STOCKHOLDERS' EQUITY - Preferred Stock Outstanding (Details) - $ / shares	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Class of Stock [Line Items]
Number of shares issued (in shares)	1,600,000	850,000
Redemption period	90 days
Redemption price per share (in dollars per share)	$ 1,000
Series A Preferred Stock
Class of Stock [Line Items]
Number of shares issued (in shares)	250,000	250,000
Preferred stock, dividend rate	5.50%
Series B Preferred Stock
Class of Stock [Line Items]
Number of shares issued (in shares)	300,000	300,000
Preferred stock, dividend rate	6.00%
Series C Preferred Stock
Class of Stock [Line Items]
Number of shares issued (in shares)	300,000	300,000
Preferred stock, dividend rate	6.375%
Series D Preferred Stock
Class of Stock [Line Items]
Number of shares issued (in shares)	300,000	0
Preferred stock, dividend rate	6.35%
Depositary shares issued (in shares)	12,000,000
Depository share interest percentage	2.50%
Series E Preferred Stock
Class of Stock [Line Items]
Number of shares issued (in shares)	450,000	0
Preferred stock, dividend rate	5.00%
Depositary shares issued (in shares)	18,000,000
Depository share interest percentage	2.50%
LIBOR | Series A Preferred Stock
Class of Stock [Line Items]
Preferred stock, dividend payment rate	3.96%
LIBOR | Series B Preferred Stock
Class of Stock [Line Items]
Preferred stock, dividend payment rate	3.003%
LIBOR | Series C Preferred Stock
Class of Stock [Line Items]
Preferred stock, dividend payment rate	3.157%
LIBOR | Series D Preferred Stock
Class of Stock [Line Items]
Preferred stock, dividend payment rate	3.642%