FAIR VALUE OF FINANCIAL INSTRUMENTS - Schedule of Quantitative Information (Details) - Discounted Cash Flow - Level 3 $ in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2016 USD ($)	Dec. 31, 2015 USD ($)
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Carrying Value	$ 2,700,210	$ 2,407,217
CMBS
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Carrying Value	$ 2,302,280	$ 1,991,506
CMBS | Minimum
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Yield (as a percent)	0.00%	0.00%
Duration (in years)	0 years	0 years
CMBS | Weighted Average
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Yield (as a percent)	2.50%	2.19%
Duration (in years)	3 years 9 months 25 days	4 years 21 days
CMBS | Maximum
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Yield (as a percent)	13.16%	9.21%
Duration (in years)	9 years 3 months 14 days	7 years 10 months 27 days
CMBS interest-only
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Carrying Value	$ 334,613	$ 344,423
CMBS interest-only | Minimum
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Yield (as a percent)	0.00%	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)	3.74%	4.13%
Duration (in years)	3 years 2 months 4 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)	4.19%	4.51%
Duration (in years)	4 years 3 months 10 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	$ 20,833	$ 26,194
GNMA interest-only | Minimum
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Yield (as a percent)	(7.16%)	0.00%
Duration (in years)	0 years	3 months 25 days
Prepayment speed	5.00	5.00
GNMA interest-only | Weighted Average
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Yield (as a percent)	5.98%	9.21%
Duration (in years)	2 years 3 months 29 days	2 years 4 months 27 days
Prepayment speed	14.11	14.57
GNMA interest-only | Maximum
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Yield (as a percent)	36.33%	10.00%
Duration (in years)	5 years 5 months 19 days	5 years 2 months 4 days
Prepayment speed	35.00	35.00
GNMA construction securities
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Carrying Value		$ 28,639
GNMA construction securities | Minimum
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Yield (as a percent)		0.58%
Duration (in years)		0 years
GNMA construction securities | Weighted Average
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Yield (as a percent)		3.47%
Duration (in years)		10 years 4 months 2 days
GNMA construction securities | Maximum
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Yield (as a percent)		3.51%
Duration (in years)		10 years 5 months 23 days
GNMA permanent securities
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Carrying Value	$ 42,484	$ 16,455
GNMA permanent securities | Minimum
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Yield (as a percent)	1.40%	0.00%
Duration (in years)	0 years	1 year 7 months 27 days
GNMA permanent securities | Weighted Average
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Yield (as a percent)	3.69%	3.25%
Duration (in years)	8 years 7 months 9 days	5 years 8 months 19 days
GNMA permanent securities | Maximum
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Yield (as a percent)	6.77%	6.62%
Duration (in years)	10 years 2 months 26 days	7 years 2 months 15 days