Annual report pursuant to Section 13 and 15(d)

Business Acquisitions and Related Transactions - Narrative (Details)

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Business Acquisitions and Related Transactions - Narrative (Details) (USD $)
 1 Months Ended 12 Months Ended 1 Months Ended 12 Months Ended 1 Months Ended 12 Months Ended 1 Months Ended 12 Months Ended 1 Months Ended 12 Months Ended 1 Months Ended 12 Months Ended
Apr. 30, 2011
Dec. 31, 2013
Dec. 31, 2012
Dec. 31, 2011
Jun. 30, 2013
ESP
Dec. 31, 2013
ESP
Dec. 31, 2013
Ennovate
Feb. 28, 2013
Ennovate
Jul. 31, 2012
FAME
Dec. 31, 2012
FAME
Apr. 30, 2011
Quantum
Aug. 31, 2010
Quantum
Jul. 31, 2011
AEG
Dec. 31, 2012
AEG
Aug. 31, 2011
Ameresco Southwest
Dec. 31, 2011
Ameresco Southwest
Dec. 31, 2011
AIS
Dec. 31, 2011
AIS
Dec. 31, 2013
Customer-Related Intangible Assets [Member]
Business Acquisition [Line Items]                                      
Number of businesses acquired         $ 2                            
Purchase price           8,764,506       4,486,950       11,993,236   50,057,113 4,497,141 4,497,141  
Initial cash payment                 4,486,950     6,150,000 11,993,236   50,057,113   4,497,141    
Additional payment 1,956,366 0 0 1,956,366             1,956,366                
Security deposit with third-party escrow agent         777,710     1,200,000 900,000       1,000,000       900,000 900,000  
Total fair value of consideration           8,764,506 1,765,556     4,486,950       11,993,236   50,057,113   4,497,141  
Maximum additional consideration for former stockholders of acquiree                         5,000,000            
Contingent consideration                         1,652,000            
Gain on contingent liability   (1,075,112) 0 0                   1,075,112          
Assets acquired                                     $ 5,099,496
Weighted average useful life                                     5 years 10 months 24 days