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	Jun. 30, 2018	Dec. 31, 2017
Derivatives Designated as Hedging Instruments \| Interest rate swap instruments \| Other assets
Derivatives, Fair Value [Line Items]
Asset derivatives	$ 1,251	$ 233
Derivatives Designated as Hedging Instruments \| Interest rate swap instruments \| Other liabilities
Derivatives, Fair Value [Line Items]
Liability derivatives	2,162	3,529
Not Designated as Hedging Instrument \| Interest rate swap instruments \| Other assets
Derivatives, Fair Value [Line Items]
Asset derivatives	47	0
Not Designated as Hedging Instrument \| Interest rate swap instruments \| Other liabilities
Derivatives, Fair Value [Line Items]
Liability derivatives	252	0
Not Designated as Hedging Instrument \| Commodity swap contracts \| Other assets
Derivatives, Fair Value [Line Items]
Asset derivatives	21	0
Not Designated as Hedging Instrument \| Commodity swap contracts \| Other liabilities
Derivatives, Fair Value [Line Items]
Liability derivatives	$ 66	$ 0