SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Carrying Value of Long-Lived Assets (Details)	12 Months Ended
	Dec. 31, 2020 USD ($) mall other_property	Dec. 31, 2019 USD ($) mall	Dec. 31, 2018 USD ($) mall
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Impairment charges of real estate	$ 213,358,000	$ 239,521,000	$ 174,529,000
Number of malls with impairment | mall	6	6	5
Malls
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Impairment charges of real estate	$ 213,358,000
Number of malls with impairment | mall	6
Other Properties
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Impairment charges of real estate	$ 0
Number of other properties with impairment | other_property	7