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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
-Paragraph 2
-Subparagraph (bbb)
-URI http://asc.fasb.org/extlink&oid=36462937&loc=d3e19207-110258

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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)
-URI http://asc.fasb.org/extlink&oid=6957238&loc=d3e14172-108612

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- Definition

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

+ References

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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No definition available.

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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
	Mar. 31, 2016	Mar. 31, 2015	Dec. 31, 2015
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 (loss)	$ 52,000,000	$ 49,000,000
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	78.00%
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	$ 545,000,000		$ 515,000,000
Other Guarantees [Member]
Fair Value Disclosures [Abstract]
Carrying value of guarantee obligations	$ 189,000,000		$ 184,000,000