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

Derivative Instruments and Hedging Activities - Fair Value of Derivative Instruments on the Balance Sheet (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Derivatives Designated as Hedging Instruments: \| Interest rate swap contracts \| Other liabilities
Derivatives, Fair Value [Line Items]
Liability derivatives	$ 7,157	$ 9,994
Derivatives Not Designated as Hedging Instruments: \| Interest rate swap contracts \| Other assets
Derivatives, Fair Value [Line Items]
Asset derivatives	1,290	2
Derivatives Not Designated as Hedging Instruments: \| Interest rate swap contracts \| Other liabilities
Derivatives, Fair Value [Line Items]
Liability derivatives	45	79
Derivatives Not Designated as Hedging Instruments: \| Commodity swap contracts \| Other assets
Derivatives, Fair Value [Line Items]
Asset derivatives	115	363
Derivatives Not Designated as Hedging Instruments: \| Make-whole provisions \| Other liabilities
Derivatives, Fair Value [Line Items]
Liability derivatives	$ 1,112	$ 412