Servicing of Residential Loans - Significant Judgment and Key Economic Assumptions Used in Estimation of Fair Value of Servicing Rights (Detail)	3 Months Ended	12 Months Ended
Mar. 31, 2015	Dec. 31, 2014
Servicing Rights Carried at Amortized Cost [Member] \| Forward Loans [Member]
Inputs and assumptions:
Weighted-average remaining life in years	5 years 6 months 20 days
Weighted-average stated borrower interest rate on underlying collateral	7.87%
Weighted-average discount rate	12.10%
Conditional prepayment rate	6.54%
Conditional default rate	2.62%
Servicing Rights Carried at Amortized Cost [Member] \| Reverse Loans [Member]
Inputs and assumptions:
Weighted-average remaining life in years	3 years 3 months 0 days
Weighted-average stated borrower interest rate on underlying collateral	3.53%
Weighted-average discount rate	15.00%
Conditional repayment rate	25.13%
Servicing Rights Carried at Fair Value [Member]
Inputs and assumptions:
Weighted-average remaining life in years	6 years 2 months 12 days	6 years 7 months 3 days
Servicing Rights Carried at Fair Value [Member] \| Weighted Average [Member]
Inputs and assumptions:
Weighted-average stated borrower interest rate on underlying collateral	4.53%	4.65%
Weighted-average discount rate	9.77%	9.55%
Conditional prepayment rate	8.88%	7.87%
Conditional default rate	1.63%	2.36%

Weighted average life of securitized assets regardless of when the transfer occurred, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 860

-SubTopic 20

-Section 50

-Paragraph 4

-Subparagraph (b)(2)

-URI http://asc.fasb.org/extlink&oid=13989330&loc=d3e107314-111719

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- Definition

Discount rate which is used to value residual cash flows generated by financial assets of a securitization, asset-backed financing arrangement, or similar transfer regardless of when the transfer occurred.

+ 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 (b)(1)

-URI http://asc.fasb.org/extlink&oid=13989330&loc=d3e107314-111719

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- Definition

Estimated rate of prepayment of principal on financial assets regardless of when the transfer occurred.

+ References

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- Definition

Discount rate which is used to value residual cash flows generated by financial assets of the securitization, asset-backed financing arrangement, or similar transfer for initial fair value measurement.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 860

-SubTopic 20

-Section 50

-Paragraph 3

-Subparagraph (c)(1)

-URI http://asc.fasb.org/extlink&oid=13989330&loc=d3e107207-111719

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- Definition

Estimated rate of prepayment of principal on financial assets for initial fair value measurement.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 860

-SubTopic 20

-Section 50

-Paragraph 3

-Subparagraph (c)(2)

-URI http://asc.fasb.org/extlink&oid=13989330&loc=d3e107207-111719

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- Definition

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

+ 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

Assumption for fair value of interests continued to be held by transferor servicing assets or liabilities conditional repayment rate.

+ References

No definition available.

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- Definition

Assumption for fair value of interests continued to be held by transferor servicing assets or liabilities stated customer interest rate on underlying collateral.

+ References

No definition available.

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