INVESTMENT SECURITIES - Significant Assumptions in Valuation of Private Label MBS (Detail)	3 Months Ended	12 Months Ended
Mar. 31, 2015	Dec. 31, 2014
Schedule Of Investments [Line Items]
Fair Value Inputs Discount Rate	14.50%us-gaap_FairValueInputsDiscountRate	14.50%us-gaap_FairValueInputsDiscountRate
Fair Value Inputs Prepayment Rate	31.56%us-gaap_FairValueInputsPrepaymentRate	32.00%us-gaap_FairValueInputsPrepaymentRate
Weighted Average, Projected Cumulative Loss Rate	7.30%us-gaap_FairValueInputsLossSeverity	7.90%us-gaap_FairValueInputsLossSeverity
Minimum [Member]
Schedule Of Investments [Line Items]
Fair Value Inputs Prepayment Rate	18.04%	19.89%
Weighted Average, Projected Cumulative Loss Rate	0.00%	0.64%
Maximum [Member]
Schedule Of Investments [Line Items]
Fair Value Inputs Prepayment Rate	100.00%	100.00%
Weighted Average, Projected Cumulative Loss Rate	80.00%	80.00%

Interest rate used to find the present value of an amount to be paid or received in the future as an input to measure fair value. For example, but not limited to, weighted average cost of capital (WACC), cost of capital, cost of equity and cost of debt.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 820

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (bbb)

-URI http://asc.fasb.org/extlink&oid=36462937&loc=d3e19207-110258

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- Definition

Loss, including interest and principal, incurred on a defaulted security, expressed as a percentage of the original principal balance, used as an input to measure fair value.

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- Definition

Rate at which loans or a loan portfolio are expected to prepay principal balances, used as an input to measure fair value.

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