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TRANSACTIONS WITH RELATED PARTIES - Narrative (Details) - 12 months ended Dec. 31, 2019
$ in Millions
property
USD ($)
apartment_community
Related Party Transaction [Line Items]      
Number of real estate properties sold 28   12
BMO Capital Markets      
Related Party Transaction [Line Items]      
Number of real estate properties sold | property 27    
Transaction fee | $   $ 1.8