SIGNIFICANT ACCOUNTING POLICIES (Schedule of Consolidated Statements of Cash Flows - Supplemental Disclosures) (Details) - USD ($) $ in Thousands	3 Months Ended						9 Months Ended
	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2020	Sep. 30, 2019
Supplemental disclosure of cash flow information:
Interest paid							$ 6,986	$ 3,359
Supplemental disclosure of non-cash investing and financing activities:
Stock dividend paid on preferred stock	$ 2,125	$ 2,125	$ 2,125	$ 2,125	$ 2,125	$ 2,125	6,375	6,375
Dividends declared, but not paid, on preferred stock							5,309	5,157
Dividends declared, but not paid, on common stock							0	7,783
Dividends declared, but not paid, on OC Units							0	0
Reclassification of development property investments to self-storage real estate owned							255,495	125,715
Reclassification of other assets and liabilities to self-storage real estate owned							1,074	0
Other loans paid off with issuance of development property investments							0	404
Contingent consideration for Internalization							8,554	0
Property Acquisition [Member]
Supplemental disclosure of non-cash investing and financing activities:
OC Units issued for Internalization	1,285	5,157	1,536
Internalization Expenses [Member]
Supplemental disclosure of non-cash investing and financing activities:
OC Units issued for Internalization			42,092
Non-Controlling Interests [Member] | Property Acquisition [Member]
Supplemental disclosure of non-cash investing and financing activities:
OC Units issued for self-storage real estate owned acquisitions							7,978	0
OC Units issued for Internalization	$ 1,285	$ 5,157	1,536
Non-Controlling Interests [Member] | Internalization Expenses [Member]
Supplemental disclosure of non-cash investing and financing activities:
OC Units issued for Internalization			$ 33,538				$ 33,538	$ 0