EQUITY - Narrative (Details) $ / shares in Units, $ in Thousands			6 Months Ended	12 Months Ended
	Jun. 30, 2016 USD ($) $ / shares shares	Jun. 28, 2016 USD ($) shares	Jun. 30, 2016 USD ($) $ / shares shares	Dec. 31, 2015 $ / shares shares	Aug. 02, 2016
Class of Stock [Line Items]
Common stock, shares authorized | shares	500,000,000		500,000,000	500,000,000
Common stock, par value (in dollars per share)	$ 0.01		$ 0.01	$ 0.01
Preferred stock, shares authorized | shares	100,000,000		100,000,000	100,000,000
Preferred stock, par value (in dollars per share)	$ 0.01		$ 0.01	$ 0.01
Net proceeds from sale of preferred stock | $			$ 72,337
Undesignated preferred stock
Class of Stock [Line Items]
Preferred stock, shares authorized | shares	88,600,000		88,600,000
9.25% Series A Preferred Stock
Class of Stock [Line Items]
Preferred stock, shares authorized | shares	2,000,000		2,000,000
Preferred stock, dividend rate (as a percent)			9.25%	9.25%
Preferred stock, liquidation preference (in dollars per share)	$ 25		$ 25
Annual dividend rate per share (in dollars per share)			$ 2.3125
9.25% Series A Preferred Stock | Maximum
Class of Stock [Line Items]
Ratio for conversion			5.92417
7.875% Series B Preferred Stock
Class of Stock [Line Items]
Preferred stock, shares authorized | shares	3,000,000		3,000,000
Preferred stock, dividend rate (as a percent)			7.875%	7.875%
Preferred stock, liquidation preference (in dollars per share)	$ 25		$ 25
Annual dividend rate per share (in dollars per share)			$ 1.96875
7.875% Series B Preferred Stock | Maximum
Class of Stock [Line Items]
Ratio for conversion			5.6497
7.125% Series C Preferred Stock
Class of Stock [Line Items]
Preferred stock, shares authorized | shares	3,400,000		3,400,000
Preferred stock, dividend rate (as a percent)			7.125%	7.125%
Preferred stock, liquidation preference (in dollars per share)	$ 25		$ 25
Annual dividend rate per share (in dollars per share)			$ 1.78125
7.125% Series C Preferred Stock | Maximum
Class of Stock [Line Items]
Ratio for conversion			5.1440
6.450% Series D Preferred Stock
Class of Stock [Line Items]
Preferred stock, shares authorized | shares	3,000,000		3,000,000
Preferred stock, dividend rate (as a percent)			6.45%
Net proceeds from sale of preferred stock (in shares) | shares		3,000,000
Net proceeds from sale of preferred stock | $		$ 72,300
Underwriting discount and offering-related expenses | $		$ 2,700
Preferred stock, liquidation preference (in dollars per share)	$ 25		$ 25
Annual dividend rate per share (in dollars per share)			$ 1.6125
6.450% Series D Preferred Stock | Maximum
Class of Stock [Line Items]
Ratio for conversion			3.9216
Operating partnership | Non-controlling Interests in Operating Partnership
Class of Stock [Line Items]
Number of common units of operating partnership owned by unaffiliated third parties | shares	462,385		462,385	516,021
Percentage of limited partnership interest in operating partnership			1.00%	1.00%
Leasehold Venture
Class of Stock [Line Items]
Payments to acquire interest in joint venture | $	$ 400
Leasehold Venture | Subsequent Event
Class of Stock [Line Items]
Ownership interest in joint venture (as a percent)					100.00%