FAIR VALUE MEASUREMENTS - Financial Assets and Liabilities Not Measured at Fair Value (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
FINANCIAL LIABILITIES
Unsecured senior notes	$ 319,236	$ 269,246
Mortgages payable	615,001
Carrying Amount
FINANCIAL ASSETS
Cash and cash equivalents	10,816	392
FINANCIAL LIABILITIES
Revolving lines of credit	181,544	152,871
Term loans	145,000	145,000
Unsecured senior notes	175,000	125,000
Mortgages payable	295,001	298,445
Carrying Amount | Restricted cash
FINANCIAL ASSETS
Cash and cash equivalents	1,610	6,918
Fair Value
FINANCIAL ASSETS
Cash and cash equivalents	10,816	392
FINANCIAL LIABILITIES
Revolving lines of credit	181,544	152,871
Term loans	145,000	145,000
Unsecured senior notes	179,630	133,181
Mortgages payable	301,538	308,855
Fair Value | Restricted cash
FINANCIAL ASSETS
Cash and cash equivalents	$ 1,610	$ 6,918