| **Fair Value of Derivative Financial Instruments and Their Classification on Balance Sheet (Detail) (Interest rate contracts, USD $)In Thousands, unless otherwise specified** | Mar. 31, 2013 | Dec. 31, 2012 |
|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|---------------|---------------|
| Designated as Hedging Instrument | Other Assets                                                                                                                                |          |          |
| **Derivatives, Fair Value [Line Items]**                                                                                                                                       |          |          |
| Asset Derivatives                                                                                                                                                              | $ 233         | $ 197         |
| Designated as Hedging Instrument | Other Liabilities                                                                                                                           |          |          |
| **Derivatives, Fair Value [Line Items]**                                                                                                                                       |          |          |
| Liability derivatives                                                                                                                                                          | 2,888         | 3,332         |
| Not Designated as Hedging Instrument | Other Assets                                                                                                                            |          |          |
| **Derivatives, Fair Value [Line Items]**                                                                                                                                       |          |          |
| Asset Derivatives                                                                                                                                                              | 5,155         | 6,103         |
| Not Designated as Hedging Instrument | Other Liabilities                                                                                                                       |          |          |
| **Derivatives, Fair Value [Line Items]**                                                                                                                                       |          |          |
| Liability derivatives                                                                                                                                                          | $ 5,419       | $ 6,434       |

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| - Definition
Fair value of derivative asset, presented on a gross basis even when the derivative instrument is subject to master netting arrangements and qualifies for net presentation in the statement of financial position.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 133 -Paragraph 205G -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.  This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 133 -Paragraph 44C -Subparagraph a -Clause 1 -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.  This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 4B -Subparagraph (a),(c) -URI http://asc.fasb.org/extlink&oid=7476318&loc=SL5624163-113959
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| - Definition
Fair value of derivative liability, presented on a gross basis even when the derivative instrument is subject to master netting arrangements and qualifies for net presentation in the statement of financial position.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 133 -Paragraph 205G -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.  This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 133 -Paragraph 44C -Subparagraph a -Clause 1 -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.  This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 4B -Subparagraph (a),(c) -URI http://asc.fasb.org/extlink&oid=7476318&loc=SL5624163-113959
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