Annual report pursuant to Section 13 and 15(d)

Document and Entity Information

v3.19.3.a.u2
Document and Entity Information - USD ($)
 12 Months Ended
Dec. 31, 2019
Mar. 02, 2020
Jun. 28, 2019
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    
Document Type 10-K    
Document Period End Date Dec. 31, 2019    
Document Fiscal Year Focus 2019    
Document Fiscal Period Focus FY    
Amendment Flag false    
Entity Well-known Seasoned Issuer No    
Entity Voluntary Filers No    
Entity Current Reporting Status Yes    
Entity Public Float     $ 322,112,989
Entity Shell Company false    
Entity Small Business false    
Entity Emerging Growth false    
Class A Common Stock      
Entity Information [Line Items]      
Common Stock, Shares Outstanding (in shares)   29,380,395  
Class B Common Stock      
Entity Information [Line Items]      
Common Stock, Shares Outstanding (in shares)   18,000,000