FAIR VALUE OF FINANCIAL INSTRUMENTS - Schedule of Quantitative Information (Details) - Discounted Cash Flow - Level 3 - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Carrying Value	$ 2,100,947	$ 2,407,217
CMBS
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Carrying Value	$ 1,701,395	$ 1,991,506
CMBS | Minimum
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Yield (as a percent)	1.35%	0.00%
Duration (in years)	0 days	0 years
CMBS | Weighted Average
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Yield (as a percent)	2.87%	2.19%
Duration (in years)	3 years 6 months 18 days	4 years 21 days
CMBS | Maximum
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Yield (as a percent)	9.18%	9.21%
Duration (in years)	9 years 3 days	7 years 10 months 28 days
CMBS interest-only
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Carrying Value	$ 342,171	$ 344,423
CMBS interest-only | Minimum
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Yield (as a percent)	2.84%	0.09%
Duration (in years)	0 years	1 year 10 months 24 days
Prepayment speed	100.00	100.00
CMBS interest-only | Weighted Average
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Yield (as a percent)	4.04%	4.13%
Duration (in years)	2 years 11 months 26 days	3 years 3 months 18 days
Prepayment speed	100.00	100.00
CMBS interest-only | Maximum
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Yield (as a percent)	4.80%	4.51%
Duration (in years)	4 years 4 months 13 days	4 years 2 months 26 days
Prepayment speed	100.00	100.00
GNMA interest-only
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Carrying Value	$ 16,821	$ 26,194
GNMA interest-only | Minimum
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Yield (as a percent)	0.87%	0.00%
Duration (in years)	1 year 8 months 8 days	9 days
Prepayment speed	5.00	5.00
GNMA interest-only | Weighted Average
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Yield (as a percent)	7.22%	9.21%
Duration (in years)	4 years 5 months 8 days	2 years 4 months 28 days
Prepayment speed	13.80	14.57
GNMA interest-only | Maximum
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Yield (as a percent)	48.64%	10.00%
Duration (in years)	20 years 7 months 28 days	5 years 2 months 4 days
Prepayment speed	35.00	35.00
Agency securities
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Carrying Value	$ 780	$ 28,639
Agency securities | Minimum
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Yield (as a percent)	1.40%	0.58%
Duration (in years)	2 years 7 months 9 days	0 years
Agency securities | Weighted Average
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Yield (as a percent)	2.17%	3.47%
Duration (in years)	3 years 3 months 7 days	10 years 4 months 2 days
Agency securities | Maximum
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Yield (as a percent)	2.63%	3.51%
Duration (in years)	4 years 4 months 20 days	10 years 5 months 23 days
GNMA permanent securities
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Carrying Value	$ 39,780	$ 16,455
GNMA permanent securities | Minimum
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Yield (as a percent)	2.63%	0.00%
Duration (in years)	1 year 11 months 1 day	1 year 7 months 28 days
GNMA permanent securities | Weighted Average
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Yield (as a percent)	3.65%	3.25%
Duration (in years)	10 years 3 months 18 days	5 years 8 months 19 days
GNMA permanent securities | Maximum
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Yield (as a percent)	6.92%	6.62%
Duration (in years)	15 years 7 months 28 days	7 years 2 months 15 days