Credit Concentration - Summary of Credit Concentration (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2021 USD ($) property	Mar. 31, 2020 USD ($)	Dec. 31, 2020
Concentration Risk [Line Items]
Total NOI	$ 434,736	$ 576,821
Percentage total investments with top five customers			36.00%
Net operating income
Concentration Risk [Line Items]
Number of Properties | property	1,498
Total NOI	$ 434,736
Percent of NOI	100.00%
Net operating income | Sunrise Senior Living
Concentration Risk [Line Items]
Number of Properties | property	165
Total NOI	$ 60,933
Percent of NOI	14.00%
Net operating income | ProMedica
Concentration Risk [Line Items]
Number of Properties | property	216
Total NOI	$ 53,031
Percent of NOI	13.00%
Net operating income | Genesis Healthcare
Concentration Risk [Line Items]
Number of Properties | property	52
Total NOI	$ 26,871
Percent of NOI	7.00%
Net operating income | Revera
Concentration Risk [Line Items]
Number of Properties | property	92
Total NOI	$ 20,865
Percent of NOI	5.00%
Net operating income | Avery Healthcare
Concentration Risk [Line Items]
Number of Properties | property	61
Total NOI	$ 20,623
Percent of NOI	5.00%
Net operating income | Remaining portfolio
Concentration Risk [Line Items]
Number of Properties | property	912
Total NOI	$ 252,413
Percent of NOI	56.00%