Ameresco, Inc. Annual report pursuant to Section 13 and 15(d)

Annual report pursuant to Section 13 and 15(d)

Debt and Financing Lease Liabilities - Senior Secured Credit Facility - Revolver and Term Loan (Details)

Debt and Financing Lease Liabilities - Senior Secured Credit Facility - Revolver and Term Loan (Details)					1 Months Ended						12 Months Ended
	Oct. 01, 2020 USD ($)	Sep. 30, 2020 USD ($)	Feb. 29, 2020	Jun. 28, 2019 USD ($) bank	Dec. 31, 2020 USD ($) project	Jul. 31, 2020 USD ($)	Jun. 30, 2020 USD ($)	May 31, 2020 USD ($) bank	Apr. 30, 2020 USD ($) project	Mar. 31, 2020 USD ($)	Dec. 31, 2020 USD ($) project	Dec. 31, 2019 USD ($) project	Mar. 31, 2021	Nov. 30, 2020 USD ($)	Oct. 31, 2020 USD ($)	Jun. 27, 2019 USD ($)
Line of Credit Facility [Line Items]
Total funded debt to EBITDA covenant ratio, maximum																3.00
Total funded debt to EBITDA ratio, minimum				3.25
Letters of credit outstanding					$ 11,916,000						$ 11,916,000
Line of credit					110,270,000						$ 110,270,000	$ 111,997,000
Solar PV project
Line of Credit Facility [Line Items]
Solar PV projects sold \| project											2	3
Fixed rate note payable in quarterly installments
Line of Credit Facility [Line Items]
Line of credit					$ 3,356,000						$ 3,356,000
December 2020 Long Term Finance Liability \| Solar PV project
Line of Credit Facility [Line Items]
Stated interest rate (percent)					0.00%						0.00%
Long-term financing facilities in quarterly installments
Line of Credit Facility [Line Items]
Line of credit					$ 2,544,000						$ 2,544,000
Agreement term											10 years
Long-term financing facilities in quarterly installments \| Solar PV project
Line of Credit Facility [Line Items]
Stated interest rate (percent)					0.00%						0.00%
Solar PV projects sold \| project					2
Revolving Credit Facility
Line of Credit Facility [Line Items]
Current borrowing capacity				$ 115,000,000
Commitment fee percentage				0.375%
Periodic principal payment				$ 1,219,000
Maximum amount of company's consolidated stockholders' equity eligible for investment in or loan to non-core subsidiaries				0.49
Minimum debt service coverage ratio				1.5
Revolving Credit Facility \| Maximum
Line of Credit Facility [Line Items]
Current borrowing capacity				$ 20,000,000
Additional borrowing capacity (up to)				100,000,000
Revolving Credit Facility \| Minimum
Line of Credit Facility [Line Items]
Additional borrowing capacity (up to)				$ 25,000,000
Revolving Credit Facility \| Base Rate \| Maximum
Line of Credit Facility [Line Items]
Basis spread on variable rate				0.25%
Revolving Credit Facility \| Base Rate \| Minimum
Line of Credit Facility [Line Items]
Basis spread on variable rate				0.50%
Revolving Credit Facility \| Federal Funds Effective Rate
Line of Credit Facility [Line Items]
Basis spread on variable rate				0.50%
Revolving Credit Facility \| London Interbank Offered Rate (LIBOR)
Line of Credit Facility [Line Items]
Basis spread on variable rate				1.50%
Revolving Credit Facility \| London Interbank Offered Rate (LIBOR) \| Maximum
Line of Credit Facility [Line Items]
Basis spread on variable rate				1.75%
Revolving Credit Facility \| London Interbank Offered Rate (LIBOR) \| Minimum
Line of Credit Facility [Line Items]
Basis spread on variable rate				2.00%
Term Loan \| Notes payable to banks
Line of Credit Facility [Line Items]
Original principal amount				$ 65,000,000
Line of Credit \| Revolving Credit Facility
Line of Credit Facility [Line Items]
Line of credit facility, number of banks \| bank				3
Long-term debt value, carrying value				$ 185,000,000						$ 185,000,000
Maximum borrowing capacity																$ 85,000,000
Total funded debt to EBITDA covenant ratio, maximum										3.75
Remaining borrowing capacity					$ 50,011,000						$ 50,011,000
Stated interest rate (percent)					3.75%						3.75%
Line of credit					$ 52,696,000						$ 52,696,000	$ 49,588,000
Line of Credit \| Revolving Credit Facility \| Forecast
Line of Credit Facility [Line Items]
Total funded debt to EBITDA covenant ratio, maximum													3.25
Line of Credit \| Revolving Credit Facility \| Eurocurrency Rate
Line of Credit Facility [Line Items]
Basis spread on variable rate			0.00%							1.00%
Line of Credit \| Revolving Credit Facility \| Revolving Credit Agreement
Line of Credit Facility [Line Items]
Maximum borrowing capacity								$ 41,850,000
Debt instrument, number of banks \| bank								2
Increase in interest rate								0.125%
Period increase for increase in interest rate								3 years
Line of credit					39,066,000						39,066,000
Line of Credit \| Revolving Credit Facility \| Revolving Credit Agreement \| London Interbank Offered Rate (LIBOR)
Line of Credit Facility [Line Items]
Basis spread on variable rate								2.25%
Line of Credit \| Revolving Credit Facility \| Construction revolver
Line of Credit Facility [Line Items]
Maximum borrowing capacity							$ 100,000,000
Long-term debt, gross					15,177,000						15,177,000	0
Remaining borrowing capacity					84,823,000						84,823,000
Line of credit					14,976,000						14,976,000
Line of Credit \| Revolving Credit Facility \| Construction revolver \| Base Rate
Line of Credit Facility [Line Items]
Basis spread on variable rate							0.50%
Line of Credit \| Revolving Credit Facility \| Construction revolver \| London Interbank Offered Rate (LIBOR)
Line of Credit Facility [Line Items]
Basis spread on variable rate							2.00%
Line of Credit \| Revolving Credit Facility \| Construction revolver
Line of Credit Facility [Line Items]
Maximum borrowing capacity						$ 30,000,000
Long-term debt, gross					11,581,000						11,581,000	0
Remaining borrowing capacity					18,419,000						18,419,000
Line of credit					11,107,000						11,107,000
Borrowing capacity increase limit						$ 20,000,000
Line of Credit \| Revolving Credit Facility \| Construction revolver \| London Interbank Offered Rate (LIBOR)
Line of Credit Facility [Line Items]
Basis spread on variable rate						1.75%
Line of Credit \| Revolving Credit Facility \| October 2020 Term Loan Modification
Line of Credit Facility [Line Items]
Maximum borrowing capacity	$ 35,000,000	$ 28,500,000													$ 50,000,000
Line of credit					33,642,000						33,642,000
Lender's option to increase limit, amount															$ 15,000,000
Debt instrument, fee amount					300,000						300,000
Unamortized discount					$ 788,000						$ 788,000
Line of Credit \| Revolving Credit Facility \| October 2020 Term Loan Modification \| London Interbank Offered Rate (LIBOR)
Line of Credit Facility [Line Items]
Basis spread on variable rate	6.00%	7.50%
Term Loan
Line of Credit Facility [Line Items]
Long-term debt, gross																$ 40,000,000
Stated interest rate (percent)					3.00%						3.00%
Line of credit					$ 57,574,000						$ 57,574,000	62,409,000
Term Loan \| Long-term financing facilities in quarterly installments
Line of Credit Facility [Line Items]
Long-term debt, gross					2,924,000						2,924,000	0
Loans Payable \| Fixed rate note
Line of Credit Facility [Line Items]
Long-term debt, gross					$ 222,000						$ 222,000	0
Original principal amount									$ 222,000
Stated interest rate (percent)					5.00%				5.00%		5.00%
Loans Payable \| Fixed rate note \| Energy Project
Line of Credit Facility [Line Items]
Number of projects acquired \| project									1
Loans Payable \| Fixed rate note payable in quarterly installments
Line of Credit Facility [Line Items]
Long-term debt, gross					$ 3,548,000						$ 3,548,000	$ 0
Original principal amount														$ 3,484,000
Stated interest rate (percent)					3.575%						3.575%