INCOME TAXES - Schedule of Taxable Common Stock Distributions (Details) - $ / shares		1 Months Ended			3 Months Ended								12 Months Ended
	Dec. 16, 2019	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Dividends per share (in dollars per share)													$ 1.87	$ 1.60	$ 1.94
Ordinary Income													77.53%	78.03%	66.64%
Long-term Capital Gain													15.82%	1.03%	7.83%
Return of Capital													6.65%	20.94%	25.53%
Dividends declared per share of common stock (in dollars per share)	$ 0.50	$ 0.50	$ 0.50	$ 0.50	$ 0.50	$ 0.50	$ 0.50	$ 0.50	$ 0.50	$ 0.50	$ 0.50	$ 0.50	$ 2.00	$ 2.00	$ 1.98
Series A Preferred Stock
Dividends per share (in dollars per share)													$ 0.69
Ordinary Income													84.18%
Long-term Capital Gain													15.82%
Return of Capital													0.00%
Series B Preferred Stock
Dividends per share (in dollars per share)													$ 0.45
Ordinary Income													84.18%
Long-term Capital Gain													15.82%
Return of Capital													0.00%