INCOME TAXES - Characterization of Distributions (Details) - $ / shares	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Common Stock
Class of Stock [Line Items]
Ordinary income (in dollars per share)	$ 0.0944	$ 0.6132	$ 0.7200
Ordinary income, percent	52.46%	85.16%	100.00%
Capital gain distributions (in dollars per share)	$ 0	$ 0.1068	$ 0
Capital gain distributions, percent	0.00%	14.84%	0.00%
Return of capital (in dollars per share)	$ 0.0856	$ 0	$ 0
Return of capital, percent	47.54%	0.00%	0.00%
Distribution per share (in dollars per share)	$ 0.1800	$ 0.7200	$ 0.7200
Distribution paid, percent	100.00%	100.00%	100.00%
Preferred Stock - Series C
Class of Stock [Line Items]
Ordinary income (in dollars per share)	$ 0	$ 0	$ 0.5393
Ordinary income, percent	0.00%	0.00%	100.00%
Distribution per share (in dollars per share)	$ 0	$ 0	$ 0.5393
Distribution paid, percent	0.00%	0.00%	100.00%
Preferred Stock - Series D
Class of Stock [Line Items]
Ordinary income (in dollars per share)	$ 0.4031	$ 1.3732	$ 1.6125
Ordinary income, percent	25.00%	85.16%	100.00%
Capital gain distributions (in dollars per share)	$ 0	$ 0.2393	$ 0
Capital gain distributions, percent	0.00%	14.84%	0.00%
Return of capital (in dollars per share)	$ 1.2094	$ 0	$ 0
Return of capital, percent	75.00%	0.00%	0.00%
Distribution per share (in dollars per share)	$ 1.6125	$ 1.6125	$ 1.6125
Distribution paid, percent	100.00%	100.00%	100.00%
Preferred Stock - Series E
Class of Stock [Line Items]
Ordinary income (in dollars per share)	$ 0.3906	$ 1.3307	$ 1.5625
Ordinary income, percent	25.00%	85.16%	100.00%
Capital gain distributions (in dollars per share)	$ 0	$ 0.2318	$ 0
Capital gain distributions, percent	0.00%	14.84%	0.00%
Return of capital (in dollars per share)	$ 1.1719	$ 0	$ 0
Return of capital, percent	75.00%	0.00%	0.00%
Distribution per share (in dollars per share)	$ 1.5625	$ 1.5625	$ 1.5625
Distribution paid, percent	100.00%	100.00%	100.00%