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

Business Segment Information - Revenue (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Revenue from External Customer [Line Items]
Revenues	$ 173,768	$ 189,142	$ 152,489	$ 115,433	$ 181,061	$ 168,891	$ 142,558	$ 100,731	$ 630,832	$ 593,241	$ 574,171
Project
Revenue from External Customer [Line Items]
Revenues									434,380	388,327	388,142
Operating Assets
Revenue from External Customer [Line Items]
Revenues									55,130	52,168	42,265
Operations and Maintenance
Revenue from External Customer [Line Items]
Revenues									59,117	57,177	55,644
Integrated-PV
Revenue from External Customer [Line Items]
Revenues									40,070	52,508	48,869
Other services
Revenue from External Customer [Line Items]
Revenues									$ 42,135	$ 43,061	$ 39,251