Allowance for Loan Losses - Additional Information (Detail)	12 Months Ended
Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($) Contracts TDRs
Financing Receivable, Allowance for Credit Losses [Line Items]
Troubled debt restructurings, subsequently defaulted	$ 0
Commitment to lend additional funds to TDR borrowers	$ 0
Number of troubled debt restructurings \| Contracts		2
Commercial Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Troubled debt restructurings, subsequently defaulted		$ 2,191,000,000
Number of troubled debt restructurings \| TDRs		1
Commercial and Industrial [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Financing allowance increase in principal		$ 100,000
Number of troubled debt restructurings \| Contracts		2

Financing receivable modifications increase in principal.

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

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- Definition

Number of financing receivables that have been modified by troubled debt restructurings.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 33
-URI http://asc.fasb.org/extlink&oid=49124121&loc=SL6953676-111524

+ Details

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- Definition

Amount of investment related to financing receivables modified by troubled debt restructurings within the previous 12 months, for which there was a payment default.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 34
-URI http://asc.fasb.org/extlink&oid=49124121&loc=SL6953682-111524

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- Definition

Reflects the unfunded portion of contractual agreements to lend funds to borrowers for loans whose terms have been modified by troubled debt restructuring.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 40
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=25495931&loc=d3e18794-111554

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