Quarterly report pursuant to Section 13 or 15(d)

Summary of Significant Accounting Policies - Goodwill and Intangible Assets (Details)

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Summary of Significant Accounting Policies - Goodwill and Intangible Assets (Details) (USD $)
Jul. 31, 2011
AEG [Member]
Aug. 31, 2011
Ameresco Southwest [Member]
Dec. 31, 2011
AIS [Member]
Goodwill [Line Items]      
Goodwill recorded for acquisitions $ 8,728,169 $ 16,545,434 $ 1,549,467