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

Income Taxes - Additional Information (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Income Tax Disclosure [Abstract]
Income tax provision	$ 3,100	$ 939	$ 597	$ 2,000
Effective tax rate, percentage	14.90%	10.10%	1.80%	9.20%
Unrecognized tax benefits	$ 80		$ 80		$ 80

Amount of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.