| Share-Based Compensation - Additional Information (Detail) (USD $) | 3 Months Ended | 9 Months Ended | ||
|---|---|---|---|---|
| Sep. 30, 2012 | Sep. 30, 2011 | Sep. 30, 2012 | Sep. 30, 2011 | |
| Share-Based Compensation Expense | $ 42,000 | $ 59,000 | $ 144,000 | $ 440,000 | 
| Amount of tax benefits | $ 18,000 | $ 25,000 | $ 61,000 | $ 185,000 | 
| Number of options exercised | ||||
| X | ||||||||||
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- Definition The total recognized tax benefit related to compensation cost for equity-based payment arrangements recognized in income during the period. Reference 1: http://www.xbrl.org/2003/role/presentationRef 
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| X | ||||||||||
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- Definition The aggregate amount of noncash, equity-based employee remuneration. This may include the value of stock or unit options, amortization of restricted stock or units, and adjustment for officers' compensation. As noncash, this element is an add back when calculating net cash generated by operating activities using the indirect method. Reference 1: http://www.xbrl.org/2003/role/presentationRef 
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| X | ||||||||||
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- Definition Number of share options (or share units) exercised during the current period. Reference 1: http://www.xbrl.org/2003/role/presentationRef 
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