Mortgage Servicing Assets - Changes in Carrying Amount of Mortgage Servicing Assets (Detail) - USD ($) $ in Millions	9 Months Ended
Sep. 30, 2015	Sep. 30, 2014
Servicing Asset [Abstract]
Balance at beginning of period	$ 323	$ 332
Servicing retained from loan sales	39	19
Purchases	29	33
Amortization	(71)	(76)
Balance at end of period	320	308
Fair value at end of period	$ 427	$ 370

No definition available.

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- Definition

Amortized amount of contract to service financial assets under which the benefits of servicing are expected to more than adequately compensate the servicer.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 860

-SubTopic 50

-Section 25

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=7524895&loc=d3e120260-111741

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 860

-SubTopic 50

-Section 45

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6469459&loc=d3e122492-111745

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 860

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-URI http://asc.fasb.org/extlink&oid=6469459&loc=d3e122501-111745

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- Definition

Amount of additions from purchases, assumption or transfer to contract to service financial assets under which the benefits of servicing are expected to more than adequately compensate the servicer.

+ References

+ Details

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- Definition

Amount of amortization of contract to service financial assets under which the benefits of servicing are expected to more than adequately compensate the servicer.

+ References

+ Details

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- Definition

Fair value of contract to service financial assets under which the benefits of servicing are expected to more than adequately compensate the servicer.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 860

-SubTopic 50

-Section 50

-Paragraph 4

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=7882072&loc=d3e122739-111746

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-Publisher FASB

-Name Accounting Standards Codification

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-SubTopic 20

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- Definition

Amount of other increase (decrease) to contract to service financial assets under which the benefits of servicing are expected to more than adequately compensate the servicer.

+ References

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