TENANT ORIGINATION AND ABSORPTION COSTS, ABOVE-MARKET LEASE ASSETS AND BELOW-MARKET LEASE LIABILITIES - Cost and Amortization (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Tenant Origination and Absorption Costs, Above-Market Lease Assets and Below-Market Lease Liabilities [Abstract]
Tenant Origination And Absorption Costs, Cost	$ 27,984		$ 27,984		$ 30,569
Tenant Origination and Absorption Costs, Accumulated Amortization	(11,861)		(11,861)		(10,223)
Tenant Origination and Absorption Costs, Net Amount	16,123		16,123		20,346
Tenant Origination and Absorption Costs, Amortization	(1,625)	$ (2,000)	(4,965)	$ (5,324)
Above-Market Lease Assets, Cost	3,499		3,499		3,714
Above-Market Lease Assets, Accumulated Amortization	(767)		(767)		(741)
Above-Market Lease Assets, Net Amount	2,732		2,732		2,973
Above-Market Lease Assets, Amortization	(74)	(101)	(241)	(303)
Below-Market Lease Liabilities, Cost	(4,122)		(4,122)		(4,958)
Below-Market Lease Liabilities, Accumulated Amortization	1,618		1,618		1,778
Below-Market Lease Liabilities, Net Amount	(2,504)		(2,504)		$ (3,180)
Below-Market Lease Liabilities, Amortization	$ 194	$ 421	$ 676	$ 1,159