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	Mar. 31, 2019	Dec. 31, 2018
Liabilities:
Total liabilities	$ 6,149	$ 6,027
Level 2
Assets:
Total assets	318	766
Level 2 \| Interest rate swap instruments
Assets:
Total assets	285	733
Liabilities:
Liability derivatives	3,990	3,187
Level 2 \| Commodity swap instruments
Assets:
Total assets	33	33
Liabilities:
Liability derivatives	70	70
Level 2 \| Interest make-whole provisions
Liabilities:
Liability derivatives	1,085	1,808
Level 3
Liabilities:
Contingent revenue earn-out	$ 1,004	$ 962