Summary of All Troubled Debt Restructuring Loans (Accruing and Non Accruing) by Portfolio Segment (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2012 Contract	Dec. 31, 2011 Contract
Financing Receivable, Modifications [Line Items]
Number of Contracts	23	24
Pre-Modification Outstanding Recorded Investment	$ 4,468	$ 5,092
Post-Modification Outstanding Recorded Investment	4,571	5,297
Current Balance	4,211	4,682
Residential real estate loans
Financing Receivable, Modifications [Line Items]
Number of Contracts	18	19
Pre-Modification Outstanding Recorded Investment	3,124	3,221
Post-Modification Outstanding Recorded Investment	3,227	3,426
Current Balance	3,095	3,330
Commercial real estate loans
Financing Receivable, Modifications [Line Items]
Number of Contracts	2	3
Pre-Modification Outstanding Recorded Investment	1,178	1,708
Post-Modification Outstanding Recorded Investment	1,178	1,708
Current Balance	1,013	1,249
Commercial loans
Financing Receivable, Modifications [Line Items]
Number of Contracts	2	2
Pre-Modification Outstanding Recorded Investment	163	163
Post-Modification Outstanding Recorded Investment	163	163
Current Balance	100	103
Consumer loans
Financing Receivable, Modifications [Line Items]
Number of Contracts	1
Pre-Modification Outstanding Recorded Investment	3
Post-Modification Outstanding Recorded Investment	3
Current Balance	$ 3

Name:	us-gaap_FinancingReceivableModificationsLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

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=7512638&loc=SL6953676-111524

+ Details

Name:	us-gaap_FinancingReceivableModificationsNumberOfContracts1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

Amount of investment in financing receivables (after modification) modified by troubled debt restructurings.

+ References

+ Details

Name:	us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount of investment in financing receivables (before modification) modified by troubled debt restructurings.

+ References

+ Details

Name:	us-gaap_FinancingReceivableModificationsPreModificationRecordedInvestment1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

The amount of the outstanding recorded investment related to 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 40

-Section 50

-Paragraph 4

-URI http://asc.fasb.org/extlink&oid=6951948&loc=d3e18845-111554

+ Details

Name:	us-gaap_FinancingReceivableModificationsRecordedInvestment
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant