Annual report pursuant to Section 13 and 15(d)

Stockholders Equity (Details)

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Stockholders Equity (Details) (USD $)
1 Months Ended 12 Months Ended 29 Months Ended 9 Months Ended 24 Months Ended 1 Months Ended 12 Months Ended 24 Months Ended 0 Months Ended 0 Months Ended 1 Months Ended
Jul. 31, 2010
Classes
Dec. 31, 2010
Dec. 31, 2012
Dec. 31, 2011
Dec. 31, 2009
Dec. 31, 2012
Warrant
Jun. 30, 2010
Warrant
Dec. 31, 2002
Warrant
Dec. 31, 2001
Warrant
Dec. 31, 2000
Series A Preferred Stock
Dec. 31, 2002
Series A Preferred Stock
Dec. 31, 2009
Series A Preferred Stock
Jul. 31, 2010
Common Stock
Jun. 30, 2010
Common Stock
Dec. 31, 2010
Common Stock
Dec. 31, 2002
Common Stock
Dec. 31, 2001
Common Stock
Dec. 31, 2002
Common Stock
Aug. 25, 2010
Class A Common Stock
Jul. 27, 2010
Class A Common Stock
Dec. 31, 2012
Class A Common Stock
Dec. 31, 2011
Class A Common Stock
Jul. 27, 2010
Class A Common Stock
Ameresco, Inc.
Jul. 27, 2010
Class A Common Stock
Existing Shareholders
Jul. 31, 2010
Class B Common Stock
Vote
Dec. 31, 2012
Class B Common Stock
Dec. 31, 2011
Class B Common Stock
Dec. 31, 2012
Preferred Stock
Class of Stock [Line Items]                                                        
Common stock, shares issued (in shares)         60,000,000                               32,019,982 30,713,837       18,000,000 18,000,000  
Common stock, par value (in dollars per share)   $ 0.0001     $ 0.0001                               $ 0.0001 $ 0.0001       $ 0.0001 $ 0.0001  
Stock issued during period                   3,220,000       405,286         342,889 8,696,820     6,000,000 2,696,820        
Share price (in dollars pers share)                   $ 1.00                                    
Preferred stock, shares authorized (in shares)     5,000,000 5,000,000               3,500,000                               5,000,000
Preferred stock, par value (in dollars per share)     $ 0.0001 $ 0.0001               $ 0.0001                               $ 0.0001
Shares converted (in shares)                     10,000             30,000                    
Common stock repurchased and held in treasury, shares                             117,400                          
Common stock repurchased and held in treasury, cost per share                             $ 6.55                          
Common stock repurchased and held in treasury, value                             768,970                          
Warrants issued                               1,600,000 2,000,000                      
Exercise price of warrants (in dollars per share)           0.005 0.005 0.30 0.005                                      
Number of classes of common stock 2                                                      
Split conversion ratio 2                       2                              
Vote ratio                                                 5      
Price per share (in dollars per share)                                     $ 10.00 $ 10.00                
Common stock, shares authorized (in shares)                                         500,000,000 500,000,000       144,000,000 144,000,000  
Initial public offering proceeds, net   53,232,458 63,400,000                                                  
Proceeds from initial public offering, net     56,400,000                                                  
Increase in capital account, gross     27,000,000                                                  
Increase in capital account, net     25,100,000                                                  
Costs incurred In initial public offering     $ 7,000,000