Amount of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates. Excludes cash and cash equivalents within disposal group and discontinued operation.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=121586364&loc=d3e3044-108585

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section 45
-Paragraph 1
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=121566466&loc=d3e6676-107765

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.1)
-URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

CONCENTRATION OF CREDIT RISK - Narrative (Details) $ / shares in Units, shares in Millions	1 Months Ended	3 Months Ended		9 Months Ended
	Apr. 30, 2020 USD ($) senior_housing	Sep. 30, 2020 USD ($) property state province	Sep. 30, 2019 USD ($)	Sep. 30, 2020 USD ($) property state province	Sep. 30, 2019 USD ($)	Jan. 01, 2022	Jul. 31, 2020 USD ($) property $ / shares shares	Jun. 30, 2020 USD ($)	Dec. 31, 2019 USD ($)
Concentration Risk
Number of real estate properties \| property		1,200		1,200
Cash and cash equivalents		$ 588,343,000		$ 588,343,000					$ 106,363,000
Non-mortgage loans receivable, net		56,844,000		56,844,000					63,724,000
Rental income		354,512,000	$ 408,322,000	1,126,934,000	$ 1,208,388,000
Secured/mortgage loans and other, net
Concentration Risk
Debt securities, held-to-maturity		$ 555,483,000		$ 555,483,000					$ 645,546,000
Consolidated Seniors Housing Communities
Concentration Risk
Number of real estate properties \| property		431		431
Brookdale Senior Living
Concentration Risk
Cash and cash equivalents							$ 162,000,000
Non-mortgage loans receivable, net							$ 45,000,000
Loan receivable, interest rate							9.00%
Loan receivable, interest rate annual increase							0.50%
Number of securities called by warrants \| shares							16.3
Warrants, exercise price \| $ / shares							$ 3.00
Lessor, Operating Lease, Payments to be Received, Next Rolling Twelve Months							$ 100,000,000
Warrants and Rights Outstanding							28,000,000
Brookdale Senior Living \| Up-front Payment Arrangement [Member]
Concentration Risk
Deferred Revenue							$ 235,000,000
Brookdale Senior Living \| Forecast
Concentration Risk
Annual increase of lease payment						3.00%
Brookdale Senior Living \| Secured/mortgage loans and other, net
Concentration Risk
Debt securities, held-to-maturity								$ 78,000,000
Brookdale Senior Living \| Collateral Pledged [Member]
Concentration Risk
Number of real estate properties \| property							5
Brookdale Senior Living \| Transfer of escrow deposit to cash [Member]
Concentration Risk
Cash and cash equivalents							$ 47,000,000
Atria and Sunrise \| Consolidated Seniors Housing Communities
Concentration Risk
Number of real estate properties \| property		258		258
Holiday Management Company
Concentration Risk
Number of real estate properties \| senior_housing	26
Loans and leases receivable, allowance	$ 49,600,000
Lease termination consideration received	99,800,000
Gain (Loss) on Contract Termination	50,200,000
Holiday Management Company \| Secured/mortgage loans and other, net
Concentration Risk
Debt securities, held-to-maturity	66,000,000
Holiday Management Company \| Transfer of escrow deposit to cash [Member]
Concentration Risk
Cash and cash equivalents	$ 33,800,000
Customer Concentration Risk \| Total Gross Book Value of Properties \| Hospitals, Medical Office Building and Other
Concentration Risk
Concentration percentage				36.30%
Customer Concentration Risk \| Total Gross Book Value of Properties \| Senior Living Operations \| Senior Housing Communities
Concentration Risk
Concentration percentage				47.30%
Customer Concentration Risk \| Total Gross Book Value of Properties \| Triple-Net Leased Properties \| Senior Housing Communities
Concentration Risk
Concentration percentage				16.40%
Customer Concentration Risk \| Total Gross Book Value of Properties \| Atria
Concentration Risk
Concentration percentage				20.60%
Customer Concentration Risk \| Total Gross Book Value of Properties \| Sunrise
Concentration Risk
Concentration percentage				10.40%
Customer Concentration Risk \| Total Gross Book Value of Properties \| Brookdale Senior Living
Concentration Risk
Concentration percentage				8.10%
Customer Concentration Risk \| Total Gross Book Value of Properties \| Ardent
Concentration Risk
Concentration percentage				4.90%
Customer Concentration Risk \| Total Gross Book Value of Properties \| Kindred
Concentration Risk
Concentration percentage				1.10%
Geographic Concentration Risk
Concentration Risk
Number of states in which entity operates \| state		45		45
Number of states accounting for more than 10% of total revenues and net operating income \| state		1		1
Continuing revenues and NOI threshold				10.00%
Geographic Concentration Risk \| CANADA
Concentration Risk
Number of Canadian provinces in which entity operates \| province		7		7