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

Fair Value Measurement - Fair Value of Assets and Liabilities Measured on a Recurring Basis (Details) - Recurring - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Liabilities:
Total liabilities	$ 3,637	$ 3,529
Level 2
Assets:
Total assets	1,528	233
Level 2 \| Interest rate swap instruments
Assets:
Total assets	1,494	233
Liabilities:
Liability derivatives	1,548	3,529
Level 2 \| Commodity swap instruments
Assets:
Total assets	34	0
Liabilities:
Liability derivatives	46	0
Level 2 \| Interest make-whole provisions
Liabilities:
Liability derivatives	1,488	0
Level 3
Liabilities:
Contingent revenue earn-out	$ 555	$ 0