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Intangible assets - Textual (Details) (USD $)
In Thousands, unless otherwise specified |
12 Months Ended | 1 Months Ended | ||
|---|---|---|---|---|
|
Dec. 31, 2013
|
Dec. 31, 2012
|
Dec. 31, 2011
|
Jun. 30, 2012
Wisconsin Alumni Research Foundation [Member]
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| Finite-Lived Intangible Assets [Line Items] | ||||
| Payments to acquire intangible assets | $ 404 | $ 2,395 | $ 373 | $ 210 |
| Amortization of licenses, patents and other agreements | 522 | 347 | 257 | |
| Increase in intangible due to non-compete agreement | $ 70 | |||