Acquisitions, Dispositions and Other Significant Transactions - Ventas Lease Portfolio Restructuring (Details)		3 Months Ended								12 Months Ended
	Apr. 26, 2018 USD ($) extension_option community	Dec. 31, 2019 USD ($) lease	Sep. 30, 2019 USD ($)	Jun. 30, 2019 USD ($)	Mar. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Sep. 30, 2018 USD ($)	Jun. 30, 2018 USD ($)	Mar. 31, 2018 USD ($)	Dec. 31, 2019 USD ($) lease community	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)	Jan. 01, 2019
Business Acquisition [Line Items]
Number of communities leased | lease		242								242
Loss on facility lease termination and modification, net		$ (1,382,000)	$ 0	$ (1,797,000)	$ (209,000)	$ (13,197,000)	$ (2,337,000)	$ (146,467,000)	$ 0	$ 3,388,000	$ 162,001,000	$ 14,276,000
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	18
Number of communities to be added to agreement | community	3
Number of extensions | extension_option	2
Extension term		10 years								10 years
Rent expense											175,000,000.0
Rent credit		$ 8,000,000.0				8,000,000.0				$ 8,000,000.0	$ 8,000,000.0
Rent credit after change of control		$ 5,000,000.0								$ 5,000,000.0
Base rent escalator, CPI increase															2.25%
Base rent escalator, CPI increase multiplier															4
Base rent escalator, CPI decrease															0.00%
Investment minimum, unit per lease	$ 2,000
Period of lease	24 months
Investment in capital improvements	$ 30,000,000.0
Payment for change of control fees	$ 25,000,000.0
Option to terminate, rent reduction percentage	6.25%
Management percent fee										5.00%
Loss on facility lease termination and modification, net						$ (125,700,000)
Number of communities exercised to market for sale and sold | community										7
Reduction of rent for terminating communities										$ 1,700,000
Forecast | Ventas, Inc | Master Lease And Security Agreement
Business Acquisition [Line Items]
Rent credit													$ 5,000,000.0	$ 7,000,000.0