Investment Activity - 2017 Mortgage Notes Receivable Funding - Additional Information (Details)	Oct. 10, 2017 USD ($)	Aug. 01, 2017 USD ($)	Jan. 30, 2017 USD ($) ft² Room	Dec. 31, 2018 USD ($)	Sep. 27, 2018 USD ($)	Sep. 21, 2018 USD ($)	Dec. 31, 2017 USD ($)
Investment Activity [Line Items]
Mortgage notes receivable, net			$ 12,500,000	$ 44,778,000			$ 18,557,000
Interest-only loan interest rate			9.60%
Area of hospital building | ft²			23,300
Number of operating rooms | Room			4
Number of special procedure rooms | Room			2
Number of inpatient rooms | Room			4
Number of full-size extended recovery rooms | Room			4
Norris Academy
Investment Activity [Line Items]
Mortgage notes receivable, net					$ 6,400,000
Tennessee | Norris Academy
Investment Activity [Line Items]
Mortgage notes receivable, net						$ 6,400,000
Maximum
Investment Activity [Line Items]
Mortgage notes receivable, net				$ 19,000,000
Medistar Corporation
Investment Activity [Line Items]
Mortgage notes receivable, net		$ 6,700,000
Interest-only loan interest rate		12.00%
Mortgage note, maturity date		Feb. 28, 2019
Sequel Youth and Family Services, LLC
Investment Activity [Line Items]
Interest-only loan interest rate	8.25%
Sequel Youth and Family Services, LLC | Tennessee | Norris Academy
Investment Activity [Line Items]
Mortgage notes receivable, net						$ 6,400,000
Sequel Youth and Family Services, LLC | Maximum
Investment Activity [Line Items]
Mortgage notes receivable, net	$ 6,000,000