Acquisitions, Dispositions and Other Significant Transactions - Ventas Lease Portfolio Restructuring (Details)		3 Months Ended				12 Months Ended
	Apr. 26, 2018 USD ($) extension_option community	Dec. 31, 2018 USD ($)	Sep. 30, 2018 USD ($)	Jun. 30, 2018 USD ($)	Mar. 31, 2018 USD ($)	Dec. 31, 2018 USD ($) community	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)	Apr. 26, 2019 USD ($)	Jan. 01, 2019
Business Acquisition [Line Items]
Loss on facility lease termination and modification, net		$ 13,197,000	$ 2,337,000	$ 146,467,000	$ 0	$ 162,001,000	$ 14,276,000	$ 11,113,000
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 communities added to agreement | community						17
Number of communities to be added to agreement | community						4
Number of extensions | extension_option	2
Extension term	10 years
Rent expense						$ 175,000,000
Rent credit		8,000,000				8,000,000
Rent credit after change of control		$ 5,000,000				$ 5,000,000
Investment minimum, unit per lease	$ 2,000
Period of lease	24 months
Investment in capital improvements	$ 30,000,000
Payment for change of control fees	$ 25,000,000
Management percent fee						5.00%
Loss on facility lease termination and modification, net						$ 125,700,000
Forecast | Ventas, Inc | Master Lease And Security Agreement
Business Acquisition [Line Items]
Rent credit									$ 5,000,000	$ 7,000,000	$ 8,000,000
Option to terminate, annual base rent												$ 30,000,000
Option to terminate, rent reduction percentage												6.25%
Subsequent event | Ventas, Inc | Master Lease And Security Agreement
Business Acquisition [Line Items]
Base rent escalator, CPI increase													2.25%
Base rent escalator, CPI increase multiplier													4
Base rent escalator, CPI decrease													0.00%