Fair Values of Assets and Liabilities - Valuation Assumption Ranges for MSRs (Detail) - Mortgage Servicing Rights [Member]	9 Months Ended	12 Months Ended
Sep. 30, 2015	Dec. 31, 2014
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Expected prepayment	12.20%	12.10%
Discount rate	10.00%	10.10%
Minimum [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Expected prepayment	11.00%
Discount rate	9.00%
Maximum [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Expected prepayment	20.00%
Discount rate	13.00%
Average [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Expected prepayment	12.00%
Discount rate	10.00%

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.

No definition available.

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- Definition

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.

+ References

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

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

+ References

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