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Stock-based compensation - Stock Option Activity (Details) (USD $)
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9 Months Ended | 12 Months Ended | 3 Months Ended | 9 Months Ended | 3 Months Ended | 9 Months Ended | 12 Months Ended | 3 Months Ended | 12 Months Ended | 3 Months Ended | 9 Months Ended | 12 Months Ended | 3 Months Ended | 12 Months Ended | ||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
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Sep. 30, 2014
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Sep. 30, 2014
Tecogen
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Dec. 31, 2013
Tecogen
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Mar. 31, 2013
Ilois
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Sep. 30, 2014
Ilois
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Dec. 31, 2013
Ilois
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Mar. 31, 2014
Minimum
Tecogen
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Sep. 30, 2014
Minimum
Tecogen
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Dec. 31, 2012
Minimum
Tecogen
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Mar. 31, 2014
Minimum
Ilois
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Dec. 31, 2012
Minimum
Ilois
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Mar. 31, 2014
Maximum
Tecogen
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Sep. 30, 2014
Maximum
Tecogen
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Dec. 31, 2012
Maximum
Tecogen
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Mar. 31, 2014
Maximum
Ilois
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Dec. 31, 2012
Maximum
Ilois
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| Stock Options Outstanding [Roll Forward] | ||||||||||||||||
| Beginning (shares) | 1,148,000 | 575,000 | ||||||||||||||
| Granted (shares) | 118,325 | 50,000 | ||||||||||||||
| Exercised (shares) | (5,000) | 0 | ||||||||||||||
| Canceled and forfeited (shares) | (7,000) | 0 | ||||||||||||||
| Expired (shares) | 0 | 0 | ||||||||||||||
| Ending (shares) | 1,254,325 | 1,148,000 | 625,000 | |||||||||||||
| Exercisable (shares) | 929,250 | 181,250 | ||||||||||||||
| Vested and expected to vest (shares) | 1,254,325 | 625,000 | ||||||||||||||
| Exercise Price Per Share [Abstract] | ||||||||||||||||
| Exercise Price Per Share, Beginning (per share) | $ 1.2 | $ 1.20 | $ 0.10 | $ 0.10 | $ 4.5 | $ 4.50 | $ 0.50 | $ 0.50 | ||||||||
| Exercise Price Per Share, Granted (per share) | $ 0.50 | $ 4.50 | $ 5.39 | |||||||||||||
| Exercise Price Per Share, Exercised (per share) | $ 1.20 | $ 0 | ||||||||||||||
| Exercise Price Per Share, Cancelled and forfeited (per share) | $ 0 | $ 1.20 | $ 4.50 | |||||||||||||
| Exercise Price Per Share, Expired (per share) | $ 0.00 | $ 0 | ||||||||||||||
| Exercise Price Per Share, Ending (per share) | $ 1.2 | $ 1.20 | $ 0.10 | $ 0.10 | $ 4.5 | $ 4.50 | $ 0.50 | $ 0.50 | ||||||||
| Weighted Average Exercise Price [Roll Forward] | ||||||||||||||||
| Beginning (usd per share) | $ 2.13 | $ 0.29 | ||||||||||||||
| Granted (usd per share) | $ 4.69 | $ 0.50 | ||||||||||||||
| Exercised (usd per share) | $ 1.20 | $ 0 | ||||||||||||||
| Canceled and forfeited (usd per share) | $ 3.32 | $ 0 | ||||||||||||||
| Expried (usd per share) | $ 0.00 | $ 0 | ||||||||||||||
| Ending (usd per share) | $ 2.37 | $ 2.13 | $ 0.31 | |||||||||||||
| Exercisable (usd per share) | $ 1.92 | $ 0.50 | ||||||||||||||
| Vested and expected to vest (usd per share) | $ 2.37 | $ 0.31 | ||||||||||||||
| Weighted Average Remaining Life | 5 years 5 months 28 days | 5 years 9 months 18 days | 6 years 5 months 9 days | 6 years 3 months 0 days | ||||||||||||
| Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Additional Disclosures [Abstract] | ||||||||||||||||
| Outstanding, Aggregate Intrinsic Value | $ 7,051,694 | $ 2,721,100 | $ 120,000 | $ 120,000 | ||||||||||||
| Exercisable, Aggregate Intrinsic Value | 5,638,158 | 0 | ||||||||||||||
| Vested and expected to vest, Aggregate Intrinsic Value | $ 7,051,694 | $ 120,000 | ||||||||||||||