Investments in Unconsolidated Ventures - Changes in Carrying Value (Details)	1 Months Ended		3 Months Ended			9 Months Ended
	Mar. 31, 2019 USD ($) facility	Oct. 31, 2018 USD ($)	Sep. 30, 2020 USD ($)	Jun. 30, 2020 USD ($)	Sep. 30, 2019 USD ($)	Sep. 30, 2020 USD ($)	Sep. 30, 2019 USD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Oct. 30, 2018
Schedule of Equity Method Investments [Line Items]
Carrying Value			$ 230,257,000			$ 230,257,000		$ 268,894,000
Number of properties sold | facility	11
Proceeds from sale of held-for-sale property	$ 118,000,000.0
Proceeds from sale of held-for-sale property, net	$ 4,300,000
Equity in earnings (losses) of unconsolidated ventures			(1,043,000)		$ (3,037,000)	(36,799,000)	$ (7,666,000)
Select Revenues and (Expenses), net			(8,602,000)		(11,534,000)	(67,770,000)	(34,027,000)
Cash Distributions			198,000		4,767,000	1,963,000	16,846,000
Federal COVID-19 provider relief funds received			$ 600,000	$ 800,000		1,400,000
Trilogy
Schedule of Equity Method Investments [Line Items]
Federal COVID-19 provider relief funds received						$ 30,700,000
Eclipse
Schedule of Equity Method Investments [Line Items]
Ownership interest (as a percentage)			5.60%			5.60%
Carrying Value			$ 5,715,000			$ 5,715,000		9,483,000
Capitalized acquisition costs								1,300,000
Equity in earnings (losses) of unconsolidated ventures			(191,000)		1,090,000	(3,683,000)	758,000
Select Revenues and (Expenses), net			(463,000)		750,000	(4,381,000)	(402,000)
Cash Distributions			$ 0		2,286,000	$ 86,000	2,573,000
Envoy
Schedule of Equity Method Investments [Line Items]
Ownership interest (as a percentage)			11.40%			11.40%
Carrying Value			$ 9,000			$ 9,000		399,000
Equity in earnings (losses) of unconsolidated ventures			0		0	0	96,000
Select Revenues and (Expenses), net			0		0	0	(822,000)
Cash Distributions			$ 198,000		0	$ 390,000	4,339,000
Griffin-American
Schedule of Equity Method Investments [Line Items]
Ownership interest (as a percentage)			14.30%			14.30%
Carrying Value			$ 85,807,000			$ 85,807,000		125,597,000
Capitalized acquisition costs								13,400,000
Equity in earnings (losses) of unconsolidated ventures			185,000		(3,626,000)	(37,905,000)	(7,654,000)
Select Revenues and (Expenses), net			(2,273,000)		(6,234,000)	(44,729,000)	(16,046,000)
Cash Distributions			$ 0		1,030,000	$ 1,487,000	5,581,000
Espresso
Schedule of Equity Method Investments [Line Items]
Ownership interest (as a percentage)			36.70%			36.70%
Carrying Value			$ 0			$ 0		0
Capitalized acquisition costs								7,600,000
Equity in earnings (losses) of unconsolidated ventures			60,000		(667,000)	(522,000)	(3,034,000)
Select Revenues and (Expenses), net			(2,814,000)		(2,274,000)	(8,256,000)	(6,324,000)
Cash Distributions			$ 0		0	$ 0	0
Espresso | Mezzanine loans
Schedule of Equity Method Investments [Line Items]
Carrying Value									$ 0
Trilogy
Schedule of Equity Method Investments [Line Items]
Ownership interest (as a percentage)		23.00%	23.20%			23.20%				29.00%
Carrying Value			$ 138,726,000			$ 138,726,000		133,361,000
Capitalized acquisition costs								9,800,000
Ownership interest sold (as a percentage)		20.00%
Proceeds from sale of equity method investments		$ 48,000,000.0
Equity in earnings (losses) of unconsolidated ventures			(1,091,000)		156,000	5,365,000	2,188,000
Select Revenues and (Expenses), net			(3,052,000)		(3,776,000)	(10,404,000)	(10,433,000)
Cash Distributions			0		1,451,000	0	4,353,000
Federal COVID-19 provider relief funds received						7,100,000
Eclipse, Envoy, Griffin-American, Espresso, Trilogy
Schedule of Equity Method Investments [Line Items]
Carrying Value			230,257,000			230,257,000		268,840,000
Equity in earnings (losses) of unconsolidated ventures			(1,037,000)		(3,047,000)	(36,745,000)	(7,646,000)
Select Revenues and (Expenses), net			(8,602,000)		(11,534,000)	(67,770,000)	(34,027,000)
Cash Distributions			$ 198,000		4,767,000	$ 1,963,000	16,846,000
Operator Platform
Schedule of Equity Method Investments [Line Items]
Ownership interest (as a percentage)			20.00%			20.00%
Carrying Value			$ 0			$ 0		$ 54,000
Equity in earnings (losses) of unconsolidated ventures			(6,000)		10,000	(54,000)	(20,000)
Select Revenues and (Expenses), net			0		0	0	0
Cash Distributions			0		$ 0	$ 0	$ 0
Solstice Senior Living
Schedule of Equity Method Investments [Line Items]
Equity in earnings (losses) of unconsolidated ventures			$ (20,000)
Winterfell
Schedule of Equity Method Investments [Line Items]
Ownership interest (as a percentage)			20.00%			20.00%
Winterfell | Solstice Senior Living
Schedule of Equity Method Investments [Line Items]
Ownership interest (as a percentage)			80.00%			80.00%