CAPITAL STOCK - Summary of Dividend Distribution Activity (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Dividends Payable [Line Items]
Distributions declared to common stockholders			$ 1,062,685	$ 937,825
Distributions declared per common share (in dollars per share)	$ 0.3	$ 0.3	$ 0.9	$ 0.9
Distributions paid to common stockholders after period end			$ 102,811	$ 326,425
Distributions paid per common share after period end (in dollars per share)			$ 0.08	$ 0.3
Series A Preferred Stock
Dividends Payable [Line Items]
Preferred dividends declared			$ 0	$ 9,527
Preferred series dividends declared, per share (in dollars per share)			$ 0	$ 1.477
Series C Preferred Stock
Dividends Payable [Line Items]
Preferred dividends declared			$ 10,987	$ 17,157
Preferred series dividends declared, per share (in dollars per share)			$ 1.43	$ 1.43
Series D Preferred Stock
Dividends Payable [Line Items]
Preferred dividends declared			$ 25,875	$ 25,875
Preferred series dividends declared, per share (in dollars per share)			$ 1.406	$ 1.406
Series E Preferred Stock
Dividends Payable [Line Items]
Preferred dividends declared			$ 2,253	$ 16,441
Preferred series dividends declared, per share (in dollars per share)			$ 0.196	$ 1.43
Series F Preferred Stock
Dividends Payable [Line Items]
Preferred dividends declared			$ 37,530	$ 0
Preferred series dividends declared, per share (in dollars per share)			$ 1.303	$ 0
Cumulative and undeclared dividends		$ 8,300		$ 8,300
Series G Preferred Stock
Dividends Payable [Line Items]
Preferred dividends declared			$ 19,875	$ 0
Preferred series dividends declared, per share (in dollars per share)			$ 1.169	$ 0
Series H Preferred Stock
Dividends Payable [Line Items]
Preferred dividends declared			$ 298	$ 0
Preferred series dividends declared, per share (in dollars per share)			$ 0.135	$ 0