Acquisitions, Dispositions and Other Significant Transactions - Ventas Lease Portfolio Restructuring (Details)		3 Months Ended		6 Months Ended		12 Months Ended
	Apr. 26, 2018 USD ($) community extension_option	Jun. 30, 2018 USD ($)	Jun. 30, 2017 USD ($)	Jun. 30, 2018 USD ($)	Jun. 30, 2017 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)	Apr. 26, 2019 USD ($)
Business Acquisition [Line Items]
Loss on facility lease termination and modification		$ 146,467,000	$ 6,368,000	$ 146,467,000	$ 6,368,000
Ventas, Inc | Master Lease And Security Agreement
Business Acquisition [Line Items]
Number of communities leased | community	128
Prior number of communities | community	107
Additional number of communities | community	21
Number of extensions | extension_option	2
Extension term	10 years
Investment minimum, unit per lease	$ 2,000
Investment in capital improvements	$ 30,000,000
Period of lease	24 months
Payment for change of control fees	$ 25,000,000
Loss on facility lease termination and modification		$ 125,700,000		$ 125,700,000
Forecast | Ventas, Inc | Master Lease And Security Agreement
Business Acquisition [Line Items]
Rent expense						$ 175,000,000
Rent credit						8,000,000	$ 5,000,000	$ 7,000,000	$ 8,000,000
Rent credit after change of control						$ 5,000,000
Base rent escalator, CPI increase						2.25%
Base rent escalator, CPI decrease						0.00%
Option to terminate, annual base rent										$ 30,000,000
Option to terminate, rent reduction percentage										6.25%