Ameresco, Inc. Quarterly report pursuant to Section 13 or 15(d)

Geographic Information (Details) (USD $)	3 Months Ended		9 Months Ended
Geographic Information (Details) (USD $)	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Dec. 31, 2012
Revenues from External Customers and Long-Lived Assets [Line Items]
Long-lived assets:	$ 236,462,648		$ 236,462,648		$ 216,662,200
Revenue:	161,648,813	163,906,205	398,037,030	474,579,479
United States [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Long-lived assets:	218,445,196		218,445,196		198,485,075
Revenue:	139,999,757	146,197,073	345,311,411	424,454,798
Canada [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Long-lived assets:	17,927,670		17,927,670		18,143,844
Revenue:	20,059,253	16,141,540	49,844,725	44,433,346
Other [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Long-lived assets:	89,782		89,782		33,281
Revenue:	$ 1,589,803	$ 1,567,592	$ 2,880,894	$ 5,691,335