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Subsequent events - Narrative (Details) (USD $)
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12 Months Ended | 1 Months Ended | 0 Months Ended | 12 Months Ended | 0 Months Ended | 9 Months Ended | 1 Months Ended | 1 Months Ended | 0 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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Sep. 30, 2013
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Oct. 18, 2013
Conversion of accrued interest in 2012 [Member]
Board of Directors Chairman [Member]
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Oct. 18, 2013
Conversion of accrued interest [Member]
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May 11, 2009
Chief Executive Officer (John N. Hatsopoulos)
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Dec. 31, 2012
Chief Executive Officer (John N. Hatsopoulos)
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Sep. 30, 2013
Chief Executive Officer (John N. Hatsopoulos)
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Mar. 25, 2013
Chief Executive Officer (John N. Hatsopoulos)
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Mar. 14, 2013
Prepayment from related party for future 2013 purchases
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Sep. 30, 2013
Prepayment from related party for future 2013 purchases
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Nov. 14, 2013
Subsequent event
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Jul. 22, 2013
Subsequent event
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Oct. 18, 2013
Subsequent event
Convertible Common Stock [Member]
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Oct. 03, 2013
Subsequent event
Chief Executive Officer (John N. Hatsopoulos)
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Mar. 25, 2013
Subsequent event
Chief Executive Officer (John N. Hatsopoulos)
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Mar. 14, 2013
Subsequent event
Prepayment from related party for future 2013 purchases
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| Subsequent Event [Line Items] | ||||||||||||||||||
| Prepayments received from related party | $ 827,747 | $ 420,317 | $ 827,747 | |||||||||||||||
| Discount rate on related party prepaid purchases | 6.00% | 6.00% | ||||||||||||||||
| Working capital line of credit with related party | 1,500,000 | 1,000,000 | 1,000,000 | |||||||||||||||
| Common Stock, Par or Stated Value Per Share | $ 0.001 | $ 0.001 | $ 0.001 | $ 0.001 | $ 0.001 | |||||||||||||
| Debt Instrument, Face Amount | 450,000 | |||||||||||||||||
| Related Party Transaction, Rate | 1.50% | 6.00% | ||||||||||||||||
| Stock Issued During Period, Shares, New Issues | 744,378 | |||||||||||||||||
| Share Price | $ 4.50 | |||||||||||||||||
| Proceeds from Issuance of Common Stock | 680,000 | 3,610,993 | 1,211,249 | 3,349,700 | ||||||||||||||
| Debt Conversion, Original Debt, Amount | 90,967 | |||||||||||||||||
| Debt Conversion, Converted Instrument, Shares Issued | 500,000 | 75,806 | ||||||||||||||||
| Debt Instrument, Convertible, Conversion Price | $ 3.20 | $ 4.50 | $ 1.20 | |||||||||||||||
| Convertible Debenture, Related Parties, Current | $ 90,967 | $ 0 | $ 90,967 | $ 6,913 | $ 4,366 | |||||||||||||
| Debt Instrument, Convertible, Number of Equity Instruments | 2,161 | 970 | ||||||||||||||||