Quarterly report pursuant to Section 13 or 15(d)

Cover Page

v3.21.2
Cover Page - shares
 9 Months Ended
Sep. 30, 2021
Oct. 29, 2021
Entity Information [Line Items]    
Document Type 10-Q  
Document Quarterly Report true  
Document Period End Date Sep. 30, 2021  
Document Transition Report false  
Entity File Number 001-34811  
Entity Registrant Name Ameresco, Inc.  
Entity Incorporation, State or Country Code DE  
Entity Tax Identification Number 04-3512838  
Entity Address, Address Line One 111 Speen Street  
Entity Address, Address Line Two Suite 410  
Entity Address, City or Town Framingham  
Entity Address, State or Province MA  
Entity Address, Postal Zip Code 01701  
City Area Code 508  
Local Phone Number 661-2200  
Entity Current Reporting Status Yes  
Entity Interactive Data Current Yes  
Entity Filer Category Accelerated Filer  
Entity Small Business false  
Entity Emerging Growth Company false  
Entity Shell Company false  
Entity Central Index Key 0001488139  
Current Fiscal Year End Date --12-31  
Document Fiscal Year Focus 2021  
Document Fiscal Period Focus Q3  
Amendment Flag false  
Class A Common Stock    
Entity Information [Line Items]    
Security Exchange Name NYSE  
Title of 12(b) Security Class A Common Stock, $0.0001 par value per share  
Trading Symbol AMRC  
Entity Common Stock, Shares Outstanding (in shares)   33,559,460
Class B Common Stock    
Entity Information [Line Items]    
Security Exchange Name NYSE  
Title of 12(b) Security Class B Common Stock, $0.0001 par value per share  
Entity Common Stock, Shares Outstanding (in shares)   18,000,000
No Trading Symbol Flag true