Troubled Debt Restructurings by Accrual Status (Detail) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Financing Receivable, Modifications [Line Items]
Recorded investment in loans	$ 289,009	$ 286,236
Residential
Financing Receivable, Modifications [Line Items]
Recorded investment in loans	108,249	108,603
Land
Financing Receivable, Modifications [Line Items]
Recorded investment in loans	10,210	9,657
Construction
Financing Receivable, Modifications [Line Items]
Recorded investment in loans	12,083	11,763
Commercial Real Estate
Financing Receivable, Modifications [Line Items]
Recorded investment in loans	70,469	68,902
Commercial Business
Financing Receivable, Modifications [Line Items]
Recorded investment in loans	21,440	18,655
Home Equity and Second Mortgage
Financing Receivable, Modifications [Line Items]
Recorded investment in loans	34,177	37,286
Other Consumer
Financing Receivable, Modifications [Line Items]
Recorded investment in loans	32,381	31,370
Troubled Debt Restructuring
Financing Receivable, Modifications [Line Items]
Accruing	1,535	221
Nonaccrual	2,303	4,099
Recorded investment in loans	3,838	4,320
Related Allowance For Loan Losses	1,140	1,293
Troubled Debt Restructuring \| Residential
Financing Receivable, Modifications [Line Items]
Accruing	357	180
Nonaccrual	353	588
Recorded investment in loans	710	768
Related Allowance For Loan Losses	50	87
Troubled Debt Restructuring \| Land
Financing Receivable, Modifications [Line Items]
Accruing	0	0
Nonaccrual	0	0
Recorded investment in loans	0	0
Related Allowance For Loan Losses	0	0
Troubled Debt Restructuring \| Construction
Financing Receivable, Modifications [Line Items]
Accruing	0	0
Nonaccrual	109	170
Recorded investment in loans	109	170
Related Allowance For Loan Losses	0	0
Troubled Debt Restructuring \| Commercial Real Estate
Financing Receivable, Modifications [Line Items]
Accruing	1,178	0
Nonaccrual	0	1,534
Recorded investment in loans	1,178	1,534
Related Allowance For Loan Losses	0	83
Troubled Debt Restructuring \| Commercial Business
Financing Receivable, Modifications [Line Items]
Accruing	0	0
Nonaccrual	1,776	1,776
Recorded investment in loans	1,776	1,776
Related Allowance For Loan Losses	1,065	1,098
Troubled Debt Restructuring \| Home Equity and Second Mortgage
Financing Receivable, Modifications [Line Items]
Accruing	0	41
Nonaccrual	65	31
Recorded investment in loans	65	72
Related Allowance For Loan Losses	25	25
Troubled Debt Restructuring \| Other Consumer
Financing Receivable, Modifications [Line Items]
Accruing	0	0
Nonaccrual	0	0
Recorded investment in loans	0	0
Related Allowance For Loan Losses	$ 0	$ 0

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Amount of allowance to cover probable credit losses on loans and leases. Includes carryover of or adjustments to the allowance for loan losses in connection with business combinations. Excludes allowance for loans and leases covered under loss sharing agreements.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 210

-Section S99

-Paragraph 1

-Subparagraph (SX 210.9-03.7(d))

-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 03

-Paragraph 7

-Subparagraph d

-Article 9

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 310

-SubTopic 30

-Section 50

-Paragraph 2

-Subparagraph (b)(1)(ii)

-URI http://asc.fasb.org/extlink&oid=6379141&loc=d3e15032-111544

Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Staff Accounting Bulletin (SAB)

-Number Topic 6

-Section L

-Subsection 1

+ Details

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- Definition

Amount before allowance of loans and leases held in portfolio, including but not limited to, commercial and consumer loans. Includes deferred interest and fees, undisbursed portion of loan balance, unamortized costs and premiums and discounts from face amounts. Excludes loans and leases covered under loss sharing agreements.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 310

-SubTopic 10

-Section 45

-Paragraph 2

-URI http://asc.fasb.org/extlink&oid=28367877&loc=d3e4428-111522

+ Details

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- Definition

Reflects the carrying amount of loans deemed to be questionable as to collection on which interest is continuing to be earned or accrued.

+ References

No definition available.

+ Details

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- Definition

Reflects the carrying amount of loans deemed to be questionable as to collection on which no interest is continuing to be recognized.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 310

-SubTopic 10

-Section 50

-Paragraph 7

-Subparagraph (a)

-URI http://asc.fasb.org/extlink&oid=28368275&loc=d3e5111-111524

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