  |  | 
| San Marcos [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 
| Property, Plant and Equipment [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 
| Property, Plant and Equipment, Additions |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 12,000 |  |  |  |  |  |  |  | $ 11,974 |  | 
| Operating Lease, Weighted Average Remaining Lease Term |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 8 years |  |  |  |  |  |  |  |  |  | 
| Lansing [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 
| Property, Plant and Equipment [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 
| Property, Plant and Equipment, Additions |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 11,100 |  |  |  |  |  |  |  |  | 11,368 |  | 
| Operating Lease, Weighted Average Remaining Lease Term |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 8 years 6 months |  |  |  |  |  |  |  |  |  |  | 
| Bannockburn [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 
| Property, Plant and Equipment [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 
| Property, Plant and Equipment, Additions |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 6,800 |  |  |  |  |  |  |  |  |  | 6,977 |  | 
| Operating Lease, Weighted Average Remaining Lease Term |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 6 years 3 months 18 days |  |  |  |  |  |  |  |  |  |  |  | 
| Aurora [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 
| Property, Plant and Equipment [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 
| Property, Plant and Equipment, Additions |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 12,600 |  |  |  |  |  |  |  |  |  |  | 12,557 |  | 
| Operating Lease, Weighted Average Remaining Lease Term |  |  |  |  |  |  |  |  |  |  |  |  |  | 6 years |  |  |  |  |  |  |  |  |  |  |  |  | 
| Livonia [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 
| Property, Plant and Equipment [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 
| Property, Plant and Equipment, Additions |  |  |  |  |  |  |  |  |  |  |  |  | $ 10,400 |  |  |  |  |  |  |  |  |  |  |  | 10,592 |  | 
| Operating Lease, Weighted Average Remaining Lease Term |  |  |  |  |  |  |  |  |  |  |  |  | 3 years 2 months 12 days |  |  |  |  |  |  |  |  |  |  |  |  |  | 
| Gilbert [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 
| Property, Plant and Equipment [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 
| Property, Plant and Equipment, Additions |  |  |  |  |  |  |  |  |  |  |  | $ 5,600 |  |  |  |  |  |  |  |  |  |  |  |  | 5,592 |  | 
| Operating Lease, Weighted Average Remaining Lease Term |  |  |  |  |  |  |  |  |  |  |  | 10 years |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 
| Morgantown [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 
| Property, Plant and Equipment [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 
| Property, Plant and Equipment, Additions |  |  |  |  |  |  |  |  |  |  | $ 8,000 |  |  |  |  |  |  |  |  |  |  |  |  |  | 7,950 |  | 
| Operating Lease, Weighted Average Remaining Lease Term |  |  |  |  |  |  |  |  |  |  | 10 years |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 
| Beaumont [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 
| Property, Plant and Equipment [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 
| Property, Plant and Equipment, Additions |  |  |  |  |  |  |  |  |  | $ 33,700 |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 33,739 |  | 
| Finite-Lived Intangible Asset, Useful Life |  |  |  |  |  |  |  |  |  | 10 years |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 
| Bastrop [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 
| Property, Plant and Equipment [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 
| Property, Plant and Equipment, Additions |  |  |  |  |  |  |  |  | $ 12,100 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 12,065 |  | 
| Finite-Lived Intangible Asset, Useful Life |  |  |  |  |  |  |  |  | 5 years |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 
| Panama City [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 
| Property, Plant and Equipment [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 
| Property, Plant and Equipment, Additions |  |  |  |  |  |  |  | $ 13,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 12,976 |  | 
| Finite-Lived Intangible Asset, Useful Life |  |  |  |  |  |  |  | 15 years |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 
| Jacksonville [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 
| Property, Plant and Equipment [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 
| Property, Plant and Equipment, Additions |  |  |  |  |  |  | $ 8,900 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 8,869 |  | 
| Finite-Lived Intangible Asset, Useful Life |  |  |  |  |  |  | 15 years |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 
| Greenwood [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 
| Property, Plant and Equipment [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 
| Property, Plant and Equipment, Additions |  |  |  |  |  | $ 5,800 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 5,848 |  | 
| Finite-Lived Intangible Asset, Useful Life |  |  |  |  |  | 13 years |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 
| LTAC Hospital [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 
| Property, Plant and Equipment [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 
| Lessor, Operating Lease, Term of Contract |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 16 years | 
| High Point Facility [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 
| Property, Plant and Equipment [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 
| Property, Plant and Equipment, Additions |  |  |  |  | $ 25,100 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 25,081 |  |  |  | 
| Lessor, Operating Lease, Term of Contract |  |  |  |  | 3 years |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 
| Clinton Facility [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 
| Property, Plant and Equipment [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 
| Property, Plant and Equipment, Additions |  |  |  | $ 11,600 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 11,619 |  |  |  | 
| Lessor, Operating Lease, Term of Contract |  |  |  | 4 years |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 
| West Allis Facility [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 
| Property, Plant and Equipment [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 
| Property, Plant and Equipment, Additions |  |  | $ 9,100 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 9,357 |  |  |  | 
| Lessor, Operating Lease, Term of Contract |  |  | 4 years |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 
| Grand Rapids Facility [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 
| Property, Plant and Equipment [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 
| Property, Plant and Equipment, Additions |  | $ 22,700 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 22,790 |  |  |  | 
| Lessor, Operating Lease, Term of Contract |  | 5 years |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 
| Dumfries Facility [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 
| Property, Plant and Equipment [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 
| Property, Plant and Equipment, Additions | $ 19,600 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |