Ameresco, Inc. Annual report pursuant to Section 13 and 15(d)

Geographic Information (Details) (USD $)	3 Months Ended								12 Months Ended
Geographic Information (Details) (USD $)	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Revenues from External Customers and Long-Lived Assets [Line Items]
Assets	$ 219,443,224				$ 216,662,200				$ 219,443,224	$ 216,662,200
Revenues	176,134,000	161,649,000	126,253,000	110,136,000	156,591,000	163,906,000	164,100,000	146,573,000	574,171,249	631,170,565	728,200,318
United States
Revenues from External Customers and Long-Lived Assets [Line Items]
Assets	201,025,592				198,485,075				201,025,592	198,485,075
Revenues									501,557,629	563,746,226	615,583,995
CANADA
Revenues from External Customers and Long-Lived Assets [Line Items]
Assets	18,324,383				18,143,844				18,324,383	18,143,844
Revenues									68,797,187	60,589,842	110,594,062
Other Countries [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Assets	93,249				33,281				93,249	33,281
Revenues									$ 3,816,433	$ 6,834,497	$ 2,022,261