DISCLOSURES REGARDING FAIR VALUES OF FINANCIAL INSTRUMENTS - Financial Instruments Other than Debt Securities (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Financial assets [Abstract]
Residential mortgage loans	$ 13,605,583	$ 13,316,282
Carrying Amount [Member]
Financial assets [Abstract]
Residential mortgage loans	2,183	2,584
Lending counterparty investments	5,002	5,002
Financial liabilities [Abstract]
Secured borrowings with initial terms of greater than 120 days	33,073	139,101
Unsecured borrowings	98,166	98,090
Fair Value [Member]
Financial assets [Abstract]
Residential mortgage loans	2,200	2,600
Lending counterparty investments	5,002	5,002
Financial liabilities [Abstract]
Secured borrowings with initial terms of greater than 120 days	33,100	139,100
Unsecured borrowings	71,600	68,800
Interest Rate Swap Agreements [Member] \| Carrying Amount [Member] \| Secured Borrowings [Member]
Financial assets [Abstract]
Secured borrowings-related interest rate swap agreements	2,022	24,709
Financial liabilities [Abstract]
Interest rate swap agreements		222
Interest Rate Swap Agreements [Member] \| Carrying Amount [Member] \| Unsecured Borrowings-Related [Member]
Financial liabilities [Abstract]
Interest rate swap agreements	24,759	24,195
Interest Rate Swap Agreements [Member] \| Fair Value [Member] \| Secured Borrowings [Member]
Financial assets [Abstract]
Secured borrowings-related interest rate swap agreements	2,022	24,709
Financial liabilities [Abstract]
Interest rate swap agreements		222
Interest Rate Swap Agreements [Member] \| Fair Value [Member] \| Unsecured Borrowings-Related [Member]
Financial liabilities [Abstract]
Interest rate swap agreements	$ 24,759	$ 24,195

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

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, after the effects of master netting arrangements, of a 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. Includes assets not subject to a master netting arrangement and not elected to be offset.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 20
-Section 50
-Paragraph 3
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=51824906&loc=SL20225862-175312

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
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-Section 45
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-Publisher FASB
-Name Accounting Standards Codification
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-Section 55
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- Definition

Fair value, after the effects of master netting arrangements, of a financial liability or 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 liabilities not subject to a master netting arrangement and not elected to be offset.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 20
-Section 55
-Paragraph 10
-URI http://asc.fasb.org/extlink&oid=82849420&loc=SL20226008-175313

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-Publisher FASB
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-Publisher FASB
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- 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

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 940
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- References

No definition available.

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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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