Real Estate Investments - Operator changes (Details)		1 Months Ended			3 Months Ended				6 Months Ended		9 Months Ended		12 Months Ended
	Oct. 04, 2019 USD ($)	Oct. 31, 2020 USD ($)	Sep. 30, 2020 USD ($) item property	Jul. 31, 2020 USD ($)	Sep. 30, 2020 USD ($) item property lease	Jun. 30, 2020 USD ($)	Mar. 31, 2020 USD ($) property item	Sep. 30, 2019 USD ($)	Sep. 30, 2020 USD ($) item property	Mar. 31, 2020 USD ($)	Sep. 30, 2020 USD ($) property item	Sep. 30, 2019 USD ($)	Dec. 31, 2020 USD ($)	Dec. 31, 2017 item	Dec. 31, 2019 USD ($)
Other disclosures
Rent deferral		$ 566,000	$ 1,176,000		$ 1,176,000				$ 1,176,000		$ 1,176,000
Impairment charges											941,000
Rental income					30,010,000			$ 38,665,000			88,320,000	$ 114,566,000
Proceeds from sale of real estate, net											72,141,000	8,068,000
Gain on sale of real estate, net					30,000			$ 6,236,000			$ 44,073,000	$ 6,736,000
Net book value															$ 26,856,000
Anthem Memory Care
Other disclosures
Number of properties in default | property											11
Anthem Memory Care | Forecast
Other disclosures
Minimum cash rent received													$ 9,900,000
Preferred Care, Inc.
Other disclosures
Number of properties under two master leases | item														24
Number of master leases | item														2
Number of properties sold | property							21
Number of beds or units in property sold | item							2,411
Proceeds from sale of real estate, net							$ 72,100,000			$ 77,900,000
Gain on sale of real estate, net							44,073,000			44,000,000
Net book value							$ 29,100,000			$ 29,100,000					$ 35,600,000
Senior Lifestyle Corporation
Other disclosures
Number of properties in default | property											23
Contractual rent		1,561,000							9,121,000
Remaining outstanding accounts receivable			2,670,000		2,670,000				2,670,000		$ 2,670,000
Rent receivable line of credit and security deposit as collateral			3,608,000		3,608,000				3,608,000		3,608,000
Write-off of rent receivable and lease incentives				$ 17,742,000
Rental income		$ 1,341,000							5,325,000
Veritas Senior Living, LLC
Other disclosures
Contractual rent			374,000		1,299,000
Write-off of rent receivable and lease incentives					$ 1,156,000
Number of master lease into combined one | lease					2
Abated cash rent					$ 570,000	$ 80,000			650,000
Rent deferral			$ 186,000		186,000				$ 186,000		$ 186,000
Impairment charges					941,000
Rental income					542,000
Genesis healthcare
Other disclosures
Write-off of rent receivable and lease incentives					$ 4,316,000
Brookdale Senior Living
Other disclosures
Number of leases consolidated | lease					4
Number of renewal option | item			3		3				3		3
Renewal term option one					4 years
Renewal term option two					5 years
Renewal term option three					10 years
Senior Care Centers
Other disclosures
Court ordered payment amount	$ 1,596,000
Real Estate Investment
Other disclosures
Number of properties | property			159		159				159		159
Real Estate Investment | Maximum
Other disclosures
Initial lease term			15 years		15 years				15 years		15 years