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Inventories - Additional Information (Detail) (USD $)
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3 Months Ended | 6 Months Ended | ||
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Jun. 30, 2013
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Jun. 30, 2012
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Jun. 30, 2013
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Jun. 30, 2012
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| Inventory Disclosure [Abstract] | ||||
| Negative impact of net income under inventory valuation LIFO method | $ 481,000 | $ (383,000) | $ (903,000) | $ (383,000) |