STOCKHOLDERS' EQUITY - Dividends (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Class of Stock [Line Items]
Dividends declared per share of common stock (in usd per share)	$ 0.39	$ 0.36	$ 1.17	$ 1.00
Common stock dividends declared and paid	$ 168	$ 162	$ 504	$ 459
Preferred stock dividends declared and paid	$ 25	$ 17	$ 75	$ 50
Series A Preferred Stock
Class of Stock [Line Items]
Dividends declared per share of preferred stock (in usd per share)	$ 10.90	$ 27.50	$ 51.88	$ 55.00
Series B Preferred Stock
Class of Stock [Line Items]
Dividends declared per share of preferred stock (in usd per share)	0	0	30.00	30.00
Series C Preferred Stock
Class of Stock [Line Items]
Dividends declared per share of preferred stock (in usd per share)	15.94	15.94	47.81	47.81
Series D Preferred Stock
Class of Stock [Line Items]
Dividends declared per share of preferred stock (in usd per share)	15.88	15.88	47.63	43.57
Series E Preferred Stock
Class of Stock [Line Items]
Dividends declared per share of preferred stock (in usd per share)	12.50	0	37.50	0
Series F Preferred Stock
Class of Stock [Line Items]
Dividends declared per share of preferred stock (in usd per share)	$ 19.15	$ 0	$ 19.15	$ 0
Dividends Declared
Class of Stock [Line Items]
Common stock dividends declared and paid	$ 168	$ 162	$ 504	$ 459
Preferred stock dividends declared and paid	25	17	75	50
Dividends Declared | Series A Preferred Stock
Class of Stock [Line Items]
Preferred stock dividends declared and paid	3	7	13	14
Dividends Declared | Series B Preferred Stock
Class of Stock [Line Items]
Preferred stock dividends declared and paid	0	0	9	9
Dividends Declared | Series C Preferred Stock
Class of Stock [Line Items]
Preferred stock dividends declared and paid	4	5	14	14
Dividends Declared | Series D Preferred Stock
Class of Stock [Line Items]
Preferred stock dividends declared and paid	4	5	14	13
Dividends Declared | Series E Preferred Stock
Class of Stock [Line Items]
Preferred stock dividends declared and paid	6	0	17	0
Dividends Declared | Series F Preferred Stock
Class of Stock [Line Items]
Preferred stock dividends declared and paid	8	0	8	0
Dividends Paid
Class of Stock [Line Items]
Common stock dividends declared and paid	168	162	504	459
Preferred stock dividends declared and paid	28	18	73	48
Dividends Paid | Series A Preferred Stock
Class of Stock [Line Items]
Preferred stock dividends declared and paid	3	0	10	7
Dividends Paid | Series B Preferred Stock
Class of Stock [Line Items]
Preferred stock dividends declared and paid	9	9	18	20
Dividends Paid | Series C Preferred Stock
Class of Stock [Line Items]
Preferred stock dividends declared and paid	5	4	15	13
Dividends Paid | Series D Preferred Stock
Class of Stock [Line Items]
Preferred stock dividends declared and paid	5	5	15	8
Dividends Paid | Series E Preferred Stock
Class of Stock [Line Items]
Preferred stock dividends declared and paid	6	0	15	0
Dividends Paid | Series F Preferred Stock
Class of Stock [Line Items]
Preferred stock dividends declared and paid	$ 0	$ 0	$ 0	$ 0