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Segments and Geographical Information - Additional Information (Detail)
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12 Months Ended | ||
|---|---|---|---|
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Dec. 31, 2012
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Dec. 31, 2011
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Dec. 31, 2010
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| Segment Reporting Information [Line Items] | |||
| Percentage of revenue from a single external customer | 12.00% | 12.00% | 11.00% |