Acquisitions, Dispositions and Other Significant Transactions - Healthpeak CCRC Venture and Master Lease Transactions (Details) $ in Thousands		12 Months Ended
	Oct. 01, 2019 USD ($) entry_fee extension_option community	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)
Business Acquisition [Line Items]
Number of additional entry fee | entry_fee	1
Base rent		$ 303,294	$ 339,721
CCRC Venture | CCRCs
Business Acquisition [Line Items]
Percentage of voting interests acquired	51.00%
Number of entry fee | entry_fee	14
Purchase price	$ 295,200
Payments to acquire interest in joint venture	$ 1,060,000
Number of entry fee sales | entry_fee	2
HCP, Inc. | CCRCs
Business Acquisition [Line Items]
Payments for management agreement termination fee	$ 100,000
Master Lease Transactions
Business Acquisition [Line Items]
Number of continuing communities | community	24
Base rent	$ 41,700
Annual escalator rate	2.40%
Initial lease rate	7.00%
Master Lease Transactions | HCP, Inc.
Business Acquisition [Line Items]
Payments to acquire interest in joint venture	$ 405,500
Number of communities leased | community	25
Number of communities, acquired, currently leased | community	18
Number of lease communities transferred to successor operator | community	1
Number of continuing communities | community	24
Number of extensions | extension_option	2
Term of number of extensions	10 years
Capital expenditures	$ 35,000
Non-Recourse First Mortgages | Master Lease Transactions
Business Acquisition [Line Items]
Proceeds from issuance of debt	$ 192,600