STOCKHOLDERS' EQUITY - Dividends (Details) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Class of Stock [Line Items]
Common stock, dividends per share (in dollars per share)	$ 0.98	$ 0.64	$ 0.46
Common stock dividends	471,000,000	322,000,000	241,000,000
Preferred stock dividends	29,000,000	14,000,000	14,000,000
Dividends Declared
Class of Stock [Line Items]
Common stock dividends	471,000,000	322,000,000	241,000,000
Preferred stock dividends	29,000,000	14,000,000	14,000,000
Dividends Paid
Class of Stock [Line Items]
Common stock dividends	471,000,000	322,000,000	241,000,000
Preferred stock dividends	14,000,000	14,000,000	14,000,000
Series A
Class of Stock [Line Items]
Preferred stock, dividends per share (in dollars per share)	55.00	55.00	55.00
Preferred stock dividends	14,000,000	14,000,000
Series A | Dividends Declared
Class of Stock [Line Items]
Preferred stock dividends	14,000,000	14,000,000	14,000,000
Series A | Dividends Paid
Class of Stock [Line Items]
Preferred stock dividends	14,000,000	14,000,000	14,000,000
Series B
Class of Stock [Line Items]
Preferred stock, dividends per share (in dollars per share)	37.00	0.00	0.00
Preferred stock dividends	11,000,000
Series B | Dividends Declared
Class of Stock [Line Items]
Preferred stock dividends	11,000,000	0	0
Series B | Dividends Paid
Class of Stock [Line Items]
Preferred stock dividends	0	0	0
Series C
Class of Stock [Line Items]
Preferred stock, dividends per share (in dollars per share)	12.57	0.00	0.00
Preferred stock dividends	4,000,000
Series C | Dividends Declared
Class of Stock [Line Items]
Preferred stock dividends	4,000,000	0	0
Series C | Dividends Paid
Class of Stock [Line Items]
Preferred stock dividends	$ 0	$ 0	$ 0