Concentration of Credit Risk - Triple-Net Leased Properties (Details) $ / shares in Units, $ in Thousands, shares in Millions	1 Months Ended			12 Months Ended
	Apr. 30, 2020 USD ($) senior_housing	Jul. 31, 2018 USD ($)	Apr. 30, 2018 USD ($) period Lease	Dec. 31, 2020 USD ($) property	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Jul. 31, 2020 USD ($)	Jul. 31, 2020 property	Jul. 31, 2020	Jul. 31, 2020 shares	Jul. 31, 2020 $ / shares	Jul. 31, 2020 senior_housing
Real estate properties
Other noncash expense				$ 779	$ (13,264)	$ (3,720)
Cash and cash equivalents				413,327	106,363
Non-mortgage loans receivable, net				$ 57,077	63,724
Loan receivable Stated Interest Rate									9.00%
Operating Lease, Lease Income, Lease Payments, Annual Increase									3.00%
Number of real estate properties | property				1,200
Secured/mortgage loans and other, net
Real estate properties
Debt Securities, Held-to-maturity				$ 555,840	$ 645,546
Brookdale Senior Living
Real estate properties
Other noncash expense			$ (21,300)	$ (21,300)
Cash and cash equivalents							$ 162,000
Non-mortgage loans receivable, net							45,000
Loan receivable Stated Interest Rate									9.00%
Loan Receivable, Interest Rate, Annual Increase									0.50%
Stock warrants							28,000
Class of Warrant or Right, Number of Securities Called by Warrants or Rights | shares										16.3
Class of Warrant or Right, Exercise Price of Warrants or Rights | $ / shares											$ 3.00
Lessor, Operating Lease, Payments to be Received, Next Rolling Twelve Months							100,000
Master leases | Lease			1
Options to extend term of lease | period			2
Lease renewal term			10 years
Proceeds from fees received			$ 2,500
Brookdale Senior Living | Secured/mortgage loans and other, net
Real estate properties
Debt Securities, Held-to-maturity							78,000
Brookdale Senior Living | Collateral Pledged
Real estate properties
Number of real estate properties								5				5
Brookdale Senior Living | Transfer Of Lease Deposit To Cash
Real estate properties
Cash and cash equivalents							47,000
Brookdale Senior Living | Up-front Payment Arrangement
Real estate properties
Contract with Customer, Liability							$ 235,000
Brookdale Senior Living | Revenues
Real estate properties
Concentration risk				4.40%	4.70%	4.30%
Brookdale Senior Living | Net Operating Income
Real estate properties
Concentration risk				9.00%	8.70%	7.60%
Ardent | Revenues
Real estate properties
Concentration risk				3.20%	3.10%	3.10%
Ardent | Net Operating Income
Real estate properties
Concentration risk				6.60%	5.80%	5.70%
Kindred
Real estate properties
Proceeds from fees received		$ 12,300
Kindred | Revenues
Real estate properties
Concentration risk				3.50%	3.30%	3.50%
Kindred | Net Operating Income
Real estate properties
Concentration risk				7.10%	6.30%	6.40%
Holiday Management Company Member
Real estate properties
Number of real estate properties | senior_housing	26
Gain (Loss) on Contract Termination	$ 50,200
Operating Lease, Lease Termination Consideration Received	99,800
Loans and Leases Receivable, Allowance	49,600
Holiday Management Company Member | Secured/mortgage loans and other, net
Real estate properties
Debt Securities, Held-to-maturity	66,000
Holiday Management Company Member | Transfer Of Lease Deposit To Cash
Real estate properties
Cash and cash equivalents	$ 33,800