Quarterly report pursuant to Section 13 or 15(d)

Business Acquisitions and Related Transactions (Details)

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Business Acquisitions and Related Transactions (Details) (USD $)
1 Months Ended
Apr. 30, 2011
Quantum [Member]
Aug. 31, 2010
Quantum [Member]
Jun. 30, 2012
Quantum [Member]
Jun. 30, 2012
AEG [Member]
Jul. 31, 2011
AEG [Member]
Aug. 31, 2011
Ameresco Southwest [Member]
Dec. 31, 2011
AIS [Member]
Business Acquisition [Line Items]              
Initial cash payment   $ 6,150,000          
Additional payment 1,956,366            
Cash paid         11,993,236 50,057,113 4,497,141
Security deposit with third-party escrow agent         1,000,000   900,000
Maximum additional consideration for former stockholders of acquiree     1,150,000 5,000,000 5,000,000    
Fair value of additional consideration for former stockholders of acquiree         $ 1,652,000