BORROWINGS - Types of Repurchase Agreements (Details) - USD ($)	Mar. 31, 2018	Dec. 31, 2017
Repurchase Agreements
Amount outstanding	$ 1,177,060,000	$ 1,234,522,000
Weighted average interest rate, percentage	1.88%	1.56%
Market value of collateral held	$ 1,237,603,856	$ 1,295,225,428
Agency
Repurchase Agreements
Amount outstanding	$ 1,174,281,000	$ 1,228,349,000
Weighted average interest rate, percentage	1.87%	1.55%
Market value of collateral held	$ 1,233,451,363	$ 1,285,083,649
Non-Agency
Repurchase Agreements
Amount outstanding	$ 2,779,000	$ 2,555,000
Weighted average interest rate, percentage	3.95%	3.38%
Market value of collateral held	$ 4,152,493	$ 4,399,779
Multi-Family
Repurchase Agreements
Amount outstanding	$ 0	$ 3,618,000
Weighted average interest rate, percentage	0.00%	3.16%
Market value of collateral held	$ 0	$ 5,742,000

This is the weighted average interest rate during the reporting period as a result of repurchase agreements.

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- Definition

Fair value of collateral permitted, by contact or custom, to be sold or re-pledged.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 30
-Section 50
-Paragraph 1A
-Subparagraph (c)(1)
-URI http://asc.fasb.org/extlink&oid=64858031&loc=SL6224234-111729

+ Details

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- Definition

Carrying value, as of the balance sheet date, of securities sold under agreements to repurchase where the transferor maintains effective control over the assets, accounting for them as secured debt.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08.(m)(1)(i))
-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 10
-Section 55
-Paragraph 51
-URI http://asc.fasb.org/extlink&oid=77903054&loc=d3e101761-111710

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- References

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