COMMON STOCK AND PREFERRED STOCK - Summary of Dividend Distribution Activity (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2018		Mar. 31, 2017
Dividends Payable [Line Items]
Distributions declared to common stockholders	$ 347,897		$ 305,691
Distributions declared per common share (in dollars per share)	$ 0.3		$ 0.30
Distributions paid to common stockholders after period end	$ 347,897		$ 305,691
Distributions paid per common share after period end (in dollars per share)	$ 0.3		$ 0.3
7.875% Series A Cumulative Redeemable Preferred Stock
Dividends Payable [Line Items]
Preferred dividends declared	$ 0		$ 3,648
Preferred series dividends declared, per share (in dollars per share)	$ 0		$ 0.492
7.625% Series C Cumulative Redeemable Preferred Stock
Dividends Payable [Line Items]
Preferred dividends declared	$ 4,316	[1]	$ 5,719
Preferred series dividends declared, per share (in dollars per share)	$ 0.477		$ 0.477
7.50% Series D Cumulative Redeemable Preferred Stock
Dividends Payable [Line Items]
Preferred dividends declared	$ 8,625		$ 8,625
Preferred series dividends declared, per share (in dollars per share)	$ 0.469		$ 0.469
7.625% Series E Cumulative Redeemable Preferred Stock
Dividends Payable [Line Items]
Preferred dividends declared	$ 2,253		$ 5,481
Preferred series dividends declared, per share (in dollars per share)	$ 0.196		$ 0.477
6.95% Series F Cumulative Redeemable Preferred Stock
Dividends Payable [Line Items]
Preferred dividends declared	$ 12,510		$ 0
Preferred series dividends declared, per share (in dollars per share)	$ 0.434		$ 0
6.50% Series G Cumulative Redeemable Preferred Stock
Dividends Payable [Line Items]
Preferred dividends declared	$ 6,062		$ 0
Preferred series dividends declared, per share (in dollars per share)	$ 0.357		$ 0

[1] Represents dividends declared per share for shares outstanding at March 31, 2018.