Loans and Allowance for Loan Losses - Impaired Loans, Segregated by Class of Loans (Detail) (USD $) In Thousands, unless otherwise specified	6 Months Ended
Jun. 30, 2013	Jun. 30, 2012
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities Acquired During Period [Line Items]
Unpaid Principal Balance	$ 48,260	$ 52,067
Recorded Investment with Allowance	43,484	47,579
Related Allowance	4,449	4,454
Average Recorded Investment	44,884	50,266
Non-residential real estate [Member]
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities Acquired During Period [Line Items]
Unpaid Principal Balance	28,111	28,184
Recorded Investment with Allowance	26,607	27,165
Related Allowance	2,391	2,122
Average Recorded Investment	26,508	27,397
Residential real estate [Member]
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities Acquired During Period [Line Items]
Unpaid Principal Balance	5,204	5,839
Recorded Investment with Allowance	4,581	5,384
Related Allowance	1,253	1,468
Average Recorded Investment	5,262	5,547
Non-consumer non-real estate [Member]
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities Acquired During Period [Line Items]
Unpaid Principal Balance	1,816	1,792
Recorded Investment with Allowance	1,481	1,163
Related Allowance	390	302
Average Recorded Investment	1,536	1,512
Consumer non-real estate [Member]
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities Acquired During Period [Line Items]
Unpaid Principal Balance	517	349
Recorded Investment with Allowance	495	325
Related Allowance	79	59
Average Recorded Investment	419	389
Other loans [Member]
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities Acquired During Period [Line Items]
Unpaid Principal Balance	2,253	2,255
Recorded Investment with Allowance	2,090	2,020
Related Allowance	278	212
Average Recorded Investment	2,648	2,158
Acquired loans [Member]
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities Acquired During Period [Line Items]
Unpaid Principal Balance	10,359	13,648
Recorded Investment with Allowance	8,230	11,522
Related Allowance	58	291
Average Recorded Investment	$ 8,511	$ 13,263

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Average amount of investment of impaired financing receivables with related allowance for credit losses and without a related allowance for credit losses.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 310

-SubTopic 10

-Section 50

-Paragraph 15

-Subparagraph (c)(1)

-URI http://asc.fasb.org/extlink&oid=28368275&loc=d3e5212-111524

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 310

-SubTopic 10

-Section 50

-Paragraph 17

-URI http://asc.fasb.org/extlink&oid=28368275&loc=d3e5258-111524

+ Details

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- Definition

Amount of investment of impaired financing receivables with related allowance for credit losses and without a related allowance for credit losses.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 310

-SubTopic 10

-Section 50

-Paragraph 14A

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=28368275&loc=SL6953550-111524

+ Details

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- Definition

Amount of allowance for credit losses related to recorded investment.

+ References

+ Details

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- Definition

Amount of unpaid principal balance of impaired financing receivables with related allowance for credit losses and without related allowance for credit losses.

+ References

+ Details

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