SIGNIFICANT ACCOUNTING POLICIES (Schedule of Consolidated Statements of Cash Flows - Supplemental Disclosures) (Details) - USD ($) $ in Thousands		6 Months Ended
	Feb. 20, 2018	Jun. 30, 2018	Jun. 30, 2017
Supplemental disclosure of cash flow information:
Interest paid		$ 743	$ 433
Supplemental disclosure of non-cash investing and financing activities:
Stock dividend paid on preferred stock		2,169	1,194
Dividends declared, but not paid, on preferred stock		4,580	177
Dividends declared, but not paid, on common stock		6,739	4,983
Reclassification of self-storage real estate owned		35,281	6,066
Assumed liabilities with acquisition of self-storage real estate owned	$ 1,258	1,258
Other loans paid off with issuance of development property investments		117	$ 1,410
Reclassification of deferred costs to cumulative preferred stock		$ 559