REAL ESTATE SECURITIES - Securities by Remaining Maturity (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Schedule of Available-for-sale Securities [Line Items]
Within 1 year	$ 143,918	$ 612,752
1-5 years	1,508,191	1,260,381
5-10 years	441,038	533,604
After 10 years	7,800	480
Fair value of real estate securities	2,100,947	2,407,217
Other than temporary impairments included in consolidated statements of income	(4,700)	(1,600)	$ (3,900)
CMBS
Schedule of Available-for-sale Securities [Line Items]
Within 1 year	132,730	610,526
1-5 years	1,156,026	891,752
5-10 years	412,639	489,228
After 10 years	0	0
Fair value of real estate securities	1,701,395	1,991,506
CMBS interest-only
Schedule of Available-for-sale Securities [Line Items]
Within 1 year	11,188	0
1-5 years	330,983	344,423
5-10 years	0	0
After 10 years	0	0
Fair value of real estate securities	342,171	344,423
GNMA interest-only
Schedule of Available-for-sale Securities [Line Items]
Within 1 year	0	6
1-5 years	15,914	17,159
5-10 years	724	8,549
After 10 years	183	480
Fair value of real estate securities	16,821	26,194
Agency securities
Schedule of Available-for-sale Securities [Line Items]
Within 1 year	0
1-5 years	780
5-10 years	0
After 10 years	0
Fair value of real estate securities	780
GNMA construction securities
Schedule of Available-for-sale Securities [Line Items]
Within 1 year		0
1-5 years		386
5-10 years		28,253
After 10 years		0
Fair value of real estate securities		28,639
GNMA permanent securities
Schedule of Available-for-sale Securities [Line Items]
Within 1 year	0	2,220
1-5 years	4,488	6,661
5-10 years	27,675	7,574
After 10 years	7,617	0
Fair value of real estate securities	$ 39,780	$ 16,455

Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 25
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=65884222&loc=d3e22054-111558

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 5
-Subparagraph (aa)
-URI http://asc.fasb.org/extlink&oid=73527792&loc=d3e27232-111563

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=66010992&loc=d3e26610-111562

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+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=73527792&loc=d3e27161-111563

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