Quarterly report pursuant to Section 13 or 15(d)

Stock-based compensation - Stock Option Activity (Details)

v3.8.0.1
Stock-based compensation - Stock Option Activity (Details) - Tecogen - USD ($)
 9 Months Ended 12 Months Ended
Sep. 30, 2017
Dec. 31, 2016
Stock Options Outstanding [Roll Forward]    
Beginning (shares) 1,117,918  
Granted (shares) 45,000  
Assumed in merger (shares) 156,124  
Exercised (shares) (79,543)  
Canceled and forfeited (shares) (106,112)  
Ending (shares) 1,133,387 1,117,918
Exercisable (shares) 883,631  
Vested and expected to vest (shares) 1,095,925  
Exercise Price Per Share [Abstract]    
Exercise Price Per Share, Outstanding, Minimum (per share) $ 0.79 $ 0.79
Exercise Price Per Share, Outstanding, Maximum (dollars per share) 30.33 5.39
Weighted Average Exercise Price [Roll Forward]    
Beginning (usd per share) 3.10  
Granted (usd per share) 3.35  
Assumed in merger (usd per share) 10.35  
Exercised (usd per share) 1.62  
Canceled and forfeited (usd per share) 9.67  
Ending (usd per share) 3.62 $ 3.10
Exercisable (usd per share) 3.42  
Vested and expected to vest (usd per share) $ 3.59  
Weighted Average Remaining Life 5 years 3 months 5 years
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Additional Disclosures [Abstract]    
Outstanding, Aggregate Intrinsic Value $ 484,535 $ 1,415,150
Exercisable, Aggregate Intrinsic Value 201,957  
Vested and expected to vest, Aggregate Intrinsic Value $ 605,063  
Minimum    
Exercise Price Per Share [Abstract]    
Exercise Price Per Share, Granted (dollars per share) $ 3.22  
Exercise Price, Assumed in Merger (dollars per share) 3.15  
Exercise Price Per Share, Exercised (dollars per share) 0.79  
Exercise Price, Canceled and Forfeited (dollars per share) 2.60  
Maximum    
Exercise Price Per Share [Abstract]    
Exercise Price Per Share, Granted (dollars per share) 3.72  
Exercise Price, Assumed in Merger (dollars per share) 30.33  
Exercise Price Per Share, Exercised (dollars per share) 2.00  
Exercise Price, Canceled and Forfeited (dollars per share) $ 30.33