COMMON STOCK AND PREFERRED STOCK - Summary of Dividend Distribution Activity (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018		Jun. 30, 2017
Dividends Payable [Line Items]
Distributions declared to common stockholders			$ 697,197		$ 611,400
Distributions declared per common share (in dollars per share)	$ 0.3	$ 0.3	$ 0.6		$ 0.60
Distributions paid to common stockholders after period end			$ 349,300		$ 305,709
Distributions paid per common share after period end (in dollars per share)			$ 0.3		$ 0.0003
7.875% Series A Cumulative Redeemable Preferred Stock
Dividends Payable [Line Items]
Preferred dividends declared			$ 0		$ 7,296
Preferred series dividends declared, per share (in dollars per share)			$ 0		$ 0.984
7.625% Series C Cumulative Redeemable Preferred Stock
Dividends Payable [Line Items]
Preferred dividends declared			$ 7,652	[1]	$ 11,438
Preferred series dividends declared, per share (in dollars per share)			$ 0.953		$ 0.953
7.50% Series D Cumulative Redeemable Preferred Stock
Dividends Payable [Line Items]
Preferred dividends declared			$ 17,250		$ 17,250
Preferred series dividends declared, per share (in dollars per share)			$ 0.938		$ 0.938
7.625% Series E Cumulative Redeemable Preferred Stock
Dividends Payable [Line Items]
Preferred dividends declared			$ 2,253		$ 10,962
Preferred series dividends declared, per share (in dollars per share)			$ 0.196		$ 0.953
6.95% Series F Cumulative Redeemable Preferred Stock
Dividends Payable [Line Items]
Preferred dividends declared			$ 25,020		$ 0
Preferred series dividends declared, per share (in dollars per share)			$ 0.869		$ 0
6.50% Series G Cumulative Redeemable Preferred Stock
Dividends Payable [Line Items]
Preferred dividends declared			$ 12,968		$ 0
Preferred series dividends declared, per share (in dollars per share)			$ 0.763		$ 0

[1] Represents dividends declared per share for shares outstanding at June 30, 2018.