INTANGIBLE ASSETS - Intangible Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Intangible assets, net:
Intangible assets, total cost	$ 94,173	$ 177,581
Intangible assets, accumulated amortization	(45,603)	(92,730)
Intangible assets, net	48,570	84,851
Intangible liabilities, net:
Acquired lease intangibles, gross	31,263	44,757
Acquired lease intangibles, accumulated amortization	(12,815)	(22,494)
Acquired lease intangibles, net	18,448	22,263
In-place lease value
Intangible assets, net:
Intangible assets, total cost	91,552	167,357
Intangible assets, accumulated amortization	(43,400)	(84,123)
Intangible assets, net	48,152	83,234
Tenant relationship value
Intangible assets, net:
Intangible assets, total cost	2,091	5,268
Intangible assets, accumulated amortization	(1,938)	(4,815)
Intangible assets, net	153	453
Above market leases acquired
Intangible assets, net:
Intangible assets, total cost	530	4,956
Intangible assets, accumulated amortization	(265)	(3,792)
Intangible assets, net	$ 265	$ 1,164