CONCENTRATION OF CREDIT RISK - Triple-Net Leased Properties (Details) - Customer Concentration Risk	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020
Revenues | Brookdale Senior Living
Concentration Risk
Concentration percentage	3.80%	4.00%
Revenues | Ardent
Concentration Risk
Concentration percentage	3.30%	3.30%
Revenues | Kindred
Concentration Risk
Concentration percentage	3.50%	3.60%
NOI | Brookdale Senior Living
Concentration Risk
Concentration percentage	8.20%	8.80%
NOI | Ardent
Concentration Risk
Concentration percentage	7.10%	7.20%
NOI | Kindred
Concentration Risk
Concentration percentage	7.50%	7.80%