Dispositions of Real Estate and Discontinued Operations - 2020 Dispositions of Real Estate (Details) $ in Thousands	1 Months Ended			3 Months Ended		12 Months Ended
	Jul. 31, 2022 USD ($) property	Jan. 31, 2021 USD ($) property	Dec. 31, 2020 USD ($) property	Jun. 30, 2022 USD ($) property	Mar. 31, 2021 USD ($)	Dec. 31, 2022 USD ($)	Dec. 31, 2021 USD ($) property	Dec. 31, 2020 USD ($) property
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Repayments of secured debt			$ 6,000
Number of assets classified as discontinued operations | property			1					1
Gain (loss) on sales of real estate, net						$ 9,078	$ 190,590	$ 90,350
Net cash provided by (used in) financing activities						$ (116,532)	(1,288,517)	246,450
Other Investments | Disposal Group, Disposed of by Means Other than Sale, Not Discontinued Operations, Abandonment
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Gain (loss) on sales of real estate, net							58,000	283,000
Other Investments | Discontinued Operations
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Gain (loss) on sales of real estate, net							39,000	193,000
Atria SHOP Portfolio
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of assets sold | property			12
Senior Housing Operating Portfolio
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Proceeds from sale of buildings		$ 230,000
Gain (loss) on sales of real estate, net		59,000			$ 16,000
Net cash provided by (used in) financing activities		$ 150,000
Senior Housing Operating Portfolio | Atria SHOP Portfolio
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Proceeds from sale of buildings			$ 312,000
Gain (loss) on sales of real estate, net			39,000
Senior Housing Operating Portfolio | Other Investments
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Proceeds from sale of buildings							169,000	$ 190,000
Senior Housing Triple Net | Aegis NNN Portfolio
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Proceeds from sale of buildings			358,000
Gain (loss) on sales of real estate, net			$ 228,000
Senior Housing Triple Net | Other Investments
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of assets sold | property								21
Proceeds from sale of buildings							$ 24,000	$ 428,000
Medical Office | Other Investments
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Proceeds from sale of buildings								136,000
MOB Land Parcels | Other Investments
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Proceeds from sale of buildings								$ 3,000
Senior Housing Triple Net | Aegis NNN Portfolio
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of assets sold | property			10
Senior Housing Triple Net | Other Investments
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of assets sold | property							7
Senior Housing Operating Portfolio
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of assets sold | property		16
Senior Housing Operating Portfolio | Atria SHOP Portfolio
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of assets sold | property			4
Net cash provided by (used in) financing activities			$ 61,000
Senior Housing Operating Portfolio | Other Investments
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of assets sold | property							15	23
Medical Office
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of assets sold | property	2			3
Proceeds from sale of buildings	$ 9,000			$ 27,000
Gain (loss) on sales of real estate, net	$ 1,000			$ 10,000
Medical Office | Other Investments
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of assets sold | property							10	11
Proceeds from sale of buildings							$ 68,000
Medical Office | Other Investments | San Diego
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of assets sold | property								3
MOB Land Parcels
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of assets sold | property				1
MOB Land Parcels | Other Investments
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of assets sold | property							1	2
Other Non-Reporting Segment | Other Investments
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of assets sold | property								1
Proceeds from sale of buildings								$ 1,000