Impairments of Real Estate (Details)	3 Months Ended			12 Months Ended
	Dec. 31, 2021 USD ($) property	Sep. 30, 2021 USD ($)	Jun. 30, 2021 USD ($)	Dec. 31, 2023 USD ($)	Dec. 31, 2022 USD ($) property	Dec. 31, 2021 USD ($) property
Impaired Long-Lived Assets Held and Used [Line Items]
Impairment of real estate				$ 0	$ 0
Net real estate				13,028,363,000	13,023,483,000
Goodwill, impairment loss				0	0	$ 0
Goodwill				18,000,000	18,000,000
Insured event loss				3,085,000	(7,168,000)	(1,632,000)
Casualty-Related Losses
Impaired Long-Lived Assets Held and Used [Line Items]
Insured event loss				(3,000,000)	6,000,000	5,000,000
Casualty-Related Losses | Rental Revenues And Resident Fees And Services
Impaired Long-Lived Assets Held and Used [Line Items]
Insured event loss				$ 4,000,000	3,000,000	$ 0
SWF SH JV and Winter Storm Uri
Impaired Long-Lived Assets Held and Used [Line Items]
Property count | property	1					1
Planned MOB Demolition, Tenant Relocation And Other Costs
Impaired Long-Lived Assets Held and Used [Line Items]
Expense on other					$ 14,000,000
Held-for-sale
Impaired Long-Lived Assets Held and Used [Line Items]
Goodwill, impairment loss		$ 22,000,000	$ 7,000,000			$ 29,000,000
Goodwill	$ 0					0
Outpatient Medical
Impaired Long-Lived Assets Held and Used [Line Items]
Impairment of real estate						$ 22,000,000
Number of real estate properties impaired | property						3
Property count | property	4				3	4
Outpatient Medical | Held-for-use
Impaired Long-Lived Assets Held and Used [Line Items]
Number of real estate properties impaired | property						1
Outpatient Medical | Held-for-use | Impairments 2021
Impaired Long-Lived Assets Held and Used [Line Items]
Impairment of real estate	$ 17,000,000
Outpatient Medical | Held-for-sale
Impaired Long-Lived Assets Held and Used [Line Items]
Number of real estate properties impaired | property						3
Outpatient Medical | Held-for-sale | Impairments 2021
Impaired Long-Lived Assets Held and Used [Line Items]
Impairment of real estate						$ 5,000,000
Net real estate	14,000,000					14,000,000
Senior Housing Operating Portfolio
Impaired Long-Lived Assets Held and Used [Line Items]
Impairment of real estate						$ 4,000,000
Number of real estate properties impaired | property						1
Senior Housing Operating Portfolio | Impairments 2021
Impaired Long-Lived Assets Held and Used [Line Items]
Aggregate carrying value before impairment	20,000,000					$ 20,000,000
Real estate held-for-sale	$ 16,000,000					$ 16,000,000