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Restructuring - Additional Information (Detail) (USD $)
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3 Months Ended | 12 Months Ended | |||
|---|---|---|---|---|---|
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Jun. 30, 2013
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Dec. 31, 2012
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Dec. 31, 2014
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Dec. 31, 2013
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Dec. 31, 2012
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| Restructuring Cost and Reserve [Line Items] | |||||
| Research and development expense | $ 100,000 | $ 588,000 | $ 1,336,000 | $ 2,218,000 | |
| Restructuring cost incurred | 192,000 | ||||
| Payment of severance and other costs | $ 134,000 | ||||
| China [Member] | |||||
| Restructuring Cost and Reserve [Line Items] | |||||
| Number of reduced employees | 21 | ||||
| Percentage of reduced employees worldwide | 20.00% | ||||