Derivative Financial Instruments - Additional Information (Detail) (USD $)	3 Months Ended
Mar. 31, 2013	Mar. 31, 2013 Cash Flow Hedging Interest Rate Swap Contract	Mar. 31, 2012 Cash Flow Hedging Interest Rate Swap Contract	Mar. 31, 2013 Cash Flow Hedging Interest Rate Cap Contract	Mar. 31, 2012 Cash Flow Hedging Interest Rate Cap Contract
Derivative [Line Items]
Number of interest rate derivatives held		2	2	1	1
Notional amount of interest rate derivatives		$ 26,000,000	$ 26,000,000	$ 13,000,000	$ 13,000,000
Estimated amount to be transferred from OCI to earnings	767,000
Notional amount of interest rate derivatives not designated as hedging instruments	159,817,000
Termination value of derivatives in a net liability position	8,510,000
Derivative collateral posted	$ 7,638,000

The aggregate fair value of assets that are already posted, at the end of the reporting period, as collateral for derivative instruments with credit-risk-related contingent features.

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 133

-Paragraph 44D

-Subparagraph c

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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.

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-Publisher FASB

-Name Accounting Standards Codification

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The estimated value of gains (losses), net anticipated to be transferred in the future from accumulated other comprehensive income into earnings.

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The aggregate fair value amounts of derivative instruments that contain credit-risk-related contingent features that are in a net liability position at the end of the reporting period. For nonderivative instruments that are designated and qualify as hedging instruments, the fair value amounts are the carrying value of the nonderivative hedging instrument, including the adjustment for the foreign currency transaction gain (loss) on that instrument.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 815

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-Publisher FASB

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-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.

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- Definition

Aggregate notional amount of all interest rate derivatives designated as hedging instruments in cash flow hedges. Notional amount refers to the monetary amount specified in the interest rate derivative contract.

+ References

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

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-Publisher FASB

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-Glossary Notional Amount

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Aggregate notional amount of all interest rate derivatives not designated as hedging instruments. Notional amount refers to the monetary amount specified in the interest rate derivative contract.

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Number of interest rate derivative instruments held by the entity at the reporting date.

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