STOCKHOLDERS' EQUITY - Preferred Stock Outstanding (Details) - $ / shares	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Class of Stock [Line Items]
Number of shares issued (in shares)	850,000	250,000
Redemption period	90 days
Redemption price per share (in dollars per share)	$ 1,000
Series A
Class of Stock [Line Items]
Number of shares issued (in shares)	250,000	250,000
Preferred stock, dividend rate	5.50%
Series B
Class of Stock [Line Items]
Number of shares issued (in shares)	300,000
Preferred stock, dividend rate	6.00%
Series C
Class of Stock [Line Items]
Number of shares issued (in shares)	300,000
Preferred stock, dividend rate	6.375%
LIBOR | Series A
Class of Stock [Line Items]
Preferred stock, dividend payment rate	3.96%
LIBOR | Series B
Class of Stock [Line Items]
Preferred stock, dividend payment rate	3.003%
LIBOR | Series C
Class of Stock [Line Items]
Preferred stock, dividend payment rate	3.157%