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Goodwill - Additional Information (Detail) (USD $)
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9 Months Ended | 12 Months Ended |
|---|---|---|
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Sep. 30, 2014
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Dec. 31, 2013
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| Goodwill And Intangible Assets Disclosure [Abstract] | ||
| Changes in the carrying amount of goodwill | $ 0 | |
| Amortization period of acquired goodwill for tax purpose | 15 years |