Fair Value Measurements - Additional Information (Detail) - Fair Value, Measurements, Recurring - Fair Value, Inputs, Level 3 - Mortgage Servicing Rights	9 Months Ended	12 Months Ended
Sep. 30, 2016 $ / Loan	Dec. 31, 2015 Loan $ / Loan
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loan segregated, number of pools \| Loan		14
Service costs assumed, per loan \| $ / Loan	6.00	6.00
Average PSA assumed rate	217.00%	163.00%
Discount rate	10.00%	11.00%
100% PSA \| First Month
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Prepayment rate	0.00%
100% PSA \| Between First Month and Month 30
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Prepayment rate increase, each month	0.20%
100% PSA \| Month 30
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Prepayment rate	6.00%
100% PSA \| Thereafter
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Prepayment rate	6.00%

Loans Segregated, Number Of Pools

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- Definition

Percentage Change In Prepayment Rate

+ References

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- Definition

Service Costs Assumed Per Loan

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- Definition

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

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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=66048111&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.

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- Definition

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

+ 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 (d)
-URI http://asc.fasb.org/extlink&oid=68078379&loc=d3e122596-111746

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