EQUITY - Additional Information (Details) $ / shares in Units, $ in Thousands			12 Months Ended
	Mar. 20, 2018 USD ($) $ / shares shares	May 25, 2017 USD ($) shares	Dec. 31, 2019 USD ($) Vote $ / shares shares	Dec. 31, 2018 USD ($) $ / shares shares	Dec. 31, 2017 USD ($)
Class of Stock [Line Items]
Common stock, shares authorized			500,000,000	500,000,000
Common stock, par value (in dollars per share) | $ / shares			$ 0.01	$ 0.01
Number of votes a share of outstanding common stock is entitled | Vote			1
Aggregate offering price | $		$ 200,000
Number of common stock sold (in shares)		6,151,514
Net proceeds from sale of stock | $		$ 89,100
Shares reserved for issuance			14,365,537	14,591,213
Preferred stock, shares authorized			100,000,000	100,000,000
Preferred stock, par value (in dollars per share) | $ / shares			$ 0.01	$ 0.01
Premium on redemption of preferred stock | $			$ 0	$ 3,277	$ 2,572
General partner, ownership interest			51.00%
Undesignated preferred stock
Class of Stock [Line Items]
Preferred stock, shares authorized			90,600,000
6.45% Series D Preferred Stock
Class of Stock [Line Items]
Preferred stock, shares authorized			3,000,000
Preferred stock, dividend rate (as a percent)			6.45%	6.45%
Preferred stock, shares outstanding			3,000,000	3,000,000
Preferred stock, redemption price (in dollars per share) | $ / shares			$ 25
Annual dividend rate per share (in dollars per share) | $ / shares			$ 1.6125
6.45% Series D Preferred Stock | Maximum
Class of Stock [Line Items]
Ratio for conversion			3.9216
6.25% Series E Preferred Stock
Class of Stock [Line Items]
Preferred stock, shares authorized			6,400,000
Preferred stock, dividend rate (as a percent)			6.25%	6.25%
Preferred stock, shares outstanding			6,400,000	6,400,000
Preferred stock, redemption price (in dollars per share) | $ / shares			$ 25,000
Annual dividend rate per share (in dollars per share) | $ / shares			$ 1.5625
6.25% Series E Preferred Stock | Maximum
Class of Stock [Line Items]
Ratio for conversion			3.1686
7.125% Series C Preferred Stock
Class of Stock [Line Items]
Preferred stock, dividend rate (as a percent)	7.125%
Payments for repurchase of redeemable preferred shares | $	$ 85,300
Preferred stock, shares outstanding	3,400,000
Preferred stock, redemption price (in dollars per share) | $ / shares	$ 25
Premium on redemption of preferred stock | $	$ 3,300
9.25% Series A Preferred Stock
Class of Stock [Line Items]
Preferred stock, redemption price (in dollars per share) | $ / shares			$ 25
GIC
Class of Stock [Line Items]
Limited partner, ownership percentage			49.00%
Unaffiliated Third Parties | Operating partnership
Class of Stock [Line Items]
Limited partner capital account units conversion ratio			1
Number of common units of operating partnership owned by unaffiliated third parties (in shares)			209,021	259,265
Limited partner, ownership percentage			1.00%	1.00%