OTHER INTANGIBLE ASSETS AND LIABILITIES - Intangible Assets and Liabilities and Related Accumulated Amortization and Accretion (Details) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2021	Dec. 31, 2020
Intangible lease assets:
Intangible lease assets, net	$ 5,498	$ 6,313
Intangible lease liabilities:
Acquired below-market leases, accumulated amortization	$ 1,063	$ 1,786
Acquired finite lived intangible lease liabilities average useful life	5 years	4 years
Acquired below-market leases, net of accumulated amortization of $1,063 and $1,786, respectively, with an average useful life of 5 and 4 years, respectively	$ 309	$ 587
Acquired below-market leases
Intangible lease liabilities:
Acquired below-market leases, net of accumulated amortization of $1,063 and $1,786, respectively, with an average useful life of 5 and 4 years, respectively	309	587
Acquired in-place Leases
Intangible lease assets:
Intangible lease assets, accumulated amortization	$ 8,786	$ 9,228
Acquired finite lived intangible lease assets average useful life	9 years	8 years
Intangible lease assets, net	$ 2,510	$ 3,316
Acquired above-market leases
Intangible lease assets:
Intangible lease assets, accumulated amortization	$ 24	$ 15
Acquired finite lived intangible lease assets average useful life	6 years	6 years
Intangible lease assets, net	$ 31	$ 40
Trade name and license
Intangible lease assets:
Intangible lease assets, net	$ 2,957	$ 2,957