Loans - Schedule of Subsequently Defaulted TDRs (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
Dec. 31, 2014 SecurityLoan	Dec. 31, 2013 SecurityLoan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of Loans		9
Pre-modification Outstanding Recorded Investment		$ 14,835
Post-modification Outstanding Recorded Investment		12,429
TDRs Occurring During The Period [Member] \| Non-Covered TDRs [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of Loans	40	54
Recorded Investment	1,600	17,305
Real Estate [Member] \| Commercial Loans [Member] \| TDRs Occurring During The Period [Member] \| Non-Covered TDRs [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of Loans		9
Pre-modification Outstanding Recorded Investment		14,835
Post-modification Outstanding Recorded Investment		12,429
Number of Loans	30	35
Recorded Investment		4,452
Business [Member] \| Commercial Loans [Member] \| TDRs Occurring During The Period [Member] \| Non-Covered TDRs [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of Loans	9	17
Recorded Investment	1,600	12,808
Home Equity [Member] \| Consumer and Other Loans [Member] \| TDRs Occurring During The Period [Member] \| Non-Covered TDRs [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of Loans		1
Recorded Investment		$ 45
Consumer - Other [Member] \| Consumer and Other Loans [Member] \| TDRs Occurring During The Period [Member] \| Non-Covered TDRs [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of Loans	1	1

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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=35738203&loc=SL6953676-111524

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Post-modification amount of investment in financing receivables modified by troubled debt restructurings.

+ References

+ Details

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- Definition

Pre-modification amount of investment in financing receivables modified by troubled debt restructurings.

+ References

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- Definition

Number of financing receivables that have been modified by troubled debt restructurings within the previous 12 months and 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=35738203&loc=SL6953682-111524

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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

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