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Stockholders Equity (Details) (USD $)
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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 | |||||||||||||||||
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Jul. 31, 2010
Classes
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Dec. 31, 2010
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Dec. 31, 2012
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Dec. 31, 2011
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Dec. 31, 2009
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Dec. 31, 2012
Warrant
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Jun. 30, 2010
Warrant
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Dec. 31, 2002
Warrant
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Dec. 31, 2001
Warrant
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Dec. 31, 2000
Series A Preferred Stock
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Dec. 31, 2002
Series A Preferred Stock
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Dec. 31, 2009
Series A Preferred Stock
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Jul. 31, 2010
Common Stock
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Jun. 30, 2010
Common Stock
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Dec. 31, 2010
Common Stock
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Dec. 31, 2002
Common Stock
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Dec. 31, 2001
Common Stock
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Dec. 31, 2002
Common Stock
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Aug. 25, 2010
Class A Common Stock
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Jul. 27, 2010
Class A Common Stock
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Dec. 31, 2012
Class A Common Stock
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Dec. 31, 2011
Class A Common Stock
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Jul. 27, 2010
Class A Common Stock
Ameresco, Inc.
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Jul. 27, 2010
Class A Common Stock
Existing Shareholders
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Jul. 31, 2010
Class B Common Stock
Vote
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Dec. 31, 2012
Class B Common Stock
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Dec. 31, 2011
Class B Common Stock
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Dec. 31, 2012
Preferred Stock
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| 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 | |||||||||||||||||||||||||||