Servicing of Residential Loans - Schedule of Sensitivity Analysis of Fair Value, Servicing Rights Carried at Fair Value (Detail) - USD ($) $ in Thousands	6 Months Ended	12 Months Ended
Jun. 30, 2017	Dec. 31, 2016
Sensitivity Analysis of Fair Value of Interests Continued to be Held by Transferor, Servicing Assets or Liabilities, Impact of Adverse Change in Assumption [Line Items]
10% adverse change in weighted-average discount rate	$ (38,285)	$ (41,926)
10% adverse change in weighted-average conditional prepayment rate	(34,899)	(30,513)
10% adverse change in weighted-average conditional default rate	(27,968)	(28,370)
20% adverse change in weighted-average discount rate	(73,495)	(80,512)
20% adverse change in weighted-average conditional prepayment rate	(69,918)	(59,083)
20% adverse change in weighted-average conditional default rate	$ (57,189)	$ (57,854)
Minimum
Sensitivity Analysis of Fair Value of Interests Continued to be Held by Transferor, Servicing Assets or Liabilities, Impact of Adverse Change in Assumption [Line Items]
Adverse Change In Assumptions, Percent	10.00%
Maximum
Sensitivity Analysis of Fair Value of Interests Continued to be Held by Transferor, Servicing Assets or Liabilities, Impact of Adverse Change in Assumption [Line Items]
Adverse Change In Assumptions, Percent	20.00%
Fair Value, Measurements, Recurring \| Servicing Rights Carried at Fair Value \| Minimum
Sensitivity Analysis of Fair Value of Interests Continued to be Held by Transferor, Servicing Assets or Liabilities, Impact of Adverse Change in Assumption [Line Items]
Weighted-average discount rate	10.62%	10.68%
Weighted-average conditional prepayment rate	6.08%	5.76%
Weighted-average conditional default rate	0.02%	0.04%
Fair Value, Measurements, Recurring \| Servicing Rights Carried at Fair Value \| Maximum
Sensitivity Analysis of Fair Value of Interests Continued to be Held by Transferor, Servicing Assets or Liabilities, Impact of Adverse Change in Assumption [Line Items]
Weighted-average discount rate	15.22%	14.61%
Weighted-average conditional prepayment rate	23.87%	21.67%
Weighted-average conditional default rate	3.21%	2.97%
Fair Value, Measurements, Recurring \| Servicing Rights Carried at Fair Value \| Weighted Average
Sensitivity Analysis of Fair Value of Interests Continued to be Held by Transferor, Servicing Assets or Liabilities, Impact of Adverse Change in Assumption [Line Items]
Weighted-average discount rate	11.97%	11.56%
Weighted-average conditional prepayment rate	9.82%	9.09%
Weighted-average conditional default rate	0.85%	0.88%

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=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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Percentage of likelihood a loan will not be repaid and instead default, used as an input to measure fair value.

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The hypothetical financial impact of a 10 percent adverse change of the discount rate on the fair value of transferor's interests in transferred financial assets (including any servicing assets or servicing liabilities) as of the balance sheet date.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 20
-Section 50
-Paragraph 4
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=64830801&loc=d3e107314-111719

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The hypothetical financial impact of a 10 percent adverse change of the specified assumption on the fair value of transferor's interests in transferred financial assets (including any servicing assets or servicing liabilities) as of the balance sheet date.

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The hypothetical financial impact of a 10 percent adverse change of prepayment speed on the fair value of transferor's interests in transferred financial assets (including any servicing assets or servicing liabilities) as of the balance sheet date.

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The hypothetical financial impact of a 20 percent adverse change of the discount rate on the fair value of transferor's interests in transferred financial assets (including any servicing assets or servicing liabilities) as of the balance sheet date.

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The hypothetical financial impact of a 20 percent adverse change of the specified assumption on the fair value of transferor's interests in transferred financial assets (including any servicing assets or servicing liabilities) as of the balance sheet date.

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The hypothetical financial impact of a 20 percent adverse change of prepayment speed on the fair value of transferor's interests in transferred financial assets (including any servicing assets or servicing liabilities) as of the balance sheet date.

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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.

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Sensitivity analysis of fair value of interests continued to be held by transferor servicing assets or liabilities adverse change in assumptions percent.

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