CONCENTRATION OF CREDIT RISK - Triple-Net Leased Properties (Details) - Customer Concentration Risk	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Revenues | Brookdale Senior Living
Concentration Risk
Concentration percentage	4.10%	4.60%
Revenues | Ardent
Concentration Risk
Concentration percentage	3.50%	3.00%
Revenues | Kindred
Concentration Risk
Concentration percentage	3.60%	3.20%
NOI | Brookdale Senior Living
Concentration Risk
Concentration percentage	8.80%	8.80%
NOI | Ardent
Concentration Risk
Concentration percentage	7.50%	5.80%
NOI | Kindred
Concentration Risk
Concentration percentage	7.80%	6.20%