FAIR VALUE OF FINANCIAL INSTRUMENTS - Schedule of Quantitative Information (Details) - Discounted Cash Flow - Level 3 - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Carrying Value	$ 2,407,217	$ 2,683,745
CMBS
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Carrying Value	$ 1,991,506	$ 2,305,410
CMBS | Minimum
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Yield (as a percent)	0.00%	(13.06%)
Duration (in years)	0 years	0 years
CMBS | Weighted Average
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Yield (as a percent)	2.19%	2.36%
Duration (in years)	4 years 21 days	4 years 8 months 4 days
CMBS | Maximum
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Yield (as a percent)	9.21%	5.49%
Duration (in years)	7 years 10 months 27 days	8 years 3 months 3 days
CMBS interest-only
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Carrying Value	$ 344,423	$ 378,335
CMBS interest-only | Minimum
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Yield (as a percent)	0.09%	(27.49%)
Duration (in years)	1 year 10 months 24 days	5 months 26 days
Prepayment speed (as a percent)	100.00%	100.00%
CMBS interest-only | Weighted Average
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Yield (as a percent)	4.13%	(4.93%)
Duration (in years)	3 years 3 months 18 days	3 years 6 months
Prepayment speed (as a percent)	100.00%	100.00%
CMBS interest-only | Maximum
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Yield (as a percent)	4.51%	23.32%
Duration (in years)	4 years 2 months 26 days	4 years 8 months 23 days
Prepayment speed (as a percent)	100.00%	100.00%
GNMA interest-only
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Carrying Value	$ 26,194
GNMA interest-only | Minimum
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Yield (as a percent)	0.00%
Duration (in years)	3 months 25 days
Prepayment speed (as a percent)	5.00%
GNMA interest-only | Weighted Average
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Yield (as a percent)	9.21%
Duration (in years)	2 years 4 months 27 days
Prepayment speed (as a percent)	15.00%
GNMA interest-only | Maximum
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Yield (as a percent)	10.00%
Duration (in years)	5 years 2 months 4 days
Prepayment speed (as a percent)	35.00%
GN construction securities
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Carrying Value	$ 28,639
GN construction securities | Minimum
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Yield (as a percent)	0.58%
Duration (in years)	0 years
GN 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
GN 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
GN permanent securities
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Carrying Value	$ 16,455
GN permanent securities | Minimum
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Yield (as a percent)	0.00%
Duration (in years)	1 year 7 months 27 days
GN permanent securities | Weighted Average
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Yield (as a percent)	3.25%
Duration (in years)	5 years 8 months 19 days
GN permanent securities | Maximum
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Yield (as a percent)	6.62%
Duration (in years)	7 years 2 months 15 days