DISCLOSURES REGARDING FAIR VALUES OF FINANCIAL INSTRUMENTS - Balance Sheet Location (Details) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2016	Dec. 31, 2015
Financial assets [Abstract]
Residential mortgage loans	$ 13,835,131	$ 14,154,737
Carrying Amount [Member]
Financial assets [Abstract]
Residential mortgage loans	3,190	3,817
Lending counterparty investments	35,002	65,002
Portfolio-related interest rate swap agreements	802	7,720
Financial liabilities [Abstract]
Secured borrowings with initial terms of greater than 120 days	2,243,179	3,246,177
Unsecured borrowings	98,014	97,986
Interest rate swap agreements [Abstract]
Portfolio-related	11,296	1,051
Unsecured borrowings-related	35,013	25,010
Fair Value [Member]
Financial assets [Abstract]
Residential mortgage loans	3,200	3,900
Lending counterparty investments	35,002	65,002
Portfolio-related interest rate swap agreements	802	7,720
Financial liabilities [Abstract]
Secured borrowings with initial terms of greater than 120 days	2,243,800	3,245,000
Unsecured borrowings	73,100	77,200
Interest rate swap agreements [Abstract]
Portfolio-related	11,296	1,051
Unsecured borrowings-related	$ 35,013	$ 25,010
Maximum [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Repurchase arrangements with initial terms	120 days

Investments in FHLB stock and other junior notes receivable with lending counterparties.

No definition available.

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- Definition

Refers to the term of investment repurchase agreement.

+ References

No definition available.

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- Definition

Fair value of portfolio related liability associated with financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset.

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No definition available.

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- Definition

Fair value, before effects of master netting arrangements, of a portfolio related asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes assets elected not to be offset. Excludes assets not subject to a master netting arrangement.

+ References

No definition available.

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- Definition

Fair value portion of FHLB advances and securities that an entity sells and agrees to repurchase at a specified date for a specified price.

+ References

No definition available.

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- Definition

Fair value of unsecured borrowings liability associated with financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset.

+ References

No definition available.

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No definition available.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

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- Definition

The fair value as of the balance sheet date of firm holdings in mortgages, mortgage backed securities (investment instruments that represent ownership of an undivided interest in a group of mortgages, where principal and interest from the individual mortgages are used to pay investors' principal and interest on the mortgage backed security) and asset-backed securities that are primarily paid from the cash flows of a discrete pool of receivables or other financial assets (such as credit-card receivables), either fixed or revolving, that by their terms convert into cash within a finite time period. Includes both pledged (to counterparties as collateral for financing transactions) 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

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- Definition

The fair value amount of long-term debt whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission.

+ References

No definition available.

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