Quarterly report pursuant to Section 13 or 15(d)

Document and Entity Information

v3.10.0.1
Document and Entity Information - shares
9 Months Ended
Sep. 30, 2018
Oct. 29, 2018
Entity Information [Line Items]    
Entity Registrant Name Ameresco, Inc.  
Entity Central Index Key 0001488139  
Current Fiscal Year End Date --12-31  
Entity Filer Category Accelerated Filer  
Entity Small Business false  
Entity Emerging Growth Company false  
Document Type 10-Q  
Document Period End Date Sep. 30, 2018  
Document Fiscal Year Focus 2018  
Document Fiscal Period Focus Q3  
Amendment Flag false  
Common Class A    
Entity Information [Line Items]    
Entity Common Stock, Shares Outstanding (in shares)   27,976,565
Common Class B    
Entity Information [Line Items]    
Entity Common Stock, Shares Outstanding (in shares)   18,000,000