Dispositions, Real Property Held for Sale and Impairment - Narrative (Details) $ in Thousands	6 Months Ended
	Jun. 30, 2021 USD ($) property	Jun. 30, 2020 USD ($) property	Dec. 31, 2020 USD ($)	[1]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Real property held for sale | $	$ 592,699		$ 216,613
Expected proceeds from properties held for sale | $	747,153
Impairment of assets held for use | $	18,077
Held for sale
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Real property held for sale | $	$ 20,382
Seniors Housing Operating
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of properties classified as held for sale | property	2
Impairment of assets held for use | $	$ 29,183
Impairment of assets held for sale | $		$ 75,151
Number of properties held for use | property	2	12
Triple-net
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of properties classified as held for sale | property	54
Impairment of assets held for use | $		$ 27,827
Number of properties subject to asset impairment | property	3
Number of properties held for use | property	2	1
Outpatient Medical
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of properties classified as held for sale | property	2
Number of properties subject to asset impairment | property	1

[1] Note: The consolidated balance sheet at December 31, 2020 has been derived from the audited financial statements at that date but does not include all of the information and footnotes required by U.S. generally accepted accounting principles for complete financial statements.