Commitments and contingencies - Additional Information (Details) - USD ($) |
6 Months Ended | |
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Jun. 30, 2015 |
Jun. 30, 2014 |
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| Guarantor Obligations [Line Items] | ||
| Short term investments | $ 291,047 | $ 0 |
| Revolving Credit Facility [Member] | ||
| Guarantor Obligations [Line Items] | ||
| Letters of Credit Outstanding, Amount | 583,073 | |
| Chief Executive Officer (John N. Hatsopoulos) | Letter of Credit [Member] | ||
| Guarantor Obligations [Line Items] | ||
| Collateralized Financings | $ 1,055,000 | |
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- Definition The value of the collateral (typically cash) that the entity receives in a financing transaction in exchange for securities lent. This item represents a liability in the financial statements of the lender of the securities. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. No definition available.
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- Definition The total amount of the contingent obligation under letters of credit outstanding as of the reporting date. No definition available.
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- Definition The cash inflow from a borrowing net of the cash outflow from repayment of a borrowing having initial term of repayment within three months. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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