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

Derivative Instruments and Hedging Activities - Effects on Statements of Income (Loss) and Consolidated Statements of Comprehensive Loss (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Loss (Gain) Recognized in Net Income	$ 667	$ 454	$ 1,892	$ 971
Derivatives Designated as Hedging Instruments \| Other expenses, net \| Interest rate swap contracts
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Loss (Gain) Recognized in Net Income	528	503	1,573	908
Derivatives Not Designated as Hedging Instruments \| Other expenses, net \| Interest rate swap contracts
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Loss (Gain) Recognized in Net Income	(63)	287	(842)	287
Derivatives Not Designated as Hedging Instruments \| Other expenses, net \| Commodity swap contracts
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Loss (Gain) Recognized in Net Income	2,409	194	3,907	241
Derivatives Not Designated as Hedging Instruments \| Other expenses, net \| Make-whole provisions
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Loss (Gain) Recognized in Net Income	$ (1,679)	$ (27)	$ (1,173)	$ 443