Fair Value Measurements - Additional Information (Detail) - Fair Value, Measurements, Recurring - Fair Value, Inputs, Level 3 - Mortgage Servicing Rights	6 Months Ended	12 Months Ended
Jun. 30, 2017 Loan $ / Loan	Dec. 31, 2016 Loan $ / Loan
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Number of portfolio	2
Fannie Mae
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	6.33	6.00
Average PSA assumed rate	147.00%	150.00%
Discount rate	14.00%	14.00%
Freddie Mac
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loan segregated, number of pools \| Loan	5
Service costs assumed, per loan \| $ / Loan	7.67
Average PSA assumed rate	195.00%
Discount rate	102.84%
Constant prepayment rate	7.51%
100% PSA \| Fannie Mae \| First Month
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Prepayment rate	0.00%
100% PSA \| Fannie Mae \| 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 \| Fannie Mae \| Month 30
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Prepayment rate	6.00%
100% PSA \| Fannie Mae \| Thereafter
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Prepayment rate	6.00%

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Loans Segregated, Number Of Pools

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Number of Portfolio.

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Percentage Change In Prepayment Rate

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Service Costs Assumed Per Loan

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

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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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