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Intangible assets other than goodwill - Narrative (Details) (USD $)
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6 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, 2011
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Dec. 31, 2010
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| Acquired Finite-Lived Intangible Assets [Line Items] | ||||
| Finited lived intangible assets, estimated useful life | 15 years | |||
| Amortization expense | $ 24,247 | $ 33,896 | $ 23,992 | $ 11,309 |
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Product Certifications
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| Acquired Finite-Lived Intangible Assets [Line Items] | ||||
| Capitalized Finite-lived Intangible Assets Acquired | 17,314 | 22,036 | ||
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Patents
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| Acquired Finite-Lived Intangible Assets [Line Items] | ||||
| Capitalized Finite-lived Intangible Assets Acquired | $ 146,981 | $ 16,712 | ||
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Patents | Minimum
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| Acquired Finite-Lived Intangible Assets [Line Items] | ||||
| Finited lived intangible assets, estimated useful life | 7 years | |||
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Patents | Maximum
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| Acquired Finite-Lived Intangible Assets [Line Items] | ||||
| Finited lived intangible assets, estimated useful life | 10 years | |||