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Description of the changes in valuation technique(s) and related inputs used to measure fair value.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 820

-SubTopic 10

-Section 50

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For each line item in the statement of financial position, the amounts of gains and losses from fair value changes included in earnings.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 825

-SubTopic 10

-Section 50

-Paragraph 30

-Subparagraph (a)

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The current carrying amount of the liability for the freestanding or embedded guarantor's obligations under the guarantee or each group of similar guarantees.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 460

-SubTopic 10

-Section 50

-Paragraph 4

-Subparagraph (c)

-URI http://asc.fasb.org/extlink&oid=6851643&loc=d3e12069-110248

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Fair Value Inputs Credit Valuation Adjustment As A Percentage Of Derivative Contract

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Fair value measurement transfers from one level to another.

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Fair Values of Assets and Liabilities - Additional Information (Detail) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014
Fair Value Disclosures [Abstract]
Fair value measurement transfers from one level to another			$ 0	$ 0
Significant changes to the valuation techniques to measure fair value during the reporting period			No significant changes to the valuation techniques used by the Company to measure fair value.
Mortgage loans held for sale measured at fair value gain	$ 61,000,000	$ 4,000,000	$ 27,000,000	$ 102,000,000
Minimum [Member]
Fair Value Disclosures [Abstract]
Assumed credit valuation adjustment as percentage of derivative contract fair value			0.00%
Maximum [Member]
Fair Value Disclosures [Abstract]
Assumed credit valuation adjustment as percentage of derivative contract fair value			97.00%
Average [Member]
Fair Value Disclosures [Abstract]
Assumed credit valuation adjustment as percentage of derivative contract fair value			4.00%
Standby Letters Of Credit, Unfunded Commitments and Deferred Non-Yield Loan Fees [Member]
Fair Value Disclosures [Abstract]
Carrying value of guarantee obligations	411,000,000		$ 411,000,000		$ 413,000,000
Other Guarantees [Member]
Fair Value Disclosures [Abstract]
Carrying value of guarantee obligations	$ 196,000,000		$ 196,000,000		$ 211,000,000