Dispositions of Real Estate and Discontinued Operations - Narrative (Details)	1 Months Ended										3 Months Ended							9 Months Ended		12 Months Ended	21 Months Ended
	Jul. 31, 2022 USD ($) property	Feb. 28, 2022 USD ($)	Jan. 31, 2022 USD ($) property	Sep. 30, 2021 USD ($) loan	Jun. 30, 2021 USD ($) property	May 31, 2021 USD ($) property	Apr. 30, 2021 USD ($) property	Mar. 31, 2021 USD ($) property	Feb. 28, 2021 USD ($) property	Jan. 31, 2021 USD ($) property	Sep. 30, 2022 USD ($)	Jun. 30, 2022 USD ($) property	Mar. 31, 2022 USD ($)	Dec. 31, 2021 USD ($) property	Sep. 30, 2021 USD ($) property	Jun. 30, 2021 USD ($)	Mar. 31, 2021 USD ($) property	Sep. 30, 2022 USD ($) loan	Sep. 30, 2021 USD ($) property	Dec. 31, 2021 loan	Sep. 30, 2022 USD ($)
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Gain (loss) on sales of real estate, net											$ (4,149,000)				$ 14,635,000			$ 10,047,000	$ 189,873,000
Carrying value of mortgages assumed by buyer in real estate dispositions																		$ 0	$ 143,676,000
Number of loans sold | loan				1														1		6
Impairment of real estate											0							$ 0
Number of properties impaired | property															2				2
Goodwill, impairment loss															$ 0				$ 0
Planned MOB Demolition, Tenant Relocation and Other Costs
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Expense on other													$ 14,000,000
Mortgage Debt
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of assets classified as discontinued operations | property						6	2	2									2
Repayments of secured debt							$ 64,000,000	$ 39,000,000
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														$ 1,000,000
Held-for-sale
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Goodwill, impairment loss															22,000,000	$ 7,000,000			29,000,000
Goodwill											$ 0							$ 0			$ 0
Sunrise Senior Housing Portfolio | SHOP
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Capital expenditure funding, amount committed	$ 40,000,000	$ 47,000,000			$ 56,000,000					$ 92,000,000
Capital expenditure funding, amount funded																					$ 400,000
Oakmont SHOP Portfolio
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Carrying value of mortgages assumed by buyer in real estate dispositions							$ 107,000,000
Oakmont SHOP Portfolio | Mortgage Debt
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of properties disposed | property							4
Other Dispositions
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Carrying value of mortgages assumed by buyer in real estate dispositions																			$ 36,000,000
Other Dispositions | Mortgage Debt
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of properties disposed | property																			1
Other Dispositions | 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															27,000,000				$ 34,000,000
Other Dispositions | 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															42,000,000				52,000,000
SHOP
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Proceeds from sale of buildings										230,000,000
Gain (loss) on sales of real estate, net										59,000,000							$ 16,000,000
Payments to acquire finance receivables										150,000,000
SHOP | Oakmont SHOP Portfolio
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Proceeds from sale of buildings							$ 564,000,000
Gain (loss) on sales of real estate, net							80,000,000
SHOP | Discovery SHOP Portfolio
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Proceeds from sale of buildings							334,000,000
Gain (loss) on sales of real estate, net							9,000,000
Proceeds from sale of loans and preferred equity method investments							21,000,000
SHOP | Sonata SHOP Portfolio
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Proceeds from sale of buildings							64,000,000
Gain (loss) on sales of real estate, net							$ 3,000,000
SHOP | Other Dispositions
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Proceeds from sale of buildings															120,000,000				169,000,000
Senior Housing Triple Net
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Proceeds from sale of buildings															12,000,000
Senior Housing Triple Net | Brookdale Triple Net Portfolio
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Proceeds from sale of buildings										510,000,000
Gain (loss) on sales of real estate, net										$ 169,000,000
Senior Housing Triple Net | HRA Triple Net Portfolio
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Proceeds from sale of buildings									$ 132,000,000
Gain (loss) on sales of real estate, net									$ 33,000,000
Senior Housing Triple Net | Other Dispositions
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Proceeds from sale of buildings																			24,000,000
Life Science
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of properties sold | property			1
Proceeds from sale of buildings			$ 14,000,000
Gain (loss) on sales of real estate, net			$ 4,000,000
Medical Office Buildings
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of properties sold | property	2											3		3
Proceeds from sale of buildings	$ 9,000,000											$ 27,000,000		$ 11,000,000
Gain (loss) on sales of real estate, net	$ 1,000,000											$ 10,000,000
Impairment of real estate															$ 2,000,000				$ 2,000,000
Number of real estate properties impaired | property															2				2
Medical Office Buildings | Other Dispositions
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of properties sold | property															3				7
Proceeds from sale of buildings															$ 36,000,000				$ 57,000,000
Medical Office Buildings | Impairments 2021
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Real estate investment property, aggregate carrying value before impairment				$ 13,000,000											13,000,000				13,000,000
Real estate held-for-sale				$ 11,000,000											$ 11,000,000				11,000,000
MOB Land Parcels
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of properties sold | property												1		1
SHOP
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of properties sold | property										16
Impairment of real estate																			$ 4,000,000
Number of real estate properties impaired | property															1				1
Real estate investment property, aggregate carrying value before impairment					20,000,000											20,000,000
Real estate held-for-sale					16,000,000											$ 16,000,000
SHOP | Sunrise Senior Housing Portfolio
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of properties sold | property										32
Proceeds from sale of buildings										$ 664,000,000
Gain (loss) on sales of real estate, net					$ 7,000,000
Payments to acquire finance receivables										$ 410,000,000
SHOP | Oakmont SHOP Portfolio
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of properties sold | property							12
SHOP | Discovery SHOP Portfolio
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of properties sold | property							10
Gain (loss) on sales of real estate, net							$ 0
Number of preferred equity method investments sold | property							2
SHOP | Discovery SHOP Portfolio | Mezzanine and Other
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of loans sold | property							2
SHOP | Sonata SHOP Portfolio
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of properties sold | property							5
SHOP | SLC SHOP Portfolio
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of properties sold | property						7
Repayments of secured debt						$ 70,000,000
SHOP | SLC SHOP Portfolio | Definitive Agreement Four
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Proceeds from sale of buildings						113,000,000
Gain (loss) on sales of real estate, net						$ 1,000,000
SHOP | Other Dispositions
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of properties sold | property															8				15
Senior Housing Triple Net | Sunrise Senior Housing Portfolio
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of properties sold | property					2
Proceeds from sale of buildings					$ 80,000,000
Gain (loss) on sales of real estate, net					$ 22,000,000
Senior Housing Triple Net | Brookdale Triple Net Portfolio
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of properties sold | property										24
Senior Housing Triple Net | HRA Triple Net Portfolio
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of properties sold | property									8
Senior Housing Triple Net | Other Dispositions
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of properties sold | property															4				7
Medical Office, Hospital
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of properties sold | property						1
Proceeds from sale of buildings						$ 226,000,000
Gain (loss) on sales of real estate, net						$ 172,000,000