Summary of Significant Accounting Policies - Narrative (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2019 USD ($) facility		Dec. 31, 2018 USD ($)		Sep. 30, 2020 USD ($) property	Jun. 30, 2020 USD ($)	Jan. 31, 2020 facility	Jan. 31, 2020 property	Jan. 01, 2020 USD ($)	Oct. 31, 2019 property	Sep. 30, 2019 USD ($)	Jun. 30, 2019 USD ($)	Jan. 01, 2019 USD ($)
Schedule of Equity Method Investments [Line Items]
Accounting Standards Update [Extensible List]	us-gaap:AccountingStandardsUpdate201613Member		us-gaap:AccountingStandardsUpdate201602Member
Cumulative effect adjustment	$ 6,667,474		$ 6,512,591		$ 7,406,308	$ 7,668,721					$ 6,523,359	$ 6,619,272
Present value of lease liabilities	156,611				175,002
Right-of-use asset	172,486				190,875
Unamortized lease intangibles	(331,693)				$ (501,583)
Accounting Standards Update 2016-02
Schedule of Equity Method Investments [Line Items]
Present value of lease liabilities													$ 153,000
Right-of-use asset													166,000
Accrued straight-line rent liability													20,000
Unamortized lease intangibles													33,000
Cumulative Effect, Period of Adoption, Adjustment
Schedule of Equity Method Investments [Line Items]
Cumulative effect adjustment	$ (1,524)	[1]	$ 590	[2]					$ 2,000				$ 1,000
CCRC JV | Brookedale MTCA
Schedule of Equity Method Investments [Line Items]
Property count | property								15
Other Non-reportable Segments | Assets Leased to Others | CCRC JV
Schedule of Equity Method Investments [Line Items]
Property count							15	15		15
Other Non-reportable Segments | Assets Leased to Others | CCRC JV | Brookedale MTCA
Schedule of Equity Method Investments [Line Items]
Property count					13		13	13
SHOP
Schedule of Equity Method Investments [Line Items]
Number of deconsolidating assets	19				19

[1] On January 1, 2020, the Company adopted a series of Accounting Standards Updates (“ASUs”) related to accounting for credit losses and recognized the cumulative-effect of adoption to beginning retained earnings. Refer to Note 2 for a detailed impact of adoption.

[2] On January 1, 2019, the Company adopted a series of ASUs related to accounting for leases and recognized the cumulative-effect of adoption to beginning retained earnings. Refer to Note 2 for a detailed impact of adoption.