Mortgage Servicing Assets - Schedule of Range and Weighted-Average of Significant Unobservable Inputs (Detail) (Discounted Cash Flow [Member], USD $)	3 Months Ended
Mar. 31, 2015	Mar. 31, 2014
Servicing Assets at Fair Value [Line Items]
Prepayment speed	4.80%	4.90%
Expected defaults	1.80%	2.00%
Residual cash flows discount rate	7.80%	7.80%
Escrow earn rate	1.90%	1.80%
Servicing cost	$ 1,059,000,000	$ 963,000,000
Loan assumption rate	1.43%	1.58%
Percentage late	0.33%	0.33%
Minimum [Member]
Servicing Assets at Fair Value [Line Items]
Prepayment speed	1.60%	1.90%
Expected defaults	1.00%	1.00%
Residual cash flows discount rate	7.00%	7.00%
Escrow earn rate	0.70%	0.40%
Servicing cost	150,000,000	150,000,000
Loan assumption rate	0.20%	0.20%
Percentage late	0.00%	0.00%
Maximum [Member]
Servicing Assets at Fair Value [Line Items]
Prepayment speed	13.10%	11.30%
Expected defaults	3.00%	3.00%
Residual cash flows discount rate	15.00%	14.00%
Escrow earn rate	3.10%	3.10%
Servicing cost	$ 2,735,000,000	$ 2,600,000,000
Loan assumption rate	3.00%	3.00%
Percentage late	2.00%	2.00%

Interest rate used to account for mortgage loan at fair value upon assumption.

No definition available.

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- Definition

Mortgage servicing assets, assumptions used to estimate fair value, percentage late.

+ References

No definition available.

+ Details

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- Definition

Mortgage servicing assets interest rate for mortgage funds.

+ References

No definition available.

+ Details

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- Definition

Mortgage servicing assets servicing cost.

+ References

No definition available.

+ Details

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- Definition

Discount rate used to estimate the fair value of 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=7882072&loc=d3e122596-111746

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- Definition

Percentage of contractually collectible principal associated with a financial asset expected not to be collected due to default by the borrower.

+ References

+ Details

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- Definition

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

+ References

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