STOCKHOLDERS' EQUITY - Dividends (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Class of Stock [Line Items]
Dividends declared per share of common stock (in usd per share)	$ 1.36	$ 0.98	$ 0.64
Common stock dividends declared and paid	$ 617	$ 471	$ 322
Preferred stock dividends declared and paid	73	29	14
Dividends Declared
Class of Stock [Line Items]
Common stock dividends declared and paid	617	471	322
Preferred stock dividends declared and paid	73	29	14
Dividends Paid
Class of Stock [Line Items]
Common stock dividends declared and paid	617	471	322
Preferred stock dividends declared and paid	$ 65	$ 14	$ 14
Series A Preferred Stock
Class of Stock [Line Items]
Dividends declared per share of preferred stock (in usd per share)	$ 55.00	$ 55.00	$ 55.00
Series A Preferred Stock | Dividends Declared
Class of Stock [Line Items]
Preferred stock dividends declared and paid	$ 14	$ 14	$ 14
Series A Preferred Stock | Dividends Paid
Class of Stock [Line Items]
Preferred stock dividends declared and paid	$ 14	$ 14	$ 14
Series B Preferred Stock
Class of Stock [Line Items]
Dividends declared per share of preferred stock (in usd per share)	$ 60.00	$ 37.00	$ 0
Series B Preferred Stock | Dividends Declared
Class of Stock [Line Items]
Preferred stock dividends declared and paid	$ 18	$ 11	$ 0
Series B Preferred Stock | Dividends Paid
Class of Stock [Line Items]
Preferred stock dividends declared and paid	$ 20	$ 0	$ 0
Series C Preferred Stock
Class of Stock [Line Items]
Dividends declared per share of preferred stock (in usd per share)	$ 63.75	$ 12.57	$ 0
Series C Preferred Stock | Dividends Declared
Class of Stock [Line Items]
Preferred stock dividends declared and paid	$ 19	$ 4	$ 0
Series C Preferred Stock | Dividends Paid
Class of Stock [Line Items]
Preferred stock dividends declared and paid	$ 18	$ 0	$ 0
Series D Preferred Stock
Class of Stock [Line Items]
Dividends declared per share of preferred stock (in usd per share)	$ 59.45	$ 0	$ 0
Series D Preferred Stock | Dividends Declared
Class of Stock [Line Items]
Preferred stock dividends declared and paid	$ 18	$ 0	$ 0
Series D Preferred Stock | Dividends Paid
Class of Stock [Line Items]
Preferred stock dividends declared and paid	$ 13	$ 0	$ 0
Series E Preferred Stock
Class of Stock [Line Items]
Dividends declared per share of preferred stock (in usd per share)	$ 9.44	$ 0	$ 0
Series E Preferred Stock | Dividends Declared
Class of Stock [Line Items]
Preferred stock dividends declared and paid	$ 4	$ 0	$ 0
Series E Preferred Stock | Dividends Paid
Class of Stock [Line Items]
Preferred stock dividends declared and paid	$ 0	$ 0	$ 0