| **Summary of Troubled Debt Restructurings and Subsequent Defaults (Detail) (USD $)In Thousands, unless otherwise specified** | Mar. 31, 2013 | Mar. 31, 2012 |
|------------------------------------------------------------------------------------------------------------------------------|---------------|---------------|
| **Financing Receivable, Modifications [Line Items]**                                                                         |          |          |
| Modification                                                                                                                 | $ 552         | $ 2,097       |
| Troubled Debt Restructurings, Term Modifications                                                                             |          |          |
| **Financing Receivable, Modifications [Line Items]**                                                                         |          |          |
| Modification                                                                                                                 | 31            | 2,072         |
| Troubled Debt Restructurings, Rate Modifications                                                                             |          |          |
| **Financing Receivable, Modifications [Line Items]**                                                                         |          |          |
| Modification                                                                                                                 |     | 22            |
| Troubled Debt Restructurings, Rate and Term Modifications                                                                    |          |          |
| **Financing Receivable, Modifications [Line Items]**                                                                         |          |          |
| Modification                                                                                                                 | 521           | 25            |
| Commercial and industrial                                                                                                    |          |          |
| **Financing Receivable, Modifications [Line Items]**                                                                         |          |          |
| Modification                                                                                                                 | 100           | 238           |
| Commercial and industrial | Troubled Debt Restructurings, Term Modifications                                                 |          |          |
| **Financing Receivable, Modifications [Line Items]**                                                                         |          |          |
| Modification                                                                                                                 | 31            | 238           |
| Commercial and industrial | Troubled Debt Restructurings, Rate Modifications                                                 |          |          |
| **Financing Receivable, Modifications [Line Items]**                                                                         |          |          |
| Modification                                                                                                                 |          | 22            |
| Commercial and industrial | Troubled Debt Restructurings, Rate and Term Modifications                                        |          |          |
| **Financing Receivable, Modifications [Line Items]**                                                                         |          |          |
| Modification                                                                                                                 | 69            |     |
| Commercial and farm land                                                                                                     |          |          |
| **Financing Receivable, Modifications [Line Items]**                                                                         |          |          |
| Modification                                                                                                                 | 415           | 1,635         |
| Commercial and farm land | Troubled Debt Restructurings, Term Modifications                                                  |          |          |
| **Financing Receivable, Modifications [Line Items]**                                                                         |          |          |
| Modification                                                                                                                 |          | 1,635         |
| Commercial and farm land | Troubled Debt Restructurings, Rate Modifications                                                  |          |          |
| **Financing Receivable, Modifications [Line Items]**                                                                         |          |          |
| Modification                                                                                                                 |     |     |
| Commercial and farm land | Troubled Debt Restructurings, Rate and Term Modifications                                         |          |          |
| **Financing Receivable, Modifications [Line Items]**                                                                         |          |          |
| Modification                                                                                                                 | 415           |     |
| Residential                                                                                                                  |          |          |
| **Financing Receivable, Modifications [Line Items]**                                                                         |          |          |
| Modification                                                                                                                 | 37            | 224           |
| Residential | Troubled Debt Restructurings, Term Modifications                                                               |          |          |
| **Financing Receivable, Modifications [Line Items]**                                                                         |          |          |
| Modification                                                                                                                 |          | 199           |
| Residential | Troubled Debt Restructurings, Rate and Term Modifications                                                      |          |          |
| **Financing Receivable, Modifications [Line Items]**                                                                         |          |          |
| Modification                                                                                                                 | $ 37          | $ 25          |

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