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

Income Taxes - Additional Information (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020
Income Tax Disclosure [Abstract]
Income tax provision (benefit)	$ 2,205	$ (2,503)
Effective tax rate, percentage	15.10%	(60.60%)
Unrecognized tax benefits	$ 190		$ 190

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