MORTGAGE SERVICING RIGHTS (Details) (USD $)	3 Months Ended	12 Months Ended
Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2014
Data and assumptions used in fair value calculation [Abstract]
Unpaid principal balance	$ 5,705,638,000us-gaap_ServicingAssetAtAmortizedValue	$ 5,568,829,000us-gaap_ServicingAssetAtAmortizedValue	$ 5,686,756,000us-gaap_ServicingAssetAtAmortizedValue
Weighted-average prepayment speed (CPR)	12.40%	10.90%	11.60%
Discount rate (annual percentage) (in hundredths)	9.80%	10.30%	9.80%
Weighted-average coupon interest rate (percentage) (in hundredths)	4.10%	4.20%	4.10%
Weighted-average remaining maturity (months)	315 months	312 months	314 months
Weighted-average servicing fee (basis points)	0.265%	0.266%	0.265%
Activity in mortgage servicing asset [Roll Forward]
Fair value as of beginning of period	51,296,000us-gaap_ServicingAssetAtFairValueAmount	54,662,000us-gaap_ServicingAssetAtFairValueAmount	54,662,000us-gaap_ServicingAssetAtFairValueAmount
Additions [Abstract]
Origination of servicing assets	2,499,000	1,460,000
Changes in fair value [Abstract]
Due to payoffs/paydowns	(1,564,000)	(1,138,000)
Due to change in valuation inputs or assumptions used in the valuation model	(3,039,000)	(1,547,000)
Other changes in fair value	(2,000)	(1,000)
Fair value as of end of period	49,190,000us-gaap_ServicingAssetAtFairValueAmount	53,436,000us-gaap_ServicingAssetAtFairValueAmount	51,296,000us-gaap_ServicingAssetAtFairValueAmount
Contractually specified servicing fees, late fees, and ancillary fees [Abstract]
Contractual servicing fees	3,900,000	3,700,000
Late and other ancillary fees	$ 348,000	$ 334,000

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All amounts that are due to the servicer of a financial asset as a result of the debt holder not meeting the monthly payment terms, and all other amounts due to the servicer, excluding contractually specified servicing fees and late fees.

+ References

No definition available.

+ Details

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- Definition

The weighted-average coupon interest rate, which may be one of the factors applied in estimating the fair value of servicing assets.

+ References

No definition available.

+ Details

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- Definition

The weighted-average servicing fee, which may be one of the factors applied in estimating the fair value of servicing assets.

+ References

No definition available.

+ Details

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- Definition

All amounts that, per contract, are due to the servicer in exchange for servicing the financial asset and would no longer be received by a servicer if the beneficial owners of the serviced assets (or their trustees or agents) were to exercise their actual or potential authority under the contract to shift the servicing to another servicer. Depending on the servicing contract, those fees may include some or all of the difference between the interest rate collected on the asset being serviced and the rate to be paid to the beneficial owners of the asset.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 860

-SubTopic 50

-Section 50

-Paragraph 2

-Subparagraph (c)

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- Definition

Amortized amount of contract to service financial assets under which the benefits of servicing are expected to more than adequately compensate the servicer.

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-Publisher FASB

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- Definition

The value of new servicing assets, subsequently measured at fair value, acquired or created during the current period through purchases or from transfers of financial assets.

+ References

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 860

-SubTopic 50

-Section 50

-Paragraph 3

-Subparagraph (a)(2)

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- Definition

Fair value of an asset representing net future revenue from contractually specified servicing fees, late charges, and other ancillary revenues, in excess of future costs related to servicing arrangements.

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-Publisher FASB

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- Definition

The net Increase or Decrease in fair value as a result of changes in the inputs, assumptions, or model used to calculate the fair value of servicing assets.

+ References

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-Publisher FASB

-Name Accounting Standards Codification

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- Definition

The net Increase or Decrease in fair value as a result of other changes that are not additions, disposals, or a result of change in the inputs, assumptions, or model used to calculate the fair value of servicing assets.

+ References

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Other net Increase or Decrease in the balance in servicing assets subsequently measured at fair value. This element is for changes other than additions, disposals, changes in fair value resulting from changes in valuation inputs or changes in assumptions, or other changes in fair value.

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Discount rate used to estimate the fair value of servicing assets and servicing liabilities.

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- Definition

Estimated rate of prepayments of principal on servicing assets and servicing liabilities.

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- Definition

Weighted average life of financial assets and financial liabilities, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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