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Revenues Revenues (Details Textual) | 3 Months Ended
--- | ---
Mar. 31, 2018 | Mar. 31, 2017
Distributor One |  |
Disaggregation of Revenue [Line Items] |  |
Percentage of revenues from major distributors | 34.00% | 36.80%
Distributor Two |  |
Disaggregation of Revenue [Line Items] |  |
Percentage of revenues from major distributors | 15.90% | 19.30%

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