STOCKHOLDERS' EQUITY - Dividends (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Class of Stock [Line Items]
Dividends declared per share of common stock (in usd per share)	$ 0.39	$ 0.32
Common stock dividends declared and paid	$ 168	$ 149
Preferred stock dividends declared and paid	$ 22	$ 15
Series A Preferred Stock
Class of Stock [Line Items]
Dividends declared per share of preferred stock (in usd per share)	$ 27.50	$ 27.50
Series B Preferred Stock
Class of Stock [Line Items]
Dividends declared per share of preferred stock (in usd per share)	0	0
Series C Preferred Stock
Class of Stock [Line Items]
Dividends declared per share of preferred stock (in usd per share)	15.94	15.94
Series D Preferred Stock
Class of Stock [Line Items]
Dividends declared per share of preferred stock (in usd per share)	15.88	11.82
Series E Preferred Stock
Class of Stock [Line Items]
Dividends declared per share of preferred stock (in usd per share)	$ 12.50	$ 0
Dividends Declared
Class of Stock [Line Items]
Common stock dividends declared and paid	$ 168	$ 149
Preferred stock dividends declared and paid	22	15
Dividends Declared | Series A Preferred Stock
Class of Stock [Line Items]
Preferred stock dividends declared and paid	7	7
Dividends Declared | Series B Preferred Stock
Class of Stock [Line Items]
Preferred stock dividends declared and paid	0	0
Dividends Declared | Series C Preferred Stock
Class of Stock [Line Items]
Preferred stock dividends declared and paid	5	5
Dividends Declared | Series D Preferred Stock
Class of Stock [Line Items]
Preferred stock dividends declared and paid	5	3
Dividends Declared | Series E Preferred Stock
Class of Stock [Line Items]
Preferred stock dividends declared and paid	5	0
Dividends Paid
Class of Stock [Line Items]
Common stock dividends declared and paid	168	149
Preferred stock dividends declared and paid	23	15
Dividends Paid | Series A Preferred Stock
Class of Stock [Line Items]
Preferred stock dividends declared and paid	0	0
Dividends Paid | Series B Preferred Stock
Class of Stock [Line Items]
Preferred stock dividends declared and paid	9	11
Dividends Paid | Series C Preferred Stock
Class of Stock [Line Items]
Preferred stock dividends declared and paid	5	4
Dividends Paid | Series D Preferred Stock
Class of Stock [Line Items]
Preferred stock dividends declared and paid	5	0
Dividends Paid | Series E Preferred Stock
Class of Stock [Line Items]
Preferred stock dividends declared and paid	$ 4	$ 0