MORTGAGE-BACKED SECURITIES - RMBS portfolio by contractual maturities (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Investments, Debt and Equity Securities [Abstract]
Greater than one year and less than five years	$ 15	$ 29
Greater than five years and less than ten years	3,049	3,281
Greater than or equal to ten years	3,742,720	3,741,501
Total mortgage-backed securities	$ 3,745,784	$ 3,744,811

Presentation of marketable securities with stated contractual maturities of five years through ten years.

No definition available.

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- Definition

Presentation of marketable securities with stated contractual maturities of one year through five years.

+ References

No definition available.

+ Details

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- Definition

Presentation of marketable securities with stated contractual maturities greater than ten years.

+ References

No definition available.

+ Details

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- Definition

The aggregate fair value as of the balance sheet date of financial instruments and other positions owned by the entity including: (1) mortgages, mortgage-backed and asset backed securities; (2) US government and agency obligations; (3) state and municipal government obligations; (4) other sovereign government debt; (5) corporate obligations; (6) corporate equities; (7) principal investments; (8) derivative contracts; and (9) physical commodities. Includes both pledged and unpledged holdings.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 940
-SubTopic 320
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=35711157&loc=d3e42546-110969

+ Details

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- References

No definition available.

+ Details

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