STOCKHOLDERS' EQUITY - Schedule of Series E Preferred Stock Issued Prices and Proceeds Presented Net of Underwriting Fees and Other Costs (Details) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Class of Stock [Line Items]
Net Proceeds	$ 52,051,000	$ 1,898,000	$ 13,266,000
Continuous Offering Program [Member] | Cumulative Redeemable Preferred Stock, Series E [Member]
Class of Stock [Line Items]
Shares	2,095,000	78,000	538,000
Net Issue Price	$ 24.77	$ 24.23	$ 24.61
Net Proceeds	$ 51,887,000	$ 1,887,000	$ 13,236,000